Magnetic resonance and confocal imaging of solute penetration into the lens reveals a zone of restricted extracellular space diffusion.

PubMed

Vaghefi, Ehsan; Walker, Kerry; Pontre, Beau P; Jacobs, Marc D; Donaldson, Paul J

2012-06-01

It has been proposed that in the absence of blood supply, the ocular lens operates an internal microcirculation system that delivers nutrients to internalized fiber cells faster and more efficiently than would occur by passive diffusion alone. To visualize the extracellular space solute fluxes potentially generated by this system, bovine lenses were organ cultured in artificial aqueous humor (AAH) for 4 h in the presence or absence of two gadolinium-based contrast agents, ionic Gd(3+), or a chelated form of Gd(3+), Gd-diethylenetriamine penta-acetic acid (Gd-DTPA; mol mass = 590 Da). Contrast reagent penetration into the lens core was monitored in real time using inversion recovery-spin echo (IR-SE) magnetic resonance imaging (MRI), while steady-state accumulation of [Gd-DTPA](-2) was also determined by calculating T1 values. After incubation, lenses were fixed and cryosectioned, and sections were labeled with the membrane marker wheat germ agglutinin (WGA). Sections were imaged by confocal microscopy using standard and reflectance imaging modalities to visualize the fluorescent WGA label and gadolinium reagents, respectively. Real-time IR-SE MRI showed rapid penetration of Gd(3+) into the outer cortex of the lens and a subsequent bloom of signal in the core. These two areas of signal were separated by an area in the inner cortex that limited entry of Gd(3+). Similar results were obtained for Gd-DTPA, but the penetration of the larger negatively charged molecule into the core could only be detected by calculating T1 values. The presence of Gd-DTPA in the extracellular space of the outer cortex and core, but its apparent absence from the inner cortex was confirmed using reflectance imaging of equatorial sections. In axial sections, Gd-DTPA was associated with the sutures, suggesting these structures provide a pathway from the surface, across the inner cortex barrier to the lens core. Our studies have revealed inner and outer boundaries of a zone within which a narrowing of the extracellular space restricts solute diffusion and acts to direct fluxes into the lens core via the sutures.

Visualization of Fluoride Ions In Vivo Using a Gadolinium(III)-Coumarin Complex-Based Fluorescence/MRI Dual-Modal Probe

PubMed Central

Wang, Yue; Song, Renfeng; Feng, Huan; Guo, Ke; Meng, Qingtao; Chi, Haijun; Zhang, Run; Zhang, Zhiqiang

2016-01-01

A new Gadolinium(III)–coumarin complex, DO3A-Gd-CA, was designed and prepared as a dual-modal probe for simultaneous fluorescence and relaxivity responses to fluoride ions (F−) in aqueous media and mice. DO3A-Gd-CA was designed by using Gd(III) center as an MRI signal output unit and fluoride binding site, and the 4-(diethylamino)-coumarin-3-carboxylic acid (CA) as a fluorescence reporter. Upon the addition of fluoride ions to the solution of DO3A-Gd-CA, the liberation of the coordinated CA ligand led to a 5.7-fold fluorescence enhancement and a 75% increase in the longitudinal relaxivity (r1). The fluorescent detection limit for fluoride ions was determined to be 8 μM based on a 3σ/slope. The desirable features of the proposed DO3A-Gd-CA, such as high sensitivity and specificity, reliability at physiological pH and low cytotoxicity enable its application in visualization of fluoride ion in mice. The successful in vivo imaging indicates that DO3A-Gd-CA could be potentially used in biomedical diagnosis fields. PMID:27999298

Visualization of Fluoride Ions In Vivo Using a Gadolinium(III)-Coumarin Complex-Based Fluorescence/MRI Dual-Modal Probe.

PubMed

Wang, Yue; Song, Renfeng; Feng, Huan; Guo, Ke; Meng, Qingtao; Chi, Haijun; Zhang, Run; Zhang, Zhiqiang

2016-12-16

A new Gadolinium(III)-coumarin complex, DO3A-Gd- CA , was designed and prepared as a dual-modal probe for simultaneous fluorescence and relaxivity responses to fluoride ions (F - ) in aqueous media and mice. DO3A-Gd- CA was designed by using Gd(III) center as an MRI signal output unit and fluoride binding site, and the 4-(diethylamino)-coumarin-3-carboxylic acid ( CA ) as a fluorescence reporter. Upon the addition of fluoride ions to the solution of DO3A-Gd- CA , the liberation of the coordinated CA ligand led to a 5.7-fold fluorescence enhancement and a 75% increase in the longitudinal relaxivity ( r ₁). The fluorescent detection limit for fluoride ions was determined to be 8 μM based on a 3 σ / slope . The desirable features of the proposed DO3A-Gd- CA , such as high sensitivity and specificity, reliability at physiological pH and low cytotoxicity enable its application in visualization of fluoride ion in mice. The successful in vivo imaging indicates that DO3A-Gd- CA could be potentially used in biomedical diagnosis fields.

Hydrogen sulfide regulates intracellular Ca2+ concentration in endothelial cells from excised rat aorta.

PubMed

Moccia, Francesco; Bertoni, Giuseppe; Pla, Alessandra Florio; Dragoni, Silvia; Pupo, Emanuela; Merlino, Annalisa; Mancardi, Daniele; Munaron, Luca; Tanzi, Franco

2011-09-01

Hydrogen sulphide (H2S) is a recently discovered gasotransmitter that may regulate a growing number of endothelial functions, including nitric oxide (NO) release, proliferation, adhesion and migration, which are the key steps of angiogenesis. The mechanism whereby H2S impacts on endothelial physiology is still unclear: however, the aforementioned processes are driven by an increase in intracellular Ca2+ concentration ([Ca2+]i). In the present study, we exploited the excised rat aorta to gain insights into the regulation of [Ca2+]i by H2S within in situ endothelial cells (ECs). Sodium hydrosulphide (NaHS), a H2S donor, caused an elevation in [Ca2+]i, which disappeared in absence of extracellular Ca2+. NaHSinduced Ca2+ inflow was sensitive to high doses of Gd3+, but not BTP-2. Inhibition of the reverse-mode of the Na+-Ca2+ exchanger (NCX), with KB-R7943 or upon removal of extracellular Na+, abrogated the Ca2+ response to NaHS. Moreover, NaHS-elicited Ca2+ entry was significantly reduced by TEA and glybenclamide, which hinted at the involvement of ATP-dependent K+ (KATP) channels. Conversely, NaHS-evoked Ca2+ signal was not affected by the reducing agent, dithiothreitol. Acute addition of NaHS hindered both Ca2+ release and Ca2+ entry induced by ATP, a physiological agonist of ECs. Consistently, inhibition of endogenous H2S synthesis with DL-propargylglycine impaired ATP-induced Ca2+ inflow, whereas it did not affect Ca2+ mobilization. These data provide the first evidence that H2S may stimulate Ca2+ influx into ECs by recruiting the reverse-mode of NCX and KATP channels. In addition, they show that such gasotransmitter may modulate the Ca2+ signals elicited by physiological stimuli in intact endothelium.

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.

Mechanisms of leukotriene D4-induced constriction in human small bronchioles

PubMed Central

Snetkov, V A; Hapgood, K J; McVicker, C G; Lee, T H; Ward, J P T

2001-01-01

We examined the mechanisms underlying leukotriene D4- (LTD4) induced constriction of human small (300 – 500 μm i.d.) bronchioles, and the effect of LTD4 on ion currents and Ca2+ transients in smooth muscle cells (SMC) isolated from these bronchioles. LTD4 caused a concentration-dependent bronchoconstriction with an EC50=0.58±0.05 nM (n=7) which was not easily reversible upon washout. This bronchoconstriction was entirely dependent on extracellular Ca2+. Blockade of L-type Ca2+ channels with nifedipine (10 μM) reduced LTD4 response by 39±2% (n=8), whilst La3+, Gd3+ and SK&F 96,365 abolished LTD4-induced bronchoconstriction completely and reversibly, suggesting the majority of Ca2+ entry was via non-selective cation channels. Antagonists of PI-PLC (U73,122 and ET-18-OCH3), PLD (propranolol) and PKC (cheleretrine and Ro31-8220) were without any effect on LTD4-induced bronchoconstriction, whilst the PC-PLC inhibitor D609 caused complete relaxation. Inhibition of protein tyrosine kinase with tyrphostin A23 (100 μM) caused about 50% relaxation, although the inactive analogue tyrphostin A1 was without effect. In freshly isolated SMC from human small bronchioles LTD4 caused a slow increase of intracellular Ca2+ concentration, with a consequent rise of the activity of large conductance Ca2+-dependent K+ channels and the amplitude of depolarization-induced outward whole-cell current. Again, no effect of LTD4 could be observed in the absence of extracellular Ca2+. We conclude that LTD4 causes constriction of these small bronchioles primarily by activating Ca2+ entry via non-voltage gated channels, possibly by a PC-PLC mediated pathway. PMID:11350860

Contrast enhanced liver MRI in patients with primary sclerosing cholangitis: inverse appearance of focal confluent fibrosis on delayed phase MR images with hepatocyte specific versus extracellular gadolinium based contrast agents.

PubMed

Husarik, Daniela B; Gupta, Rajan T; Ringe, Kristina I; Boll, Daniel T; Merkle, Elmar M

2011-12-01

To assess the enhancement pattern of focal confluent fibrosis (FCF) on contrast-enhanced hepatic magnetic resonance imaging (MRI) using hepatocyte-specific (Gd-EOB-DTPA) and extracellular (ECA) gadolinium-based contrast agents in patients with primary sclerosing cholangitis (PSC). After institutional review board approval, 10 patients with PSC (6 male, 4 female; 33-61 years) with 13 FCF were included in this retrospective study. All patients had a Gd-EOB-DTPA-enhanced liver MRI exam, and a comparison ECA-enhanced MRI. On each T1-weighted dynamic dataset, the signal intensity (SI) of FCF and the surrounding liver as well as the paraspinal muscle (M) were measured. In the Gd-EOB-DTPA group, hepatocyte phase images were also included. SI FCF/SI M, SI liver/SI M, and [(SI liver - SI FCF)/SI liver] were compared between the different contrast agents for each dynamic phase using the paired Student's t-test. There was no significant difference in SI FCF/SI M in all imaging phases. SI liver/SI M was significantly higher for the Gd-EOB-DTPA group in the delayed phase (P < .001), whereas there was no significant difference in all other imaging phases. In the Gd-EOB-DTPA group, mean [(SI liver - SI FCF)/SI liver] were as follows (values for ECA group in parentheses): unenhanced phase: 0.26 (0.26); arterial phase: 0.01 (-0.31); portal venous phase (PVP): -0.05 (-0.26); delayed phase (DP): 0.14 (-0.54); and hepatocyte phase: 0.26. Differences were significant for the DP (P < .001). On delayed phase MR images the FCF-to-liver contrast is reversed with the lesions appearing hyperintense on ECA enhanced images and hypointense on Gd-EOB-DTPA-enhanced images. Copyright © 2011 AUR. Published by Elsevier Inc. All rights reserved.

Thermal, spectroscopic properties and laser performance at 1.06 and 1.33 μm of Nd : Ca 4YO(BO 3) 3 and Nd : Ca 4GdO(BO 3) 3 crystals

NASA Astrophysics Data System (ADS)

Wang, Changqing; Zhang, Huaijin; Meng, Xianlin; Zhu, Li; Chow, Y. T.; Liu, Xuesong; Cheng, Ruiping; Yang, Zhaohe; Zhang, Shaojun; Sun, Lianke

2000-11-01

Nd : Ca 4YO(BO 3) 3 (Nd : YCOB) and Nd : Ca 4GdO(BO 3) 3 (Nd : GdCOB) crystals were grown by Czochralski method. Thermal expansion and specific heat of these two crystals were experimentally determined. Their fluorescence spectra were measured within the range from 1000 to 1500 nm. Laser output experiments at 1.06 and 1.33 μm of Nd : YCOB and Nd : GdCOB crystals were performed with a cw Ti : sapphire laser as the pump source.

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.

Effect of CMAS composition on hot corrosion behavior of gadolinium zirconate thermal barrier coating materials

DOE PAGES

Deng, Wenzhuo; Fergus, Jeffrey W.

2017-07-06

The resistance of synthesized pyrochlore-type Gd 2Zr 2O 7 bulk specimens to four calcium-magnesium aluminosilicate (CMAS) compositions at different temperatures was investigated. The reaction products were identified by x-ray diffraction and penetration depths were examined using scanning electron microscopy. A dense reaction layer is comprised mainly of Ca 2Gd 8(SiO 4) 6O 2 and a cubic fluorite phase formed during the CMAS attack, and some unreacted CMAS was found in a transition layer below the reaction layer. The overall infiltration depth changed slightly with temperature, however, the thickness of the reaction layer and the morphology of the transition layer variedmore » distinctly with temperature. The sintered sample underwent the most severe degradation by the CaO-lean CMAS, whereas the effect of CaSO 4 and CaCO 3 was not significant. Furthermore, the Gd content of the ZrO 2-based cubic fluorite phase depends on the temperature and the molar ratio of Ca:Si in the CMAS.« less

Effects of in utero exposure to Tityus bahiensis scorpion venom in adult rats.

PubMed

Dorce, Ana Leticia Coronado; Dorce, Valquiria Abrão Coronado; Nencioni, Ana Leonor Abrahão

2010-01-01

The toxicity of Tityus bahiensis scorpion venom is well known, but there are little data about the damage in offspring of dams that were exposed to the venom during pregnancy. The objective of this work was to determine the toxic effects of venom in adult offspring of Wistar rats exposed to venom in utero. Dams were divided into a control group, subcutaneously injected with saline solution on the 10th (GD10) and 16th (GD16) days, and two experimental groups, subcutaneously injected with venom (2.5mg/kg) on GD10 or GD16, respectively. Adult offspring were evaluated according to behavioral development and neuronal integrity in the hippocampus. Tests performed in the activity box and in the enriched environment demonstrated that males from GD10 had motor decrease. Females from GD10 showed a depressive-like state and were more anxious, as demonstrated by the forced swimming test and social interaction. The plus-maze discriminative avoidance task demonstrated that GD16 males had lower levels of anxiety. The number of neuronal cells was decreased in CA1, CA3 and CA4 hippocampal areas of males and females from GD10 group and in CA1 of females and CA4 of males from GD16 group. Thus, we conclude that venom exposure in pregnant dams causes subtle alteration in the behavioral and neuronal development of offspring in adult life in a gender-dependent manner. Copyright (c) 2009 Elsevier Inc. All rights reserved.

Assessment of Myocardial Remodeling Using an Elastin/Tropoelastin Specific Agent with High Field Magnetic Resonance Imaging (MRI).

PubMed

Protti, Andrea; Lavin, Begoña; Dong, Xuebin; Lorrio, Silvia; Robinson, Simon; Onthank, David; Shah, Ajay M; Botnar, Rene M

2015-08-13

Well-defined inflammation, proliferation, and maturation phases orchestrate the remodeling of the injured myocardium after myocardial infarction (MI) by controlling the formation of new extracellular matrix. The extracellular matrix consists mainly of collagen but also fractions of elastin. It is thought that elastin is responsible for maintaining elastic properties of the myocardium, thus reducing the risk of premature rupture. An elastin/tropoelastin-specific contrast agent (Gd-ESMA) was used to image tropoelastin and mature elastin fibers for in vivo assessment of extracellular matrix remodeling post-MI. Gd-ESMA enhancement was studied in a mouse model of myocardial infarction using a 7 T MRI scanner and results were compared to those achieved after injection of a nonspecific control contrast agent, gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA). In the infarcted tissue, Gd-ESMA uptake (measured as R1 relaxation rate) steadily increased from day 3 to day 21 as a result of the synthesis of elastin/tropoelastin. R1 values were in good agreement with histological findings. A similar R1 behavior was observed in the remote myocardium. No mature cross-linked elastin was found at any time point. In contrast, Gd-DTPA uptake was only observed in the infarct with no changes in R1 values between 3 and 21 days post-MI. We demonstrate the feasibility of in vivo imaging of extracellular matrix remodeling post-MI using a tropoelastin/elastin binding MR contrast agent, Gd-ESMA. We found that tropoelastin is the main contributor to the increased MRI signal at late stages of MI where its augmentation in areas of infarction was in good agreement with the R1 increase. © 2015 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

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.

Mechanical properties and corrosion behavior of Mg-Gd-Ca-Zr alloys for medical applications.

PubMed

Shi, Ling-Ling; Huang, Yuanding; Yang, Lei; Feyerabend, Frank; Mendis, Chamini; Willumeit, Regine; Ulrich Kainer, Karl; Hort, Norbert

2015-07-01

Magnesium alloys are promising candidates for biomedical applications. In this work, influences of composition and heat treatment on the microstructure, the mechanical properties and the corrosion behavior of Mg-Gd-Ca-Zr alloys as potential biomedical implant candidates were investigated. Mg5Gd phase was observed at the grain boundaries of Mg-10Gd-xCa-0.5Zr (x=0, 0.3, 1.2wt%) alloys. Increase in the Ca content led to the formation of additional Mg2Ca phase. The Ca additions increased both the compressive and the tensile yield strengths, but reduced the ductility and the corrosion resistance in cell culture medium. After solution heat treatment, the Mg5Gd particles dissolved in the Mg matrix. The compressive strength decreased, while the corrosion resistance improved in the solution treated alloys. After ageing at 200°C, metastable β' phase formed on prismatic planes and a new type of basal precipitates have been observed, which improved the compressive and tensile ultimate strength, but decreased the ductility. Copyright © 2015 Elsevier Ltd. All rights reserved.

Microstructure, mechanical properties and stretch formability of Mg-3Al-0.5Ca-0.2Gd alloy processed at various finish rolling temperatures

NASA Astrophysics Data System (ADS)

Kang, Qiang; Jiang, Haitao; Zhang, Yun

2018-04-01

Effects of various finish rolling temperatures on the microstructure, texture, mechanical properties and stretch formability of rolled and annealed Mg-3Al-0.5Ca-0.2Gd (wt%) alloy were investigated in this paper, and it was found that compared with grain size and second phase particles, the basal textures, tensile properties and stretch formability Mg-3Al-0.5Ca-0.2Gd alloy are more sensitive to the increasing finishing rolling temperature. For the rolled and annealed Mg-3Al-0.5Ca-0.2Gd alloy, their grains barely grow up and second phase particles are slightly coarsened, while their basal poles are obviously weakened and tilted with increasing finish rolling temperature. Consequently, the weakened and RD-tilted basal textures are beneficial to the gradually improved elongation and stretch formability of Mg-3Al-0.5Ca-0.2Gd alloy. It is investigated that the gradually activated non-basal slips, e. g. 〈c 〉, 〈c + a〉 dislocations due to the increasing finish rolling temperature could contribute to the weakened RD-tilted textures in rolled and annealed Mg-3Al-0.5Ca-0.2Gd alloy.

Determination of the optimum phase-matching directions for the self-frequency conversion of Nd:GdCOB and Nd:YCOB crystals

NASA Astrophysics Data System (ADS)

Chen, Xueyuan; Huang, Miaoliang; Luo, Zundu; Huang, Yidong

2001-09-01

We report on the nonlinear optical properties of Nd:Ca 4GdO(BO 3) 3 (Nd:GdCOB) and Nd:Ca 4YO(BO 3) 3 (Nd:YCOB) biaxial crystals by theoretical calculation. The phase-matching curves for the self-frequency conversion generation of both crystals are presented. The dependence of the effective nonlinear coefficients and walk-off angles on different phase-matching directions are discussed. The results show that the optimum type-I phase-matching directions for the self-frequency doubling and self-sum-frequency mixing lasers are not in the principal planes but are located respectively in the directions ( θ=67.1°, ϕ=132.35°) and ( θ=68.75°, ϕ=118.1°) for Nd:GdCOB, and ( θ=66.5°, ϕ=143.4°) and ( θ=65.9°, ϕ=134.1°) for Nd:YCOB.

[Imaging and quantitative measurement of brain extracellular space using MRI Gd-DTPA tracer method].

PubMed

He, Qing-yuan; Han, Hong-bin; Xu, Fang-jing-wei; Yan, Jun-hao; Zeng, Jin-jin; Li, Xiao-gang; Fu, Yu; Peng, Yun; Chen, He; Hou, Chao; Xu, Xiao-juan

2010-04-18

To observe the diffusion of Gd-DTPA in brain extracellular space (ECS) by magnetic resonance imaging(MRI) and investigate the feasibility of ECS measurement by using MRI tracer method in vivo. 2 microL Gd-DTPA was introduced into ECS by caudate nucleus according to stereotaxic atlas in 8 Sprague Dawley(SD) rats (male, 280-320 g). The MRI scans were performed at 1 h, 3 h, 6 h, 9 h and 12 h respectively after administration. MRI appearances of Gd-DTPA diffusion and distribution was observed and compared. The MRI signal enhancement was measured at each time point. The neuroethology assessment was performed after MRI scanning at 12 h. The injection was accurate at the center of the caudate nucleus in 6 rats, while, at the capsula externa in other 2 rats. Gd-DTPA diffused isotropically after it was introduced into caudate nucleus, which spread into lateral cortex at 3 h. The MRI signal enhancement distributed mainly in the middle cerebral artery territory. A significant difference was found between the signal enhancement ratio at 1 h and that at 3 h in the original point of caudate nucleus (t=95.63, P<0.01), and the signal enhancement attenuated following the exponential power function y=1.7886x(-0.1776) (R2=0.94). In 2 rats with the injection point at capsula externa, Gd-DTPA diffused anisotropically along the fiber track of white matter during 1 h to 3 h, and spread into the lateral cortex at 6 h. The diffusion and clearance of Gd-DTPA in brain ECS could be monitored and measured quantitatively in vivo by MRI tracer method.

Resonant excited UV luminescence of the Gd3+ centres in borate glasses, co-doped with Gd and Ag

NASA Astrophysics Data System (ADS)

Padlyak, B. V.; Drzewiecki, A.; Padlyak, T. B.; Adamiv, V. T.; Teslyuk, I. M.

2018-05-01

The Li2B4O7:Gd, CaB4O7:Gd, LiCaBO3:Gd, and Li2B4O7:Gd, Ag glasses of high optical quality, obtained by standard technology, have been investigated by electron paramagnetic resonance (EPR) and optical spectroscopy at room temperature. The Gd impurity was added in the raw materials as Gd2O3 oxide in amounts 0.5 and 1.0 mol.%. The Ag impurity was introduced into the Li2B4O7 composition as AgNO3 and as highly dispersed metallic Ag in amount 2.0 mol.%. In all Gd-doped glasses was observed typical for glasses EPR U-spectrum of the Gd3+ (8S7/2, 4f7) ions. In the Gd-doped glasses upon the 273 nm excitation was observed weak UV emission line at 311 nm that is attributed to the 6P7/2 → 8S7/2 intraconfiguration 4f - 4f transition of the Gd3+ ions. In the Li2B4O7:Gd, Ag glass has been observed significant (∼100 times) increasing of peak intensity of the Gd3+ emission line at 311 nm in comparison with this line in CaB4O7:Gd glass. In luminescence excitation spectra of the CaB4O7:Gd and Li2B4O7:Gd, Ag glasses are observed characteristic groups of lines corresponding to the 8S7/2 → 6IJ, 6DJ transitions of the Gd3+ ions. Significant increasing of the Gd3+ emission line at 311 nm in the Li2B4O7:Gd, Ag glass is explained by energy transfer from Ag+ (4d10) to Gd3+ (4f7) upon 273 nm excitation that is resonant for 4d10 → 4d9 5s1 (1S0 → 1D2) and 8S7/2 → 6IJ transitions of the Ag+ and Gd3+ ions. Luminescence kinetics of the Gd3+ and Ag+ centres was investigated and analysed. Obtained results show that the borate glasses, co-activated by Gd3+ and Ag+, can be promising materials for effective UVB light sources for biomedical applications.

Detecting Protein-Glycolipid Interactions Using Glycomicelles and CaR-ESI-MS

NASA Astrophysics Data System (ADS)

Han, Ling; Kitova, Elena N.; Klassen, John S.

2016-11-01

This study reports on the use of the catch-and-release electrospray ionization mass spectrometry (CaR-ESI-MS) assay, combined with glycomicelles, as a method for detecting specific interactions between water-soluble proteins and glycolipids (GLs) in aqueous solution. The B subunit homopentamers of cholera toxin (CTB5) and Shiga toxin type 1 B (Stx1B5) and the gangliosides GM1, GM2, GM3, GD1a, GD1b, GT1b, and GD2 served as model systems for this study. The CTB5 exhibits broad specificity for gangliosides and binds to GM1, GM2, GM3, GD1a, GD1b, and GT1b; Stx1B5 does not recognize gangliosides. The CaR-ESI-MS assay was used to analyze solutions of CTB5 or Stx1B5 and individual gangliosides (GM1, GM2, GM3, GD1a, GD1b, GT1b, and GD2) or mixtures thereof. The high affinity interaction of CTB5 with GM1 was successfully detected. However, the apparent affinity, as determined from the mass spectra, is significantly lower than that of the corresponding pentasaccharide or when GM1 is presented in model membranes such as nanodiscs. Interactions between CTB5 and the low affinity gangliosides GD1a, GD1b, and GT1b, as well as GD2, which served as a negative control, were detected; no binding of CTB5 to GM2 or GM3 was observed. The CaR-ESI-MS results obtained for Stx1B5 reveal that nonspecific protein-ganglioside binding can occur during the ESI process, although the extent of binding varies between gangliosides. Consequently, interactions detected for CTB5 with GD1a, GD1b, and GT1b are likely nonspecific in origin. Taken together, these results reveal that the CaR-ESI-MS/glycomicelle approach for detecting protein-GL interactions is prone to false positives and false negatives and must be used with caution.

Detecting Protein-Glycolipid Interactions Using Glycomicelles and CaR-ESI-MS.

PubMed

Han, Ling; Kitova, Elena N; Klassen, John S

2016-11-01

This study reports on the use of the catch-and-release electrospray ionization mass spectrometry (CaR-ESI-MS) assay, combined with glycomicelles, as a method for detecting specific interactions between water-soluble proteins and glycolipids (GLs) in aqueous solution. The B subunit homopentamers of cholera toxin (CTB 5 ) and Shiga toxin type 1 B (Stx1B 5 ) and the gangliosides GM1, GM2, GM3, GD1a, GD1b, GT1b, and GD2 served as model systems for this study. The CTB 5 exhibits broad specificity for gangliosides and binds to GM1, GM2, GM3, GD1a, GD1b, and GT1b; Stx1B 5 does not recognize gangliosides. The CaR-ESI-MS assay was used to analyze solutions of CTB 5 or Stx1B 5 and individual gangliosides (GM1, GM2, GM3, GD1a, GD1b, GT1b, and GD2) or mixtures thereof. The high affinity interaction of CTB 5 with GM1 was successfully detected. However, the apparent affinity, as determined from the mass spectra, is significantly lower than that of the corresponding pentasaccharide or when GM1 is presented in model membranes such as nanodiscs. Interactions between CTB 5 and the low affinity gangliosides GD1a, GD1b, and GT1b, as well as GD2, which served as a negative control, were detected; no binding of CTB 5 to GM2 or GM3 was observed. The CaR-ESI-MS results obtained for Stx1B 5 reveal that nonspecific protein-ganglioside binding can occur during the ESI process, although the extent of binding varies between gangliosides. Consequently, interactions detected for CTB 5 with GD1a, GD1b, and GT1b are likely nonspecific in origin. Taken together, these results reveal that the CaR-ESI-MS/glycomicelle approach for detecting protein-GL interactions is prone to false positives and false negatives and must be used with caution. Graphical Abstract .

Zea mays Annexins Modulate Cytosolic Free Ca2+ and Generate a Ca2+-Permeable Conductance[W

PubMed Central

Laohavisit, Anuphon; Mortimer, Jennifer C.; Demidchik, Vadim; Coxon, Katy M.; Stancombe, Matthew A.; Macpherson, Neil; Brownlee, Colin; Hofmann, Andreas; Webb, Alex A.R.; Miedema, Henk; Battey, Nicholas H.; Davies, Julia M.

2009-01-01

Regulation of reactive oxygen species and cytosolic free calcium ([Ca2+]cyt) is central to plant function. Annexins are small proteins capable of Ca2+-dependent membrane binding or membrane insertion. They possess structural motifs that could support both peroxidase activity and calcium transport. Here, a Zea mays annexin preparation caused increases in [Ca2+]cyt when added to protoplasts of Arabidopsis thaliana roots expressing aequorin. The pharmacological profile was consistent with annexin activation (at the extracellular plasma membrane face) of Arabidopsis Ca2+-permeable nonselective cation channels. Secreted annexins could therefore modulate Ca2+ influx. As maize annexins occur in the cytosol and plasma membrane, they were incorporated at the intracellular face of lipid bilayers designed to mimic the plasma membrane. Here, they generated an instantaneously activating Ca2+-permeable conductance at mildly acidic pH that was sensitive to verapamil and Gd3+ and had a Ca2+-to-K+ permeability ratio of 0.36. These results suggest that cytosolic annexins create a Ca2+ influx pathway directly, particularly during stress responses involving acidosis. A maize annexin preparation also demonstrated in vitro peroxidase activity that appeared independent of heme association. In conclusion, this study has demonstrated that plant annexins create Ca2+-permeable transport pathways, regulate [Ca2+]cyt, and may function as peroxidases in vitro. PMID:19234085

Extracellular biosynthesis of gadolinium oxide (Gd2O3) nanoparticles, their biodistribution and bioconjugation with the chemically modified anticancer drug taxol

PubMed Central

Khan, Shadab Ali; Gambhir, Sanjay

2014-01-01

Summary As a part of our programme to develop nanobioconjugates for the treatment of cancer, we first synthesized extracellular, protein-capped, highly stable and well-dispersed gadolinium oxide (Gd2O3) nanoparticles by using thermophilic fungus Humicola sp. The biodistribution of the nanoparticles in rats was checked by radiolabelling with Tc-99m. Finally, these nanoparticles were bioconjugated with the chemically modified anticancer drug taxol with the aim of characterizing the role of this bioconjugate in the treatment of cancer. The biosynthesized Gd2O3 nanoparticles were characterized by UV–vis spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoemission spectroscopy (XPS). The Gd2O3–taxol bioconjugate was confirmed by UV–vis spectroscopy and fluorescence microscopy and was purified by using high performance liquid chromatography (HPLC). PMID:24778946

Pharmacological analysis of calcium transients in response to gravity vector change in Arabidopsis hypocotyls and petioles.

NASA Astrophysics Data System (ADS)

Toyota, M.; Furuichi, T.; Tatsumi, H.; Sokabe, M.

Plants regulate their growth and morphology in response to gravity field known as gravitropism in general In the process of gravitropism gravity sensing will form the critical earliest event which is supposed to take place in specialized cells statocytes such as columella cells and shoot endodermal cells Although gravistimulation is assumed to be converted into certain intracellular signals the underlying transduction mechanisms have hardly been explored One of the potential candidates for the intracellular signals is an increase in the cytoplasmic free calcium concentration Ca 2 c Here we measured Ca 2 c changes induced by gravistimulation in seedlings of Arabidopsis thaliana expressing aequorin as a calcium reporter When a plate of seedlings was turned through 180 r Ca 2 c transiently increased within 50 s and decayed exponentially with a time constant of ca 60 s The amplitude of the Ca 2 c increase was independent of the angular velocity of the rotation The Ca 2 c increase was reversibly blocked by extracellularly applied potential mechanosensitive channel blockers La 3 Gd 3 or a Ca 2 chelator BAPTA indicating that it arose from Ca 2 -influx via Ca 2 -permeable channel s on the plasma membrane Furthermore the Ca 2 c increase was attenuated by actin-disrupting drugs latrunculin B cytochalasin B but not by microtuble-disrupting drugs oryzalin nocodazole indicating that the activation of

Spontaneous calcium transients in human neural progenitor cells mediated by transient receptor potential channels.

PubMed

Morgan, Peter J; Hübner, Rayk; Rolfs, Arndt; Frech, Moritz J

2013-09-15

Calcium signals affect many developmental processes, including proliferation, migration, survival, and apoptosis, processes that are of particular importance in stem cells intended for cell replacement therapies. The mechanisms underlying Ca(2+) signals, therefore, have a role in determining how stem cells respond to their environment, and how these responses might be controlled in vitro. In this study, we examined the spontaneous Ca(2+) activity in human neural progenitor cells during proliferation and differentiation. Pharmacological characterization indicates that in proliferating cells, most activity is the result of transient receptor potential (TRP) channels that are sensitive to Gd(3+) and La(3+), with the more subtype selective antagonist Ruthenium red also reducing activity, suggesting the involvement of transient receptor potential vanilloid (TRPV) channels. In differentiating cells, Gd(3+) and La(3+)-sensitive TRP channels also appear to underlie the spontaneous activity; however, no sub-type-specific antagonists had any effect. Protein levels of TRPV2 and TRPV3 decreased in differentiated cells, which is demonstrated by western blot. Thus, it appears that TRP channels represent the main route of Ca(2+) entry in human neural progenitor cells (hNPCs), but the responsible channel types are subject to substitution under differentiating conditions. The level of spontaneous activity could be increased and decreased by lowering and raising the extracellular K(+) concentration. Proliferating cells in low K(+) slowed the cell cycle, with a disproportionate increased percentage of cells in G1 phase and a reduction in S phase. Taken together, these results suggest a link between external K(+) concentration, spontaneous Ca(2+) transients, and cell cycle distribution, which is able to influence the fate of stem and progenitor cells.

The Calcium-Sensing Receptor in Health and Disease.

PubMed

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

2016-01-01

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

Effect of Ca and RE additions on microstructures and tensile properties of AZ31 alloys

NASA Astrophysics Data System (ADS)

Fu, Li; Le, Qichi; Tang, Yan; Sun, Jingying; Jia, Yonghui; Song, Zetian

2018-05-01

Microstructures and tensile properties of AZ31 magnesium alloys with the same amount of Ca and RE (Gd + La) additions are investigated. The results show that Al2Ca new phases form after adding Ca elements, Al2Gd and Al11La3 new phases form after adding Gd and La elements, and formations of Al-Ca and Al-RE phases could decrease Mg17Al12 phases and refine grains. Al2Ca and Al11La3 phases are crushed into granules because of severe deformation during hot extrusion, while Al2Gd phases are not. Room temperature (TR) and 150 °C (T150°C) tensile tests results reveal that both AZ31-1.5Ca and AZ31-1.5RE as-extruded alloys exhibit superior comprehensive tensile properties when compared to AZ31 as-extruded alloy, however, AZ31-1.5Ca as-extruded alloy could be a better choice in view of the costs. Textures images of as-extruded alloys indicate that 1.5 wt% Ca and RE additions affects little on textures of AZ31 as-extruded alloy, therefore, morphologies of second phases and average grain sizes are the leading cause of tensile properties of as-extruded alloys.

Spectral management and morphology evolution of β-NaGdF4:Yb3+,Er3+ by tuning the concentration of citric acid

NASA Astrophysics Data System (ADS)

Yao, Lu; Xu, Dekang; Lin, Hao; Yang, Shenghong; Zhang, Yueli

2018-05-01

β-NaGdF4:Yb3+,Er3+ upconversion (UC) particles were prepared by a facile hydrothermal process with assistance of citric acid (CA). The morphologies of β-NaGdF4 UC particles were controlled by changing the doses of CA in precursor. With an increase CA concentration in precursor, increase sizes of crystals were observed, resulting in the increasing of luminescence intensity. The energy transfer ET mechanism was analyzed in detail.

Pr:Ca1-xRxF2+x (R=Y or Gd) crystals: Modulated blue, orange and red emission spectra with the proportion of R3+ ions

NASA Astrophysics Data System (ADS)

Yu, Hao; Qian, Xiaobo; Guo, Linyang; Jiang, Dapeng; Wu, Qinghui; Tang, Fei; Su, Liangbi; Ju, Qiangwen; Wang, Jingya; Xu, Jun

2018-04-01

The spectroscopic properties of 0.6at.%:Pr:Ca1-xRxF2+x (R = Y, Gd; x = 0,0.006, 0.012, 0.03, 0.06) crystals were investigated and compared. The XRD tests were conducted and the cell dimensions of the crystals were calculated. Room temperature absorption spectra have been registered and analyzed. The emission spectra and decay curves of the crystals were obtained at room temperature. Increasing the proportion of the lattice regulators of Y3+ or Gd3+ ions could significantly enhance the luminescence intensity of all visible emission bands with different ratios. Particularly, the emission intensity ratio of orange to red increased from 0.15 to 1.9 in Pr:Ca1-xYxF2+x crystals and to 1.02 in Pr:Ca1-xGdxF2+x crystals, respectively. Furthermore, Pr:Ca1-xGdxF2+x crystals have substantially strong emission at orange and red region of 580-660 nm, comparable with blue light at 482 nm. The quantum efficiency of the crystals increased rapidly with the increment of R3+ concentration, and finally tend to be 100%.

Involvement of amygdalar extracellular zinc in rat behavior for passive avoidance.

PubMed

Takeda, Atsushi; Minami, Akira; Yamaide, Rie; Oku, Naoto

2004-03-25

On the basis of the evidence that zinc is released from glutamatergic neuron terminals in the amygdala, the effect of chelation of amygdalar extracellular zinc on glutamate release from the neuron terminals was studied by using in vivo microdialysis. When the amygdala was perfused with 100 microM CaEDTA to chelate extracellular zinc, glutamate concentration in the perfusate was decreased significantly, whereas that tended to be increased by perfusion with 100 microM ZnEDTA as a control. The effect of CaEDTA on extracellular glutamate levels was different between the amygdala and hippocampus, implying that modulation of glutamate signaling by zinc is different between them. To evaluate chelation of zinc in rat behavior, perfusion of the amygdala with CaEDTA was started 40 min before behavioral test for passive avoidance. The behavior for passive avoidance was impaired during perfusion with CaEDTA. On the other hand, the behavior during perfusion with ZnEDTA was more rapidly developed than that with vehicle only. These results suggest that amygdalar extracellular zinc is involved in the behavior for passive avoidance.

Highly intensified upconversion luminescence of Ca(2+) -doped Yb/Er:NaGdF(4) nanocrystals prepared by a solvothermal route.

PubMed

Lei, Lei; Chen, Daqin; Xu, Ju; Zhang, Rui; Wang, Yuansheng

2014-03-01

Upon introducing Ca(2+) dopants into the grain lattices by substituting Gd(3+) ions, irregular Yb/Er:NaGdF4 nanocrystals prepared through a simple solvothermal route convert into highly uniform nanorods. Meanwhile, their upconversion luminescence intensifies by about 200 times, probably due to a modification of the crystal structure of NaGdF4 and an improvement in the crystallinity of the nanophase. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ca2+/Calmodulin-Dependent Protein Kinase Kinases (CaMKKs) Effects on AMP-Activated Protein Kinase (AMPK) Regulation of Chicken Sperm Functions.

PubMed

Nguyen, Thi Mong Diep; Combarnous, Yves; Praud, Christophe; Duittoz, Anne; Blesbois, Elisabeth

2016-01-01

Sperm require high levels of energy to ensure motility and acrosome reaction (AR) accomplishment. The AMP-activated protein kinase (AMPK) has been demonstrated to be strongly involved in the control of these properties. We address here the question of the potential role of calcium mobilization on AMPK activation and function in chicken sperm through the Ca(2+)/calmodulin-dependent protein kinase kinases (CaMKKs) mediated pathway. The presence of CaMKKs and their substrates CaMKI and CaMKIV was evaluated by western-blotting and indirect immunofluorescence. Sperm were incubated in presence or absence of extracellular Ca(2+), or of CaMKKs inhibitor (STO-609). Phosphorylations of AMPK, CaMKI, and CaMKIV, as well as sperm functions were evaluated. We demonstrate the presence of both CaMKKs (α and β), CaMKI and CaMKIV in chicken sperm. CaMKKα and CaMKI were localized in the acrosome, the midpiece, and at much lower fluorescence in the flagellum, whereas CaMKKβ was mostly localized in the flagellum and much less in the midpiece and the acrosome. CaMKIV was only present in the flagellum. The presence of extracellular calcium induced an increase in kinases phosphorylation and sperm activity. STO-609 reduced AMPK phosphorylation in the presence of extracellular Ca(2+) but not in its absence. STO-609 did not affect CaMKIV phosphorylation but decreased CaMKI phosphorylation and this inhibition was quicker in the presence of extracellular Ca(2+) than in its absence. STO-609 efficiently inhibited sperm motility and AR, both in the presence and absence of extracellular Ca(2+). Our results show for the first time the presence of CaMKKs (α and β) and one of its substrate, CaMKI in different subcellular compartments in germ cells, as well as the changes in the AMPK regulation pathway, sperm motility and AR related to Ca(2+) entry in sperm through the Ca(2+)/CaM/CaMKKs/CaMKI pathway. The Ca(2+)/CaMKKs/AMPK pathway is activated only under conditions of extracellular Ca(2+) entry in the cells.

Abnormal thermal expansion, multiple transitions, magnetocaloric effect, and electronic structure of Gd{sub 6}Co{sub 4.85}

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

Zhang, Jiliang; Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716; Zheng, Zhigang

2015-10-07

The structure of known Gd{sub 4}Co{sub 3} compound is re-determined as Gd{sub 6}Co{sub 4.85}, adopting the Gd{sub 6}Co{sub 1.67}Si{sub 3} structure type, which is characterized by two disorder Co sites filling the Gd octahedral and a short Gd-Gd distance within the octahedra. The compound shows uniaxial negative thermal expansion in paramagnetic state, significant negative expansion in ferromagnetic state, and positive expansion below ca. 140 K. It also exhibits large magnetocaloric effect, with an entropy change of −6.4 J kg{sup −1} K{sup −1} at 50 kOe. In the lattice of the compound, Co atoms at different sites show different spin states. It was confirmed by themore » X-ray photoelectron spectra and calculation of electronic structure and shed lights on the abnormal thermal expansion. The stability of such compound and the origin of its magnetism are also discussed based on measured and calculated electronic structures.« less

A small MRI contrast agent library of gadolinium(III)-encapsulated supramolecular nanoparticles for improved relaxivity and sensitivity**

PubMed Central

Chen, Kuan-Ju; Wolahan, Stephanie M.; Wang, Hao; Hsu, Chao-Hsiung; Chang, Hsing-Wei; Durazo, Armando; Hwang, Lian-Pin; Garcia, Mitch A.; Jiang, Ziyue Karen; Wu, Lily

2010-01-01

We introduce a new category of nanoparticle-based T1 MRI contrast agents (CAs) by encapsulating paramagnetic chelated gadolinium(III), i.e., Gd3+·DOTA, through supramolecular assembly of molecular building blocks that carry complementary molecular recognition motifs, including adamantane (Ad) and β-cyclodextrin (CD). A small library of Gd3+·DOTA-encapsulated supramolecular nanoparticles (Gd3+·DOTA⊂SNPs) was produced by systematically altering the molecular building block mixing ratios. A broad spectrum of relaxation rates was correlated to the resulting Gd3+·DOTA⊂SNP library. Consequently, an optimal synthetic formulation of Gd3+·DOTA⊂SNPs with an r1 of 17.3 s−1mM−1 (ca. 4-fold higher than clinical Gd3+ chelated complexes at high field strengths) was identified. T1-weighted imaging of Gd3+·DOTA⊂SNPs exhibits an enhanced sensitivity with a contrast-to-noise ratio (C/N ratio) ca. 3.6 times greater than that observed for free Gd3+·DTPA. A Gd3+·DOTA⊂SNPs solution was injected into foot pads of mice, and MRI was employed to monitor dynamic lymphatic drainage of the Gd3+·DOTA⊂SNPs-based CA. We observe an increase in signal intensity of the brachial lymph node in T1-weighted imaging after injecting Gd3+·DOTA⊂SNPs but not after injecting Gd3+·DTPA. The MRI results are supported by ICP-MS analysis ex vivo. These results show that Gd3+·DOTA⊂SNPs not only exhibits enhanced relaxivity and high sensitivity but also can serve as a potential tool for diagnosis of cancer metastasis. PMID:21167594

Extracellular calmodulin regulates growth and cAMP-mediated chemotaxis in Dictyostelium discoideum

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

O'Day, Danton H., E-mail: danton.oday@utoronto.ca; Department of Biology, University of Toronto Mississauga, 3359 Mississauga Rd. N., Mississauga, Ontario, Canada L5L 1C6; Huber, Robert J.

2012-09-07

Highlights: Black-Right-Pointing-Pointer Extracellular calmodulin is present throughout growth and development in Dictyostelium. Black-Right-Pointing-Pointer Extracellular calmodulin localizes within the ECM during development. Black-Right-Pointing-Pointer Extracellular calmodulin inhibits cell proliferation and increases chemotaxis. Black-Right-Pointing-Pointer Extracellular calmodulin exists in eukaryotic microbes. Black-Right-Pointing-Pointer Extracellular calmodulin may be functionally as important as intracellular calmodulin. -- Abstract: The existence of extracellular calmodulin (CaM) has had a long and controversial history. CaM is a ubiquitous calcium-binding protein that has been found in every eukaryotic cell system. Calcium-free apo-CaM and Ca{sup 2+}/CaM exert their effects by binding to and regulating the activity of CaM-binding proteins (CaMBPs). Most of themore » research done to date on CaM and its CaMBPs has focused on their intracellular functions. The presence of extracellular CaM is well established in a number of plants where it functions in proliferation, cell wall regeneration, gene regulation and germination. While CaM has been detected extracellularly in several animal species, including frog, rat, rabbit and human, its extracellular localization and functions are less well established. In contrast the study of extracellular CaM in eukaryotic microbes remains to be done. Here we show that CaM is constitutively expressed and secreted throughout asexual development in Dictyostelium where the presence of extracellular CaM dose-dependently inhibits cell proliferation but increases cAMP mediated chemotaxis. During development, extracellular CaM localizes within the slime sheath where it coexists with at least one CaMBP, the matricellular CaM-binding protein CyrA. Coupled with previous research, this work provides direct evidence for the existence of extracellular CaM in the Dictyostelium and provides insight into its functions in this model amoebozoan.« less

Modifying the size and uniformity of upconversion Yb/Er:NaGdF4 nanocrystals through alkaline-earth doping.

PubMed

Lei, Lei; Chen, Daqin; Huang, Ping; Xu, Ju; Zhang, Rui; Wang, Yuansheng

2013-11-21

NaGdF4 is regarded as an ideal upconversion (UC) host material for lanthanide (Ln(3+)) activators because of its unique crystal structure, high Ln(3+) solubility, low phonon energy and high photochemical stability, and Ln(3+)-doped NaGdF4 UC nanocrystals (NCs) have been widely investigated as bio-imaging and magnetic resonance imaging agents recently. To realize their practical applications, controlling the size and uniformity of the monodisperse Ln(3+)-doped NaGdF4 UC NCs is highly desired. Unlike the routine routes by finely adjusting the multiple experimental parameters, herein we provide a facile and straightforward strategy to modify the size and uniformity of NaGdF4 NCs via alkaline-earth doping for the first time. With the increase of alkaline-earth doping content, the size of NaGdF4 NCs increases gradually, while the size-uniformity is still retained. We attribute this "focusing" of size distribution to the diffusion controlled growth of NaGdF4 NCs induced by alkaline-earth doping. Importantly, adopting the Ca(2+)-doped Yb/Er:NaGdF4 NCs as cores, the complete Ca/Yb/Er:NaGdF4@NaYF4 core-shell particles with excellent size-uniformity can be easily achieved. However, when taking the Yb/Er:NaGdF4 NCs without Ca(2+) doping as cores, they could not be perfectly covered by NaYF4 shells, and the obtained products are non-uniform in size. As a result, the UC emission intensity of the complete core-shell NCs increases by about 30 times in comparison with that of the cores, owing to the effective surface passivation of the Ca(2+)-doped cores and therefore protection of Er(3+) in the cores from the non-radiative decay caused by surface defects, whereas the UC intensity of the incomplete core-shell NCs is enhanced by only 3 times.

Tumor Xenograft Response to Redox-Active Therapies Assessed by Magnetic Resonance Imaging Using a Thiol-Bearing DOTA Complex of Gadolinium1

PubMed Central

Guntle, Gerald P; Jagadish, Bhumasamudram; Mash, Eugene A; Powis, Garth; Dorr, Robert T; Raghunand, Natarajan

2012-01-01

Gd-LC6-SH is a thiol-bearing DOTA complex of gadolinium designed to bind plasma albumin at the conserved Cys34 site. The binding of Gd-LC6-SH shows sensitivity to the presence of competing thiols. We hypothesized that Gd-LC6-SH could provide magnetic resonance imaging (MRI) enhancement that is sensitive to tumor redox state and that the prolonged retention of albumin-bound Gd-LC6-SH in vivo can be exploited to identify a saturating dose above which the shortening of MRI longitudinal relaxation time (T1) of tissue is insensitive to the injected gadolinium dose. In the Mia-PaCa-2 pancreatic tumor xenograft model in SCID mice, both the small-molecule Gd-DTPA-BMA and the macromolecule Galbumin MRI contrast agents produced dose-dependent decreases in tumor T1. By contrast, the decreases in tumor T1 provided by Gd-LC6-SH at 0.05 and 0.1 mmol/kg were not significantly different at longer times after injection. SCID mice bearing Mia-PaCa-2 or NCI-N87 tumor xenografts were treated with either the glutathione synthesis inhibitor buthionine sulfoximine or the thiol-oxidizing anticancer drug Imexon, respectively. In both models, there was a significantly greater increase in tumor R1 (=1/T1) 60 minutes after injection of Gd-LC6-SH in drug-treated animals relative to saline-treated controls. In addition, Mercury Orange staining for nonprotein sulfhydryls was significantly decreased by drug treatment relative to controls in both tumor models. In summary, these studies show that thiol-bearing complexes of gadolinium such as Gd-LC6-SH can serve as redox-sensitive MRI contrast agents for detecting differences in tumor redox status and can be used to evaluate the effects of redox-active drugs. PMID:22741038

Growth, improved thermal stability and spectral properties of Yb3+-ions doped high temperature phase α-Ba3Gd(BO3)3 crystals co-doped by Sr2+, Ca2+ and La3+ ions

NASA Astrophysics Data System (ADS)

Pan, Shangke; Zhang, Jianyu; Pan, Jianguo

2018-02-01

To investigate the cause of the thermal instability of Yb3+-ions doped Ba3Gd(BO3)3 crystal grown from Czochralski technique, the low temperature phase β-Ba3Gd(BO3)3 powder was synthesized at the temperature of 800 °C. To inhibit the phase transition of high temperature phase Yb:α-Ba3Gd(BO3)3 during the crystal growth process, co-doping ions Sr2+, Ca2+ and La3+ ions were introduced in Yb:α-Ba3Gd(BO3)3 crystal. The melting point increased and the thermal stability of Yb:α-Ba3Gd(BO3)3 crystal was improved by co-doping ions. The absorption peaks of co-doped crystals centered at 976 nm with FWHM of 11, 11 and 12 nm and the absorption cross sections were 3.40 × 10-21 cm2, 4.00 × 10-21 cm2 and 2.66 × 10-21 cm2, respectively. The emission cross sections at 1040 nm were 2.19 × 10-21 cm2, 2.53 × 10-21 cm2 and 1.93 × 10-21 cm2, respectively. The fluorescence times of co-doped by Sr2+, Ca2+ and La3+ ions were shorter than that of Yb:α-Ba3Gd(BO3)3 crystal. So Yb:α-Ba3Gd(BO3)3 crystals co-doped by Sr2+, Ca2+ and La3+ ions will be more suitable for LD-pumping laser.

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.

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

PubMed Central

2018-01-01

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

Prostate-specific membrane antigen targeted protein contrast agents for molecular imaging of prostate cancer by MRI

NASA Astrophysics Data System (ADS)

Pu, Fan; Salarian, Mani; Xue, Shenghui; Qiao, Jingjuan; Feng, Jie; Tan, Shanshan; Patel, Anvi; Li, Xin; Mamouni, Kenza; Hekmatyar, Khan; Zou, Juan; Wu, Daqing; Yang, Jenny J.

2016-06-01

Prostate-specific membrane antigen (PSMA) is one of the most specific cell surface markers for prostate cancer diagnosis and targeted treatment. However, achieving molecular imaging using non-invasive MRI with high resolution has yet to be achieved due to the lack of contrast agents with significantly improved relaxivity for sensitivity, targeting capabilities and metal selectivity. We have previously reported our creation of a novel class of protein Gd3+ contrast agents, ProCA32, which displayed significantly improved relaxivity while exhibiting strong Gd3+ binding selectivity over physiological metal ions. In this study, we report our effort in further developing biomarker-targeted protein MRI contrast agents for molecular imaging of PSMA. Among three PSMA targeted contrast agents engineered with addition of different molecular recognition sequences, ProCA32.PSMA exhibits a binding affinity of 1.1 +/- 0.1 μM for PSMA while the metal binding affinity is maintained at 0.9 +/- 0.1 × 10-22 M. In addition, ProCA32.PSMA exhibits r1 of 27.6 mM-1 s-1 and r2 of 37.9 mM-1 s-1 per Gd (55.2 and 75.8 mM-1 s-1 per molecule r1 and r2, respectively) at 1.4 T. At 7 T, ProCA32.PSMA also has r2 of 94.0 mM-1 s-1 per Gd (188.0 mM-1 s-1 per molecule) and r1 of 18.6 mM-1 s-1 per Gd (37.2 mM-1 s-1 per molecule). This contrast capability enables the first MRI enhancement dependent on PSMA expression levels in tumor bearing mice using both T1 and T2-weighted MRI at 7 T. Further development of these PSMA-targeted contrast agents are expected to be used for the precision imaging of prostate cancer at an early stage and to monitor disease progression and staging, as well as determine the effect of therapeutic treatment by non-invasive evaluation of the PSMA level using MRI.Prostate-specific membrane antigen (PSMA) is one of the most specific cell surface markers for prostate cancer diagnosis and targeted treatment. However, achieving molecular imaging using non-invasive MRI with high resolution has yet to be achieved due to the lack of contrast agents with significantly improved relaxivity for sensitivity, targeting capabilities and metal selectivity. We have previously reported our creation of a novel class of protein Gd3+ contrast agents, ProCA32, which displayed significantly improved relaxivity while exhibiting strong Gd3+ binding selectivity over physiological metal ions. In this study, we report our effort in further developing biomarker-targeted protein MRI contrast agents for molecular imaging of PSMA. Among three PSMA targeted contrast agents engineered with addition of different molecular recognition sequences, ProCA32.PSMA exhibits a binding affinity of 1.1 +/- 0.1 μM for PSMA while the metal binding affinity is maintained at 0.9 +/- 0.1 × 10-22 M. In addition, ProCA32.PSMA exhibits r1 of 27.6 mM-1 s-1 and r2 of 37.9 mM-1 s-1 per Gd (55.2 and 75.8 mM-1 s-1 per molecule r1 and r2, respectively) at 1.4 T. At 7 T, ProCA32.PSMA also has r2 of 94.0 mM-1 s-1 per Gd (188.0 mM-1 s-1 per molecule) and r1 of 18.6 mM-1 s-1 per Gd (37.2 mM-1 s-1 per molecule). This contrast capability enables the first MRI enhancement dependent on PSMA expression levels in tumor bearing mice using both T1 and T2-weighted MRI at 7 T. Further development of these PSMA-targeted contrast agents are expected to be used for the precision imaging of prostate cancer at an early stage and to monitor disease progression and staging, as well as determine the effect of therapeutic treatment by non-invasive evaluation of the PSMA level using MRI. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr09071g

Enhanced conjugation stability and blood circulation time of macromolecular gadolinium-DTPA contrast agent.

PubMed

Jenjob, Ratchapol; Kun, Na; Ghee, Jung Yeon; Shen, Zheyu; Wu, Xiaoxia; Cho, Steve K; Lee, Don Haeng; Yang, Su-Geun

2016-04-01

In this study, we prepared macromolecular MR T1 contrast agent: pullulan-conjugated Gd diethylene triamine pentaacetate (Gd-DTPA-Pullulan) and estimated residual free Gd(3+), chelation stability in competition with metal ions, plasma and tissue pharmacokinetics, and abdominal MR contrast on rats. Residual free Gd(3+) in Gd-DTPA-Pullulan was measured using colorimetric spectroscopy. The transmetalation of Gd(3+) incubated with Ca(2+) was performed by using a dialysis membrane (MWCO 100-500 Da) and investigated by ICP-OES. The plasma concentration profiles of Gd-DTPA-Pullulan were estimated after intravenous injection at a dose 0.1 mmol/kg of Gd. The coronal-plane abdominal images of normal rats were observed by MR imaging. The content of free Gd(3+), the toxic residual form, was less than 0.01%. Chelation stability of Gd-DTPA-Pullulan was estimated, and only 0.2% and 0.00045% of Gd(3+) were released from Gd-DTPA-Pullulan after 2h incubation with Ca(2+) and Fe(2+), respectively. Gd-DTPA-Pullulan displayed the extended plasma half-life (t1/2,α=0.43 h, t1/2,β=2.32 h), much longer than 0.11h and 0.79 h of Gd-EOB-DTPA. Abdominal MR imaging showed Gd-DTPA-Pullulan maintained initial MR contrast for 30 min. The extended plasma half-life of Gd-DTPA-Pullulan probably allows the prolonged MR acquisition time in clinic with enhanced MR contrast. Copyright © 2016 Elsevier B.V. All rights reserved.

Hydrothermally synthesized PEGylated calcium phosphate nanoparticles incorporating Gd-DTPA for contrast enhanced MRI diagnosis of solid tumors.

PubMed

Mi, Peng; Kokuryo, Daisuke; Cabral, Horacio; Kumagai, Michiaki; Nomoto, Takahiro; Aoki, Ichio; Terada, Yasuko; Kishimura, Akihiro; Nishiyama, Nobuhiro; Kataoka, Kazunori

2014-01-28

Organic-inorganic hybrid nanoparticles with calcium phosphate (CaP) core and PEGylated shell were developed to incorporate magnetic resonance imaging (MRI) contrast agent diethylenetriaminepentaacetic acid gadolinium (III) (Gd-DTPA) for noninvasive diagnosis of solid tumors. A two-step preparation method was applied to elaborate hybrid nanoparticles with a z-average hydrodynamic diameter about 80nm, neutral surface ξ-potential and high colloidal stability in physiological environments by self-assembly of poly(ethylene glycol)-b-poly(aspartic acid) block copolymer, Gd-DTPA, and CaP in aqueous solution, followed with hydrothermal treatment. Incorporation into the hybrid nanoparticles allowed Gd-DTPA to show significant enhanced retention ratio in blood circulation, leading to high accumulation in tumor positions due to enhanced permeability and retention (EPR) effect. Moreover, Gd-DTPA revealed above 6 times increase of relaxivity in the nanoparticle system compared to free form, and eventually, selective and elevated contrast enhancements in the tumor positions were observed. These results indicate the high potential of Gd-DTPA-loaded PEGylated CaP nanoparticles as a novel contrast agent for noninvasive cancer diagnosis. Copyright © 2013 Elsevier B.V. All rights reserved.

Extracellular diffusion quantified by magnetic resonance imaging during rat C6 glioma cell progression.

PubMed

Song, G; Luo, T; Dong, L; Liu, Q

2017-07-03

Solution reflux and edema hamper the convection-enhanced delivery of the standard treatment for glioma. Therefore, a real-time magnetic resonance imaging (MRI) method was developed to monitor the dosing process, but a quantitative analysis of local diffusion and clearance parameters has not been assessed. The objective of this study was to compare diffusion into the extracellular space (ECS) at different stages of rat C6 gliomas, and analyze the effects of the extracellular matrix (ECM) on the diffusion process. At 10 and 20 days, after successful glioma modeling, gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) was introduced into the ECS of rat C6 gliomas. Diffusion parameters and half-life of the reagent were then detected using MRI, and quantified according to the mathematical model of diffusion. The main ECM components [chondroitin sulfate proteoglycans (CSPGs), collagen IV, and tenascin C] were detected by immunohistochemical and immunoblot analyses. In 20-day gliomas, Gd-DTPA diffused more slowly and derived higher tortuosity, with lower clearance rate and longer half-life compared to 10-day gliomas. The increased glioma ECM was associated with different diffusion and clearance parameters in 20-day rat gliomas compared to 10-day gliomas. ECS parameters were altered with C6 glioma progression from increased ECM content. Our study might help better understand the glioma microenvironment and provide benefits for interstitial drug delivery to treat brain gliomas.

Bioinspired design of a polymer gel sensor for the realization of extracellular Ca2+ imaging

NASA Astrophysics Data System (ADS)

Ishiwari, Fumitaka; Hasebe, Hanako; Matsumura, Satoko; Hajjaj, Fatin; Horii-Hayashi, Noriko; Nishi, Mayumi; Someya, Takao; Fukushima, Takanori

2016-04-01

Although the role of extracellular Ca2+ draws increasing attention as a messenger in intercellular communications, there is currently no tool available for imaging Ca2+ dynamics in extracellular regions. Here we report the first solid-state fluorescent Ca2+ sensor that fulfills the essential requirements for realizing extracellular Ca2+ imaging. Inspired by natural extracellular Ca2+-sensing receptors, we designed a particular type of chemically-crosslinked polyacrylic acid gel, which can undergo single-chain aggregation in the presence of Ca2+. By attaching aggregation-induced emission luminogen to the polyacrylic acid as a pendant, the conformational state of the main chain at a given Ca2+ concentration is successfully translated into fluorescence property. The Ca2+ sensor has a millimolar-order apparent dissociation constant compatible with extracellular Ca2+ concentrations, and exhibits sufficient dynamic range and excellent selectivity in the presence of physiological concentrations of biologically relevant ions, thus enabling monitoring of submillimolar fluctuations of Ca2+ in flowing analytes containing millimolar Ca2+ concentrations.

The role of glutamic or aspartic acid in position four of the epitope binding motif and thyrotropin receptor-extracellular domain epitope selection in Graves' disease.

PubMed

Inaba, Hidefumi; Martin, William; Ardito, Matt; De Groot, Anne Searls; De Groot, Leslie J

2010-06-01

Development of Graves' disease (GD) is related to HLA-DRB1*0301 (DR3),and more specifically to arginine at position 74 of the DRB1 molecule. The extracellular domain (ECD) of human TSH receptor (hTSH-R) contains the target antigen. We analyzed the relation between hTSH-R-ECD peptides and DR molecules to determine whether aspartic acid (D) or glutamic acid (E) at position four in the binding motif influenced selection of functional epitopes. Peptide epitopes from TSH-R-ECD with D or E in position four (D/E+) had higher affinity for binding to DR3 than peptides without D/E (D/E-) (IC(50) 29.3 vs. 61.4, P = 0.0024). HLA-DR7, negatively correlated with GD, and DRB1*0302 (HLA-DR18), not associated with GD, had different profiles of epitope binding. Toxic GD patients who are DR3+ had higher responses to D/E+ peptides than D/E- peptides (stimulation index 1.42 vs. 1.22, P = 0.028). All DR3+ GD patients (toxic + euthyroid) had higher responses, with borderline significance (Sl; 1.32 vs. 1.18, P = 0.051). Splenocytes of DR3 transgenic mice immunized to TSH-R-ECD responded to D/E+ peptides more than D/E- peptides (stimulation index 1.95 vs. 1.69, P = 0.036). Seven of nine hTSH-R-ECD peptide epitopes reported to be reactive with GD patients' peripheral blood mononuclear cells contain binding motifs with D/E at position four. TSH-R-ECD epitopes with D/E in position four of the binding motif bind more strongly to DRB1*0301 than epitopes that are D/E- and are more stimulatory to GD patients' peripheral blood mononuclear cells and to splenocytes from mice immunized to hTSH-R. These epitopes appear important in immunogenicity to TSH-R due to their favored binding to HLA-DR3, thus increasing presentation to T cells.

TMEM16A Channels Contribute to the Myogenic Response in Cerebral Arteries

PubMed Central

Bulley, Simon; Neeb, Zachary P.; Burris, Sarah K.; Bannister, John P.; Thomas-Gatewood, Candice M.; Jangsangthong, Wanchana; Jaggar, Jonathan H.

2013-01-01

Rationale Pressure-induced arterial depolarization and constriction (the myogenic response), is a smooth muscle cell (myocyte)-specific mechanism that controls regional organ blood flow and systemic blood pressure. Several different non-selective cation channels contribute to pressure-induced depolarization, but signaling mechanisms involved are unclear. Similarly uncertain is the contribution of anion channels to the myogenic response and physiological functions and mechanisms of regulation of recently discovered transmembrane 16A (TMEM16A) chloride (Cl−) channels in arterial myocytes. Objective Investigate the hypothesis that myocyte TMEM16A channels control membrane potential and contractility and contribute to the myogenic response in cerebral arteries. Methods and Results Cell swelling induced by hyposmotic bath solution stimulated Cl− currents in arterial myocytes that were blocked by TMEM16A channel inhibitory antibodies, RNAi-mediated selective TMEM16A channel knockdown, removal of extracellular calcium (Ca2+), replacement of intracellular EGTA with BAPTA, a fast Ca2+ chelator, and Gd3+ and SKF-96365, non-selective cation channel blockers. In contrast, nimodipine, a voltage-dependent Ca2+ channel inhibitor, or thapsigargin, which depletes intracellular Ca2+ stores, did not alter swelling-activated TMEM16A currents. Pressure (−40 mmHg)-induced membrane stretch activated ion channels in arterial myocyte cell-attached patches that were inhibited by TMEM16A antibodies and were of similar amplitude to recombinant TMEM16A channels. TMEM16A knockdown reduced intravascular pressure-induced depolarization and vasoconstriction, but did not alter depolarization (60 mmol/L K+)-induced vasoconstriction. Conclusions Membrane stretch activates arterial myocyte TMEM16A channels, leading to membrane depolarization and vasoconstriction. Data also provide a mechanism by which a local Ca2+ signal generated by non-selective cation channels stimulates TMEM16A channels to induce myogenic constriction. PMID:22872152

Komatiites of the Onverwacht Group, S. Africa: REE geochemistry, Sm/Nd age and mantle evolution

NASA Astrophysics Data System (ADS)

Jahn, Bor-Ming; Gruau, G.; Glikson, A. Y.

1982-08-01

Komatiites of the Tjakastad Subgroup of the Onverwacht Group (S. Africa) were dated by the Sm/Nd method. A whole-rock isochron yields an age of 3.56±0.24 (2 σ) AE, with initial 143Nd/144Nd ratio of 0.50818±23 (2 σ), corresponding to ɛ Nd( T)= + 1.9±4.5. This age is interpreted as the time of initial Onverwacht volcanism. This result agrees with earlier Sm/Nd data of Hamilton et al. (1979) and is consistent with the Rb-Sr result of Jahn and Shih (1974). Komatiites may be divided into 3 groups based on the typology of heavy REE distributions (Jahn and Gruau 1981). According to this scheme, the Onverwacht komatiites of the present study belong to two groups: the predominant Group II rocks showing (Gd/Yb)N≃1.4, CaO/Al2O3 = 1.33, Al2O3/TiO2≃10.6; and the subordinate Group III rocks with (Gd/Yb)N<1.0; CaO/Al2O3≃0.6 and A12O3/ TiO2≃40. This contrasting feature is best explained by garnet fractionation within the mantle sources. Younger komatiites (˜2.7 AE) from Finland, Canada, Rhodesia, and Australia have (Gd/Yb)N≃1.0, CaO/ Al2O3<1.1 and Al2O3/TiO2≃21 based on 58 analyses. These ratios are nearly chondritic or of the bulk earth value (Anders 1977). It appears that some late Archean komatiites are different in chemistry from many early Archean komatiites. This may imply that the upper mantle chemistry has evolved through Archean times. However, the age connotation of the chemical parameters, such as CaO/Al2O3, (Gd/Yb)N or Al2O3/TiO2 ratio has not been firmly established. The characteristic “high” CaO/Al2O3 or (Gd/Yb)N ratios in many Onverwacht Group rocks can also be explained as a result of local short-term mantle heterogeneity.

Dual-wavelength and efficient continuous-wave operation of a Yb:CaGd0.1Y0.9AlO4 laser

NASA Astrophysics Data System (ADS)

Di, J. Q.; Sai, Q. L.; Sun, X. H.; Xu, X. D.; Kong, L. C.; Xie, G. Q.; Liu, Y. L.; Teng, F.; Zhu, L.

2018-05-01

The spectra and laser properties of single crystalline Yb:CaGd0.1Y0.9AlO4 were investigated for the first time. The peak absorption cross-sections of 4.01 cm2 and 1.39  ×  10‑20 cm2 with full width at half maximum of 17 and 32 nm, and the maximum emission cross-sections of 2.11 and 1.53  ×  10‑20 cm2 were obtained for π and σ polarizations, respectively. The fluorescence decay time was 638 µs. The maximum continuous-wave laser achieved was 1.60 W with a slope efficiency of 23.4% for an a-cut Yb:CaGd0.1Y0.9AlO4 crystal. Dual-wavelength lasers at 1041.7 and 1044.9 nm were also demonstrated. The results show that Yb:CaGd0.1Y0.9AlO4 crystal is a promising ultra-short and dual-wavelength laser medium.

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.

Extracellular calcium triggers unique transcriptional programs and modulates staurosporine-induced cell death in Neurospora crassa

PubMed Central

Gonçalves, A. P.; Monteiro, João; Lucchi, Chiara; Kowbel, David J.; Cordeiro, J. M.; Correia-de-Sá, Paulo; Rigden, Daniel J.; Glass, N. L.; Videira, Arnaldo

2014-01-01

Alterations in the intracellular levels of calcium are a common response to cell death stimuli in animals and fungi and, particularly, in the Neurospora crassa response to staurosporine. We highlight the importance of the extracellular availability of Ca2+ for this response. Limitation of the ion in the culture medium further sensitizes cells to the drug and results in increased accumulation of reactive oxygen species (ROS). Conversely, an approximately 30-fold excess of external Ca2+ leads to increased drug tolerance and lower ROS generation. In line with this, distinct staurosporine-induced cytosolic Ca2+ signaling profiles were observed in the absence or presence of excessive external Ca2+. High-throughput RNA sequencing revealed that different concentrations of extracellular Ca2+ define distinct transcriptional programs. Our transcriptional profiling also pointed to two putative novel Ca2+-binding proteins, encoded by the NCU08524 and NCU06607 genes, and provides a reference dataset for future investigations on the role of Ca2+ in fungal biology. PMID:28357255

The voltage sensor of excitation–contraction coupling in mammals: Inactivation and interaction with Ca2+

PubMed Central

2017-01-01

In skeletal muscle, the four-helix voltage-sensing modules (VSMs) of CaV1.1 calcium channels simultaneously gate two Ca2+ pathways: the CaV1.1 pore itself and the RyR1 calcium release channel in the sarcoplasmic reticulum. Here, to gain insight into the mechanism by which VSMs gate RyR1, we quantify intramembrane charge movement associated with VSM activation (sensing current) and gated Ca2+ release flux in single muscle cells of mice and rats. As found for most four-helix VSMs, upon sustained depolarization, rodent VSMs lose the ability to activate Ca2+ release channels opening; their properties change from a functionally capable mode, in which the mobile sensor charge is called charge 1, to an inactivated mode, charge 2, with a voltage dependence shifted toward more negative voltages. We find that charge 2 is promoted and Ca2+ release inactivated when resting, well-polarized muscle cells are exposed to low extracellular [Ca2+] and that the opposite occurs in high [Ca2+]. It follows that murine VSMs are partly inactivated at rest, which establishes the reduced availability of voltage sensing as a pathogenic mechanism in disorders of calcemia. We additionally find that the degree of resting inactivation is significantly different in two mouse strains, which underscores the variability of voltage sensor properties and their vulnerability to environmental conditions. Our studies reveal that the resting and activated states of VSMs are equally favored by extracellular Ca2+. Promotion by an extracellular species of two states of the VSM that differ in the conformation of the activation gate requires the existence of a second gate, inactivation, topologically extracellular and therefore accessible from outside regardless of the activation state. PMID:29021148

Enhanced emission of encaged-OH--free Ca12(1-x)Sr12xAl14O33:0.1%Gd3+ conductive phosphors via tuning the encaged-electron concentration for low-voltage FEDs.

PubMed

Zhang, Meng; Liu, Yuxue; Yang, Jian; Zhu, Hancheng; Yan, Duanting; Zhang, Xinyang; Liu, Chunguang; Xu, Changshan; Zhang, Hong

2017-05-24

Encaged-OH - -free Ca 12(1-x) Sr 12x Al 14 O 33 :0.1%Gd 3+ conductive phosphors were prepared through a melt-solidification process in combination with a subsequent heat treatment. Absorption spectra showed that the maximum encaged-electron concentration was increased to 1.08 × 10 21 cm -3 through optimizing the doping amount of Sr 2+ (x = 0.005). Meanwhile, FTIR and Raman spectra indicated that pure Ca 11.94 Sr 0.06 Al 14 O 33 :0.1%Gd 3+ conductive phosphor without encaged OH - and C 2 2- anions was acquired. For the conductive powders heat-treated in air for different times, the encaged-electron concentrations were tuned from 1.02 × 10 21 to 8.3 × 10 20 cm -3 . ESR, photoluminescence, and luminescence kinetics analyses indicated that the emission at 312 nm mainly originated from Gd 3+ ions surrounded by encaged O 2- anions, while Gd 3+ ions surrounded by encaged electrons had a negative contribution to the UV emission due to the existence of an energy transfer process. Under low-voltage electron-beam excitation (3 kV), enhanced cathodoluminescence (CL) of the conductive phosphors could be achieved by tuning the encaged-electron concentrations. In particular, for the encaged-OH - -free conductive phosphor, the emission intensity of the CL was about one order of magnitude higher than that of the conductive phosphor containing encaged OH - anions. Our results suggested that the encaged-OH - -free conductive phosphors have potential application in low-voltage FEDs.

Disintegration of collagen fibrils by Glucono-δ-lactone: An implied lead for disintegration of fibrosis.

PubMed

Jayamani, Jayaraman; Ravikanth Reddy, R; Madhan, Balaraman; Shanmugam, Ganesh

2018-02-01

Excess accumulation of collagen (fibrosis) undergoes self-aggregation, which leads to fibrillar collagen, on the extracellular matrix is the hallmark of a number of diseases such as keloids, hypertrophic scars, and systemic scleroderma. Direct inhibition or disintegration of collagen fibrils by small molecules offer a therapeutic approach to prevent or treat the diseases related to fibrosis. Herein, the anti-fibrotic property of Glucono-δ-lactone (GdL), known as acidifier, on the fibrillation and its disintegration of collagen was investigated. As collagen fibrillation is pH dependent, the pH modulation property of GdL is attractive to inhibit self-association of collagen. Optical density and microscopic data indicate that GdL elicits concentration-dependent fibril inhibition and also disintegrates pre-formed collagen fibrils. The simultaneous pH analysis showed that the modulation(lowering) of pH by GdL is the primary cause for its anti-fibrotic activity. The intact triple helical structure of collagen upon treatment of GdL suggests that collagen fibril disintegration can be achieved without affecting the native structure of collagen which is essential for any anti-fibrotic agents. Saturation transfer difference (STD) NMR result reveals that GdL is in proximity to collagen. The present results thus suggest that GdL provides a lead to design novel anti-fibrotic agents for the pathologies related to collagen deposition. Copyright © 2017 Elsevier B.V. All rights reserved.

Type-I non-critically phase-matched second-harmonic generation in Gd1-xYxCa4O(BO3)3

NASA Astrophysics Data System (ADS)

Burmester, P. B. W.; Kellner, T.; Petermann, K.; Huber, G.; Uecker, R.; Reiche, P.

Second-harmonic generation was z-cut observed Gd1-xYxCa4O(BO3)3 (Gd1-xYxCOB) and the dependence of the phase-matching wavelength on the mixing ratio x has been investigated. The dependence on both temperature and angle tuning was examined as well. We found the suitable composition for noncritical frequency doubling at 930 nm, which is the lasing wavelength of Nd:YAlO3 on the 4F3/2?4I9/2 transition.

Kainate toxicity in energy-compromised rat hippocampal slices: differences between oxygen and glucose deprivation.

PubMed

Schurr, A; Rigor, B M

1993-06-18

The effects of kainate (KA) on the recovery of neuronal function in rat hippocampal slices after hypoxia or glucose deprivation (GD) were investigated and compared to those of (R,S)-alpha-amino-3-hydroxy-5-methyl-4- isoxazoleproprionate (AMPA). KA and AMPA were found to be more toxic than either N-methyl-D-aspartate (NMDA), quinolinate, or glutamate, both under normal conditions and under states of energy deprivation. Doses as low as 1 microM KA or AMPA were sufficient to significantly reduce the recovery rate of neuronal function in slices after a standardized period of hypoxia or GD. The enhancement of hypoxic neuronal damage by both agonists could be partially blocked by the antagonist kynurenate, by the NMDA competitive antagonist AP5, and by elevating [Mg2+] in or by omitting Ca2+ from the perfusion medium. The AMPA antagonist glutamic acid diethyl ester was ineffective in preventing the enhanced hypoxic neuronal damage by either KA or AMPA. The antagonist of the glycine modulatory site on the NMDA receptor, 7-chlorokynurenate, did not block the KA toxicity but was able to block the toxicity of AMPA. 2,3-Dihydroxyquinoxaline completely blocked the KA- and AMPA-enhanced hypoxic neuronal damage. The KA-enhanced, GD-induced neuronal damage was prevented by Ca2+ depletion and partially antagonized by kynurenate but not by AP5 or elevated [Mg2+]. The results of the present study indicate that the KA receptor is involved in the mechanism of neuronal damage induced by hypoxia and GD, probably allowing Ca2+ influx and subsequent intracellular Ca2+ overload.(ABSTRACT TRUNCATED AT 250 WORDS)

Conditions of Mytilus edulis extracellular body fluids and shell composition in a pH-treatment experiment: Acid-base status, trace elements and δ11B

NASA Astrophysics Data System (ADS)

Heinemann, Agnes; Fietzke, Jan; Melzner, Frank; BöHm, Florian; Thomsen, JöRn; Garbe-SchöNberg, Dieter; Eisenhauer, Anton

2012-01-01

Mytilus edulis were cultured for 3 months under six different seawater pCO2 levels ranging from 380 to 4000 μatm. Specimen were taken from Kiel Fjord (Western Baltic Sea, Germany) which is a habitat with high and variable seawater pCO2 and related shifts in carbonate system speciation (e.g., low pH and low CaCO3 saturation state). Hemolymph (HL) and extrapallial fluid (EPF) samples were analyzed for pH and total dissolved inorganic carbon (CT) to calculate pCO2 and [HCO3-]. A second experiment was conducted for 2 months with three different pCO2 levels (380, 1400 and 4000 μatm). Boron isotopes (δ11B) were investigated by LA-MC-ICP-MS (Laser Ablation-Multicollector-Inductively Coupled Plasma-Mass Spectrometry) in shell portions precipitated during experimental treatment time. Additionally, elemental ratios (B/Ca, Mg/Ca and Sr/Ca) in the EPF of specimen from the second experiment were measured via ICP-OES (Inductively Coupled Plasma-Optical Emission Spectrometry). Extracellular pH was not significantly different in HL and EPF but systematically lower than ambient water pH. This is due to high extracellular pCO2 values, a prerequisite for metabolic CO2 excretion. No accumulation of extracellular [HCO3-] was measured. Elemental ratios (B/Ca, Mg/Ca and Sr/Ca) in the EPF increased slightly with pH which is in accordance with increasing growth and calcification rates at higher seawater pH values. Boron isotope ratios were highly variable between different individuals but also within single shells. This corresponds to a high individual variability in fluid B/Ca ratios and may be due to high boron concentrations in the organic parts of the shell. The mean δ11B value shows no trend with pH but appears to represent internal pH (EPF) rather than ambient water pH.

Sodium leak channel, non-selective contributes to the leak current in human myometrial smooth muscle cells from pregnant women.

PubMed

Reinl, Erin L; Cabeza, Rafael; Gregory, Ismail A; Cahill, Alison G; England, Sarah K

2015-10-01

Uterine contractions are tightly regulated by the electrical activity of myometrial smooth muscle cells (MSMCs). These cells require a depolarizing current to initiate Ca(2+) influx and induce contraction. Cationic leak channels, which permit a steady flow of cations into a cell, are known to cause membrane depolarization in many tissue types. Previously, a Gd(3+)-sensitive, Na(+)-dependent leak current was identified in the rat myometrium, but the presence of such a current in human MSMCs and the specific ion channel conducting this current was unknown. Here, we report the presence of a Na(+)-dependent leak current in human myometrium and demonstrate that the Na(+)-leak channel, NALCN, contributes to this current. We performed whole-cell voltage-clamp on fresh and cultured MSMCs from uterine biopsies of term, non-laboring women and isolated the leak currents by using Ca(2+) and K(+) channel blockers in the bath solution. Ohmic leak currents were identified in freshly isolated and cultured MSMCs with normalized conductances of 14.6 pS/pF and 10.0 pS/pF, respectively. The myometrial leak current was significantly reduced (P < 0.01) by treating cells with 10 μM Gd(3+) or by superfusing the cells with a Na(+)-free extracellular solution. Reverse transcriptase PCR and immunoblot analysis of uterine biopsies from term, non-laboring women revealed NALCN messenger RNA and protein expression in the myometrium. Notably, ∼90% knockdown of NALCN protein expression with lentivirus-delivered shRNA reduced the Gd(3+)-sensitive leak current density by 42% (P < 0.05). Our results reveal that NALCN, in part, generates the leak current in MSMCs and provide the basis for future research assessing NALCN as a potential molecular target for modulating uterine excitability. © The Author 2015. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

The Calcium-Sensing Receptor Increases Activity of the Renal NCC through the WNK4-SPAK Pathway.

PubMed

Bazúa-Valenti, Silvana; Rojas-Vega, Lorena; Castañeda-Bueno, María; Barrera-Chimal, Jonatan; Bautista, Rocío; Cervantes-Pérez, Luz G; Vázquez, Norma; Plata, Consuelo; Murillo-de-Ozores, Adrián R; González-Mariscal, Lorenza; Ellison, David H; Riccardi, Daniela; Bobadilla, Norma A; Gamba, Gerardo

2018-05-30

Background Hypercalciuria can result from activation of the basolateral calcium-sensing receptor (CaSR), which in the thick ascending limb of Henle's loop controls Ca 2+ excretion and NaCl reabsorption in response to extracellular Ca 2+ However, the function of CaSR in the regulation of NaCl reabsorption in the distal convoluted tubule (DCT) is unknown. We hypothesized that CaSR in this location is involved in activating the thiazide-sensitive NaCl cotransporter (NCC) to prevent NaCl loss. Methods We used a combination of in vitro and in vivo models to examine the effects of CaSR on NCC activity. Because the KLHL3-WNK4-SPAK pathway is involved in regulating NaCl reabsorption in the DCT, we assessed the involvement of this pathway as well. Results Thiazide-sensitive 22 Na + uptake assays in Xenopus laevis oocytes revealed that NCC activity increased in a WNK4-dependent manner upon activation of CaSR with Gd 3+ In HEK293 cells, treatment with the calcimimetic R-568 stimulated SPAK phosphorylation only in the presence of WNK4. The WNK4 inhibitor WNK463 also prevented this effect. Furthermore, CaSR activation in HEK293 cells led to phosphorylation of KLHL3 and WNK4 and increased WNK4 abundance and activity. Finally, acute oral administration of R-568 in mice led to the phosphorylation of NCC. Conclusions Activation of CaSR can increase NCC activity via the WNK4-SPAK pathway. It is possible that activation of CaSR by Ca 2+ in the apical membrane of the DCT increases NaCl reabsorption by NCC, with the consequent, well known decrease of Ca 2+ reabsorption, further promoting hypercalciuria. Copyright © 2018 by the American Society of Nephrology.

A focus on extracellular Ca2+ entry into skeletal muscle

PubMed Central

Cho, Chung-Hyun; Woo, Jin Seok; Perez, Claudio F; Lee, Eun Hui

2017-01-01

The main task of skeletal muscle is contraction and relaxation for body movement and posture maintenance. During contraction and relaxation, Ca2+ in the cytosol has a critical role in activating and deactivating a series of contractile proteins. In skeletal muscle, the cytosolic Ca2+ level is mainly determined by Ca2+ movements between the cytosol and the sarcoplasmic reticulum. The importance of Ca2+ entry from extracellular spaces to the cytosol has gained significant attention over the past decade. Store-operated Ca2+ entry with a low amplitude and relatively slow kinetics is a main extracellular Ca2+ entryway into skeletal muscle. Herein, recent studies on extracellular Ca2+ entry into skeletal muscle are reviewed along with descriptions of the proteins that are related to extracellular Ca2+ entry and their influences on skeletal muscle function and disease. PMID:28912570

Effect of ion concentration changes in the limited extracellular spaces on sarcolemmal ion transport and Ca2+ turnover in a model of human ventricular cardiomyocyte.

PubMed

Hrabcová, Dana; Pásek, Michal; Šimurda, Jiří; Christé, Georges

2013-12-13

We have developed a computer model of human cardiac ventricular myocyte (CVM), including t-tubular and cleft spaces with the aim of evaluating the impact of accumulation-depletion of ions in restricted extracellular spaces on transmembrane ion transport and ionic homeostasis in human CVM. The model was based on available data from human CVMs. Under steady state, the effect of ion concentration changes in extracellular spaces on [Ca2+]i-transient was explored as a function of critical fractions of ion transporters in t-tubular membrane (not documented for human CVM). Depletion of Ca2+ and accumulation of K+ occurring in extracellular spaces slightly affected the transmembrane Ca2+ flux, but not the action potential duration (APD90). The [Ca2+]i-transient was reduced (by 2%-9%), depending on the stimulation frequency, the rate of ion exchange between t-tubules and clefts and fractions of ion-transfer proteins in the t-tubular membrane. Under non-steady state, the responses of the model to changes of stimulation frequency were analyzed. A sudden increase of frequency (1-2.5 Hz) caused a temporal decrease of [Ca2+] in both extracellular spaces, a reduction of [Ca2+]i-transient (by 15%) and APD90 (by 13 ms). The results reveal different effects of activity-related ion concentration changes in human cardiac t-tubules (steady-state effects) and intercellular clefts (transient effects) in the modulation of membrane ion transport and Ca2+ turnover.

High pH-Sensitive TRPA1 Activation in Odontoblasts Regulates Mineralization.

PubMed

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

2016-08-01

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

Ca2+ paradox injury mediated through TRPC channels in mouse ventricular myocytes

PubMed Central

Kojima, Akiko; Kitagawa, Hirotoshi; Omatsu-Kanbe, Mariko; Matsuura, Hiroshi; Nosaka, Shuichi

2010-01-01

BACKGROUND AND PURPOSE The Ca2+ paradox is an important phenomenon associated with Ca2+ overload-mediated cellular injury in myocardium. The present study was undertaken to elucidate molecular and cellular mechanisms for the development of the Ca2+ paradox. EXPERIMENTAL APPROACH Fluorescence imaging was performed on fluo-3 loaded quiescent mouse ventricular myocytes using confocal laser scanning microscope. KEY RESULTS The Ca2+ paradox was readily evoked by restoration of the extracellular Ca2+ following 10–20 min of nominally Ca2+-free superfusion. The Ca2+ paradox was significantly reduced by blockers of transient receptor potential canonical (TRPC) channels (2-aminoethoxydiphenyl borate, Gd3+, La3+) and anti-TRPC1 antibody. The sarcoplasmic reticulum (SR) Ca2+ content, assessed by caffeine application, gradually declined during Ca2+-free superfusion, which was further accelerated by metabolic inhibition. Block of SR Ca2+ leak by tetracaine prevented Ca2+ paradox. The Na+/Ca2+ exchange (NCX) blocker KB-R7943 significantly inhibited Ca2+ paradox when applied throughout superfusion period, but had little effect when added for a period of 3 min before and during Ca2+ restoration. The SR Ca2+ content was better preserved during Ca2+ depletion by KB-R7943. Immunocytochemistry confirmed the expression of TRPC1, in addition to TRPC3 and TRPC4, in mouse ventricular myocytes. CONCLUSIONS AND IMPLICATIONS These results provide evidence that (i) the Ca2+ paradox is primarily mediated by Ca2+ entry through TRPC (probably TRPC1) channels that are presumably activated by SR Ca2+ depletion; and (ii) reverse mode NCX contributes little to the Ca2+ paradox, whereas inhibition of NCX during Ca2+ depletion improves SR Ca2+ loading, and is associated with reduced incidence of Ca2+ paradox in mouse ventricular myocytes. PMID:20718730

Endoplasmic reticulum and lysosomal Ca²⁺ stores are remodelled in GBA1-linked Parkinson disease patient fibroblasts.

PubMed

Kilpatrick, Bethan S; Magalhaes, Joana; Beavan, Michelle S; McNeill, Alisdair; Gegg, Matthew E; Cleeter, Michael W J; Bloor-Young, Duncan; Churchill, Grant C; Duchen, Michael R; Schapira, Anthony H; Patel, Sandip

2016-01-01

Mutations in β-glucocerebrosidase (encoded by GBA1) cause Gaucher disease (GD), a lysosomal storage disorder, and increase the risk of developing Parkinson disease (PD). The pathogenetic relationship between the two disorders is unclear. Here, we characterised Ca(2+) release in fibroblasts from type I GD and PD patients together with age-matched, asymptomatic carriers, all with the common N370S mutation in β-glucocerebrosidase. We show that endoplasmic reticulum (ER) Ca(2+) release was potentiated in GD and PD patient fibroblasts but not in cells from asymptomatic carriers. ER Ca(2+) signalling was also potentiated in fibroblasts from aged healthy subjects relative to younger individuals but not further increased in aged PD patient cells. Chemical or molecular inhibition of β-glucocerebrosidase in fibroblasts and a neuronal cell line did not affect ER Ca(2+) signalling suggesting defects are independent of enzymatic activity loss. Conversely, lysosomal Ca(2+) store content was reduced in PD fibroblasts and associated with age-dependent alterations in lysosomal morphology. Accelerated remodelling of Ca(2+) stores by pathogenic GBA1 mutations may therefore feature in PD. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Crystal growth, polarized spectra, and laser performance of Yb:CaGdAlO4 crystal

NASA Astrophysics Data System (ADS)

Di, J. Q.; Xu, X. D.; Xia, C. T.; Zheng, L. H.; Aka, G.; Yu, H. H.; Sai, Q. L.; Guo, X. Y.; Zhu, L.

2016-04-01

In this paper, the crystal growth, polarized spectra, and laser performance of Yb:CaGdAlO4 crystal were reported. The segregation coefficient of Yb3+ ions was calculated to be 0.47. The cell parameters were determined to be a  =  b  =  0.3658 nm, c  =  1.1985 nm. The peak absorption cross-section was calculated to be 2.65  ×  10-20 cm2 at 979 nm and the peak stimulated emission cross-section was 2.23  ×  10-20 cm2 at 980 nm for the π polarization. The continuous-wave (CW) laser operations of uncoated Yb:CaGdAlO4 crystals with 5  ×  5  ×  3 mm3 in size were demonstrated. A maximum output power of 1.6 W at 1048 nm was obtained with a slope efficiency of 28%. The results show that Yb:CaGdAlO4 crystal is a promising laser medium.

Properties of transparent (Gd,Lu)3(Al,Ga)5O12:Ce ceramic with Mg, Ca and Ce co-dopants

NASA Astrophysics Data System (ADS)

Wang, Yimin; Baldoni, Gary; Brecher, Charles; Rhodes, William H.; Shirwadkar, Urmila; Glodo, Jarek; Shah, Ishaan; Ji, Chuncheng

2015-08-01

Cerium activated mixed lutetium/gadolinium- and aluminum/gallium-based garnets have great potential as host scintillators for medical imaging applications. (Gd,Lu)3(Al,Ga)5O12:Ce and denoted as GLuGAG feature high effective atomic number and good light yield, which make it particularly attractive for Positron Emission Tomography (PET) and other γ-ray detection applications. For PET application, rapid decay and good timing resolution are extremely important. Most Ce-doped mixed garnet materials such as GLuGAG:Ce, have their main decay component at around 80 ns. However, it has been reported that the decays of some single crystal scintillators (e.g., LSO and GGAG) can be effectively accelerated by codoping with selected additives such as Ca, Mg and B. In this study, transparent polycrystalline (Gd,Lu)3(Al,Ga)5O12:Ce ceramics codoped with Ca or Mg or additional Ce, were fabricated by the sinter-HIP approach. It was found the transmission of the ceramics are closely related to the microstructure of the ceramics. As the co-dopant levels increase, 2nd phase occurs in the ceramic and thus transparency of the ceramic decreases. Ca and Mg co-doping in GLuGAG:Ce ceramic effectively accelerate decays of GLuGAG:Ce ceramics at a cost of light output. However, additional Ce doping in the GLuGAG:Ce has no benefit on improving decay time but, on the other hand, reduces transmission, light output. The mechanism under the different scintillation behaviors with Mg, Ca and Ce dopants are discussed. The results suggest that decay time of GLuGAG:Ce ceramics can be effectively tailored by co-doping GLuGAG:Ce ceramic with Mg and Ca for applications with optimal timing resolution.

Extracellular calcium acts as a “third messenger” to regulate enzyme and alkaline secretion

PubMed Central

Caroppo, Rosa; Gerbino, Andrea; Fistetto, Gregorio; Colella, Matilde; Debellis, Lucantonio; Hofer, Aldebaran M.; Curci, Silvana

2004-01-01

It is generally assumed that the functional consequences of stimulation with Ca2+-mobilizing agonists are derived exclusively from the second messenger action of intracellular Ca2+, acting on targets inside the cells. However, during Ca2+ signaling events, Ca2+ moves in and out of the cell, causing changes not only in intracellular Ca2+, but also in local extracellular Ca2+. The fact that numerous cell types possess an extracellular Ca2+ “sensor” raises the question of whether these dynamic changes in external [Ca2+] may serve some sort of messenger function. We found that in intact gastric mucosa, the changes in extracellular [Ca2+] secondary to carbachol-induced increases in intracellular [Ca2+] were sufficient and necessary to elicit alkaline secretion and pepsinogen secretion, independent of intracellular [Ca2+] changes. These findings suggest that extracellular Ca2+ can act as a “third messenger” via Ca2+ sensor(s) to regulate specific subsets of tissue function previously assumed to be under the direct control of intracellular Ca2+. PMID:15240573

Caveolin-1 and glucose transporter 4 involved in the regulation of glucose-deprivation stress in PC12 cells.

PubMed

Zhang, Qi-Qi; Huang, Liang; Han, Chao; Guan, Xin; Wang, Ya-Jun; Liu, Jing; Wan, Jing-Hua; Zou, Wei

2015-08-25

Recent evidence suggests that caveolin-1 (Cav-1), the major protein constituent of caveolae, plays a prominent role in neuronal nutritional availability with cellular fate regulation besides in several cellular processes such as cholesterol homeostasis, regulation of signal transduction, integrin signaling and cell growth. Here, we aimed to investigate the function of Cav-1 and glucose transporter 4 (GLUT4) upon glucose deprivation (GD) in PC12 cells. The results demonstrated firstly that both Cav-1 and GLUT4 were up-regulated by glucose withdrawal in PC12 cells by using Western blot and laser confocal technology. Also, we found that the cell death rate, mitochondrial membrane potential (MMP) and intracellular free Ca(2+) concentration ([Ca(2+)]i) were also respectively changed followed the GD stress tested by CCK8 and flow cytometry. After knocking down of Cav-1 in the cells by siRNA, the level of [Ca(2+)]i was increased, and MMP was reduced further in GD-treated PC12 cells. Knockdown of Cav-1 or methylated-β-Cyclodextrin (M-β-CD) treatment inhibited the expression of GLUT4 protein upon GD. Additionally, we found that GLUT4 could translocate from cytoplasm to cell membrane upon GD. These findings might suggest a neuroprotective role for Cav-1, through coordination of GLUT4 in GD.

Microwave sol–gel synthesis and upconversion photoluminescence properties of CaGd{sub 2}(WO{sub 4}){sub 4}:Er{sup 3+}/Yb{sup 3+} phosphors with incommensurately modulated structure

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

Lim, Chang Sung; Aleksandrovsky, Aleksandr; Department of Photonics and Laser Technologies, Siberian Federal University, Krasnoyarsk 660079

2015-08-15

CaGd{sub 2−x}(WO{sub 4}){sub 4}:Er{sup 3+}/Yb{sup 3+} phosphors with the doping concentrations of Er{sup 3+} and Yb{sup 3+} (x=Er{sup 3+}+Yb{sup 3+}, Er{sup 3+}=0.05, 0.1, 0.2 and Yb{sup 3+}=0.2, 0.45) have been successfully synthesized by the microwave sol–gel method. The crystal structure of CaGd{sub 2−x}(WO{sub 4}){sub 4}:Er{sup 3+}/Yb{sup 3+} tungstates have been refined, and upconversion photoluminescence properties have been investigated. The synthesized particles, being formed after the heat-treatment at 900 °C for 16 h, showed a well crystallized morphology. Under the excitation at 980 nm, CaGd{sub 2}(WO{sub 4}){sub 4}:Er{sup 3+}/Yb{sup 3+} particles exhibited a strong 525-nm and a weak 550-nm emission bandsmore » in the green region and a very weak 655-nm emission band in the red region. The Raman spectrum of undoped CaGd{sub 2}(WO{sub 4}){sub 4} revealed about 12 narrow lines. The strongest band observed at 903 cm{sup −1} was assigned to the ν{sub 1} symmetric stretching vibration of WO{sub 4} tetrahedrons. The spectra of the samples doped with Er and Yb obtained under the 514.5 nm excitation were dominated by Er{sup 3+} luminescence preventing the recording of these samples Raman spectra. Concentration quenching of the erbium luminescence at {sup 2}H{sub 11/2}→{sup 4}I{sub 15/2} transition is weak in the range of erbium doping level x{sub Er}=0.05–0.2, while, for transition {sup 4}S{sub 3/2}→{sup 4}I{sub 15/2}, the signs of concentration quenching become pronounced at x{sub Er}=0.2. - Graphical abstract: CaGd{sub 2−x}(WO{sub 4}){sub 4}:Er{sup 3+}/Yb{sup 3+} phosphors with the doping concentrations of Er{sup 3+} and Yb{sup 3+} (x=Er{sup 3+}+Yb{sup 3+}, Er{sup 3+}=0.05, 0.1, 0.2 and Yb{sup 3+}=0.2, 0.45) have been successfully synthesized by the microwave sol–gel method and the crystal structure refinement, and upconversion photoluminescence properties have been investigated. - Highlights: • CaGd{sub 2−x}(WO{sub 4}){sub 4}:Er{sup 3+}/Yb{sup 3+} phosphors have been synthesized by the microwave sol–gel method. • The crystal structure of CaGd{sub 2−x}(WO{sub 4}){sub 4}:Er{sup 3+}/Yb{sup 3+} tungstates have been refined. • The upconversion photoluminescence properties have been investigated.« less

Reciprocal regulation of two G protein-coupled receptors sensing extracellular concentrations of Ca2+ and H+

PubMed Central

Wei, Wei-Chun; Jacobs, Benjamin; Becker, Esther B. E.; Glitsch, Maike D.

2015-01-01

G protein-coupled receptors (GPCRs) are cell surface receptors that detect a wide range of extracellular messengers and convey this information to the inside of cells. Extracellular calcium-sensing receptor (CaSR) and ovarian cancer gene receptor 1 (OGR1) are two GPCRs that sense extracellular Ca2+ and H+, respectively. These two ions are key components of the interstitial fluid, and their concentrations change in an activity-dependent manner. Importantly, the interstitial fluid forms part of the microenvironment that influences cell function in health and disease; however, the exact mechanisms through which changes in the microenvironment influence cell function remain largely unknown. We show that CaSR and OGR1 reciprocally inhibit signaling through each other in central neurons, and that this is lost in their transformed counterparts. Furthermore, strong intracellular acidification impairs CaSR function, but potentiates OGR1 function. Thus, CaSR and OGR1 activities can be regulated in a seesaw manner, whereby conditions promoting signaling through one receptor simultaneously inhibit signaling through the other receptor, potentiating the difference in their relative signaling activity. Our results provide insight into how small but consistent changes in the ionic microenvironment of cells can significantly alter the balance between two signaling pathways, which may contribute to disease progression. PMID:26261299

Role of gamma carboxylated Glu47 in connexin 26 hemichannel regulation by extracellular Ca{sup 2+}: Insight from a local quantum chemistry study

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

Zonta, Francesco; Mammano, Fabio, E-mail: fabio.mammano@unipd.it; Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, 35129 Padova

2014-02-28

Graphical abstract: - Highlights: • QM calculations show that Ca{sup 2+} binds to γGlu47 in connexin hemichannels. • Molecular models of increasing size are employed in hybrid DFT calculations. • Ca{sup 2+} binding affects the interaction between γGlu47 and Arg75, Arg184. • Ca{sup 2+} binding alters the structure in a critical region of connexin hemichannels. - Abstract: Connexin hemichannels are regulated by several gating mechanisms, some of which depend critically on the extracellular Ca{sup 2+} concentration ([Ca{sup 2+}]{sub e}). It is well established that hemichannel activity is inhibited at normal (∼1 mM) [Ca{sup 2+}]{sub e}, whereas lowering [Ca{sup 2+}]{sub e}more » to micromolar levels fosters hemichannel opening. Atomic force microscopy imaging shows significant and reversible changes of pore diameter at the extracellular mouth of Cx26 hemichannels exposed to different [Ca{sup 2+}]{sub e}, however, the underlying molecular mechanisms are not fully elucidated. Analysis of the crystal structure of connexin 26 (Cx26) gap junction channels, corroborated by molecular dynamics (MD) simulations, suggests that several negatively charged amino acids create a favorable environment for low-affinity Ca{sup 2+} binding within the extracellular vestibule of the Cx26 hemichannel. In particular a highly conserved glutammic acid, found in position 47 in most connexins, is thought to undergo post translational gamma carboxylation (γGlu47), and is thus likely to play an important role in Ca{sup 2+} coordination. γGlu47 may also form salt bridges with two conserved arginines (Arg75 and Arg184 in Cx26), which are considered important in stabilizing the structure of the extracellular region. Using a combination of quantum chemistry methods, we analyzed the interaction between γGlu47, Arg75 and Arg184 in a Cx26 hemichannel model both in the absence and in the presence of Ca{sup 2+}. We show that Ca{sup 2+} imparts significant local structural changes and speculate that these modifications may alter the structure of the extracellular loops in Cx26, and may thus account for the mechanism of hemichannel closure in the presence of mM [Ca{sup 2+}]{sub e}.« less

A non-capacitative pathway activated by arachidonic acid is the major Ca2+ entry mechanism in rat A7r5 smooth muscle cells stimulated with low concentrations of vasopressin

PubMed Central

Broad, Lisa M; Cannon, Toby R; Taylor, Colin W

1999-01-01

Depletion of the Ca2+ stores of A7r5 cells stimulated Ca2+, though not Sr2+, entry. Vasopressin (AVP) or platelet-derived growth factor (PDGF) stimulated Sr2+ entry. The cells therefore express a capacitative pathway activated by empty stores and a non-capacitative pathway stimulated by receptors; only the former is permeable to Mn2+ and only the latter to Sr2+. Neither empty stores nor inositol 1,4,5-trisphosphate (InsP3) binding to its receptors are required for activation of the non-capacitative pathway, because microinjection of cells with heparin prevented PDGF-evoked Ca2+ mobilization but not Sr2+ entry. Low concentrations of Gd3+ irreversibly blocked capacitative Ca2+ entry without affecting AVP-evoked Sr2+ entry. After inhibition of the capacitative pathway with Gd3+, AVP evoked a substantial increase in cytosolic [Ca2+], confirming that the non-capacitative pathway can evoke a significant increase in cytosolic [Ca2+]. Arachidonic acid mimicked the effect of AVP on Sr2+ entry without stimulating Mn2+ entry; the Sr2+ entry was inhibited by 100 μM Gd3+, but not by 1 μM Gd3+ which completely inhibited capacitative Ca2+ entry. The effects of arachidonic acid did not require its metabolism. AVP-evoked Sr2+ entry was unaffected by isotetrandrine, an inhibitor of G protein-coupled phospholipase A2. U73122, an inhibitor of phosphoinositidase C, inhibited AVP-evoked formation of inositol phosphates and Sr2+ entry. The effects of phorbol esters and Ro31-8220 (a protein kinase C inhibitor) established that protein kinase C did not mediate the effects of AVP on the non-capacitative pathway. An inhibitor of diacylglycerol lipase, RHC-80267, inhibited AVP-evoked Sr2+ entry without affecting capacitative Ca2+ entry or release of Ca2+ stores. Selective inhibition of capacitative Ca2+ entry with Gd3+ revealed that the non-capacitative pathway is the major route for the Ca2+ entry evoked by low AVP concentrations. We conclude that in A7r5 cells, the Ca2+ entry evoked by low concentrations of AVP is mediated largely by a non-capacitative pathway directly regulated by arachidonic acid produced by the sequential activities of phosphoinositidase C and diacylglycerol lipase. PMID:10226154

Prostate-specific membrane antigen targeted protein contrast agents for molecular imaging of prostate cancer by MRI†

PubMed Central

Pu, Fan; Salarian, Mani; Xue, Shenghui; Qiao, Jingjuan; Feng, Jie; Tan, Shanshan; Patel, Anvi; Li, Xin; Mamouni, Kenza; Hekmatyar, Khan; Zou, Juan; Wu, Daqing

2017-01-01

Prostate-specific membrane antigen (PSMA) is one of the most specific cell surface markers for prostate cancer diagnosis and targeted treatment. However, achieving molecular imaging using non-invasive MRI with high resolution has yet to be achieved due to the lack of contrast agents with significantly improved relaxivity for sensitivity, targeting capabilities and metal selectivity. We have previously reported our creation of a novel class of protein Gd3+ contrast agents, ProCA32, which displayed significantly improved relaxivity while exhibiting strong Gd3+ binding selectivity over physiological metal ions. In this study, we report our effort in further developing biomarker-targeted protein MRI contrast agents for molecular imaging of PSMA. Among three PSMA targeted contrast agents engineered with addition of different molecular recognition sequences, ProCA32.PSMA exhibits a binding affinity of 1.1 ± 0.1 μM for PSMA while the metal binding affinity is maintained at 0.9 ± 0.1 × 10−22 M. In addition, ProCA32.PSMA exhibits r1 of 27.6 mM−1 s−1 and r2 of 37.9 mM−1 s−1 per Gd (55.2 and 75.8 mM−1 s−1 per molecule r1 and r2, respectively) at 1.4 T. At 7 T, ProCA32.PSMA also has r2 of 94.0 mM−1 s−1 per Gd (188.0 mM−1 s−1 per molecule) and r1 of 18.6 mM−1 s−1 per Gd (37.2 mM−1 s−1 per molecule). This contrast capability enables the first MRI enhancement dependent on PSMA expression levels in tumor bearing mice using both T1 and T2-weighted MRI at 7 T. Further development of these PSMA-targeted contrast agents are expected to be used for the precision imaging of prostate cancer at an early stage and to monitor disease progression and staging, as well as determine the effect of therapeutic treatment by non-invasive evaluation of the PSMA level using MRI. PMID:26961235

Calreticulin localizes to plant intra/extracellular peripheries of highly specialized cells involved in pollen-pistil interactions.

PubMed

Wasąg, Piotr; Suwińska, Anna; Zakrzewski, Przemysław; Walczewski, Jakub; Lenartowski, Robert; Lenartowska, Marta

2018-01-01

Calcium (Ca 2+ ) plays essential roles in generative reproduction of angiosperms, but the sites and mechanisms of Ca 2+ storage and mobilization during pollen-pistil interactions have not been fully defined. Both external and internal Ca 2+ stores are likely important during male gametophyte communication with the sporophytic and gametophytic cells within the pistil. Given that calreticulin (CRT), a Ca 2+ -buffering protein, is able to bind Ca 2+ reversibly, it can serve as a mobile store of easily releasable Ca 2+ (so called an exchangeable Ca 2+ ) in eukaryotic cells. CRT has typical endoplasmic reticulum (ER) targeting and retention signals and resides primarily in the ER. However, localization of this protein outside the ER has also been revealed in both animal and plant cells, including Golgi/dictyosomes, nucleus, plasma membrane/cell surface, plasmodesmata, and even extracellular matrix. These findings indicate that CRT may function in a variety of different cell compartments and specialized structures. We have recently shown that CRT is highly expressed and accumulated in the ER of plant cells involved in pollen-pistil interactions in Petunia, and we proposed an essential role for CRT in intracellular Ca 2+ storage and mobilization during the key reproductive events. Here, we demonstrate that both CRT and exchangeable Ca 2+ are localized in the intra/extracellular peripheries of highly specialized plant cells, such as the pistil transmitting tract cells, pollen tubes, nucellus cells surrounding the embryo sac, and synergids. Based on our present results, we propose that extracellularly located CRT is also involved in Ca 2+ storage and mobilization during sexual reproduction of angiosperms.

Extracellular Ca(2+)-dependent enhancement of cytocidal potency of zoledronic acid in human oral cancer cells.

PubMed

Inoue, Sayaka; Arai, Naoya; Tomihara, Kei; Takashina, Michinori; Hattori, Yuichi; Noguchi, Makoto

2015-08-15

Direct antitumor effects of bisphosphonates (BPs) have been demonstrated in various cancer cells in vitro. However, the effective concentrations of BPs are typically much higher than their clinically relevant concentrations. Oral cancers frequently invade jawbone and may lead to the release of Ca(2+) in primary lesions. We investigated the effects of the combined application of zoledronic acid (ZA) and Ca(2+) on proliferation and apoptosis of oral cancer cells. Human oral cancer cells, breast cancer cells, and colon cancer cells were treated with ZA at a wide range of concentrations in different Ca(2+) concentration environments. Under a standard Ca(2+) concentration (0.6mM), micromolar concentrations of ZA were required to inhibit oral cancer cell proliferation. Increasing extracellular Ca(2+) concentrations greatly enhanced the potency of the ZA cytocidal effect. The ability of Ca(2+) to enhance the cytocidal effects of ZA was negated by the Ca(2+)-selective chelator EGTA. In contrast, the cytocidal effect of ZA was less pronounced in breast and colon cancer cells regardless of whether extracellular Ca(2+) was elevated. In oral cancer cells incubated with 1.6mM Ca(2+), ZA up-regulated mitochondrial Bax expression and increased mitochondrial Ca(2+) uptake. This was associated with decreased mitochondrial membrane potential and increased release of cytochrome c. We suggest that ZA can specifically produce potent cytocidal activity in oral cancer cells in an extracellular Ca(2+)-dependent manner, implying that BPs may be useful for treatment of oral squamous cell carcinoma with jawbone invasion leading to the hypercalcemic state. Copyright © 2015 Elsevier B.V. All rights reserved.

Influence of gamma-irradiation on the non-isothermal decomposition of calcium-gadolinium oxalate

NASA Astrophysics Data System (ADS)

Moharana, S. C.; Praharaj, J.; Bhatta, D.

Thermal decomposition of co-precipitated unirradiated and irradiated Ca-Gd oxalate has been studied by adopting differential thermal analysis (DTA) and thermogravimetric (TG) techniques. The reaction occurs through two stages corresponding to the decomposition of gadolinium oxalate (Gd-Ox) followed by that of calcium oxalate (Ca-Ox). The kinetic parameters for both the stages are calculated by using solid state reaction models and Coats-Redfern's equation. The co-precipitation as well as irradiation alter the DTA peak temperatures and the kinetic parameters of Ca-Ox. The decomposition of Gd-Ox follows the two dimensional Contracting area (R-2) mechanism, while that of Ca-Ox follows the Avrami-Erofeev (A(2)) mechanism (n =2), which are also exhibited by the co-precipitated and irradiated samples. Co-precipitation decreases the energy of activation and the pre-exponential factor of the individual components but the reverse phenomenon takes place upon irradiation of the co-precipitate. The mechanisms underlying the phenomena are explored.

Engineering Synthetic Proteins to Generate Ca2+ Signals in Mammalian Cells.

PubMed

Qudrat, Anam; Truong, Kevin

2017-03-17

The versatility of Ca 2+ signals allows it to regulate diverse cellular processes such as migration, apoptosis, motility and exocytosis. In some receptors (e.g., VEGFR2), Ca 2+ signals are generated upon binding their ligand(s) (e.g., VEGF-A). Here, we employed a design strategy to engineer proteins that generate a Ca 2+ signal upon binding various extracellular stimuli by creating fusions of protein domains that oligomerize to the transmembrane domain and the cytoplasmic tail of the VEGFR2. To test the strategy, we created chimeric proteins that generate Ca 2+ signals upon stimulation with various extracellular stimuli (e.g., rapamycin, EDTA or extracellular free Ca 2+ ). By coupling these chimeric proteins that generate Ca 2+ signals with proteins that respond to Ca 2+ signals, we rewired, for example, dynamic cellular blebbing to increases in extracellular free Ca 2+ . Thus, using this design strategy, it is possible to engineer proteins to generate a Ca 2+ signal to rewire a wide range of extracellular stimuli to a wide range of Ca 2+ -activated processes.

Age-dependent changes in diastolic Ca{sup 2+} and Na{sup +} concentrations in dystrophic cardiomyopathy: Role of Ca{sup 2+} entry and IP{sub 3}

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

Mijares, Alfredo; Altamirano, Francisco; Kolster, Juan

2014-10-03

Highlights: • Age-dependent increase in [Ca{sup 2+}]{sub d} and [Na{sup +}]{sub d} in mdx cardiomyocytes. • Gadolinium significantly reduced both [Ca{sup 2+}]{sub d} and [Na{sup +}]{sub d} at all ages. • IP{sub 3}-pathway inhibition reduced cations concentrations in dystrophic cardiomyocytes. - Abstract: Duchenne muscular dystrophy (DMD) is a lethal X-inherited disease caused by dystrophin deficiency. Besides the relatively well characterized skeletal muscle degenerative processes, DMD is also associated with a dilated cardiomyopathy that leads to progressive heart failure at the end of the second decade. The aim of the present study was to characterize the diastolic Ca{sup 2+} concentration ([Ca{supmore » 2+}]{sub d}) and diastolic Na{sup +} concentration ([Na{sup +}]{sub d}) abnormalities in cardiomyocytes isolated from 3-, 6-, 9-, and 12-month old mdx mice using ion-selective microelectrodes. In addition, the contributions of gadolinium (Gd{sup 3+})-sensitive Ca{sup 2+} entry and inositol triphosphate (IP{sub 3}) signaling pathways in abnormal [Ca{sup 2+}]{sub d} and [Na{sup +}]{sub d} were investigated. Our results showed an age-dependent increase in both [Ca{sup 2+}]{sub d} and [Na{sup +}]{sub d} in dystrophic cardiomyocytes compared to those isolated from age-matched wt mice. Gd{sup 3+} treatment significantly reduced both [Ca{sup 2+}]{sub d} and [Na{sup +}]{sub d} at all ages. In addition, blockade of the IP{sub 3}-pathway with either U-73122 or xestospongin C significantly reduced ion concentrations in dystrophic cardiomyocytes. Co-treatment with U-73122 and Gd{sup 3+} normalized both [Ca{sup 2+}]{sub d} and [Na{sup +}]{sub d} at all ages in dystrophic cardiomyocytes. These data showed that loss of dystrophin in mdx cardiomyocytes produced an age-dependent intracellular Ca{sup 2+} and Na{sup +} overload mediated at least in part by enhanced Ca{sup 2+} entry through Gd{sup 3+} sensitive transient receptor potential channels (TRPC), and by IP{sub 3} receptors.« less

Evaluation of a Gadolinium-Based Nanoparticle (AGuIX) for Contrast-Enhanced MRI of the Liver in a Rat Model of Hepatic Colorectal Cancer Metastases at 9.4 Tesla.

PubMed

Fries, P; Morr, D; Müller, A; Lux, F; Tillement, O; Massmann, A; Seidel, R; Schäfer, T; Menger, M D; Schneider, G; Bücker, A

2015-12-01

The aim of this study was to compare a Gd-based nanoparticle (AGuIX) with a standard extracellular Gd-based contrast agent (Gd-DOTA) for MRI at 9.4 T in rats with hepatic colorectal cancer metastases. 12 rats with hepatic metastases were subjected to MRI using a 9.4 T animal scanner. T1w self-gated FLASH sequences (TR/TE = 45/2.5 ms, alpha = 45°, TA = 1: 23 min, FOV = 5.12 × 5.12 cm(2), matrix = 256 × 256) were acquired before and at 10 time points after contrast injection. Each animal received 0.1 mmol/kg BW Gd-DOTA i.v. 2 days later AGuIX was applied at 0.01 mmol/kg BW (representing equal Gd doses). The SNR of normal liver (SNRliver), hyper- and hypoenhancing parts of tumors (SNRtumor, hyperenh/SNRtumor, hypoenhanc), erector spinae muscle (SNRmuscle), CNR and lesion enhancement (LE) were calculated based on ROI measurements. Mean SNRliver (Gd-DOTA: 14.6 +/- 0.7; AGuIX: 28.2+/- 2.6, p < 0.001), SNRtumor, hyperenhanc (Gd-DOTA: 18.6 +/- 1.2; AGuIX: 29.6 +/- 2.8, p < 0.001), SNRtumor, hypoenhanc (Gd-DOTA: 12.0 +/- 0.7; AGuIX: 15.4 +/- 0.7, p < 0.001), SNRmuscle (Gd-DOTA: 12.3 +/- 0.3; AGuIX: 14.0 +/- 0.7, p < 0.001), mean CNR (Gd-DOTA: -2.5 +/- 0.2; AGuIX: -7.5 +/- 1.0, p < 0.001) and LE (Gd-DOTA: 3.8 +/- 0.7; AGuIX: 14.9 +/- 2.8, p = 0.001) were significantly higher using AGuIX. Regardless of the larger molecular size, AGuIX demonstrates an early peak enhancement followed by a continuous washout. AGuIX provides better enhancement at 9.4 T compared to Gd-DOTA for equal doses of applied Gd. This is based on the molecule structure and the subsequent increased interaction with protons leading to a higher relaxivity. AGuIX potentially ameliorates the conspicuity of focal liver lesions and may improve the sensitivity in diagnostic imaging of malignant hepatic tumors. AGuIX provides superior enhancement as compared to the extracellular compound Gd-DOTA at 9.4 T. AGuIX may improve the detection and diagnostic sensitivity of malignant focal liver lesions. The small size of AGuIX allows for fast renal clearance and prevents undesirable accumulation in the body. © Georg Thieme Verlag KG Stuttgart · New York.

Fe²⁺ block and permeation of CaV3.1 (α1G) T-type calcium channels: candidate mechanism for non-transferrin-mediated Fe²⁺ influx.

PubMed

Lopin, Kyle V; Gray, I Patrick; Obejero-Paz, Carlos A; Thévenod, Frank; Jones, Stephen W

2012-12-01

Iron is a biologically essential metal, but excess iron can cause damage to the cardiovascular and nervous systems. We examined the effects of extracellular Fe²⁺ on permeation and gating of Ca(V)3.1 channels stably transfected in HEK293 cells, by using whole-cell recording. Precautions were taken to maintain iron in the Fe²⁺ state (e.g., use of extracellular ascorbate). With the use of instantaneous I-V currents (measured after strong depolarization) to isolate the effects on permeation, extracellular Fe²⁺ rapidly blocked currents with 2 mM extracellular Ca²⁺ in a voltage-dependent manner, as described by a Woodhull model with K(D) = 2.5 mM at 0 mV and apparent electrical distance δ = 0.17. Extracellular Fe²⁺ also shifted activation to more-depolarized voltages (by ∼10 mV with 1.8 mM extracellular Fe²⁺) somewhat more strongly than did extracellular Ca²⁺ or Mg²⁺, which is consistent with a Gouy-Chapman-Stern model with surface charge density σ = 1 e(-)/98 Ų and K(Fe) = 4.5 M⁻¹ for extracellular Fe²⁺. In the absence of extracellular Ca²⁺ (and with extracellular Na⁺ replaced by TEA), Fe²⁺ carried detectable, whole-cell, inward currents at millimolar concentrations (73 ± 7 pA at -60 mV with 10 mM extracellular Fe²⁺). With a two-site/three-barrier Eyring model for permeation of Ca(V)3.1 channels, we estimated a transport rate for Fe²⁺ of ∼20 ions/s for each open channel at -60 mV and pH 7.2, with 1 μM extracellular Fe²⁺ (with 2 mM extracellular Ca²⁺). Because Ca(V)3.1 channels exhibit a significant "window current" at that voltage (open probability, ∼1%), Ca(V)3.1 channels represent a likely pathway for Fe²⁺ entry into cells with clinically relevant concentrations of extracellular Fe²⁺.

Alkali earth co-doping effects on luminescence and scintillation properties of Ce doped Gd3Al2Ga3O12 scintillator

NASA Astrophysics Data System (ADS)

Kamada, Kei; Nikl, Martin; Kurosawa, Shunsuke; Beitlerova, Alena; Nagura, Aya; Shoji, Yasuhiro; Pejchal, Jan; Ohashi, Yuji; Yokota, Yuui; Yoshikawa, Akira

2015-03-01

The Mg and Ca co-doped Ce:Gd3Al2Ga3O12 single crystals were prepared by micro pulling down method with a wide concentration range 0-1000 ppm of the codopants. Absorption and luminescence spectra were measured together with several other scintillation characteristics, namely the scintillation decay and light yield to reveal the effect of Mg and Ca co-doping. The scintillation decays were accelerated by both Mg and Ca codopants. Comparing to Ca co-doping, the Mg co-doped samples showed much faster decay and comparatively smaller light output decrease with increasing Mg dopant concentration.

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

Sanchez-Miranda, Elizabeth; Ibarra-Sanchez, Alfredo; Gonzalez-Espinosa, Claudia, E-mail: cgonzal@cinvestav.mx

IgE-antigen-dependent crosslinking of the high affinity IgE receptor (Fc{epsilon}RI) on mast cells leads to degranulation, leukotriene synthesis and cytokine production. Calcium (Ca{sup 2+}) mobilization is a sine qua non requisite for degranulation, allowing the rapid secretion of stored pro-inflammatory mediators responsible for allergy symptoms. Fyn is a Src-family kinase that positively controls Fc{epsilon}RI-induced mast cell degranulation. However, our understanding of the mechanism connecting Fyn activation to secretion of pre-synthesized mediators is very limited. We analyzed Fc{epsilon}RI-dependent Ca{sup 2+} mobilization in bone marrow-derived mast cells (BMMCs) differentiated from WT and Fyn -/- knock out mice. Fyn -/- BMMCs showed a markedmore » defect in extracellular Ca{sup 2+} influx after Fc{epsilon}RI crosslinking but not after thapsigargin addition. High concentrations of Gadolinium (Gd{sup 3+}) partially blocked Fc{epsilon}RI-induced Ca{sup 2+} influx in WT cells but, in contrast, completely inhibited Ca{sup 2+} mobilization in Fyn -/- cells. Low concentrations of an inhibitor of the canonical transient receptor potential (TRPC) Ca{sup 2+} channels (2-aminoethoxyphenyl-borane, 2-APB) blocked Fc{epsilon}RI-induced maximal Ca{sup 2+} rise in WT but not in Fyn -/- cells. Ca{sup 2+} entry through Fyn-controlled, 2-APB sensitive channels was found to be important for full degranulation and IL-2 mRNA accumulation in WT cells. Immunoprecipitation assays showed that Fyn kinase interacts with TRPC 3/6/7 channels after IgE-antigen stimulation, but its association is not related to protein tyrosine phosphorylation. Results indicate Fyn kinase mediates the receptor-dependent activation of TRPC channels that contribute to degranulation in Fc{epsilon}RI-stimulated mast cells.« less

Investigation of a calcium-responsive contrast agent in cellular model systems: feasibility for use as a smart molecular probe in functional MRI.

PubMed

Angelovski, Goran; Gottschalk, Sven; Milošević, Milena; Engelmann, Jörn; Hagberg, Gisela E; Kadjane, Pascal; Andjus, Pavle; Logothetis, Nikos K

2014-05-21

Responsive or smart contrast agents (SCAs) represent a promising direction for development of novel functional MRI (fMRI) methods for the eventual noninvasive assessment of brain function. In particular, SCAs that respond to Ca(2+) may allow tracking neuronal activity independent of brain vasculature, thus avoiding the characteristic limitations of current fMRI techniques. Here we report an in vitro proof-of-principle study with a Ca(2+)-sensitive, Gd(3+)-based SCA in an attempt to validate its potential use as a functional in vivo marker. First, we quantified its relaxometric response in a complex 3D cell culture model. Subsequently, we examined potential changes in the functionality of primary glial cells following administration of this SCA. Monitoring intracellular Ca(2+) showed that, despite a reduction in the Ca(2+) level, transport of Ca(2+) through the plasma membrane remained unaffected, while stimulation with ATP induced Ca(2+)-transients suggested normal cellular signaling in the presence of low millimolar SCA concentrations. SCAs merely lowered the intracellular Ca(2+) level. Finally, we estimated the longitudinal relaxation times (T1) for an idealized in vivo fMRI experiment with SCA, for extracellular Ca(2+) concentration level changes expected during intense neuronal activity which takes place upon repetitive stimulation. The values we obtained indicate changes in T1 of around 1-6%, sufficient to be robustly detectable using modern MRI methods in high field scanners. Our results encourage further attempts to develop even more potent SCAs and appropriate fMRI protocols. This would result in novel methods that allow monitoring of essential physiological processes at the cellular and molecular level.

Requirement of extracellular Ca2+ binding to specific amino acids for heat‐evoked activation of TRPA1

PubMed Central

Kurganov, Erkin; Saito, Shigeru; Tanaka Saito, Claire

2017-01-01

Key points We found that extracellular Ca2+, but not other divalent cations (Mg2+ and Ba2+) or intracellular Ca2+, is involved in heat‐evoked activation of green anole (ga) TRPA1.Heat‐evoked activation of chicken (ch) and rat snake (rs) TRPA1 does not depend solely on extracellular Ca2+.Neutralization of acidic amino acids on the outer surface of TRPA1 by extracellular Ca2+ is important for heat‐evoked large activation of gaTRPA1, chTRPA1 and rsTRPA1. Abstract Transient receptor potential ankyrin 1 (TRPA1) is a homotetrameric non‐selective cation‐permeable channel that has six transmembrane domains and cytoplasmic N‐ and C‐termini. The N‐terminus is characterized by an unusually large number of ankyrin repeats. Although the 3‐dimensional structure of human TRPA1 has been determined, and TRPA1 channels from insects to birds are known to be activated by heat stimulus, the mechanism for temperature‐dependent TRPA1 activation is unclear. We previously reported that extracellular Ca2+, but not intracellular Ca2+, plays an important role in heat‐evoked TRPA1 activation in green anole lizards (gaTRPA1). Here we focus on extracellular Ca2+‐dependent heat sensitivity of gaTRPA1 by comparing gaTRPA1 with heat‐activated TRPA1 channels from rat snake (rsTRPA1) and chicken (chTRPA1). In the absence of extracellular Ca2+, rsTRPA1 and chTRPA1 are activated by heat and generate small inward currents. A comparison of extracellular amino acids in TRPA1 identified three negatively charged amino acid residues (glutamate and aspartate) near the outer pore vestibule that are involved in heat‐evoked TRPA1 activation in the presence of extracellular Ca2+. These results suggest that neutralization of acidic amino acids by extracellular Ca2+ is important for heat‐evoked activation of gaTRPA1, chTRPA1, and rsTRPA1, which could clarify mechanisms of heat‐evoked channel activation. PMID:28194754

Gd-DTPA T1 relaxivity in brain tissue obtained by convection-enhanced delivery, magnetic resonance imaging and emission spectroscopy

NASA Astrophysics Data System (ADS)

Haar, Peter J.; Broaddus, William C.; Chen, Zhi-jian; Fatouros, Panos P.; Gillies, George T.; Corwin, Frank D.

2010-06-01

A common approach to quantify gadolinium (Gd) contrast agents involves measuring the post-contrast change in T1 rate and then using the constant T1 relaxivity R to determine the contrast agent concentration. Because this method is fast and non-invasive, it could be potentially valuable in many areas of brain research. However, to accurately measure contrast agent concentrations in the brain, the T1 relaxivity R of the specific agent must be accurately known. Furthermore, the macromolecular content and compartmentalization of the brain extracellular space (ECS) are expected to significantly alter R from values measured in aqueous solutions. In this study, the T1 relaxivity R of gadolinium-diethylene-triamine penta-acetic acid (Gd-DTPA) was measured following direct interstitial infusions of three different contrast agent concentrations to the parenchyma of rat brains. Changes in magnetic resonance (MR) T1 values were compared to brain slice concentrations determined with inductively coupled plasma atomic emission spectroscopy (ICP-AES) to determine R in 15 rats. Additionally, samples of cerebrospinal fluid, blood and urine were analyzed to evaluate possible Gd-DTPA clearance from the brain. The T1 relaxivity R of Gd-DTPA in the brain ECS was measured to be 5.35 (mM s)-1 in a 2.4 T field. This value is considerably higher than estimations used in studies by other groups. Measurements of brain Gd-DTPA tissue concentrations using MRI and ICP-AES demonstrated a high degree of coincidence. Clearance of Gd-DTPA was minimal at the time point immediately after infusion. These results suggest that the environment of the brain does in fact significantly affect Gd T1 relaxivity, and that MRI can accurately measure contrast agent concentrations when this relaxivity is well characterized.

Extracellular Protein Kinase A Modulates Intracellular Calcium/Calmodulin-Dependent Protein Kinase II, Nitric Oxide Synthase, and the Glutamate-Nitric Oxide-cGMP Pathway in Cerebellum. Differential Effects in Hyperammonemia.

PubMed

Cabrera-Pastor, Andrea; Llansola, Marta; Felipo, Vicente

2016-12-21

Extracellular protein kinases, including cAMP-dependent protein kinase (PKA), modulate neuronal functions including N-methyl-d-aspartate (NMDA) receptor-dependent long-term potentiation. NMDA receptor activation increases calcium, which binds to calmodulin and activates nitric oxide synthase (NOS), increasing nitric oxide (NO), which activates guanylate cyclase, increasing cGMP, which is released to the extracellular fluid, allowing analysis of this glutamate-NO-cGMP pathway in vivo by microdialysis. The function of this pathway is impaired in hyperammonemic rats. The aims of this work were to assess (1) whether the glutamate-NO-cGMP pathway is modulated in cerebellum in vivo by an extracellular PKA, (2) the role of phosphorylation and activity of calcium/calmodulin-dependent protein kinase II (CaMKII) and NOS in the pathway modulation by extracellular PKA, and (3) whether the effects are different in hyperammonemic and control rats. The pathway was analyzed by in vivo microdialysis. The role of extracellular PKA was analyzed by inhibiting it with a membrane-impermeable inhibitor. The mechanisms involved were analyzed in freshly isolated cerebellar slices from control and hyperammonemic rats. In control rats, inhibiting extracellular PKA reduces the glutamate-NO-cGMP pathway function in vivo. This is due to reduction of CaMKII phosphorylation and activity, which reduces NOS phosphorylation at Ser1417 and NOS activity, resulting in reduced guanylate cyclase activation and cGMP formation. In hyperammonemic rats, under basal conditions, CaMKII phosphorylation and activity are increased, increasing NOS phosphorylation at Ser847, which reduces NOS activity, guanylate cyclase activation, and cGMP. Inhibiting extracellular PKA in hyperammonemic rats normalizes CaMKII phosphorylation and activity, NOS phosphorylation, NOS activity, and cGMP, restoring normal function of the pathway.

Pasteurella haemolytica A1-Derived Leukotoxin and Endotoxin Induce Intracellular Calcium Elevation in Bovine Alveolar Macrophages by Different Signaling Pathways

PubMed Central

Hsuan, S. L.; Kannan, M. S.; Jeyaseelan, S.; Prakash, Y. S.; Sieck, G. C.; Maheswaran, S. K.

1998-01-01

Leukotoxin and endotoxin derived from Pasteurella haemolytica serotype 1 are the primary virulence factors contributing to the pathogenesis of lung injury in bovine pneumonic pasteurellosis. Activation of bovine alveolar macrophages with endotoxin or leukotoxin results in the induction of cytokine gene expression, with different kinetics (H. S. Yoo, S. K. Maheswaran, G. Lin, E. L. Townsend, and T. R. Ames, Infect. Immun. 63:381–388, 1995; H. S. Yoo, B. S. Rajagopal, S. K. Maheswaran, and T. R. Ames, Microb. Pathog. 18:237–252, 1995). Furthermore, extracellular Ca2+ is required for leukotoxin-induced cytokine gene expression. However, the involvement of Ca2+ in endotoxin effects and the precise signaling mechanisms in the regulation of intracellular Ca2+ by leukotoxin and endotoxin are not known. In fura-2-acetoxymethyl ester-loaded alveolar macrophages, intracellular Ca2+ regulation by leukotoxin and endotoxin was studied by video fluorescence microscopy. Leukotoxin induced a sustained elevation of intracellular Ca2+ in a concentration-dependent fashion by influx of extracellular Ca2+ through voltage-gated channels. In the presence of fetal bovine serum, endotoxin elevated intracellular Ca2+ even in the absence of extracellular Ca2+. Leukotoxin-induced intracellular Ca2+ elevation was inhibited by pertussis toxin, inhibitors of phospholipases A2 and C, and the arachidonic acid analog 5,8,11,14-eicosatetraynoic acid. Intracellular Ca2+ elevation by endotoxin was inhibited by inhibitors of phospholipase C and protein tyrosine kinase, but not by pertussis toxin, or the arachidonic acid analog. To the best of our knowledge, this is the first report of Ca2+ signaling by leukotoxin through a G-protein-coupled mechanism involving activation of phospholipases A2 and C and release of arachidonic acid in bovine alveolar macrophages. Ca2+ signaling by endotoxin, on the other hand, involves activation of phospholipase C and requires tyrosine phosphorylation. The differences in the Ca2+ signaling mechanisms may underlie the reported temporal differences in gene expression during leukotoxin and endotoxin activation. PMID:9596757

Pasteurella haemolytica A1-derived leukotoxin and endotoxin induce intracellular calcium elevation in bovine alveolar macrophages by different signaling pathways.

PubMed

Hsuan, S L; Kannan, M S; Jeyaseelan, S; Prakash, Y S; Sieck, G C; Maheswaran, S K

1998-06-01

Leukotoxin and endotoxin derived from Pasteurella haemolytica serotype 1 are the primary virulence factors contributing to the pathogenesis of lung injury in bovine pneumonic pasteurellosis. Activation of bovine alveolar macrophages with endotoxin or leukotoxin results in the induction of cytokine gene expression, with different kinetics (H. S. Yoo, S. K. Maheswaran, G. Lin, E. L. Townsend, and T. R. Ames, Infect. Immun. 63:381-388, 1995; H. S. Yoo, B. S. Rajagopal, S. K. Maheswaran, and T. R. Ames, Microb. Pathog. 18:237-252, 1995). Furthermore, extracellular Ca2+ is required for leukotoxin-induced cytokine gene expression. However, the involvement of Ca2+ in endotoxin effects and the precise signaling mechanisms in the regulation of intracellular Ca2+ by leukotoxin and endotoxin are not known. In fura-2-acetoxymethyl ester-loaded alveolar macrophages, intracellular Ca2+ regulation by leukotoxin and endotoxin was studied by video fluorescence microscopy. Leukotoxin induced a sustained elevation of intracellular Ca2+ in a concentration-dependent fashion by influx of extracellular Ca2+ through voltage-gated channels. In the presence of fetal bovine serum, endotoxin elevated intracellular Ca2+ even in the absence of extracellular Ca2+. Leukotoxin-induced intracellular Ca2+ elevation was inhibited by pertussis toxin, inhibitors of phospholipases A2 and C, and the arachidonic acid analog 5,8,11,14-eicosatetraynoic acid. Intracellular Ca2+ elevation by endotoxin was inhibited by inhibitors of phospholipase C and protein tyrosine kinase, but not by pertussis toxin, or the arachidonic acid analog. To the best of our knowledge, this is the first report of Ca2+ signaling by leukotoxin through a G-protein-coupled mechanism involving activation of phospholipases A2 and C and release of arachidonic acid in bovine alveolar macrophages. Ca2+ signaling by endotoxin, on the other hand, involves activation of phospholipase C and requires tyrosine phosphorylation. The differences in the Ca2+ signaling mechanisms may underlie the reported temporal differences in gene expression during leukotoxin and endotoxin activation.

UV-emitting phosphors: synthesis, photoluminescence and applications

NASA Astrophysics Data System (ADS)

Thakare, D. S.; Omanwar, S. K.; Muthal, P. L.; Dhopte, S. M.; Kondawar, V. K.; Moharil, S. V.

2004-02-01

UV-emitting phosphors find uses in various applications, such as photocopying, phototherapy, sun tanning, etc. The phosphor requirements for these applications vary. Simple methods for preparing different UV-emitting phosphors are described. Novel syntheses for some borates (SrB4O7:Eu, CeMgB5O10:Gd, GdBO3:Pr, LaB3O6:Ce,Bi, LaB3O6:Gd,Bi, LaB3O6:Ce, Ba2B5O9Cl:Eu), a silicate (Ba2SiO5:Pb), phosphates (Sr2-xMgxP2O7:Eu) and a sulphate (CaSO4:Eu) are reported. Photoluminescence spectra of the phosphors so prepared are presented and discussed in the context of applications like phototherapy and photocopying lamps, photoluminescent liquid crystal displays, radiophotoluminescence, etc.

Investigation of cyano-bridged coordination nanoparticles Gd3+/[Fe(CN)6]3-/d-mannitol as T1-weighted MRI contrast agents

NASA Astrophysics Data System (ADS)

Perrier, M.; Gallud, A.; Ayadi, A.; Kennouche, S.; Porredon, C.; Gary-Bobo, M.; Larionova, J.; Goze-Bac, Ch.; Zanca, M.; Garcia, M.; Basile, I.; Long, J.; de Lapuente, J.; Borras, M.; Guari, Y.

2015-07-01

Cyano-bridged Gd3+/[Fe(CN)6]3- coordination polymer nanoparticles of 3-4 nm stabilized with d-mannitol presenting a high r1 relaxivity value of 11.4 mM-1 s-1 were investigated in vivo as contrast agents (CA) for Magnetic Resonance Imaging (MRI). They allow an increase of the MR image contrast and can act as an efficient intravascular T1 CA with a relatively long blood-circulation lifetime (60 min) without specific toxicity.Cyano-bridged Gd3+/[Fe(CN)6]3- coordination polymer nanoparticles of 3-4 nm stabilized with d-mannitol presenting a high r1 relaxivity value of 11.4 mM-1 s-1 were investigated in vivo as contrast agents (CA) for Magnetic Resonance Imaging (MRI). They allow an increase of the MR image contrast and can act as an efficient intravascular T1 CA with a relatively long blood-circulation lifetime (60 min) without specific toxicity. Electronic supplementary information (ESI) available: Experimental details and procedures, toxicological data, physical characterization. See DOI: 10.1039/c5nr01557j

Localization of intracellular and plasma membrane Ca2+-ATPases in the cerebellum.

PubMed

Sepúlveda, M Rosario; Mata, Ana M

2005-01-01

The sarco-endoplasmic reticulum Ca2+-ATPase and the plasma membrane Ca2+-ATPase contribute to the regulation of the intracellular Ca2+ concentration. These proteins transport Ca2+ ions into the endoplasmic reticulum and to the extracellular medium, respectively. A different localization of the two families of Ca2+-ATPases has been shown in concrete subcellular areas of Purkinje cells and in other neuronal elements from cerebellum. In the light of the actual knowledge of Ca2+-ATPases, this strict distribution suggests the existence of different demands on Ca2+ homeostasis in these cerebellar and cellular subregions.

Hyperforin stimulates intracellular calcium mobilisation and enhances extracellular acidification in DDT1-MF2 smooth muscle cells.

PubMed

Koch, E; Chatterjee, S S

2001-07-01

Hyperforin, an acylphloroglucinol derivative, is a major constituent of St. John's wort extract (Hypericum perforatum L.), which is used in treating depressive disorders. Hyperforin has been demonstrated as a modulator of several neuronal ion channels, and inhibits smooth-muscle contraction induced by various neurotransmitters. To evaluate the spasmolytic properties of hyperforin in more detail, we performed studies on the hamster vas deferens smooth muscle cell line DDT1-MF2. In a first series of experiments, we determined the effect of hyperforin on intracellular Ca2+ concentration ([Ca2+]i) using the fluorochrome fura-2. These investigations were supplemented in a second series of assays, where the effects on cellular metabolism were analysed by measuring the rate of extracellular release of acidic metabolites with the help of a microphysiometer. Hyperforin (0.3-10 microg/ml) caused a concentration-dependent elevation of [Ca2+]i and extracellular acidification rate (ECAR). Both of these effects were independent of extracellular Ca2+. To elucidate whether the increase of [Ca2+]i by hyperforin causes or results from its ECAR-stimulating properties, we used various pharmacological tools to reveal the sequence of events and the molecular mechanisms involved. Our results suggest that hyperforin induces release of Ca2+ from as yet unidentified sources. Since the ECAR stimulation was inhibited to a different extent by the intracellular Ca2+ chelator BAPTA as well as by inhibitors of plasmalemmal and mitochondrial Na+/Ca2+ exchange, but not by inhibitors of Na+/H+ antiport, the intracellular Ca2+ increase seems to be essential for this hyperforin effect. However, further studies are needed to establish the exact mode of action, and to deduce whether this aspect of hyperforin activity contributes to its antidepressant and neuroprotective effects.

Influence of Li+ charge compensator ion on the energy transfer from Pr3 + to Gd3 + ions in Ca9Mg(PO4)6F2:Gd3 +, Pr3 +, Li+ phosphor

NASA Astrophysics Data System (ADS)

Tamboli, Sumedha; Dhoble, S. J.

2017-09-01

Phototherapy is a renowned treatment for curing skin diseases since ancient times. Phototherapeutic treatment for psoriasis and many other diseases require narrow band ultra violet-B (NB-UVB) light with peak intensity at 313 nm to be exposed to the affected part of body. In this paper, we report combustion synthesis of NB-UVB - 313 nm emitting Ca9Mg(PO4)6F2 phosphors doped with Gd3 +, Pr3 + and Li+ ions. The phase formation was confirmed by obtaining X-ray diffraction (XRD) pattern and morphology was studied with the Scanning electron microscopy (SEM) images. Photoluminescence (PL) emission spectra show intense narrow band emission at 313 nm under 274 nm excitation wavelengths. Emission intensity was enhanced when Ca9Mg(PO4)6F2 compound is co-doped with Pr3 + ions. Excitation spectra of Ca9Mg(PO4)6F2:Gd3 +, Pr3 + doped samples shows broad excitation in ultra violet C (UVC) region. Diffuse reflectance spectra (DRS), obtained by UV-visible spectrophotometer, measures the absorption properties of the material. By applying Kubelka Munk function on the diffuse reflectance spectra, band gap of the material is determined. PL decay curves were examined which indicates efficient energy transfer between Pr3 + and Gd3 + ions. Charge compensation effect was also studied by co-doping Li+ ion in host. Emission intensity was found to increase with the addition of charge compensator. The prepared phosphor has potential to convert UVC light into NB-UVB. The luminescence intensity of Gd3 + shows remarkable increase when it is sensitized with Pr3 +, and an addition of charge compensator in the form of Li+, show even better results. This phosphor surely has the potential to be used as phototherapy lamp phosphor.

Thermodynamic stability, kinetic inertness and relaxometric properties of monoamide derivatives of lanthanide(III) DOTA complexes.

PubMed

Tei, Lorenzo; Baranyai, Zsolt; Gaino, Luca; Forgács, Attila; Vágner, Adrienn; Botta, Mauro

2015-03-28

A complete thermodynamic and kinetic solution study on lanthanide(III) complexes with monoacetamide (DOTAMA, L1) and monopropionamide (DOTAMAP, L2) derivatives of DOTA (DOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) was undertaken with the aim to elucidate their stability and inertness in aqueous media. The stability constants of GdL1 and GdL2 are comparable, whereas a more marked difference is found in the kinetic inertness of the two complexes. The formation of the Eu(III) and Ce(III) complexes takes place via the formation of the protonated intermediates which can deprotonate and transform into the final complex through a OH(-) assisted pathway. GdL2 shows faster rates of acid catalysed decomplexation with respect to GdL1, which has a kinetic inertness comparable to GdDOTA. Nevertheless, GdL2 is one order of magnitude more inert than GdDO3A. A novel DOTAMAP-based bifunctional chelating ligand and its deoxycholic acid derivative (L5) were also synthesized. Since the coordinated water molecule in GdL2 is characterized by an exchange rate ca. two orders of magnitude greater than in GdL1, the relaxivity of the macromolecular derivatives of L5 should not be limited by the slow water exchange process. The relaxometric properties of the supramolecular adduct of GdL5 with human serum albumin (HSA) were investigated in aqueous solution by measuring the magnetic field dependence of the (1)H relaxivity which, at 20 MHz and 298 K, shows a 430% increase over that of the unbound GdL5 chelate. Thus, Gd(III) complexes with DOTAMAP macrocyclic ligands can represent good candidates for the development of stable and highly effective bioconjugate systems for molecular imaging applications.

Calcium influx through L-type channels attenuates skeletal muscle contraction via inhibition of adenylyl cyclases.

PubMed

Menezes-Rodrigues, Francisco Sandro; Pires-Oliveira, Marcelo; Duarte, Thiago; Paredes-Gamero, Edgar Julian; Chiavegatti, Tiago; Godinho, Rosely Oliveira

2013-11-15

Skeletal muscle contraction is triggered by acetylcholine induced release of Ca(2+) from sarcoplasmic reticulum. Although this signaling pathway is independent of extracellular Ca(2+), L-type voltage-gated calcium channel (Cav) blockers have inotropic effects on frog skeletal muscles which occur by an unknown mechanism. Taking into account that skeletal muscle fiber expresses Ca(+2)-sensitive adenylyl cyclase (AC) isoforms and that cAMP is able to increase skeletal muscle contraction force, we investigated the role of Ca(2+) influx on mouse skeletal muscle contraction and the putative crosstalk between extracellular Ca(2+) and intracellular cAMP signaling pathways. The effects of Cav blockers (verapamil and nifedipine) and extracellular Ca(2+) chelator EGTA were evaluated on isometric contractility of mouse diaphragm muscle under direct electrical stimulus (supramaximal voltage, 2 ms, 0.1 Hz). Production of cAMP was evaluated by radiometric assay while Ca(2+) transients were assessed by confocal microscopy using L6 cells loaded with fluo-4/AM. Ca(2+) channel blockers verapamil and nifedipine had positive inotropic effect, which was mimicked by removal of extracellular Ca(+2) with EGTA or Ca(2+)-free Tyrode. While phosphodiesterase inhibitor IBMX potentiates verapamil positive inotropic effect, it was abolished by AC inhibitors SQ22536 and NYK80. Finally, the inotropic effect of verapamil was associated with increased intracellular cAMP content and mobilization of intracellular Ca(2+), indicating that positive inotropic effects of Ca(2+) blockers depend on cAMP formation. Together, our results show that extracellular Ca(2+) modulates skeletal muscle contraction, through inhibition of Ca(2+)-sensitive AC. The cross-talk between extracellular calcium and cAMP-dependent signaling pathways appears to regulate the extent of skeletal muscle contraction responses. © 2013 Published by Elsevier B.V.

Trapping effect on a small molecular drug with vascular-disrupting agent CA4P in rodent H22 hepatic tumor model: in vivo magnetic resonance imaging and postmortem inductively coupled plasma atomic emission spectroscopy.

PubMed

Gao, Meng; Yao, Nan; Huang, Dejian; Jiang, Cuihua; Feng, Yuanbo; Li, Yue; Lou, Bin; Peng, Fei; Sun, Ziping; Ni, Yicheng; Zhang, Jian

2015-06-01

The aim of the present study is to verify the trapping effect of combretastatin A-4-phosphate (CA4P) on small molecular drugs in rodent tumors. Mice with H22 hepatocarcinoma were randomized into groups A and B. Magnetic resonance imaging (MRI) of T1WI, T2WI, and DWI was performed as baseline. Mice in group A were injected with Gd-DTPA and PBS. Mice in group B were injected with Gd-DTPA and CA4P. All mice undergo CE-T1WI at 0 h, 3 h, 6 h, 12 h, and 24 h. Enhancing efficacy of the two groups on CE-T1WI was compared with the signal-to-noise ratio (SNR) calculated. Concentrations of gadolinium measured by ICP-AES in the tumor were compared between groups. On the early CE-T1WI, tumors were equally enhanced in both groups. On the delayed CE-T1WI, the enhancing effect of group A was weaker than that of group B. The SNR and the concentration of gadolinium within the tumor of group A were lower than that of group B at 6 h, 12 h, and 24 h after administration. This study indicates that CA4P could improve the retention of Gd-DTPA in the tumor and MRI allowed dynamically monitoring trapping effects of CA4P on local retention of Gd-DTPA as a small molecular drug.

Hypotonic shock stimulates ascorbate release from coronary artery endothelial cells by a Ca2+ -independent pathway.

PubMed

Davis, Kim A; Samson, Sue E; Wilson, John X; Grover, Ashok K

2006-10-24

In endothelial cells, anion channels open upon osmotic swelling during shear stress and hypotonic shock. Therefore, we examined the effects of hypotonic shock on release of the antioxidant anion ascorbate from pig coronary artery endothelial cells. Hypotonic shock potentiated ascorbate release from freshly isolated or cultured pig coronary artery endothelial cells; subsequently cultured endothelial cells were used. The hypotonic shock-induced increase in Asc release was rapid, depended on the degree of hypotonic shock, and not due to membrane leakiness. Stimulating P2Y2 like receptors in endothelial cells with ATP causes ascorbate release via a Ca2+ -mediated pathway. Hypotonic shock-induced release differed from the Ca2+-mediated Asc release because: (a) the increase in release with hypotonic shock was additive to that with ATP or A23187 (Ca2+ -ionophore), (b) apyrase, suramin or removing extracellular Ca2+ did not affect the hypotonic shock-stimulated release, (c) anion channel blockers inhibited the release by the two pathways differently, and (d) hypotonic shock increased the ascorbate release from endothelial cells and cultured smooth muscle cells whereas the Ca2+ -mediated ascorbate release occurred only in endothelial cells. Accumulation of ascorbate by endothelial cells was examined at extracellular ascorbate concentrations of 10 (Na+ -ascorbate symporter not saturated) and 5000 microM (Na+ -ascorbate symporter saturated). Hypotonic shock and A23187 decreased ascorbate accumulation at 10 microM ascorbate but increased it at 5000 microM. The effects of the two treatments were additive and also differed from each other with substitution of gluconate for extracellular chloride. Thus, ascorbate release from endothelial cells can be potentiated by two distinct pathways - hypotonic shock mediated and ATP/Ca2+ stimulated.

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

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

PubMed Central

Occhipinti, Rossana; Boron, Walter F.

2014-01-01

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

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.

Extraction of Structural Extracellular Polymeric Substances from Aerobic Granular Sludge

PubMed Central

Felz, Simon; Al-Zuhairy, Salah; Aarstad, Olav Andreas; van Loosdrecht, Mark C.M.; Lin, Yue Mei

2016-01-01

To evaluate and develop methodologies for the extraction of gel-forming extracellular polymeric substances (EPS), EPS from aerobic granular sludge (AGS) was extracted using six different methods (centrifugation, sonication, ethylenediaminetetraacetic acid (EDTA), formamide with sodium hydroxide (NaOH), formaldehyde with NaOH and sodium carbonate (Na2CO3) with heat and constant mixing). AGS was collected from a pilot wastewater treatment reactor. The ionic gel-forming property of the extracted EPS of the six different extraction methods was tested with calcium ions (Ca2+). From the six extraction methods used, only the Na2CO3 extraction could solubilize the hydrogel matrix of AGS. The alginate-like extracellular polymers (ALE) recovered with this method formed ionic gel beads with Ca2+. The Ca2+-ALE beads were stable in EDTA, formamide with NaOH and formaldehyde with NaOH, indicating that ALE are one part of the structural polymers in EPS. It is recommended to use an extraction method that combines physical and chemical treatment to solubilize AGS and extract structural EPS. PMID:27768085

Hyperforin activates nonselective cation channels (NSCCs).

PubMed

Treiber, Kristina; Singer, Andrea; Henke, Bettina; Müller, Walter E

2005-05-01

A large body of evidence supports the preclinical antidepressant profile of hyperforin including inhibition of the synaptosomal uptake of several neurotransmitters by hyperforin and studies in behavioural models. In contrast to other antidepressants, hyperforin does not directly inhibit neurotransmitter transporters, but instead uptake inhibition seems to be the consequence of an elevated intracellular sodium concentration ([Na+]i). The mechanism of hyperforin-induced elevation of [Na+]i was investigated using two different cell types: human platelets and rat pheochromocytoma cells (PC12 cells). In both cell systems, hyperforin increased both [Na+]i and free intracellular Ca2+ concentration ([Ca2+]i). One pathway for Na+ and Ca2+ entry is mediated by nonselective cation channels (NSCCs), which can be blocked by SK&F 96365 and LOE 908. LOE 908 is a blocker of both NSCC1 and NSCC2 subclasses, while SK&F 96365 blocks NSCC2 only. Both SK&F 96365 and LOE 908 completely inhibited the hyperforin-induced influx of Na+ and Ca2+ into platelets and PC12 cells. This indicates that hyperforin is mainly active upon NSCC2. The effect of hyperforin is inhibited by La3+ and Gd3+, indicating that there is a potential homology with canonical transient receptor potential protein channels (TRPC channels). Moreover, La3+ and Gd3+ attenuate the effect of hyperforin on serotonin uptake in human platelets. Additionally, hyperforin induces barium influx in PC12 cells and this influx can be inhibited by SK&F 96365, LOE 908, Gd3+ and La3+. In summary, these findings suggest that hyperforin represents a new principle for preclinical antidepressant activity, modulating brain neurotransmission by inhibition of neurotransmitter uptake via activation of NSCCs.British Journal of Pharmacology (2005) 145, 75-83. doi:10.1038/sj.bjp.0706155.

Hyperforin activates nonselective cation channels (NSCCs)

PubMed Central

Treiber, Kristina; Singer, Andrea; Henke, Bettina; Müller, Walter E

2005-01-01

A large body of evidence supports the preclinical antidepressant profile of hyperforin including inhibition of the synaptosomal uptake of several neurotransmitters by hyperforin and studies in behavioural models. In contrast to other antidepressants, hyperforin does not directly inhibit neurotransmitter transporters, but instead uptake inhibition seems to be the consequence of an elevated intracellular sodium concentration ([Na+]i). The mechanism of hyperforin-induced elevation of [Na+]i was investigated using two different cell types: human platelets and rat pheochromocytoma cells (PC12 cells). In both cell systems, hyperforin increased both [Na+]i and free intracellular Ca2+ concentration ([Ca2+]i). One pathway for Na+ and Ca2+ entry is mediated by nonselective cation channels (NSCCs), which can be blocked by SK&F 96365 and LOE 908. LOE 908 is a blocker of both NSCC1 and NSCC2 subclasses, while SK&F 96365 blocks NSCC2 only. Both SK&F 96365 and LOE 908 completely inhibited the hyperforin-induced influx of Na+ and Ca2+ into platelets and PC12 cells. This indicates that hyperforin is mainly active upon NSCC2. The effect of hyperforin is inhibited by La3+ and Gd3+, indicating that there is a potential homology with canonical transient receptor potential protein channels (TRPC channels). Moreover, La3+ and Gd3+ attenuate the effect of hyperforin on serotonin uptake in human platelets. Additionally, hyperforin induces barium influx in PC12 cells and this influx can be inhibited by SK&F 96365, LOE 908, Gd3+ and La3+. In summary, these findings suggest that hyperforin represents a new principle for preclinical antidepressant activity, modulating brain neurotransmission by inhibition of neurotransmitter uptake via activation of NSCCs. PMID:15723093

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

PubMed

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

2015-09-01

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

The role of extracellular calcium in corticotropin-stimulated steroidogenesis.

PubMed

Cheitlin, R; Buckley, D I; Ramachandran, J

1985-05-10

The role of extracellular Ca2+ in the binding of corticotropin (ACTH) to adrenocortical cell receptors as well as in the post-binding events involved in steroidogenesis were investigated. Binding studies using [125I-Tyr23,Phe2,Nle4]ACTH (1-38) peptide showed that extracellular Ca2+ is essential not only for the interaction of ACTH with its receptor, but also for continued occupancy of the receptor. In view of the requirement of Ca2+ for binding the hormone to the receptor, the role of Ca2+ in post-receptor events was investigated by covalently attaching the hormone to its receptor by photoaffinity labeling in the presence of Ca2+. Persistent activation of steroidogenesis induced by photoaffinity labeling in the presence of Ca2+ was depressed when cells were incubated in medium containing EGTA but was unaffected when the cells were merely washed and incubated in Ca2+-free medium. In the presence of EGTA, 8-Br-cAMP partially restored persistent activation of steroidogenesis. The concentration of extracellular Ca2+ required for restoring steroidogenesis was 10-fold lower than the concentration of Ca2+ needed for optimal binding of ACTH to its receptor. These results suggest that the primary role of extracellular Ca2+ in the action of ACTH is to facilitate the association of the hormone with its receptor.

Influence of calcium and phosphorus feeding on markers of bone metabolism in transition cows.

PubMed

Moreira, V R; Zeringue, L K; Williams, C C; Leonardi, C; McCormick, M E

2009-10-01

A study was carried out to verify the effect of Ca and P levels on production, digestibility, and serum bone metabolism biomarkers in dairy cows. Fifty-two nonlactating multiparous cows (>or=3 lactations) were confined in a free-stall barn approximately 20 d before calving. A standard close-up diet was fed to cows once daily until d 2 postpartum. Cows were randomly assigned to 1 of 4 dietary treatments arranged in a 2 x 2 factorial approach averaging 0.64% Ca for high Ca (HCa), 0.46% Ca for low Ca (LCa), 0.47% P for high P (HP), and 0.38% P for low P (LP) on a dry matter basis. Experimental diets were fed twice daily from 3 d in milk (DIM) until 31 DIM. Intake and milk yield were recorded daily. Milk samples were collected on d 28, 29, and 30 postpartum for components analyses. Blood samples were drawn 10 d before expected calving, at calving, and at 15 and 30 DIM for serum analyses of osteocalcin, a biomarker of bone accretion, and pyridinoline, a biomarker of bone resorption. Total fecal collection was conducted when cows in a block averaged 20 DIM. Intake and production traits were not significantly affected by any of the dietary treatments. Cows averaged nearly 21 kg/d dry matter intake and 44 kg/d milk yield from 6 to 31 DIM. There were no significant differences across treatments in body weight or body condition score loss. Phosphorus intake, P fecal output, P digestibility, and P apparent absorption were affected by dietary P content. Calcium intake was higher with HCa, but Ca fecal output, digestibility, and apparent absorption showed an interaction between dietary Ca and dietary P. Calcium fecal output was 100.6 g/d for cows fed HCaHP, intermediate for cows on the HCaLP diet (89 g/d), and similar among cows fed the 2 LCa diets (70 g/d with LCaHP and 75 with LCaLP). There was no significant effect of Ca or P on osteocalcin measurements. Pyridinoline concentrations were affected by dietary Ca levels and tended to have a significant dietary Ca x dietary P interaction. Phosphorus apparent digestibility occurred independently of dietary Ca levels. Results of this study suggest that more bone was mobilized in cows fed LCa diets, but excess dietary P caused greater and prolonged bone mobilization regardless of dietary Ca content.

Drawing entitled "Planting Plan Pine Hills, Gd. Sta. U.S. Department ...

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

Drawing entitled "Planting Plan Pine Hills, Gd. Sta. U.S. Department of Agriculture, Forest Service, Region 5. L. Glenn Hall, landscape engineer. 11-5-35. - Pine Hills Station, Barracks, West Side of Boulder Creek Road at Engineers Road, Julian, San Diego County, CA

Extracellular calcium sensing and extracellular calcium signaling

NASA Technical Reports Server (NTRS)

Brown, E. M.; MacLeod, R. J.; O'Malley, B. W. (Principal Investigator)

2001-01-01

The cloning of a G protein-coupled extracellular Ca(2+) (Ca(o)(2+))-sensing receptor (CaR) has elucidated the molecular basis for many of the previously recognized effects of Ca(o)(2+) on tissues that maintain systemic Ca(o)(2+) homeostasis, especially parathyroid chief cells and several cells in the kidney. The availability of the cloned CaR enabled the development of DNA and antibody probes for identifying the CaR's mRNA and protein, respectively, within these and other tissues. It also permitted the identification of human diseases resulting from inactivating or activating mutations of the CaR gene and the subsequent generation of mice with targeted disruption of the CaR gene. The characteristic alterations in parathyroid and renal function in these patients and in the mice with "knockout" of the CaR gene have provided valuable information on the CaR's physiological roles in these tissues participating in mineral ion homeostasis. Nevertheless, relatively little is known about how the CaR regulates other tissues involved in systemic Ca(o)(2+) homeostasis, particularly bone and intestine. Moreover, there is evidence that additional Ca(o)(2+) sensors may exist in bone cells that mediate some or even all of the known effects of Ca(o)(2+) on these cells. Even more remains to be learned about the CaR's function in the rapidly growing list of cells that express it but are uninvolved in systemic Ca(o)(2+) metabolism. Available data suggest that the receptor serves numerous roles outside of systemic mineral ion homeostasis, ranging from the regulation of hormonal secretion and the activities of various ion channels to the longer term control of gene expression, programmed cell death (apoptosis), and cellular proliferation. In some cases, the CaR on these "nonhomeostatic" cells responds to local changes in Ca(o)(2+) taking place within compartments of the extracellular fluid (ECF) that communicate with the outside environment (e.g., the gastrointestinal tract). In others, localized changes in Ca(o)(2+) within the ECF can originate from several mechanisms, including fluxes of calcium ions into or out of cellular or extracellular stores or across epithelium that absorb or secrete Ca(2+). In any event, the CaR and other receptors/sensors for Ca(o)(2+) and probably for other extracellular ions represent versatile regulators of numerous cellular functions and may serve as important therapeutic targets.

Influx of extracellular Zn(2+) into the hippocampal CA1 neurons is required for cognitive performance via long-term potentiation.

PubMed

Takeda, A; Suzuki, M; Tempaku, M; Ohashi, K; Tamano, H

2015-09-24

Physiological significance of synaptic Zn(2+) signaling was examined in the CA1 of young rats. In vivo CA1 long-term potentiation (LTP) was induced using a recording electrode attached to a microdialysis probe and the recording region was locally perfused with artificial cerebrospinal fluid (ACSF) via the microdialysis probe. In vivo CA1 LTP was inhibited under perfusion with CaEDTA and ZnAF-2DA, extracellular and intracellular Zn(2+) chelators, respectively, suggesting that the influx of extracellular Zn(2+) is required for in vivo CA1 LTP induction. The increase in intracellular Zn(2+) was chelated with intracellular ZnAF-2 in the CA1 1h after local injection of ZnAF-2DA into the CA1, suggesting that intracellular Zn(2+) signaling induced during learning is blocked with intracellular ZnAF-2 when the learning was performed 1h after ZnAF-2DA injection. Object recognition was affected when training of object recognition test was performed 1h after ZnAF-2DA injection. These data suggest that intracellular Zn(2+) signaling in the CA1 is required for object recognition memory via LTP. Surprisingly, in vivo CA1 LTP was affected under perfusion with 0.1-1μM ZnCl2, unlike the previous data that in vitro CA1 LTP was enhanced in the presence of 1-5μM ZnCl2. The influx of extracellular Zn(2+) into CA1 pyramidal cells has bidirectional action in CA1 LTP. The present study indicates that the degree of extracellular Zn(2+) influx into CA1 neurons is critical for LTP and cognitive performance. Copyright © 2015 IBRO. Published by Elsevier Ltd. All rights reserved.

β adrenergic receptor/cAMP/PKA signaling contributes to the intracellular Ca2+ release by tentacle extract from the jellyfish Cyanea capillata.

PubMed

Wang, Qianqian; Zhang, Hui; Wang, Bo; Wang, Chao; Xiao, Liang; Zhang, Liming

2017-07-25

Intracellular Ca 2+ overload induced by extracellular Ca 2+ entry has previously been confirmed to be an important mechanism for the cardiotoxicity as well as the acute heart dysfunction induced by jellyfish venom, while the underlying mechanism remains to be elucidated. Under extracellular Ca 2+ -free or Ca 2+ -containing conditions, the Ca 2+ fluorescence in isolated adult mouse cardiomyocytes pre-incubated with tentacle extract (TE) from the jellyfish Cyanea capillata and β blockers was scanned by laser scanning confocal microscope. Then, the cyclic adenosine monophosphate (cAMP) concentration and protein kinase A (PKA) activity in primary neonatal rat ventricular cardiomyocytes were determined by ELISA assay. Furthermore, the effect of propranolol against the cardiotoxicity of TE was evaluated in Langendorff-perfused rat hearts and intact rats. The increase of intracellular Ca 2+ fluorescence signal by TE was significantly attenuated and delayed when the extracellular Ca 2+ was removed. The β adrenergic blockers, including propranolol, atenolol and esmolol, partially inhibited the increase of intracellular Ca 2+ in the presence of 1.8 mM extracellular Ca 2+ and completely abolished the Ca 2+ increase under an extracellular Ca 2+ -free condition. Both cAMP concentration and PKA activity were stimulated by TE, and were inhibited by the β adrenergic blockers. Cardiomyocyte toxicity of TE was antagonized by β adrenergic blockers and the PKA inhibitor H89. Finally, the acute heart dysfuction by TE was antagonized by propranolol in Langendorff-perfused rat hearts and intact rats. Our findings indicate that β adrenergic receptor/cAMP/PKA signaling contributes to the intracellular Ca 2+ overload through intracellular Ca 2+ release by TE from the jellyfish C. capillata.

Calcium dependence of eugenol tolerance and toxicity in Saccharomyces cerevisiae.

PubMed

Roberts, Stephen K; McAinsh, Martin; Cantopher, Hanna; Sandison, Sean

2014-01-01

Eugenol is a plant-derived phenolic compound which has recognised therapeutical potential as an antifungal agent. However little is known of either its fungicidal activity or the mechanisms employed by fungi to tolerate eugenol toxicity. A better exploitation of eugenol as a therapeutic agent will therefore depend on addressing this knowledge gap. Eugenol initiates increases in cytosolic Ca2+ in Saccharomyces cerevisiae which is partly dependent on the plasma membrane calcium channel, Cch1p. However, it is unclear whether a toxic cytosolic Ca2+elevation mediates the fungicidal activity of eugenol. In the present study, no significant difference in yeast survival was observed following transient eugenol treatment in the presence or absence of extracellular Ca2+. Furthermore, using yeast expressing apoaequorin to report cytosolic Ca2+ and a range of eugenol derivatives, antifungal activity did not appear to be coupled to Ca2+ influx or cytosolic Ca2+ elevation. Taken together, these results suggest that eugenol toxicity is not dependent on a toxic influx of Ca2+. In contrast, careful control of extracellular Ca2+ (using EGTA or BAPTA) revealed that tolerance of yeast to eugenol depended on Ca2+ influx via Cch1p. These findings expose significant differences between the antifungal activity of eugenol and that of azoles, amiodarone and carvacrol. This study highlights the potential to use eugenol in combination with other antifungal agents that exhibit differing modes of action as antifungal agents to combat drug resistant infections.

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

PubMed Central

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

2015-01-01

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

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

Quantitative Visualization of Dynamic Tracer Transportation in the Extracellular Space of Deep Brain Regions Using Tracer-Based Magnetic Resonance Imaging.

PubMed

Hou, Jin; Wang, Wei; Quan, Xianyue; Liang, Wen; Li, Zhiming; Chen, Deji; Han, Hongbin

2017-09-03

BACKGROUND This study assessed an innovative tracer-based magnetic resonance imaging (MRI) system to visualize the dynamic transportation of tracers in regions of deep brain extracellular space (ECS) and to measure transportation ability and ECS structure. MATERIAL AND METHODS Gadolinium-diethylene triamine pentaacetic acid (Gd-DTPA) was the chosen tracer and was injected into the caudate nucleus and thalamus. Real-time dynamic transportation of Gd-DTPA in ECS was observed and the results were verified by laser scanning confocal microscopy. Using Transwell assay across the blood-brain barrier, a modified diffusion equation was further simplified. Effective diffusion coefficient D* and tortuosity λ were calculated. Immunohistochemical staining and Western blot analysis were used to investigate the extracellular matrix contributing to ECS structure. RESULTS Tracers injected into the caudate nucleus were transported to the ipsilateral frontal and temporal cortices away from the injection points, while both of them injected into the thalamus were only distributed on site. Although the caudate nucleus was closely adjacent to the thalamus, tracer transportation between partitions was not observed. In addition, D* and the λ showed statistically significant differences between partitions. ECS was shown to be a physiologically partitioned system, and its division is characterized by the unique distribution territory and transportation ability of substances located in it. Versican and Tenascin R are possible contributors to the tortuosity of ECS. CONCLUSIONS Tracer-based MRI will improve our understanding of the brain microenvironment, improve the techniques for local delivery of drugs, and highlight brain tissue engineering fields in the future.

In Vitro Longitudinal Relaxivity Profile of Gd(ABE-DTTA), an Investigational Magnetic Resonance Imaging Contrast Agent

PubMed Central

Varga-Szemes, Akos; Kiss, Pal; Rab, Andras; Suranyi, Pal; Lenkey, Zsofia; Simor, Tamas; Bryant, Robert G.; Elgavish, Gabriel A.

2016-01-01

Purpose MRI contrast agents (CA) whose contrast enhancement remains relatively high even at the higher end of the magnetic field strength range would be desirable. The purpose of this work was to demonstrate such a desired magnetic field dependency of the longitudinal relaxivity for an experimental MRI CA, Gd(ABE-DTTA). Materials and Methods The relaxivity of 0.5mM and 1mM Gd(ABE-DTTA) was measured by Nuclear Magnetic Relaxation Dispersion (NMRD) in the range of 0.0002 to 1T. Two MRI and five NMR instruments were used to cover the range between 1.5 to 20T. Parallel measurement of a Gd-DTPA sample was performed throughout as reference. All measurements were carried out at 37°C and pH 7.4. Results The relaxivity values of 0.5mM and 1mM Gd(ABE-DTTA) measured at 1.5, 3, and 7T, within the presently clinically relevant magnetic field range, were 15.3, 11.8, 12.4 s-1mM-1 and 18.1, 16.7, and 13.5 s-1mM-1, respectively. The control 4 mM Gd-DTPA relaxivities at the same magnetic fields were 3.6, 3.3, and 3.0 s-1mM-1, respectively. Conclusions The longitudinal relaxivity of Gd(ABE-DTTA) measured within the presently clinically relevant field range is three to five times higher than that of most commercially available agents. Thus, Gd(ABE-DTTA) could be a practical choice at any field strength currently used in clinical imaging including those at the higher end. PMID:26872055

Osteogenic differentiation capacity of human mesenchymal stromal cells in response to extracellular calcium with special regard to connexin 43.

PubMed

Wagner, Alena-Svenja; Glenske, Kristina; Wolf, Verena; Fietz, Daniela; Mazurek, Sybille; Hanke, Thomas; Moritz, Andreas; Arnhold, Stefan; Wenisch, Sabine

2017-01-01

The effects of extracellular calcium on osteogenic differentiation capacity of human bone-derived mesenchymal stromal cells with special regard to connexin 43 (cx43) have been investigated by means of cell culture experiments. Mesenchymal stromal cells isolated from human cancellous bone were cultured on tissue culture plates at different calcium ion (Ca 2+ ) concentrations (1.8mmoll -1 , 10mmoll -1 , 20mmoll -1 ). Cell responses were evaluated by quantitative RT-PCR, immunofluorescence staining, and Lucifer Yellow fluorescence uptake experiments. It could be shown that increasing Ca 2+ concentrations correlate with increasing cx43 and bone sialoprotein mRNA levels as well as with enhanced cx43 fluorescence signaling and matrix mineralization of the cultures as shown by von Kossa staining. Hemichannel gating - assessed by Lucifer Yellow uptake - increases with increasing extracellular Ca 2+ concentrations suggesting that regulatory effects at the hemichannel level are calcium-dependent. Copyright © 2016 Elsevier GmbH. All rights reserved.

Extracellular Ca2+ Is Required for Fertilization in the African Clawed Frog, Xenopus laevis

PubMed Central

Duray, Alexis M.; Tembo, Maiwase; Beleny, David O.; Napolitano, Marc A.; Sauer, Monica L.; Wisner, Bennett W.

2017-01-01

Background The necessity of extracellular Ca2+ for fertilization and early embryonic development in the African clawed frog, Xenopus laevis, is controversial. Ca2+ entry into X. laevis sperm is reportedly required for the acrosome reaction, yet fertilization and embryonic development have been documented to occur in high concentrations of the Ca2+ chelator BAPTA. Here we sought to resolve this controversy. Methodology/principal finding Using the appearance of cleavage furrows as an indicator of embryonic development, we found that X. laevis eggs inseminated in a solution lacking added divalent cations developed normally. By contrast, eggs inseminated in millimolar concentrations of BAPTA or EGTA failed to develop. Transferring embryos to varying solutions after sperm addition, we found that extracellular Ca2+ is specifically required for events occurring within the first 30 minutes after sperm addition, but not after. We found that the fluorescently stained sperm were not able to penetrate the envelope of eggs inseminated in high BAPTA, whereas several had penetrated the vitelline envelope of eggs inseminated without a Ca2+ chelator, or with BAPTA and saturating CaCl2. Together these results indicate that fertilization does not occur in high concentrations of Ca2+ chelators. Finally, we found that the jelly coat includes >5 mM of readily diffusible Ca2+. Conclusions/Significance Taken together, these data are consistent with requirement of extracellular Ca2+ for fertilization. Based on our findings, we hypothesize that the jelly coat surrounding the egg acts as a reserve of readily available Ca2+ ions to foster fertilization in changing extracellular milieu. PMID:28114360

Delayed gadolinium-enhanced MRI of the fibrocartilage disc of the temporomandibular joint – a feasibility study

PubMed Central

Pittschieler, Elisabeth; Szomolanyi, Pavol; Schmid-Schwap, Martina; Weber, Michael; Egerbacher, Monika; Traxler, Hannes; Trattnig, Siegfried

2014-01-01

Objective To 1) test the feasibility of delayed Gadolinium-Enhanced Magnetic Resonance Imaging of Cartilage (dGEMRIC) at 3 T in the temporomandibular joint (TMJ) and 2) to determine the optimal delay for measurements of the TMJ disc after i.v. contrast agent (CA) administration. Design MRI of the right and left TMJ of six asymptomatic volunteers was performed at 3 T using a dedicated coil. 2D inversion recovery (2D-IR) sequences were performed at 4 time points covering 120 minutes and 3D gradient-echo (3D GRE) dual flip-angle sequences were performed at 14 time points covering 130 minutes after the administration of 0.2 mmol/kg of Gd-diethylenetriamine pentaacetic acid ion (Gd-DTPA)2-, i.e., 0.4 mL of Magnevist™ per kg body weight. Pair-wise tests were used to assess differences between pre-and post-contrast T1 values. Results 2D-IR sequences showed a statistically significant drop (p < 0.001) in T1 values after i.v. CA administration. The T1 drop of 50% was reached 60 minutes after bolus injection in the TMJ disc. The 3D GRE dual flip-angle sequences confirmed these results and show plateau of T1 after 60 minutes. Conclusions T1(Gd) maps calculated from dGEMRIC data allow in vivo assessment of the fibrocartilage disc of the TMJ. The recommended measurement time for dGEMRIC in the TMJ after i.v. CA administration is from 60 to 120 minutes. PMID:25131629

Delayed gadolinium-enhanced MRI of the fibrocartilage disc of the temporomandibular joint--a feasibility study.

PubMed

Pittschieler, Elisabeth; Szomolanyi, Pavol; Schmid-Schwap, Martina; Weber, Michael; Egerbacher, Monika; Traxler, Hannes; Trattnig, Siegfried

2014-12-01

To 1) test the feasibility of delayed Gadolinium-Enhanced Magnetic Resonance Imaging of Cartilage (dGEMRIC) at 3 T in the temporomandibular joint (TMJ) and 2) to determine the optimal delay for measurements of the TMJ disc after i.v. contrast agent (CA) administration. MRI of the right and left TMJ of six asymptomatic volunteers was performed at 3 T using a dedicated coil. 2D inversion recovery (2D-IR) sequences were performed at 4 time points covering 120 minutes and 3D gradient-echo (3D GRE) dual flip-angle sequences were performed at 14 time points covering 130 minutes after the administration of 0.2 mmol/kg of Gd-diethylenetriamine pentaacetic acid ion (Gd-DTPA)(2-), i.e., 0.4 mL of Magnevist™ per kg body weight. Pair-wise tests were used to assess differences between pre-and post-contrast T1 values. 2D-IR sequences showed a statistically significant drop (p<0.001) in T1 values after i.v. CA administration. The T1 drop of 50% was reached 60 minutes after bolus injection in the TMJ disc. The 3D GRE dual flip-angle sequences confirmed these results and show plateau of T1 after 60 minutes. T1(Gd) maps calculated from dGEMRIC data allow in vivo assessment of the fibrocartilage disc of the TMJ. The recommended measurement time for dGEMRIC in the TMJ after i.v. CA administration is from 60 to 120 minutes. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

Regulation of axonal and dendritic growth by the extracellular calcium-sensing receptor (CaSR)

PubMed Central

Vizard, Thomas N.; O'Keeffe, Gerard W.; Gutierrez, Humberto; Kos, Claudine H.; Riccardi, Daniela; Davies, Alun M.

2009-01-01

The extracellular calcium-sensing receptor (CaSR) monitors the systemic extracellular free ionized calcium level ([Ca2+]o) in organs involved in systemic [Ca2+]o homeostasis. However, the CaSR is also expressed in the nervous system where its role is unknown. Here we find high levels of the CaSR in perinatal mouse sympathetic neurons when their axons are innervating and branching extensively in their targets. Manipulating CaSR function in these neurons by varying [Ca2+]o, using CaSR agonists and antagonists or expressing a dominant-negative CaSR markedly affects neurite growth in vitro Sympathetic neurons lacking the CaSR have smaller neurite arbors in vitro, and sympathetic innervation density is reduced in CaSR-deficient mice in vivo. Hippocampal pyramidal neurons, which also express the CaSR, have smaller dendrites when transfected with dominant-negative CaSR in postnatal organotypic cultures. Our findings reveal a crucial role for the CaSR in regulating the growth of neural processes in the peripheral and central nervous systems. PMID:18223649

Biologically-compatible gadolinium(at)(carbon nanostructures) as advanced contrast agents for magnetic resonance imaging

NASA Astrophysics Data System (ADS)

Sitharaman, Balaji

2005-11-01

Paramagnetic gadolinium-based carbon nanostructures are introduced as a new paradigm in high-performance magnetic resonance imaging (MRI) contrast agent (CA) design. Two Gd C60-based nanomaterials, Gd C60 [C(COOH)2]10 and Gd C60(OH)x are shown to have MRI efficacies (relaxivities) 5 to 20 times larger than any current Gd3+-based CA in clinical use. The first detailed and systematic physicochemical characterization was performed on these materials using the same experimental techniques usually applied to traditional Gd 3+-based CAs. Water-proton relaxivities were measured for the first time on these materials, as a function of magnetic field (5 x 10-4--9.4 T) to elucidate the different interaction mechanisms and dynamic processes influencing the relaxation behavior. These studies attribute the observed enhanced relaxivities completely to the "outer sphere" proton relaxation mechanism. These "outer sphere" relaxation effects are the largest reported for any Gd3+-based agent without inner-sphere water molecules. The proton relaxivities displayed a remarkable pH-dependency, increasing dramatically with decreasing pH (pH: 3--12). The increase in relaxivity resulted mainly from aggregation and subsequent three-order-of-magnitude increase in tauR, the rotational correlation time. Water-soluble fullerene materials (such as the neuroprotective fullerene drug, C3) readily cross cell membranes, suggesting an application for these gadofullerenes as the first intracellular, as well as pH-responsive MRI CAs. Studies performed at 60 MHz in the presence of phosphate-buffered saline (PBS, mice serum pH: 7.4) to mimic physiological conditions demonstrated that the aggregates can be disrupted by addition of salts, leading to a decrease in relaxivity. Biological fluids present a high salt concentration and should strongly modify the behavior of any fullerenes/metallofullerene-based drug in vivo. Gd C60[C(COOH)2]10 also showed enhanced relaxivity (23% increase) in the presence of the blood protein, human serum albumin (HSA). This result suggests a strong non-covalent interaction between Gd C60[C(COOH)2]10 and HSA leading to slower rotation and a subsequent increase in relaxivity. This also suggests Gd C 60[C(COOH)2]10 as a promising candidate for non-invasive MR angiographic applications to image the "blood pool." Finally, the various important factors or parameters discussed in this work provide valuable insight that can, in general, be used not only for the development of other carbon nanostructure-based MRI contrast agents, but also for any fullerene-based biomedical application.

Effects of prepartum dietary calcium level on calcium and magnesium metabolism in periparturient dairy cows.

PubMed

Kronqvist, C; Emanuelson, U; Spörndly, R; Holtenius, K

2011-03-01

The aim of this study was to investigate the effects of dietary Ca level (4.9, 9.3, and 13.6 g/kg of DM) on Ca and Mg homeostasis in dairy cows around parturition. Cows of the Swedish Red breed (n = 29) with no previous veterinary treatment for milk fever were divided into 3 groups, and each group was fed one of the different diets during the last 15 to 32 d of gestation. Calcium was added as ground limestone, and the Mg concentration was 1.8 g/kg of DM in all diets. After calving the cows were fed similar diets. Plasma was sampled twice per week until calving, and 6, 12, and 24 h, 2, 4, and 7 d after calving. Spot urine samples were collected twice weekly until calving and creatinine was used as a marker of daily urinary excretion. Fecal samples were collected 2 times per day for 5 d starting 2 wk before expected calving, and acid-insoluble ash was used as an indigestible marker to estimate digestibility. Apparent digestibility of Mg and daily Mg excretion in the urine were lower in the dry period for cows fed the highest Ca level. Plasma Mg concentration was lower on 2, 4, and 7 d after calving in cows fed the highest level of Ca. Treatment groups did not differ in plasma Ca concentration, parathyroid hormone concentration, or bone mobilization, evaluated using crosslinked carboxyterminal telopeptides of type I collagen (CTx) as a marker. Plasma Ca concentration decreased and plasma CTx concentration increased 6 h after calving. The apparent digestibility of Ca during the dry period was not affected by dietary Ca, but the cows fed 4.9 g Ca/kg of DM excreted 1.2 g of Ca/d in the urine, which was higher compared with 0.4 g/d and 0.6 g/d for the cows fed 9.3 g of Ca/kg of DM and 13.6 g of Ca/kg of DM, respectively. The results show that feeding 13.6 g of dietary Ca/kg of DM impaired the Mg absorption during the dry period, and resulted in decreased plasma Mg concentration after calving, but prepartum dietary Ca level did not affect plasma Ca, parathyroid hormone, or CTx concentrations. Copyright © 2011 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

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

[Effects of neuroactive substances on intracellular free Ca2+ concentration in isolated outer hair cells of the guinea pig cochlea].

PubMed

Yang, J; Wang, J; Wei, S

1998-10-01

To measure the effects of neuro-active substances on intracellular free Ca2+ concentration ([Ca2+]i) in isolated outer hair cells(OHCs) of the guinea pig cochlea. The fura-2 microfluorimetry was used to measure changes of [Ca2+]i in OHCs of the guinea pig cochlea after application of acetylcholine, ATP and carbacholine. Acetylcholine, ATP and carbacholine increased [Ca2+]i (acetylcholine: 0.74 +/- 0.12 mumol/L, ATP: 0.65 +/- 0.11 mumol/L, carbacholine: 1.16 +/- 0.27 mumol/L) in OHCs in the presence of extracellular Ca2+. In the absence of extracellular Ca2+, however, only ATP induced a gradual and small [Ca2+]i elevation, whereas other substances did not. Acetylcholine and carbacholine, the cholinergic mascarinic agonists, increased [Ca2+]i in OHCs by acting at receptor-induced ion channel resulting in Ca2+ efflux. ATP-induced elevation of [Ca2+]i without Ca2+ in extracellular medium is due to a release of Ca2+ from an intracellular reservoir.

Mapping of native inorganic elements and injected nanoparticles in a biological organ with laser-induced plasma

NASA Astrophysics Data System (ADS)

Motto-Ros, V.; Sancey, L.; Ma, Q. L.; Lux, F.; Bai, X. S.; Wang, X. C.; Yu, Jin; Panczer, G.; Tillement, O.

2012-11-01

Emission spectroscopy of laser-induced plasma from a thin section of mouse kidney successfully detected inorganic elements, Na, Ca, Cu, and Gd, naturally contained in the organ or artificially injected in the form of Gd-based nanoparticle. A two-dimensional scan of the sample allowed the laser beam to explore its surface with a resolution of 100 μm, resulting in a quantitative elemental mapping of the organ with sub-mM sensitivity. The compatibility of the setup with standard optical microscopy emphasizes the potential to provide multiple images of a same biological tissue with different types of response which can be elemental, molecular, or cellular.

In vivo EPR extracellular pH-metry in tumors using a triphosphonated trityl radical.

PubMed

Marchand, Valérie; Levêque, Philippe; Driesschaert, Benoit; Marchand-Brynaert, Jacqueline; Gallez, Bernard

2017-06-01

The ability to assess the extracellular pH (pHe) is an important issue in oncology, because extracellular acidification is associated with tumor aggressiveness and resistance to cytotoxic therapies. In this study, a stable triphosphonated triarylmethyl (TPTAM) radical was qualified as a pHe electron paramagnetic resonance (EPR) molecular reporter. Calibration of hyperfine splitting as a function of pH was performed using a 1.2-GHz EPR spectrometer. Gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) was used as an extracellular paramagnetic broadening agent to assess the localization of TPTAM when incubated with cells. In vivo EPR pH-metry was performed in MDA, SiHa, and TLT tumor models and in muscle. Bicarbonate therapy was used to modulate the tumor pHe. EPR measurements were compared with microelectrode readouts. The hyperfine splitting of TPTAM was strongly pH-dependent around the pKa of the probe (pKa = 6.99). Experiments with Gd-DTPA demonstrated that TPTAM remained in the extracellular compartment. pHe was found to be more acidic in the MDA, SiHa, and TLT tumor models compared with muscle. Treatment of animals by bicarbonate induced an increase in pHe in tumors: similar variations in pHe were found when using in vivo EPR or invasive microelectrodes measurements. This study demonstrates the potential usefulness of TPTAM for monitoring pHe in tumors. Magn Reson Med 77:2438-2443, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Four Ca2+ Ions Activate TRPM2 Channels by Binding in Deep Crevices near the Pore but Intracellularly of the Gate

PubMed Central

Törőcsik, Beáta

2009-01-01

TRPM2 is a tetrameric Ca2+-permeable channel involved in immunocyte respiratory burst and in postischaemic neuronal death. In whole cells, TRPM2 activity requires intracellular ADP ribose (ADPR) and intra- or extracellular Ca2+, but the mechanism and the binding sites for Ca2+ activation remain unknown. Here we study TRPM2 gating in inside-out patches while directly controlling intracellular ligand concentrations. Concentration jump experiments at various voltages and Ca2+ dependence of steady-state single-channel gating kinetics provide unprecedented insight into the molecular mechanism of Ca2+ activation. In patches excised from Xenopus laevis oocytes expressing human TRPM2, coapplication of intracellular ADPR and Ca2+ activated ∼50-pS nonselective cation channels; K1/2 for ADPR was ∼1 µM at saturating Ca2+. Intracellular Ca2+ dependence of TRPM2 steady-state opening and closing rates (at saturating [ADPR] and low extracellular Ca2+) reveals that Ca2+ activation is a consequence of tighter binding of Ca2+ in the open rather than in the closed channel conformation. Four Ca2+ ions activate TRPM2 with a Monod-Wymann-Changeux mechanism: each binding event increases the open-closed equilibrium constant ∼33-fold, producing altogether 106-fold activation. Experiments in the presence of 1 mM of free Ca2+ on the extracellular side clearly show that closed channels do not sense extracellular Ca2+, but once channels have opened Ca2+ entering passively through the pore slows channel closure by keeping the “activating sites” saturated, despite rapid continuous Ca2+-free wash of the intracellular channel surface. This effect of extracellular Ca2+ on gating is gradually lost at progressively depolarized membrane potentials, where the driving force for Ca2+ influx is diminished. Thus, the activating sites lie intracellularly from the gate, but in a shielded crevice near the pore entrance. Our results suggest that in intact cells that contain micromolar ADPR a single brief puff of Ca2+ likely triggers prolonged, self-sustained TRPM2 activity. PMID:19171771

Effect of extracellular ATP on contraction, cytosolic calcium activity, membrane voltage and ion currents of rat mesangial cells in primary culture.

PubMed Central

Pavenstädt, H.; Gloy, J.; Leipziger, J.; Klär, B.; Pfeilschifter, J.; Schollmeyer, P.; Greger, R.

1993-01-01

1. The effects of extracellular ATP on contraction, membrane voltage (Vm), ion currents and intracellular calcium activity [Ca2+]i were studied in rat mesangial cells (MC) in primary culture. 2. Addition of extracellular ATP (10(-5) and 10(-4) M) to MC led to a cell contraction which was independent of extracellular calcium. 3. Membrane voltage (Vm) and ion currents were measured with the nystatin patch clamp technique. ATP induced a concentration-dependent transient depolarization of Vm (ED50: 2 x 10(-6) M). During the transient depolarization ion currents were monitored simultaneously and showed an increase of the inward- and outward current. 4. In a buffer with a reduced extracellular chloride concentration (from 145 to 30 mM) ATP induced a depolarization augmented to -4 +/- 4 mV. 5. ATP-gamma-S and 2-methylthio-ATP depolarized Vm to the same extent as ATP, whereas alpha,beta-methylene-ATP (all 10(-5) M) had no effect on Vm. 6. The Ca2+ ionophore, A23187, depolarized Vm transiently from -51 +/- 2 to -28 +/- 4 mV and caused an increase of the inward current. 7. The intracellular calcium activity [Ca2+]i was measured with the fura-2 technique. ATP stimulated a concentration-dependent increase of [Ca2+]i (ED50: 5 x 10(-6) M). The increase of [Ca2+]i was biphasic with an initial peak followed by a sustained plateau. 8. The [Ca2+]i peak was still present in an extracellular Ca(2+)-free buffer, whereas the plateau was abolished. Verapamil (10(-4) M) did not inhibit the [Ca2+]i increase induced by ATP.(ABSTRACT TRUNCATED AT 250 WORDS) Images Figure 1 PMID:7691366

Enhanced MRI relaxivity of aquated Gd3+ ions by carboxyphenylated water-dispersed graphene nanoribbons

NASA Astrophysics Data System (ADS)

Gizzatov, Ayrat; Keshishian, Vazrik; Guven, Adem; Dimiev, Ayrat M.; Qu, Feifei; Muthupillai, Raja; Decuzzi, Paolo; Bryant, Robert G.; Tour, James M.; Wilson, Lon J.

2014-02-01

The present study demonstrates that highly water-dispersed graphene nanoribbons dispersed by carboxyphenylated substituents and conjugated to aquated Gd3+ ions can serve as a high-performance contrast agent (CA) for applications in T1- and T2-weighted magnetic resonance imaging (MRI) with relaxivity (r1,2) values outperforming currently-available clinical CAs by up to 16 times for r1 and 21 times for r2.The present study demonstrates that highly water-dispersed graphene nanoribbons dispersed by carboxyphenylated substituents and conjugated to aquated Gd3+ ions can serve as a high-performance contrast agent (CA) for applications in T1- and T2-weighted magnetic resonance imaging (MRI) with relaxivity (r1,2) values outperforming currently-available clinical CAs by up to 16 times for r1 and 21 times for r2. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr06026h

Elevated extracellular calcium increases expression of bone morphogenetic protein-2 gene via a calcium channel and ERK pathway in human dental pulp cells

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

Tada, Hiroyuki; Nemoto, Eiji, E-mail: e-nemoto@umin.ac.jp; Kanaya, Sousuke

Dental pulp cells, which have been shown to share phenotypical features with osteoblasts, are capable of differentiating into odontoblast-like cells and generating a dentin-like mineral structure. Elevated extracellular Ca{sup 2+}Ca{sub o}{sup 2+} has been implicated in osteogenesis by stimulating the proliferation and differentiation of osteoblasts; however, the role of Ca{sub o}{sup 2+} signaling in odontogenesis remains unclear. We found that elevated Ca{sub o}{sup 2+} increases bone morphogenetic protein (BMP)-2 gene expression in human dental pulp cells. The increase was modulated not only at a transcriptional level but also at a post-transcriptional level, because treatment with Ca{sup 2+} increased the stabilitymore » of BMP-2 mRNA in the presence of actinomycin D, an inhibitor of transcription. A similar increase in BMP-2 mRNA level was observed in other human mesenchymal cells from oral tissue; periodontal ligament cells and gingival fibroblasts. However, the latter cells exhibited considerably lower expression of BMP-2 mRNA compared with dental pulp cells and periodontal ligament cells. The BMP-2 increase was markedly inhibited by pretreatment with an extracellular signal-regulated kinase (ERK) inhibitor, PD98059, and partially inhibited by the L-type Ca{sup 2+} channels inhibitor, nifedipine. However, pretreatment with nifedipine had no effect on ERK1/2 phosphorylation triggered by Ca{sup 2+}, suggesting that the Ca{sup 2+} influx from Ca{sup 2+} channels may operate independently of ERK signaling. Dental pulp cells do not express the transcript of Ca{sup 2+}-sensing receptors (CaSR) and only respond slightly to other cations such as Sr{sup 2+} and spermine, suggesting that dental pulp cells respond to Ca{sub o}{sup 2+} to increase BMP-2 mRNA expression in a manner different from CaSR and rather specific for Ca{sub o}{sup 2+} among cations.« less

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

NASA Technical Reports Server (NTRS)

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

2000-01-01

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

A RRKM study and a DFT assessment on gas-phase fragmentation of formamide-M(2+) (M = Ca, Sr).

PubMed

Martín-Sómer, Ana; Gaigeot, Marie-Pierre; Yáñez, Manuel; Spezia, Riccardo

2014-07-28

A kinetic study of the unimolecular reactivity of formamide-M(2+) (M = Ca, Sr) systems was carried out by means of RRKM statistical theory using high-level DFT. The results predict M(2+), [M(NH2)](+) and [HCO](+) as the main products, together with an intermediate that could eventually evolve to produce [M(NH3)](2+) and CO, for high values of internal energy. In this framework, we also evaluated the influence of the external rotational energy on the reaction rate constants. In order to find a method to perform reliable electronic structure calculations for formamide-M(2+) (M = Ca, Sr) at a relatively low computational cost, an assessment of different methods was performed. In the first assessment twenty-one functionals, belonging to different DFT categories, and an MP2 wave function method using a small basis set were evaluated. CCSD(T)/cc-pWCVTZ single point calculations were used as reference. A second assessment has been performed on geometries and energies. We found BLYP/6-31G(d) and G96LYP/6-31+G(d,p) as the best performing methods, for formamide-Ca(2+) and formamide-Sr(2+), respectively. Furthermore, a detailed assessment was done on RRKM reactivity and G96LYP/6-31G(d) provided results in agreement with higher level calculations. The combination of geometrical, energetics and kinetics (RRKM) criteria to evaluate DFT functionals is rather unusual and provides an original assessment procedure. Overall, we suggest using G96LYP as the best performing functional with a small basis set for both systems.

Development of Gd3N@C80 encapsulated redox nanoparticles for high-performance magnetic resonance imaging.

PubMed

Gao, Zhenyu; Nakanishi, Yusuke; Noda, Shoko; Omachi, Haruka; Shinohara, Hisanori; Kimura, Hiroyuki; Nagasaki, Yukio

As novel magnetic resonance imaging (MRI) contrast agent, gadofullerene encapsulated redox nanoparticles (Gd 3 NPs) were prepared by encapsulation of Gd 3 N@C 80 in the core of core-shell-type polymer micelles composed of original polyamine with a reactive oxygen species (ROS)-scavenging ability. Because Gd 3 NPs possess biocompatible PEG shell with a smaller size (ca. 50 nm), they had high colloidal stability in a physiological environment, and showed low cytotoxicity. Specific accumulation of Gd 3 NPs in a tumor was confirmed in tumor-bearing mice after systemic administration. The tumor/muscle (T/M) ratio of the Gd ion reached five at 7.5 h after the administration. T 1 -weighted MRI signal enhancement of the T/M ratio increased by 8% at 6 h postinjection of Gd 3 NPs (Gd dose:14.35 μmol/kg). Although Gd 3 NPs showed a tendency for extended blood circulation, they did not have severe adverse effects, probably due to the confinement of Gd in a hydrophobic fullerene in addition to the ROS-scavenging capacity of these nanoparticles. In sharp contrast, systemic administration of Gd-chelate nanoparticles (GdCNPs) to mice disrupts liver function, increases leukocyte counts, and destroys spleen and skin tissues. Leaking of Gd ions from GdCNPs may cause such adverse effects. Based on these results, we expect that Gd 3 NPs is high-performance MRI contrast agents for tumor diagnosis.

Mechanism of extracellular ion exchange and binding-site occlusion in the sodium-calcium exchanger

PubMed Central

Lee, ChangKeun; Huang, Yihe; Faraldo-Gómez, José D.; Jiang, Youxing

2016-01-01

Na+/Ca2+ exchangers utilize the Na+ electrochemical gradient across the plasma membrane to extrude intracellular Ca2+, and play a central role in Ca2+ homeostasis. Here, we elucidate their mechanisms of extracellular ion recognition and exchange through a structural analysis of the exchanger from Methanococcus jannaschii (NCX_Mj) bound to Na+, Ca2+ or Sr2+ in various occupancies and in an apo state. This analysis defines the binding mode and relative affinity of these ions, establishes the structural basis for the anticipated 3Na+:1Ca2+ exchange stoichiometry, and reveals the conformational changes at the onset of the alternating-access transport mechanism. An independent analysis of the dynamics and conformational free-energy landscape of NCX_Mj in different ion-occupancy states, based on enhanced-sampling molecular-dynamics simulations, demonstrates that the crystal structures reflect mechanistically relevant, interconverting conformations. These calculations also reveal the mechanism by which the outward-to-inward transition is controlled by the ion-occupancy state, thereby explaining the emergence of strictly-coupled Na+/Ca2+ antiport. PMID:27183196

Mechanism of extracellular ion exchange and binding-site occlusion in a sodium/calcium exchanger

DOE PAGES

Liao, Jun; Marinelli, Fabrizio; Lee, Changkeun; ...

2016-05-16

Na +/Ca 2+ exchangers utilize the Na + electrochemical gradient across the plasma membrane to extrude intracellular Ca 2+, and play a central role in Ca 2+ homeostasis. Here, we elucidate their mechanisms of extracellular ion recognition and exchange through a structural analysis of the exchanger from Methanococcus jannaschii (NCX_Mj) bound to Na +, Ca 2+ or Sr 2+ in various occupancies and in an apo state. This analysis defines the binding mode and relative affinity of these ions, establishes the structural basis for the anticipated 3:1Na +/Ca 2+ exchange stoichiometry, and reveals the conformational changes at the onset ofmore » the alternating-access transport mechanism. An independent analysis of the dynamics and conformational free-energy landscape of NCX_Mj in different ion-occupancy states, based on enhanced-sampling molecular-dynamics simulations, demonstrates that the crystal structures reflect mechanistically relevant, interconverting conformations. Lastly, these calculations also reveal the mechanism by which the outward-to-inward transition is controlled by the ion-occupancy state, thereby explaining the emergence of strictly-coupled Na +/Ca 2+ antiport.« less

Deficits in cognitive function and hippocampal plasticity in GM2/GD2 synthase knockout mice.

PubMed

Sha, Sha; Zhou, Libin; Yin, Jun; Takamiya, Koga; Furukawa, Keiko; Furukawa, Koichi; Sokabe, Masahiro; Chen, Ling

2014-04-01

In this study, we used GM2/GD2 synthase knockout (GM2/GD2−/−) mice to examine the influence of deficiency in ganglioside “a-pathway” and “b-pathway” on cognitive performances and hippocampal synaptic plasticity. Eight-week-old GM2/GD2−/− male mice showed a longer escape-latency in Morris water maze test and a shorter latency in step-down inhibitory avoidance task than wild-type (WT) mice. Schaffer collateral-CA1 synapses in the hippocampal slices from GM2/GD2−/− mice showed an increase in the slope of EPSPs with reduced paired-pulse facilitation, indicating an enhancement of their presynaptic glutamate release. In GM2/GD2−/− mice, NMDA receptor (NMDAr)-dependent LTP could not be induced by high-frequency (100–200 Hz) tetanus or θ-burst conditioning stimulation (CS), whereas NMDAr-independent LTP was induced by medium-frequency CS (20–50 Hz). The application of mono-sialoganglioside GM1 in the slice from GM2/GD2−/− mice, to specifically recover the a-pathway, prevented the increased presynaptic glutamate release and 20 Hz-LTP induction, whereas it could not rescue the impaired NMDAr-dependent LTP. These findings suggest that b-pathway deficiency impairs cognitive function probably through suppression of NMDAr-dependent LTP, while a-pathway deficiency may facilitate NMDAr-independent LTP through enhancing presynaptic glutamate release. As both of the NMDAr-independent LTP and increased presynaptic glutamate release were sensitive to the blockade of L-type voltage-gated Ca2+ channels (L-VGCC), a-pathway deficiency may affect presynaptic L-VGCC.

Pharmacological properties of excitatory amino acid induced changes in extracellular calcium concentration in rat hippocampal slices.

PubMed

Arens, J; Stabel, J; Heinemann, U

1992-01-01

We have studied extracellular ionic changes induced by iontophoretic application of excitatory amino acids in rat hippocampal slices. In contrast to kinetics of changes in [Ca2+]o, kinetics of changes in [K+]o, [Na+]o, [Cl-]o as well as in extracellular space size were comparable for different glutamate receptor agonists. Thus, alpha-amino-3-hydroxy-5-methylisoxazolepropionic acid (AMPA), quisqualate (quis), and kainate caused reductions in [Ca2+]o followed by an increase of [Ca2+]o above baseline, whereas glutamate, aspartate, N-methyl-D-aspartate (NMDA), and DL-homocysteic acid caused only reductions in [Ca2+]o. After blocking the NMDA receptors with ketamine and 2-amino-5- phosphonovaleric acid (2-APV), glutamate-induced decreases in [Ca2+]o were followed by an overshoot. Reduction of the transmembrane Na+ gradient by lowering [Na+]o, blocking of the Na(+)-K+ ATPase by lowering [K+]o, and application of ouabain blocked the overshoots after quis application, whereas vanadate, a blocker of the Ca(2+)-Mg2+ ATPase, had no effects. Lithium enhanced the reductions in [Ca2+]o and blocked the overshoots. Amiloride also reduced the overshoots. All organic Ca2+ entry blockers diminished reductions of [Ca2+]o but increased the overshoots. Inorganic Ca2+ antagonists had variable effects. Ni2+ had similar effects as the organic Ca2+ entry blockers while Cd2+ reduced both the [Ca2+]o decreases as well as the subsequent overshoots. Co2+ had initially a similar action as Ni2+. With prolonged application, [Ca2+]o decreases became augmented and, during wash, overshoots could no longer be elicited. We suggest that the overshoots in [Ca2+]o are due to a combined effect of extracellular space shrinkage and activation of the Na+/Ca2+ exchangers. This would imply that NMDA receptor activation blocks extrusion of Ca2+ from the cells. We tested the hypothesis that quis-induced intracellular Ca2+ release and extrusion of Ca2+ from the cells contributed to the overshoots. Dantrolene was without effect on the quis-induced signals, while ryanodine reduced the overshoots. Caffeine on the other hand diminished the [Ca2+]o decreases with no effects on the overshoots. To test for possible second messenger routes by which NMDA receptor activation might slow Ca2+ extrusion from cells, we investigated the effects of arachidonic acid and N-monomethyl-D- arginine on the quis-induced signals. While these agents reduced decreases in [Ca2+]o, they had no clear effects on the overshoots. Thus a possible route by which NMDA receptor activation may affect Ca2+ extrusion from cells has still to be elucidated.

Magnetic Resonance Imaging of Acute Reperfused Myocardial Infarction: Intraindividual Comparison of ECIII-60 and Gd-DTPA in a Swine Model

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

Jin Jiyang; Teng Gaojun; Feng Yi

2007-04-15

Purpose. To compare a necrosis-avid contrast agent (NACA) bis-Gd-DTPA-pamoic acid derivative (ECIII-60) after intracoronary delivery with an extracellular agent Gd-DTPA after intravenous injection on magnetic resonance imaging (MRI) in a swine model of acute reperfused myocardial infarction (MI). Methods. Eight pigs underwent 90 min of transcatheter coronary balloon occlusion and 60 min of reperfusion. After intravenous injection of Gd-DTPA at a dose of 0.2 mmol/kg, all pigs were scanned with T1-weighted MRI until the delayed enhancement of MI disappeared. Then they were intracoronarily infused with ECIII-60 at 0.0025 mmol/kg and imaged for 5 hr. Signal intensity, infarct-over-normal contrast ratio andmore » relative infarct size were quantified, compared, and correlated with the results of postmortem MRI and triphenyltetrazolium chloride (TTC) histochemical staining. Results. A contrast ratio over 3.0 was induced by both Gd-DTPA and ECIII-60. However, while the delayed enhancement with Gd-DTPA virtually vanished in 1 hr, ECIII-60 at an 80x smaller dose depicted the MI accurately over 5 hr as proven by ex vivo MRI and TTC staining. Conclusion. Both Gd-DTPA and ECIII-60 strongly enhanced acute MI. Comparing with fading contrast in a narrow time window with intravenous Gd-DTPA, intracoronary ECIII-60 persistently demarcated the acute MI, indicating a potential method for postprocedural assessment of myocardial viability after coronary interventions.« less

Health economic assessment of Gd-EOB-DTPA MRI versus ECCM-MRI and multi-detector CT for diagnosis of hepatocellular carcinoma in China

PubMed Central

He, Xiaoning; Holtorf, Anke-Peggy; Rinde, Harald; Xie, Shuangshuang; Shen, Wen; Hou, Jiancun; Li, Xuehua; Li, Ziping; Lai, Jiaming; Wang, Yuting; Zhang, Lin; Wang, Jian; Li, Xuesong; Ma, Kuansheng; Ye, Feng; Ouyang, Han; Zhao, Hong

2018-01-01

Limited data exists in China on the comparative cost of gadolinium ethoxybenzyl diethylenetriamine magnetic resonance imaging (Gd-EOB-DTPA-MRI) with other imaging techniques. This study compared the total cost of Gd-EOB-DTPA-MRI with multidetector computed tomography (MDCT) and extracellular contrast media–enhanced MRI (ECCM-MRI) as initial imaging procedures in patients with suspected hepatocellular carcinoma (HCC). We developed a decision-tree model on the basis of the Chinese clinical guidelines for HCC, which was validated by clinical experts from China. The model compared the diagnostic accuracy and costs of alternative initial imaging procedures. Compared with MDCT and ECCM-MRI, Gd-EOB-DTPA-MRI imaging was associated with higher rates of diagnostic accuracy, i.e. higher proportions of true positives (TP) and true negatives (TN) with lower false positives (FP). Total diagnosis and treatment cost per patient after the initial Gd-EOB-DTPA-MRI evaluation was similar to MDCT (¥30,360 vs. ¥30,803) and lower than that reported with ECCM-MRI (¥30,360 vs. ¥31,465). Lower treatment cost after initial Gd-EOB-DTPA-MRI was driven by reduced utilization of confirmatory diagnostic procedures and unnecessary treatments. The findings reported that Gd-EOB-DTPA-MRI offered higher diagnostic accuracy compared with MDCT and ECCM-MRI at a comparable cost, which indicates Gd-EOB-DTPA-MRI could be the preferred initial imaging procedure for the diagnosis of HCC in China. PMID:29324837

Moderate extracellular acidification inhibits capsaicin-induced cell death through regulating calcium mobilization, NF-{kappa}B translocation and ROS production in synoviocytes

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

Hu, Fen; Yang, Shuang; Zhao, Dan

Highlights: Black-Right-Pointing-Pointer Moderate extracellular acidification regulates intracellular Ca{sup 2+} mobilization. Black-Right-Pointing-Pointer Moderate acidification activates NF-{kappa}B nuclear translocation in synoviocytes. Black-Right-Pointing-Pointer Moderate acidification depresses the ROS production induced by capsaicin. Black-Right-Pointing-Pointer Moderate acidification inhibits capsaicin-caused synoviocyte death. -- Abstract: We previously show the expression of transient receptor potential vanilloid 1 (TRPV1) in primary synoviocytes from collagen-induced arthritis (CIA) rats. Capsaicin and lowered extracellular pH from 7.4 to 5.5 induce cell death through TRPV1-mediated Ca{sup 2+} entry and reactive oxygen species (ROS) production. However, under the pathological condition in rheumatoid arthritis, the synovial fluid is acidified to a moderate level (about pHmore » 6.8). In the present study, we examined the effects of pH 6.8 on the TRPV1-mediated cell death. Our finding is different or even opposite from what was observed at pH 5.5. We found that the moderate extracellular acidification (from pH 7.4 to 6.8) inhibited the capsaicin-induced Ca{sup 2+} entry through attenuating the activity of TRPV1. In the mean time, it triggered a phospholipse C (PLC)-related Ca{sup 2+} release from intracellular stores. The nuclear translocation of NF-{kappa}B was found at pH 6.8, and this also depends on PLC activation. Moreover, the capsaicin-evoked massive ROS production and cell death were depressed at pH 6.8, both of which are dependent on the activation of PLC and NF-{kappa}B. Taken together, these results suggested that the moderate extracellular acidification inhibited the capsaicin-induced synoviocyte death through regulating Ca{sup 2+} mobilization, activating NF-{kappa}B nuclear translocation and depressing ROS production.« less

Coupling Gd-DTPA with a bispecific, recombinant protein anti-EGFR-iRGD complex improves tumor targeting in MRI

PubMed Central

XIN, XIAOYAN; SHA, HUIZI; SHEN, JINGTAO; ZHANG, BING; ZHU, BIN; LIU, BAORUI

2016-01-01

Recombinant anti-epidermal growth factor receptor-internalizing arginine-glycine-aspartic acid (anti-EGFR single-domain antibody fused with iRGD peptide) protein efficiently targets the EGFR extracellular domain and integrin αvβ/β5, and shows a high penetration into cells. Thus, this protein may improve penetration of conjugated drugs into the deep zone of gastric cancer multicellular 3D spheroids. In the present study, a novel tumor-targeting contrast agent for magnetic resonance imaging (MRI) was developed, by coupling gadolinium-diethylene triamine pentaacetate (Gd-DTPA) with the bispecific recombinant anti-EGFR-iRGD protein. The anti-EGFR-iRGD protein was extracted from Escherichia coli and Gd was loaded onto the recombinant protein by chelation using DTPA anhydride. Single-targeting agent anti-EGFR-DTPA-Gd, which served as the control, was also prepared. The results of the present study showed that anti-EGFR-iRGD-DTPA-Gd exhibited no significant cyto toxicity to human gastric carcinoma cells (BGC-823) under the experimental conditions used. Compared with a conventional contrast agent (Magnevist), anti-EGFR-iRGD-DTPA-Gd showed higher T1 relaxivity (10.157/mM/sec at 3T) and better tumor-targeting ability. In addition, the signal intensity and the area under curve for the enhanced signal time in tumor, in vivo, were stronger than Gd-DTPA alone or the anti-EGFR-Gd control. Thus, Gd-labelled anti-EGFR-iRGD has potential as a tumor-targeting contrast agent for improved MRI. PMID:27035336

Effect of toluene diisocyanate on homeostasis of intracellular-free calcium in human neuroblastoma SH-SY5Y Cells

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

Liu, P.-S.; Chiung, Y.-M.; Department of Microbiology and Immunology, National Defense Medical Center, Taipei, Taiwan

2006-03-01

The mechanisms of TDI (2,4-toluene diisocyanate)-induced occupational asthma are not fully established. Previous studies have indicated that TDI induces non-specific bronchial hyperreactivity to methacholine and induces contraction of smooth muscle tissue by activating 'capsaicin-sensitive' nerves resulting asthma. Cytosolic-free calcium ion concentrations ([Ca{sup 2+}]{sub c}) are elevated when either capsaicin acts at vanilloid receptors, or methacholine at muscarinic receptors. This study therefore investigated the effects of TDI on Ca{sup 2+} mobilization in human neuroblastoma SH-SY5Y cells. TDI was found to elevate [Ca{sup 2+}]{sub c} by releasing Ca{sup 2+} from the intracellular stores and extracellular Ca{sup 2+} influx. 500 {mu}M TDI inducedmore » a net [Ca{sup 2+}]{sub c} increase of 112 {+-} 8 and 78 {+-} 6 nM in the presence and absence of extracellular Ca{sup 2+}, respectively. In Ca{sup 2+}-free buffer, TDI induced Ca{sup 2+} release from internal stores to reduce their Ca{sup 2+} content and this reduction was evidenced by a suppression occurring on the [Ca{sup 2+}]{sub c} rise induced by thapsigargin, ionomycin, and methacholine after TDI incubation. In the presence of extracellular Ca{sup 2+}, simultaneous exposure to TDI and methacholine led a higher level of [Ca{sup 2+}]{sub c} compared to single methacholine stimulation, that might explain that TDI induces bronchial hyperreactivity to methacholine. We conclude that TDI is capable of interfering the [Ca{sup 2+}]{sub c} homeostasis including releasing Ca{sup 2+} from internal stores and inducing extracellular Ca{sup 2+} influx. The interaction of this novel character and bronchial hyperreactivity need further investigation.« less

Tm:CaGdAlO4: spectroscopy, microchip laser and passive Q-switching by carbon nanostructures

NASA Astrophysics Data System (ADS)

Loiko, Pavel; Mateos, Xavier; Choi, Sun Young; Rotermund, Fabian; Liebald, Christoph; Peltz, Mark; Vernay, Sophie; Rytz, Daniel; Wang, Yicheng; Kemnitzer, Matthias; Agnesi, Antonio; Vilejshikova, Elena; Yumashev, Konstantin; Griebner, Uwe; Petrov, Valentin

2017-02-01

Absorption, stimulated-emission and gain cross-sections are determined for 3 at.% Tm:CaGdAlO4. This crystal is employed in a microchip laser diode-pumped at 802 nm. In the continuous-wave (CW) regime, this laser generates 1.16 W at 1883-1893 nm with a slope efficiency of 32% with respect to the absorbed pump power. Using a special "bandpass" output coupler, vibronic CW laser operation up to 2043 nm is achieved. For passive Q-switching of the Tm:CaGdAlO4 laser-saturable absorbers (SAs) based on CVD-grown graphene and randomly-oriented arc-discharge single-walled carbon nanotubes (SWCNTs) in a PMMA film. The SWCNT-SA demonstrates superior performance. The laser produced a maximum average output power of 245 mW at 1844 nm with a slope efficiency of 8%. The latter corresponds to a pulse energy and duration of 6 μJ and 138 ns, respectively, at a repetition rate of 41 kHz. Using the graphene-SA, 2.8 μJ, 490 ns pulses are obtained at a repetition rate of 86 kHz.

Functional interaction between bicarbonate transporters and carbonic anhydrase modulates lactate uptake into mouse cardiomyocytes.

PubMed

Peetz, Jan; Barros, L Felipe; San Martín, Alejandro; Becker, Holger M

2015-07-01

Blood-derived lactate is a precious energy substrate for the heart muscle. Lactate is transported into cardiomyocytes via monocarboxylate transporters (MCTs) together with H(+), which couples lactate uptake to cellular pH regulation. In this study, we have investigated how the interplay between different acid/base transporters and carbonic anhydrases (CA), which catalyze the reversible hydration of CO2, modulates the uptake of lactate into isolated mouse cardiomyocytes. Lactate transport was estimated both as lactate-induced acidification and as changes in intracellular lactate levels measured with a newly developed Förster resonance energy transfer (FRET) nanosensor. Recordings of intracellular pH showed an increase in the rate of lactate-induced acidification when CA was inhibited by 6-ethoxy-2-benzothiazolesulfonamide (EZA), while direct measurements of lactate flux demonstrated a decrease in MCT transport activity, when CA was inhibited. The data indicate that catalytic activity of extracellular CA increases lactate uptake and counteracts intracellular lactate-induced acidification. We propose a hypothetical model, in which HCO3 (-), formed from cell-derived CO2 at the outer surface of the cardiomyocyte plasma membrane by membrane-anchored, extracellular CA, is transported into the cell via Na(+)/HCO3 (-) cotransport to counteract intracellular acidification, while the remaining H(+) stabilizes extracellular pH at the surface of the plasma membrane during MCT activity to enhance lactate influx into cardiomyocytes.

Molecular Basis for Modulation of Metabotropic Glutamate Receptors and Their Drug Actions by Extracellular Ca2+

PubMed Central

Zou, Juan; Jiang, Jason Y.; Yang, Jenny J.

2017-01-01

Metabotropic glutamate receptors (mGluRs) associated with the slow phase of the glutamatergic signaling pathway in neurons of the central nervous system have gained importance as drug targets for chronic neurodegenerative diseases. While extracellular Ca2+ was reported to exhibit direct activation and modulation via an allosteric site, the identification of those binding sites was challenged by weak binding. Herein, we review the discovery of extracellular Ca2+ in regulation of mGluRs, summarize the recent developments in probing Ca2+ binding and its co-regulation of the receptor based on structural and biochemical analysis, and discuss the molecular basis for Ca2+ to regulate various classes of drug action as well as its importance as an allosteric modulator in mGluRs. PMID:28335551

Intracellular Ca-carbonate biomineralization is widespread in cyanobacteria.

PubMed

Benzerara, Karim; Skouri-Panet, Feriel; Li, Jinhua; Férard, Céline; Gugger, Muriel; Laurent, Thierry; Couradeau, Estelle; Ragon, Marie; Cosmidis, Julie; Menguy, Nicolas; Margaret-Oliver, Isabel; Tavera, Rosaluz; López-García, Purificación; Moreira, David

2014-07-29

Cyanobacteria have played a significant role in the formation of past and modern carbonate deposits at the surface of the Earth using a biomineralization process that has been almost systematically considered induced and extracellular. Recently, a deep-branching cyanobacterial species, Candidatus Gloeomargarita lithophora, was reported to form intracellular amorphous Ca-rich carbonates. However, the significance and diversity of the cyanobacteria in which intracellular biomineralization occurs remain unknown. Here, we searched for intracellular Ca-carbonate inclusions in 68 cyanobacterial strains distributed throughout the phylogenetic tree of cyanobacteria. We discovered that diverse unicellular cyanobacterial taxa form intracellular amorphous Ca-carbonates with at least two different distribution patterns, suggesting the existence of at least two distinct mechanisms of biomineralization: (i) one with Ca-carbonate inclusions scattered within the cell cytoplasm such as in Ca. G. lithophora, and (ii) another one observed in strains belonging to the Thermosynechococcus elongatus BP-1 lineage, in which Ca-carbonate inclusions lie at the cell poles. This pattern seems to be linked with the nucleation of the inclusions at the septum of the cells, showing an intricate and original connection between cell division and biomineralization. These findings indicate that intracellular Ca-carbonate biomineralization by cyanobacteria has been overlooked by past studies and open new perspectives on the mechanisms and the evolutionary history of intra- and extracellular Ca-carbonate biomineralization by cyanobacteria.

Variation in Extracellular Detoxification Is a Link to Different Carcinogenicity among Chromates in Rodent and Human Lungs.

PubMed

Krawic, Casey; Luczak, Michal W; Zhitkovich, Anatoly

2017-09-18

Inhalation of soluble chromium(VI) is firmly linked with higher risks of lung cancer in humans. However, comparative studies in rats have found a high lung tumorigenicity for moderately soluble chromates but no tumors for highly soluble chromates. These major species differences remain unexplained. We investigated the impact of extracellular reducers on responses of human and rat lung epithelial cells to different Cr(VI) forms. Extracellular reduction of Cr(VI) is a detoxification process, and rat and human lung lining fluids contain different concentrations of ascorbate and glutathione. We found that reduction of chromate anions in simulated lung fluids was principally driven by ascorbate with only minimal contribution from glutathione. The addition of 500 μM ascorbate (∼rat lung fluid concentration) to culture media strongly inhibited cellular uptake of chromate anions and completely prevented their cytotoxicity even at otherwise lethal doses. While proportionally less effective, 50 μM extracellular ascorbate (∼human lung fluid concentration) also decreased uptake of chromate anions and their cytotoxicity. In comparison to chromate anions, uptake and cytotoxicity of respirable particles of moderately soluble CaCrO 4 and SrCrO 4 were much less sensitive to suppression by extracellular ascorbate, especially during early exposure times and in primary bronchial cells. In the absence of extracellular ascorbate, chromate anions and CaCrO 4 /SrCrO 4 particles produced overall similar levels of DNA double-stranded breaks, with less soluble particles exhibiting a slower rate of breakage. Our results indicate that a gradual extracellular dissolution and a rapid internalization of calcium chromate and strontium chromate particles makes them resistant to detoxification outside the cells, which is extremely effective for chromate anions in the rat lung fluid. The detoxification potential of the human lung fluid is significant but much lower and insufficient to provide a threshold-type dose dependence for soluble chromates.

The impact of extracellular and intracellular Ca2+ on ethanol-induced smooth muscle contraction.

PubMed

Döndaş, Naciye Yaktubay; Kaplan, Mahir; Kaya, Derya; Singirik, Ergin

2009-10-01

To evaluate the impact of extracellular and intracellular Ca2+ on contractions induced by ethanol in smooth muscle. Longitudinal smooth muscle strips were prepared from the gastric fundi of mice. The contractions of smooth muscle strips were recorded with an isometric force displacement transducer. Ethanol (164 mmol/L) produced reproducible contractions in isolated gastric fundal strips of mice. Although lidocaine (50 and 100 micromol/L), a local anesthetic agent, and hexamethonium (100 and 500 micromol/L), a ganglionic blocking agent, failed to affect these contractions, verapamil (1-50 micromol/L) and nifedipine (1-50 micromol/L), selective blockers of L-type Ca2+ channels, significantly inhibited the contractile responses of ethanol. Using a Ca(2+)-free medium nearly eliminated these contractions in the same tissue. Ryanodine (1-50 micromol/L) and ruthenium red (10-100 micromol/L), selective blockers of intracellular Ca2+ channels/ryanodine receptors; cyclopiazonic acid (CPA; 1-10 mumol/L), a selective inhibitor of sarcoplasmic reticulum (SR) Ca(2+)-ATPase; and caffeine (0.5-5 mmol/L), a depleting agent of intracellular Ca2+ stores, significantly inhibited the contractile responses induced by ethanol. In addition, the combination of caffeine (5 mmol/L) plus CPA (10 micromol/L), and ryanodine (10 micromol/L) plus CPA (10 micromol/L), caused further inhibition of contractions in response to ethanol. This inhibition was significantly different from those associated with caffeine, ryanodine or CPA. Furthermore the combination of caffeine (5 mmol/L), ryanodine (10 micromol/L) and CPA(10 micromol/L) eliminated the contractions induced by ethanol in isolated gastric fundal strips of mice. Both extracellular and intracellular Ca2+ may have important roles in regulating contractions induced by ethanol in the mouse gastric fundus.

Crystal Chemical Substitution at Ca and La Sites in CaLa4(SiO4)3O To Design the Composition Ca1- xM xLa4-xRE x(SiO4)3O for Nuclear Waste Immobilization and Its Influence on the Thermal Expansion Behavior.

PubMed

Ravikumar, Ramya; Gopal, Buvaneswari; Jena, Hrudananda

2018-06-04

The oxysilicate apatite host CaLa 4 (SiO 4 ) 3 O has been explored for immobilization of radioactive nuclides. Divalent ion, trivalent rare earth ion, and combined ionic substitutions in the silicate oxyapatite were carried out to optimize the simulated wasteform composition. The phases were characterized by powder X-ray diffraction, FT-IR, TGA, SEM-EDS, and HT-XRD techniques. The results revealed the effect of ionic substitutions on the structure and thermal expansion behavior. The investigation resulted in the formulation of simulated wasteforms such as La 3.4 Ce 0.1 Pr 0.1 Nd 0.1 Sm 0.1 Gd 0.1 Y 0.1 (SiO 4 ) 3 O (WF-1) and Ca 0.8 Sr 0.1 Pb 0.1 La 3.4 Ce 0.1 Pr 0.1 Nd 0.1 Sm 0.1 Gd 0.1 Y 0.1 (SiO 4 ) 3 O (WF-2). In comparison to the average axial thermal expansion coefficients of the hexagonal unit cell of the parent CaLa 4 (SiO 4 ) 3 O measured in the temperature range 298-1073 K (α' a = 9.74 × 10 -6 K -1 and α' c = 10.10 × 10 -6 K -1 ), rare earth ion substitution decreases the thermal expansion coefficients, as in the case of La 3.4 Ce 0.1 Pr 0.1 Nd 0.1 Sm 0.1 Gd 0.1 Y 0.1 (SiO 4 ) 3 O (α' a = 8.67 × 10 -6 K -1 and α' c = 7.94 × 10 -6 K -1 ). However, the phase Ca 0.8 Sr 0.1 Pb 0.1 La 3.4 Ce 0.1 Pr 0.1 Nd 0.1 Sm 0.1 Gd 0.1 Y 0.1 (SiO 4 ) 3 O shows an increase in the values of thermal expansion coefficients: α' a = 11.74 × 10 -6 K -1 and α' c = 11.70 × 10 -6 K -1 .

Generation and functional analysis of monoclonal antibodies against the second extracellular loop of human M3 muscarinic acetylcholine receptor.

PubMed

Tsuboi, Hiroto; Nakamura, Yumi; Iizuka, Mana; Matsuo, Naomi; Matsumoto, Isao; Sumida, Takayuki

2012-04-01

The M3 muscarinic acetylcholine receptor (M3R) plays a crucial role in the activation of salivary and lachrymal glands. The M3R contains four extracellular domains (the N-terminal, and the first, second, and third extracellular loops), and we recently detected antibodies against each of these four domains in a subgroup of patients with Sjögren's syndrome (SS). Functional analysis indicated that the influence of such anti-M3R antibodies on salivary secretion might differ based on the epitopes to which they bind. To clarify the relationship between B-cell epitopes on the M3R and its function, we generated two hybridomas producing anti-M3R monoclonal antibodies against the second extracellular loop of M3R (anti-M3R(2nd) mAbs) and analyzed their function by Ca(2+)-influx assays, using a human salivary gland (HSG) cell line. These two anti-M3R(2nd) mAbs suppressed Ca(2+)-influx in the HSG cells induced by cevimeline stimulation, suggesting that autoantibodies against the second extracellular loop of M3R could be involved in salivary dysfunction in patients with SS.

Response of extracellular zinc in the ventral hippocampus against novelty stress.

PubMed

Takeda, Atsushi; Sakurada, Naomi; Kanno, Shingo; Minami, Akira; Oku, Naoto

2006-10-01

An extensive neuronal activity takes place in the hippocampus during exploratory behavior. However, the role of hippocampal zinc in exploratory behavior is poorly understood. To analyze the response of extracellular zinc in the hippocampus against novelty stress, rats were placed for 50 min in a novel environment once a day for 8 days. Extracellular glutamate in the hippocampus was increased during exploratory behavior on day 1, whereas extracellular zinc was decreased. The same phenomenon was observed during exploratory behavior on day 2 and extracellular zinc had returned to the basal level during exploratory behavior on day 8. To examine the significance of the decrease in extracellular zinc in exploratory activity, exploratory behavior was observed during perfusion with 1 mm CaEDTA, a membrane-impermeable zinc chelator. Locomotor activity in the novel environment was decreased by perfusion with CaEDTA. The decrease in extracellular zinc and the increase in extracellular glutamate in exploratory period were abolished by perfusion with CaEDTA. These results suggest that zinc uptake by hippocampal cells is linked to exploratory activity and is required for the activation of the glutamatergic neurotransmitter system. The zinc uptake may be involved in the response to painless psychological stress or in the cognitive processes.

Individual Differences in Military Training Environments: Four Areas of Research

DTIC Science & Technology

1987-01-30

training setting. Such factors as ability, skills, experience, intelligence , interests, personal characteristics (e.g., age) and motivation interact...recruits than were Intelligence scores; fast learners retained more and relearned more quickly than slow learners. This suggests that if the goal is to...and Development Center. Gottfredson , G.D., Holland, J.L. and Ogawa, D.K. (1982). Dictionary of Holland occupational codes. Palo Alto, CA: Consulting

Structure and thermal expansion of Ca9Gd(VO4)7: A combined powder-diffraction and dilatometric study of a Czochralski-grown crystal

NASA Astrophysics Data System (ADS)

Paszkowicz, Wojciech; Shekhovtsov, Alexei; Kosmyna, Miron; Loiko, Pavel; Vilejshikova, Elena; Minikayev, Roman; Romanowski, Przemysław; Wierzchowski, Wojciech; Wieteska, Krzysztof; Paulmann, Carsten; Bryleva, Ekaterina; Belikov, Konstantin; Fitch, Andrew

2017-11-01

Materials of the Ca9RE(VO4)7 (CRVO) formula (RE = rare earth) and whitlockite-related structures are considered for applications in optoelectronics, e.g., in white-light emitting diodes and lasers. In the CRVO structure, the RE atoms are known to share the site occupation with Ca atoms at two or three among four Ca sites, with partial occupancy values depending on the choice of the RE atom. In this work, the structure and quality of a Czochralski-grown crystal of this family, Ca9Gd(VO4)7 (CGVO), are studied using X-ray diffraction methods. The room-temperature structure is refined using the powder diffraction data collected at a high-resolution synchrotron beamline ID22 (ESRF, Grenoble); for comparison purposes, a laboratory diffraction pattern was collected and analyzed, as well. The site occupancies are discussed on the basis of comparison with literature data of isostructural synthetic crystals of the CRVO series. The results confirm the previously reported site-occupation scheme and indicate a tendency of the CGVO compound to adopt a Gd-deficient composition. Moreover, the thermal expansion coefficient is determined for CGVO as a function of temperature in the 302-1023 K range using laboratory diffraction data. Additionally, for CGVO and six other single crystals of the same family, thermal expansion is studied in the 298-473 K range, using the dilatometric data. The magnitude and anisotropy of thermal expansion, being of importance for laser applications, are discussed for these materials.

A CW green laser emission by self-sum-frequency-mixing in Nd:GdCOB crystal

NASA Astrophysics Data System (ADS)

Shao, Y.; Jin, H. J.; Lin, J.; Zhang, D.; Tao, Z. H.; Zhang, T. Y.; Li, Y. L.; Ruan, Q. R.

2011-10-01

A compact and efficient green laser light at 538 nm produced by self-sum-frequency-mixing of both fundamental infrared laser waves (1061 and 1091 nm) in Nd:GdCa4O(BO3)3 (Nd:GdCOB) crystal is demonstrated. With 18.2 W of diode pump power, a maximum output power of 1.73 W in the green spectral range at 538 nm has been achieved, corresponding to an optical-to-optical conversion efficiency of 9.5%; the output power stability over 30 min is better than 3%. To the best of our knowledge, this is first work on self-sum-frequency-mixing of a diode pumped Nd:GdCOB laser.

Extracellular Ca²⁺ acts as a mediator of communication from neurons to glia.

PubMed

Torres, Arnulfo; Wang, Fushun; Xu, Qiwu; Fujita, Takumi; Dobrowolski, Radoslaw; Willecke, Klaus; Takano, Takahiro; Nedergaard, Maiken

2012-01-24

Defining the pathways through which neurons and astrocytes communicate may contribute to the elucidation of higher central nervous system functions. We investigated the possibility that decreases in extracellular calcium ion concentration ([Ca(2+)](e)) that occur during synaptic transmission might mediate signaling from neurons to glia. Using noninvasive photolysis of the photolabile Ca(2+) buffer diazo-2 {N-[2-[2-[2-[bis(carboxymethyl)amino]-5-(diazoacetyl)phenoxy]ethoxy]-4-methylphenyl]-N-(carboxymethyl)-, tetrapotassium salt} to reduce [Ca(2+)](e) or caged glutamate to simulate glutamatergic transmission, we found that a local decline in extracellular Ca(2+) triggered astrocytic adenosine triphosphate (ATP) release and astrocytic Ca(2+) signaling. In turn, activation of purinergic P2Y1 receptors on a subset of inhibitory interneurons initiated the generation of action potentials by these interneurons, thereby enhancing synaptic inhibition. Thus, astrocytic ATP release evoked by an activity-associated decrease in [Ca(2+)](e) may provide a negative feedback mechanism that potentiates inhibitory transmission in response to local hyperexcitability.

Extracellular Ca2+ Acts as a Mediator of Communication from Neurons to Glia

PubMed Central

Torres, Arnulfo; Wang, Fushun; Xu, Qiwu; Fujita, Takumi; Dobrowolski, Radoslaw; Willecke, Klaus; Takano, Takahiro; Nedergaard, Maiken

2013-01-01

Defining the pathways through which neurons and astrocytes communicate may contribute to the elucidation of higher central nervous system functions. We investigated the possibility that decreases in extracellular calcium ion concentration ([Ca2+]e) that occur during synaptic transmission might mediate signaling from neurons to glia. Using noninvasive photolysis of the photolabile Ca2+ buffer diazo-2 {N-[2-[2-[2-[bis(carboxymethyl)amino]-5-(diazoacetyl)phenoxy]ethoxy]-4-methylphenyl]-N-(carboxymethyl)-, tetrapotassium salt} to reduce [Ca2+]e or caged glutamate to simulate glutamatergic transmission, we found that a local decline in extracellular Ca2+ triggered astrocytic adenosine triphosphate (ATP) release and astrocytic Ca2+ signaling. In turn, activation of purinergic P2Y1 receptors on a subset of inhibitory interneurons initiated the generation of action potentials by these interneurons, thereby enhancing synaptic inhibition. Thus, astrocytic ATP release evoked by an activity-associated decrease in [Ca2+]e may provide a negative feedback mechanism that potentiates inhibitory transmission in response to local hyperexcitability. PMID:22275221

Magnetic structures and magnetocaloric effect in R VO4 (R =Gd , Nd )

NASA Astrophysics Data System (ADS)

Palacios, E.; Evangelisti, M.; Sáez-Puche, R.; Dos Santos-García, A. J.; Fernández-Martínez, F.; Cascales, C.; Castro, M.; Burriel, R.; Fabelo, O.; Rodríguez-Velamazán, J. A.

2018-06-01

We report the magnetic properties and magnetic structure of the zircon-type compound GdVO4, together with the magnetic structure of the isostructural NdVO4. At T ≃2.5 K, GdVO4 undergoes a phase transition to antiferromagnetic Gz, driven mainly by the exchange interactions, while the magnetic anisotropy and dipolar interactions are minor contributions. Near the liquid-helium boiling temperature, the magnetocaloric effect of GdVO4 is nearly as large as that of the structurally closely related GdPO4. It is noteworthy that GdVO4 has been recently proposed as a good passive regenerator in Gifford-McMahon cryocoolers, since adding a magnetization-demagnetization stage to the cryocooler refrigeration cycle would increase its efficiency for liquefying helium. NdVO4 is a canted Gz-type antiferromagnet and shows enhancement of the magnetic reflections in neutron diffraction below ca. 500 mK, due to the polarization of the Nd nuclei by the hyperfine field.

[Change in concentration of cytosolic Ca2+ caused by extracellular ATP and ecto-ATP-ase activity in thymocytes and transformed MT-4 cells].

PubMed

Hrebinyk, S M; Artemenko, O Iu; Hryniuk, I I; Perepelitsyna, O M; Matyshevs'ka, O P

2009-01-01

The comparative study of extracellular ATP (ATP0) effect on free cytosolic calcium concentration ([Ca2+]i) in normal (isolated rat thymocytes) and transformed (leukosis MT-4 line) T-cells was carried out. Addition of 1 mM ATP to Ca-free incubation medium of both types of cells, loaded with indo-1, had no effect on [Ca2+]i level. Upon subsequent addition of 1 mM CaCl2 to the incubation medium the rapid and significant increase of [Ca2+]i in MT-4 cells was registered. This effect was maintained within 10 min and was not inhibited by phospholipase C inhibitor 0.2 mM neomycin, that was induced by cation entry into the cells from the extracellular medium. Both types of cells were shown to demonstrate ecto-ATPase activity in the presence of 1 mM MgCl2 or CaC12 in the incubation medium. Estimation of kinetic parameters has indicated that the maximum rate of extracellular ATP hydrolysis by MT-4 cells is higher and Mg2+ and Ca2+ activation constants are lower as compared to respective parameters of ATP hydrolysis by thymocytes. The possible functional significance of the increased level of ecto-ATPase activity in malignantly transformed cells is discussed.

Elemental compositions of two extrasolar rocky planetesimals

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

Xu, S.; Jura, M.; Klein, B.

2014-03-10

We report Keck/HIRES and Hubble Space Telescope/COS spectroscopic studies of extrasolar rocky planetesimals accreted onto two hydrogen atmosphere white dwarfs, G29-38 and GD 133. In G29-38, eight elements are detected, including C, O, Mg, Si, Ca, Ti, Cr, and Fe while in GD 133, O, Si, Ca, and marginally Mg are seen. These two extrasolar planetesimals show a pattern of refractory enhancement and volatile depletion. For G29-38, the observed composition can be best interpreted as a blend of a chondritic object with some refractory-rich material, a result from post-nebular processing. Water is very depleted in the parent body accreted ontomore » G29-38, based on the derived oxygen abundance. The inferred total mass accretion rate in GD 133 is the lowest of all known dusty white dwarfs, possibly due to non-steady state accretion. We continue to find that a variety of extrasolar planetesimals all resemble to zeroth order the elemental composition of bulk Earth.« less

Growth stimulating antibody, as another predisposing factor of Graves' disease (GD): analysis using monoclonal TSH receptor antibodies derived from patients with GD.

PubMed

Ihara, Yoshiaki; Kanda, Yasunari; Seo, Marie; Watanabe, Yasuhiro; Akamizu, Takashi; Tanaka, Yuji

2012-01-01

TSH receptor antibody (TRAb) is clinically classified into thyroid stimulating antibody (TSAb) and thyroid-stimulation blocking antibody (TSBAb). Although the former is considered to cause Graves' disease (GD), its activity does not necessarily reflect hormone production and goiter size. Moreover, uptake of 99mTcO4(-), the best indicator for GD, is correlated with activity of TSH binding inhibitor immunoglobulin better than activity of TSAb. Because uptake of 99mTcO4(-) reflects thyroid volume, these observations suggest that there exist TRAb with thyrocyte growth stimulating activity (GSA) other than TSAb. In this study, we analyzed GSA of monoclonal TRAb established from patients with GD or idiopathic myxedema (IME). GSA was measured as the degree of FRTL-5 cell growth stimulated by each TRAb. The signaling pathways of the cell growth were pharmacologically analyzed. The cell growth stimulated by TSH was strongly suppressed by protein kinase A (PKA) inhibitor, but was not affected by extracellular signal regulated kinase kinase (MEK) inhibitor. Although TSAb from GD stimulated the cell growth, both inhibitors suppressed it. Surprisingly, the cell growth was also induced by TSBAb from GD and was only suppressed by MEK inhibitor. TSBAb from IME did not have GSA and attenuated the cell growth stimulated by TSH. We concluded that 1; in GD, not only TSAb but some TSBAb could stimulate thyrocyte growth. 2; TSBAb might be classified with respect to their effects on thyrocyte growth; i.e., thyrocyte growth stimulating antibody and thyrocyte growth-stimulation blocking antibody.

AFLOWLIB.ORG: a Distributed Materials Properties Repository from High-throughput Ab initio Calculations

DTIC Science & Technology

2011-11-15

uncle) fcc (uncle) hcp (uncle) phase-diagram Ag Al Al Au Au Bi Bi Ca Ca Cd Cd Ce Ce Co Co Cr Cr Cu Cu Fe Fe Ga Ga Gd Gd Ge Ge Hf...Hf Hg Hg In In Ir Ir La La Li Li Mg Mg Mn Mn Mo Mo Na Na Nb Nb Ni Ni Os Os Pb Pb Pd Pd Pt Pt Rb Rb Re Re Rh Rh Ru Ru Sb Sb Sc...2 S. Curtarolo, A. N. Kolmogorov, and F. H. Cocks, High-throughput ab initio analysis of the Bi-In, Bi- Mg , Bi-Sb, In- Mg , In-Sb, and Mg -Sb systems

Thermoelectric and Magnetic Properties of Ca0.98RE0.02MnO3- δ (RE = Sm, Gd, and Dy)

NASA Astrophysics Data System (ADS)

Bhaskar, Ankam; Liu, Chia-Jyi; Yuan, J. J.

2012-09-01

Polycrystalline samples of Ca0.98RE0.02MnO3- δ (RE = Sm, Gd, and Dy) have been prepared by conventional solid-state reactions and their properties measured at 300 K to 700 K. All samples were single phase with orthorhombic structure. The average valence and oxygen content of Ca0.98RE0.02MnO3- δ were determined by iodometric titration. Doping at the Ca site by rare-earth metals causes a strong decrease of electrical resistivity due to the creation of charge carrier content by Mn3+ in the Mn4+ matrix, as evidenced by iodometric titration results. The Seebeck coefficient of all the samples was negative, indicating that the predominant carriers are electrons over the entire temperature range. Among the doped samples, Ca0.98Dy0.02MnO3- δ had the highest dimensionless figure of merit of 0.073 at 612 K, representing an improvement of about 115% with respect to the undoped CaMnO3- δ sample at the same temperature. All the samples exhibited an antiferromagnetic transition with Néel temperature of around 120 K. Magnetization measurements indicated that Ca0.98RE0.02 MnO3- δ samples exhibited a high-spin state of Mn3+.

Contribution of TMEM16F to pyroptotic cell death.

PubMed

Ousingsawat, Jiraporn; Wanitchakool, Podchanart; Schreiber, Rainer; Kunzelmann, Karl

2018-02-20

Pyroptosis is a highly inflammatory form of programmed cell death that is caused by infection with intracellular pathogens and activation of canonical or noncanonical inflammasomes. The purinergic receptor P2X 7 is activated by the noncanonical inflammasome and contributes essentially to pyroptotic cell death. The Ca 2+ activated phospholipid scramblase and ion channel TMEM16F has been shown earlier to control cellular effects downstream of purinergic P2X 7 receptors that ultimately lead to cell death. As pyroptotic cell death is accompanied by an increases in intracellular Ca 2+ , we asked whether TMEM16F is activated during pyroptosis. The N-terminal cleavage product of gasdermin D (GD-N) is an executioner of pyroptosis by forming large plasma membrane pores. Expression of GD-N enhanced basal Ca 2+ levels and induced cell death. We observed that GD-N induced cell death in HEK293 and HAP1 cells, which was depending on expression of endogenous TMEM16F. GD-N activated large whole cell currents that were suppressed by knockdown or inhibition of TMEM16F. The results suggest that whole cell currents induced by the pore forming domain of gasdermin-D, are at least in part due to activation of TMEM16F. Knockdown of other TMEM16 paralogues expressed in HAP1 cells suggest TMEM16F as a crucial element during pyroptosis and excluded a role of other TMEM16 proteins. Thus TMEM16F supports pyroptosis and other forms of inflammatory cell death such as ferroptosis. Its potent inhibition by tannic acid may be part of the anti-inflammatory effects of flavonoids.

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

PubMed

Nishi, Haruhisa; Arai, Hirokazu; Momiyama, Toshihiko

2013-01-01

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

The feasibility of in vivo quantification of bone-gadolinium in humans by prompt gamma neutron activation analysis (PGNAA) following gadolinium-based contrast-enhanced MRI

NASA Astrophysics Data System (ADS)

Mostafaei, F.; McNeill, F. E.; Chettle, D. R.; Noseworthy, M. D.; Prestwich, W. V.

2015-11-01

The feasibility of using a 238Pu/Be-based in vivo prompt γ-ray neutron activation analysis (IVNAA) system, previously successfully used for measurements of muscle, for the detection of gadolinium (Gd) in bone was presented. Gd is extensively used in contrast agents in MR imaging. We present phantom measurement data for the measurement of Gd in the tibia. Gd has seven naturally occurring isotopes, of which two have extremely large neutron capture cross sections; 155Gd (14.8% natural abundance (NA), σ= 60,900 barns) and 157Gd (15.65% NA, σ= 254,000 barns). Our previous work focused on muscle but this only informs about the short term kinetics of Gd. We studied the possibility of measuring bone, as it may be a long term storage site for Gd. A human simulating bone phantom set was developed. The phantoms were doped with seven concentrations of Gd of concentrations 0.0, 25, 50, 75, 100, 120 and 150 ppm. Additional elements important for neutron activation analysis, Na, Cl and Ca, were also included to create an overall elemental composition consistent with Reference Man. The overall conclusion is that the potential application of this Pu-Be-based prompt in vivo NAA for the monitoring of the storage and retention of Gd in bone is not feasible.

Extracellular calcium controls the expression of two different forms of ripple-like hippocampal oscillations.

PubMed

Aivar, Paloma; Valero, Manuel; Bellistri, Elisa; Menendez de la Prida, Liset

2014-02-19

Hippocampal high-frequency oscillations (HFOs) are prominent in physiological and pathological conditions. During physiological ripples (100-200 Hz), few pyramidal cells fire together coordinated by rhythmic inhibitory potentials. In the epileptic hippocampus, fast ripples (>200 Hz) reflect population spikes (PSs) from clusters of bursting cells, but HFOs in the ripple and the fast ripple range are vastly intermixed. What is the meaning of this frequency range? What determines the expression of different HFOs? Here, we used different concentrations of Ca(2+) in a physiological range (1-3 mM) to record local field potentials and single cells in hippocampal slices from normal rats. Surprisingly, we found that this sole manipulation results in the emergence of two forms of HFOs reminiscent of ripples and fast ripples recorded in vivo from normal and epileptic rats, respectively. We scrutinized the cellular correlates and mechanisms underlying the emergence of these two forms of HFOs by combining multisite, single-cell and paired-cell recordings in slices prepared from a rat reporter line that facilitates identification of GABAergic cells. We found a major effect of extracellular Ca(2+) in modulating intrinsic excitability and disynaptic inhibition, two critical factors shaping network dynamics. Moreover, locally modulating the extracellular Ca(2+) concentration in an in vivo environment had a similar effect on disynaptic inhibition, pyramidal cell excitability, and ripple dynamics. Therefore, the HFO frequency band reflects a range of firing dynamics of hippocampal networks.

Conversion of Biowaste Asian Hard Clam (Meretrix lusoria) Shells into White-Emitting Phosphors for Use in Neutral White LEDs

PubMed Central

Chang, Tsung-Yuan; Wang, Chih-Min; Lin, Tai-Yuan; Lin, Hsiu-Mei

2016-01-01

The increasing volume and complexity of waste associated with the modern economy poses a serious risk to ecosystems and human health. However, the remanufacturing and recycling of waste into usable products can lead to substantial resource savings. In the present study, clam shell waste was first transformed into pure and well-crystallized single-phase white light-emitting phosphor Ca9Gd(PO4)7:Eu2+,Mn2+ materials. The phosphor Ca9Gd(PO4)7:Eu2+,Mn2+ materials were synthesized by the solid-state reaction method and the carbothermic reduction process, and then characterized and analyzed by means of X-ray diffraction (XRD) and photoluminescence (PL) measurements. The structural and luminescent properties of the phosphors were investigated as well. The PL and quantum efficiency measurements showed that the luminescence properties of clam shell-based phosphors were comparable to that of the chemically derived phosphors. Moreover, white light-emitting diodes were fabricated through the integration of 380 nm chips and single-phase white light-emitting phosphors (Ca0.979Eu0.006Mn0.015)9Gd(PO4)7 into a single package of a white light emitting diode (WLED) emitting a neutral white light of 5298 K with color coordinates of (0.337, 0.344). PMID:28774101

Retinoic acid stimulation of human dermal fibroblast proliferation is dependent on suboptimal extracellular Ca2+ concentration.

PubMed Central

Varani, J.; Shayevitz, J.; Perry, D.; Mitra, R. S.; Nickoloff, B. J.; Voorhees, J. J.

1990-01-01

Human dermal fibroblasts failed to proliferate when cultured in medium containing 0.15 mmol/l (millimolar) Ca2+ (keratinocyte growth medium [KGM]) but did when the external Ca2+ concentration was raised to 1.4 mmol/l. All-trans retinoic acid (retinoic acid) stimulated proliferation in KGM but did not further stimulate growth in Ca2(+)-supplemented KGM. The ability of retinoic acid to stimulate proliferation was inhibited in KGM prepared without Ca2+ or prepared with 0.03 mmol/l Ca2+ and in KGM treated with 1 mmol/l ethylene-glycol-bis-(beta-aminoethyl ether)N,N'-tetra acetic acid. Using 45Ca2+ to measure Ca2+ influx and efflux, it was found that retinoic acid minimally increased Ca2+ uptake into fibroblasts. In contrast, retinoic acid treatment of fibroblasts that had been pre-equilibrated for 1 day with 45Ca2+ inhibited release of intracellular Ca2+ into the extracellular fluid. Retinoic acid also stimulated 35S-methionine incorporation into trichloroacetic acid-precipitable material but in contrast to its effect on proliferation, stimulation of 35S-methionine incorporation occurred in both high-Ca2+ and low-Ca2+ medium. These data indicate that retinoic acid stimulation of proliferation, but not protein synthesis, is dependent on the concentration of Ca2+ in the extracellular environment. PMID:2356860

Response of hippocampal mossy fiber zinc to excessive glutamate release.

PubMed

Takeda, Atsushi; Minami, Akira; Sakurada, Naomi; Nakajima, Satoko; Oku, Naoto

2007-01-01

The response of hippocampal mossy fiber zinc to excessive glutamate release was examined to understand the role of the zinc in excessive excitation in the hippocampus. Extracellular zinc and glutamate concentrations during excessive stimulation with high K(+) were compared between the hippocampal CA3 and CA1 by the in vivo microdialysis. Zinc concentration in the CA3 was more increased than that in the CA1, while glutamate concentration in the CA3 was less increased than that in the CA1. It is likely that more increase in extracellular zinc is linked with less increase in extracellular glutamate in the CA3. To see zinc action in mossy fiber synapses during excessive excitation, furthermore, 1mM glutamate was regionally delivered to the stratum lucidum in the presence of zinc or CaEDTA, a membrane-impermeable zinc chelator, and intracellular calcium signal was measured in the CA3 pyramidal cell layer. The persistent increase in calcium signal during stimulation with glutamate was significantly attenuated in the presence of 100 microM zinc, while significantly enhanced in the presence of 1mM CaEDTA. These results suggest that zinc released from mossy fibers attenuates the increase in intracellular calcium signal in mossy fiber synapses and postsynaptic CA3 neurons after excessive inputs to dentate granular cells.

Further characterization of [3H]gamma-aminobutyric acid release from isolated neuronal growth cones: role of intracellular Ca2+ stores.

PubMed

Lockerbie, R O; Gordon-Weeks, P R

1986-04-01

We have recently shown that growth cones isolated from neonatal rat forebrain possess uptake and release mechanisms for the neurotransmitter gamma-aminobutyric acid. About half of the K+-induced release of [3H]gamma-aminobutyric acid from isolated growth cones is dependent on extracellular Ca2+. The remaining component of the [3H]gamma-aminobutyric acid release is unaffected by removal of extracellular Ca2+ and is resistant to blockade by the voltage-sensitive Ca2+-channel blocker methoxyverapamil. In the present series of experiments we have used caffeine to assess the possible role of intracellular stores of Ca2+ in supporting that component of the K+-induced release of [3H]gamma-aminobutyric acid from isolated growth cones that is independent of extracellular Ca2+. We have chosen caffeine because of its well established effect of releasing Ca2+ from smooth endoplasmic reticulum in muscle. We found that caffeine can release [3H]gamma-aminobutyric acid from isolated growth cones. This effect persists in Ca2+-free medium, in the presence of methoxyverapamil and in the absence of Na+. Furthermore, isobutylmethylxanthine could not substitute for caffeine suggesting that the caffeine effect is not due to phosphodiesterase inhibition and the subsequent rise in intracellular cyclic nucleotides. A combination of the mitochondrial poisons, Antimycin A and sodium azide had no effect on the release of [3H]gamma-aminobutyric acid induced either by caffeine or by high K+. We conclude that caffeine causes the release of Ca2+ from a non-mitochondrial store within the growth cone and that this Ca2+ store supports that component of the K+-induced release of [3H]gamma-aminobutyric acid that is independent of extracellular Ca2+.

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.

Synthesis and characterization of a smart contrast agent sensitive to calcium.

PubMed

Dhingra, Kirti; Maier, Martin E; Beyerlein, Michael; Angelovski, Goran; Logothetis, Nikos K

2008-08-07

A novel first-generation Ca2+ sensitive contrast agent, Gd-DOPTRA has been synthesized and characterized. The agent shows approximately 100% relaxivity enhancement upon addition of Ca2+. The agent is selective and sensitive to Ca2+ also in the presence of Mg2+ and Zn2+. The relaxivity studies carried out in physiological fluids prove the prospects of the agent for in vivo measurements.

Diode-pumped Kerr-lens mode-locked Yb:CaGdAlO4 laser with tunable wavelength

NASA Astrophysics Data System (ADS)

Gao, Ziye; Zhu, Jiangfeng; Wang, Junli; Wang, Zhaohua; Wei, Zhiyi; Xu, Xiaodong; Zheng, Lihe; Su, Liangbi; Xu, Jun

2016-01-01

We experimentally demonstrated a wavelength tunable Kerr-lens mode-locked femtosecond laser based on an Yb:CaGdAlO4 (Yb:CGA) crystal. The Kerr-lens mode-locked wavelength tuning range was from 1043.5 to 1076 nm, as broad as 32.5 nm, by slightly tilting the end mirror. Pulses as short as 60 fs were generated at the central wavelength of 1043.8 nm with an average output power of 66 mW. By using an output coupler with 1.5% transmittance, the Kerr-lens mode-locked average output power reached 127 mW with a pulse duration of 81 fs at a central wavelength of 1049.5 nm.

Effect of ca+2 addition on the properties of ce0.8gd0.2o2-δ for it-sofc

NASA Astrophysics Data System (ADS)

Koteswararao, P.; Buchi Suresh, M.; Wani, B. N.; Bhaskara Rao, P. V.; Varalaxmi, P.

2018-03-01

This paper reports the effect of Ca2+ addition on the structural and electrical properties of Ce0.8Gd0.2O2-δ(GDC) electrolyte for low temperature solid oxide fuel cell application. The Ca (0, 0.5, 1 and 2 mol %) doped GDC solid electrolytes have been prepared by solid state method. The sintered densities of the samples are greater than 95%. XRD study reveals the cubic fluorite structure. The microstructure of the samples sintered at 1400°C resulted into grain sizes in the range of 1.72 to 10.20 μm. Raman spectra show the presence of GDC single phase. AC impedance analysis is used to measure the ionic conductivity of the electrolyte. Among all the compositions, the highest conductivity is observed in the GDC sample with 0.5 mol% Ca addition. Nyquist plots resulted in multiple redoxation process such as grain and grain boundary conductions to final conductivity. Estimated blocking factor is lower for the GDC electrolyte with 0.5mol% Ca, indicating that Ca addition was promoted grain boundary conduction. Activation energies were calculated from Arrhenius plot and are found in the range of 1eV.

Molecular mechanism of pancreatic tumor metastasis inhibition by Gd@C 82(OH) 22 and its implication for de novo design of nanomedicine

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

Kang, S. -g.; Zhou, G.; Yang, P.

2012-09-18

Pancreatic adenocarcinoma is the most lethal of the solid tumors and the fourth-leading cause of cancer-related death in North America. Matrix metalloproteinases (MMPs) have long been targeted as a potential anticancer therapy because of their seminal role in angiogenesis and extracellular matrix (ECM) degradation of tumor survival and invasion. However, the inhibition specificity to MMPs and the molecular-level understanding of the inhibition mechanism remain largely unresolved. Here, we found that endohedral metallofullerenol Gd@C 82(OH) 22 can successfully inhibit the neoplastic activity with experiments at animal, tissue, and cellular levels. Gd@C 82(OH) 22 effectively blocks tumor growth in human pancreatic cancermore » xenografts in a nude mouse model. Enzyme activity assays also show Gd@C 82(OH) 22 not only suppresses the expression of MMPs but also significantly reduces their activities. We then applied large-scale molecular-dynamics simulations to illustrate the molecular mechanism by studying the Gd@C 82(OH) 22–MMP-9 interactions in atomic detail. Our data demonstrated that Gd@C 82(OH) 22 inhibits MMP-9 mainly via an exocite interaction, whereas the well-known zinc catalytic site only plays a minimal role. Steered by nonspecific electrostatic, hydrophobic, and specific hydrogen-bonding interactions, Gd@C 82(OH) 22 exhibits specific binding modes near the ligand-specificity loop S1', thereby inhibiting MMP-9 activity. Both the suppression of MMP expression and specific binding mode make Gd@C 82(OH) 22 a potentially more effective nanomedicine for pancreatic cancer than traditional medicines, which usually target the proteolytic sites directly but fail in selective inhibition. Finally, our findings provide insights for de novo design of nanomedicines for fatal diseases such as pancreatic cancer.« less

Health economic evaluation of Gd-EOB-DTPA MRI vs ECCM-MRI and multi-detector computed tomography in patients with suspected hepatocellular carcinoma in Thailand and South Korea.

PubMed

Lee, Jeong-Min; Kim, Myeong-Jin; Phongkitkarun, Sith; Sobhonslidsuk, Abhasnee; Holtorf, Anke-Peggy; Rinde, Harald; Bergmann, Karsten

2016-08-01

The effectiveness of treatment decisions and economic outcomes of using gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging (Gd-EOB-DTPA-MRI) were compared with extracellular contrast media-enhanced MRI (ECCM-MRI) and multi-detector computed tomography (MDCT) as initial procedures in patients with suspected hepatocellular carcinoma (HCC) in South Korea and Thailand. A decision-tree model simulated the clinical pathway for patients with suspected HCC from the first imaging procedure to a confirmed treatment decision. Input data (probabilities and resource consumptions) were estimated and validated by clinical experts. Costs for diagnostic alternatives and related treatment options were derived from published sources, taking into account both payer's and hospital's perspectives. All experts from Korea and Thailand agreed that Gd-EOB-DTPA-MRI yields the highest diagnostic certainty and minimizes the need for additional confirmatory diagnostic procedures in HCC. In Korea, from the payer's perspective, total cost was USD $3087/patient to reach a confirmed treatment decision using Gd-EOB-DTPA-MRI (vs $3205/patient for MDCT and $3403/patient for ECCM-MRI). From the hospital's perspective, Gd-EOB-DTPA-MRI incurred the lowest cost ($2289/patient vs $2320/patient and $2528/patient, respectively). In Thailand, Gd-EOB-DTPA-MRI was the least costly alternative for the payer ($702/patient vs $931/patient for MDCT and $873/patient for ECCM-MRI). From the hospital's perspective, costs were $1106/patient, $1178/patient, and $1087/patient for Gd-EOB-DTPA-MRI, MDCT, and ECCM-MRI, respectively. Gd-EOB-DTPA-MRI as an initial imaging procedure in patients with suspected HCC provides better diagnostic certainty and relevant statutory health insurance cost savings in Thailand and Korea, compared with ECCM-MRI and MDCT.

Ionic and secretory response of pancreatic islet cells to minoxidil sulfate

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

Antoine, M.H.; Hermann, M.; Herchuelz, A.

Minoxidil sulfate is an antihypertensive agent belonging to the new class of vasodilators, the K+ channel openers. The present study was undertaken to characterize the effects of minoxidil sulfate on ionic and secretory events in rat pancreatic islets. The drug unexpectedly provoked a concentration-dependent decrease in 86Rb outflow. This inhibitory effect was reduced in a concentration-dependent manner by glucose and tolbutamide. Minoxidil sulfate did not affect 45Ca outflow from islets perfused in the presence of extracellular Ca++ and absence or presence of glucose. However, in islets exposed to a medium deprived of extracellular Ca++, the drug provoked a rise inmore » 45Ca outflow. Whether in the absence or presence of extracellular Ca++, minoxidil sulfate increased the cytosolic free Ca++ concentration of islet cells. Lastly, minoxidil sulfate increased the release of insulin from glucose-stimulated pancreatic islets. These results suggest that minoxidil sulfate reduces the activity of the ATP-sensitive K+ channels and promotes an intracellular translocation of Ca++. The latter change might account for the effect of the drug on the insulin-releasing process. However, the secretory response to minoxidil sulfate could also be mediated, at least in part, by a modest Ca++ entry.« less

Calcium Dependence of Settlement and Nematocyst Discharge in Actinulae of the Hydroid Tubularia mesembryanthemum.

PubMed

Kawaii, S; Yamashita, K; Nakai, M; Takahashi, M; Fusetani, N

1999-02-01

The influence of Ca2+ and Mg2+ ions on both atrichous isorhiza (AI) discharge and settlement of actinular larvae of the hydroid Tubularia mesembryanthemum was investigated. Mg2+-supplemented artificial seawater (ASW) completely inhibited both events at a concentration of 206 mM, whereas lowered Mg2+ concentrations enhanced them. Ca2+ ions in the bathing solution highly regulated AI discharge and settlement, and Mg2+ ions may down-regulate these events. The effect of inorganic Ca2+-channel blockers, including Gd3+ and La3+, was also examined. Larval settlement was inhibited by Co2+, Ni2+, Cd2+, La3+, and Gd3+, with half inhibitory concentrations (IC50) of 5800, 260, 53, 45, and 7 {mu}M, respectively; AI discharge was also inhibited by these ions, with IC50 values of 6600, 500, 78, 41, and 5 {mu}M, respectively. These results suggest possible involvement of stretch-activated Ca2+ channels in the signal transmission of both AI discharge and larval settlement. Copyright © 1999 by Marine Biological Laboratory.

Microchip Yb:CaLnAlO4 lasers with up to 91% slope efficiency.

PubMed

Loiko, Pavel; Serres, Josep Maria; Mateos, Xavier; Xu, Xiaodong; Xu, Jun; Jambunathan, Venkatesan; Navratil, Petr; Lucianetti, Antonio; Mocek, Tomas; Zhang, Xuzhao; Griebner, Uwe; Petrov, Valentin; Aguiló, Magdalena; Díaz, Francesc; Major, Arkady

2017-07-01

Multi-watt continuous-wave (CW) operation of tetragonal rare-earth calcium aluminate Yb:CaLnAlO 4 (Ln=Gd,Y)) crystals in plano-plano microchip lasers was demonstrated with an almost quantum-defect-limited slope efficiency. Pumped at 978 nm by an InGaAs laser diode, a 3.4 mm long 8 at. % Yb:CaGdAlO 4 laser generated 7.79 W at 1057-1065 nm with a slope efficiency of η=84% (with respect to the absorbed pump power). An even higher η=91% was achieved with a 2.5 mm long 3 at. % Yb:CaYAlO 4 laser, from which 5.06 W were extracted at 1048-1056 nm. Both lasers produced linearly polarized output (σ-polarization) with an almost circular diffraction-limited beam (Mx,y2<1.1). The output performance of the developed lasers was modeled, yielding an internal loss coefficient as low as 0.004-0.007  cm -1 . In addition, their spectroscopic properties were revisited.

Vasodilatory effects of ethanol extract of Radix Paeoniae Rubra and its mechanism of action in the rat aorta.

PubMed

Jin, Song Nan; Wen, Jin Fu; Wang, Ting Ting; Kang, Dae Gill; Lee, Ho Sub; Cho, Kyung Woo

2012-06-26

Radix Paeoniae Rubra (RPR) is an important traditional Chinese medicine (TCM) commonly used in clinic for a long history in China. RPR is the radix of either Paeonia lactiflora Pall. or Paeonia veitchii Lynch. RPR has a wide variety of pharmacological actions such as anti-thrombus, anti-coagulation, and anti-atherosclerotic properties, protecting heart and liver. However, the mechanisms involved are to be defined. The aim of the present study was to define the effect of Paeonia lactiflora Pall. extracts on vascular tension and responsible mechanisms in rat thoracic aortic rings. Ethanol extract of Paeonia lactiflora Pall. (EPL) was examined for their vascular relaxant effects in isolated phenylephrine-precontracted rat thoracic aorta. EPL induced relaxation of the phenylephrine-precontracted aortic rings in a concentration-dependent manner. Vascular relaxation induced by EPL was significantly inhibited by removal of the endothelium or pretreatment of the rings with N(G)-nitro-L-arginine methylester (L-NAME) or 1H-[1,2,4]-oxadiazolo-[4,3-α]-quinoxalin-1-one (ODQ). Extracellular Ca²⁺ depletion or diltiazem significantly attenuated EPL-induced vasorelaxation. Modulators of the store-operated Ca²⁺ entry (SOCE), thapsigargin, 2-aminoethyl diphenylborinate and Gd³⁺, and an inhibitor of Akt, wortmannin, markedly attenuated the EPL-induced vasorelaxation. Further, the EPL-induced vasorelaxation was significantly attenuated by pretreatment with tetraethylammonium, a non-selective K(Ca) channels blocker, or glibenclamide, an ATP-sensitive K⁺ channels inhibitor, respectively. Inhibition of cyclooxygenases with indomethacin, and adrenergic and muscarinic receptors blockade had no effects on the EPL-induced vasorelaxation. The present study suggests that EPL relaxes vascular smooth muscle via endothelium-dependent and Akt- and SOCE-eNOS-cGMP-mediated pathways through activation of both K(Ca) and K(ATP) channels and inhibition of L-type Ca²⁺ channels. Copyright © 2012. Published by Elsevier Ireland Ltd.

Increased extracellular and intracellular Ca{sup 2+} lead to adipocyte accumulation in bone marrow stromal cells by different mechanisms

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

Hashimoto, Ryota, E-mail: hryota@juntendo.ac.jp; Katoh, Youichi, E-mail: katoyo@juntendo-urayasu.jp; Department of Cardiology, Juntendo University Faculty of Medicine, Hongo 2-1-1, Bunkyo-ku, Tokyo 113-8421

2015-02-20

Mesenchymal stem cells found in bone marrow stromal cells (BMSCs) are the common progenitors for both adipocyte and osteoblast. An increase in marrow adipogenesis is associated with age-related osteopenia and anemia. Both extracellular and intracellular Ca{sup 2+} ([Ca{sup 2+}]{sub o} and [Ca{sup 2+}]{sub i}) are versatile signaling molecules that are involved in the regulation of cell functions, including proliferation and differentiation. We have recently reported that upon treatment of BMSCs with insulin and dexamethasone, both high [Ca{sup 2+}]{sub o} and high [Ca{sup 2+}]{sub i} enhanced adipocyte accumulation, which suggested that increases in [Ca{sup 2+}]{sub o} caused by bone resorption maymore » accelerate adipocyte accumulation in aging and diabetic patients. In this study, we used primary mouse BMSCs to investigate the mechanisms by which high [Ca{sup 2+}]{sub o} and high [Ca{sup 2+}]{sub i} may enhance adipocyte accumulation. In the process of adipocyte accumulation, two important keys are adipocyte differentiation and the proliferation of BMSCs, which have the potential to differentiate into adipocytes. Use of MTT assay and real-time RT-PCR revealed that high [Ca{sup 2+}]{sub i} (ionomycin)-dependent adipocyte accumulation is caused by enhanced proliferation of BMSCs but not enhanced differentiation into adipocytes. Using fura-2 fluorescence-based approaches, we showed that high [Ca{sup 2+}]{sub o} (addition of CaCl{sub 2}) leads to increases in [Ca{sup 2+}]{sub i}. Flow cytometric methods revealed that high [Ca{sup 2+}]{sub o} suppressed the phosphorylation of ERK independently of intracellular Ca{sup 2+}. The inhibition of ERK by U0126 and PD0325901 enhanced the differentiation of BMSCs into adipocytes. These data suggest that increased extracellular Ca{sup 2+} provides the differentiation of BMSCs into adipocytes by the suppression of ERK activity independently of increased intracellular Ca{sup 2+}, which results in BMSC proliferation. - Highlights: • Both high [Ca{sup 2+}]{sub o} and high [Ca{sup 2+}]{sub i} enhanced adipocyte accumulation in BMSCs. • High [Ca{sup 2+}]{sub i} enhanced the proliferation of BMSCs but not adipocyte differentiation. • High [Ca{sup 2+}]{sub o} suppressed the phosphorylation of ERK in BMSCs. • Inhibition of ERK enhanced the differentiation of BMSCs into adipocytes. • High [Ca{sup 2+}]{sub o}-mediated suppression of ERK may be a new therapy target for anemia.« less

Differences in magnesium and calcium effects on N-methyl-D-aspartate- and quisqualate-induced decreases in extracellular sodium concentration in rat hippocampal slices.

PubMed

Köhr, G; Heinemann, U

1988-01-01

Decreases in extracellular sodium concentration [( Na+]o) and associated slow negative field potentials (fp's) were monitored with double barreled sodium sensitive/reference microelectrodes in area CA1 of rat hippocampal slices during iontophoretic application of the glutamate receptor agonists N-methyl-D-aspartate (NMDA) and quisqualate (quis). The effects of lowering [Ca2+]o on these signals were compared to those of lowering [Mg2+]o. Both NMDA- and quis-induced decreases in [Na+]o of up to 60 mM and in the fp's of up to 8 mV. Decreasing [Mg2+]o enhanced NMDA-induced signals, whereas quis-induced signals were unaffected. Lowering [Ca2+]o also enhanced NMDA signals, although somewhat less than lowering [Mg2+]o. This effect was still present, even when voltage dependent Na+ currents were blocked by 10(-7) tetrodotoxin. Interestingly, quis-induced signals could be enhanced in a low Ca2+ medium as well, but only when high quis concentrations were used. The results suggest that, during the sorts of large decreases of [Ca2+]o observed during seizure activity, activation of NMDA receptors is facilitated.

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

PubMed

Bonnet, Mariette; Tran Van Nhieu, Guy

2016-01-01

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

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

PubMed Central

Bonnet, Mariette; Tran Van Nhieu, Guy

2016-01-01

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

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

PubMed Central

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

2013-01-01

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

ATP activates P2x receptors and requires extracellular Ca(++) participation to modify outer hair cell nonlinear capacitance.

PubMed

Yu, Ning; Zhao, Hong-Bo

2008-11-01

Intracochlear ATP is an important mediator in regulating hearing function. ATP can activate ionotropic purinergic (P2x) and metabotropic purinergic (P2y) receptors to influence cell functions. In this paper, we report that ATP can activate P2x receptors directly to modify outer hair cell (OHC) electromotility, which is an active cochlear amplifier determining hearing sensitivity and frequency selectivity in mammals. We found that ATP, but not UTP, a P2y receptor agonist, reduced the OHC electromotility-associated nonlinear capacitance (NLC) and shifted its voltage dependence to the right (depolarizing) direction. Blockage of the activation of P2x receptors by pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), suramin, and 4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid (DIDS) could block the ATP effect. This modification also required extracellular Ca(++) participation. Removal of extracellular Ca(++) abolished the ATP effect. However, chelation of intracellular Ca(++) concentration by a fast calcium-chelating reagent 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA, 10 mM) did not affect the effect of ATP on NLC. The effect is also independent of K(+) ions. Substitution of Cs(+) for intracellular or extracellular K(+) did not affect the ATP effect. Our findings indicate that ATP activates P2x receptors instead of P2y receptors to modify OHC electromotility. Extracellular Ca(++) is required for this modification.

Structural mechanism of ligand activation in human calcium-sensing receptor

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

Geng, Yong; Mosyak, Lidia; Kurinov, Igor

2016-07-19

Human calcium-sensing receptor (CaSR) is a G-protein-coupled receptor (GPCR) that maintains extracellular Ca 2+homeostasis through the regulation of parathyroid hormone secretion. It functions as a disulfide-tethered homodimer composed of three main domains, the Venus Flytrap module, cysteine-rich domain, and seven-helix transmembrane region. Here, we present the crystal structures of the entire extracellular domain of CaSR in the resting and active conformations. We provide direct evidence that L-amino acids are agonists of the receptor. In the active structure, L-Trp occupies the orthosteric agonist-binding site at the interdomain cleft and is primarily responsible for inducing extracellular domain closure to initiate receptor activation.more » Our structures reveal multiple binding sites for Ca 2+and PO 4 3-ions. Both ions are crucial for structural integrity of the receptor. While Ca 2+ions stabilize the active state, PO 4 3-ions reinforce the inactive conformation. The activation mechanism of CaSR involves the formation of a novel dimer interface between subunits.« less

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

DOE PAGES

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

2014-10-17

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

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

NASA Astrophysics Data System (ADS)

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

2014-10-01

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

Extracellular acidosis selectively inhibits pharmacomechanical coupling induced by carbachol in strips of rat gastric fundus.

PubMed

de Oliveira, Daniel Maia Nogueira; Batista-Lima, Francisco José; de Carvalho, Emanuella Feitosa; Havt, Alexandre; da Silva, Moisés Tolentino Bento; Dos Santos, Armênio Aguiar; Magalhães, Pedro Jorge Caldas

2017-12-01

What is the central question of this study? Acute acidosis that results from short-term exercise is involved in delayed gastric emptying in rats and the lower responsiveness of gastric fundus strips to carbachol. Does extracellular acidosis decrease responsiveness to carbachol in tissues of sedentary rats? How? What is the main finding and its importance? Extracellular acidosis inhibits cholinergic signalling in the rat gastric fundus by selectively influencing the G q/11 protein signalling pathway. Acute acidosis that results from short-term exercise delays gastric emptying in rats and decreases the responsiveness to carbachol in gastric fundus strips. The regulation of cytosolic Ca 2+ concentrations appears to be a mechanism of action of acidosis. The present study investigated the way in which acidosis interferes with gastric smooth muscle contractions. Rat gastric fundus isolated strips at pH 6.0 presented a lower magnitude of carbachol-induced contractions compared with preparations at pH 7.4. This lower magnitude was absent in carbachol-stimulated duodenum and KCl-stimulated gastric fundus strips. In Ca 2+ -free conditions, repeated contractions that were induced by carbachol progressively decreased, with no influence of extracellular pH. In fundus strips, CaCl 2 -induced contractions were lower at pH 6.0 than at pH 7.4 but only when stimulated in the combined presence of carbachol and verapamil. In contrast, verapamil-sensitive contractions that were induced by CaCl 2 in the presence of KCl did not change with pH acidification. In Ca 2+ store-depleted preparations that were treated with thapsigargin, the contractions that were induced by extracellular Ca 2+ restoration were smaller at pH 6.0 than at pH 7.4, but relaxation that was induced by SKF-96365 (an inhibitor of store-operated Ca 2+ entry) was unaltered by extracellular acidification. At pH 6.0, the phospholipase C inhibitor U-73122 relaxed carbachol-induced contractions less than at pH 7.4, and this phenomenon was absent in tissue that was treated with the RhoA kinase blocker Y-27632. Thus, extracellular acidosis inhibited pharmacomechanical coupling in gastric fundus by selectively inhibiting the G q/11 protein signalling pathway, whereas electromechanical coupling remained functionally preserved. © 2017 The Authors. Experimental Physiology © 2017 The Physiological Society.

Calcium signaling in smooth muscle.

PubMed

Hill-Eubanks, David C; Werner, Matthias E; Heppner, Thomas J; Nelson, Mark T

2011-09-01

Changes in intracellular Ca(2+) are central to the function of smooth muscle, which lines the walls of all hollow organs. These changes take a variety of forms, from sustained, cell-wide increases to temporally varying, localized changes. The nature of the Ca(2+) signal is a reflection of the source of Ca(2+) (extracellular or intracellular) and the molecular entity responsible for generating it. Depending on the specific channel involved and the detection technology employed, extracellular Ca(2+) entry may be detected optically as graded elevations in intracellular Ca(2+), junctional Ca(2+) transients, Ca(2+) flashes, or Ca(2+) sparklets, whereas release of Ca(2+) from intracellular stores may manifest as Ca(2+) sparks, Ca(2+) puffs, or Ca(2+) waves. These diverse Ca(2+) signals collectively regulate a variety of functions. Some functions, such as contractility, are unique to smooth muscle; others are common to other excitable cells (e.g., modulation of membrane potential) and nonexcitable cells (e.g., regulation of gene expression).

Arabidopsis annexin1 mediates the radical-activated plasma membrane Ca²+- and K+-permeable conductance in root cells.

PubMed

Laohavisit, Anuphon; Shang, Zhonglin; Rubio, Lourdes; Cuin, Tracey A; Véry, Anne-Aliénor; Wang, Aihua; Mortimer, Jennifer C; Macpherson, Neil; Coxon, Katy M; Battey, Nicholas H; Brownlee, Colin; Park, Ohkmae K; Sentenac, Hervé; Shabala, Sergey; Webb, Alex A R; Davies, Julia M

2012-04-01

Plant cell growth and stress signaling require Ca²⁺ influx through plasma membrane transport proteins that are regulated by reactive oxygen species. In root cell growth, adaptation to salinity stress, and stomatal closure, such proteins operate downstream of the plasma membrane NADPH oxidases that produce extracellular superoxide anion, a reactive oxygen species that is readily converted to extracellular hydrogen peroxide and hydroxyl radicals, OH•. In root cells, extracellular OH• activates a plasma membrane Ca²⁺-permeable conductance that permits Ca²⁺ influx. In Arabidopsis thaliana, distribution of this conductance resembles that of annexin1 (ANN1). Annexins are membrane binding proteins that can form Ca²⁺-permeable conductances in vitro. Here, the Arabidopsis loss-of-function mutant for annexin1 (Atann1) was found to lack the root hair and epidermal OH•-activated Ca²⁺- and K⁺-permeable conductance. This manifests in both impaired root cell growth and ability to elevate root cell cytosolic free Ca²⁺ in response to OH•. An OH•-activated Ca²⁺ conductance is reconstituted by recombinant ANN1 in planar lipid bilayers. ANN1 therefore presents as a novel Ca²⁺-permeable transporter providing a molecular link between reactive oxygen species and cytosolic Ca²⁺ in plants.

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.

Dual-color quantum dot detection of a heterotetrameric potassium channel (hKCa3.1).

PubMed

Waschk, Daniel E J; Fabian, Anke; Budde, Thomas; Schwab, Albrecht

2011-04-01

Potassium channels play a key role in establishing the cell membrane potential and are expressed ubiquitously. Today, more than 70 mammalian K(+) channel genes are known. The diversity of K(+) channels is further increased by the fact that different K(+) channel family members may assemble to form heterotetramers. We present a method based on fluorescence microscopy to determine the subunit composition of a tetrameric K(+) channel. We generated artificial "heteromers" of the K(+) channel hK(Ca)3.1 by coexpressing two differently tagged hK(Ca)3.1 constructs containing either an extracellular hemagglutinin (HA) or an intracellular V5 epitope. hK(Ca)3.1 channel subunits were detected in the plasma membrane of MDCK-F cells or HEK293 cells by labeling the extra- and intracellular epitopes with differently colored quantum dots (QDs). As previously shown for the extracellular part of hK(Ca)3.1 channels, its intracellular domain can also bind only one QD label at a time. When both channel subunits were coexpressed, 27.5 ± 1.8% and 24.9 ± 2.1% were homotetramers consisting of HA- and V5-tagged subunits, respectively. 47.6 ± 3.2% of the channels were heteromeric and composed of both subunits. The frequency distribution of HA- and V5-tagged homo- and heteromeric hK(Ca)3.1 channels is reminiscent of the binomial distribution (a + b)(2) = a(2) + 2ab + b(2). Along these lines, our findings are consistent with the notion that hK(Ca)3.1 channels are assembled from two homomeric dimers and not randomly from four independent subunits. We anticipate that our technique will be applicable to other heteromeric membrane proteins, too.

Strained enabled Ferroelectricity in CaTiO3 Thin Films Probed by Nonlinear Optics and Scanning Probe Microscopy

NASA Astrophysics Data System (ADS)

Vlahos, Eftihia; Kumar, Amit; Denev, Sava; Brooks, Charles; Schlom, Darrell; Eklund, Carl-Johan; Rabe, Karin M.; Fennie, Craig J.; Gopalan, Venkatraman

2009-03-01

Calcium titanate, CaTiO3 is not a ferroelectric in its bulk form. However, first principles calculations predict that biaxially tensile strained CaTiO3 thin films should become ferroelectric. Here, we indeed confirm that strained CaTiO3 films become ferroelectric with a Curie temperature of ˜125K. Optical second harmonic generation (SHG) measurements, polarization studies, and in-situ electric-field measurements for a number of films with different strain values will be presented: CaTiO3/DyScO3(110), CaTiO3/SrTiO3 (100),CaTiO3/GdScO3/NdGaO3(110), CaTiO3/LaSrAlO3(001) as well as for a single crystal CaTiO3. From these studies, we conclude that strained CaTiO3 films are ferroelectric with a point group symmetry of mm2, and show reversible domain switching characteristics under an electric field. We also present results of variable temperature piezoelectric force microscopy for imaging the polar domains in the ferroelectric phase. These results suggest that strain is a valuable tool for inducing polar, long range ferroelectric order in even non-polar ceramic materials such as CaTiO3.

Nutrient intakes and iron and vitamin D status differ depending on main milk consumed by UK children aged 12-18 months - secondary analysis from the Diet and Nutrition Survey of Infants and Young Children.

PubMed

Sidnell, Anne; Pigat, Sandrine; Gibson, Sigrid; O'Connor, Rosalyn; Connolly, Aileen; Sterecka, Sylwia; Stephen, Alison M

2016-01-01

Nutrition in the second year is important as this is a period of rapid growth and development. Milk is a major food for young children and this analysis evaluated the impact of the type of milk consumed on nutrient intakes and nutritional status. Data from the Diet and Nutrition Survey of Infants and Young Children were used to investigate the intakes of key nutrients, and Fe and vitamin D status, of children aged 12-18 months, not breastfed, and consuming >400 g/d fortified milk (n 139) or >400 g/d of whole cows' milk (n 404). Blood samples from eligible children for measurement of Hb (n 113), serum ferritin and plasma 25-hydroxyvitamin D (25(OH)D) concentrations (n 105) were available for approximately 20 % of children. Unpaired Mann-Whitney tests were used to compare nutrient intakes and status between consumers of fortified and cows' milk. Mean daily total dietary intakes of Fe, Zn, vitamin A and vitamin D were significantly higher in the fortified milk group. Mean daily total dietary intakes of energy, protein, Ca, iodine, Na and saturated fat were significantly higher in the cows' milk group. Hb was not different between groups. The fortified milk group had significantly higher serum ferritin (P = 0·049) and plasma 25(OH)D (P = 0·014). This analysis demonstrates significantly different nutrient intakes and status between infants consuming >400 g/d fortified milk v. those consuming >400 g/d whole cows' milk. These results indicate that fortified milks can play a significant role in improving the quality of young children's diets in their second year of life.

Crystal structure of the ternary silicide Gd2Re3Si5.

PubMed

Fedyna, Vitaliia; Kozak, Roksolana; Gladyshevskii, Roman

2014-12-01

A single crystal of the title compound, the ternary silicide digadolinium trirhenium penta-silicide, Gd2Re3Si5, was isolated from an alloy of nominal composition Gd20Re30Si50 synthesized by arc melting and investigated by X-ray single-crystal diffraction. Its crystal structure belongs to the U2Mn3Si5 structure type. All atoms in the asymmetric lie on special positions. The Gd site has site symmetry m..; the two Mn atoms have site symmetries m.. and 2.22; the three Si atoms have site symmetries m.., ..2 and 4.. . The coordination polyhedra of the Gd atoms have 21 vertices, while those of the Re atoms are cubo-octa-hedra and 13-vertex polyhedra. The Si atoms are arranged as tricapped trigonal prisms, bicapped square anti-prisms, or 11-vertex polyhedra. The crystal structure of the title compound is also related to the structure types CaBe2Ge2 and W5Si3. It can be represented as a stacking of Gd-centred polyhedra of composition [GdSi9]. The Re atoms form infinite chains with an Re-Re distance of 2.78163 (5) Å and isolated squares with an Re-Re distance of 2.9683 (6) Å.

Crystal structure of the ternary silicide Gd2Re3Si5

PubMed Central

Fedyna, Vitaliia; Kozak, Roksolana; Gladyshevskii, Roman

2014-01-01

A single crystal of the title compound, the ternary silicide digadolinium trirhenium penta­silicide, Gd2Re3Si5, was isolated from an alloy of nominal composition Gd20Re30Si50 synthesized by arc melting and investigated by X-ray single-crystal diffraction. Its crystal structure belongs to the U2Mn3Si5 structure type. All atoms in the asymmetric lie on special positions. The Gd site has site symmetry m..; the two Mn atoms have site symmetries m.. and 2.22; the three Si atoms have site symmetries m.., ..2 and 4.. . The coordination polyhedra of the Gd atoms have 21 vertices, while those of the Re atoms are cubo­octa­hedra and 13-vertex polyhedra. The Si atoms are arranged as tricapped trigonal prisms, bicapped square anti­prisms, or 11-vertex polyhedra. The crystal structure of the title compound is also related to the structure types CaBe2Ge2 and W5Si3. It can be represented as a stacking of Gd-centred polyhedra of composition [GdSi9]. The Re atoms form infinite chains with an Re—Re distance of 2.78163 (5) Å and isolated squares with an Re—Re distance of 2.9683 (6) Å. PMID:25552967

Gd-labeled glycol chitosan as a pH-responsive magnetic resonance imaging agent for detecting acidic tumor microenvironments.

PubMed

Nwe, Kido; Huang, Ching-Hui; Tsourkas, Andrew

2013-10-24

Neoplastic lesions can create a hostile tumor microenvironment with low extracellular pH. It is commonly believed that these conditions can contribute to tumor progression as well as resistance to therapy. We report the development and characterization of a pH-responsive magnetic resonance imaging contrast agent for imaging the acidic tumor microenvironment. The preparation included the conjugation of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid 1-(2,5-dioxo-1-pyrrolidinyl) ester (DOTA-NHS) to the surface of a water-soluble glycol chitosan (GC) polymer, which contains pH-titrable primary amines, followed by gadolinium complexation (GC-NH2-GdDOTA). GC-NH2-GdDOTA had a chelate-to-polymer ratio of approximately1:24 and a molar relaxivity of 9.1 mM(-1) s(-1). GC-NH2-GdDOTA demonstrated pH-dependent cellular association in vitro compared to the control. It also generated a 2.4-fold enhancement in signal in tumor-bearing mice 2 h postinjection. These findings suggest that glycol chitosan coupled with contrast agents can provide important diagnostic information about the tumor microenvironment.

Influence of Calcium in Extracellular DNA Mediated Bacterial Aggregation and Biofilm Formation

PubMed Central

Koop, Leena; Wong, Yie Kuan; Ahmed, Safia; Siddiqui, Khawar Sohail; Manefield, Mike

2014-01-01

Calcium (Ca2+) has an important structural role in guaranteeing the integrity of the outer lipopolysaccharide layer and cell walls of bacterial cells. Extracellular DNA (eDNA) being part of the slimy matrix produced by bacteria promotes biofilm formation through enhanced structural integrity of the matrix. Here, the concurrent role of Ca2+ and eDNA in mediating bacterial aggregation and biofilm formation was studied for the first time using a variety of bacterial strains and the thermodynamics of DNA to Ca2+ binding. It was found that the eDNA concentrations under both planktonic and biofilm growth conditions were different among bacterial strains. Whilst Ca2+ had no influence on eDNA release, presence of eDNA by itself favours bacterial aggregation via attractive acid-base interactions in addition, its binding with Ca2+ at biologically relevant concentrations was shown further increase in bacterial aggregation via cationic bridging. Negative Gibbs free energy (ΔG) values in iTC data confirmed that the interaction between DNA and Ca2+ is thermodynamically favourable and that the binding process is spontaneous and exothermic owing to its highly negative enthalpy. Removal of eDNA through DNase I treatment revealed that Ca2+ alone did not enhance cell aggregation and biofilm formation. This discovery signifies the importance of eDNA and concludes that existence of eDNA on bacterial cell surfaces is a key facilitator in binding of Ca2+ to eDNA thereby mediating bacterial aggregation and biofilm formation. PMID:24651318

Fs-laser-induced Ca2+ concentration change during membrane perforation for cell transfection.

PubMed

Baumgart, J; Bintig, W; Ngezahayo, A; Lubatschowski, H; Heisterkamp, A

2010-02-01

Fs-laser based opto-perforation is a gentle method for gene transfer into sensitive cells such as stem cells or primary cells. The high selectivity and the low damage to the cell lead to a high efficiency of transfection. However, there are side effects which induce stress to the cell due to the exchange of intra- and extracellular media as well as the disintegration of the structure of biomolecules resulting from the laser exposure. Moreover, the mechanisms of the optical transfection are still unclear. In this paper, we present our study on calcium (Ca(2+)) homeostasis during cell surgery, especially during laser induced membrane perforation. We show that the manipulation of cells can induce an increase in the cytosolic Ca(2+) concentration. This increase was not observed if the manipulation of the cells was performed in absence of the extracellular calcium indicating the importance of the Ca(2+) uptake. We found, that the uptake of extracellular Ca(2+) strongly depends on the repetition rate and the irradiation time of the laser pulses. The exposure for several seconds to kHz pulses even induces Ca(2+) induced Ca(2+) release. Dependent on the location of perforation, probably in the vicinity of an intracellular Ca(2+) stock, an instantaneous intracellular Ca(2+) release can be induced. Since Ca(2+) could be involved in negative side effect by cell surgery, we propose an application of the optoperforation technique in nominal Ca(2+)-free external solution.

Thyrotropin Receptor Epitope and Human Leukocyte Antigen in Graves’ Disease

PubMed Central

Inaba, Hidefumi; De Groot, Leslie J.; Akamizu, Takashi

2016-01-01

Graves’ disease (GD) is an organ-specific autoimmune disease, and thyrotropin (TSH) receptor (TSHR) is a major autoantigen in this condition. Since the extracellular domain of human TSHR (TSHR-ECD) is shed into the circulation, TSHR-ECD is a preferentially immunogenic portion of TSHR. Both genetic factors and environmental factors contribute to development of GD. Inheritance of human leukocyte antigen (HLA) genes, especially HLA-DR3, is associated with GD. TSHR-ECD protein is endocytosed into antigen-presenting cells (APCs), and processed to TSHR-ECD peptides. These peptide epitopes bind to HLA-class II molecules, and subsequently the complex of HLA-class II and TSHR-ECD epitope is presented to CD4+ T cells. The activated CD4+ T cells secrete cytokines/chemokines that stimulate B-cells to produce TSAb, and in turn hyperthyroidism occurs. Numerous studies have been done to identify T- and B-cell epitopes in TSHR-ECD, including (1) in silico, (2) in vitro, (3) in vivo, and (4) clinical experiments. Murine models of GD and HLA-transgenic mice have played a pivotal role in elucidating the immunological mechanisms. To date, linear or conformational epitopes of TSHR-ECD, as well as the molecular structure of the epitope-binding groove in HLA-DR, were reported to be related to the pathogenesis in GD. Dysfunction of central tolerance in the thymus, or in peripheral tolerance, such as regulatory T cells, could allow development of GD. Novel treatments using TSHR antagonists or mutated TSHR peptides have been reported to be effective. We review and update the role of immunogenic TSHR epitopes and HLA in GD, and offer perspectives on TSHR epitope specific treatments. PMID:27602020

Agonist activation of cytosolic Ca2+ in subfornical organ cells projecting to the supraoptic nucleus

NASA Technical Reports Server (NTRS)

Johnson, R. F.; Beltz, T. G.; Sharma, R. V.; Xu, Z.; Bhatty, R. A.; Johnson, A. K.

2001-01-01

The subfornical organ (SFO) is sensitive to both ANG II and ACh, and local application of these agents produces dipsogenic responses and vasopressin release. The present study examined the effects of cholinergic drugs, ANG II, and increased extracellular osmolarity on dissociated, cultured cells of the SFO that were retrogradely labeled from the supraoptic nucleus. The effects were measured as changes in cytosolic calcium in fura 2-loaded cells by using a calcium imaging system. Both ACh and carbachol increased intracellular ionic calcium concentration ([Ca2+]i). However, in contrast to the effects of muscarinic receptor agonists on SFO neurons, manipulation of the extracellular osmolality produced no effects, and application of ANG II produced only moderate effects on [Ca2+]i in a few retrogradely labeled cells. The cholinergic effects on [Ca2+]i could be blocked with the muscarinic receptor antagonist atropine and with the more selective muscarinic receptor antagonists pirenzepine and 4-diphenylacetoxy-N-methylpiperdine methiodide (4-DAMP). In addition, the calcium in the extracellular fluid was required for the cholinergic-induced increase in [Ca2+]i. These findings indicate that ACh acts to induce a functional cellular response in SFO neurons through action on a muscarinic receptor, probably of the M1 subtype and that the increase of [Ca2+]i, at least initially, requires the entry of extracellular Ca2+. Also, consistent with a functional role of M1 receptors in the SFO are the results of immunohistochemical preparations demonstrating M1 muscarinic receptor-like protein present within this forebrain circumventricular organ.

Extracellular adenosine triphosphate increases cation permeability of chronic lymphocytic leukemic lymphocytes

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

Wiley, J.S.; Dubyak, G.R.

Extracellular adenosine triphosphate (ATP) is known to reversibly increase the cation permeability of a variety of freshly isolated and cultured cell types. In this study the effects of extracellular ATP were studied using peripheral blood lymphocytes (PBL) isolated from both normal subjects and from patients with chronic lymphocytic leukemia (CLL). Changes in the permeability to Na+, Rb+, and Li+ ions were measured using conventional isotope and flame photometry techniques. In addition, changes in cytosolic (Ca2+) were fluorimetrically monitored to assess possible changes in net Ca2+ influx. ATP produced a 12-fold increase in 22Na+ influx into CLL cells but only amore » 3.5-fold increase in this flux in PBL cells. A maximal response was produced by 0.1 mmol/L ATP in the absence of Mg2+, while a twofold molar excess of Mg2+ over ATP abolished the response. ATP had no effect on the passive (ouabain-insensitive) 86Rb+ influx into PBL cells but stimulated this flux by fivefold in the CLL cells. Li+ influx into CLL cells was also stimulated threefold by ATP. Under these same conditions ATP also produced a net increase in total cell Na and a decrease in total cell K in the CLL cells. Exclusion of two normally impermeable dyes, trypan blue and ethidium bromide, was not altered in the ATP-treated CLL cells. Finally, extracellular ATP (3 mmol/L) produced no significant change in the cytosolic (Ca2+) of normal, monocyte-depleted populations of PBL. Conversely, this same concentration of ATP produced a very rapid and a significant (an average threefold peak change) increase in the cytosolic (Ca2+) of cell preparations derived from five out of nine CLL patients. In these latter CLL cells, the ATP-induced elevation in cytosolic (Ca2+) appeared to be due to a net increase in Ca2+ influx, since no elevations were observed when the extracellular (Ca2+) was reduced to less than 0.1 mmol/L.« less

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.

Radioisotope tracer studies of inorganic carbon and Ca in microbially derived CaCO3

USGS Publications Warehouse

Yates, Kimberly K.; Robbins, Lisa L.

1999-01-01

Microbial calcification significantly impacts the cycling and deposition of inorganic carbon. This research employs 45Ca and 14C techniques as radioisotopic tracers to examine the role of cellular cycling of Ca2+ and inorganic carbon in CaCO3 precipitation by the unicellular green alga Nannochloris atomus. Implications of the effects of these physiological aspects on CaCO3 precipitation and the effects of microbial calcification on CaCO3 δ13C ratios are discussed. Results from pulse/chase experiments indicate that intracellular Ca2+ is incorporated into extracellular CaCO3. Intracellular inorganic carbon leaks from cells within 10 to 12 s after injection of unlabelled NaHCO3, providing a source of inorganic carbon for extracellular CaCO3. Cellular expulsion of calcium plays a key role in increasing the CaCO3 saturation state at the site of calcification. The δ13C ratios of microbial carbonates may vary depending on the amount of photorespiratory CO2 incorporated.

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

PubMed

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

2015-11-01

Activating mutations of calcium-sensing receptor (CaSR) cause autosomal dominant hypocalcemia (ADH). ADH patients develop hypocalcemia, hyperphosphatemia, and hypercalciuria, similar to the clinical features of hypoparathyroidism. The current treatment of ADH is similar to the other forms of hypoparathyroidism, using active vitamin D3 or parathyroid hormone (PTH). However, these treatments aggravate hypercalciuria and renal calcification. Thus, new therapeutic strategies for ADH are needed. Calcilytics are allosteric antagonists of CaSR, and may be effective for the treatment of ADH caused by activating mutations of CaSR. In order to examine the effect of calcilytic JTT-305/MK-5442 on CaSR harboring activating mutations in the extracellular and transmembrane domains in vitro, we first transfected a mutated CaSR gene into HEK cells. JTT-305/MK-5442 suppressed the hypersensitivity to extracellular Ca(2+) of HEK cells transfected with the CaSR gene with activating mutations in the extracellular and transmembrane domains. We then selected two activating mutations locating in the extracellular (C129S) and transmembrane (A843E) domains, and generated two strains of CaSR knock-in mice to build an ADH mouse model. Both mutant mice mimicked almost all the clinical features of human ADH. JTT-305/MK-5442 treatment in vivo increased urinary cAMP excretion, improved serum and urinary calcium and phosphate levels by stimulating endogenous PTH secretion, and prevented renal calcification. In contrast, PTH(1-34) treatment normalized serum calcium and phosphate but could not reduce hypercalciuria or renal calcification. CaSR knock-in mice exhibited low bone turnover due to the deficiency of PTH, and JTT-305/MK-5442 as well as PTH(1-34) increased bone turnover and bone mineral density (BMD) in these mice. These results demonstrate that calcilytics can reverse almost all the phenotypes of ADH including hypercalciuria and renal calcification, and suggest that calcilytics can become a novel therapeutic agent for ADH. © 2015 American Society for Bone and Mineral Research.

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.

Prognostic significance of highly sulfated chondroitin sulfates in ovarian cancer defined by the single chain antibody GD3A11.

PubMed

van der Steen, Sophieke C H A; van Tilborg, Angela A G; Vallen, Myrtille J E; Bulten, Johan; van Kuppevelt, Toin H; Massuger, Leon F A G

2016-03-01

The extracellular matrix (ECM) of ovarian cancer may provide a number of potential biomarkers. Chondroitin sulfate (CS), a class of sulfated polysaccharides, is abundantly present in the ECM of ovarian cancer. Structural alterations of CS chains (i.e. sulfation pattern) have been demonstrated to play a role in cancer development and progression. In this study we investigate the potential of highly sulfated CS as a biomarker in ovarian cancer using the single chain antibody GD3A11 selected by the phage display technology. The specificity of the antibody was determined by an indirect ELISA. GD3A11 epitope expression was assessed by immunohistochemistry in healthy organs, benign and malignant ovarian tumors (N=359) and correlated to clinical parameters. The CHST15 gene, responsible for the biosynthesis of highly sulfated CS was evaluated for mutation and methylation status. The GD3A11 epitope was minimally expressed in normal organs. Intense expression was observed in the ECM of different ovarian cancer subtypes, in contrast to benign ovarian tumors. Expression was independent of tumor grade, FIGO stage, and the use chemotherapy. For the aggressive ovarian cancer phenotype, intense expression was identified as an independent predictor for poor prognosis. CHST15 gene analysis showed no mutations nor an altered methylation status. Specific highly sulfated CS motifs expressed in the tumoral ECM hold biomarker potential in ovarian cancer patients. These matrix motifs constitute a novel class of biomarkers with prognostic significance and may be instrumental for innovative diagnostic and therapeutic applications (e.g. targeted therapy) in management of ovarian cancer. Copyright © 2016 Elsevier Inc. All rights reserved.

An Ocean Acidification Acclimatised Green Tide Alga Is Robust to Changes of Seawater Carbon Chemistry but Vulnerable to Light Stress

PubMed Central

Li, Xinshu; Feng, Zhihua; Xu, Juntian

2016-01-01

Ulva is the dominant genus in the green tide events and is considered to have efficient CO2 concentrating mechanisms (CCMs). However, little is understood regarding the impacts of ocean acidification on the CCMs of Ulva and the consequences of thalli’s acclimation to ocean acidification in terms of responding to environmental factors. Here, we grew a cosmopolitan green alga, Ulva linza at ambient (LC) and elevated (HC) CO2 levels and investigated the alteration of CCMs in U. linza grown at HC and its responses to the changed seawater carbon chemistry and light intensity. The inhibitors experiment for photosynthetic inorganic carbon utilization demonstrated that acidic compartments, extracellular carbonic anhydrase (CA) and intracellular CA worked together in the thalli grown at LC and the acquisition of exogenous carbon source in the thalli could be attributed to the collaboration of acidic compartments and extracellular CA. Contrastingly, when U. linza was grown at HC, extracellular CA was completely inhibited, acidic compartments and intracellular CA were also down-regulated to different extents and thus the acquisition of exogenous carbon source solely relied on acidic compartments. The down-regulated CCMs in U. linza did not affect its responses to changes of seawater carbon chemistry but led to a decrease of net photosynthetic rate when thalli were exposed to increased light intensity. This decrease could be attributed to photodamage caused by the combination of the saved energy due to the down-regulated CCMs and high light intensity. Our findings suggest future ocean acidification might impose depressing effects on green tide events when combined with increased light exposure. PMID:28033367

An Ocean Acidification Acclimatised Green Tide Alga Is Robust to Changes of Seawater Carbon Chemistry but Vulnerable to Light Stress.

PubMed

Gao, Guang; Liu, Yameng; Li, Xinshu; Feng, Zhihua; Xu, Juntian

2016-01-01

Ulva is the dominant genus in the green tide events and is considered to have efficient CO2 concentrating mechanisms (CCMs). However, little is understood regarding the impacts of ocean acidification on the CCMs of Ulva and the consequences of thalli's acclimation to ocean acidification in terms of responding to environmental factors. Here, we grew a cosmopolitan green alga, Ulva linza at ambient (LC) and elevated (HC) CO2 levels and investigated the alteration of CCMs in U. linza grown at HC and its responses to the changed seawater carbon chemistry and light intensity. The inhibitors experiment for photosynthetic inorganic carbon utilization demonstrated that acidic compartments, extracellular carbonic anhydrase (CA) and intracellular CA worked together in the thalli grown at LC and the acquisition of exogenous carbon source in the thalli could be attributed to the collaboration of acidic compartments and extracellular CA. Contrastingly, when U. linza was grown at HC, extracellular CA was completely inhibited, acidic compartments and intracellular CA were also down-regulated to different extents and thus the acquisition of exogenous carbon source solely relied on acidic compartments. The down-regulated CCMs in U. linza did not affect its responses to changes of seawater carbon chemistry but led to a decrease of net photosynthetic rate when thalli were exposed to increased light intensity. This decrease could be attributed to photodamage caused by the combination of the saved energy due to the down-regulated CCMs and high light intensity. Our findings suggest future ocean acidification might impose depressing effects on green tide events when combined with increased light exposure.

Can direct extracellular electron transfer occur in the absence of outer membrane cytochromes in Desulfovibrio vulgaris?

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

Elias, Dwayne A; Zane, Mr. Grant M.; Auer, Dr. Manfred

2010-01-01

Extracellular electron transfer has been investigated over several decades via forms of soluble electron transfer proteins that are exported for extracellular reoxidation. More recently, several organisms have been shown to reduce extracellular metals via the direct transfer of electron through appendages; also known as nanowires. They have been reported most predominantly in Shewanella and Geobacter. While the relevancy and composition of these structures in each genus has been debated, both possess outer membrane cytochrome complexes that could theoretically come into direct contact with solid phase oxidized metals. Members of the genus Desulfovibrio apparently have no such cytochromes although similar appendagesmore » are present, are electrically conductive, and are different from flagella. Upon U(VI)-reduction, the structures in Desulfovibrio become coated with U(IV). Deletion of flagellar genes did not alter soluble or amorphous Fe(III) or U(VI) reduction, or appendage appearance. Removal of the chromosomal pilA gene hampered amorphous Fe(III)-reduction by ca. 25%, but cells lacking the native plasmid, pDV1, reduced soluble Fe(III) and U(VI) at ca. 50% of the wild type rate while amorphous Fe(III)-reduction slowed to ca. 20% of the wild type rate. Appendages were present in all deletions as well as pDV1, except pilA. Gene complementation restored all activities and morphologies to wild type levels. This suggests that pilA encodes the structural component, whereas genes within pDV1 may provide the reactive members. How such appendages function without outer membrane cytochromes is under investigation.« less

Carbonic anhydrase activation enhances object recognition memory in mice through phosphorylation of the extracellular signal-regulated kinase in the cortex and the hippocampus.

PubMed

Canto de Souza, Lucas; Provensi, Gustavo; Vullo, Daniela; Carta, Fabrizio; Scozzafava, Andrea; Costa, Alessia; Schmidt, Scheila Daiane; Passani, Maria Beatrice; Supuran, Claudiu T; Blandina, Patrizio

2017-05-15

Rats injected with by d-phenylalanine, a carbonic anhydrase (CA) activator, enhanced spatial learning, whereas rats given acetazolamide, a CA inhibitor, exhibited impairments of fear memory consolidation. However, the related mechanisms are unclear. We investigated if CAs are involved in a non-spatial recognition memory task assessed using the object recognition test (ORT). Systemic administration of acetazolamide to male CD1 mice caused amnesia in the ORT and reduced CA activity in brain homogenates, while treatment with d-phenylalanine enhanced memory and increased CA activity. We provided also the first evidence that d-phenylalanine administration rapidly activated extracellular signal-regulated kinase (ERK) pathways, a critical step for memory formation, in the cortex and the hippocampus, two brain areas involved in memory processing. Effects elicited by d-phenylalanine were completely blunted by co-administration of acetazolamide, but not of 1-N-(4-sulfamoylphenyl-ethyl)-2,4,6-trimethylpyridinium perchlorate (C18), a CA inhibitor that, differently from acetazolamide, does not cross the blood brain barrier. Our results strongly suggest that brain but not peripheral CAs activation potentiates memory as a result of ERK pathway enhanced activation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of Gd2O3 doping on structure and boron volatility of borosilicate glass sealants in solid oxide fuel cells-A study on the La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathode

NASA Astrophysics Data System (ADS)

Zhang, Qi; Tan, Shengwei; Ren, Mengyuan; Yang, Hsiwen; Tang, Dian; Chen, Kongfa; Zhang, Teng; Jiang, San Ping

2018-04-01

Boron volatility is one of the most important properties of borosilicate-based glass sealants in solid oxide fuel cells (SOFCs), as boron contaminants react with lanthanum-containing cathodes, forming LaBO3 and degrading the activity of SOFCs. Here, we report that the reaction between the volatile boron and a La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathode during polarization can be significantly reduced by doping aluminoborosilicate glass with Gd2O3. Specifically, the Gd cations in glass with 2 mol.% Gd2O3 dissolve preferentially in the borate-rich environment to form more Gd-metaborate structures and promote the formation of calcium metaborate (CaB2O4); they also condense the B-O network after heat treatment, which suppresses poisoning by boron contaminants on the LSCF cathode. The results provide insights into design and development of a reliable sealing glass for SOFC applications.

Synthesis and evaluation of novel polysaccharide-Gd-DTPA compounds as contrast agent for MRI

NASA Astrophysics Data System (ADS)

Sun, Guoying; Feng, Jianghua; Jing, Fengying; Pei, Fengkui; Liu, Maili

2003-09-01

Macromolecular conjugates of two kinds of natural polysaccharides, that from Panax quinquefolium linn (PQPS) and Ganoderma applanatum pat (GAPS), with gadolinium-diethylenetriaminepenta-acetic acid (Gd-DTPA) have been synthesized and characterized by means of FTIR, elementary analysis and ICP-AES. Their stability was investigated by competition study with Ca 2+, EDTA (ethylenediaminetetraacetic acid) and DTPA. Polysaccharide-bound complexes exhibit T1 relaxivities of 1.5-1.7 times that of Gd-DTPA in D 2O at 25°C and 9.4 T. MR imaging of Sprague-Dawley (SD) rats showed remarkable enhancement in rat liver and kidney after i.v. injection of these two complexes: liver parenchyma 60.9±5.6%, 57.8±7.4% at 65-85 min; kidney 144.9±14.5%, 199.9±25.4% at 10-30 min for PQPS-Gd-DTPA, GAPS-Gd-DTPA at gadolinium dose of 0.083 and 0.082 mmol/kg, respectively. Our preliminary in vivo and in vitro study indicates that the two kinds of polysaccharide-bound complexes are potential tissue-specific contrast agents for MRI.

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

PubMed

Eldyasti, Ahmed; Nakhla, George; Zhu, Jesse

2014-12-01

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

[Anti-M3 muscarinic acetylcholine receptor antibodies and Sjögren's syndrome].

PubMed

Tsuboi, Hiroto; Iizuka, Mana; Asashima, Hiromitsu; Sumida, Takayuki

2013-01-01

Sjögren's syndrome (SS) is an autoimmune disease that affects exocrine glands including salivary and lacrimal glands. It is characterized by lymphocytic infiltration into exocrine glands, leading to dry mouth and eyes. A number of auto-antibodies are detected in patients with SS. However, no SS-specific pathologic auto-antibodies have yet been found in this condition. M3 muscarinic acetylcholine receptor (M3R) plays a crucial role in the secretion of saliva. It is reported that some patients with SS carried inhibitory auto-antibodies against M3R. To clarify the epitopes and function of anti-M3R antibodies in SS, we examined antibodies to the extracellular domains (N terminal region, the first, second, and third extracellular loop) of M3R by ELISA using synthesized peptide antigens encoding these domains in 42 SS and 42 healthy controls (HC). Titers and positivity of anti-M3R antibodies to every extracellular domain of M3R were significantly higher in SS than in HC. Our results indicated the presence of several B cell epitopes on M3R in SS. Moreover, we analyzed the functions of anti-M3R antibodies by Ca(2+)-influx assays using a human salivary gland (HSG) cell line. The functional analysis indicated that the influence of such anti-M3R antibodies on Ca(2+)-influx in HSG cells might differ based on the epitopes to which they bind. Interestingly, both IgG from anti-M3R antibodies to the second extracellular loop positive SS and anti-M3R monoclonal antibodies against the second extracellular loop of M3R, which we generated, suppressed Ca(2+)-influx in the HSG cells induced by cevimeline stimulation. These observations suggested that auto-antibodies against the second extracellular loop of M3R could be involved in salivary dysfunction in patients with SS. These results indicated the presence of several B cell epitopes on M3R in SS and the influence of anti-M3R antibodies on salivary secretion might differ based on these epitopes. Thus, anti-M3R antibodies could be not only potential pathologic auto-antibodies, but also new diagnostic makers and therapeutic targets for SS.

Non‐invasive evaluation of the myocardial substrate of cardiac amyloidosis by gadolinium cardiac magnetic resonance

PubMed Central

Perugini, E; Rapezzi, C; Piva, T; Leone, O; Bacchi‐Reggiani, L; Riva, L; Salvi, F; Lovato, L; Branzi, A; Fattori, R

2006-01-01

Objective To investigate the prevalence and distribution of gadolinium (Gd) enhancement at cardiac magnetic resonance (CMR) imaging in patients with cardiac amyloidosis (CA) and to look for associations with clinical, morphological, and functional features. Patients and design 21 patients with definitely diagnosed CA (nine with immunoglobulin light chain amyloidosis and 12 transthyretin related) underwent Gd‐CMR. Results Gd enhancement was detected in 16 of 21 (76%) patients. Sixty six of 357 (18%) segments were enhanced, more often at the mid ventricular level. Transmural extension of enhancement within each patient significantly correlated with left ventricular (LV) end systolic volume (r  =  0.58). The number of enhanced segments correlated with LV end diastolic volume (r  =  0.76), end systolic volume (r  =  0.6), and left atrial size (r  =  0.56). Segments with > 50% extensive transmural enhancement more often were severely hypokinetic or akinetic (p  =  0.001). Patients with > 2 enhanced segments had significantly lower 12 lead QRS voltage and Sokolow‐Lyon index. No relation was apparent with any other clinical, morphological, functional, or histological characteristics. Conclusion Gd enhancement is common but not universally present in CA, probably due to expansion of infiltrated interstitium. The segmental and transmural distribution of the enhancement is highly variable, and mid‐ventricular regions are more often involved. Enhancement appears to be associated with impaired segmental and global contractility and a larger atrium. PMID:15939726

Evidence that polycystins are involved in Hydra cnidocyte discharge.

PubMed

McLaughlin, Susan

2017-03-01

Like other cnidarians, the freshwater organism Hydra is characterized by the possession of cnidocytes (stinging cells). Most cnidocytes are located on hydra tentacles, where they are organized along with sensory cells and ganglion cells into battery complexes. The function of the battery complexes is to integrate multiple types of stimuli for the regulation of cnidocyte discharge. The molecular mechanisms controlling the discharge of cnidocytes are not yet fully understood, but it is known that discharge depends on extracellular Ca 2+ and that mechanically induced cnidocyte discharge can be enhanced by the presence of prey extracts and other chemicals. Experiments in this paper show that a PKD2 (polycystin 2) transient receptor potential (TRP) channel is expressed in hydra tentacles and bases. PKD2 (TRPP) channels belong to the TRP channel superfamily and are non-selective Ca 2+ channels involved in the transduction of both mechanical and chemical stimuli in other organisms. Non-specific PKD2 channel inhibitors Neo (neomycin) and Gd 3+ (gadolinium) inhibit both prey capture and cnidocyte discharge in hydra. The PKD2 activator Trip (triptolide) enhances cnidocyte discharge in both starved and satiated hydra and reduces the inhibition of cnidocyte discharge caused by Neo. PKD1 and 2 proteins are known to act together to transduce mechanical and chemical stimuli; in situ hybridization experiments show that a PKD1 gene is expressed in hydra tentacles and bases, suggesting that polycystins play a direct or indirect role in cnidocyte discharge.

Depletion of intracellular zinc from neurons by use of an extracellular chelator in vivo and in vitro.

PubMed

Frederickson, Christopher J; Suh, Sang W; Koh, Jae-Young; Cha, Yoo K; Thompson, Richard B; LaBuda, Christopher J; Balaji, Rengarajan V; Cuajungco, Math P

2002-12-01

The membrane-impermeable chelator CaEDTA was introduced extracellularly among neurons in vivo and in vitro for the purpose of chelating extracellular Zn(2+). Unexpectedly, this treatment caused histochemically reactive Zn(2+) in intracellular compartments to drop rapidly. The same general result was seen with intravesicular Zn(2+), which fell after CaEDTA infusion into the lateral ventricle of the brain, with perikaryal Zn(2+) in Purkinje neurons (in vivo) and with cortical neurons (in vitro). These findings suggest either that the volume of zinc ion efflux and reuptake is higher than previously suspected or that EDTA can enter cells and vesicles. Caution is therefore warranted in attempting to manipulate extracellular or intracellular Zn(2+) selectively.

Monodispersed calcium carbonate nanoparticles modulate local pH and inhibit tumor growth in vivo

NASA Astrophysics Data System (ADS)

Som, Avik; Raliya, Ramesh; Tian, Limei; Akers, Walter; Ippolito, Joseph E.; Singamaneni, Srikanth; Biswas, Pratim; Achilefu, Samuel

2016-06-01

The acidic extracellular environment of tumors potentiates their aggressiveness and metastasis, but few methods exist to selectively modulate the extracellular pH (pHe) environment of tumors. Transient flushing of biological systems with alkaline fluids or proton pump inhibitors is impractical and nonselective. Here we report a nanoparticles-based strategy to intentionally modulate the pHe in tumors. Biochemical simulations indicate that the dissolution of calcium carbonate nanoparticles (nano-CaCO3) in vivo increases pH asymptotically to 7.4. We developed two independent facile methods to synthesize monodisperse non-doped vaterite nano-CaCO3 with distinct size range between 20 and 300 nm. Using murine models of cancer, we demonstrate that the selective accumulation of nano-CaCO3 in tumors increases tumor pH over time. The associated induction of tumor growth stasis is putatively interpreted as a pHe increase. This study establishes an approach to prepare nano-CaCO3 over a wide particle size range, a formulation that stabilizes the nanomaterials in aqueous solutions, and a pH-sensitive nano-platform capable of modulating the acidic environment of cancer for potential therapeutic benefits.The acidic extracellular environment of tumors potentiates their aggressiveness and metastasis, but few methods exist to selectively modulate the extracellular pH (pHe) environment of tumors. Transient flushing of biological systems with alkaline fluids or proton pump inhibitors is impractical and nonselective. Here we report a nanoparticles-based strategy to intentionally modulate the pHe in tumors. Biochemical simulations indicate that the dissolution of calcium carbonate nanoparticles (nano-CaCO3) in vivo increases pH asymptotically to 7.4. We developed two independent facile methods to synthesize monodisperse non-doped vaterite nano-CaCO3 with distinct size range between 20 and 300 nm. Using murine models of cancer, we demonstrate that the selective accumulation of nano-CaCO3 in tumors increases tumor pH over time. The associated induction of tumor growth stasis is putatively interpreted as a pHe increase. This study establishes an approach to prepare nano-CaCO3 over a wide particle size range, a formulation that stabilizes the nanomaterials in aqueous solutions, and a pH-sensitive nano-platform capable of modulating the acidic environment of cancer for potential therapeutic benefits. Electronic supplementary information (ESI) available: Summary of experiments, theoretical schema of effect, synthesis schema, X-Ray diffraction results, TEM of effects of different solvents on particles in various solvents. See DOI: 10.1039/c5nr06162h

Signatures of cytoplasmic proteins in the exoproteome distinguish community- and hospital-associated methicillin-resistant Staphylococcus aureus USA300 lineages.

PubMed

Mekonnen, Solomon A; Palma Medina, Laura M; Glasner, Corinna; Tsompanidou, Eleni; de Jong, Anne; Grasso, Stefano; Schaffer, Marc; Mäder, Ulrike; Larsen, Anders R; Gumpert, Heidi; Westh, Henrik; Völker, Uwe; Otto, Andreas; Becher, Dörte; van Dijl, Jan Maarten

2017-08-18

Methicillin-resistant Staphylococcus aureus (MRSA) is the common name for a heterogeneous group of highly drug-resistant staphylococci. Two major MRSA classes are distinguished based on epidemiology, namely community-associated (CA) and hospital-associated (HA) MRSA. Notably, the distinction of CA- and HA-MRSA based on molecular traits remains difficult due to the high genomic plasticity of S. aureus. Here we sought to pinpoint global distinguishing features of CA- and HA-MRSA through a comparative genome and proteome analysis of the notorious MRSA lineage USA300. We show for the first time that CA- and HA-MRSA isolates can be distinguished by 2 distinct extracellular protein abundance clusters that are predictive not only for epidemiologic behavior, but also for their growth and survival within epithelial cells. This 'exoproteome profiling' also groups more distantly related HA-MRSA isolates into the HA exoproteome cluster. Comparative genome analysis suggests that these distinctive features of CA- and HA-MRSA isolates relate predominantly to the accessory genome. Intriguingly, the identified exoproteome clusters differ in the relative abundance of typical cytoplasmic proteins, suggesting that signatures of cytoplasmic proteins in the exoproteome represent a new distinguishing feature of CA- and HA-MRSA. Our comparative genome and proteome analysis focuses attention on potentially distinctive roles of 'liberated' cytoplasmic proteins in the epidemiology and intracellular survival of CA- and HA-MRSA isolates. Such extracellular cytoplasmic proteins were recently invoked in staphylococcal virulence, but their implication in the epidemiology of MRSA is unprecedented.

Zinc induces long-term upregulation of T-type calcium current in hippocampal neurons in vivo.

PubMed

Ekstein, Dana; Benninger, Felix; Daninos, Moshe; Pitsch, Julika; van Loo, Karen M J; Becker, Albert J; Yaari, Yoel

2012-11-15

Extracellular zinc can induce numerous acute and persistent physiological and toxic effects in neurons by acting at their plasma membrane or intracellularly following permeation or uptake into them. Zinc acutely and reversibly blocks T-type voltage-gated calcium current (I(CaT)), but the long-term effect of zinc on this current has not been studied. Because chemically induced status epilepticus (SE) results in the release of zinc into the extracellular space, as well as in a long-lasting increase in I(CaT) in CA1 pyramidal cells, we hypothesized that zinc may play a causative role in I(CaT) upregulation. We tested this hypothesis by monitoring for 18 days the effects of zinc and ibotenic acid (a neurotoxic agent serving as control for zinc), injected into the right lateral ventricle, on I(CaT) in rat CA1 pyramidal cells. Both zinc and ibotenic acid caused marked hippocampal lesions on the side of injection, but only minor damage to contralateral hippocampi. Zinc, but not ibotenic acid, caused upregulation of a nickel-sensitive I(CaT) in a subset of contralateral CA1 pyramidal cells, appearing 2 days after injection and lasting for about 2 weeks thereafter. In contrast, acute application of zinc to CA1 pyramidal cells promptly blocked I(CaT). These data indicate that extracellular zinc has a dual effect on I(CaT), blocking it acutely while causing its long-term upregulation. Through the latter effect, zinc may regulate the intrinsic excitability of principal neurons, particularly in pathological conditions associated with enhanced release of zinc, such as SE.

Effects of pilocarpine and cevimeline on Ca2+ mobilization in rat parotid acini and ducts.

PubMed

Ono, Kentaro; Inagaki, Tomohiro; Iida, Taichi; Hosokawa, Ryuji; Inenaga, Kiyotoshi

2009-01-01

Previous reports suggested that there is no significant difference in the binding affinity of pilocarpine and cevimeline on muscarinic receptors (1). However, in vivo studies from our laboratory suggested that pilocarpine-induced salivation from the parotid gland is greater than that induced by cevimeline in rats. Therefore, in the present study, sialogogue-induced intracellular Ca(2+) mobilization was investigated in isolated parotid gland cells in vitro. Pilocarpine and cevimeline increased the intracellular Ca(2+) concentration of parotid gland acinar and duct cells over 1 microM in a dose-dependent manner. Pilocarpine-induced responses were higher than cevimeline-induced responses. Ca(2+) responses to both agents were completely blocked by 1 microM 4-DAMP, an M3 muscarinic receptor antagonist. In the absence of extracellular Ca(2+), both sialogogues induced transient Ca(2+) increase in parotid gland acinar cells. These results suggest that the sialogogues stimulate some common routes via the Ca(2+) signaling in parotid gland acinar cells. We also report a significant difference of Ca(2+) responses in concentration between pilocarpine and cevimeline in parotid gland acinar cells. The different Ca(2+) responses between the sialogogues would explain the different saliva volumes from the parotid gland between them that we have observed in previous in vivo studies.

A DFT study of the mechanism and the regioselectivity of [3 + 2] cycloaddition reactions of nitrile oxides with α,β-acetylenic aldehyde

NASA Astrophysics Data System (ADS)

Sobhi, Chafia; Nacereddine, Abdelmalek Khorief; Nasri, Lilia; Lechtar, Zohra; Djerourou, Abdelhafid

2016-11-01

A DFT study of the (32CA) reaction of a series of some nitrile oxides with electron-deficient alkyne (3-phenylpropionlaldehyde) in gas phase and in toluene has been carried out using B3LYP functional with 6-31G(d) basis set. Two reactive channels 4- and 5-associated with the two regioisomeric modes have been located and characterised. These 32CA reactions are characterised by a low asynchronous one-step mechanism with a low-polar character. Analysis of the DFT reactivity indices indicates that the nucleophilic centre of the different nitrile oxides accounts for the 4-regioselectivity. Our calculations are in a good agreement with the experimental findings.

REVEALING THE ACTIVATION PATHWAY FOR TMEM16A CHLORIDE CHANNELS FROM MACROSCOPIC CURRENTS AND KINETIC MODELS

PubMed Central

Contreras-Vite, Juan A.; Cruz-Rangel, Silvia; De Jesús-Pérez, José J.; Aréchiga Figueroa, Iván A.; Rodríguez-Menchaca, Aldo A.; Pérez-Cornejo, Patricia; Hartzell, H. Criss; Arreola, Jorge

2017-01-01

TMEM16A (ANO1), the pore-forming subunit of calcium-activated chloride channels, regulates several physiological and pathophysiological processes such as smooth muscle contraction, cardiac and neuronal excitability, salivary secretion, tumour growth, and cancer progression. Gating of TMEM16A is complex because it involves the interplay between increases in intracellular calcium concentration ([Ca2+]i), membrane depolarization, extracellular Cl− or permeant anions, and intracellular protons. Our goal here was to understand how these variables regulate TMEM16A gating and to explain four observations. a) TMEM16A is activated by voltage in the absence of intracellular Ca2+. b) The Cl− conductance is decreased after reducing extracellular Cl− concentration ([Cl−]o). c) ICl is regulated by physiological concentrations of [Cl−]o. d) In cells dialyzed with 0.2 µM [Ca2+]i, Cl− has a bimodal effect: at [Cl−]o < 30 mM TMEM16A current activates with a monoexponential time course, but above 30 mM [Cl−]o ICl activation displays fast and slow kinetics. To explain the contribution of Vm, Ca2+ and Cl− to gating, we developed a 12-state Markov chain model. This model explains TMEM16A activation as a sequential, direct, and Vm-dependent binding of two Ca2+ ions coupled to a Vm-dependent binding of an external Cl− ion, with Vm-dependent transitions between states. Our model predicts that extracellular Cl− does not alter the apparent Ca2+ affinity of TMEM16A, which we corroborated experimentally. Rather, extracellular Cl− acts by stabilizing the open configuration induced by Ca2+ and by contributing to the Vm dependence of activation. PMID:27138167

EGF stimulates Mg{sup 2+} influx in mammary epithelial cells

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

Trapani, Valentina; Arduini, Daniela; Luongo, Francesca

2014-11-28

Highlights: • EGF stimulation potentiates Mg{sup 2+} influx into epithelial cells. • EGF-induced Mg{sup 2+} influx does not depend on the concomitantly induced Ca{sup 2+} signal. • EGF-induced Ca{sup 2+} signal is dependent on the presence of extracellular Mg{sup 2+}. • New players in EGF-mediated signaling might be exploited as therapeutic targets. - Abstract: Magnesium is well established as a fundamental factor that regulates cell proliferation. However, the molecular mechanisms linking mitogenic signals, extracellular magnesium availability and intracellular effectors are still largely unknown. In the present study we sought to determine whether EGF regulates magnesium homeostasis in normal HC11 mammarymore » epithelial cells. To this end, we measured Mg{sup 2+} and Ca{sup 2+} fluxes by confocal imaging in live cells loaded with specific fluorescent ion indicators (Mag-Fluo-4 and Fluo-4, respectively). EGF stimulation induces a rapid and sustained increase in intracellular Mg{sup 2+}, concomitantly with a rise in intracellular calcium. The increase in intracellular Mg{sup 2+} derives from an influx from the extracellular compartment, and does not depend on Ca{sup 2+}. On the contrary, the increase in intracellular Ca{sup 2+} derives from intracellular stores, and is impaired in the absence of extracellular magnesium. Inhibition of the EGF receptor tyrosine kinase by Tyrphostin AG1478 markedly inhibits EGF-induced Mg{sup 2+} and Ca{sup 2+} signals. These findings demonstrate that not only does Mg{sup 2+} influx represent an important step in the physiological response of epithelial cells to EGF, but unexpectedly the EGF-induced Mg{sup 2+} influx is essential for the Ca{sup 2+} signal to occur.« less

Ca2+ signalling, voltage-gated Ca2+ channels and praziquantel in flatworm neuromusculature.

PubMed

Greenberg, R M

2005-01-01

Transient changes in calcium (Ca2+) levels regulate a wide variety of cellular processes, and cells employ both intracellular and extracellular sources of Ca2+ for signalling. Praziquantel, the drug of choice against schistosomiasis, disrupts Ca2+ homeostasis in adult worms. This review will focus on voltage-gated Ca2+ channels, which regulate levels of intracellular Ca2+ by coupling membrane depolarization to entry of extracellular Ca2+. Ca2+ channels are members of the ion channel superfamily and represent essential components of neurons, muscles and other excitable cells. Ca2+ channels are membrane protein complexes in which the pore-forming alpha1 subunit is modulated by auxiliary subunits such as beta and alpha2delta. Schistosomes express two Ca2+ channel beta subunit subtypes: a conventional subtype similar to beta subunits found in other vertebrates and invertebrates and a novel variant subtype with unusual structural and functional properties. The variant schistosome beta subunit confers praziquantel sensitivity to an otherwise praziquantel-insensitive mammalian Ca2+ channel, implicating it as a mediator of praziquantel action.

An N-methyl-D-aspartate receptor-independent excitatory action of partial reduction of extracellular [Mg2+] in CA1-region of rat hippocampal slices.

PubMed

Hamon, B; Stanton, P K; Heinemann, U

1987-03-31

Partial reduction of [Mg2+]o from 2 to 1 mM markedly enhanced neuronal responses evoked by Schaffer collateral-commissural fiber stimulation in the CA1-region of rat hippocampal slices. The amplitude of extracellular population potentials recorded in the CA1-pyramidal cell layer and maximum dV/dt of extracellular population EPSP's recorded in the CA1-pyramidal apical dendritic layer were both increased. However, unlike findings from slices where Mg2+ was completely removed from the bathing medium, there was no spontaneous or evoked epileptiform activity, and the N-methyl-D-aspartate (NMDA) receptor antagonist 2-amino-5-phosphonovalerate (2-APV) did not antagonize the enhancement of evoked responses. These results indicate that, in addition to the participation of NMDA receptors in the epileptiform activity observed when Mg2+ is completely removed from the bathing medium, there is also an NMDA receptor-independent excitatory action of partial reduction of [Mg2+]o in hippocampal slices.

Two-photon activation of endogenous store-operated calcium channels without optogenetics

NASA Astrophysics Data System (ADS)

Cheng, Pan; Tang, Wanyi; He, Hao

2018-02-01

Store-operated calcium (SOC) channels, regulated by intracellular Ca2+ store, are the essential pathway of calcium signaling and participate in a wide variety of cellular activities such as gene expression, secretion and immune response1. However, our understanding and regulation of SOC channels are mainly based on pharmacological methods. Considering the unique advantages of optical control, optogenetic control of SOC channels has been developed2. However, the process of genetic engineering to express exogenous light-sensitive protein is complicated, which arouses concerns about ethic difficulties in some research of animal and applications in human. In this report, we demonstrate rapid, robust and reproducible two-photon activation of endogenous SOC channels by femtosecond laser without optogenetics. We present that the short-duration two-photon scanning on subcellular microregion induces slow Ca2+ influx from extracellular medium, which can be eliminated by removing extracellular Ca2+. Block of SOC channels using various pharmacological inhibitors or knockdown of SOC channels by RNA interference reduce the probability of two-photon activated Ca2+ influx. On the contrary, overexpression of SOC channels can increase the probability of Ca2+ influx by two-photon scanning. These results collectively indicate Ca2+ influx through two-photon activated SOC channels. Different from classical pathway of SOC entry activated by Ca2+ store depletion, STIM1, the sensor protein of Ca2+ level in endoplasmic reticulum, does not show any aggregation or migration in this two-photon activated Ca2+ influx, which rules out the possibility of intracellular Ca2+ store depletion. Thereby, we propose this all-optical method of two-photon activation of SOC channels is of great potential to be widely applied in the research of cell calcium signaling and related biological research.

Inhibition of Carbonic Anhydrase IX by Ureidosulfonamide Inhibitor U104 Reduces Prostate Cancer Cell Growth, But Does Not Modulate Daunorubicin or Cisplatin Cytotoxicity.

PubMed

Riemann, Anne; Güttler, Antje; Haupt, Verena; Wichmann, Henri; Reime, Sarah; Bache, Matthias; Vordermark, Dirk; Thews, Oliver

2018-03-05

Carbonic anhydrase (CA) IX has emerged as a promising target for cancer therapy. It is highly upregulated in hypoxic regions and mediates pH regulation critical for tumor cell survival as well as extracellular acidification of the tumor microenvironment, which promotes tumor aggressiveness via various mechanisms, such as augmenting metastatic potential. Therefore, the aim of this study was to analyze the complex interdependency between CA IX and the tumor microenvironment in prostate tumor cells with regard to potential therapeutic implications. CA IX was upregulated by hypoxia as well as acidosis in prostate cancer cells. This induction did not modulate intracellular pH but led to extracellular acidification. Pharmacological inhibition of CA IX activity by U104 (SLC-0111) resulted in a reduction in tumor cell growth and an increase in apoptotic cell death. Intracellular pH was reduced under normoxic and even more so under hypoxic conditions when CA IX level was high. However, although intracellular pH regulation was disturbed, targeting CA IX in combination with daunorubicin or cisplatin did not intensify apoptotic tumor cell death. Hence, targeting CA IX in prostate cancer cells can lead to intracellular pH dysregulation and, consequently, can reduce cellular growth and elevate apoptotic cell death. Attenuation of extracellular acidification by blocking CA IX might additionally impede tumor progression and metastasis. However, no beneficial effect was seen when targeting CA IX in combination with chemotherapeutic drugs.

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

Toxicological perspective on the osmoregulation and ionoregulation physiology of major ions by freshwater animals: Teleost fish, crustacea, aquatic insects, and Mollusca.

PubMed

Griffith, Michael B

2017-03-01

Anthropogenic sources increase freshwater salinity and produce differences in constituent ions compared with natural waters. Moreover, ions differ in physiological roles and concentrations in intracellular and extracellular fluids. Four freshwater taxa groups are compared, to investigate similarities and differences in ion transport processes and what ion transport mechanisms suggest about the toxicity of these or other ions in freshwater. Although differences exist, many ion transporters are functionally similar and may belong to evolutionarily conserved protein families. For example, the Na + /H + -exchanger in teleost fish differs from the H + /2Na + (or Ca 2+ )-exchanger in crustaceans. In osmoregulation, Na + and Cl - predominate. Stenohaline freshwater animals hyperregulate until they are no longer able to maintain hypertonic extracellular Na + and Cl - concentrations with increasing salinity and become isotonic. Toxic effects of K + are related to ionoregulation and volume regulation. The ionic balance between intracellular and extracellular fluids is maintained by Na + /K + -adenosine triphosphatase (ATPase), but details are lacking on apical K + transporters. Elevated H + affects the maintenance of internal Na + by Na + /H + exchange; elevated HCO 3 - inhibits Cl - uptake. The uptake of Mg 2+ occurs by the gills or intestine, but details are lacking on Mg 2+ transporters. In unionid gills, SO 4 2- is actively transported, but most epithelia are generally impermeant to SO 4 2- . Transporters of Ca 2+ maintain homeostasis of dissolved Ca 2+ . More integration of physiology with toxicology is needed to fully understand freshwater ion effects. Environ Toxicol Chem 2017;36:576-600. Published 2016 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America. Published 2016 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

L-type Ca2+ channels in the heart: structure and regulation.

PubMed

Treinys, Rimantas; Jurevicius, Jonas

2008-01-01

This review analyzes the structure and regulation mechanisms of voltage-dependent L-type Ca(2+) channel in the heart. L-type Ca(2+) channels in the heart are composed of four different polypeptide subunits, and the pore-forming subunit alpha(1) is the most important part of the channel. In cardiac myocytes, Ca(2+) enter cell cytoplasm from extracellular space mainly through L-type Ca(2+) channels; these channels are very important system in heart Ca(2+) uptake regulation. L-type Ca(2+) channels are responsible for the activation of sarcoplasmic reticulum channels (RyR2) and force of muscle contraction generation in heart; hence, activity of the heart depends on L-type Ca(2+) channels. Phosphorylation of channel-forming subunits by different kinases is one of the most important ways to change the activity of L-type Ca(2+) channel. Additionally, the activity of L-type Ca(2+) channels depends on Ca(2+) concentration in cytoplasm. Ca(2+) current in cardiac cells can facilitate, and this process is regulated by phosphorylation of L-type Ca(2+) channels and intracellular Ca(2+) concentration. Disturbances in cellular Ca(2+) transport and regulation of L-type Ca(2+) channels are directly related to heart diseases, life quality, and life span.

Excess influx of Zn(2+) into dentate granule cells affects object recognition memory via attenuated LTP.

PubMed

Suzuki, Miki; Fujise, Yuki; Tsuchiya, Yuka; Tamano, Haruna; Takeda, Atsushi

2015-08-01

The influx of extracellular Zn(2+) into dentate granule cells is nonessential for dentate gyrus long-term potentiation (LTP) and the physiological significance of extracellular Zn(2+) dynamics is unknown in the dentate gyrus. Excess increase in extracellular Zn(2+) in the hippocampal CA1, which is induced with excitation of zincergic neurons, induces memory deficit via excess influx of Zn(2+) into CA1 pyramidal cells. In the present study, it was examined whether extracellular Zn(2+) induces object recognition memory deficit via excess influx of Zn(2+) into dentate granule cells. KCl (100 mM, 2 µl) was locally injected into the dentate gyrus. The increase in intracellular Zn(2+) in dentate granule cells induced with high K(+) was blocked by co-injection of CaEDTA and CNQX, an extracellular Zn(2+) chelator and an AMPA receptor antagonist, respectively, suggesting that high K(+) increases the influx of Zn(2+) into dentate granule cells via AMPA receptor activation. Dentate gyrus LTP induction was attenuated 1 h after KCl injection into the dentate gyrus and also attenuated when KCl was injected 5 min after the induction. Memory deficit was induced when training of object recognition test was performed 1 h after KCl injection into the dentate gyrus and also induced when KCl was injected 5 min after the training. High K(+)-induced impairments of LTP and memory were rescued by co-injection of CaEDTA. These results indicate that excess influx of Zn(2+) into dentate granule cells via AMPA receptor activation affects object recognition memory via attenuated LTP induction. Even in the dentate gyrus where is scarcely innervated by zincergic neurons, it is likely that extracellular Zn(2+) homeostasis is strictly regulated for cognition. Copyright © 2015 Elsevier Ltd. All rights reserved.

CB1 Receptor Antagonist SR141716A Inhibits Ca2+-Induced Relaxation in CB1 Receptor–Deficient Mice

PubMed Central

Bukoski, Richard D.; Bátkai, Sándor; Járai, Zoltán; Wang, Yanlin; Offertaler, Laszlo; Jackson, William F.; Kunos, George

2006-01-01

Mesenteric branch arteries isolated from cannabinoid type 1 receptor knockout (CB1−/−) mice, their wild-type littermates (CB1+/+ mice), and C57BL/J wild-type mice were studied to test the hypothesis that murine arteries undergo high sensitivity Ca2+-induced relaxation that is CB1 receptor dependent. Confocal microscope analysis of mesenteric branch arteries from wild-type mice showed the presence of Ca2+ receptor–positive periadventitial nerves. Arterial segments of C57 control mice mounted on wire myographs contracted in response to 5 μmol/L norepinephrine and responded to the cumulative addition of extracellular Ca2+ with a concentration-dependent relaxation that reached a maximum of 72.0±6.3% of the prerelaxation tone and had an EC50 for Ca2+ of 2.90±0.54 mmol/L. The relaxation was antagonized by precontraction in buffer containing 100 mmol/L K+ and by pretreatment with 10 mmol/L tetraethylammonium. Arteries from CB1−/− and CB1+/+ mice also relaxed in response to extracellular Ca2+ with no differences being detected between the knockout and their littermate controls. SR141716A, a selective CB1 antagonist, caused concentration-dependent inhibition of Ca2+-induced relaxation in both the knockout and wild-type strains (60% inhibition at 1 μmol/L). O-1918, a cannabidiol analog, had a similar blocking effect in arteries of both wild-type and CB1−/− mice at 10 μmol/L. In contrast, 1 μmol/L SR144538, a cannabinoid type 2 receptor antagonist, or 50 μmol/L 18α-glycyrrhetinic acid, a gap junction blocker, were without effect. SR141716A (1 to 30 μmol/L) was also assessed for nonspecific actions on whole-cell K+ currents in isolated vascular smooth muscle cells. SR141716A inhibited macroscopic K+ currents at concentrations higher than those required to inhibit Ca2+-induced relaxation, and appeared to have little effect on currents through large conductance Ca2+-activated K+ channels. These data indicate that arteries of the mouse relax in response to cumulative addition of extracellular Ca2+ in a hyperpolarization-dependent manner and rule out a role for CB1 or CB2 receptors in this effect. The possible role of a nonclassical cannabinoid receptor is discussed. PMID:11847193

Calcium Signaling Is Involved in Cadmium-Induced Neuronal Apoptosis via Induction of Reactive Oxygen Species and Activation of MAPK/mTOR Network

PubMed Central

Luo, Yan; Chen, Zi; Liu, Lei; Zhou, Hongyu; Chen, Wenxing; Shen, Tao; Han, Xiuzhen; Chen, Long; Huang, Shile

2011-01-01

Cadmium (Cd), a toxic environmental contaminant, induces oxidative stress, leading to neurodegenerative disorders. Recently we have demonstrated that Cd induces neuronal apoptosis in part by activation of the mitogen-activated protein kineses (MAPK) and mammalian target of rapamycin (mTOR) pathways. However, the underlying mechanism remains elusive. Here we show that Cd elevated intracellular calcium ion ([Ca2+]i) level in PC12, SH-SY5Y cells and primary murine neurons. BAPTA/AM, an intracellular Ca2+ chelator, abolished Cd-induced [Ca2+]i elevation, and blocked Cd activation of MAKPs including extracellular signal-regulated kinase 1/2 (Erk1/2), c-Jun N-terminal kinase (JNK) and p38, and mTOR-mediated signaling pathways, as well as cell death. Pretreatment with the extracellular Ca2+ chelator EGTA also prevented Cd-induced [Ca2+]i elevation, MAPK/mTOR activation, as well as cell death, suggesting that Cd-induced extracellular Ca2+ influx plays a critical role in contributing to neuronal apoptosis. In addition, calmodulin (CaM) antagonist trifluoperazine (TFP) or silencing CaM attenuated the effects of Cd on MAPK/mTOR activation and cell death. Furthermore, Cd-induced [Ca2+]i elevation or CaM activation resulted in induction of reactive oxygen species (ROS). Pretreatment with BAPTA/AM, EGTA or TFP attenuated Cd-induced ROS and cleavage of caspase-3 in the neuronal cells. Our findings indicate that Cd elevates [Ca2+]i, which induces ROS and activates MAPK and mTOR pathways, leading to neuronal apoptosis. The results suggest that regulation of Cd-disrupted [Ca2+]i homeostasis may be a new strategy for prevention of Cd-induced neurodegenerative diseases. PMID:21544200

Extracellular Calcium Has Multiple Targets to Control Cell Proliferation.

PubMed

Capiod, Thierry

2016-01-01

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

Assessment of gadolinium calcium oxoborate (GdCOB) for laser applications

NASA Astrophysics Data System (ADS)

Bajor, A. L.; Kisielewski, J.; Kłos, A.; Kopczyński, K.; Łukasiewicz, T.; Mierczyk, J.; Młyńczak, J.

2011-12-01

Increasing demand for growing high quality laser crystals puts a question about their most important parameters that one should concentrate on to get a desired product which will exhibit best properties in practical use. And by no means, this is a simple question. Apart of the usual lasing properties associated with a special dopant in the host material itself, one needs to consider another two lasing phenomena, namely second (SHG) and higher harmonic generation, and self-frequency doubling (SFD). Not necessarily all of these three can meet altogether in the same host material to yield in its best appearance in every case. We have made a review of basic properties of gadolinium oxoborate GdCa4O(BO3)3 (GdCOB) crystal and came to the conclusion that, currently, as a host material this is probably the best in all of its lasing applications. Although GdCOB has low thermal conductivity, which requires a suitable cooling, on the other hand it has got small thermo-optic coefficients which govern good operation in SHG and SFD experiments. Two inch dia. Nd-doped crystals were grown by the Czochralski technique. Since a large discrepancy in the literature exists on exact values of nonlinear coefficients, one is never sure about this whether theoretically predicted phase-matching angles (PMA) are those that are really optimal. Besides, none has yet measured the values of nonlinear coefficients as a function of doping concentration. Therefore we have not decided to cut numerous differently oriented samples for generation of different wavelengths in SHG and SFD, but rather tried to generate different wavelengths from the same samples. We have also not paid special attention to get highest possible conversion efficiencies. However, we have concentrated our attention on potential use of the core region in laser technique. Unlike in YAG crystals, when the core is by all means a parasitic structure, we discovered that the core region in GdCOB, that majority of investigators are even not aware of its presence in the crystal, can be also useful in laser technique. According to our best knowledge, a SHG of red light in this work is the second reported case in the world-wide literature.

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.

Machine learning based analytics of micro-MRI trabecular bone microarchitecture and texture in type 1 Gaucher disease.

PubMed

Sharma, Gulshan B; Robertson, Douglas D; Laney, Dawn A; Gambello, Michael J; Terk, Michael

2016-06-14

Type 1 Gaucher disease (GD) is an autosomal recessive lysosomal storage disease, affecting bone metabolism, structure and strength. Current bone assessment methods are not ideal. Semi-quantitative MRI scoring is unreliable, not standardized, and only evaluates bone marrow. DXA BMD is also used but is a limited predictor of bone fragility/fracture risk. Our purpose was to measure trabecular bone microarchitecture, as a biomarker of bone disease severity, in type 1 GD individuals with different GD genotypes and to apply machine learning based analytics to discriminate between GD patients and healthy individuals. Micro-MR imaging of the distal radius was performed on 20 type 1 GD patients and 10 healthy controls (HC). Fifteen stereological and textural measures (STM) were calculated from the MR images. General linear models demonstrated significant differences between GD and HC, and GD genotypes. Stereological measures, main contributors to the first two principal components (PCs), explained ~50% of data variation and were significantly different between males and females. Subsequent PCs textural measures were significantly different between GD patients and HC individuals. Textural measures also significantly differed between GD genotypes, and distinguished between GD patients with normal and pathologic DXA scores. PCA and SVM predictive analyses discriminated between GD and HC with maximum accuracy of 73% and area under ROC curve of 0.79. Trabecular STM differences can be quantified between GD patients and HC, and GD sub-types using micro-MRI and machine learning based analytics. Work is underway to expand this approach to evaluate GD disease burden and treatment efficacy. Copyright © 2016 Elsevier Ltd. All rights reserved.

Dual-wavelength vortex beam with high stability in a diode-pumped Yb:CaGdAlO4 laser

NASA Astrophysics Data System (ADS)

Shen, Yijie; Meng, Yuan; Fu, Xing; Gong, Mali

2018-05-01

We present a stable dual-wavelength vortex beam carrying orbital angular momentum (OAM) with two spectral peaks separated by a few terahertz in a diode-pumped Yb:CaGdAlO4 (CALGO) laser. The dual-wavelength spectrum is controlled by the pump power and off-axis loss in a laser resonator, arising from the broad emission bandwidth of Yb:CALGO. The OAM beam is obtained by a pair of cylindrical lenses serving as a π/2 convertor for high-order Hermite–Gaussian modes. The stability is verified by the fact that a 1\\hbar OAM beam with two spectral peaks at 1046.1 nm and 1057.2 nm (3.01 THz interval) can steadily operate for more than 3 h. It has great potential for scaling the application of OAM beams in terahertz spectroscopy, high-resolution interferometry, and so on.

Grape seed extract triggers apoptosis in Caco-2 human colon cancer cells through reactive oxygen species and calcium increase: extracellular signal-regulated kinase involvement.

PubMed

Dinicola, Simona; Mariggiò, Maria Addolorata; Morabito, Caterina; Guarnieri, Simone; Cucina, Alessandra; Pasqualato, Alessia; D'Anselmi, Fabrizio; Proietti, Sara; Coluccia, Pierpaolo; Bizzarri, Mariano

2013-09-14

Grape seed extract (GSE) from Italia, Palieri and Red Globe cultivars inhibits cell growth and induces apoptosis in Caco-2 human colon cancer cells in a dose-dependent manner. In order to investigate the mechanism(s) supporting the apoptotic process, we analysed reactive oxygen species (ROS) production, intracellular Ca2+ handling and extracellular signal-regulated kinase (ERK) activation. Upon exposure to GSE, ROS and intracellular Ca2+ levels increased in Caco-2 cells, concomitantly with ERK inactivation. As ERK activity is thought to be essential for promoting survival pathways, inhibition of this kinase is likely to play a relevant role in GSE-mediated anticancer effects. Indeed, pretreatment with N-acetyl cysteine, a ROS scavenger, reversed GSE-induced apoptosis, and promoted ERK phosphorylation. This effect was strengthened by ethylene glycol tetraacetic acid-mediated inhibition of extracellular Ca2+ influx. ROS and Ca2+ influx inhibition, in turn, increased ERK phosphorylation, and hence almost entirely suppressed GSE-mediated apoptosis. These data suggested that GSE triggers a previously unrecognised ERK-based mechanism, involving both ROS production and intracellular Ca2+ increase, eventually leading to apoptosis in cancer cells.

Organization of the Escherichia coli K-12 gene cluster responsible for production of the extracellular polysaccharide colanic acid.

PubMed Central

Stevenson, G; Andrianopoulos, K; Hobbs, M; Reeves, P R

1996-01-01

Colanic acid (CA) is an extracellular polysaccharide produced by most Escherichia coli strains as well as by other species of the family Enterobacteriaceae. We have determined the sequence of a 23-kb segment of the E. coli K-12 chromosome which includes the cluster of genes necessary for production of CA. The CA cluster comprises 19 genes. Two other sequenced genes (orf1.3 and galF), which are situated between the CA cluster and the O-antigen cluster, were shown to be unnecessary for CA production. The CA cluster includes genes for synthesis of GDP-L-fucose, one of the precursors of CA, and the gene for one of the enzymes in this pathway (GDP-D-mannose 4,6-dehydratase) was identified by biochemical assay. Six of the inferred proteins show sequence similarity to glycosyl transferases, and two others have sequence similarity to acetyl transferases. Another gene (wzx) is predicted to encode a protein with multiple transmembrane segments and may function in export of the CA repeat unit from the cytoplasm into the periplasm in a process analogous to O-unit export. The first three genes of the cluster are predicted to encode an outer membrane lipoprotein, a phosphatase, and an inner membrane protein with an ATP-binding domain. Since homologs of these genes are found in other extracellular polysaccharide gene clusters, they may have a common function, such as export of polysaccharide from the cell. PMID:8759852

The extracellular calcium-sensing receptor is required for cholecystokinin secretion in response to l-phenylalanine in acutely isolated intestinal I cells

PubMed Central

Liou, Alice P.; Sei, Yoshitatsu; Zhao, Xilin; Feng, Jianying; Lu, Xinping; Thomas, Craig; Pechhold, Susanne; Raybould, Helen E.

2011-01-01

The extracellular calcium-sensing receptor (CaSR) has recently been recognized as an l-amino acid sensor and has been implicated in mediating cholecystokinin (CCK) secretion in response to aromatic amino acids. We investigated whether direct detection of l-phenylalanine (l-Phe) by CaSR results in CCK secretion in the native I cell. Fluorescence-activated cell sorting of duodenal I cells from CCK-enhanced green fluorescent protein (eGFP) transgenic mice demonstrated CaSR gene expression. Immunostaining of fixed and fresh duodenal tissue sections confirmed CaSR protein expression. Intracellular calcium fluxes were CaSR dependent, stereoselective for l-Phe over d-Phe, and responsive to type II calcimimetic cinacalcet in CCK-eGFP cells. Additionally, CCK secretion by an isolated I cell population was increased by 30 and 62% in response to l-Phe in the presence of physiological (1.26 mM) and superphysiological (2.5 mM) extracellular calcium concentrations, respectively. While the deletion of CaSR from CCK-eGFP cells did not affect basal CCK secretion, the effect of l-Phe or cinacalcet on intracellular calcium flux was lost. In fact, both secretagogues, as well as superphysiological Ca2+, evoked an unexpected 20–30% decrease in CCK secretion compared with basal secretion in CaSR−/− CCK-eGFP cells. CCK secretion in response to KCl or tryptone was unaffected by the absence of CaSR. The present data suggest that CaSR is required for hormone secretion in the specific response to l-Phe by the native I cell, and that a receptor-mediated mechanism may inhibit hormone secretion in the absence of a fully functional CaSR. PMID:21252045

Effects of extracellular modulation through hypoxia on the glucose metabolism of human breast cancer stem cells

NASA Astrophysics Data System (ADS)

Yustisia, I.; Jusman, S. W. A.; Wanandi, S. I.

2017-08-01

Cancer stem cells have been reported to maintain stemness under certain extracellular changes. This study aimed to analyze the effect of extracellular O2 level modulation on the glucose metabolism of human CD24-/CD44+ breast cancer stem cells (BCSCs). The primary BCSCs (CD24-/CD44+ cells) were cultured under hypoxia (1% O2) for 0.5, 4, 6, 24 and 48 hours. After each incubation period, HIF1α, GLUT1 and CA9 expressions, as well as glucose metabolism status, including glucose consumption, lactate production, O2 consumption and extracellular pH (pHe) were analyzed using qRT-PCR, colorimetry, fluorometry, and enzymatic reactions, respectively. Hypoxia caused an increase in HIF1α mRNA expressions and protein levels and shifted the metabolic states to anaerobic glycolysis, as demonstrated by increased glucose consumption and lactate production, as well as decreased O2 consumption and pHe. Furthermore, we demonstrated that GLUT1 and CA9 mRNA expressions simultaneously increased, in line with HIF1α expression. In conclusion, modulation of the extracellular environment of human BCSCs through hypoxia shifedt the metabolic state of BCSCs to anaerobic glycolysis, which might be associated with GLUT1 and CA9 expressions regulated by HIFlα transcription factor.

Aβ mediates Sigma receptor degradation via CaN/NFAT pathway

PubMed Central

Fang, Min; Zhang, Pei; Zhao, Yanxin; Jin, Aiping; Liu, Xueyuan

2016-01-01

Sigma receptor is an endoplasmic reticulum protein and belongs to non-opioid receptor. Increasing evidence shows that Sigma receptor activation can significantly attenuate AD induced neurological dysfunction and the functional deficiency of Sigma receptor plays an important role in the Aβ induced neuronal loss. This study aimed to investigate the influence of extracellular accumulation of Aβ on the Sigma receptor expression. Our results showed the increase in extracellular Aβ had little influence on the mRNA expression of Sigma receptor, but gradually reduced its protein expression. Co-immunoprecipitation was employed to evaluate the interaction of Sigma receptor with other proteins. Results showed BIP could bind to Sigma receptor to affect the ubiquitination of Sigma receptor. Further investigation showed there was a NFAT binding site at the promoter of BIP. Then, Western blot assay was performed to detect NFAT expression. Results showed extracellular Aβ affected the nuclear translocation of NFAT and the CaN activity of NFAT also increased with the accumulation of extracellular Aβ. In this study, NFAT-BIP luciferase reporter gene system was constructed. Results showed NFAT was able to regulate the transcription of BIP. Thus, we speculate that extracellular Aβ accumulation may activate CaN/NFAT signaling pathway to induce chaperone BIP expression, which results in Sigma receptor ubiquitination and its degradation. PMID:27648137

Zinc is released by cultured astrocytes as a gliotransmitter under hypoosmotic stress-loaded conditions and regulates microglial activity.

PubMed

Segawa, Shohei; Nishiura, Takeshi; Furuta, Takahiro; Ohsato, Yuki; Tani, Misaki; Nishida, Kentaro; Nagasawa, Kazuki

2014-01-17

Astrocytes contribute to the maintenance of brain homeostasis via the release of gliotransmitters such as ATP and glutamate. Here we examined whether zinc was released from astrocytes under stress-loaded conditions, and was involved in the regulation of microglial activity as a gliotransmitter. Hypoosmotic stress was loaded to astrocytes using balanced salt solution prepared to 214-314 mOsmol/L, and then intra- and extra-cellular zinc levels were assessed using Newport Green DCF diacetate (NG) and ICP-MS, respectively. Microglial activation by the astrocytic supernatant was assessed by their morphological changes and poly(ADP-ribose) (PAR) polymer accumulation. Exposure of astrocytes to hypoosmotic buffer, increased the extracellular ATP level in osmolarity-dependent manners, indicating a load of hypoosmotic stress. In hypoosmotic stress-loaded astrocytes, there were apparent increases in the intra- and extra-cellular zinc levels. Incubation of microglia in the astrocytic conditioned medium transformed them into the activated "amoeboid" form and induced PAR formation. Administration of an extracellular zinc chelator, CaEDTA, to the astrocytic conditioned medium almost completely prevented the microglial activation. Treatment of astrocytes with an intracellular zinc chelator, TPEN, suppressed the hypoosmotic stress-increased intracellular, but not the extracellular, zinc level, and the increase in the intracellular zinc level was blocked partially by a nitric oxide synthase inhibitor, but not by CaEDTA, indicating that the mechanisms underlying the increases in the intra- and extra-cellular zinc levels might be different. These findings suggest that under hypoosmotic stress-loaded conditions, zinc is released from astrocytes and then plays a primary role in microglial activation as a gliotransmitter. Copyright © 2013 Elsevier Inc. All rights reserved.

Self-Assembled Nanomicelles as MRI Blood-Pool Contrast Agent.

PubMed

Babič, Andrej; Vorobiev, Vassily; Xayaphoummine, Céline; Lapicorey, Gaëlle; Chauvin, Anne-Sophie; Helm, Lothar; Allémann, Eric

2018-01-26

Gadolinium-loaded nanomicelles show promise as future magnetic resonance imaging (MRI) contrast agents (CAs). Their increased size and high gadolinium (Gd) loading gives them an edge in proton relaxivity over smaller molecular Gd-complexes. Their size and stealth properties are fundamental for their long blood residence time, opening the possibility for use as blood-pool contrast agents. Using l-tyrosine as a three-functional scaffold we synthesized a nanostructure building block 8. The double C18 aliphatic chain on one side, Gd-1,4,7,10-tetraazacyclododecane-1-4-7-triacetic acid (Gd-DO3A) with access to bulk water in the center and 2 kDa PEG on the hydrophilic side gave the amphiphilic properties required for the core-shell nanomicellar architecture. The self-assembly into Gd-loaded monodispersed 10-20 nm nanomicelles occurred spontaneously in water. These nanomicelles (Tyr-MRI) display very high relaxivity at 29 mm -1  s -1 at low field strength and low cytotoxicity. Good contrast enhancement of the blood vessels and the heart together with prolonged circulation time in vivo, makes Tyr-MRI an excellent candidate for a new supramolecular blood-pool MRI CA. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tissue gadolinium deposition in renally impaired rats exposed to different gadolinium-based MRI contrast agents: evaluation with inductively coupled plasma mass spectrometry (ICP-MS).

PubMed

Sato, Tomohiro; Ito, Katsuyoshi; Tamada, Tsutomu; Kanki, Akihiko; Watanabe, Shigeru; Nishimura, Hirotake; Tanimoto, Daigo; Higashi, Hiroki; Yamamoto, Akira

2013-10-01

To quantify tissue gadolinium (Gd) deposition in renally impaired rats exposed to Gd-EOB-DTPA and other Gd-based MRI contrast agents by means of inductively coupled plasma mass spectrometry (ICP-MS), and to compare the differences in distribution among major organs as possible triggers for nephrogenic systemic fibrosis (NSF). A total of 15 renally impaired rats were injected with Gd-EOB-DTPA, Gd-DTPA-BMA and Gd-HP-DO3A. Gd contents of skin, liver, kidney, lung, heart, spleen, diaphragm and femoral muscle were measured by inductively coupled plasma mass spectrometry (ICP-MS). Histological assessment was also conducted. Tissue Gd deposition in all organs was significantly higher (P=0.005~0.009) in the Gd-DTPA-BMA group than in the Gd-HP-DO3A and Gd-EOB-DTPA groups. In the Gd-DTPA-BMA group, Gd was predominantly deposited in kidney (1306±605.7μg/g), followed by skin, liver, lung, spleen, femoral muscle, diaphragm and heart. Comparing Gd-HP-DO3A and Gd-EOB-DTPA groups, Gd depositions in the kidney, liver and lung were significantly lower (P=0.009~0.011) in the Gd-EOB-DTPA group than in the Gd-HP-DO3A group although no significant differences were seen for any other organs. Gd-EOB-DTPA is a stable and safe Gd-based contrast agent (GBCA) showing lower Gd deposition in major organs in renally impaired rats, compared with other GBCAs. This fact suggests that the risk of NSF onset would be low in the use of Gd-EOB-DTPA. Copyright © 2013 Elsevier Inc. All rights reserved.

The essential oil of bergamot enhances the levels of amino acid neurotransmitters in the hippocampus of rat: implication of monoterpene hydrocarbons.

PubMed

Morrone, Luigi A; Rombolà, Laura; Pelle, Cinzia; Corasaniti, Maria T; Zappettini, Simona; Paudice, Paolo; Bonanno, Giambattista; Bagetta, Giacinto

2007-04-01

The effects of bergamot essential oil (BEO) on the release of amino acid neurotransmitters in rat hippocampus have been studied by in vivo microdialysis and by in vitro superfusion of isolated nerve terminals. Intraperitoneal administration of BEO (100microl/kg) significantly elevated the extracellular concentration of aspartate, glycine and taurine in a Ca(2+)-dependent manner. A dose-relation study generated a bell-shaped curve. When perfused into the hippocampus via the dialysis probe (20microl/20min), BEO produced a significant increase of extracellular aspartate, glycine, taurine as well as of GABA and glutamate. The augmentation of all amino acids was Ca(2+)-independent. Focally injected 1:1 diluted BEO preferentially caused extracellular increase of glutamate. Interestingly, this release appeared to be strictly Ca(2+)-dependent. BEO concentration-dependently enhanced the release of [(3)H]D-aspartate from superfused hippocampal synaptosomes. Similar results were obtained by monitoring the BEO-evoked release of endogenous glutamate. At relatively high concentrations, the BEO-induced [(3)H]d-aspartate release was almost entirely prevented by the glutamate transporter blocker dl-threo-beta-benzyloxyaspartic acid (DL-TBOA) and was Ca(2+)-independent. At relatively low concentrations the release of [(3)H]D-aspartate was only in part ( approximately 50%) DL-TBOA-sensitive and Ca(2+)-independent; the remaining portion of release was dependent on extracellular Ca(2+). Interestingly, the monoterpene hydrocarbon-free fraction of the essential oil appeared to be inactive while the bergapten-free fraction superimposed the releasing effect of BEO supporting the deduction that psoralens may not be implicated. To conclude, BEO contains into its volatile fraction still unidentified monoterpene hydrocarbons able to stimulate glutamate release by transporter reversal and/or by exocytosis, depending on the dose administered.

Stimulatory effects of the degradation products from Mg-Ca-Sr alloy on the osteogenesis through regulating ERK signaling pathway

NASA Astrophysics Data System (ADS)

Li, Mei; He, Peng; Wu, Yuanhao; Zhang, Yu; Xia, Hong; Zheng, Yufeng; Han, Yong

2016-09-01

The influence of Mg-1Ca-xwt.% Sr (x = 0.2, 0.5, 1.0, 2.0) alloys on the osteogenic differentiation and mineralization of pre-osteoblast MC3T3-E1 were studied through typical differentiation markers, such as intracellular alkaline phosphatase (ALP) activity, extracellular collagen secretion and calcium nodule formation. It was shown that Mg-1Ca alloys with different content of Sr promoted cell viability and enhanced the differentiation and mineralization levels of osteoblasts, and Mg-1Ca-2.0Sr alloy had the most remarkable and significant effect among all. To further investigate the underlying mechanisms, RT-PCR and Western Blotting assays were taken to analyze the mRNA expression level of osteogenesis-related genes and intracellular signaling pathways involved in osteogenesis, respectively. RT-PCR results showed that Mg-1Ca-2.0Sr alloy significantly up-regulated the expressions of the transcription factors of Runt-related transcription factor 2 (RUNX2) and Osterix (OSX), Integrin subunits, as well as alkaline phosphatase (ALP), Bone sialoprotein (BSP), Collagen I (COL I), Osteocalcin (OCN) and Osteopontin (OPN). Western Blotting results suggested that Mg-1Ca-2.0Sr alloy rapidly induced extracellular signal-regulated kinase (ERK) activation but showed no obvious effects on c-Jun N terminal kinase (JNK) and p38 kinase of MAPK. Taken together, our results demonstrated that Mg-1Ca-2.0Sr alloy had excellent biocompatibility and osteogenesis via the ERK pathway and is expected to be promising as orthopedic implants and bone repair materials.

GD1a Overcomes Inhibition of Myelination by Fibronectin via Activation of Protein Kinase A: Implications for Multiple Sclerosis.

PubMed

Qin, Jing; Sikkema, Arend H; van der Bij, Kristine; de Jonge, Jenny C; Klappe, Karin; Nies, Vera; Jonker, Johan W; Kok, Jan Willem; Hoekstra, Dick; Baron, Wia

2017-10-11

Remyelination failure by oligodendrocytes contributes to the functional impairment that characterizes the demyelinating disease multiple sclerosis (MS). Since incomplete remyelination will irreversibly damage axonal connections, treatments effectively promoting remyelination are pivotal in halting disease progression. Our previous findings suggest that fibronectin aggregates, as an environmental factor, contribute to remyelination failure by perturbing oligodendrocyte progenitor cell (OPC) maturation. Here, we aim at elucidating whether exogenously added gangliosides (i.e., cell surface lipids with a potential to modulate signaling pathways) could counteract fibronectin-mediated inhibition of OPC maturation. Exclusive exposure of rat oligodendrocytes to GD1a, but not other gangliosides, overcomes aggregated fibronectin-induced inhibition of myelin membrane formation, in vitro , and OPC differentiation in fibronectin aggregate containing cuprizone-induced demyelinated lesions in male mice. GD1a exerts its effect on OPCs by inducing their proliferation and, at a late stage, by modulating OPC maturation. Kinase activity profiling revealed that GD1a activated a protein kinase A (PKA)-dependent signaling pathway and increased phosphorylation of the transcription factor cAMP response element-binding protein. Consistently, the effect of GD1a in restoring myelin membrane formation in the presence of fibronectin aggregates was abolished by the PKA inhibitor H89, whereas the effect of GD1a was mimicked by the PKA activator dibutyryl-cAMP. Together, GD1a overcomes the inhibiting effect of aggregated fibronectin on OPC maturation by activating a PKA-dependent signaling pathway. Given the persistent presence of fibronectin aggregates in MS lesions, ganglioside GD1a might act as a potential novel therapeutic tool to selectively modulate the detrimental signaling environment that precludes remyelination. SIGNIFICANCE STATEMENT As an environmental factor, aggregates of the extracellular matrix protein fibronectin perturb the maturation of oligodendrocyte progenitor cells (OPCs), thereby impeding remyelination, in the demyelinating disease multiple sclerosis (MS). Here we demonstrate that exogenous addition of ganglioside GD1a overcomes the inhibiting effect of aggregated fibronectin on OPC maturation, both in vitro and in vivo , by activating a PKA-dependent signaling pathway. We propose that targeted delivery of GD1a to MS lesions may act as a potential novel molecular tool to boost maturation of resident OPCs to overcome remyelination failure and halt disease progression. Copyright © 2017 the authors 0270-6474/17/379925-14$15.00/0.

Materials Data on Ca(GdS2)2 (SG:122) by Materials Project

DOE Data Explorer

Kristin Persson

2014-07-09

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

Expression of extracellular calcium (Ca2 + o)-sensing receptor in the clonal osteoblast-like cell lines, UMR-106 and SAOS-2

NASA Technical Reports Server (NTRS)

Yamaguchi, T.; Kifor, O.; Chattopadhyay, N.; 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. More recent data have suggested the presence of this receptor in additional tissues, such as brain, intestine and skin. In this study, we examined the expression of the CaR in the rat and human osteosarcoma cell lines, UMR-106 and SAOS-2, respectively, which possess osteoblast-like characteristics. Both immunocytochemistry and Western blot analysis, using a polyclonal antiserum specific for the CaR, detected CaR protein in UMR-106 and SAOS-2 cells. The use of reverse transcription-polymerase chain reaction (RT-PCR) with CaR-specific primers, followed by nucleotide sequencing of the amplified products, also identified CaR transcripts in each cell line. Therefore, taken together, our data strongly suggest that the osteoblast-like cell lines, UMR-106 and SAOS-2, possess both CaR protein and mRNA very similar if not identical to those in parathyroid and kidney.

MPO4:Nd3+ (M=Ca, Gd), Luminomagnetic Nanophosphors with Optical and Magnetic Features for Multimodal Imaging Applications

NASA Astrophysics Data System (ADS)

Rightsell, Chris; Mimun, Lawrence C.; Kumar, Ajith G.; Sardar, Dhiraj K.

2015-03-01

Nanomaterials with multiple functionalities play a very important role in several high technology applications. A major area of such applications is the biomedical industry, where contrast agents with multiple imaging modalities can provide better results than conventional materials. Many of the contrast agents available now have drawbacks such as toxicity, photobleaching, low contrast, size restrictions, and overall cost of the imaging system. Rare-earth doped inorganic nanophosphors are alternatives to circumvent several of these issues, together with the added advantage of super high resolution imaging due to the excellent near infrared sensitivity of the phosphors. In addition to optical imaging features, by adding a magnetic ion such as Gd3+ at suitable lattice positions, the phosphor can be made magnetic, yielding dual imaging functionalities. In this research, we are presenting the optical and magnetic imaging features of sub-nanometer size MPO4:Nd3+ (M=Ca, Gd) phosphors for the potential application of these nanophosphors as multimodal contrast agents. Cytotoxicity, in vitro and in vivo imaging, penetration depth etc. are studied for various phosphor compositions, and optimized compositions are explored. This research was funded by the National Science Foundation Partnerships for Research and Education in Materials (NSF-PREM) Grant N0-DMR-0934218.

Cell Surface Translocation of Annexin A2 Facilitates Glutamate-induced Extracellular Proteolysis*

PubMed Central

Valapala, Mallika; Maji, Sayantan; Borejdo, Julian; Vishwanatha, Jamboor K.

2014-01-01

Glutamate-induced elevation in intracellular Ca2+ has been implicated in excitotoxic cell death. Neurons respond to increased glutamate levels by activating an extracellular proteolytic cascade involving the components of the plasmin-plasminogen system. AnxA2 is a Ca2+-dependent phospholipid binding protein and serves as an extracellular proteolytic center by recruiting the tissue plasminogen activator and plasminogen and mediating the localized generation of plasmin. Ratiometric Ca2+ imaging and time-lapse confocal microscopy demonstrated glutamate-induced Ca2+ influx. We showed that glutamate translocated both endogenous and AnxA2-GFP to the cell surface in a process dependent on the activity of the NMDA receptor. Glutamate-induced translocation of AnxA2 is dependent on the phosphorylation of tyrosine 23 at the N terminus, and mutation of tyrosine 23 to a non-phosphomimetic variant inhibits the translocation process. The cell surface-translocated AnxA2 forms an active plasmin-generating complex, and this activity can be neutralized by a hexapeptide directed against the N terminus. These results suggest an involvement of AnxA2 in potentiating glutamate-induced cell death processes. PMID:24742684

Extracellular Bio-imaging of Acetylcholine-stimulated PC12 Cells Using a Calcium and Potassium Multi-ion Image Sensor.

PubMed

Matsuba, Sota; Kato, Ryo; Okumura, Koichi; Sawada, Kazuaki; Hattori, Toshiaki

2018-01-01

In biochemistry, Ca 2+ and K + play essential roles to control signal transduction. Much interest has been focused on ion-imaging, which facilitates understanding of their ion flux dynamics. In this paper, we report a calcium and potassium multi-ion image sensor and its application to living cells (PC12). The multi-ion sensor had two selective plasticized poly(vinyl chloride) membranes containing ionophores. Each region on the sensor responded to only the corresponding ion. The multi-ion sensor has many advantages including not only label-free and real-time measurement but also simultaneous detection of Ca 2+ and K + . Cultured PC12 cells treated with nerve growth factor were prepared, and a practical observation for the cells was conducted with the sensor. After the PC12 cells were stimulated by acetylcholine, only the extracellular Ca 2+ concentration increased while there was no increase in the extracellular K + concentration. Through the practical observation, we demonstrated that the sensor was helpful for analyzing the cell events with changing Ca 2+ and/or K + concentration.

In vivo tumor characterization using both MR and optical contrast agents with a hybrid MRI-DOT system

NASA Astrophysics Data System (ADS)

Lin, Yuting; Ghijsen, Michael; Thayer, David; Nalcioglu, Orhan; Gulsen, Gultekin

2011-03-01

Dynamic contrast enhanced MRI (DCE-MRI) has been proven to be the most sensitive modality in detecting breast lesions. Currently available MR contrast agent, Gd-DTPA, is a low molecular weight extracellular agent and can diffuse freely from the vascular space into interstitial space. Due to this reason, DCE-MRI has low sensitivity in differentiating benign and malignant tumors. Meanwhile, diffuse optical tomography (DOT) can be used to provide enhancement kinetics of an FDA approved optical contrast agent, ICG, which behaves like a large molecular weight optical agent due to its binding to albumin. The enhancement kinetics of ICG may have a potential to distinguish between the malignant and benign tumors and hence improve the specificity. Our group has developed a high speed hybrid MRI-DOT system. The DOT is a fully automated, MR-compatible, multi-frequency and multi-spectral imaging system. Fischer-344 rats bearing subcutaneous R3230 tumor are injected simultaneously with Gd-DTPA (0.1nmol/kg) and IC-Green (2.5mg/kg). The enhancement kinetics of both contrast agents are recorded simultaneously with this hybrid MRI-DOT system and evaluated for different tumors.

Extracellular calcium- and magnesium-mediated regulation of passive calcium transport across Caco-2 monolayers.

PubMed

Davies, Sarah L; Gibbons, Claire E; Steward, Martin C; Ward, Donald T

2008-10-01

The calcium-sensing receptor (CaR) is expressed on intestinal epithelial serosal membrane and in Caco-2 cells. In renal epithelium, CaR expressed on the basolateral membrane acts to limit excess tubular Ca2+ reabsorption. Therefore, here we investigated whether extracellular calcium (Ca(o)2+) can regulate active or passive 45Ca2+ transport across differentiated Caco-2 monolayers via CaR-dependent or CaR-independent mechanisms. Raising the Ca(o)2+ concentration from 0.8 to 1.6 mM increased transepithelial electrical resistance (TER) and decreased passive Ca2+ permeability but failed to alter active Ca2+ transport. The Ca(o)2+ effect on TER was rapid, sustained and concentration-dependent. Increasing basolateral Mg2+ concentration increased TER and inhibited both passive and active Ca2+ transport, whereas spermine and the CaR-selective calcimimetic NPS R-467 were without effect. We conclude that small increases in divalent cation concentration elicit CaR-independent increases in TER and inhibit passive Ca2+ transport across Caco-2 monolayers, most probably through a direct effect on tight junction permeability. Whilst it is known that the complete removal of Ca(o)2+ lowers TER, here we show that Ca(o)2+ addition actually increases TER in a concentration-dependent manner. Therefore, such Ca(o)2+-sensitivity could modulate intestinal solute transport including the limiting of excess Ca2+ absorption.

Triple-functional core-shell structured upconversion luminescent nanoparticles covalently grafted with photosensitizer for luminescent, magnetic resonance imaging and photodynamic therapy in vitro

NASA Astrophysics Data System (ADS)

Qiao, Xiao-Fei; Zhou, Jia-Cai; Xiao, Jia-Wen; Wang, Ye-Fu; Sun, Ling-Dong; Yan, Chun-Hua

2012-07-01

Upconversion luminescent nanoparticles (UCNPs) have been widely used in many biochemical fields, due to their characteristic large anti-Stokes shifts, narrow emission bands, deep tissue penetration and minimal background interference. UCNPs-derived multifunctional materials that integrate the merits of UCNPs and other functional entities have also attracted extensive attention. Here in this paper we present a core-shell structured nanomaterial, namely, NaGdF4:Yb,Er@CaF2@SiO2-PS, which is multifunctional in the fields of photodynamic therapy (PDT), magnetic resonance imaging (MRI) and fluorescence/luminescence imaging. The NaGdF4:Yb,Er@CaF2 nanophosphors (10 nm in diameter) were prepared via sequential thermolysis, and mesoporous silica was coated as shell layer, in which photosensitizer (PS, hematoporphyrin and silicon phthalocyanine dihydroxide) was covalently grafted. The silica shell improved the dispersibility of hydrophobic PS molecules in aqueous environments, and the covalent linkage stably anchored the PS molecules in the silica shell. Under excitation at 980 nm, the as-fabricated nanomaterial gave luminescence bands at 550 nm and 660 nm. One luminescent peak could be used for fluorescence imaging and the other was suitable for the absorption of PS to generate singlet oxygen for killing cancer cells. The PDT performance was investigated using a singlet oxygen indicator, and was investigated in vitro in HeLa cells using a fluorescent probe. Meanwhile, the nanomaterial displayed low dark cytotoxicity and near-infrared (NIR) image in HeLa cells. Further, benefiting from the paramagnetic Gd3+ ions in the core, the nanomaterial could be used as a contrast agent for magnetic resonance imaging (MRI). Compared with the clinical commercial contrast agent Gd-DTPA, the as-fabricated nanomaterial showed a comparable longitudinal relaxivities value (r1) and similar imaging effect.Upconversion luminescent nanoparticles (UCNPs) have been widely used in many biochemical fields, due to their characteristic large anti-Stokes shifts, narrow emission bands, deep tissue penetration and minimal background interference. UCNPs-derived multifunctional materials that integrate the merits of UCNPs and other functional entities have also attracted extensive attention. Here in this paper we present a core-shell structured nanomaterial, namely, NaGdF4:Yb,Er@CaF2@SiO2-PS, which is multifunctional in the fields of photodynamic therapy (PDT), magnetic resonance imaging (MRI) and fluorescence/luminescence imaging. The NaGdF4:Yb,Er@CaF2 nanophosphors (10 nm in diameter) were prepared via sequential thermolysis, and mesoporous silica was coated as shell layer, in which photosensitizer (PS, hematoporphyrin and silicon phthalocyanine dihydroxide) was covalently grafted. The silica shell improved the dispersibility of hydrophobic PS molecules in aqueous environments, and the covalent linkage stably anchored the PS molecules in the silica shell. Under excitation at 980 nm, the as-fabricated nanomaterial gave luminescence bands at 550 nm and 660 nm. One luminescent peak could be used for fluorescence imaging and the other was suitable for the absorption of PS to generate singlet oxygen for killing cancer cells. The PDT performance was investigated using a singlet oxygen indicator, and was investigated in vitro in HeLa cells using a fluorescent probe. Meanwhile, the nanomaterial displayed low dark cytotoxicity and near-infrared (NIR) image in HeLa cells. Further, benefiting from the paramagnetic Gd3+ ions in the core, the nanomaterial could be used as a contrast agent for magnetic resonance imaging (MRI). Compared with the clinical commercial contrast agent Gd-DTPA, the as-fabricated nanomaterial showed a comparable longitudinal relaxivities value (r1) and similar imaging effect. Electronic supplementary information (ESI) available: More TEM, emission spectra, longitudinal and transverse relaxation times, t2-weighted MR images of the as-prepared nanomaterial, and confocal fluorescent images of HeLa cells. See DOI: 10.1039/c2nr30938f

Use of calcitriol to maintain postpartum blood calcium and improve immune function in dairy cows.

PubMed

Vieira-Neto, A; Lima, I R P; Lopes, F; Lopera, C; Zimpel, R; Sinedino, L D P; Jeong, K C; Galvão, K; Thatcher, W W; Nelson, C D; Santos, J E P

2017-07-01

Our objectives were to determine the effects of an injectable formulation of calcitriol on mineral metabolism and immune function in postpartum Holstein cows that received an acidogenic diet prepartum to minimize hypocalcemia. In experiment 1, cows within 6 h of calving received calcitriol (0, 200, or 300 μg) to determine the dose needed to increase plasma concentrations of Ca; 300 μg was sufficient to sustain Ca for at least 3 d. In experiment 2, multiparous cows were assigned randomly to receive only vehicle (control, n = 25) or 300 μg of calcitriol (n = 25) subcutaneously within the first 6 h after calving. Blood was sampled before treatment and 12 h later, then daily until 15 d in milk (DIM), and analyzed for concentrations of ionized Ca (iCa), total Ca (tCa), total Mg (tMg), and total P (tP), metabolites, and hormones. Urine was sampled in the first 7 DIM and analyzed for concentrations of tCa, tMg, and creatinine. Neutrophil function was evaluated in the first week postpartum. Dry matter intake and production performance were evaluated for the first 36 DIM. Calcitriol administration increased concentrations of calcitriol in plasma within 12 h of application from 51 to 427 pg/mL, which returned to baseline within 5 d. Concentrations of iCa and tCa increased 24 h after treatment with calcitriol. Concentrations of iCa (control = 1.08 vs. calcitriol = 1.20 mM), tCa (control = 2.23 vs. calcitriol = 2.33 mM), and tP (control = 1.47 vs. calcitriol = 1.81 mM) remained elevated in cows treated with calcitriol until 3, 5, and 7 DIM, respectively, whereas concentration of tMg (control = 0.76 vs. calcitriol = 0.67 mM) was less in calcitriol cows than control cows until 3 DIM. Concentrations of parathyroid hormone decreased in calcitriol cows compared with control cows (control = 441 vs. calcitriol = 336 pg/mL). Calcitriol tended to increase plasma concentrations of β-hydroxybutyrate and serotonin, but concentrations of glucose, nonesterified fatty acids, and C-telopeptide of type I collagen in plasma did not differ between treatments. Cows treated with calcitriol excreted more urinary tCa (control = 0.5 vs. calcitriol = 2.1 g/d) and tMg (control = 4.5 vs. calcitriol = 5.0 g/d) in the first 7 and 2 DIM, respectively, than control cows. Compared with control, calcitriol improved the proportion of neutrophils with oxidative burst (control = 31.9 vs. calcitriol = 40.6%), mean fluorescence intensity for oxidative burst (control = 90,900 vs. calcitriol = 99,746), and mean fluorescence intensity for phagocytosis (control = 23,887 vs. calcitriol = 28,080). Dry matter intake, yields of milk, and milk components did not differ between treatments. Administration of 300 μg of calcitriol at calving was safe and effective in increasing blood concentration of iCa and plasma concentrations of calcitriol, tCa, and tP for the first 6 d after treatment, and improved measures of innate immune function in early-lactation Holstein cows. Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Ciguatoxin extracted from poisonous moray eels Gymnothorax javanicus triggers acetylcholine release from Torpedo cholinergic synaptosomes via reversed Na(+)-Ca2+ exchange.

PubMed

Molgó, J; Gaudry-Talarmain, Y M; Legrand, A M; Moulian, N

1993-09-17

Ciguatoxin (CTX) (0.1 pM to 10 nM) added to a suspension of Torpedo synaptosomes incubated in Ca(2+)-free medium caused no detectable acetylcholine (ACh) release. However, subsequent addition of Ca2+ caused a large ACh release that depended on time of exposure, dose of CTX and on [Ca2+]. Tetrodotoxin completely prevented CTX-induced Ca(2+)-dependent ACh release. Simultaneous blockade of Ca2+ channel subtypes by FTX, a toxin extracted from the venom of the spider Agelenopsis aperta, omega-conotoxin and Gd3+ did not prevent ACh release caused by CTX, upon addition of Ca2+. These results suggest that CTX activates the reversed operation of the Na+/Ca2+ exchange system allowing the entry of Ca2+ in exchange for Na+. It is concluded that Torpedo synaptosomes are endowed with Na+ channels sensitive to pico- to nanomolar concentrations of CTX.

New Crystalline Materials for Nonlinear Frequency Conversion, Electro-Optic Modulation, and Mid-Infrared Gain Media

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

Adams, J

New crystalline materials were investigated for applications in frequency conversion of near-infrared wavelengths and as gain media for tunable mid-infrared solid-state lasers. GaCa{sub 4}O(BO{sub 3}){sub 3} (GdCOB), YCa{sub 4}O(BO{sub 3}){sub 3} (YCOB), LaCa{sub 4}O(BO{sub 3}){sub 3} (LaCOB), and Gd{sub 0.275}Y{sub 0.725}Ca{sub 4}O(BO{sub 3}){sub 3} were characterized for frequency conversion of 1 {micro}m lasers. For type I doubling at 1064 nm, LaCOB, GdCOB, and YCOB were found to have effective coupling coefficients (d{sub eff}) of 0.52 {+-} 0.05, 0.78 {+-} 0.06, and 1.12 {+-} 0.07 pm/V, respectively. LaCOB was measured to have angular and thermal sensitivities of 1224 {+-} 184 (cm-rad){supmore » -1} and < 0.10 (cm-{sup o}C){sup -1}, respectively. The effective coupling coefficient for type II noncritically phasematched (NCPM) doubling at 1064 nm in Gd{sub 0.275}Y{sub 0.725}Ca{sub 4}O(BO{sub 3}){sub 3} was measured to be 0.37 {+-} 0.04 pm/V. We predict LaCOB to have a type I NCPM fundamental wavelength of 1042 {+-} 1.5 nm. Due to its low angular and thermal sensitivities for doubling near 1047 nm, LaCOB has potential for frequency doubling of high-average power Nd:LiYF{sub 4} and Yb:Sr{sub 5}(P0{sub 4}){sub 3}F lasers. LaCOB, GdCOB, and YCOB were also investigated for optical parametric oscillator applications and we determined that they may have potential in a Ti:sapphire pumped oscillator. The effective linear electro-optic coefficients (r{sub eff}) were measured along dielectric directions in YCOB and a maximum r{sub eff} of 10.8 pm/V was found. For a crystal with a 5:1 aspect ratio, the corresponding half-wave voltage at 1064 nm would be 19.6 kV. Therefore a Pockels cell composed of two YCOB crystals with 5:1 aspect ratios would have a required half-wave voltage <10 kV. Moderate coupling coefficients (3 x KH{sub 2}PO{sub 4}), low thermal sensitivities, ease of growth to large sizes, non-hygroscopicity, and favorable polishing and coating characteristics make LaCOB, GdCOB, and YCOB attractive for frequency conversion of high-average power near-infrared lasers. Absorption and emission cross-sections of {approx}10{sup -18} cm{sup 2} were measured for Fe{sup 2+}:ZnSe in the 4 {micro}m region at temperatures below 220 K. Luminescence lifetimes were found that ranged from 5-110 {micro}s below 220 K. Tunable lasing action was demonstrated for the first time in Fe{sup 2+}:ZnSe with a tuning range from 3.98 {micro}m (20 K) to 4.54 {micro}m (180 K). The Fe{sup 2+}:ZnSe laser had thresholds {le}50 {micro}J and slope efficiencies {le}10% with 0.6% output coupling.« less

64Cu-DOTA as a surrogate positron analog of Gd-DOTA for cardiac fibrosis detection with PET: Pharmacokinetic study in a rat model of chronic MI

PubMed Central

Kim, Heejung; Lee, Sung-Jin; Davies-Venn, Cynthia; Kim, Jin Su; Yang, Bo Yeun; Yao, Zhengsheng; Kim, Insook; Paik, Chang H.; Bluemke, David A.

2015-01-01

Objectives To investigate the pharmacokinetics of 64Cu-DOTA, a positron surrogate analog of late Gd-enhancement cardiac magnetic resonance agent, Gd-DOTA in a rat model of chronic myocardial infarction (MI) and its microdistribution in the cardiac fibrosis by autoradiography. Methods DOTA was labeled with 64Cu-acetate. CD rats (n = 5) with MI by LAD ligation and normal rats (n = 6) were injected iv with the 64Cu-DOTA (18.5 MBq, 0.02 mmol DOTA/Kg). Dynamic PET imaging was performed for 60 min after injection. [18F]-FDG PET imaging was performed to identify the viable myocardium. For the ROI analysis, the 64Cu PET image was co-registered to the [18F]-FDG PET image. To validate the PET images, slices of heart samples from the base to the apex were analyzed using autoradiography and histological staining with Masson’s trichrome. Results 64Cu-DOTA was rapidly taken up in the infarct area. The time-activity curves demonstrated that the 64Cu-DOTA concentrations in blood, the fibrotic tissue and perfusion-rich organs peaked within a minute of post injection and thereafter rapidly washed out in parallel with the blood clearance and excreted via the renal system. The blood clearance curve was bi-phasic, with the distribution half-life of < 3 min and the elimination half-life of ~ 21.8 min. The elimination half-life of 64Cu-DOTA from the focal fibrotic tissue (~ 22.4 min) and the remote myocardium (~ 20.1 min) was similar to the blood elimination half-life. Consequently, the uptake ratios of focal fibrosis-to-blood and remote myocardium-to-blood remained stable for the time period between 10 to 60 min. The corresponding ratios obtained from images acquired from 30 to 60 min were 1.09 and 0.59, respectively, indicating that the concentration of 64Cu-DOTA in the focal fibrosis was 1.85 (1.09/0.59) times greater than in remote myocardium. Thus, this finding indicates that the extracellular volume fraction was 1.85 times greater in the focal fibrosis than in remote myocardium. The accumulation of 64Cu-DOTA in fibrotic tissue was further supported by autoradiography and histology images. The autoradiography images of 64Cu-DOTA in fibrotic tissues were qualitatively superimposed over the histology images of the fibrotic tissues. The histology images of the infarct areas were characterized by a heterogeneous distribution of thin bands of fibrotic-collagen, myocytes, and expanded extracellular space. Conclusion 64Cu-DOTA is a useful surrogate positron analog of Gd-DOTA, enabling to quantitatively measure the uptake values in fibrotic tissues by the dynamic PET imaging and calculate the extracellular volume fractions of the fibrotic tissues. At a microscopic level, the distribution of 64Cu-DOTA is non-uniform, corresponding to the heterogeneous distribution of expanded extracellular space in the setting of myocardial infarction. PMID:26488428

Evidence from mathematical modeling that carbonic anhydrase II and IV enhance CO2 fluxes across Xenopus oocyte plasma membranes

PubMed Central

Musa-Aziz, Raif; Boron, Walter F.

2014-01-01

Exposing an oocyte to CO2/HCO3− causes intracellular pH (pHi) to decline and extracellular-surface pH (pHS) to rise to a peak and decay. The two companion papers showed that oocytes injected with cytosolic carbonic anhydrase II (CA II) or expressing surface CA IV exhibit increased maximal rate of pHi change (dpHi/dt)max, increased maximal pHS changes (ΔpHS), and decreased time constants for pHi decline and pHS decay. Here we investigate these results using refinements of an earlier mathematical model of CO2 influx into a spherical cell. Refinements include 1) reduced cytosolic water content, 2) reduced cytosolic diffusion constants, 3) refined CA II activity, 4) layer of intracellular vesicles, 5) reduced membrane CO2 permeability, 6) microvilli, 7) refined CA IV activity, 8) a vitelline membrane, and 9) a new simulation protocol for delivering and removing the bulk extracellular CO2/HCO3− solution. We show how these features affect the simulated pHi and pHS transients and use the refined model with the experimental data for 1.5% CO2/10 mM HCO3− (pHo = 7.5) to find parameter values that approximate ΔpHS, the time to peak pHS, the time delay to the start of the pHi change, (dpHi/dt)max, and the change in steady-state pHi. We validate the revised model against data collected as we vary levels of CO2/HCO3− or of extracellular HEPES buffer. The model confirms the hypothesis that CA II and CA IV enhance transmembrane CO2 fluxes by maximizing CO2 gradients across the plasma membrane, and it predicts that the pH effects of simultaneously implementing intracellular and extracellular-surface CA are supra-additive. PMID:24965589

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

PubMed

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

2003-03-01

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

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

Properties of the calcium-activated chloride current in heart.

PubMed

Zygmunt, A C; Gibbons, W R

1992-03-01

We used the whole cell patch clamp technique to study transient outward currents of single rabbit atrial cells. A large transient current, IA, was blocked by 4-aminopyridine (4AP) and/or by depolarized holding potentials. After block of IA, a smaller transient current remained. It was completely blocked by nisoldipine, cadmium, ryanodine, or caffeine, which indicates that all of the 4AP-resistant current is activated by the calcium transient that causes contraction. Neither calcium-activated potassium current nor calcium-activated nonspecific cation current appeared to contribute to the 4AP-resistant transient current. The transient current disappeared when ECl was made equal to the pulse potential; it was present in potassium-free internal and external solutions. It was blocked by the anion transport blockers SITS and DIDS, and the reversal potential of instantaneous current-voltage relations varied with extracellular chloride as predicted for a chloride-selective conductance. We concluded that the 4AP-resistant transient outward current of atrial cells is produced by a calcium-activated chloride current like the current ICl(Ca) of ventricular cells (1991. Circulation Research. 68:424-437). ICl(Ca) in atrial cells demonstrated outward rectification, even when intracellular chloride concentration was higher than extracellular. When ICa was inactivated or allowed to recover from inactivation, amplitudes of ICl(Ca) and ICa were closely correlated. The results were consistent with the view that ICl(Ca) does not undergo independent inactivation. Tentatively, we propose that ICl(Ca) is transient because it is activated by an intracellular calcium transient. Lowering extracellular sodium increased the peak outward transient current. The current was insensitive to the choice of sodium substitute. Because a recently identified time-independent, adrenergically activated chloride current in heart is reduced in low sodium, these data suggest that the two chloride currents are produced by different populations of channels.

Calcium homeostasis in crustaceans: subcellular Ca dynamics.

PubMed

Wheatly, M G; Zanotto, F P; Hubbard, M G

2002-05-01

The molting cycle of crustaceans, associated with renewal and remineralization of the cuticle, has emerged as a model system to study regulation of genes that code for Ca(2+)-transporting proteins, common to all eukaryotic cells. This article reviews state-of-the-art knowledge about how crustacean transporting epithelia (gills, hepatopancreas and antennal gland) effect mass transcellular movement of Ca(2+) while preventing cytotoxicity. The current model proposed is based on in vitro research on the intermolt stage with extrapolation to other molting stages. Plasma membrane proteins involved in apical and basolateral Ca(2+) movement (NCX, PMCA) are contrasted between aquatic species of different osmotic origin and among transporting epithelia of an individual species. Their roles are assessed in the context of epithelial Ca(2+) flux derived from organismic approaches. Exchange with extracellular environments is integrated with Ca(2+) sequestration mechanisms across endomembranes of the ER/SR and mitochondria. Finally, the review postulates how new Ca(2+) imaging techniques will allow spatial and temporal resolution of Ca(2+) concentration in subcellular domains.

Epileptiform activity induced by lowering extracellular [Mg2+] in combined hippocampal-entorhinal cortex slices: modulation by receptors for norepinephrine and N-methyl-D-aspartate.

PubMed

Stanton, P K; Jones, R S; Mody, I; Heinemann, U

1987-01-01

Reduction of extracellular Mg2+ concentration induced spontaneous and evoked epileptiform activity in the entorhinal cortex (EC) and dentate gyrus (DG) of combined hippocampus (HC)-EC slices. Extracellular field potentials, as well as changes in extracellular Ca2+ and K+ concentrations, were measured in EC and DG with ion-selective/reference electrodes during both repetitive and single stimuli. In the EC, lowering extracellular [Mg2+] induces both spontaneous and single stimulus evoked ictal events consisting of extracellular negative potential shifts (up to 5 mV, 30 sec), decreases in [Ca2+]0 and increases in [K+]0. In the DG, spontaneous events were much shorter, but similar changes in [Ca2+]0, [K+]0 and field potentials (FPs) could be evoked by brief high-frequency stimulation. In both areas, the N-methyl-D-aspartate (NMDA) receptor antagonist 2-aminophosphonovalerate (2-APV) completely blocked spontaneous as well as stimulus evoked epileptiform events. The neurotransmitter norepinephrine (NE), which has previously been shown to modulate long-term potentiation in the DG, was found to exhibit differential modulation of epileptiform activity in the EC and DG. In the EC, NE, acting via alpha 1-receptors, completely blocked low Mg2+-induced epileptiform activity. In contrast, in the DG, NE exhibited a beta-receptor mediated prolongation of the low Mg2+-induced ictal events, and enhanced the stimulus-induced ionic and field potential changes. From these results, we conclude that lowering extracellular [Mg2+], acting in large part through the removal of the Mg2+ voltage-dependent blockade of NMDA receptors, leads to induction of epileptiform activity in both the EC and DG.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Mechanosensory calcium-selective cation channels in epidermal cells

NASA Technical Reports Server (NTRS)

Ding, J. P.; Pickard, B. G.

1993-01-01

This paper explores the properties and likely functions of an epidermal Ca(2+)-selective cation channel complex activated by tension. As many as eight or nine linked or linkable equivalent conductance units or co-channels can open together. Open time for co-channel quadruplets and quintuplets tends to be relatively long with millimolar Mg2+ (but not millimolar Ca2+) at the cytosolic face of excised plasma membrane. Sensitivity to tension is regulated by transmembrane voltage and temperature. Under some circumstances channel activity is sychronized in rhythmic pulses. Certain lanthanides and a cytoskeleton-disturbing herbicide that inhibit gravitropic reception act on the channel system at low concentrations. Specifically, ethyl-N-phenylcarbamate promotes tension-dependent activity at micromolar levels. With moderate suction, Gd3+ provided at about 0.5 micromole at the extracellular face of the membrane promotes for several seconds but may then become inhibitory. Provision at 1-2 micromoles promotes and subsequently inhibits more vigorously (often abruptly and totally), and at high levels inhibits immediately. La3+, a poor gravitropic inhibitor, acts similarly but much more gradually and only at much higher concentrations. These properties, particularly these susceptibilities to modulation, indicate that in vivo the mechanosensitive channel must be mechanosensory and mechanoregulatory. It could serve to transduce the shear forces generated in the integrated wall-membrane-cytoskeleton system during turgor changes and cell expansion as well as transducing the stresses induced by gravity, touch and flexure. In so far as such transduction is modulated by voltage and temperature, the channels would also be sensors for these modalities as long as the wall-membrane-cytoskeleton system experiences mechanical stress.

Voltage Dependence of a Neuromodulator-Activated Ionic Current.

PubMed

Gray, Michael; Golowasch, Jorge

2016-01-01

The neuromodulatory inward current (IMI) generated by crab Cancer borealis stomatogastric ganglion neurons is an inward current whose voltage dependence has been shown to be crucial in the activation of oscillatory activity of the pyloric network of this system. It has been previously shown that IMI loses its voltage dependence in conditions of low extracellular calcium, but that this effect appears to be regulated by intracellular calmodulin. Voltage dependence is only rarely regulated by intracellular signaling mechanisms. Here we address the hypothesis that the voltage dependence of IMI is mediated by intracellular signaling pathways activated by extracellular calcium. We demonstrate that calmodulin inhibitors and a ryanodine antagonist can reduce IMI voltage dependence in normal Ca(2+), but that, in conditions of low Ca(2+), calmodulin activators do not restore IMI voltage dependence. Further, we show evidence that CaMKII alters IMI voltage dependence. These results suggest that calmodulin is necessary but not sufficient for IMI voltage dependence. We therefore hypothesize that the Ca(2+)/calmodulin requirement for IMI voltage dependence is due to an active sensing of extracellular calcium by a GPCR family calcium-sensing receptor (CaSR) and that the reduction in IMI voltage dependence by a calmodulin inhibitor is due to CaSR endocytosis. Supporting this, preincubation with an endocytosis inhibitor prevented W7 (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride)-induced loss of IMI voltage dependence, and a CaSR antagonist reduced IMI voltage dependence. Additionally, myosin light chain kinase, which is known to act downstream of the CaSR, seems to play a role in regulating IMI voltage dependence. Finally, a Gβγ-subunit inhibitor also affects IMI voltage dependence, in support of the hypothesis that this process is regulated by a G-protein-coupled CaSR.

Voltage Dependence of a Neuromodulator-Activated Ionic Current123

PubMed Central

2016-01-01

Abstract The neuromodulatory inward current (IMI) generated by crab Cancer borealis stomatogastric ganglion neurons is an inward current whose voltage dependence has been shown to be crucial in the activation of oscillatory activity of the pyloric network of this system. It has been previously shown that IMI loses its voltage dependence in conditions of low extracellular calcium, but that this effect appears to be regulated by intracellular calmodulin. Voltage dependence is only rarely regulated by intracellular signaling mechanisms. Here we address the hypothesis that the voltage dependence of IMI is mediated by intracellular signaling pathways activated by extracellular calcium. We demonstrate that calmodulin inhibitors and a ryanodine antagonist can reduce IMI voltage dependence in normal Ca2+, but that, in conditions of low Ca2+, calmodulin activators do not restore IMI voltage dependence. Further, we show evidence that CaMKII alters IMI voltage dependence. These results suggest that calmodulin is necessary but not sufficient for IMI voltage dependence. We therefore hypothesize that the Ca2+/calmodulin requirement for IMI voltage dependence is due to an active sensing of extracellular calcium by a GPCR family calcium-sensing receptor (CaSR) and that the reduction in IMI voltage dependence by a calmodulin inhibitor is due to CaSR endocytosis. Supporting this, preincubation with an endocytosis inhibitor prevented W7 (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride)-induced loss of IMI voltage dependence, and a CaSR antagonist reduced IMI voltage dependence. Additionally, myosin light chain kinase, which is known to act downstream of the CaSR, seems to play a role in regulating IMI voltage dependence. Finally, a Gβγ-subunit inhibitor also affects IMI voltage dependence, in support of the hypothesis that this process is regulated by a G-protein-coupled CaSR. PMID:27257619

Yeast respond to hypotonic shock with a calcium pulse

NASA Technical Reports Server (NTRS)

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

1996-01-01

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

Electrophysiological and optical changes in slices of rat hippocampus during spreading depression.

PubMed

Snow, R W; Taylor, C P; Dudek, F E

1983-09-01

Spreading depression (SD) was studied with intracellular and extracellular recordings and with photometry in slices of rat hippocampus. Repetitive electrical stimulation could initiate SD in either normal medium or in low-Ca2+ medium containing Mn2+, especially during transient hypoxia. The extracellular voltage near CA1 pyramidal somata and dendrites became negative by approximately 18 mV during SD. This negativity peaked more slowly in low-Ca2+ medium containing Mn2+. The wave of negativity propagated across the slice in both media at approximately 6 mm/min. Input resistance of pyramidal neurons became undetectable during SD, and differential voltage recording between neurons and adjacent extracellular space demonstrated that transmembrane potential approached zero. Slices became more opaque during SD. Photometry revealed approximately 10% increase in reflectance and a similar decrease in transmittance of white light, which occurred with a time course similar to the extracellularly recorded voltage shift. These data support the hypothesis that SD represents a large increase in membrane permeability associated with substantial movements of water. The persistance of SD in a bathing solution that blocked electrically evoked postsynaptic potentials suggests that the contribution of synaptic transmitter release to the propagation of SD should be reappraised.

Spin-phonon and lattice contributions to the ground-state splitting of Gd3+ and Eu2+ in scheelite crystals

NASA Astrophysics Data System (ADS)

Gorlov, A. D.

2015-07-01

The EPR spectra of Gd3+ in CaWO4 single crystals have been studied at temperatures T = 1.8, 4.2, and 114-300 K, and the temperature dependence of the parameters b {/n m } ( T) of the spin Hamiltonian has been found. The behavior of b {2/0}( T) has been analyzed. The spin-phonon and static lattice contributions b {2/0}( F) and b {2/0}( L) to b {2/0}( T) have been revealed. For this purpose, the variation of b {2/0}( L) has been calculated taking into account the thermal shifts of oxygen ions in CaWO4. Similar analysis has been carried out for CaWO4: Eu2+ based on the EPR data of other authors (Bronstein, Voterra and Harvey, Kiefte). It has been shown that at b {2/0}( F) > 0, the variation of b {2/0}( F) as a function of T for these impurity centers is described well by the Pfister model and a sign change of b {2/0}( T) for Eu2+ is determined by thermal expansion of the lattice.

Participation of IP3R, RyR and L-type Ca2+ channel in the nuclear maturation of Rhinella arenarum oocytes.

PubMed

Toranzo, G Sánchez; Bühler, M C Gramajo; Bühler, M I

2014-05-01

During meiosis resumption, oocytes undergo a series of nuclear and cytosolic changes that prepare them for fertilization and that are referred to as oocyte maturation. These events are characterized by germinal vesicle breakdown (GVBD), chromatin condensation and spindle formation and, among cytosolic changes, organelle redistribution and maturation of Ca2+-release mechanisms. The progression of the meiotic cell cycle is regulated by M phase/maturation-promoting factor (MPF) and mitogen-activated protein kinase (MAPK). Changes in the levels of intracellular free Ca2+ ion have also been implicated strongly in the triggering of the initiation of the M phase. Ca2+ signals can be generated by Ca2+ release from intracellular Ca2+ stores (endoplasmic reticulum; ER) or by Ca2+ influx from the extracellular space. In this sense, the L-type Ca2+ channel plays an important role in the incorporation of Ca2+ from the extracellular space. Two types of intracellular Ca2+ receptor/channels are known to mediate the intracellular Ca2+ release from the ER lumen. The most abundant, the inositol 1,4,5-trisphosphate receptor (IP3R), and the other Ca2+ channel, the ryanodine receptor (RyR), have also been reported to mediate Ca2+ release in several oocytes. In amphibians, MPF and MAPK play a central role during oocyte maturation, controlling several events. However, no definitive relationships have been identified between Ca2+ and MPF or MAPK. We investigated the participation of Ca2+ in the spontaneous and progesterone-induced nuclear maturation in Rhinella arenarum oocytes and the effect of different pharmacological agents known to produce modifications in the Ca2+ channels. We demonstrated that loading competent and incompetent oocytes with the intracellular calcium chelator BAPTA/AM produced suppression of spontaneous and progesterone-induced GVBD. In our results, the capacity of progesterone to trigger meiosis reinitiation in Rhinella in the presence of L-type Ca2+ channel blockers (nifedipine and lanthane) indicated that spontaneous and progesterone-induced maturation would be independent of extracellular calcium influx, but would be sensitive to intracellular Ca2+ deprivation. As demonstrated by the effect of thimerosal and heparin in Rhinella arenarum, the intracellular increase in Ca2+ during maturation is also mediated mainly by IP3R. In addition, our results using caffeine, an agonist of the RyR, could suggest that Ca2+ release from ryanodine-sensitive stores is not essential for oocyte maturation in Rhinella. The decrease in MPF activity with NaVO3 negatively affected the percentage of thimerosal-induced GVBD. This finding suggests that Ca2+ release through the IP3R could be involved in the signalling pathway that induces MPF activation. However, the inhibition of MAP/ERK kinase (MEK) by PD98128 or P90 by geldanamycin produced a significant decrease in the percentages of GVBD induced by thimerosal. This finding suggests that Ca2+ release per se cannot bypass the inhibition of the MAPK activity.

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.

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

PubMed

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

1996-11-01

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

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

PubMed

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

2002-10-01

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

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

PubMed Central

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

2002-01-01

Cell suspensions obtained from Nicotiana plumbaginifolia plants stably expressing the apoaequorin gene were used to analyze changes in cytosolic free calcium concentrations ([Ca2+]cyt) in response to elicitors of plant defenses, particularly cryptogein and oligogalacturonides. The calcium signatures differ in lag time, peak time, intensity, and duration. The intensities of both signatures depend on elicitor concentration and extracellular calcium concentration. Cryptogein signature is characterized by a long-sustained [Ca2+]cyt increase that should be responsible for sustained mitogen-activated protein kinase activation, microtubule depolymerization, defense gene activation, and cell death. The [Ca2+]cyt increase in elicitor-treated cells first results from a calcium influx, which in turns leads to calcium release from internal stores and additional Ca2+ influx. H2O2 resulting from the calcium-dependent activation of the NADPH oxidase also participates in [Ca2+]cyt increase and may activate calcium channels from the plasma membrane. Competition assays with different elicitins demonstrate that [Ca2+]cyt increase is mediated by cryptogein–receptor interaction. PMID:12368509

Active caspase-1 induces plasma membrane pores that precede pyroptotic lysis and are blocked by lanthanides#

PubMed Central

Russo, Hana M.; Rathkey, Joseph; Boyd-Tressler, Andrea; Katsnelson, Michael A.; Abbott, Derek W.; Dubyak, George R.

2016-01-01

Canonical inflammasome activation induces a caspase-1/gasdermin D (Gsdmd) dependent lytic cell death called pyroptosis which promotes anti-microbial host defense but may contribute to sepsis. The nature of the caspase-1-dependent change in plasma membrane (PM) permeability during pyroptotic progression remains incompletely defined. We assayed propidium2+ (Pro2+) influx kinetics during NLRP3 or Pyrin inflammasome activation in murine bone marrow-derived macrophages (BMDM) as an indicator of this PM permeabilization. BMDM were characterized by rapid Pro2+ influx after initiation of NLRP3 or Pyrin inflammasomes by nigericin or C. difficile toxin B (TcdB), respectively. No Pro2+ uptake in response to nigericin or TcdB was observed in Caspase-1−/− or ASC−/− BMDM. The cytoprotectant glycine profoundly suppressed nigericin and TcdB-induced lysis but not Pro2+ influx. The absence of Gsdmd expression resulted in suppression of nigericin-stimulated Pro2+ influx and pyroptotic lysis. Extracellular La3+ and Gd3+ rapidly and reversibly blocked the induced Pro2+ influx and markedly delayed pyroptotic lysis without limiting upstream inflammasome assembly and caspase-1 activation. Thus, caspase-1 driven pyroptosis requires induction of initial pre-lytic pores in the PM that are dependent on Gsdmd expression. These PM pores also facilitated the efflux of cytosolic ATP and influx of extracellular Ca2+. Although lanthanides and Gsdmd deletion both suppressed PM pore activity and pyroptotic lysis, robust IL-1β release was observed in lanthanide-treated BMDM but not in Gsdmd-deficient cells. This suggests roles for Gsdmd in both passive IL-1β release secondary to pyroptotic lysis and in non-lytic/non-classical IL-1β export. PMID:27385778

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.

Down-regulation of transmembrane carbonic anhydrases in renal cell carcinoma cell lines by wild-type von Hippel-Lindau transgenes

PubMed Central

Ivanov, Sergey V.; Kuzmin, Igor; Wei, Ming-Hui; Pack, Svetlana; Geil, Laura; Johnson, Bruce E.; Stanbridge, Eric J.; Lerman, Michael I.

1998-01-01

To discover genes involved in von Hippel-Lindau (VHL)-mediated carcinogenesis, we used renal cell carcinoma cell lines stably transfected with wild-type VHL-expressing transgenes. Large-scale RNA differential display technology applied to these cell lines identified several differentially expressed genes, including an alpha carbonic anhydrase gene, termed CA12. The deduced protein sequence was classified as a one-pass transmembrane CA possessing an apparently intact catalytic domain in the extracellular CA module. Reintroduced wild-type VHL strongly inhibited the overexpression of the CA12 gene in the parental renal cell carcinoma cell lines. Similar results were obtained with CA9, encoding another transmembrane CA with an intact catalytic domain. Although both domains of the VHL protein contribute to regulation of CA12 expression, the elongin binding domain alone could effectively regulate CA9 expression. We mapped CA12 and CA9 loci to chromosome bands 15q22 and 17q21.2 respectively, regions prone to amplification in some human cancers. Additional experiments are needed to define the role of CA IX and CA XII enzymes in the regulation of pH in the extracellular microenvironment and its potential impact on cancer cell growth. PMID:9770531

Cytosolic and mitochondrial [Ca2+] in whole hearts using indo-1 acetoxymethyl ester: effects of high extracellular Ca2+.

PubMed Central

Schreur, J H; Figueredo, V M; Miyamae, M; Shames, D M; Baker, A J; Camacho, S A

1996-01-01

Assessment of free cytosolic [Ca2+] ([Ca2+]c) using the acetoxymethyl ester (AM) form of indo-1 may be compromised by loading of indo-1 into noncytosolic compartments, primarily mitochondria. To determine the fraction of noncytosolic fluorescence in whole hearts loaded with indo-1 AM, Mn2+ was used to quench cytosolic fluorescence. Residual (i.e., noncytosolic) fluorescence was subtracted from the total fluorescence before calculating [Ca2+]c. Noncytosolic fluorescence was used to estimate mitochondrial [Ca2+]. In hearts paced at 5 Hz (N = 17), noncytosolic fluorescence was 0.61 +/- 0.06 and 0.56 +/- 0.07 of total fluorescence at lambda 385 and lambda 456, respectively. After taking into account noncytosolic fluorescence, systolic and diastolic [Ca2+]c was 673 +/- 72 and 132 +/- 9 nM, respectively, noncytosolic [Ca2+] was 183 +/- 36 nM and increased to 272 +/- 12 when extracellular Ca2+ was increased from 2 to 6 mM. This increase in noncytosolic [Ca2+] was inhibited by ruthenium red, a blocker of Ca2+ uptake by mitochondria. We conclude that cytosolic and mitochondrial [Ca2+] can be determined in whole hearts loaded with indo-1 AM by using Mn2+ to quench cytosolic fluorescence. PMID:8744296

Diode-Pumped Passively Mode-Locked 1079 nm Nd:CaGdAlO4 Laser

NASA Astrophysics Data System (ADS)

He, Kun-Na; Liu, Jia-Xing; Wei, Long; Xu, Xiao-Dong; Wang, Zhao-Hua; Tian, Wen-Long; Zhang, Zhi-Guo; Xu, Jun; Di, Ju-Qing; Xia, Chang-Tai; Wei, Zhi-Yi

2016-01-01

Not Available Supported by the National Key Basic Research Program of China under Grant No 2013CB922402, and the International Joint Research Program of the National Natural Science Foundation of China under Grant No 61210017.

Molecular and cellular aspects of calcium action in plants

NASA Technical Reports Server (NTRS)

Poovaiah, B. W.

1988-01-01

Calcium is known to be a second messenger in many developmental processes in animal systems, but it has only recently become evident that Ca is an important intracellular messenger in plants as well. The level of free Ca concentration in the cytoplasm is extremely low, and it is influenced by extracellular signals such as light, gravity, and hormones. Investigations from our laboratory indicated that Ca and its binding protein, calmodulin, play an important role in stimulus-response coupling by regulating enzyme activities, especially through protein phosphorylation. In vivo and in vitro protein phosphorylation studies have revealed Ca-dependent changes in various plant tissues. We have also been able to influence various physiological processes such as cell elongation, abscission, senescence, and tuberization by altering extracellular and intracellular Ca levels. Other examples of Ca-mediated processes in plants are as follows: a) cell division, b) geotropism, c) protoplasmic streaming, d) stomatal control, e) chloroplast movement, f) secretion, g) hormone-dependent changes, h) enzyme activation, and i) protein phosphorylation.

Comparison of neutrophil functions between two strains of inbred mice.

PubMed

Zhang, Xiaohuan; Zhao, Sainan; Sun, Luping; Li, Wenqing; Glogauer, Michael; Hu, Yan

2016-12-01

In this study, differences between two strains of inbred mice in aspects of neutrophil function, namely Rac1 expression, chemotaxis, nicotinamide adenine dinucleotide phosphate oxidase activity and formation of neutrophil extracellular traps (NETs), were determined. Neutrophils from CBA/CaH mice exhibited weaker Rac1 expression and a slower chemotactic gradient than BALB/c mice. Furthermore, PMA- or fMLP-stimulated neutrophils from CBA/CaH mice generated much less superoxide and NETs than similarly stimulated neutrophils from BALB/c mice. These findings suggest that neutrophils from BALB/c mice are functionally more efficient than those from CBA/CaH mice. © 2016 The Societies and John Wiley & Sons Australia, Ltd.

The Calcium-Sensing Receptor Couples to Gαs and Regulates PTHrP and ACTH Secretion in Pituitary Cells

PubMed Central

Mamillapalli, Ramanaiah; Wysolmerski, John

2013-01-01

The calcium-sensing receptor (CaR) is a G-protein-coupled receptor (GPCR) that binds and signals in response to extracellular calcium and other polycations. It is highly expressed on parathyroid and kidney cells, where it participates in the regulation of systemic calcium homeostasis. It is also expressed on many other cell types and is involved in a wide array of biological functions such as cell growth and differentiation, ion transport and hormone secretion. It has been described to couple to several different G-proteins including Gαi/0, Gαq/11 and Gα12/13. Recently, it has also been shown to stimulate cAMP production by coupling to Gαs in immortalized or malignant breast cells. The CaR is expressed on cells in the anterior pituitary and had previously been described to stimulate cAMP production in these cells. In this report, we examined signaling from the CaR in murine pituitary corticotroph-derived, AtT-20 cells. We found that CaR activation led to the stimulation of cAMP production, and PTHrP and ACTH secretion from these cells. Furthermore, manipulation of cAMP levels was able to modulate PTHrP and ACTH secretion independent of changes in extracellular calcium. Finally, we demonstrated that the CaR couples to Gαs in AtT-20 cells. Therefore, in pituitary corticotroph-like cells, as in breast cancer cells, the CaR utilizes Gαs and activates cAMP production to stimulate hormone secretion. PMID:20032198

Dissociation of intracellular lysosomal rupture from the cell death caused by silica

PubMed Central

Kane, AB; Stanton, RP; Raymond, EG; Dobson, ME; Knafelc, ME; Farber, JL

1980-01-01

The relationship between intracellular lysosomal rupture and cell death caused by silica was studied in P388d(1) macrophages. After 3 h of exposure to 150 μg silica in medium containing 1.8 mM Ca(2+), 60 percent of the cells were unable to exclude trypan blue. In the absence of extracellular Ca(2+), however, all of the cells remained viable. Phagocytosis of silica particles occurred to the same extent in the presence or absence of Ca(2+). The percentage of P388D(1) cells killed by silica depended on the dose and the concentration of Ca(2+) in the medium. Intracellular lyosomal rupture after exposure to silica was measured by acridine orange fluorescence or histochemical assay of horseradish peroxidase. With either assay, 60 percent of the cells exposed to 150 μg silica for 3 h in the presence of Ca(2+) showed intracellular lysosomal rupture, was not associated with measureable degradation of total DNA, RNA, protein, or phospholipids or accelerated turnover of exogenous horseradish peroxidase. Pretreatment with promethazine (20 μg/ml) protected 80 percent of P388D(1) macrophages against silica toxicity although lysosomal rupture occurred in 60-70 percent of the cells. Intracellular lysosomal rupture was prevented in 80 percent of the cells by pretreatment with indomethacin (5 x 10(-5)M), yet 40-50 percent of the cells died after 3 h of exposure to 150 μg silica in 1.8 mM extracellular Ca(2+). The calcium ionophore A23187 also caused intracellular lysosomal rupture in 90-98 percent of the cells treated for 1 h in either the presence or absence of extracellular Ca(2+). With the addition of 1.8 mM Ca(2+), 80 percent of the cells was killed after 3 h, whereas all of the cells remained viable in the absence of Ca(2+). These experiments suggest that intracellular lysosomal rupture is not causally related to the cell death cause by silica or A23187. Cell death is dependent on extracellular Ca(2+) and may be mediated by an influx of these ions across the plasma membrane permeability barrier damaged directly by exposure to these toxins. PMID:6161936

Modeling Tight Junction Dynamics and Oscillations

PubMed Central

Kassab, Fuad; Marques, Ricardo Paulino; Lacaz-Vieira, Francisco

2002-01-01

Tight junction (TJ) permeability responds to changes of extracellular Ca2+ concentration. This can be gauged through changes of the transepithelial electrical conductance (G) determined in the absence of apical Na+. The early events of TJ dynamics were evaluated by the fast Ca2+ switch assay (FCSA) (Lacaz-Vieira, 2000), which consists of opening the TJs by removing basal calcium (Ca2+ bl) and closing by returning Ca2+ bl to normal values. Oscillations of TJ permeability were observed when Ca2+ bl is removed in the presence of apical calcium (Ca2+ ap) and were interpreted as resulting from oscillations of a feedback control loop which involves: (a) a sensor (the Ca2+ binding sites of zonula adhaerens), (b) a control unit (the cell signaling machinery), and (c) an effector (the TJs). A mathematical model to explain the dynamical behavior of the TJs and oscillations was developed. The extracellular route (ER), which comprises the paracellular space in series with the submucosal interstitial fluid, was modeled as a continuous aqueous medium having the TJ as a controlled barrier located at its apical end. The ER was approximated as a linear array of cells. The most apical cell is separated from the apical solution by the TJ and this cell bears the Ca2+ binding sites of zonula adhaerens that control the TJs. According to the model, the control unit receives information from the Ca2+ binding sites and delivers a signal that regulates the TJ barrier. Ca2+ moves along the ER according to one-dimensional diffusion following Fick's second law. Across the TJ, Ca2+ diffusion follows Fick's first law. Our first approach was to simulate the experimental results in a semiquantitative way. The model tested against experiment results performed in the frog urinary bladder adequately predicts the responses obtained in different experimental conditions, such as: (a) TJ opening and closing in a FCSA, (b) opening by the presence of apical Ca2+ and attainment of a new steady-state, (c) the escape phase which follows the halt of TJ opening induced by apical Ca2+, (d) the oscillations of TJ permeability, and (e) the effect of Ca2+ ap concentration on the frequency of oscillations. PMID:12149284

Microbial excavation of solid carbonates powered by P-type ATPase-mediated transcellular Ca2+ transport.

PubMed

Garcia-Pichel, Ferran; Ramírez-Reinat, Edgardo; Gao, Qunjie

2010-12-14

Some microbes, among them a few species of cyanobacteria, are able to excavate carbonate minerals, from limestone to biogenic carbonates, including coral reefs, in a bioerosive activity that directly links biological and geological parts of the global carbon cycle. The physiological mechanisms that enable such endolithic cyanobacteria to bore, however, remain unknown. In fact, their boring constitutes a geochemical paradox, in that photoautotrophic metabolism will tend to precipitate carbonates, not dissolve them. We developed a stable microbe/mineral boring system based on a cyanobacterial isolate, strain BC008, with which to study the process of microbial excavation directly in the laboratory. Measurements of boring into calcite under different light regimes, and an analysis of photopigment content and photosynthetic rates along boring filaments, helped us reject mechanisms based on the spatial or temporal separation of alkali versus Acid-generating metabolism (i.e., photosynthesis and respiration). Instead, extracellular Ca(2+) imaging of boring cultures in vivo showed that BC008 was able to take up Ca(2+) at the excavation front, decreasing the local extracellular ion activity product of calcium carbonate enough to promote spontaneous dissolution there. Intracellular Ca(2+) was then transported away along the multicellular cyanobacterial trichomes and excreted at the distal borehole opening into the external medium. Inhibition assays and gene expression analyses indicate that the uptake and transport was driven by P-type Ca(2+)-ATPases. We believe such a chemically simple and biologically sophisticated mechanism for boring to be unparalleled among bacteria.

An autocrine ATP release mechanism regulates basal ciliary activity in airway epithelium.

PubMed

Droguett, Karla; Rios, Mariana; Carreño, Daniela V; Navarrete, Camilo; Fuentes, Christian; Villalón, Manuel; Barrera, Nelson P

2017-07-15

Extracellular ATP, in association with [Ca 2+ ] i regulation, is required to maintain basal ciliary beat frequency. Increasing extracellular ATP levels increases ciliary beating in airway epithelial cells, maintaining a sustained response by inducing the release of additional ATP. Extracellular ATP levels in the millimolar range, previously associated with pathophysiological conditions of the airway epithelium, produce a transient arrest of ciliary activity. The regulation of ciliary beat frequency is dependent on ATP release by hemichannels (connexin/pannexin) and P2X receptor activation, the blockage of which may even stop ciliary movement. The force exerted by cilia, measured by atomic force microscopy, is reduced following extracellular ATP hydrolysis. This result complements the current understanding of the ciliary beating regulatory mechanism, with special relevance to inflammatory diseases of the airway epithelium that affect mucociliary clearance. Extracellular nucleotides, including ATP, are locally released by the airway epithelium and stimulate ciliary activity in a [Ca 2+ ] i -dependent manner after mechanical stimulation of ciliated cells. However, it is unclear whether the ATP released is involved in regulating basal ciliary activity and mediating changes in ciliary activity in response to chemical stimulation. In the present study, we evaluated ciliary beat frequency (CBF) and ciliary beating forces in primary cultures from mouse tracheal epithelium, using videomicroscopy and atomic force microscopy (AFM), respectively. Extracellular ATP levels and [Ca 2+ ] i were measured by luminometric and fluorimetric assays, respectively. Uptake of ethidium bromide was measured to evaluate hemichannel functionality. We show that hydrolysis of constitutive extracellular ATP levels with apyrase (50 U ml -1 ) reduced basal CBF by 45% and ciliary force by 67%. The apyrase effect on CBF was potentiated by carbenoxolone, a hemichannel inhibitor, and oxidized ATP, an antagonist used to block P2X7 receptors, which reduced basal CBF by 85%. Additionally, increasing extracellular ATP levels (0.1-100 μm) increased CBF, maintaining a sustained response that was suppressed in the presence of carbenoxolone. We also show that high levels of ATP (1 mm), associated with inflammatory conditions, lowered basal CBF by reducing [Ca 2+ ] i and hemichannel functionality. In summary, we provide evidence indicating that airway epithelium ATP release is the molecular autocrine mechanism regulating basal ciliary activity and is also the mediator of the ciliary response to chemical stimulation. © 2017 The Authors. The Journal of Physiology © 2017 The Physiological Society.

A Coordination Chemistry Approach to Fine-Tune the Physicochemical Parameters of Lanthanide Complexes Relevant to Medical Applications.

PubMed

Le Fur, Mariane; Molnár, Enikő; Beyler, Maryline; Kálmán, Ferenc K; Fougère, Olivier; Esteban-Gómez, David; Rousseaux, Olivier; Tripier, Raphaël; Tircsó, Gyula; Platas-Iglesias, Carlos

2018-03-02

The geometric features of two pyclen-based ligands possessing identical donor atoms but different site organization have a profound impact in their complexation properties toward lanthanide ions. The ligand containing two acetate groups and a picolinate arm arranged in a symmetrical fashion (L1) forms a Gd 3+ complex being two orders of magnitude less stable than its dissymmetric analogue GdL2. Besides, GdL1 experiences a much faster dissociation following the acid-catalyzed mechanism than GdL2. On the contrary, GdL1 exhibits a lower exchange rate of the coordinated water molecule compared to GdL2. These very different properties are related to different strengths of the Gd-ligand bonds associated to steric effects, which hinder the coordination of a water molecule in GdL2 and the binding of acetate groups in GdL1. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rac1/WAVE2 and Cdc42/N-WASP Participation in Actin-Dependent Host Cell Invasion by Extracellular Amastigotes of Trypanosoma cruzi.

PubMed

Bonfim-Melo, Alexis; Ferreira, Éden R; Mortara, Renato A

2018-01-01

This study evaluated the participation of host cell Rho-family GTPases and their effector proteins in the actin-dependent invasion by Trypanosoma cruzi extracellular amastigotes (EAs). We observed that all proteins were recruited and colocalized with actin at EA invasion sites in live or fixed cells. EA internalization was inhibited in cells depleted in Rac1, N-WASP, and WAVE2. Time-lapse experiments with Rac1, N-WASP and WAVE2 depleted cells revealed that EA internalization kinetics is delayed even though no differences were observed in the proportion of EA-induced actin recruitment in these groups. Overexpression of constitutively active constructs of Rac1 and RhoA altered the morphology of actin recruitments to EA invasion sites. Additionally, EA internalization was increased in cells overexpressing CA-Rac1 but inhibited in cells overexpressing CA-RhoA. WT-Cdc42 expression increased EA internalization, but curiously, CA-Cdc42 inhibited it. Altogether, these results corroborate the hypothesis of EA internalization in non-phagocytic cells by a phagocytosis-like mechanism and present Rac1 as the key Rho-family GTPase in this process.

Rac1/WAVE2 and Cdc42/N-WASP Participation in Actin-Dependent Host Cell Invasion by Extracellular Amastigotes of Trypanosoma cruzi

PubMed Central

Bonfim-Melo, Alexis; Ferreira, Éden R.; Mortara, Renato A.

2018-01-01

This study evaluated the participation of host cell Rho-family GTPases and their effector proteins in the actin-dependent invasion by Trypanosoma cruzi extracellular amastigotes (EAs). We observed that all proteins were recruited and colocalized with actin at EA invasion sites in live or fixed cells. EA internalization was inhibited in cells depleted in Rac1, N-WASP, and WAVE2. Time-lapse experiments with Rac1, N-WASP and WAVE2 depleted cells revealed that EA internalization kinetics is delayed even though no differences were observed in the proportion of EA-induced actin recruitment in these groups. Overexpression of constitutively active constructs of Rac1 and RhoA altered the morphology of actin recruitments to EA invasion sites. Additionally, EA internalization was increased in cells overexpressing CA-Rac1 but inhibited in cells overexpressing CA-RhoA. WT-Cdc42 expression increased EA internalization, but curiously, CA-Cdc42 inhibited it. Altogether, these results corroborate the hypothesis of EA internalization in non-phagocytic cells by a phagocytosis-like mechanism and present Rac1 as the key Rho-family GTPase in this process. PMID:29541069

Structural basis for regulation of human calcium-sensing receptor by magnesium ions and an unexpected tryptophan derivative co-agonist.

PubMed

Zhang, Chen; Zhang, Tuo; Zou, Juan; Miller, Cassandra Lynn; Gorkhali, Rakshya; Yang, Jeong-Yeh; Schilmiller, Anthony; Wang, Shuo; Huang, Kenneth; Brown, Edward M; Moremen, Kelley W; Hu, Jian; Yang, Jenny J

2016-05-01

Ca(2+)-sensing receptors (CaSRs) modulate calcium and magnesium homeostasis and many (patho)physiological processes by responding to extracellular stimuli, including divalent cations and amino acids. We report the first crystal structure of the extracellular domain (ECD) of human CaSR bound with Mg(2+) and a tryptophan derivative ligand at 2.1 Å. The structure reveals key determinants for cooperative activation by metal ions and aromatic amino acids. The unexpected tryptophan derivative was bound in the hinge region between two globular ECD subdomains, and represents a novel high-affinity co-agonist of CaSR. The dissection of structure-function relations by mutagenesis, biochemical, and functional studies provides insights into the molecular basis of human diseases arising from CaSR mutations. The data also provide a novel paradigm for understanding the mechanism of CaSR-mediated signaling that is likely shared by the other family C GPCR [G protein (heterotrimeric guanine nucleotide-binding protein)-coupled receptor] members and can facilitate the development of novel CaSR-based therapeutics.

Peroxidase Release Induced by Ozone in Sedum album Leaves

PubMed Central

Castillo, Federico J.; Penel, Claude; Greppin, Hubert

1984-01-01

The effect of ozone was studied on the peroxidase activity from various compartments of Sedum album leaves (epidermis, intercellular fluid, residual cell material, and total cell material). The greatest increase following a 2-hour ozone exposure (0.4 microliters O3 per liter) was observed in extracellular peroxidases. Most of the main bands of peroxidase activity separated by isoelectric focusing exhibited an increase upon exposure to ozone. Incubation experiments with isolated peeled or unpeeled leaves showed that leaves from ozone-treated plants release much more peroxidases in the medium than untreated leaves. The withdrawal of Ca2+ ions reduced the level of extracellular peroxidase activity either in whole plants or in incubation experiments. This reduction and the activation obtained after addition of Ca2+ resulted from a direct requirement of Ca2+ by the enzyme and from an effect of Ca2+ on peroxidase secretion. The ionophore A23187 promoted an increase of extracellular peroxidase activity only in untreated plants. The release of peroxidases by untreated and ozone-treated leaves is considerably lowered by metabolic inhibitors (3-(3,4-dichlorophenyl)-1,1-dimethylurea and sodium azide) and by puromycin. Images Fig. 1 PMID:16663520

Preparation of high magneto-optical performance and crystalline quality Ce1Gd2Fe5-xGaxO12 films on CLNGG substrate crystal

NASA Astrophysics Data System (ADS)

Fu, Qiu-ping; Zheng, Ze-yuan; Lin, Nan-xi; Liu, Xiao-feng; Hong, Can-huang; Hu, Xiao-lin; Zhuang, Nai-feng; Chen, Jian-zhong

2016-11-01

Thin films of Ce1Gd2Fe5-xGaxO12 (Ce,Ga:GIG) were prepared on Gd3Ga5O12 (GGG) and Ca2.90Li0.30Nb1.93Ga2.76O12 (CLNGG) substrates by using radio frequency magnetron sputtering technique. The phase, grain orientation, surface morphology, transmittance, magnetism and magnetic circular dichroism (MCD) properties of films were analyzed. And the effects of lattice mismatch and non-magnetic Ga3+-doping were discussed. The results show that the films with higher crystallized quality and lower stress can be obtained by growing on CLNGG than on GGG. Moreover, the coercive force, magnetization, magneto-optical effect intensity and orientation of film can be effectively regulated by adjusting Ga3+-doped concentration.

A new ex vivo method to evaluate the performance of candidate MRI contrast agents: a proof-of-concept study.

PubMed

Candiota, Ana Paula; Acosta, Milena; Simões, Rui Vasco; Delgado-Goñi, Teresa; Lope-Piedrafita, Silvia; Irure, Ainhoa; Marradi, Marco; Bomati-Miguel, Oscar; Miguel-Sancho, Nuria; Abasolo, Ibane; Schwartz, Simó; Santamaria, Jesús; Penadés, Soledad; Arús, Carles

2014-04-05

Magnetic resonance imaging (MRI) plays an important role in tumor detection/diagnosis. The use of exogenous contrast agents (CAs) helps to improve the discrimination between lesion and neighbouring tissue, but most of the currently available CAs are non-specific. Assessing the performance of new, selective CAs requires exhaustive assays and large amounts of material. Accordingly, in a preliminary screening of new CAs, it is important to choose candidate compounds with good potential for in vivo efficiency. This screening method should reproduce as close as possible the in vivo environment. In this sense, a fast and reliable method to select the best candidate CAs for in vivo studies would minimize time and investment cost, and would benefit the development of better CAs. The post-mortem ex vivo relative contrast enhancement (RCE) was evaluated as a method to screen different types of CAs, including paramagnetic and superparamagnetic agents. In detail, sugar/gadolinium-loaded gold nanoparticles (Gd-GNPs) and iron nanoparticles (SPIONs) were tested. Our results indicate that the post-mortem ex vivo RCE of evaluated CAs, did not correlate well with their respective in vitro relaxivities. The results obtained with different Gd-GNPs suggest that the linker length of the sugar conjugate could modulate the interactions with cellular receptors and therefore the relaxivity value. A paramagnetic CA (GNP (E_2)), which performed best among a series of Gd-GNPs, was evaluated both ex vivo and in vivo. The ex vivo RCE was slightly worst than gadoterate meglumine (201.9 ± 9.3% versus 237 ± 14%, respectively), while the in vivo RCE, measured at the time-to-maximum enhancement for both compounds, pointed to GNP E_2 being a better CA in vivo than gadoterate meglumine. This is suggested to be related to the nanoparticule characteristics of the evaluated GNP. We have developed a simple, cost-effective relatively high-throughput method for selecting CAs for in vivo experiments. This method requires approximately 800 times less quantity of material than the amount used for in vivo administrations.

A new ex vivo method to evaluate the performance of candidate MRI contrast agents: a proof-of-concept study

PubMed Central

2014-01-01

Background Magnetic resonance imaging (MRI) plays an important role in tumor detection/diagnosis. The use of exogenous contrast agents (CAs) helps to improve the discrimination between lesion and neighbouring tissue, but most of the currently available CAs are non-specific. Assessing the performance of new, selective CAs requires exhaustive assays and large amounts of material. Accordingly, in a preliminary screening of new CAs, it is important to choose candidate compounds with good potential for in vivo efficiency. This screening method should reproduce as close as possible the in vivo environment. In this sense, a fast and reliable method to select the best candidate CAs for in vivo studies would minimize time and investment cost, and would benefit the development of better CAs. Results The post-mortem ex vivo relative contrast enhancement (RCE) was evaluated as a method to screen different types of CAs, including paramagnetic and superparamagnetic agents. In detail, sugar/gadolinium-loaded gold nanoparticles (Gd-GNPs) and iron nanoparticles (SPIONs) were tested. Our results indicate that the post-mortem ex vivo RCE of evaluated CAs, did not correlate well with their respective in vitro relaxivities. The results obtained with different Gd-GNPs suggest that the linker length of the sugar conjugate could modulate the interactions with cellular receptors and therefore the relaxivity value. A paramagnetic CA (GNP (E_2)), which performed best among a series of Gd-GNPs, was evaluated both ex vivo and in vivo. The ex vivo RCE was slightly worst than gadoterate meglumine (201.9 ± 9.3% versus 237 ± 14%, respectively), while the in vivo RCE, measured at the time-to-maximum enhancement for both compounds, pointed to GNP E_2 being a better CA in vivo than gadoterate meglumine. This is suggested to be related to the nanoparticule characteristics of the evaluated GNP. Conclusion We have developed a simple, cost-effective relatively high-throughput method for selecting CAs for in vivo experiments. This method requires approximately 800 times less quantity of material than the amount used for in vivo administrations. PMID:24708566

Effect of CaO2 addition on anaerobic digestion of waste activated sludge at different temperatures and the promotion of valuable carbon source production under ambient condition.

PubMed

Ping, Qian; Lu, Xiao; Zheng, Ming; Li, Yongmei

2018-06-06

The effect of calcium peroxide (CaO 2 ) addition on anaerobic digestion (AD) of waste activated sludge (WAS) at different temperatures (20 °C, 35 °C, and 55 °C) were investigated. The results show that CaO 2 addition had significant positive effect on short-chain fatty acids (SCFAs) production under ambient and mesophilic conditions. Polysaccharides and proteins embedded in extracellular polymeric substances (EPS) were effectively released from inner fraction to outer fraction, and non-biodegradable humic-like substances were decreased while easily biodegradable tryptophan-like proteins increased. These effects were most remarkable under ambient conditions. However, CaO 2 addition was unfavorable to thermophilic AD because of high free ammonia concentrations and the accumulation of humic-like substances. Temperature showed a stronger effect than CaO 2 on microbial community structure, but CaO 2 addition was more effective than temperature in enhancing hydrolytic and acidifying microorganisms. Predictive functional profiling indicated that microbial hydrolysis, metabolism and acidification were promoted by CaO 2 under ambient conditions. Copyright © 2018 Elsevier Ltd. All rights reserved.

In vivo characterization of a smart MRI agent that displays an inverse response to calcium concentration.

PubMed

Mamedov, Ilgar; Canals, Santiago; Henig, Jörg; Beyerlein, Michael; Murayama, Yusuke; Mayer, Hermann A; Logothetis, Nikos K; Angelovski, Goran

2010-12-15

Contrast agents for magnetic resonance imaging (MRI) that exhibit sensitivity toward specific ions or molecules represent a challenging but attractive direction of research. Here a Gd(3+) complex linked to an aminobis(methylenephosphonate) group for chelating Ca(2+) was synthesized and investigated. The longitudinal relaxivity (r(1)) of this complex decreases during the relaxometric titration with Ca(2+) from 5.76 to 3.57 mM(-1) s(-1) upon saturation. The r(1) is modulated by changes in the hydration number, which was confirmed by determination of the luminescence emission lifetimes of the analogous Eu(3+) complex. The initial in vivo characterization of this responsive contrast agent was performed by means of electrophysiology and MRI experiments. The investigated complex is fully biocompatible, having no observable effect on neuronal function after administration into the brain ventricles or parenchyma. Distribution studies demonstrated that the diffusivity of this agent is significantly lower compared with that of gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA).

Double perovskite Ca2GdNbO6:Mn4+ deep red phosphor: Potential application for warm W-LEDs

NASA Astrophysics Data System (ADS)

Lu, Zuizhi; Huang, Tianjiao; Deng, Ruopeng; Wang, Huan; Wen, Lingling; Huang, Meixin; Zhou, Liya; Yao, Chunying

2018-05-01

A novel Mn4+-doped Ca2GdNbO6 (CGN) phosphor was prepared by high-temperature solid-state reaction. The crystal structure was investigated by X-ray diffraction patterns and unit cell structure. Mn4+ replaced the location of Nb5+ in the CGN lattice, and the value of energy gap (Egap) decreased from 2.16 eV to 1.13 eV, indicating that Mn4+ ions play a great influence on the absorption of CGN hosts. The broad excitation band from 250 nm to 550 nm matches well with commercial near-UV light emitting diodes, and the emission peak centered at 680 nm is due to 2E→4A2g transition in Mn4+ ions. The CIE chromaticity coordinates (0.698, 0.303) of CGN:Mn4+ phosphor was close to standard red color coordinates (0.666, 0.333). These investigations demonstrate CGN:Mn4+ phosphor as an efficient red phosphor for potential applications.

CaO-MgO-Al 2O 3-SiO 2 (CMAS) corrosion of Gd 2Zr 2O 7 and Sm 2Zr 2O 7

DOE PAGES

Wang, Honglong; Bakal, Ahmet; Zhang, Xingxing; ...

2016-08-08

Ceramic thermal barrier coatings are applied to superalloys used in gas turbine engineering to increase the operating temperature and the energy conversion efficiency. However, dust consisting of CaO-MgO-Al 2O 3-SiO 2 (CMAS) from the air can be injected into the engines and corrode the thermal barrier coatings. Lanthanide zirconates are promising materials in thermal barrier coatings due to their low thermal conductivities, good phase stability and good corrosion resistance. However, the corrosion resistance mechanism of CMAS on lanthanide zirconates is still not clearly understood. In this work, the corrosion mechanism of Gd 2Zr 2O 7 and Sm 2Zr 2O 7more » in CMAS is studied. Here, the results show that the CMAS can easily react with lanthanide zirconate thermal barrier coatings to form a dense layer, which can resist further corrosion« less

Cannabidiol induces intracellular calcium elevation and cytotoxicity in oligodendrocytes.

PubMed

Mato, Susana; Victoria Sánchez-Gómez, María; Matute, Carlos

2010-11-01

Heavy marijuana use has been linked to white matter histological alterations. However, the impact of cannabis constituents on oligodendroglial pathophysiology remains poorly understood. Here, we investigated the in vitro effects of cannabidiol, the main nonpsychoactive marijuana component, on oligodendrocytes. Exposure to cannabidiol induced an intracellular Ca(2+) rise in optic nerve oligodendrocytes that was not primarily mediated by entry from the extracellular space, nor by interactions with ryanodine or IP(3) receptors. Application of the mitochondrial protonophore carbonylcyanide-p-trifluoromethoxyphenylhydrazone (FCCP; 1 μM) completely prevented subsequent cannabidiol-induced Ca(2+) responses. Conversely, the increase in cytosolic Ca(2+) levels elicited by FCCP was reduced after previous exposure to cannabidiol, further suggesting that the mitochondria acts as the source of cannabidiol-evoked Ca(2+) rise in oligodendrocytes. n addition, brief exposure to cannabidiol (100 nM-10 μM) led to a concentration-dependent decrease of oligodendroglial viability that was not prevented by antagonists of CB(1), CB(2), vanilloid, A(2A) or PPARγ receptors, but was instead reduced in the absence of extracellular Ca(2+). The oligodendrotoxic effect of cannabidiol was partially blocked by inhibitors of caspase-3, -8 and -9, PARP-1 and calpains, suggesting the activation of caspase-dependent and -independent death pathways. Cannabidiol also elicited a concentration-dependent alteration of mitochondrial membrane potential, and an increase in reactive oxygen species (ROS) that was reduced in the absence of extracellular Ca(2+). Finally, cannabidiol-induced cytotoxicity was partially prevented by the ROS scavenger trolox. Together, these results suggest that cannabidiol causes intracellular Ca(2+) dysregulation which can lead to oligodendrocytes demise.

Measurement of the optical and the physical properties of a liquid scintillator containing water at different times and under different environmental conditions

NASA Astrophysics Data System (ADS)

Kim, Seung Chan; Joo, Kyung Kwang; Kim, Ba Ro; Shin, Chang Dong; So, Sun Heang; Yeo, In Sung

2014-10-01

In this paper, we describe the optical and the physical properties of a liquid scintillator (LS) containing water with long-term stability. Gadolinium (Gd) is loaded into the liquid scintillator to increase the intensity of the neutron capture signal. If a successful neutrino experiment is to be performed, the Gd-loaded liquid scintillator (GdLS) must be stable over the entire duration of the experiment. If water is contained inside the GdLS, the optical and the physical parameters of the GdLS may change. We, therefore, briefly describe several characteristics of GdLS samples with various water contents under different environmental conditions. Measurements of the water content, Gd concentration, transmittance, and light yield (LY) were performed over 600 days.

Factors associated with desistence and persistence of childhood gender dysphoria: a quantitative follow-up study.

PubMed

Steensma, Thomas D; McGuire, Jenifer K; Kreukels, Baudewijntje P C; Beekman, Anneke J; Cohen-Kettenis, Peggy T

2013-06-01

To examine the factors associated with the persistence of childhood gender dysphoria (GD), and to assess the feelings of GD, body image, and sexual orientation in adolescence. The sample consisted of 127 adolescents (79 boys, 48 girls), who were referred for GD in childhood (<12 years of age) and followed up in adolescence. We examined childhood differences among persisters and desisters in demographics, psychological functioning, quality of peer relations and childhood GD, and adolescent reports of GD, body image, and sexual orientation. We examined contributions of childhood factors on the probability of persistence of GD into adolescence. We found a link between the intensity of GD in childhood and persistence of GD, as well as a higher probability of persistence among natal girls. Psychological functioning and the quality of peer relations did not predict the persistence of childhood GD. Formerly nonsignificant (age at childhood assessment) and unstudied factors (a cognitive and/or affective cross-gender identification and a social role transition) were associated with the persistence of childhood GD, and varied among natal boys and girls. Intensity of early GD appears to be an important predictor of persistence of GD. Clinical recommendations for the support of children with GD may need to be developed independently for natal boys and for girls, as the presentation of boys and girls with GD is different, and different factors are predictive for the persistence of GD. Copyright © 2013 American Academy of Child and Adolescent Psychiatry. Published by Elsevier Inc. All rights reserved.

CHEMICAL ABUNDANCES IN THE EXTERNALLY POLLUTED WHITE DWARF GD 40: EVIDENCE OF A ROCKY EXTRASOLAR MINOR PLANET

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

Klein, B.; Jura, M.; Zuckerman, B.

2010-02-01

We present Keck/High Resolution Echelle Spectrometer data with model atmosphere analysis of the helium-dominated polluted white dwarf GD 40, in which we measure atmospheric abundances relative to helium of nine elements: H, O, Mg, Si, Ca, Ti, Cr, Mn, and Fe. Apart from hydrogen, whose association with the other contaminants is uncertain, this material most likely accreted from GD 40's circumstellar dust disk whose existence is demonstrated by excess infrared emission. The data are best explained by accretion of rocky planetary material, in which heavy elements are largely contained within oxides, derived from a tidally disrupted minor planet at leastmore » the mass of Juno, and probably as massive as Vesta. The relatively low hydrogen abundance sets an upper limit of 10% water by mass in the inferred parent body, and the relatively high abundances of refractory elements, Ca and Ti, may indicate high-temperature processing. While the overall constitution of the parent body is similar to the bulk Earth being over 85% by mass composed of oxygen, magnesium, silicon, and iron, we find n(Si)/n(Mg) = 0.30 +- 0.11, significantly smaller than the ratio near unity for the bulk Earth, chondrites, the Sun, and nearby stars. This result suggests that differentiation occurred within the parent body.« less

Spectral features of the Stokes part of supercontinuum generated by femtosecond light pulses in selected oxide crystals: A comparative study

NASA Astrophysics Data System (ADS)

Macalik, B.; Kowalski, R. M.; Ryba-Romanowski, W.

2018-04-01

The peculiarities of the Stokes part of supercontinuum (SC) generated by femtosecond light pulses at wavelength 800 nm in single crystals of Gd2SiO5(GSO), Ca4GdO(BO3)3(GCOB), Gd3Ga5O12(GGG), LiTaO3 (LTO) and LuVO4 (LVO) were investigated. Spectral bandwidth and intensity of SC were measured as a function of energy of incident 100 fs pulses employing a grating spectrograph coupled with an InGaAs detector and spatial characteristics of the beam inside crystal samples were monitored perpendicularly to the direction of propagation and recorded using an optical microscope coupled with a camera. It was found that spectral widths of the Stokes part of SC increase markedly with increasing energy of incident pulses for all crystals under study. For fixed focusing conditions the spectral widths of generated SC in GSO, GCOB and GGG wide band-gap crystals are relatively large with cut-off wavelengths close to 1500 nm. Bandwidths of SC generated in LVO and LTO crystals, characterized by band-gaps Eg inferior to three times incident photon energy, are markedly smaller with cut-off wavelengths of 1300 nm and 1150 nm, respectively. Increase of incident pulse energy affects SC spectra giving rise to plateau-like regions stretching to ca 1000 nm.

Coxsackievirus protein 2B modifies endoplasmic reticulum membrane and plasma membrane permeability and facilitates virus release.

PubMed Central

van Kuppeveld, F J; Hoenderop, J G; Smeets, R L; Willems, P H; Dijkman, H B; Galama, J M; Melchers, W J

1997-01-01

Digital-imaging microscopy was performed to study the effect of Coxsackie B3 virus infection on the cytosolic free Ca2+ concentration and the Ca2+ content of the endoplasmic reticulum (ER). During the course of infection a gradual increase in the cytosolic free Ca2+ concentration was observed, due to the influx of extracellular Ca2+. The Ca2+ content of the ER decreased in time with kinetics inversely proportional to those of viral protein synthesis. Individual expression of protein 2B was sufficient to induce the influx of extracellular Ca2+ and to release Ca2+ from ER stores. Analysis of mutant 2B proteins showed that both a cationic amphipathic alpha-helix and a second hydrophobic domain in 2B were required for these activities. Consistent with a presumed ability of protein 2B to increase membrane permeability, viruses carrying a mutant 2B protein exhibited a defect in virus release. We propose that 2B gradually enhances membrane permeability, thereby disrupting the intracellular Ca2+ homeostasis and ultimately causing the membrane lesions that allow release of virus progeny. PMID:9218794

Contribution of ultra-processed foods in the diet of adults from the French NutriNet-Santé study.

PubMed

Julia, Chantal; Martinez, Lucien; Allès, Benjamin; Touvier, Mathilde; Hercberg, Serge; Méjean, Caroline; Kesse-Guyot, Emmanuelle

2018-01-01

Concerns have been raised about the potential health impact of ultra-processed foods (UPF) in the diet. Our objective was to investigate the contribution of UPF in the diet in a large French population and its association with sociodemographic factors and dietary patterns. Cross-sectional analysis of dietary data from 74 470 participants in the web-based NutriNet-Santé cohort. UPF were identified in repeated 24 h records and the proportion (in weight) of UPF in the total diet (UPFp) was computed for each participant. Associations of sociodemographic characteristics and UPFp in quartiles were assessed using multivariate multinomial logistic regression. Food group consumption and nutrient intakes across quartiles of UPFp were estimated using linear regression adjusted for sociodemographic factors and energy intake. France. UPF contributed 18·4 % of the foods consumed in weight and 35·9 % of total energy intake. Higher UPFp consumption was independently associated with male gender, younger age, lower education, smoking, and overweight and obesity (all P<0·0001). Participants in the highest UPFp quartile consumed lower amounts of fruit and vegetables (difference between quartile 4 and quartile 1 of UPFp, Δ=-180·3 g/d) and higher amounts of sweet products (Δ=68·5 g/d) and soft drinks (Δ=98·6 g/d; all P<0·0001). They had higher intakes of energy (Δ=610 kJ/d (145·7 kcal/d)) and added sugar (Δ=17·1 g/d), and lower intakes of fibre (Δ=-4·04 g/d), β-carotene (Δ=-1019·6 μg/d) and Ca (Δ=-87·8 mg/d; all P<0·0001). UPF represent an important part of the diet in adults from the French general population and are associated with unbalanced nutritional intakes.

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

PubMed

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

1996-05-01

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

Gambling Disorder and Minority Populations: Prevalence and Risk Factors.

PubMed

Okuda, Mayumi; Liu, Weiwei; Cisewski, Jodi A; Segura, Luis; Storr, Carla L; Martins, Silvia S

2016-09-01

Previous studies demonstrate disparities in health and health services including gambling disorders (GD) among ethnic and racial minority groups. In this review, we summarize studies examining the prevalence of GD across different ethnic and racial minorities. We describe the sociodemographic subgroup variations at heightened risk for GD and factors associated with GD in racial and ethnic minority groups including gambling availability, comorbid substance use, psychiatric conditions, stress, acculturation, and differences in cultural values and cognitions. We found that research of GD among minority groups is scant, and the prevalence of GD among these groups is at a magnitude of concern. Racial and ethnic minority status in it of itself is not a risk factor for GD but may be a proxy for underlying potential risk factors. The need for prevention and treatment programs for different cultural group remains unmet.

Gadolinium-loaded chitosan nanoparticles for neutron-capture therapy: Influence of micrometric properties of the nanoparticles on tumor-killing effect.

PubMed

Ichikawa, Hideki; Uneme, Takeshi; Andoh, Tooru; Arita, Yuya; Fujimoto, Takuya; Suzuki, Minoru; Sakurai, Yoshinori; Shinto, Hiroyuki; Fukasawa, Tomonori; Fujii, Fumihiko; Fukumori, Yoshinobu

2014-06-01

As a nanoparticulate device for controlled delivery of Gd in NCT, the authors have developed gadolinium-loaded chitosan nanoparticles (Gd-nanoCPs). In the present study, influence of micrometric properties such as particle size, particle-surface charge and Gd content of Gd-nanoCPs on tumor-killing effect by Gd-NCT was investigated with Gd-nanoCPs. Two types of Gd-nanoCPs with different mean particle size, zeta potential and Gd-content (Gd-nanoCP-400; 391nm, 28mV, 9wt% and Gd-nanoCP-200; 214nm, 19mV, 24wt%) could be prepared by using chitosans with different molecular weights. Gd-nanoCPs incorporating 1.2mg of natural Gd were injected intratumorally once or twice to mice subcutaneously-bearing B16F10 melanoma. Eight hours after the last administration, thermal neutron was irradiated to tumor region of the mice. Remarkable tumor-growth was observed in both hot and cold control groups. In contrast, Gd-NCT groups showed significant tumor-growth suppression effect, though their efficacy was found to depend on the micrometric properties of Gd-nanoCPs. In particular, the Gd-nanoCP-200 exhibited stronger tumor-killing effect than the Gd-nanoCP-400 at the same Gd dose and it was still similar to Gd-nanoCP-400 in tumor-growth suppressing effect even at the half of Gd dose of Gd-nanoCP-400. This significance in tumor-killing effect would be ascribed from a higher Gd retention in the tumor tissue and an improved distribution of Gd with intratumorally administered Gd-nanoCP-200. Indeed, the Gd concentration in tumor tissue at the time corresponding to the onset of thermal neutron irradiation was determined to be significantly higher in Gd-nanoCP-200, compared with Gd-nanoCP-400. These results demonstrated that appropriate modification of Gd-nanoCPs in micrometric properties would be an effective way to improve the retention of Gd in the tumor tissue after intratumoral injection, leading to the enhanced tumor-killing effect in Gd-NCT. Copyright © 2013 Elsevier Ltd. All rights reserved.

Cameleon calcium indicator reports cytoplasmic calcium dynamics in Arabidopsis guard cells

NASA Technical Reports Server (NTRS)

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

1999-01-01

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

Measuring hepatic functional reserve using low temporal resolution Gd-EOB-DTPA dynamic contrast-enhanced MRI: a preliminary study comparing galactosyl human serum albumin scintigraphy with indocyanine green retention.

PubMed

Saito, Kazuhiro; Ledsam, Joseph; Sourbron, Steven; Hashimoto, Tsuyoshi; Araki, Yoichi; Akata, Soichi; Tokuuye, Koichi

2014-01-01

To investigate if tracer kinetic modelling of low temporal resolution dynamic contrast-enhanced (DCE) MRI with Gd-EOB-DTPA could replace technetium-99 m galactosyl human serum albumin (GSA) single positron emission computed tomography (SPECT) and indocyanine green (ICG) retention for the measurement of liver functional reserve. Twenty eight patients awaiting liver resection for various cancers were included in this retrospective study that was approved by the institutional review board. The Gd-EOB-DTPA MRI sequence acquired five images: unenhanced, double arterial phase, portal phase, and 4 min after injection. Intracellular contrast uptake rate (UR) and extracellular volume (Ve) were calculated from DCE-MRI, along with the ratio of GSA radioactivity of liver to heart-plus-liver and per cent of cumulative uptake from 15-16 min (LHL15 and LU15, respectively) from GSA-scintigraphy. ICG retention at 15 min, Child-Pugh cirrhosis score (CPS) and postoperative Inuyama fibrosis criteria were also recorded. Statistical analysis was with Spearman rank correlation analysis. Comparing MRI parameters with the reference methods, significant correlations were obtained for UR and LHL15, LU15, ICG15 (all 0.4-0.6, P < 0.05); UR and CPS (-0.64, P < 0.001); Ve and Inuyama (0.44, P < 0.05). Measures of liver function obtained by routine Gd-EOB-DTPA DCE-MRI with tracer kinetic modelling may provide a suitable method for the evaluation of liver functional reserve. • Magnetic resonance imaging (MRI) provides new methods of measuring hepatic functional reserve. • DCE-MRI with Gd-EOB-DTPA offers the possibility of replacing scintigraphy. • The analysis method can be used for preoperative liver function evaluation.

In vitro study of novel gadolinium-loaded liposomes guided by GBI-10 aptamer for promising tumor targeting and tumor diagnosis by magnetic resonance imaging.

PubMed

Gu, Meng-Jie; Li, Kun-Feng; Zhang, Lan-Xin; Wang, Huan; Liu, Li-Si; Zheng, Zhuo-Zhao; Han, Nan-Yin; Yang, Zhen-Jun; Fan, Tian-Yuan

2015-01-01

Novel gadolinium-loaded liposomes guided by GBI-10 aptamer were developed and evaluated in vitro to enhance magnetic resonance imaging (MRI) diagnosis of tumor. Nontargeted gadolinium-loaded liposomes were achieved by incorporating amphipathic material, Gd (III) [N,N-bis-stearylamidomethyl-N'-amidomethyl] diethylenetriamine tetraacetic acid, into the liposome membrane using lipid film hydration method. GBI-10, as the targeting ligand, was then conjugated onto the liposome surface to get GBI-10-targeted gadolinium-loaded liposomes (GTLs). Both nontargeted gadolinium-loaded liposomes and GTLs displayed good dispersion stability, optimal size, and zeta potential for tumor targeting, as well as favorable imaging properties with enhanced relaxivity compared with a commercial MRI contrast agent (CA), gadopentetate dimeglumine. The use of GBI-10 aptamer in this liposomal system was intended to result in increased accumulation of gadolinium at the periphery of C6 glioma cells, where the targeting extracellular matrix protein tenascin-C is overexpressed. Increased cellular binding of GTLs to C6 cells was confirmed by confocal microscopy, flow cytometry, and MRI, demonstrating the promise of this novel delivery system as a carrier of MRI contrast agent for the diagnosis of tumor. These studies provide a new strategy furthering the development of nanomedicine for both diagnosis and therapy of tumor.

Extracellular cyclic ADP-ribose potentiates ACh-induced contraction in bovine tracheal smooth muscle.

PubMed

Franco, L; Bruzzone, S; Song, P; Guida, L; Zocchi, E; Walseth, T F; Crimi, E; Usai, C; De Flora, A; Brusasco, V

2001-01-01

Cyclic ADP-ribose (cADPR), a universal calcium releaser, is generated from NAD(+) by an ADP-ribosyl cyclase and is degraded to ADP-ribose by a cADPR hydrolase. In mammals, both activities are expressed as ectoenzymes by the transmembrane glycoprotein CD38. CD38 was identified in both epithelial cells and smooth myocytes isolated from bovine trachea. Intact tracheal smooth myocytes (TSMs) responded to extracellular cADPR (100 microM) with an increase in intracellular calcium concentration ([Ca(2+)](i)) both at baseline and after acetylcholine (ACh) stimulation. The nonhydrolyzable analog 3-deaza-cADPR (10 nM) elicited the same effects as cADPR, whereas the cADPR antagonist 8-NH(2)-cADPR (10 microM) inhibited both basal and ACh-stimulated [Ca(2+)](i) levels. Extracellular cADPR or 3-deaza-cADPR caused a significant increase of ACh-induced contraction in tracheal smooth muscle strips, whereas 8-NH(2)-cADPR decreased it. Tracheal mucosa strips, by releasing NAD(+), enhanced [Ca(2+)](i) in isolated TSMs, and this increase was abrogated by either NAD(+)-ase or 8-NH(2)-cADPR. These data suggest the existence of a paracrine mechanism whereby mucosa-released extracellular NAD(+) plays a hormonelike function and cADPR behaves as second messenger regulating calcium-related contractility in TSMs.

Ca2+ permeability and Na+ conductance in cellular toxicity caused by hyperactive DEG/ENaC channels.

PubMed

Matthewman, Cristina; Miller-Fleming, Tyne W; Miller, David M; Bianchi, Laura

2016-12-01

Hyperactivated DEG/ENaC channels cause neuronal death mediated by intracellular Ca 2+ overload. Mammalian ASIC1a channels and MEC-4(d) neurotoxic channels in Caenorhabditis elegans both conduct Na + and Ca 2+ , raising the possibility that direct Ca 2+ influx through these channels contributes to intracellular Ca 2+ overload. However, we showed that the homologous C. elegans DEG/ENaC channel UNC-8(d) is not Ca 2+ permeable, yet it is neurotoxic, suggesting that Na + influx is sufficient to induce cell death. Interestingly, UNC-8(d) shows small currents due to extracellular Ca 2+ block in the Xenopus oocyte expression system. Thus, MEC-4(d) and UNC-8(d) differ both in current amplitude and Ca 2+ permeability. Given that these two channels show a striking difference in toxicity, we wondered how Na + conductance vs. Ca 2+ permeability contributes to cell death. To address this question, we built an UNC-8/MEC-4 chimeric channel that retains the calcium permeability of MEC-4 and characterized its properties in Xenopus oocytes. Our data support the hypothesis that for Ca 2+ -permeable DEG/ENaC channels, both Ca 2+ permeability and Na + conductance contribute to toxicity. However, for Ca 2+ -impermeable DEG/ENaCs (e.g., UNC-8), our evidence shows that constitutive Na + conductance is sufficient to induce toxicity, and that this effect is enhanced as current amplitude increases. Our work further refines the contribution of different channel properties to cellular toxicity induced by hyperactive DEG/ENaC channels. Copyright © 2016 the American Physiological Society.

Ca2+ permeability and Na+ conductance in cellular toxicity caused by hyperactive DEG/ENaC channels

PubMed Central

Matthewman, Cristina; Miller-Fleming, Tyne W.; Miller, David M.

2016-01-01

Hyperactivated DEG/ENaC channels cause neuronal death mediated by intracellular Ca2+ overload. Mammalian ASIC1a channels and MEC-4(d) neurotoxic channels in Caenorhabditis elegans both conduct Na+ and Ca2+, raising the possibility that direct Ca2+ influx through these channels contributes to intracellular Ca2+ overload. However, we showed that the homologous C. elegans DEG/ENaC channel UNC-8(d) is not Ca2+ permeable, yet it is neurotoxic, suggesting that Na+ influx is sufficient to induce cell death. Interestingly, UNC-8(d) shows small currents due to extracellular Ca2+ block in the Xenopus oocyte expression system. Thus, MEC-4(d) and UNC-8(d) differ both in current amplitude and Ca2+ permeability. Given that these two channels show a striking difference in toxicity, we wondered how Na+ conductance vs. Ca2+ permeability contributes to cell death. To address this question, we built an UNC-8/MEC-4 chimeric channel that retains the calcium permeability of MEC-4 and characterized its properties in Xenopus oocytes. Our data support the hypothesis that for Ca2+-permeable DEG/ENaC channels, both Ca2+ permeability and Na+ conductance contribute to toxicity. However, for Ca2+-impermeable DEG/ENaCs (e.g., UNC-8), our evidence shows that constitutive Na+ conductance is sufficient to induce toxicity, and that this effect is enhanced as current amplitude increases. Our work further refines the contribution of different channel properties to cellular toxicity induced by hyperactive DEG/ENaC channels. PMID:27760755

Increases in extracellular zinc in the amygdala in acquisition and recall of fear experience and their roles in response to fear.

PubMed

Takeda, A; Tamano, H; Imano, S; Oku, N

2010-07-14

The amygdala is enriched with histochemically reactive zinc, which is dynamically coupled with neuronal activity and co-released with glutamate. The dynamics of the zinc in the amygdala was analyzed in rats, which were subjected to inescapable stress, to understand the role of the zinc in emotional behavior. In the communication box, two rats were subjected to foot shock stress and anxiety stress experiencing emotional responses of foot-shocked rat under amygdalar perfusion. Extracellular zinc was increased by foot shock stress, while decreased by anxiety stress, suggesting that the differential changes in extracellular zinc are associated with emotional behavior. In rats conditioned with foot shock, furthermore, extracellular zinc was increased again in the recall of fear (foot shock) in the same box without foot shock. When this recall was performed under perfusion with CaEDTA, a membrane-impermeable zinc chelator, to examine the role of the increase in extracellular zinc, the time of freezing behavior was more increased, suggesting that zinc released in the lateral amygdala during the recall of fear participates in freezing behavior. To examine the role of the increase in extracellular zinc during fear conditioning, fear conditioning was also performed under perfusion with CaEDTA. The time of freezing behavior was more increased in the contextual recall, suggesting that zinc released in the lateral nucleus during fear conditioning also participates in freezing behavior in the recall. In brain slice experiment, CaEDTA enhanced presynaptic activity (exocytosis) in the lateral nucleus after activation of the entorhinal cortex. The present paper demonstrates that zinc released in the lateral amygdala may participate in emotional behavior in response to fear. Copyright 2010 IBRO. Published by Elsevier Ltd. All rights reserved.

Similar cholesterol-lowering properties of rice bran oil, with varied gamma-oryzanol, in mildly hypercholesterolemic men.

PubMed

Berger, Alvin; Rein, Dietrich; Schäfer, Angela; Monnard, Irina; Gremaud, Gérard; Lambelet, Pierre; Bertoli, Constantin

2005-03-01

The cholesterol lowering properties of rice bran oil (RBO) containing differing amounts of non-saponifiable components have not been studied in humans, to our knowledge. To evaluate cholesterol lowering effects of RBO, with low and high amounts of gamma-oryzanol (ferulated plant sterols) in mildly hypercholesterolemic men. Mildly hypercholesterolemic men, 38-64 y, starting cholesterol 4.9-8.4 mmol/l (n = 30), consumed 50 g/d peanut oil (PNO) in vehicles for 2 wks during a run-in period, then, without wash-out, were randomly equilibrated (based on initial level of cholesterol) into two groups to consume 50 g/d RBO low (0.05 g/d) or high (0.8 g/d) gamma-oryzanol for 4 wks, in a randomized, controlled, parallel design study. Subjects were free-living and consumed habitual diets with some restrictions. Plasma concentrations of total, LDL-,HDL-cholesterol and triacylglycerol were measured at base line and after 2, 4, and 6 wks. The two RBO types were not significantly different with respect to effects on various cholesterol parameters, at 2 and 4 wks, including total cholesterol, LDL-, HDL- and LDL/HDL cholesterol ratio. Low and high gamma-oryzanolcontaining RBO feeding for 4 wks lowered total plasma cholesterol (6.3 %), LDL-C (10.5 %) and the LDL-C/HDL-C ratio (18.9 %). RBO supplementation at ca. 50% total fat intake improved lipoprotein pattern in mildly hypercholesterolemic men. Methylated sterols in gamma-oryzanol are thought to be largely ineffective at inhibiting dietary cholesterol absorption, but could enhance cholesterol-lowering ability of 4-desmethylsterols. Assuming all ferulated sterols become de-ferulated in the gut, low and high gamma-oryzanolcontaining RBOs provided intestinal loads of 453 and 740 mg/d free 4-desmethylsterols, respectively. This intestinal load of 453-740 mg/d of efficacious free plant sterol equivalents had identical effects on lipoproteins.

Theoretical considerations in measurement of time discrepancies between input and myocardial time-signal intensity curves in estimates of regional myocardial perfusion with first-pass contrast-enhanced MRI.

PubMed

Natsume, Takahiro; Ishida, Masaki; Kitagawa, Kakuya; Nagata, Motonori; Sakuma, Hajime; Ichihara, Takashi

2015-11-01

The purpose of this study was to develop a method to determine time discrepancies between input and myocardial time-signal intensity (TSI) curves for accurate estimation of myocardial perfusion with first-pass contrast-enhanced MRI. Estimation of myocardial perfusion with contrast-enhanced MRI using kinetic models requires faithful recording of contrast content in the blood and myocardium. Typically, the arterial input function (AIF) is obtained by setting a region of interest in the left ventricular cavity. However, there is a small delay between the AIF and the myocardial curves, and such time discrepancies can lead to errors in flow estimation using Patlak plot analysis. In this study, the time discrepancies between the arterial TSI curve and the myocardial tissue TSI curve were estimated based on the compartment model. In the early phase after the arrival of the contrast agent in the myocardium, the relationship between rate constant K1 and the concentrations of Gd-DTPA contrast agent in the myocardium and arterial blood (LV blood) can be described by the equation K1={dCmyo(tpeak)/dt}/Ca(tpeak), where Cmyo(t) and Ca(t) are the relative concentrations of Gd-DTPA contrast agent in the myocardium and in the LV blood, respectively, and tpeak is the time corresponding to the peak of Ca(t). In the ideal case, the time corresponding to the maximum upslope of Cmyo(t), tmax, is equal to tpeak. In practice, however, there is a small difference in the arrival times of the contrast agent into the LV and into the myocardium. This difference was estimated to correspond to the difference between tpeak and tmax. The magnitudes of such time discrepancies and the effectiveness of the correction for these time discrepancies were measured in 18 subjects who underwent myocardial perfusion MRI under rest and stress conditions. The effects of the time discrepancies could be corrected effectively in the myocardial perfusion estimates. Copyright © 2015 Elsevier Inc. All rights reserved.

The responses to manipulation of extracellular and intracellular calcium are altered in the streptozotocin-diabetic rat colon and ileum.

PubMed

Forrest, Abigail; Molleman, Areles; Parsons, Mike

2005-02-10

Studies were performed to see if alterations in Ca2+ homeostasis underlie the gastrointestinal motility complications seen in many diabetic patients. Experiments were performed on colonic and ileal tissues taken from streptozotocin-induced diabetic and control rats. Diabetes caused alterations in the responses of the tissues to Ca2+ manipulation but these differed between the colon and ileum. In the colon a small but not significant increase in contractile responses to CaCl2 was observed in diabetic tissues, whereas the responses of the ileum were depressed relative to those of the controls. In contrast, responses of the diabetic ileum to the Ca2+ channel agonist Bay K8644 were greater than those of the controls, whilst the agonist failed to contract the colon. Similarly, the Ca2+-ATPase inhibitors, thapsigargin and cyclopiazonic acid, produced contractions which were greater in diabetic ileal tissues. Thus, alterations in the responses of the diabetic gut to Ca2+ manipulation are complex, and also tissue-specific.

64Cu-DOTA as a surrogate positron analog of Gd-DOTA for cardiac fibrosis detection with PET: pharmacokinetic study in a rat model of chronic MI.

PubMed

Kim, Heejung; Lee, Sung-Jin; Davies-Venn, Cynthia; Kim, Jin Su; Yang, Bo Yeun; Yao, Zhengsheng; Kim, Insook; Paik, Chang H; Bluemke, David A

2016-02-01

The aim of this study was to investigate the pharmacokinetics of (64)Cu-DOTA (1,4,7,10-azacyclododecane-N,N',N'',N'''-tetraacetic acid), a positron surrogate analog of the late gadolinium (Gd)-enhancement cardiac magnetic resonance agent, Gd-DOTA, in a rat model of chronic myocardial infarction (MI) and its microdistribution in the cardiac fibrosis by autoradiography. DOTA was labeled with (64)Cu-acetate. CD rats (n=5) with MI by left anterior descending coronary artery ligation and normal rats (n=6) were injected intravenously with (64)Cu-DOTA (18.5 MBq, 0.02 mmol DOTA/kg). Dynamic PET imaging was performed for 60 min after injection. (18)F-Fluorodeoxyglucose ([(18)F]-FDG) PET imaging was performed to identify the viable myocardium. For the region of interest analysis, the (64)Cu-DOTA PET image was coregistered to the [(18)F]-FDG PET image. To validate the PET images, slices of heart samples from the base to the apex were analyzed using autoradiography and by histological staining with Masson's trichrome. (64)Cu-DOTA was rapidly taken up in the infarct area. The time-activity curves demonstrated that (64)Cu-DOTA concentrations in the blood, fibrotic tissue, and perfusion-rich organs peaked within a minute post injection; thereafter, it was rapidly washed out in parallel with blood clearance and excreted through the renal system. The blood clearance curve was biphasic, with a distribution half-life of less than 3 min and an elimination half-life of ∼21.8 min. The elimination half-life of (64)Cu-DOTA from the focal fibrotic tissue (∼22.4 min) and the remote myocardium (∼20.1 min) was similar to the blood elimination half-life. Consequently, the uptake ratios of focal fibrosis-to-blood and remote myocardium-to-blood remained stable for the time period between 10 and 60 min. The corresponding ratios obtained from images acquired from 30 to 60 min were 1.09 and 0.59, respectively, indicating that the concentration of (64)Cu-DOTA in the focal fibrosis was 1.85 (1.09/0.59) times greater than that in the remote myocardium. Thus, this finding indicates that the extracellular volume fraction was 1.85 times greater in the focal fibrosis than in the remote myocardium. The accumulation of (64)Cu-DOTA in fibrotic tissue was further supported by autoradiography and histology images. The autoradiography images of (64)Cu-DOTA in the fibrotic tissues were qualitatively superimposed over the histology images of the fibrotic tissues. The histology images of the infarct areas were characterized by a heterogeneous distribution of thin bands of fibrotic collagen, myocytes, and expanded extracellular space. (64)Cu-DOTA is a useful surrogate positron analog of Gd-DOTA, enabling quantitative measurement of the uptake values in fibrotic tissues by dynamic PET imaging and calculation of the extracellular volume fractions of the fibrotic tissues. At a microscopic level, the distribution of (64)Cu-DOTA is nonuniform, corresponding to the heterogeneous distribution of expanded extracellular space in the setting of MI.

Synchrotron radiation based STXM analysis and micro-XRF mapping of differential expression of extracellular thiol groups by Acidithiobacillus ferrooxidans grown on Fe(2+) and S(0).

PubMed

Xia, Jin-Lan; Liu, Hong-Chang; Nie, Zhen-Yuan; Peng, An-An; Zhen, Xiang-Jun; Yang, Yun; Zhang, Xiu-Li

2013-09-01

The differential expression of extracellular thiol groups by Acidithiobacillus ferrooxidans grown on substrates Fe(2+) and S(0) was investigated by using synchrotron radiation based scanning transmission X-ray microscopy (STXM) imaging and microbeam X-ray fluorescence (μ-XRF) mapping. The extracellular thiol groups (SH) were first alkylated by iodoacetic acid forming Protein-SCH2COOH and then the P-SCH2COOH was marked by calcium ions forming P-SCH2COOCa. The STXM imaging and μ-XRF mapping of SH were based on analysis of SCH2COO-bonded Ca(2+). The results indicated that the thiol group content of A. ferrooxidans grown on S(0) is 3.88 times to that on Fe(2+). Combined with selective labeling of SH by Ca(2+), the STXM imaging and μ-XRF mapping provided an in situ and rapid analysis of differential expression of extracellular thiol groups. © 2013.

Intercellular Ca2+ Waves: Mechanisms and Function

PubMed Central

Sanderson, Michael J.

2012-01-01

Intercellular calcium (Ca2+) waves (ICWs) represent the propagation of increases in intracellular Ca2+ through a syncytium of cells and appear to be a fundamental mechanism for coordinating multicellular responses. ICWs occur in a wide diversity of cells and have been extensively studied in vitro. More recent studies focus on ICWs in vivo. ICWs are triggered by a variety of stimuli and involve the release of Ca2+ from internal stores. The propagation of ICWs predominately involves cell communication with internal messengers moving via gap junctions or extracellular messengers mediating paracrine signaling. ICWs appear to be important in both normal physiology as well as pathophysiological processes in a variety of organs and tissues including brain, liver, retina, cochlea, and vascular tissue. We review here the mechanisms of initiation and propagation of ICWs, the key intra- and extracellular messengers (inositol 1,4,5-trisphosphate and ATP) mediating ICWs, and the proposed physiological functions of ICWs. PMID:22811430

Self-Reported Autism Spectrum Disorder Symptoms Among Adults Referred to a Gender Identity Clinic.

PubMed

Vermaat, Lieke E W; van der Miesen, Anna I R; de Vries, Annelou L C; Steensma, Thomas D; Popma, Arne; Cohen-Kettenis, Peggy T; Kreukels, Baudewijntje P C

The purpose of this study was to (1) investigate autism spectrum disorder (ASD) symptoms in a sample of adults referred for gender dysphoria (GD) compared to typically developing (TD) populations, (2) see whether males assigned at birth with GD (MaB GD s) and females assigned at birth with GD (FaB GD s) differ in ASD symptom levels, (3) study the role of sexual orientation, and (4) investigate ASD symptoms' correlation with GD symptoms. The Autism-Spectrum Quotient (AQ) was used to measure ASD symptoms, and the Utrecht Gender Dysphoria Scale (UGDS) was used to measure the intensity of GD. Mean AQ scores of adults referred for GD (n = 326; 191 MaB GD and 135 FaB GD ) were compared to three TD populations taken from the literature (n = 1316; 667 male and 644 female, 5 birth-assigned sex unknown). The mean AQ score in individuals referred for GD was similar to the TD samples. FaB GD s showed higher mean AQ scores than MaB GD s, and they had mean scores similar to TD individuals of the same experienced gender (TD males). After selecting individuals with an UGDS score indicative of GD, a positive association between ASD and GD symptoms was found. The co-occurrence of GD and ASD in adults may not be as prevalent as previously suggested. Attenuation of sex differences in ASD might explain FaB GD s' and MaB GD s' ASD symptoms' similarity to those of TD individuals of the same experienced gender. Intensity of ASD symptoms might be correlated with intensity of GD symptoms, warranting further studies to elaborate on their potential co-occurrence.

Target binding improves relaxivity in aptamer-gadolinium conjugates.

PubMed

Bernard, Elyse D; Beking, Michael A; Rajamanickam, Karunanithi; Tsai, Eve C; Derosa, Maria C

2012-12-01

MRI contrast agents (CA) have been heavily used over the past several decades to enhance the diagnostic value of the obtained images. From a design perspective, two avenues to improve the efficacy of contrast agents are readily evident: optimization of magnetic properties of the CA, and optimization of the pharmacokinetics and distribution of the CA in the patient. Contrast agents consisting of DNA aptamer-gadolinium(III) conjugates provide a single system in which these factors can be addressed simultaneously. In this proof-of-concept study, the 15mer thrombin aptamer was conjugated to diethylenetriaminepentaacetic (DTPA) dianhydride to form a monoamide derivative of the linear open-chain chelate present in the commonly used contrast agent Magnevist(®). The stability of the conjugated DNA aptamer-DTPA-Gd(III) chelate in a transmetallation study using Zn(II) was found to be similar to that reported for DTPA-Gd(III). Relaxivity enhancements of 35 ± 4 and 20 ± 1 % were observed in the presence of thrombin compared to a control protein at fields of 9.4 and 1.5 T, respectively. The inclusion of spacers between the aptamer and the DTPA to eliminate possible steric effects was also investigated but not found to improve the relaxation enhancement achieved in comparison to the unaltered aptamer conjugate.

Influences of alkaline earth metal substitution on the crystal structure and physical properties of magnetic RuSr1.9A0.1GdCu2O8 (A = Ca, Sr, and Ba) superconductors.

PubMed

Hur, Su Gil; Park, Dae Hoon; Hwang, Seong-Ju; Kim, Seung Joo; Lee, J H; Lee, Sang Young

2005-11-24

We have investigated the effect of alkaline earth metal substitution on the crystal structure and physical properties of magnetic superconductors RuSr(1.9)A(0.1)GdCu(2)O(8) (A = Ca, Sr, and Ba) in order to probe an interaction between the magnetic coupling of the RuO(2) layer and the superconductivity of the CuO(2) layer. X-ray diffraction and X-ray absorption spectroscopic analyses demonstrate that the isovalent substitution of Sr ions with Ca or Ba ions makes it possible to tune the interlayer distance between the CuO(2) and the RuO(2) layers. From the measurements of electrical resistance and magnetic susceptibility, it was found that, in contrast to negligible change of magnetization, both of the alkaline earth metal substitutions lead to a notable depression of zero-resistance temperature T(c) (DeltaT(c) approximately 17-19 K). On the basis of the absence of a systematic correlation between the T(c) and the interlayer distance/magnetization, we have concluded that the internal magnetic field of the RuO(2) layer has insignificant influence on the superconducting property of the CuO(2) layer in the ruthenocuprate.

In Vivo Perturbation of Membrane-Associated Calcium by Freeze-Thaw Stress in Onion Bulb Cells 1

PubMed Central

Arora, Rajeev; Palta, Jiwan P.

1988-01-01

Incipient freeze-thaw stress in onion bulb scale tissue is known to cause enhanced efflux of K+, along with small but significant loss of cellular Ca2+. During the post-thaw period, irreversibly injured cells undergo a cytological aberration, namely, `protoplasmic swelling.' This cellular symptom is thought to be caused by replacement of Ca2+ from membrane by extracellular K+ and subsequent perturbation of K+ transport properties of plasma membrane. In the present study, onion (Allium cepa L. cv Sweet Sandwich) bulbs were slowly frozen to either −8.5°C or −11.5°C and thawed over ice. Inner epidermal peels from bulb scales were treated with fluorescein diacetate for assessing viability. In these cells, membrane-associated calcium was determined using chlorotetracycline fluorescence microscopy combined with image analysis. Increased freezing stress and tissue infiltration (visual water-soaking) were paralleled by increased ion leakage. Freezing injury (−11.5°C; irreversible) caused a specific and substantial loss of membrane-associated Ca2+ compared to control. Loss of membrane-associated Ca2+ caused by moderate stress (−8.5°C; reversible) was much less relative to −11.5°C treatment. Ion efflux and Ca2+-chlorotetracycline fluorescence showed a negative relationship. Extracellular KCl treatment simulated freeze-thaw stress by causing a similar loss of membrane-associated calcium. This loss was dramatically reduced by presence of extracellular CaCl2. Our results suggest that the loss of membrane-associated Ca2+, in part, plays a role in initiation and progression of freezing injury. Images Fig. 1 Fig. 2 PMID:16666196

Calcium Signaling Regulates Trafficking of Familial Hypocalciuric Hypercalcemia (FHH) Mutants of the Calcium Sensing Receptor

PubMed Central

Grant, Michael P.; Stepanchick, Ann

2012-01-01

Calcium-sensing receptors (CaSRs) regulate systemic Ca2+ homeostasis. Loss-of-function mutations cause familial benign hypocalciuric hypercalcemia (FHH) or neonatal severe hyperparathyroidism (NSHPT). FHH/NSHPT mutations can reduce trafficking of CaSRs to the plasma membrane. CaSR signaling is potentiated by agonist-driven anterograde CaSR trafficking, leading to a new steady state level of plasma membrane CaSR, which is maintained, with minimal functional desensitization, as long as extracellular Ca2+ is elevated. This requirement for CaSR signaling to drive CaSR trafficking to the plasma membrane led us to reconsider the mechanism(s) contributing to dysregulated trafficking of FHH/NSHPT mutants. We simultaneously monitored dynamic changes in plasma membrane levels of CaSR and intracellular Ca2+, using a chimeric CaSR construct, which allowed explicit tracking of plasma membrane levels of mutant or wild-type CaSRs in the presence of nonchimeric partners. Expression of mutants alone revealed severe defects in plasma membrane targeting and Ca2+ signaling, which were substantially rescued by coexpression with wild-type CaSR. Biasing toward heterodimerization of wild-type and FHH/NSHPT mutants revealed that intracellular Ca2+ oscillations were insufficient to rescue plasma membrane targeting. Coexpression of the nonfunctional mutant E297K with the truncation CaSRΔ868 robustly rescued trafficking and Ca2+ signaling, whereas coexpression of distinct FHH/NSHPT mutants rescued neither trafficking nor signaling. Our study suggests that rescue of FHH/NSHPT mutants requires a steady state intracellular Ca2+ response when extracellular Ca2+ is elevated and argues that Ca2+ signaling by wild-type CaSRs rescues FHH mutant trafficking to the plasma membrane. PMID:23077345

Meiosis, egg activation, and nuclear envelope breakdown are differentially reliant on Ca2+, whereas germinal vesicle breakdown is Ca2+ independent in the mouse oocyte

NASA Technical Reports Server (NTRS)

Tombes, R. M.; Simerly, C.; Borisy, G. G.; Schatten, G.

1992-01-01

During early development, intracellular Ca2+ mobilization is not only essential for fertilization, but has also been implicated during other meiotic and mitotic events, such as germinal vesicle breakdown (GVBD) and nuclear envelope breakdown (NEBD). In this study, the roles of intracellular and extracellular Ca2+ were examined during meiotic maturation and reinitiation at parthenogenetic activation and during first mitosis in a single species using the same methodologies. Cumulus-free metaphase II mouse oocytes immediately resumed anaphase upon the induction of a large, transient Ca2+ elevation. This resumption of meiosis and associated events, such as cortical granule discharge, were not sensitive to extracellular Ca2+ removal, but were blocked by intracellular Ca2+ chelators. In contrast, meiosis I was dependent on external Ca2+; in its absence, the formation and function of the first meiotic spindle was delayed, the first polar body did not form and an interphase-like state was induced. GVBD was not dependent on external Ca2+ and showed no associated Ca2+ changes. NEBD at first mitosis in fertilized eggs, on the other hand, was frequently, but not always associated with a brief Ca2+ transient and was dependent on Ca2+ mobilization. We conclude that GVBD is Ca2+ independent, but that the dependence of NEBD on Ca2+ suggests regulation by more than one pathway. As cells develop from Ca(2+)-independent germinal vesicle oocytes to internal Ca(2+)-dependent pronuclear eggs, internal Ca2+ pools increase by approximately fourfold.

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

Investigation of the transport properties and compositions of the Ca{sub 2}RE{sub 7}Pn{sub 5}O{sub 5} series (RE=Pr, Sm, Gd, Dy; Pn=Sb, Bi)

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

Forbes, Scott; Yuan, Fang; Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044

The Ca{sub 2}RE{sub 7}Pn{sub 5}O{sub 5} phases (RE=Pr, Sm, Gd, Dy; Pn=Sb, Bi) were successfully prepared from high temperature reactions at 1225–1300 °C. These phases maintain the same structure types as the parent RE{sub 9}Pn{sub 5}O{sub 5} phases, except for a Ca/RE mixing. The study and preparation of these phases was motivated by the desire to shift the metallic type properties of the parent RE{sub 9}Pn{sub 5}O{sub 5} phases to a level more suitable for thermoelectric applications. Electrical resistivity measurements performed on pure, bulk samples indicated all phases to be narrow band gap semiconductors or semimetals, supporting the charge balancedmore » electron count of the Ca{sub 2}RE{sub 7}Pn{sub 5}O{sub 5} composition. Unfortunately, all samples are too electrically resistive for any potential usage as thermoelectrics. Electronic band structure calculations performed on idealized RE{sub 9}Pn{sub 5}O{sub 5} structures revealed the presence of a pseudogap at the Fermi level, which is consistent with the observed electrical resistivity and Seebeck coefficient behavior. - Graphical abstract: Ca substitution in RE{sub 9}Pn{sub 5}O{sub 5} leads to charge-balanced Ca{sub 2}RE{sub 7}Pn{sub 5}O{sub 5} phases with semiconducting or semimetallic properties. - Highlights: • The RE{sub 9}Pn{sub 5}O{sub 5} structure may be stabilized with calcium substitution in the form of Ca{sub 2}RE{sub 7}Pn{sub 5}O{sub 5}. • The Ca{sub 2}RE{sub 7}Pn{sub 5}O{sub 5} phases maintain the parent P 4/n structure, albeit with Ca/RE mixing. • The Ca{sub 2}RE{sub 7}Sb{sub 5}O{sub 5} phases behave as semiconductors while Ca{sub 2}RE{sub 7}Bi{sub 5}O{sub 5} are semimetals with electron-electron correlations. • Electronic structure calculations yield a semimetal-like density of states for both Ca{sub 2}RE{sub 7}Sb{sub 5}O{sub 5} and Ca{sub 2}RE{sub 7}Bi{sub 5}O{sub 5}.« less

Glucose deprivation stimulates Cu(2+) toxicity in cultured cerebellar granule neurons and Cu(2+)-dependent zinc release.

PubMed

Isaev, Nickolay K; Genrikhs, Elisaveta E; Aleksandrova, Olga P; Zelenova, Elena A; Stelmashook, Elena V

2016-05-27

Copper chloride (0.01mM, 2h) did not have significant influence on the survival of cerebellar granule neurons (CGNs) incubated in balanced salt solution. However, CuCl2 caused severe neuronal damage by glucose deprivation (GD). The glutamate NMDA-receptors blocker MK-801 partially and antioxidant N-acetyl-l-cysteine (NAC) or Zn(2+) chelator, N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) almost entirely protected CGNs from this toxic effect. Measurements of intracellular calcium ions using Fluo-4 AM, or zinc ions with FluoZin-3 AM demonstrated that 1 h-exposure to GD induced intensive increase of Fluo-4 but not FluoZin-3 fluorescence in neurons. The supplementation of solution with CuCl2 caused an increase of FluoZin-3, Fluo-4 and CellROX Green (reactive oxygen species probe) fluorescence by GD. The stimulation of Fluo-4 but not FluoZin-3 fluorescence by copper could be prevented partially by MK-801 and as well as CellROX Green fluorescence by NAC at GD. This data imply that during GD copper ions induce intense displacement zinc ions from intracellular stores, in addition free radical production, glutamate release and Ca(2+) overload of CGNs, that causes death of neurons as a result. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Carbachol-mediated pigment granule dispersion in retinal pigment epithelium requires Ca2+ and calcineurin.

PubMed

Johnson, Adam S; García, Dana M

2007-12-19

Inside bluegill (Lepomis macrochirus) retinal pigment epithelial cells, pigment granules move in response to extracellular signals. During the process of aggregation, pigment motility is directed toward the cell nucleus; in dispersion, pigment is directed away from the nucleus and into long apical processes. A number of different chemicals have been found to initiate dispersion, and carbachol (an acetylcholine analog) is one example. Previous research indicates that the carbachol-receptor interaction activates a Gq-mediated pathway which is commonly linked to Ca2+ mobilization. The purpose of the present study was to test for involvement of calcium and to probe calcium-dependent mediators to reveal their role in carbachol-mediated dispersion. Carbachol-induced pigment granule dispersion was blocked by the calcium chelator BAPTA. In contrast, the calcium channel antagonist verapamil, and incubation in Ca2+-free medium failed to block carbachol-induced dispersion. The calcineurin inhibitor cypermethrin blocked carbachol-induced dispersion; whereas, two protein kinase C inhibitors (staurosporine and bisindolylmaleimide II) failed to block carbachol-induced dispersion, and the protein kinase C activator phorbol 12-myristate 13-acetate failed to elicit dispersion. A rise in intracellular calcium is necessary for carbachol-induced dispersion; however, the Ca2+ requirement is not dependent on extracellular sources, implying that intracellular stores are sufficient to enable pigment granule dispersion to occur. Calcineurin is a likely Ca2+-dependent mediator involved in the signal cascade. Although the pathway leads to the generation of diacylglycerol and calcium (both required for the activation of certain PKC isoforms), our evidence does not support a significant role for PKC.

Carbachol-mediated pigment granule dispersion in retinal pigment epithelium requires Ca2+ and calcineurin

PubMed Central

Johnson, Adam S; García, Dana M

2007-01-01

Background Inside bluegill (Lepomis macrochirus) retinal pigment epithelial cells, pigment granules move in response to extracellular signals. During the process of aggregation, pigment motility is directed toward the cell nucleus; in dispersion, pigment is directed away from the nucleus and into long apical processes. A number of different chemicals have been found to initiate dispersion, and carbachol (an acetylcholine analog) is one example. Previous research indicates that the carbachol-receptor interaction activates a Gq-mediated pathway which is commonly linked to Ca2+ mobilization. The purpose of the present study was to test for involvement of calcium and to probe calcium-dependent mediators to reveal their role in carbachol-mediated dispersion. Results Carbachol-induced pigment granule dispersion was blocked by the calcium chelator BAPTA. In contrast, the calcium channel antagonist verapamil, and incubation in Ca2+-free medium failed to block carbachol-induced dispersion. The calcineurin inhibitor cypermethrin blocked carbachol-induced dispersion; whereas, two protein kinase C inhibitors (staurosporine and bisindolylmaleimide II) failed to block carbachol-induced dispersion, and the protein kinase C activator phorbol 12-myristate 13-acetate failed to elicit dispersion. Conclusion A rise in intracellular calcium is necessary for carbachol-induced dispersion; however, the Ca2+ requirement is not dependent on extracellular sources, implying that intracellular stores are sufficient to enable pigment granule dispersion to occur. Calcineurin is a likely Ca2+-dependent mediator involved in the signal cascade. Although the pathway leads to the generation of diacylglycerol and calcium (both required for the activation of certain PKC isoforms), our evidence does not support a significant role for PKC. PMID:18093324

17O nuclear quadrupole coupling constants of water bound to a metal ion: A gadolinium(III) case study

NASA Astrophysics Data System (ADS)

Yazyev, Oleg V.; Helm, Lothar

2006-08-01

Rotational correlation times of metal ion aqua complexes can be determined from O17 NMR relaxation rates if the quadrupole coupling constant of the bound water oxygen-17 nucleus is known. The rotational correlation time is an important parameter for the efficiency of Gd3+ complexes as magnetic resonance imaging contrast agents. Using a combination of density functional theory with classical and Car-Parrinello molecular dynamics simulations we performed a computational study of the O17 quadrupole coupling constants in model aqua ions and the [Gd(DOTA)(H2O)]- complex used in clinical diagnostics. For the inner sphere water molecule in the [Gd(DOTA)(H2O)]- complex the determined quadrupole coupling parameter χ√1+η2/3 of 8.7MHz is very similar to that of the liquid water (9.0MHz ). Very close values were also predicted for the the homoleptic aqua ions of Gd3+ and Ca2+. We conclude that the O17 quadrupole coupling parameters of water molecules coordinated to closed shell and lanthanide metal ions are similar to water molecules in the liquid state.

How Does the Ca2+-paradox Injury Induce Contracture in the Heart?—A Combined Study of the Intracellular Ca2+ Dynamics and Cell Structures in Perfused Rat Hearts—

PubMed Central

Mani, Hiroki; Tanaka, Hideo; Adachi, Tetsuya; Ikegawa, Masaya; Dai, Ping; Fujita, Naohisa; Takamatsu, Tetsuro

2015-01-01

The calcium (Ca2+)-paradox injury of the heart, induced by restoration of extracellular Ca2+ after its short-term depletion, is known to provoke cardiomyocyte contracture. However, undetermined is how the Ca2+-paradox provokes such a distinctive presentation of myocytes in the heart. To address this, we imaged sequential intracellular Ca2+ dynamics and concomitant structures of the subepicardial ventricular myocytes in fluo3-loaded, Langendorff-perfused rat hearts produced by the Ca2+ paradox. Under rapid-scanning confocal microscopy, repletion of Ca2+ following its depletion produced high-frequency Ca2+ waves in individual myocytes with asynchronous localized contractions, resulting in contracture within 10 min. Such alterations of myocytes were attenuated by 5-mM NiCl2, but not by verapamil, SEA0400, or combination of ryanodine and thapsigargin, indicating a contribution of non-specific transmembrane Ca2+ influx in the injury. However, saponin-induced membrane permeabilization of Ca2+ showed no apparent contracture despite the emergence of high-frequency Ca2+ waves, indicating an essential role of myocyte-myocyte and myocyte-extracellular matrix (ECM) mechanical connections in the Ca2+ paradox. In immunohistochemistry Ca2+ depletion produced separation of the intercalated disc that expresses cadherin and dissipation of β-dystroglycan located along the sarcolemma. Taken together, along with the trans-sarcolemmal Ca2+ influx, disruption of cell-cell and cell-ECM connections is essential for contracture in the Ca2+-paradox injury. PMID:25861132

Intramitochondrial Zn2+ accumulation via the Ca2+ uniporter contributes to acute ischemic neurodegeneration

PubMed Central

Medvedeva, Yuliya V.; Weiss, John H.

2014-01-01

Ca2+ and Zn2+ have both been implicated in the induction of acute ischemic neurodegeneration. We recently examined changes in intracellular Zn2+ and Ca2+ in CA1 pyramidal neurons subjected to oxygen glucose deprivation (OGD), and found that Zn2+ rises precede and contribute to the onset of terminal Ca2+ rises (“Ca2+ deregulation”), which are causatively linked to a lethal loss of membrane integrity. The present study seeks to examine the specific role of intramitochondrial Zn2+ accumulation in ischemic injury, using blockers of the mitochondrial Ca2+ uniporter (MCU), through which both Zn2+ and Ca2+ appear able to enter the mitochondrial matrix. In physiological extracellular Ca2+, treatment with the MCU blocker, Ruthenium Red (RR), accelerated the Ca2+ deregulation, most likely by disrupting mitochondrial Ca2+ buffering and thus accelerating the lethal cytosolic Ca2+ overload. However, when intracellular Ca2+ overload was slowed, either by adding blockers of major Ca2+ entry channels or by lowering the concentration of Ca2+ in the extracellular buffer, Ca2+ deregulation was delayed, and under these conditions either Zn2+ chelation or MCU blockade resulted in similar further delays of the Ca2+ deregulation. In parallel studies using the reactive oxygen species (ROS) indicator, hydroethidine, lowering Ca2+ surprisingly accelerated OGD induced ROS generation, and in these low Ca2+ conditions, either Zn2+ chelation or MCU block slowed the ROS generation. These studies suggest that, during acute ischemia, Zn2+ entry into mitochondria via the MCU induces mitochondrial dysfunction (including ROS generation) that occurs upstream of, and contributes to the terminal Ca2+ deregulation. PMID:24787898

Brain synaptosomes display a diadenosine tetraphosphate (Ap4A)-mediated Ca2+ influx distinct from ATP-mediated influx.

PubMed

Pivorun, E B; Nordone, A

1996-06-01

Studies undertaken to compare the effects of Ap4A and ATP on altering intrasynaptosomal Ca2+ levels from deermouse brain reveal that both ligands induce a rapid influx of extracellular Ca2+. The Ca2+ profile elicited by 167 microM Ap4A is "spike-like" (half-time for decline to baseline, 19.1 +/- 1.2 sec), in contrast to the gradual decline observed with ATP (104.0 +/- 7.4 sec). DIDS (4-4'-diisothiocyano-2,2'-disulfonic acid stilbene) and suramin preincubation alter only the ATP-induced Ca2+ profile. Cross-desensitization studies indicate that prior application of ATP does not significantly affect the Ca2+ influx elicited by Ap4A, and that prior application of Ap4A does not affect the Ca2+ influx elicited by ATP. These results demonstrate that extracellular Ap4A and ATP elicit distinct intrasynaptosomal Ca2+ influx profiles, and suggest that these two nucleotides may be interacting with distinct purinoceptor subclasses or purinoceptor-effector complexes. Subjecting the synaptosomes simultaneously to depolarization and Ap4A, or to depolarization and ATP, induces an additive effect on Ca2+ influx. Preincubation with verapamil negates the effects of depolarization without modifying the ligand-elicited Ca2+ fluxes. These results indicate the presence of Ap4A and ATP ligand-gated channels that may function as modulators of neuronal activity.

Moclobemide attenuates anoxia and glutamate-induced neuronal damage in vitro independently of interaction with glutamate receptor subtypes.

PubMed

Verleye, Marc; Steinschneider, Remy; Bernard, François Xavier; Gillardin, Jean-Marie

2007-03-23

Recent data suggested the existence of a bidirectional relation between depression and neurodegenerative diseases resulting from cerebral ischemia injury. Glutamate, a major excitatory neurotransmitter, has long been recognised to play a key role in the pathophysiology of anoxia or ischemia, due to its excessive accumulation in the extracellular space and the subsequent activation of its receptors. A characteristic response to glutamate is the increase in cytosolic Na(+) and Ca(2+) levels which is due mainly to influx from the extracellular space, with a consequent cell swelling and oxidative metabolism dysfunction. The present study examined the in vitro effects of the antidepressant and type-A monoamine oxidase inhibitor, moclobemide, in neuronal-astroglial cultures from rat cerebral cortex exposed to anoxia (for 5 and 7 h) or to glutamate (2 mM for 6 h), two in vitro models of brain ischemia. In addition, the affinity of moclobemide for the different glutamate receptor subtypes and an interaction with the cell influx of Na(+) and of Ca(2+) enhanced by veratridine and K(+) excess, respectively, were evaluated. Moclobemide (10-100 microM) included in the culture medium during anoxia or with glutamate significantly increased in a concentration-dependent manner the amount of surviving neurons compared to controls. Moclobemide displayed no binding affinity for the different glutamate receptor subtypes (IC(50)>100 microM) and did not block up to 300 microM the entry of Na(+) and of Ca(2+) activated by veratridine and K(+), respectively. These results suggest that the neuroprotective properties of moclobemide imply neither the glutamate neurotransmission nor the Na(+) and Ca(2+) channels.

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

Osteoclast cytosolic calcium, regulated by voltage-gated calcium channels and extracellular calcium, controls podosome assembly and bone resorption

NASA Technical Reports Server (NTRS)

Miyauchi, A.; Hruska, K. A.; Greenfield, E. M.; Duncan, R.; Alvarez, J.; Barattolo, R.; Colucci, S.; Zambonin-Zallone, A.; Teitelbaum, S. L.; Teti, A.

1990-01-01

The mechanisms of Ca2+ entry and their effects on cell function were investigated in cultured chicken osteoclasts and putative osteoclasts produced by fusion of mononuclear cell precursors. Voltage-gated Ca2+ channels (VGCC) were detected by the effects of membrane depolarization with K+, BAY K 8644, and dihydropyridine antagonists. K+ produced dose-dependent increases of cytosolic calcium ([Ca2+]i) in osteoclasts on glass coverslips. Half-maximal effects were achieved at 70 mM K+. The effects of K+ were completely inhibited by dihydropyridine derivative Ca2+ channel blocking agents. BAY K 8644 (5 X 10(-6) M), a VGCC agonist, stimulated Ca2+ entry which was inhibited by nicardipine. VGCCs were inactivated by the attachment of osteoclasts to bone, indicating a rapid phenotypic change in Ca2+ entry mechanisms associated with adhesion of osteoclasts to their resorption substrate. Increasing extracellular Ca2+ ([Ca2+]e) induced Ca2+ release from intracellular stores and Ca2+ influx. The Ca2+ release was blocked by dantrolene (10(-5) M), and the influx by La3+. The effects of [Ca2+]e on [Ca2+]i suggests the presence of a Ca2+ receptor on the osteoclast cell membrane that could be coupled to mechanisms regulating cell function. Expression of the [Ca2+]e effect on [Ca2+]i was similar in the presence or absence of bone matrix substrate. Each of the mechanisms producing increases in [Ca2+]i, (membrane depolarization, BAY K 8644, and [Ca2+]e) reduced expression of the osteoclast-specific adhesion structure, the podosome. The decrease in podosome expression was mirrored by a 50% decrease in bone resorptive activity. Thus, stimulated increases of osteoclast [Ca2+]i lead to cytoskeletal changes affecting cell adhesion and decreasing bone resorptive activity.

Pericellular Ca2+ recycling potentiates thrombin-evoked Ca2+ signals in human platelets

PubMed Central

Sage, Stewart O; Pugh, Nicholas; Farndale, Richard W; Harper, Alan G S

2013-01-01

We have previously demonstrated that Na+/Ca2+ exchangers (NCXs) potentiate Ca2+ signaling evoked by thapsigargin in human platelets, via their ability to modulate the secretion of autocoids from dense granules. This link was confirmed in platelets stimulated with the physiological agonist, thrombin, and experiments were performed to examine how Ca2+ removal by the NCX modulates platelet dense granule secretion. In cells loaded with the near-membrane indicator FFP-18, thrombin stimulation was observed to elicit an NCX-dependent accumulation of Ca2+ in a pericellular region around the platelets. To test whether this pericellular Ca2+ accumulation might be responsible for the influence of NCXs over platelet function, platelets were exposed to fast Ca2+ chelators or had their glycocalyx removed. Both manipulations of the pericellular Ca2+ rise reduced thrombin-evoked Ca2+ signals and dense granule secretion. Blocking Ca2+-permeable ion channels had a similar effect, suggesting that Ca2+ exported into the pericellular region is able to recycle back into the platelet cytosol. Single cell imaging with extracellular Fluo-4 indicated that thrombin-evoked rises in extracellular [Ca2+] occurred within the boundary described by the cell surface, suggesting their presence within the open canalicular system (OCS). FFP-18 fluorescence was similarly distributed. These data suggest that upon thrombin stimulation, NCX activity creates a rise in [Ca2+] within the pericellular region of the platelet from where it recycles back into the platelet cytosol, acting to both accelerate dense granule secretion and maintain the initial rise in cytosolic [Ca2+]. PMID:24303163

Mitochondrial Ca2+ homeostasis during Ca2+ influx and Ca2+ release in gastric myocytes from Bufo marinus

PubMed Central

Drummond, Robert M; Mix, T Christian H; Tuft, Richard A; Walsh, John V; Fay, Fredric S

2000-01-01

The Ca2+-sensitive fluorescent indicator rhod-2 was used to monitor mitochondrial Ca2+ concentration ([Ca2+]m) in gastric smooth muscle cells from Bufo marinus. In some studies, fura-2 was used in combination with rhod-2, allowing simultaneous measurement of cytoplasmic Ca2+ concentration ([Ca2+]i) and [Ca2+]m, respectively. During a short train of depolarizations, which causes Ca2+ influx from the extracellular medium, there was an increase in both [Ca2+]i and [Ca2+]m. The half-time (t½) to peak for the increase in [Ca2+]m was considerably longer than the t½ to peak for the increase in [Ca2+]i. [Ca2+]m remained elevated for tens of seconds after [Ca2+]i had returned to its resting value. Stimulation with caffeine, which causes release of Ca2+ from the sarcoplasmic reticulum (SR), also produced increases in both [Ca2+]i and [Ca2+]m. The values of t½ to peak for the increase in [Ca2+] in both cytoplasm and mitochondria were similar; however, [Ca2+]i returned to baseline values much faster than [Ca2+]m. Using a wide-field digital imaging microscope, changes in [Ca2+]m were monitored within individual mitochondria in situ, during stimulation of Ca2+ influx or Ca2+ release from the SR. Mitochondrial Ca2+ uptake during depolarizing stimulation caused depolarization of the mitochondrial membrane potential. The mitochondrial membrane potential recovered considerably faster than the recovery of [Ca2+]m. This study shows that Ca2+ influx from the extracellular medium and Ca2+ release from the SR are capable of increasing [Ca2+]m in smooth muscle cells. The efflux of Ca2+ from the mitochondria is a slow process and appears to be dependent upon the amount of Ca2+ in the SR. PMID:10713963

Differences in perilymphatic space enhancement and adverse inflammatory reaction after intratympanic injection of two different gadolinium agents: A 9.4-T magnetic resonance imaging study.

PubMed

Park, Mina; Lee, Ho Sun; Kim, Hyeonjin; Oh, Seung Ha; Lee, Jun Ho; Suh, Myung-Whan

2016-03-01

To compare the inner ear enhancement after intratympanic injection of two widely used gadolinium (Gd) agents by 9.4 T micro-magnetic resonance imaging (MRI) and to investigate the effects of Gd on the inner ear. Twelve ears of six rats received intratympanic administration of 1/5 diluted Gd agents: gadoterate meglumine (Gd-DTPA) for the left ear and gadodiamide (Gd-DTPA-BMA) for the right ear. MRI was performed every 30 min from 1 to 4 h after administration. The normalized signal intensity was evaluated by quantitative analysis at each cochlear fluid compartment. Eight, six, and seven ears treated with Gd-DTPA, Gd-DPTA-BMA, and nothing as controls, respectively, were processed for histological evaluation after MRI. After hematoxylin & eosin staining, adverse inflammatory reactions were evaluated for turbid aggregation and lymphocytes. The perilymphatic enhancement of Gd-DTPA was superior to that of Gd-DTPA-BMA regardless of cochlear turn, compartment, and time point. Inflammatory reactions were found in 4/8 (50.0%) and 4/6 (66.6%) ears administered Gd-DTPA and Gd-DTPA-BMA, respectively. Regardless of the contrast agent used, inflammatory reactions were most definite in the scala tympani of the basal turn, i.e., near the round window. Slightly greater inflammatory reactions were observed in ears injected with Gd-DTPA-BMA compared to Gd-DTPA although the difference was not statistically significant. No inflammatory reaction was observed in any of the seven controls. The auditory brainstem response threshold was 11.8 ± 2.5 dB SPL before IT Gd injection and it did not change for up to 5 days (15.4 ± 6.6 dB SPL) post-injection. Gd-DTPA was superior to Gd-DTPA-BMA for visualization of the inner ear. Administration of diluted Gd agents intratympanically may induce considerable inflammatory reactions in the inner ear. Copyright © 2015 Elsevier B.V. All rights reserved.

Laser-induced Breakdown Spectroscopy: A New Approach for Nanoparticle's Mapping and Quantification in Organ Tissue

PubMed Central

Sancey, Lucie; Motto-Ros, Vincent; Kotb, Shady; Wang, Xiaochun; Lux, François; Panczer, Gérard; Yu, Jin; Tillement, Olivier

2014-01-01

Emission spectroscopy of laser-induced plasma was applied to elemental analysis of biological samples. Laser-induced breakdown spectroscopy (LIBS) performed on thin sections of rodent tissues: kidneys and tumor, allows the detection of inorganic elements such as (i) Na, Ca, Cu, Mg, P, and Fe, naturally present in the body and (ii) Si and Gd, detected after the injection of gadolinium-based nanoparticles. The animals were euthanized 1 to 24 hr after intravenous injection of particles. A two-dimensional scan of the sample, performed using a motorized micrometric 3D-stage, allowed the infrared laser beam exploring the surface with a lateral resolution less than 100 μm. Quantitative chemical images of Gd element inside the organ were obtained with sub-mM sensitivity. LIBS offers a simple and robust method to study the distribution of inorganic materials without any specific labeling. Moreover, the compatibility of the setup with standard optical microscopy emphasizes its potential to provide multiple images of the same biological tissue with different types of response: elemental, molecular, or cellular. PMID:24962015

Electronic excitations and self-trapping of electrons and holes in CaSO4

NASA Astrophysics Data System (ADS)

Kudryavtseva, I.; Klopov, M.; Lushchik, A.; Lushchik, Ch; Maaroos, A.; Pishtshev, A.

2014-04-01

A first-principles study of the electronic properties of a CaSO4 anhydrite structural phase has been performed. A theoretical estimation for the fundamental band gap (p → s transitions) is Eg = 9.6 eV and a proper threshold for p → d transitions is Epd = 10.8 eV. These values agree with the data obtained for a set of CaSO4 doped with Gd3+, Dy3+, Tm3+ and Tb3+ ions using the methods of low-temperature highly sensitive luminescence and thermoactivation spectroscopy. The results are consistent with theoretical predictions of a possible low-temperature self-trapping of oxygen p-holes. The hopping diffusion of hole polarons starts above ˜40 K and is accompanied by a ˜50-60 K peak of thermally stimulated luminescence of RE3+ ions caused due to the recombination of hole polarons with the electrons localized at RE3+. There is no direct evidence of the self-trapping of heavy d-electrons, however, one can argue that their motion rather differs from that of conduction s-electrons.

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.

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.

Glass-ceramic nuclear waste forms obtained by crystallization of SiO 2-Al 2O 3-CaO-ZrO 2-TiO 2 glasses containing lanthanides (Ce, Nd, Eu, Gd, Yb) and actinides (Th): Study of the crystallization from the surface

NASA Astrophysics Data System (ADS)

Loiseau, P.; Caurant, D.

2010-07-01

Glass-ceramic materials containing zirconolite (nominally CaZrTi 2O 7) crystals in their bulk can be envisaged as potential waste forms for minor actinides (Np, Am, Cm) and Pu immobilization. In this study such matrices are synthesized by crystallization of SiO 2-Al 2O 3-CaO-ZrO 2-TiO 2 glasses containing lanthanides (Ce, Nd, Eu, Gd, Yb) and actinides (Th) as surrogates. A thin partially crystallized layer containing titanite and anorthite (nominally CaTiSiO 5 and CaAl 2Si 2O 8, respectively) growing from glass surface is also observed. The effect of the nature and concentration of surrogates on the structure, the microstructure and the composition of the crystals formed in the surface layer is presented in this paper. Titanite is the only crystalline phase able to significantly incorporate trivalent lanthanides whereas ThO 2 precipitates in the layer. The crystal growth thermal treatment duration (2-300 h) at high temperature (1050-1200 °C) is shown to strongly affect glass-ceramics microstructure. For the system studied in this paper, it appears that zirconolite is not thermodynamically stable in comparison with titanite growing form glass surface. Nevertheless, for kinetic reasons, such transformation (i.e. zirconolite disappearance to the benefit of titanite) is not expected to occur during interim storage and disposal of the glass-ceramic waste forms because their temperature will never exceed a few hundred degrees.

Modulation of Gardos channel activity by oxidants and oxygen tension: effects of 1-chloro-2,4-dinitrobenzene and phenazine methosulphate.

PubMed

Gibson, John S; Muzyamba, Morris C

2004-05-01

We compare the effects of 1-chloro-2,4-dinitrobenzene (CDNB) and phenazine methosulphate (PMS) on Gardos channel activity in normal human red cells. Both stimulate channel activity, both are dependent on the presence of extracellular Ca2+, and neither is affected by inhibitors of protein (de)phosphorylation. Of the two, PMS has a considerably greater effect. In addition, a major difference is that whilst CDNB has a greater stimulatory effect in oxygenated cells, by contrast, PMS is more effective in deoxygenated cells. These actions are correlated with ca. 30% inhibition of the plasma membrane Ca2+ pump (PMCA) and an increased sensitivity of the Gardos channel to Ca2+ (EC50 falling to about 150 nM). These findings are important in understanding how oxidants alter red cell cation permeability and may be relevant to the abnormal permeability phenotype shown by deoxygenated sickle cells.

Carbon-Based Nanostructures as Advanced Contrast Agents for Magnetic Resonance Imaging

NASA Astrophysics Data System (ADS)

Ananta Narayanan, Jeyarama S.

2011-12-01

Superparamagnetic carbon-based nanostructures are presented as contrast agents (CAs) for advanced imaging applications such as cellular and molecular imaging using magnetic resonance imaging (MRI). Gadolinium-loaded, ultra-short single-walled carbon nanotubes (gadonanotubes; GNTs) are shown to have extremely high r1 relaxivities (contrast enhancement efficacy), especially at low-magnetic field strengths. The inherent lipophilicity of GNTs provides them the ability to image cells at low magnetic field strength. A carboxylated dextran-coated GNT (GadoDex) has been synthesized and proposed as a new biocompatible high-performance MRI CA. The r1 relaxivity is ca. 20 times greater than for other paramagnetic Gd-based CAs. This enhanced relaxivity for GadoDex is due to the synergistic effects of an increased molecular tumbling time (tauR) and a faster proton exchange rate (taum). GNTs also exhibit very large transverse relaxivities (r2) at high magnetic fields (≥ 3 T). The dependence of the transverse relaxation rates (especially R2*) of labeled cells on GNT concentration offers the possibility to quantify cell population in vivo using R2* mapping. The cell-labeling efficiency and high transverse relaxivities of GNTs has enabled the first non-iron oxide-based single-cell imaging using MRI. The residual metal catalyst particles of SWNT materials also have transverse relaxation properties. All of the SWNT materials exhibit superior transverse relaxation properties. However, purified SWNTs and US-tubes with less residual metal content exhibit better transverse relaxivities (r2), demonstrating the importance of the SWNT structure for enhanced MRI CA performance. A strategy to improve the r1 relaxivity of Gd-CAs by geometrically confining them within porous silicon particles (SiMPs) has been investigated. The enhancement in relaxivity is attributed to the slow diffusion of water molecules through the pores and the increase in the molecular tumbling time of the nanoconstruct. The universality of the strategy has been demonstrated for GNTs, gadofullerols and clinically-used MagnevistRTM. In summary, primary nanoscale confinement of Gd3+ ions in US-tubes has resulted in a new class of CAs which could revitalize low-field contrast-enhanced MRI, while extending and complementing current high-field MRI technology, as well. The observed boost in relaxivity upon a secondary nanoscale confinement of Gd-CAs within SiMPs suggests that additional unforeseen nanoscale effects may have the potential to further boost performance of MRI CAs.

ABH antigens as recognition sites for the activation of red blood cell anion exchange by the lectin ulex europaeus agglutinin I.

PubMed

Engelmann, B

1993-11-01

The blood group antigen H (blood group O) and fucose-specific lectin Ulex europaeus agglutinin I (UEA1) (10 micrograms/ml) was found to increase the rate constant of Cl- efflux into 100 mM Na+ oxalate media by about 40% in erythrocytes taken from antigen H donors. In 100 mM K+ oxalate, 150 mM Na+ pyruvate and in 150 mM Na+ acetate media the lectin elevated the rate constant of Cl- efflux by 20-50%. The acceleration of Cl- efflux by UEA1 was completely blocked by 10 microM 4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid (DIDS) indicating that the effect of the lectin is mediated by the anion exchanger of human erythrocytes (band 3 protein). In antigen A1 erythrocytes no significant stimulation of anion exchange by UEA1 was seen. The activation of Cl- efflux was completely prevented by addition of 1 mM fucose to the medium. These results suggest that the effect of UEA1 is mediated through interaction with the fucose residues of H antigens. Increasing extracellular Ca++ from 0.5 to 5 mM in Na+ pyruvate or Na+ acetate media slightly reduced the acceleration of anion exchange by the lectin. On the other hand, replacing part of extracellular chloride by bicarbonate did not considerably alter the (previously reported) stimulatory effect of UEA1 on red blood cell Ca++ uptake. This suggests that the acceleration of anion exchange and of Ca++ uptake by UEA1, respectively, are mediated by different mechanisms. It is concluded that UEA1 activates anion exchange of human erythrocytes most probably by a direct interaction with H antigens present on extracellular domains of the band 3 protein.

Intercellular signal communication among odontoblasts and trigeminal ganglion neurons via glutamate.

PubMed

Nishiyama, A; Sato, M; Kimura, M; Katakura, A; Tazaki, M; Shibukawa, Y

2016-11-01

Various stimuli to the exposed surface of dentin induce changes in the hydrodynamic force inside the dentinal tubules resulting in dentinal pain. Recent evidences indicate that mechano-sensor channels, such as the transient receptor potential channels, in odontoblasts receive these hydrodynamic forces and trigger the release of ATP to the pulpal neurons, to generate dentinal pain. A recent study, however, has shown that odontoblasts also express glutamate receptors (GluRs). This implies that cells in the dental pulp tissue have the ability to release glutamate, which acts as a functional intercellular mediator to establish inter-odontoblast and odontoblast-trigeminal ganglion (TG) neuron signal communication. To investigate the intercellular signal communication, we applied mechanical stimulation to odontoblasts and measured the intracellular free Ca 2+ concentration ([Ca 2+ ] i ). During mechanical stimulation in the presence of extracellular Ca 2+ , we observed a transient [Ca 2+ ] i increase not only in single stimulated odontoblasts, but also in adjacent odontoblasts. We could not observe these responses in the absence of extracellular Ca 2+ . [Ca 2+ ] i increases in the neighboring odontoblasts during mechanical stimulation of single odontoblasts were inhibited by antagonists of metabotropic glutamate receptors (mGluRs) as well as glutamate-permeable anion channels. In the odontoblast-TG neuron coculture, we observed an increase in [Ca 2+ ] i in the stimulated odontoblasts and TG neurons, in response to direct mechanical stimulation of single odontoblasts. These [Ca 2+ ] i increases in the neighboring TG neurons were inhibited by antagonists for mGluRs. The [Ca 2+ ] i increases in the stimulated odontoblasts were also inhibited by mGluRs antagonists. We further confirmed that the odontoblasts express group I, II, and III mGluRs. However, we could not record any currents evoked from odontoblasts near the mechanically stimulated odontoblast, with or without extracellular Mg 2+ , indicating that N-methyl-d-aspartic acid receptor does not contribute to inter-odontoblast signal communication. The results suggest that a mechanically stimulated odontoblast is capable of releasing glutamate into the extracellular space via glutamate-permeable anion channels. The released glutamate activates mGluRs on the odontoblasts in an autocrine/paracrine manner, forming an inter-odontoblasts communication, which drives dentin formation via odontoblast-odontoblast signal communication. Glutamate and mGluRs also mediate neurotransmission between the odontoblasts and neurons in the dental pulp to modulate sensory signal transmission for dentinal sensitivity. Copyright © 2016 Elsevier Ltd. All rights reserved.

Lanthanum manganite-based air electrode for solid oxide fuel cells

DOEpatents

Ruka, Roswell J.; Kuo, Lewis; Li, Baozhen

1999-01-01

An air electrode material for a solid oxide fuel cell is disclosed. The electrode material is based on lanthanum manganite having a perovskite-like crystal structure ABO.sub.3. The A-site of the air electrode material preferably comprises La, Ca, Ce and at least one lanthanide selected from Sm, Gd, Dy, Er, Y and Nd. The B-site of the electrode material comprises Mn with substantially no dopants. The ratio of A:B is preferably slightly above 1. A preferred air electrode composition is of the formula La.sub.w Ca.sub.x Ln.sub.y Ce.sub.z MnO.sub.3, wherein Ln comprises at least one lanthanide selected from Sm, Gd, Dy, Er, Y and Nd, w is from about 0.55 to about 0.56, x is from about 0.255 to about 0.265, y is from about 0.175 to about 0.185, and z is from about 0.005 to about 0.02. The air electrode material possesses advantageous chemical and electrical properties as well as favorable thermal expansion and thermal cycle shrinkage characteristics.

Lanthanum manganite-based air electrode for solid oxide fuel cells

DOEpatents

Ruka, R.J.; Kuo, L.; Li, B.

1999-06-29

An air electrode material for a solid oxide fuel cell is disclosed. The electrode material is based on lanthanum manganite having a perovskite-like crystal structure ABO[sub 3]. The A-site of the air electrode material preferably comprises La, Ca, Ce and at least one lanthanide selected from Sm, Gd, Dy, Er, Y and Nd. The B-site of the electrode material comprises Mn with substantially no dopants. The ratio of A:B is preferably slightly above 1. A preferred air electrode composition is of the formula La[sub w]Ca[sub x]Ln[sub y]Ce[sub z]MnO[sub 3], wherein Ln comprises at least one lanthanide selected from Sm, Gd, Dy, Er, Y and Nd, w is from about 0.55 to about 0.56, x is from about 0.255 to about 0.265, y is from about 0.175 to about 0.185, and z is from about 0.005 to about 0.02. The air electrode material possesses advantageous chemical and electrical properties as well as favorable thermal expansion and thermal cycle shrinkage characteristics. 10 figs.

Extracellular Ca2+-induced force restoration in K+-depressed skeletal muscle of the mouse involves an elevation of [K+]i: implications for fatigue

PubMed Central

Leader, John P.; Loiselle, Denis S.; Higgins, Amanda; Lin, Wei; Renaud, Jean-Marc

2015-01-01

We examined whether a Ca2+-K+ interaction was a potential mechanism operating during fatigue with repeated tetani in isolated mouse muscles. Raising the extracellular Ca2+ concentration ([Ca2+]o) from 1.3 to 10 mM in K+-depressed slow-twitch soleus and/or fast-twitch extensor digitorum longus muscles caused the following: 1) increase of intracellular K+ activity by 20–60 mM (raised intracellular K+ content, unchanged intracellular fluid volume), so that the K+-equilibrium potential increased by ∼10 mV and resting membrane potential repolarized by 5–10 mV; 2) large restoration of action potential amplitude (16–54 mV); 3) considerable recovery of excitable fibers (∼50% total); and 4) restoration of peak force with the peak tetanic force-extracellular K+ concentration ([K+]o) relationship shifting rightward toward higher [K+]o. Double-sigmoid curve-fitting to fatigue profiles (125 Hz for 500 ms, every second for 100 s) showed that prior exposure to raised [K+]o (7 mM) increased, whereas lowered [K+]o (2 mM) decreased, the rate and extent of force loss during the late phase of fatigue (second sigmoid) in soleus, hence implying a K+ dependence for late fatigue. Prior exposure to 10 mM [Ca2+]o slowed late fatigue in both muscle types, but was without effect on the extent of fatigue. These combined findings support our notion that a Ca2+-K+ interaction is plausible during severe fatigue in both muscle types. We speculate that a diminished transsarcolemmal K+ gradient and lowered [Ca2+]o contribute to late fatigue through reduced action potential amplitude and excitability. The raised [Ca2+]o-induced slowing of fatigue is likely to be mediated by a higher intracellular K+ activity, which prolongs the time before stimulation-induced K+ efflux depolarizes the sarcolemma sufficiently to interfere with action potentials. PMID:25571990

Erythrocyte ion channels in regulation of apoptosis.

PubMed

Lang, Florian; Birka, Christina; Myssina, Svetlana; Lang, Karl S; Lang, Philipp A; Tanneur, Valerie; Duranton, Christophe; Wieder, Thomas; Huber, Stephan M

2004-01-01

Erythrocytes lack mitochondria and nuclei, key organelles in the regulation of apoptosis. Until recently, erythrocytes were thus not considered subject to this type of cell death. However, exposure of erythrocytes to the Ca2+ ionophore ionomycin was shown to induce cell shrinkage, cell membrane blebbing and breakdown of phosphatidylserine asymmetry with subsequent phosphatidylserine exposure at the cell surface, all typical features of apoptosis. Further studies revealed the participation of ion channels in the regulation of erythrocyte "apoptosis." Osmotic shock, oxidative stress and energy depletion all activate a Ca2(+)-permeable non-selective cation channel in the erythrocyte cell membrane. The subsequent increase of Ca2+ concentration stimulates a scramblase leading to breakdown of cell membrane phosphatidylserine asymmetry and activates Ca2+ sensitive K+ (Gardos) channels leading to KCl loss and (further) cell shrinkage. Phosphatidylserine exposure and cell shrinkage are blunted in the nominal absence of extracellular Ca2+, in the presence of the cation channel inhibitors amiloride or ethylisopropylamiloride, at increased extracellular K+ or in the presence of the Gardos channel inhibitors clotrimazole or charybdotoxin. Thus, increase of cytosolic Ca2+ and cellular loss of K+ participate in the triggering of erythrocyte scramblase. Nevertheless, phosphatidylserine exposure is not completely abrogated in the nominal absence of Ca2+, pointing to additional Ca2(+)-independent pathways. One of those is activation of sphingomyelinase with subsequent formation of ceramide which in turn leads to stimulation of erythrocyte scramblase. The exposure of phosphatidylserine at the extracellular face of the cell membrane stimulates phagocytes to engulf the apoptotic erythrocytes. Thus, sustained activation of the cation channels eventually leads to clearance of affected erythrocytes from peripheral blood. Erythropoietin inhibits the non-selective cation channel and thus interferes with erythrocyte "apoptosis." Susceptibility to scramblase activation is enhanced in thalassemia, sickle cell disease and glucose-6-phosphate dehydrogenase deficiency. Infection with Plasmodium falciparum leads to activation of the cation channel eventually triggering erythrocyte "apoptosis."

Synthesis and characterization of rare-earth-doped calcium tungstate nanocrystals

NASA Astrophysics Data System (ADS)

Suneeta, P.; Rajesh, Ch.; Ramana, M. V.

2018-02-01

In this paper, we report synthesis and characterization of rare-earth-ion-doped calcium tungstate (CaWO4) nanocrystals (NCs). Rare-earth ions, such as gadolinium (Gd), neodymium (Nd), praseodymium (Pr), samarium (Sm) and holmium (Ho), were successfully doped in the CaWO4 NCs by changing the synthesis conditions. The adopted synthesis route was found to be fast and eco-friendly. Structural characterizations, such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and compositional analysis, were performed using energy dispersive analysis of X-rays (EDAX) on as-synthesized NCs. The results indicate the size of the NCs ranging between 47 to 68nm and incorporation of rare-earth ions in CaWO4 NCs.

Involvement of intracellular Zn2+ signaling in LTP at perforant pathway-CA1 pyramidal cell synapse.

PubMed

Tamano, Haruna; Nishio, Ryusuke; Takeda, Atsushi

2017-07-01

Physiological significance of synaptic Zn 2+ signaling was examined at perforant pathway-CA1 pyramidal cell synapses. In vivo long-term potentiation (LTP) at perforant pathway-CA1 pyramidal cell synapses was induced using a recording electrode attached to a microdialysis probe and the recording region was locally perfused with artificial cerebrospinal fluid (ACSF) via the microdialysis probe. Perforant pathway LTP was not attenuated under perfusion with CaEDTA (10 mM), an extracellular Zn 2+ chelator, but attenuated under perfusion with ZnAF-2DA (50 μM), an intracellular Zn 2+ chelator, suggesting that intracellular Zn 2+ signaling is required for perforant pathway LTP. Even in rat brain slices bathed in CaEDTA in ACSF, intracellular Zn 2+ level, which was measured with intracellular ZnAF-2, was increased in the stratum lacunosum-moleculare where perforant pathway-CA1 pyramidal cell synapses were contained after tetanic stimulation. These results suggest that intracellular Zn 2+ signaling, which originates in internal stores/proteins, is involved in LTP at perforant pathway-CA1 pyramidal cell synapses. Because the influx of extracellular Zn 2+ , which originates in presynaptic Zn 2+ release, is involved in LTP at Schaffer collateral-CA1 pyramidal cell synapses, synapse-dependent Zn 2+ dynamics may be involved in plasticity of postsynaptic CA1 pyramidal cells. © 2017 Wiley Periodicals, Inc.

Intracellular calcium levels determine differential modulation of allosteric interactions within G protein-coupled receptor heteromers.

PubMed

Navarro, Gemma; Aguinaga, David; Moreno, Estefania; Hradsky, Johannes; Reddy, Pasham P; Cortés, Antoni; Mallol, Josefa; Casadó, Vicent; Mikhaylova, Marina; Kreutz, Michael R; Lluís, Carme; Canela, Enric I; McCormick, Peter J; Ferré, Sergi

2014-11-20

The pharmacological significance of the adenosine A2A receptor (A2AR)-dopamine D2 receptor (D2R) heteromer is well established and it is being considered as an important target for the treatment of Parkinson’s disease and other neuropsychiatric disorders. However, the physiological factors that control its distinctive biochemical properties are still unknown. We demonstrate that different intracellular Ca2+ levels exert a differential modulation of A2AR-D2R heteromer-mediated adenylyl-cyclase and MAPK signaling in striatal cells. This depends on the ability of low and high Ca2+ levels to promote a selective interaction of the heteromer with the neuronal Ca2+-binding proteins NCS-1 and calneuron-1, respectively. These Ca2+-binding proteins differentially modulate allosteric interactions within the A2AR-D2R heteromer, which constitutes a unique cellular device that integrates extracellular (adenosine and dopamine) and intracellular (Ca+2) signals to produce a specific functional response.

The Extracellular Calcium-Sensing Receptor in the Intestine: Evidence for Regulation of Colonic Absorption, Secretion, Motility, and Immunity

PubMed Central

Tang, Lieqi; Cheng, Catherine Y.; Sun, Xiangrong; Pedicone, Alexandra J.; Mohamadzadeh, Mansour; Cheng, Sam X.

2016-01-01

Different from other epithelia, the intestinal epithelium has the complex task of providing a barrier impeding the entry of toxins, food antigens, and microbes, while at the same time allowing for the transfer of nutrients, electrolytes, water, and microbial metabolites. These molecules/organisms are transported either transcellularly, crossing the apical and basolateral membranes of enterocytes, or paracellularly, passing through the space between enterocytes. Accordingly, the intestinal epithelium can affect energy metabolism, fluid balance, as well as immune response and tolerance. To help accomplish these complex tasks, the intestinal epithelium has evolved many sensing receptor mechanisms. Yet, their roles and functions are only now beginning to be elucidated. This article explores one such sensing receptor mechanism, carried out by the extracellular calcium-sensing receptor (CaSR). In addition to its established function as a nutrient sensor, coordinating food digestion, nutrient absorption, and regulating energy metabolism, we present evidence for the emerging role of CaSR in the control of intestinal fluid homeostasis and immune balance. An additional role in the modulation of the enteric nerve activity and motility is also discussed. Clearly, CaSR has profound effects on many aspects of intestinal function. Nevertheless, more work is needed to fully understand all functions of CaSR in the intestine, including detailed mechanisms of action and specific pathways involved. Considering the essential roles CaSR plays in gastrointestinal physiology and immunology, research may lead to a translational opportunity for the development of novel therapies that are based on CaSR's unique property of using simple nutrients such as calcium, polyamines, and certain amino acids/oligopeptides as activators. It is possible that, through targeting of intestinal CaSR with a combination of specific nutrients, oral solutions that are both inexpensive and practical may be developed to help in conditioning the gut microenvironment and in maintaining digestive health. PMID:27458380

The Extracellular Calcium-Sensing Receptor in the Intestine: Evidence for Regulation of Colonic Absorption, Secretion, Motility, and Immunity.

PubMed

Tang, Lieqi; Cheng, Catherine Y; Sun, Xiangrong; Pedicone, Alexandra J; Mohamadzadeh, Mansour; Cheng, Sam X

2016-01-01

Different from other epithelia, the intestinal epithelium has the complex task of providing a barrier impeding the entry of toxins, food antigens, and microbes, while at the same time allowing for the transfer of nutrients, electrolytes, water, and microbial metabolites. These molecules/organisms are transported either transcellularly, crossing the apical and basolateral membranes of enterocytes, or paracellularly, passing through the space between enterocytes. Accordingly, the intestinal epithelium can affect energy metabolism, fluid balance, as well as immune response and tolerance. To help accomplish these complex tasks, the intestinal epithelium has evolved many sensing receptor mechanisms. Yet, their roles and functions are only now beginning to be elucidated. This article explores one such sensing receptor mechanism, carried out by the extracellular calcium-sensing receptor (CaSR). In addition to its established function as a nutrient sensor, coordinating food digestion, nutrient absorption, and regulating energy metabolism, we present evidence for the emerging role of CaSR in the control of intestinal fluid homeostasis and immune balance. An additional role in the modulation of the enteric nerve activity and motility is also discussed. Clearly, CaSR has profound effects on many aspects of intestinal function. Nevertheless, more work is needed to fully understand all functions of CaSR in the intestine, including detailed mechanisms of action and specific pathways involved. Considering the essential roles CaSR plays in gastrointestinal physiology and immunology, research may lead to a translational opportunity for the development of novel therapies that are based on CaSR's unique property of using simple nutrients such as calcium, polyamines, and certain amino acids/oligopeptides as activators. It is possible that, through targeting of intestinal CaSR with a combination of specific nutrients, oral solutions that are both inexpensive and practical may be developed to help in conditioning the gut microenvironment and in maintaining digestive health.

Fluorescence Imaging Study of Extracellular Zinc at the Hippocampal Mossy Fiber Synapse

PubMed Central

Bastian, Chinthasagar; Li, Yang V

2010-01-01

Although synaptically-released, vesicular Zn2+ has been proposed to play a neuromodulatory or neuronal signaling role at the mossy fiber-CA3 synapse, Zn2+ release remains controversial, especially when detected using fluorescent imaging. In the present study, we investigated synaptically released Zn2+ at the mossy fiber synapse in rat hippocampal slices using three chemically distinct, fluorescent Zn2+ indicators. The indicators employed for this study were cell membrane impermeable (or extracellular) Newport Green (KD Zn2+ ~ 1 μM), Zinpyr-4 (KD Zn2+ ~ 1 nM) and FluoZin-3 (KD Zn2+ ~ 15 nM), chosen, in part, for their distinct dissociation constants. Among the three indicators, FluoZin-3 was also sensitive to Ca2+ (KD Ca2+ ~ 100 μM) which was present in the extracellular medium ([Ca2+]o > 2mM). Hippocampal slices loaded with either Newport Green or FluoZin-3 showed increases in fluorescence after electrical stimulation of the mossy fiber pathway. These results are consistent with previous studies suggesting the presence of synaptically-released Zn2+ in the extracellular space during neuronal activities; however, the rise in FluoZin-3 fluorescence observed was complicated by the data that the addition of exogenous Zn2+ onto FluoZin-3 loaded slices gave little change in fluorescence. In the slices loaded with the high-affinity indicator Zinpyr-4, there was little change in fluorescence after mossy fiber activation by electrical stimulation. Further study revealed that the sensitivity of Zinpyr-4 was mitigated by saturation with Zn2+ contamination from the slice. These data suggest that the sensitivity and selectivity of a probe may affect individual outcomes in a given experimental system. PMID:17485170

Extracellular calcium (Ca2+o)-sensing receptor in a mouse monocyte-macrophage cell line (J774): potential mediator of the actions of Ca2+o on the function of J774 cells

NASA Technical Reports Server (NTRS)

Yamaguchi, T.; Kifor, O.; Chattopadhyay, N.; Bai, M.; 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. Macrophage-like mononuclear cells appear at sites of osteoclastic bone resorption during bone remodeling and may play a role 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 bone marrow mononuclear cells in the vicinity, leading us to investigate whether such mononuclear cells express the CaR. In this study, we used the mouse J774 cell line, which exhibits a pure monocyte-macrophage phenotype. Both immunocytochemistry and Western blot analysis, using polyclonal antisera specific for the CaR, detected CaR protein in J774 cells. The use of reverse transcriptase-polymerase chain reaction with CaR-specific primers, including a set of intron-spanning primers, followed by nucleotide sequencing of the amplified products, also identified CaR transcripts in J774 cells. Exposure of J774 cells to high Ca2+o (2.8 mM or more) or the polycationic CaR agonist, neomycin (100 microM), stimulated both chemotaxis and DNA synthesis in J774 cells. Therefore, taken together, our data strongly suggest that the monocyte-macrophage cell line, J774, possesses both CaR protein and mRNA very similar, if not identical, to those in parathyroid and kidney.

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

PubMed Central

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

2012-01-01

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

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

PubMed

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

2009-03-04

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

Effect of quinine on the release of catecholamines from bovine cultured chromaffin cells.

PubMed Central

Tang, R.; Novas, M. L.; Glavinovic, M. I.; Trifaró, J. M.

1990-01-01

1. The effects of quinine on catecholamine release from cultured bovine chromaffin cells were studied. 2. Quinine (25-400 microM) produced a dose-related inhibition of catecholamine release in response to depolarizing concentrations (12.5-50 mM) of K+. 3. The inhibition of the secretory response to high K+ produced by quinine decreased with the increase in the extracellular concentration of Ca2+. 4. Stimulation of cultured chromaffin cells with 50 mM K+ produced a significant increase in Ca2+ influx. In the presence of 100 microM quinine a 54% inhibition of the K(+)-induced Ca2+ influx was observed. 5. Quinine treatment of chromaffin cell cultures produced a small but significant decrease in membrane resting potential and a less pronounced depolarization in response to 50 mM K+. 6. The results suggest that the inhibition of the K(+)-evoked release of catecholamines produced by quinine is at least partly due to a decrease in Ca2+ influx. Ca2+ influx is lower because quinine reduces the sensitivity of the membrane potential to changes in extracellular K+ but direct effects of quinine on Ca2+ channels cannot be excluded. PMID:2158846

Ionotropic NMDA receptor signaling is required for the induction of long-term depression in the mouse hippocampal CA1 region.

PubMed

Babiec, Walter E; Guglietta, Ryan; Jami, Shekib A; Morishita, Wade; Malenka, Robert C; O'Dell, Thomas J

2014-04-09

Previous studies have provided strong support for the notion that NMDAR-mediated increases in postsynaptic Ca(2+) have a crucial role in the induction of long-term depression (LTD). This view has recently been challenged, however, by findings suggesting that LTD induction is instead attributable to an ion channel-independent, metabotropic form of NMDAR signaling. Thus, to explore the role of ionotropic versus metabotropic NMDAR signaling in LTD, we examined the effects of varying extracellular Ca(2+) levels or blocking NMDAR channel ion fluxes with MK-801 on LTD and NMDAR signaling in the mouse hippocampal CA1 region. We find that the induction of LTD in the adult hippocampus is highly sensitive to extracellular Ca(2+) levels and that MK-801 blocks NMDAR-dependent LTD in the hippocampus of both adult and immature mice. Moreover, MK-801 inhibits NMDAR-mediated activation of p38-MAPK and dephosphorylation of AMPAR GluA1 subunits at sites implicated in LTD. Thus, our results indicate that the induction of LTD in the hippocampal CA1 region is dependent on ionotropic, rather than metabotropic, NMDAR signaling.

Effect of angiotensin II-induced arterial hypertension on the voltage-dependent contractions of mouse arteries.

PubMed

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

2016-02-01

Arterial hypertension (AHT) affects the voltage dependency of L-type Ca(2+) channels in cardiomyocytes. We analyzed the effect of angiotensin II (AngII)-induced AHT on L-type Ca(2+) channel-mediated isometric contractions in conduit arteries. AHT was induced in C57Bl6 mice with AngII-filled osmotic mini-pumps (4 weeks). Normotensive mice treated with saline-filled osmotic mini-pumps were used for comparison. Voltage-dependent contractions mediated by L-type Ca(2+) channels were studied in vaso-reactive studies in vitro in isolated aortic and femoral arteries by using extracellular K(+) concentration-response (KDR) experiments. In aortic segments, AngII-induced AHT significantly sensitized isometric contractions induced by elevated extracellular K(+) and depolarization. This sensitization was partly prevented by normalizing blood pressure with hydralazine, suggesting that it was caused by AHT rather than by direct AngII effects on aortic smooth muscle cells. The EC50 for extracellular K(+) obtained in vitro correlated significantly with the rise in arterial blood pressure induced by AngII in vivo. The AHT-induced sensitization persisted when aortic segments were exposed to levcromakalim or to inhibitors of basal nitric oxide release. Consistent with these observations, AngII-treatment also sensitized the vaso-relaxing effects of the L-type Ca(2+) channel blocker diltiazem during K(+)-induced contractions. Unlike aorta, AngII-treatment desensitized the isometric contractions to depolarization in femoral arteries pointing to vascular bed specific responses of arteries to hypertension. AHT affects the voltage-dependent L-type Ca(2+) channel-mediated contraction of conduit arteries. This effect may contribute to the decreased vascular compliance in AHT and explain the efficacy of Ca(2+) channel blockers to reduce vascular stiffness and central blood pressure in AHT.

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

PubMed Central

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

2012-01-01

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

Hyperglycemia-induced mouse trophoblast spreading is mediated by reactive oxygen species.

PubMed

Sánchez-Santos, Alejandra; Martínez-Hernández, María G; Contreras-Ramos, Alejandra; Ortega-Camarillo, Clara; Baiza-Gutman, Luis A

2018-04-01

During embryo implantation, the outer layer of the blastocyst interacts with the endometrium giving rise to the development of the trophoblast cell lineage. The cells in this lineage participate in the penetration of endometrium due to their motility and invasive properties. The mechanisms that regulate the differentiation and invasive ability of these cells are essential for the establishment and maintenance of an efficient exchange between maternal and fetal tissues during pregnancy. In this context, hyperglycemia can induce oxidative stress causing alterations in the placenta. This study evaluated the role of reactive oxygen species (ROS) in the actions of high glucose concentration (HG) on trophoblast spreading and the expression of extracellular proteases in cultured mouse conceptuses. Blastocysts from gestational day 4 (GD4) were cultured until GD7 in HAM-F10 medium and further treated for 48 hr with HG (25 mM glucose) from GD7 to GD9. This treatment induced larger trophoblast outgrowths and increased ROS concentration, which was associated with increased expression levels of urokinase-type plasminogen activator (PLAU), plasminogen activator inhibitor 1 (PAI-1), and matrix metalloproteinase 9 (MMP-9). These effects were prevented by treatment with the non-specific antioxidant N-acetylcysteine (NAC) or apocynin, an inhibitor of NADPH oxidase. Our data suggest that the HG-induced trophoblast spreading and the expression of PLAU, PAI-1, and MMP-9 were mediated by the production of ROS via NADPH oxidase activity. Our results shed light on placental alterations in gestational diabetes mellitus. © 2018 Wiley Periodicals, Inc.

Store-Operated Ca2+ Entry (SOCE) Contributes to Normal Skeletal Muscle Contractility in young but not in aged skeletal muscle

PubMed Central

Brotto, Leticia S.; Bougoin, Sylvain; Nosek, Thomas M.; Reid, Michael; Hardin, Brian; Pan, Zui; Ma, Jianjie; Parness, Jerome

2011-01-01

Muscle atrophy alone is insufficient to explain the significant decline in contractile force of skeletal muscle during normal aging. One contributing factor to decreased contractile force in aging skeletal muscle could be compromised excitation-contraction (E-C) coupling, without sufficient available Ca2+ to allow for repetitive muscle contractility, skeletal muscles naturally become weaker. Using biophysical approaches, we previously showed that store-operated Ca2+ entry (SOCE) is compromised in aged skeletal muscle but not in young ones. While important, a missing component from previous studies is whether or not SOCE function correlates with contractile function during aging. Here we test the contribution of extracellular Ca2+ to contractile function of skeletal muscle during aging. First, we demonstrate graded coupling between SR Ca2+ release channel-mediated Ca2+ release and activation of SOCE. Inhibition of SOCE produced significant reduction of contractile force in young skeletal muscle, particularly at high frequency stimulation, and such effects were completely absent in aged skeletal muscle. Our data indicate that SOCE contributes to the normal physiological contractile response of young healthy skeletal muscle and that defective extracellular Ca2+ entry through SOCE contributes to the reduced contractile force characteristic of aged skeletal muscle. PMID:21666285

Store-operated Ca(2+) entry (SOCE) contributes to normal skeletal muscle contractility in young but not in aged skeletal muscle.

PubMed

Thornton, Angela M; Zhao, Xiaoli; Weisleder, Noah; Brotto, Leticia S; Bougoin, Sylvain; Nosek, Thomas M; Reid, Michael; Hardin, Brian; Pan, Zui; Ma, Jianjie; Parness, Jerome; Brotto, Marco

2011-06-01

Muscle atrophy alone is insufficient to explain the significant decline in contractile force of skeletal muscle during normal aging. One contributing factor to decreased contractile force in aging skeletal muscle could be compromised excitation-contraction (E-C) coupling, without sufficient available Ca(2+) to allow for repetitive muscle contractility, skeletal muscles naturally become weaker. Using biophysical approaches, we previously showed that store-operated Ca(2+) entry (SOCE) is compromised in aged skeletal muscle but not in young ones. While important, a missing component from previous studies is whether or not SOCE function correlates with contractile function during aging. Here we test the contribution of extracellular Ca(2+) to contractile function of skeletal muscle during aging. First, we demonstrate graded coupling between SR Ca(2+) release channel-mediated Ca(2+) release and activation of SOCE. Inhibition of SOCE produced significant reduction of contractile force in young skeletal muscle, particularly at high frequency stimulation, and such effects were completely absent in aged skeletal muscle. Our data indicate that SOCE contributes to the normal physiological contractile response of young healthy skeletal muscle and that defective extracellular Ca(2+) entry through SOCE contributes to the reduced contractile force characteristic of aged skeletal muscle.

Signal transduction, plasma membrane calcium movements, and pigment translocation in freshwater shrimp chromatophores.

PubMed

Milograna, Sarah Ribeiro; Bell, Fernanda Tinti; McNamara, John Campbell

2010-11-01

Crustacean color change results from the differential translocation of chromatophore pigments, regulated by neurosecretory peptides like red pigment concentrating hormone (RPCH) that, in the red ovarian chromatophores of the freshwater shrimp Macrobrachium olfersi, triggers pigment aggregation via increased cytosolic cGMP and Ca(2+) of both smooth endoplasmatic reticulum (SER) and extracellular origin. However, Ca(2+) movements during RPCH signaling and the mechanisms that regulate intracellular [Ca(2+)] are enigmatic. We investigate Ca(2+) transporters in the chromatophore plasma membrane and Ca(2+) movements that occur during RPCH signal transduction. Inhibition of the plasma membrane Ca(2+)-ATPase by La(3+) and indirect inhibition of the Na(+)/Ca(2+) exchanger by ouabain induce pigment aggregation, revealing a role for both in Ca(2+) extrusion. Ca(2+) channel blockade by La(3+) or Cd(2+) strongly inhibits slow-phase RPCH-triggered aggregation during which pigments disperse spontaneously. L-type Ca(2+) channel blockade by gabapentin markedly reduces rapid-phase translocation velocity; N- or P/Q-type blockade by ω-conotoxin MVIIC strongly inhibits RPCH-triggered aggregation and reduces velocity, effects revealing RPCH-signaled influx of extracellular Ca(2+). Plasma membrane depolarization, induced by increasing external K(+) from 5 to 50 mM, produces Ca(2+)-dependent pigment aggregation, whereas removal of K(+) from the perfusate causes pigment hyperdispersion, disclosing a clear correlation between membrane depolarization and pigment aggregation; K(+) channel blockade by Ba(2+) also partially inhibits RPCH action. We suggest that, during RPCH signal transduction, Ca(2+) released from the SER, together with K(+) channel closure, causes chromatophore membrane depolarization, leading to the opening of predominantly N- and/or P/Q-type voltage-gated Ca(2+) channels, and a Ca(2+)/cGMP cascade, resulting in pigment aggregation.

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

Isotopic Evidence for Multi-stage Cosmic-ray Exposure Histories of Lunar Meteorites: Long Residence on the Moon and Short Transition to the Earth

NASA Astrophysics Data System (ADS)

Hidaka, Hiroshi; Sakuma, Keisuke; Nishiizumi, Kunihiko; Yoneda, Shigekazu

2017-06-01

It is known that most lunar meteorites have complicated cosmic-ray exposure experiences on the Moon and in space. In this study, cosmic-ray irradiation histories of six lunar meteorites, Dhofar 489, Northwest Africa 032 (NWA 032), NWA 479, NWA 482, NWA 2995, and NWA 5000, were characterized from neutron-captured isotopic shifts of Sm and Gd, and from the abundances of long-lived cosmogenic radionuclides like 10Be, 26Al, 36Cl, and 41Ca. Sm and Gd isotopic data of all of six meteorites show significant isotopic shifts of 149Sm-150Sm and 157Gd-158Gd caused by accumulation of neutron capture reactions due to cosmic-ray irradiation, corresponding to the neutron fluences of (1.3-9.6) × 1016 n cm-2. In particular, very large Sm and Gd isotopic shifts of NWA 482 are over those of a lunar regolith 70002, having the largest isotopic shifts among the Apollo regolith samples, corresponding to cosmic-ray exposure duration over 800 million years in the lunar surface (2π irradiation). Meanwhile, the concentrations of cosmogenic radionuclides for individual six meteorites show the short irradiation time less than one million years as their bodies in space (4π irradiation). Our data also support the results of previous studies, revealing that most of lunar meteorites have long exposure ages at shallow depths on the Moon and short transit times from the Moon to the Earth.

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.

Calcium-dependent molecular fMRI using a magnetic nanosensor.

PubMed

Okada, Satoshi; Bartelle, Benjamin B; Li, Nan; Breton-Provencher, Vincent; Lee, Jiyoung J; Rodriguez, Elisenda; Melican, James; Sur, Mriganka; Jasanoff, Alan

2018-06-01

Calcium ions are ubiquitous signalling molecules in all multicellular organisms, where they mediate diverse aspects of intracellular and extracellular communication over widely varying temporal and spatial scales 1 . Though techniques to map calcium-related activity at a high resolution by optical means are well established, there is currently no reliable method to measure calcium dynamics over large volumes in intact tissue 2 . Here, we address this need by introducing a family of magnetic calcium-responsive nanoparticles (MaCaReNas) that can be detected by magnetic resonance imaging (MRI). MaCaReNas respond within seconds to [Ca 2+ ] changes in the 0.1-1.0 mM range, suitable for monitoring extracellular calcium signalling processes in the brain. We show that the probes permit the repeated detection of brain activation in response to diverse stimuli in vivo. MaCaReNas thus provide a tool for calcium-activity mapping in deep tissue and offer a precedent for the development of further nanoparticle-based sensors for dynamic molecular imaging with MRI.

Calcium-dependent molecular fMRI using a magnetic nanosensor

NASA Astrophysics Data System (ADS)

Okada, Satoshi; Bartelle, Benjamin B.; Li, Nan; Breton-Provencher, Vincent; Lee, Jiyoung J.; Rodriguez, Elisenda; Melican, James; Sur, Mriganka; Jasanoff, Alan

2018-06-01

Calcium ions are ubiquitous signalling molecules in all multicellular organisms, where they mediate diverse aspects of intracellular and extracellular communication over widely varying temporal and spatial scales1. Though techniques to map calcium-related activity at a high resolution by optical means are well established, there is currently no reliable method to measure calcium dynamics over large volumes in intact tissue2. Here, we address this need by introducing a family of magnetic calcium-responsive nanoparticles (MaCaReNas) that can be detected by magnetic resonance imaging (MRI). MaCaReNas respond within seconds to [Ca2+] changes in the 0.1-1.0 mM range, suitable for monitoring extracellular calcium signalling processes in the brain. We show that the probes permit the repeated detection of brain activation in response to diverse stimuli in vivo. MaCaReNas thus provide a tool for calcium-activity mapping in deep tissue and offer a precedent for the development of further nanoparticle-based sensors for dynamic molecular imaging with MRI.

Membrane Potential Dynamics of CA1 Pyramidal Neurons During Hippocampal Ripples in Awake Mice

PubMed Central

Hulse, Brad K.; Moreaux, Laurent C.; Lubenov, Evgueniy V.; Siapas, Athanassios G.

2016-01-01

Ripples are high-frequency oscillations associated with population bursts in area CA1 of the hippocampus that play a prominent role in theories of memory consolidation. While spiking during ripples has been extensively studied, our understanding of the subthreshold behavior of hippocampal neurons during these events remains incomplete. Here, we combine in vivo whole-cell and multisite extracellular recordings to characterize the membrane potential dynamics of identified CA1 pyramidal neurons during ripples. We find that the subthreshold depolarization during ripples is uncorrelated with the net excitatory input to CA1, while the post-ripple hyperpolarization varies proportionately. This clarifies the circuit mechanism keeping most neurons silent during ripples. On a finer time scale, the phase delay between intracellular and extracellular ripple oscillations varies systematically with membrane potential. Such smoothly varying delays are inconsistent with models of intracellular ripple generation involving perisomatic inhibition alone. Instead, they suggest that ripple-frequency excitation leading inhibition shapes intracellular ripple oscillations. PMID:26889811

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

PubMed

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

2007-08-01

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

Structural stability of bismuth-based superconductors under heterovalent substitution

NASA Astrophysics Data System (ADS)

Bonoldi, L.; Calestani, G. L.; Francesconi, M. G.; Salsi, G.; Sparpaglione, M.; Zini, L.

1995-02-01

The stability of the three CuO 2 layers phase of BiPbSrCaCuO superconducting system (BSCCO) with the addition of several rare-earth (RE) oxides is considered. It is shown that if a trivalent (Y, Nd, Gd, Dy, Ho, Er) or tetravalent (Ce) cation is nominally substituted “ab initio” on the Ca site, the higher- Tc phase of this system (the 2223 phase) does not form, at least for dopant molar concentration larger than or equal to 0.032 in the nominal formula of the 2223 phase. If RE oxides are added to a preformed 2223, a solid-state reaction at a temperature of about 840°C takes place giving rise to a substituted (Bi 2- yPb y)Sr 2Ca 1- xRE xCu 2O 8 compound plus other oxides. The synthesis of RE doped 2223 phase was attempted in different ways without success. We argue that this is due to thermodynamic rather than kinetic factors. A possible explanation of 2223 instability under doping in the calcium site with a higher-valence ion is proposed. It highlights the difference with the Bi 2Sr 2CaCu 2O 8 structural stability under the same doping conditions.

Neurophysiological modification of CA1 pyramidal neurons in a transgenic mouse expressing a truncated form of disrupted-in-schizophrenia 1

PubMed Central

Booth, Clair A; Brown, Jonathan T; Randall, Andrew D

2014-01-01

A t(1;11) balanced chromosomal translocation transects the Disc1 gene in a large Scottish family and produces genome-wide linkage to schizophrenia and recurrent major depressive disorder. This study describes our in vitro investigations into neurophysiological function in hippocampal area CA1 of a transgenic mouse (DISC1tr) that expresses a truncated version of DISC1 designed to reproduce aspects of the genetic situation in the Scottish t(1;11) pedigree. We employed both patch-clamp and extracellular recording methods in vitro to compare intrinsic properties and synaptic function and plasticity between DISC1tr animals and wild-type littermates. Patch-clamp analysis of CA1 pyramidal neurons (CA1-PNs) revealed no genotype dependence in multiple subthreshold parameters, including resting potential, input resistance, hyperpolarization-activated ‘sag’ and resonance properties. Suprathreshold stimuli revealed no alteration to action potential (AP) waveform, although the initial rate of AP production was higher in DISC1tr mice. No difference was observed in afterhyperpolarizing potentials following trains of 5–25 APs at 50 Hz. Patch-clamp analysis of synaptic responses in the Schaffer collateral commissural (SC) pathway indicated no genotype-dependence of paired pulse facilitation, excitatory postsynaptic potential summation or AMPA/NMDA ratio. Extracellular recordings also revealed an absence of changes to SC synaptic responses and indicated input–output and short-term plasticity were also unaltered in the temporoammonic (TA) input. However, in DISC1tr mice theta burst-induced long-term potentiation was enhanced in the SC pathway but completely lost in the TA pathway. These data demonstrate that expressing a truncated form of DISC1 affects intrinsic properties of CA1-PNs and produces pathway-specific effects on long-term synaptic plasticity. PMID:24712988

Acetylation Suppresses the Proapoptotic Activity of GD3 Ganglioside

PubMed Central

Malisan, Florence; Franchi, Luigi; Tomassini, Barbara; Ventura, Natascia; Condò, Ivano; Rippo, Maria Rita; Rufini, Alessandra; Liberati, Laura; Nachtigall, Claudia; Kniep, Bernhard; Testi, Roberto

2002-01-01

GD3 synthase is rapidly activated in different cell types after specific apoptotic stimuli. De novo synthesized GD3 accumulates and contributes to the apoptotic program by relocating to mitochondrial membranes and inducing the release of apoptogenic factors. We found that sialic acid acetylation suppresses the proapoptotic activity of GD3. In fact, unlike GD3, 9-O-acetyl-GD3 is completely ineffective in inducing cytochrome c release and caspase-9 activation on isolated mitochondria and fails to induce the collapse of mitochondrial transmembrane potential and cellular apoptosis. Moreover, cells which are resistant to the overexpression of the GD3 synthase, actively convert de novo synthesized GD3 to 9-O-acetyl-GD3. The coexpression of GD3 synthase with a viral 9-O-acetyl esterase, which prevents 9-O-acetyl-GD3 accumulation, reconstitutes GD3 responsiveness and apoptosis. Finally, the expression of the 9-O-acetyl esterase is sufficient to induce apoptosis of glioblastomas which express high levels of 9-O-acetyl-GD3. Thus, sialic acid acetylation critically controls the proapoptotic activity of GD3. PMID:12486096

Tunable optical properties of some rare earth elements-doped mayenite Ca12Al14O33 nanopowders elaborated by oxalate precursor route

NASA Astrophysics Data System (ADS)

Rashad, Mohamed M.; Mostafa, Ahmed G.; Mwakikunga, Bonex W.; Rayan, Diaa A.

2017-01-01

Rare earth (RE) ions-doped mayenite Ca12Al14- x RE x O33 nanopowders (where RE = La and Gd and x = 0-1.0) were synthesized using the oxalate precursor technique. The as-prepared precursors were calcined at 800 °C for 2 h. Obviously, all RE-doped Ca12Al14- x RE x O33 possessed a well-crystalline cubic mayenite phase till RE content of 0.8. The crystallo-chemical aspects including crystallite size, lattice parameters, theoretical X-ray density and bulk density were robustly on RE nature and ratio. The microstructure and the average grain size were significantly influenced by the RE kind and content. The high transparency of Ca12Al14- x RE x O33 over 80% was found to be evinced in the visible wavelength range of 400-800 nm. Besides, the incorporation of RE cation minimized the direct band gap energy from 4.42 eV for pure mayenite to 3.85 and 3.59 eV with x value 1.0 of La3+ and Gd3+ ions. The photoluminescence spectra of pure mayenite nanoparticles showed that the band edge emission ( λ exc = 248 nm) with an intense visible emission band at 360 nm was detected. Otherwise, the band edge emission showed a slight shift toward short wavelength due to the substitution Al3+ by RE3+ ions. Such results open a new avenue for application of mayenite as a good candidate for transparent low-temperature electron conductor for optoelectronics applications.

Protoplasmic Swelling as a Symptom of Freezing Injury in Onion Bulb Cells 1

PubMed Central

Arora, Rajeev; Palta, Jiwan P.

1986-01-01

Freezing injury, in onion bulb tissue, is known to cause enhanced K+ efflux accompanied by a small but significant loss of Ca2+ following incipient freezing injury and swelling of protoplasm during the postthaw secondary injury. The protoplasmic swelling of the cell is thought to be caused by the passive influx of extracellular K+ into the cell followed by water uptake. Using outer epidermal layer of unfrozen onion bulb scales (Allium cepa L. cv Big Red), we were able to stimulate the irreversible freezing injury symptoms, by bathing epidermal cells in 50 millimolar KCl. These symptoms were prevented by adding 20 millimolar CaCl2 to the extracellular KCl solution. Our results provide evidence that loss of cellular Ca2+ plays an important role in the initiation and the progression of freezing injury. Images Fig. 1 PMID:16665083

Calcium Signaling throughout the Toxoplasma gondii Lytic Cycle

PubMed Central

Borges-Pereira, Lucas; Budu, Alexandre; McKnight, Ciara A.; Moore, Christina A.; Vella, Stephen A.; Hortua Triana, Miryam A.; Liu, Jing; Garcia, Celia R. S.; Pace, Douglas A.; Moreno, Silvia N. J.

2015-01-01

Toxoplasma gondii is an obligate intracellular parasite that invades host cells, creating a parasitophorous vacuole where it communicates with the host cell cytosol through the parasitophorous vacuole membrane. The lytic cycle of the parasite starts with its exit from the host cell followed by gliding motility, conoid extrusion, attachment, and invasion of another host cell. Here, we report that Ca2+ oscillations occur in the cytosol of the parasite during egress, gliding, and invasion, which are critical steps of the lytic cycle. Extracellular Ca2+ enhances each one of these processes. We used tachyzoite clonal lines expressing genetically encoded calcium indicators combined with host cells expressing transiently expressed calcium indicators of different colors, and we measured Ca2+ changes in both parasites and host simultaneously during egress. We demonstrated a link between cytosolic Ca2+ oscillations in the host and in the parasite. Our approach also allowed us to measure two new features of motile parasites, which were enhanced by Ca2+ influx. This is the first study showing, in real time, Ca2+ signals preceding egress and their direct link with motility, an essential virulence trait. PMID:26374900

“Gambling disorder in older adults: a cross-cultural perspective”

PubMed Central

Medeiros, Gustavo Costa; Leppink, Eric; Yaemi, Ana; Mariani, Mirella; Tavares, Hermano; Grant, Jon

2015-01-01

INTRODUCTION Gambling Disorder (GD) in older adults is significantly increasing and became an important public health issue in different countries. However, little is known regarding GD in older adults. The prevalence and acceptance of gambling varies among different cultures and this raises the question of how and to what extent culture affects older gamblers. The majority of the important studies regarding GD in older adults have been conducted mainly in Anglo-Saxon cultures and little information is available regarding GD in other cultures. The objective of this paper is to perform the first standardized cross-cultural comparison regarding older adults presenting GD. METHODS The total studied sample involved 170 subjects: 89 from the Brazilian (BR) sample and 81 from the American (US) sample. It consisted of 67 men and 103, women (average age = 64.42, standard deviation = ±3,86). They were evaluated for socio-demographics, gambling behavior variables and psychiatric antecedents. RESULTS Overall, there were significant differences between BR and US older adults gamblers in marital status, onset of gambling activity, onset of GD and urge scores. DISCUSSION This study showed that there are important differences in gambling course, gambling behavior and personal antecedents between two samples of older adults presenting GD from countries with different social-cultural background. It weakens the possibility of generalization of results found in Anglo-Saxon countries to other cultures and reinforces for the need for development of research on GD in older adults outside the Anglo-Saxon culture. PMID:25612901

Gambling disorder in older adults: a cross-cultural perspective.

PubMed

Medeiros, Gustavo Costa; Leppink, Eric; Yaemi, Ana; Mariani, Mirella; Tavares, Hermano; Grant, Jon

2015-04-01

Gambling disorder (GD) in older adults is significantly increasing and became an important public health issue in different countries. However, little is known regarding GD in older adults. The prevalence and acceptance of gambling vary among different cultures and this raises the question of how and to what extent culture affects older gamblers. The majority of the important studies regarding GD in older adults have been conducted mainly in Anglo-Saxon cultures and little information is available regarding GD in other cultures. The objective of this paper is to perform the first standardized cross-cultural comparison regarding older adults presenting GD. The total studied sample involved 170 subjects: 89 from the Brazilian (BR) sample and 81 from the American (US) sample. It consisted of 67 men and 103 women (average age=64.42, standard deviation=±3.86). They were evaluated for socio-demographics, gambling behavior variables and psychiatric antecedents. Overall, there were significant differences between BR and US older adult gamblers in marital status, onset of gambling activity, onset of GD and urge scores. This study showed that there are important differences in gambling course, gambling behavior and personal antecedents between two samples of older adults presenting GD from countries with different social-cultural background. It weakens the possibility of generalization of results found in Anglo-Saxon countries to other cultures and reinforces for the need for development of research on GD in older adults outside the Anglo-Saxon culture. Copyright © 2014 Elsevier Inc. All rights reserved.

Microstructural Anisotropy of Magnetocaloric Gadolinium Cylinders: Effect on the Mechanical Properties of the Material

PubMed Central

Petrovič, Darja Steiner; Šturm, Roman; Naglič, Iztok; Markoli, Boštjan; Pepelnjak, Tomaž

2016-01-01

The development of advanced materials and technologies based on magnetocaloric Gd and its compounds requires an understanding of the dependency of mechanical properties on their underlying microstructure. Therefore, the aim of the study was to characterize microstructural inhomogeneities in the gadolinium that can be used in magnetocaloric refrigeration systems. Microstructures of magnetocaloric gadolinium cylinders were investigated by light microscopy and FE-SEM (Field Emission Scanning Electron Microscopy), EDS (Energy-dispersive X-ray Spectroscopy), and BSE (Back-scattered Electrons) in both the extrusion and the extrusion-transversal directions. XRD (X-ray Diffraction) analyses were performed to reveal the presence of calcium- and fluorine-based compounds. Metallographic characterization showed an oxidized and inhomogeneous microstructure of the cross-sections. The edges and the outer parts of the cylinders were oxidized more intensively on the surfaces directly exposed to the processing tools. Moreover, a significant morphological anisotropy of the non-metallic inclusions was observed. CaF inclusions act as active nucleation sites for internal oxidation. The non-metallic, Ca- and F-containing inclusions can be classified as complex calciumoxyfluorides. The solubility of Er and Yb in the CaF was negligible compared to the Gd matrix and/or the oxide phase. Lower mechanical properties of the material are a consequence of the lower structural integrity due to selective oxidation of surfaces and interfaces. PMID:28773502

Regional convection-enhanced delivery of gadolinium-labeled albumin in the rat hippocampus in vivo.

PubMed

Astary, Garrett W; Kantorovich, Svetlana; Carney, Paul R; Mareci, Thomas H; Sarntinoranont, Malisa

2010-03-15

Convection-enhanced delivery (CED) has emerged as a promising method of targeted drug delivery for treating central nervous system (CNS) disorders, but the influence of brain structure on infusate distribution is unclear. We have utilized this approach to study extracellular transport and distribution of a contrast agent in the hippocampus, a complex structure susceptible to CNS disorders. The magnetic resonance (MR) contrast agent diethylene triamene penta-acetic acid chelated gadolinium-labeled albumin (Gd-albumin), tagged with Evans blue dye, was directly infused (V(i)=5 microl) into the dorsal and ventral hippocampus of seven male Sprague-Dawley rats. The final distribution profile of the contrast agent, a product of CED and limited diffusion, was observed in vivo using high-resolution T1-weighted MR imaging at 11.1T. Dense cell layers, such as the granule cell layer of the dentate gyrus and the pyramidal cell layer of CA1, appeared to be barriers to transport of the tracer. Three-dimensional distribution shape and volume (V(d)) differences, between the dorsal and ventral hippocampus infusions, were determined from the MR images using a semi-automatic segmentation routine (dorsal V(d)=23.4+/-1.8 microl, ventral V(d)=36.4+/-5.1 microl). Finer structural detail of the hippocampus was obtained using a combination of histological analysis and fluorescence imaging. This study demonstrates that CED has the potential to target all regions of the hippocampus and that tracer distribution is influenced by infusion site, underlying structure and circuitry, and extent of backflow. Therefore, CED, combined with high-resolution MR imaging, may be a useful strategy for delivering therapeutics for the treatment of CNS disorders affecting the hippocampus. Published by Elsevier B.V.

Antigenic structure of soluble herpes simplex virus (HSV) glycoprotein D correlates with inhibition of HSV infection.

PubMed Central

Nicola, A V; Peng, C; Lou, H; Cohen, G H; Eisenberg, R J

1997-01-01

Soluble forms of herpes simplex virus (HSV) glycoprotein D (gD) block viral penetration. Likewise, most HSV strains are sensitive to gD-mediated interference by cells expressing gD. The mechanism of both forms of gD-mediated inhibition is thought to be at the receptor level. We analyzed the ability of different forms of soluble, truncated gD (gDt) to inhibit infection by different strains of HSV-1 and HSV-2. Strains that were resistant to gD-mediated interference were also resistant to inhibition by gDt, thereby suggesting a link between these two phenomena. Virion gD was the major viral determinant for resistance to inhibition by gDt. An insertion-deletion mutant, gD-1(delta 290-299t), had an enhanced inhibitory activity against most strains tested. The structure and function of gDt proteins derived from the inhibition-resistant viruses rid1 and ANG were analyzed. gD-1(ridlt) and gD-1(ANGt) had a potent inhibitory effect on plaque formation by wild-type strains of HSV but, surprisingly, little or no effect on their parental strains. As measured by quantitative enzyme-linked immunosorbent assay with a diverse panel of monoclonal antibodies, the antigenic structures of gD-1(rid1t) and gD-1(ANGt) were divergent from that of the wild type yet were similar to each other and to that of gD-1 (delta 290-299t). Thus, three different forms of gD have common antigenic changes that correlate with enhanced inhibitory activity against HSV. We conclude that inhibition of HSV infectivity by soluble gD is influenced by the antigenic conformation of the blocking gDt as well as the form of gD in the target virus. PMID:9060653

Adrenergic-agonist-induced Ca2+ fluxes in rat parotid cells are not Na+-dependent.

PubMed Central

Helman, J; Roth, G S; Baum, B J

1985-01-01

We investigated the hypothesis that extracellular Na+ is required for the rapid mobilization of Ca2+ by rat parotid cells after adrenergic stimulation. When Na+ salts in the media were osmotically replaced with either choline chloride (+atropine) or sucrose, efflux of 45Ca2+ from preloaded cells, caused by 10 microM-(-)-adrenaline, was unchanged. Similarly adrenaline stimulated 45Ca2+ uptake into cells under nonsteady-state conditions in the presence or absence of Na+. Monensin, a Na+ ionophore, was able to elicit a modest increase in 45Ca2+ efflux, compared with controls. Studies of net 45Ca2+ flux, performed under near-steady-state conditions, showed that adrenaline caused net 45Ca2+ accumulation, whereas monensin caused net 45Ca2+ release. The effect of monensin required the presence of Na+ in the incubation medium. Both 1 mM-LaCl3 and 0.1 mM-D-600 prevented adrenaline-stimulated 45Ca2+ uptake into cells, but had no effect on monensin-induced changes. We conclude that (1) the rapid mobilization of Ca2+ by adrenergic agonists seen in rat parotid cells does not require a Na+out greater than Na+in gradient and (2) the nature of the monensin effect is quite different from the adrenergic-agonist-induced response. PMID:2413840

Extracellular cAMP activates molecular signalling pathways associated with sperm capacitation in bovines.

PubMed

Alonso, Carlos Agustín I; Osycka-Salut, Claudia E; Castellano, Luciana; Cesari, Andreína; Di Siervi, Nicolás; Mutto, Adrián; Johannisson, Anders; Morrell, Jane M; Davio, Carlos; Perez-Martinez, Silvina

2017-08-01

Is extracellular cAMP involved in the regulation of signalling pathways in bovine sperm capacitation? Extracellular cAMP induces sperm capacitation through the activation of different signalling pathways that involve phospholipase C (PLC), PKC/ERK1-2 signalling and an increase in sperm Ca2+ levels, as well as soluble AC and cAMP/protein kinase A (PKA) signalling. In order to fertilize the oocyte, ejaculated spermatozoa must undergo a series of changes in the female reproductive tract, known as capacitation. This correlates with a number of membrane and metabolic modifications that include an increased influx of bicarbonate and Ca2+, activation of a soluble adenylyl cyclase (sAC) to produce cAMP, PKA activation, protein tyrosine phosphorylation and the development of hyperactivated motility. We previously reported that cAMP efflux by Multidrug Resistance Protein 4 (MRP4) occurs during sperm capacitation and the pharmacological blockade of this inhibits the process. Moreover, the supplementation of incubation media with cAMP abolishes the inhibition and leads to sperm capacitation, suggesting that extracellular cAMP regulates crucial signalling cascades involved in this process. Bovine sperm were selected by the wool glass column method, and washed by centrifugation in BSA-Free Tyrode's Albumin Lactate Pyruvate (sp-TALP). Pellets were resuspended then diluted for each treatment. For in vitro capacitation, 10 to 15 × 106 SPZ/ml were incubated in 0.3% BSA sp-TALP at 38.5°C for 45 min under different experimental conditions. To evaluate the role of extracellular cAMP on different events associated with sperm capacitation, 10 nM cAMP was added to the incubation medium as well as different inhibitors of enzymes associated with signalling transduction pathways: U73122 (PLC inhibitor, 10 μM), Gö6983 (PKC inhibitor, 10 μM), PD98059 (ERK-1/2 inhibitor, 30 μM), H89 and KT (PKA inhibitors, 50 μM and 100 nM, respectively), KH7 (sAC inhibitor, 10 μM), BAPTA-AM (intracellular Ca2+ chelator, 50 μM), EGTA (10 μM) and Probenecid (MRPs general inhibitor, 500 μM). In addition, assays for binding to oviductal epithelial cells and IVF were carried out to test the effect of cAMP compared with other known capacitant agents such as heparin (60 μg/ml) and bicarbonate (40 mM). Straws of frozen bovine semen (20-25 × 106 spermatozoa/ml) were kindly provided by Las Lilas, CIALE and CIAVT Artificial Insemination Centers. The methods used in this work include western blot, immunohistochemistry, flow cytometry, computer-assisted semen analysis, live imaging of Ca2+ and fluorescence scanning. At least three independent assays with bull samples of proven fertility were carried. In the present study, we elucidate the molecular events induced by extracellular cAMP. Our results showed that external cAMP induces sperm capacitation, depending upon the action of PLC. Downstream, this enzyme increased ERK1-2 activation through PKC and elicited a rise in sperm Ca2+ levels (P < 0.01). Moreover, extracellular cAMP-induced capacitation also depended on the activity of sAC and PKA, and increased tyrosine phosphorylation, indicating that the nucleotide exerts a broad range of responses. In addition, extracellular cAMP-induced sperm hyperactivation and concomitantly increased the proportion of spermatozoa with high mitochondrial activity (P < 0.01). Finally, cAMP increased the in vitro fertilization rate compared to control conditions (P < 0.001). None. This is an in vitro study performed with bovine cryopreserved spermatozoa. Studies in other species and with fresh samples are needed to extrapolate these data. These findings strongly suggest an important role of extracellular cAMP in the regulation of the signalling pathways involved in the acquisition of bull sperm fertilizing capability. The data presented here indicate that not only a rise, but also a regulation of cAMP levels is necessary to ensure sperm fertilizing ability. Thus, exclusion of the nucleotide to the extracellular space might be essential to guarantee the achievement of a cAMP tone, needed for all capacitation-associated events to take place. Moreover, the ability of cAMP to trigger such broad and complex signalling events allows us to hypothesize that cAMP is a self-produced autocrine/paracrine factor, and supports the emerging paradigm that spermatozoa do not compete but, in fact, communicate with each other. A precise understanding of the functional competence of mammalian spermatozoa is essential to generate clinical advances in the treatment of infertility and the development of novel contraceptive strategies. This work was supported by Consejo Nacional de Investigaciones Científicas y Técnicas [PIP0 496 to S.P.-M.], Agencia Nacional de Promoción Científica y Tecológica [PICT 2012-1195 and PICT2014-2325 to S.P.-M., and PICT 2013-2050 to C.D.], Boehringer Ingelheim Funds, and the Swedish Farmers Foundation [SLF-H13300339 to J.M.]. The authors declare there are no conflicts of interests. © The Author 2017. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved. For Permissions, please email: journals.permissions@oup.com

Deduction of a calcium ion circuit affecting rooster sperm in vitro.

PubMed

Froman, D P

2016-08-01

Four premises for rooster sperm preservation were outlined previously. Understanding mitochondrial Ca cycling in terms of whole-cell Ca flux was one premise. The present work tested the hypothesis that sperm mitochondria can be damaged by intracellular as well as extracellular Ca. Sperm were washed by centrifugation through 12% (wt/vol) Sperm were washed by centrifugation through 12%(at/vol) Accudenz to procure sperm at a physiological concentration within a chemically-defined suspension. Five solutions were tested. Each solution contained 30 m glucose, and had an osmolality of 320 mmol/kg and a pH of 7.4. Washed sperm were diluted to 2.0 × 10 sperm/mL. Each replicate sperm suspension was cooled to 10°C. Sperm mobility was measured after 1, 2, 4, 8, 12, and 24 h. Data were plotted as a function of time in each experiment. Function type was confirmed by lack of fit analysis. A parabola with a maximum at 3.7 h was observed when sperm were suspended in 205 m taurine buffered with 50 m-tris[hydroxyl-methyl]methyl-2-amino-ethanesulfonic acid (TES). This effect was attributed to a Ca flux from the nuclear envelope into mitochondria. An exponential decay was observed when TES-buffered taurine contained 2 m Ca. This effect was attributed to mitochondrial Ca overload induced by uptake of extracellular Ca. Exponential decay also was observed when TES-buffered taurine contained a Ca chelator. This effect was attributed to a Ca flux from the nuclear envelope through mitochondria and then into an extracellular Ca sink. This possibility was supported by the response of sperm to thapsigargin. Specifically, inhibition of sarcoendoplasmic reticulum Ca-ATPase compromised sperm mobility relative to a buffer control. Finally, a 60 m phosphate buffer containing 2 m citrate yielded a linear relationship in contrast to the TES-buffered solutions tested. Sperm mobility after 24 h of storage in the phosphate buffer was 92% of that observed for prewashed sperm. The linear response was attributed to weak chelators providing resistance within a Ca circuit and thereby preventing mitochondrial Ca overload. Fertility, however, was compromised when hens were inseminated with mobile sperm recovered after either 8 or 24 h of storage at 10°C. In conclusion, sperm cell Ca homeostasis was proven to be critical for maintaining sperm mobility in vitro, but mitochondrial Ca uptake is not the sole phenomenon that compromises sperm function during in vitro storage.

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

UVB-irradiated keratinocytes induce melanoma-associated ganglioside GD3 synthase gene in melanocytes via secretion of tumor necrosis factor α and interleukin 6

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

Miyata, Maiko; Department of Biochemistry II, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya 466-0065; Ichihara, Masatoshi

Highlights: • Melanocytes showed low ST8SIA1 and high B3GALT4 levels in contrast with melanomas. • Direct UVB irradiation of melanocytes did not induce ganglioside synthase genes. • Culture supernatants of UVB-irradiated keratinocytes induced ST8SIA1 in melanocytes. • TNFα and IL-6 secreted from keratinocytes enhanced ST8SIA1 expression in melanocytes. • Inflammatory cytokines induced melanoma-related ST8SIA1 in melanocytes. - Abstract: Although expression of gangliosides and their synthetic enzyme genes in malignant melanomas has been well studied, that in normal melanocytes has been scarcely analyzed. In particular, changes in expression levels of glycosyltransferase genes responsible for ganglioside synthesis during evolution of melanomas frommore » melanocytes are very important to understand roles of gangliosides in melanomas. Here, expression of glycosyltransferase genes related to the ganglioside synthesis was analyzed using RNAs from cultured melanocytes and melanoma cell lines. Quantitative RT-PCR revealed that melanomas expressed high levels of mRNA of GD3 synthase and GM2/GD2 synthase genes and low levels of GM1/GD1b synthase genes compared with melanocytes. As a representative exogenous stimulation, effects of ultraviolet B (UVB) on the expression levels of 3 major ganglioside synthase genes in melanocytes were analyzed. Although direct UVB irradiation of melanocytes caused no marked changes, culture supernatants of UVB-irradiated keratinocytes (HaCaT cells) induced definite up-regulation of GD3 synthase and GM2/GD2 synthase genes. Detailed examination of the supernatants revealed that inflammatory cytokines such as TNFα and IL-6 enhanced GD3 synthase gene expression. These results suggest that inflammatory cytokines secreted from UVB-irradiated keratinocytes induced melanoma-associated ganglioside synthase genes, proposing roles of skin microenvironment in the promotion of melanoma-like ganglioside profiles in melanocytes.« less

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

The role of Na-Ca exchange current in the cardiac action potential.

PubMed

Janvier, N C; Boyett, M R

1996-07-01

Since 1981, when Mullins published his provocative book proposing that the Na-Ca exchanger is electrogenic, it has been shown, first by computer simulation by Noble and later by experiment by various investigators, that inward iNaCa triggered by the Ca2+ transient is responsible for the low plateau of the atrial action potential and contributes to the high plateau of the ventricular action potential. Reduction or complete block of inward iNaCa by buffering intracellular Ca2+ with EGTA or BAPTA, by blocking SR Ca2+ release or by substituting extracellular Na+ with Li+ can result in a shortening of the action potential. The effect of block of outward iNaCa or complete block of both inward and outward iNaCa on the action potential has not been investigated experimentally, because of the lack of a suitable blocker, and remains a goal for the future. An increase in the intracellular Na+ concentration (after the application of cardiac glycoside or an increase in heart rate) or an increase in extracellular Ca2+ are believed to lead to an outward shift in iNaCa at plateau potentials and a shortening of the action potential. Changes in the Ca2+ transient are expected to result in changes in inward iNaCa and thus the action potential. This may explain the shortening of the premature action potential as well as the prolongation of the action potential when a muscle is allowed to shorten during the action potential. Inward iNaCa may play an important role in both normal and abnormal pacemaker activity in the heart.

Faster flux of neurotransmitter glutamate during seizure — Evidence from 13C-enrichment of extracellular glutamate in kainate rat model

PubMed Central

2017-01-01

The objective is to examine how the flux of neurotransmitter glutamate from neurons to the extracellular fluid, as measured by the rate of 13C enrichment of extracellular glutamate (GLUECF), changes in response to seizures in the kainate-induced rat model of temporal-lobe epilepsy. Following unilateral intrahippocampal injection of kainate, GLUECF was collected by microdialysis from the CA1/CA3 region of awake rats, in combination with EEG recording of chronic-phase recurrent seizures and intravenous infusion of [2,5-13C]glucose. The 13C enrichment of GLUECF C5 at ~ 10 picomol level was measured by gas-chromatography mass-spectrometry. The rate of 13C enrichment, expressed as the increase of the fractional enrichment/min, was 0.0029 ± 0.0001/min in frequently seizing rats (n = 4); this was significantly higher (p < 0.01) than in the control (0.00167 ± 0.0001/min; n = 6) or in rats with infrequent seizures (0.00172 ± 0.0001/min; n = 6). This result strongly suggests that the flux of the excitatory neurotransmitter from neurons to the extracellular fluid is significantly increased by frequent seizures. The extracellular [12C + 13C]glutamate concentration increased progressively in frequently seizing rats. Taken together, these results strongly suggest that the observed seizure-induced high flux of glutamate overstimulated glutamate receptors, which triggered a chain reaction of excitation in the CA3 recurrent glutamatergic networks. The rate of 13C enrichment of extracellular glutamine (GLNECF) at C5 was 0.00299 ± 0.00027/min in frequently seizing rats, which was higher (p < 0.05) than in controls (0.00227 ± 0.00008/min). For the first time in vivo, this study examined the effects of epileptic seizures on fluxes of the neurotransmitter glutamate and its precursor glutamine in the extracellular fluid of the hippocampus. The advantages, limitations and the potential for improvement of this approach for pre-clinical and clinical studies of temporal-lobe epilepsy are discussed. PMID:28403176

Color Discrimination in Patients with Gaucher Disease and Parkinson Disease.

PubMed

Simon-Tov, Shlomi; Dinur, Tama; Giladi, Nir; Bar-Shira, Anat; Zelis, Mayaan; Zimran, Ari; Elstein, Deborah

2015-01-01

Poor color discrimination among patients with Parkinson disease (PD) has long been recognized. It has been shown that carrying one or two mutations in the β-glucocerebrosidase gene (GBA) for the autosomal disease Gaucher disease (GD), as based initially on clinical evidence, is a genetic risk factor for early-onset PD. The purpose of this study was to assess color discrimination in patients with one or two GBA mutations relative to healthy controls to ascertain whether this function is affected when persons with GD or even one GBA mutation develop PD. The Farnsworth-Munsell 100 hue test (FMHT) was evaluated among patients with GD+PD compared to patients with GD only, obligate GBA carriers with and without PD, patients with PD only, and healthy controls. FMHT outcome include computer-generated TES (Total Error Score) and values recommended by Vingrys & King-Smith. Six groups of 10 persons were tested. Significant differences were seen for male GD+PD and for age in PD. The highest mean TES was in the PD only group, the lowest in the GD only group. There was a significant difference because of PD in groups with GD and GBA carriers. GD+PD means were between GD only and PD only mean scores. These findings confirm that PD impacts color discrimination, more in males with GD+PD but nonetheless, GD+PD patients (but not GBA carriers) had better scores than PD only patients.

Bupropion Shows Different Effects on Brain Functional Connectivity in Patients With Internet-Based Gambling Disorder and Internet Gaming Disorder.

PubMed

Bae, Sujin; Hong, Ji Sun; Kim, Sun Mi; Han, Doug Hyun

2018-01-01

Internet gaming disorder (IGD) and gambling disorder (GD) share similar clinical characteristics but show different brain functional connectivity patterns. Bupropion is known to be effective for the treatment of patients with IGD and GD. We hypothesized that bupropion may be effective for the treatment of Internet-based gambling disorder (ibGD) and IGD and that the connections between the default mode network (DMN) and cognitive control network (CCN) would be different between ibGD and IGD patients after 12 weeks of bupropion treatment. 16 patients with IGD, 15 patients with ibGD, and 15 healthy subjects were recruited in this study. At baseline and after 12 weeks of bupropion treatment, the clinical symptoms of patients with IGD or ibGD were assessed, and brain activity was evaluated using resting state functional magnetic resonance imaging. After the 12-week bupropion treatment, clinical symptoms, including the severity of IGD or GD, depressive symptoms, attention, and impulsivity improved in both groups. In the IGD group, the functional connectivity (FC) within the posterior DMN as well as the FC between the DMN and the CCN decreased following treatment. Moreover, the FC within the DMN in the IGD group was positively correlated with changes in Young Internet Addiction Scale scores after the bupropion treatment period. In the ibGD group, the FC within the posterior DMN decreased while the FC within the CCN increased after the bupropion treatment period. Moreover, the FC within the CCN in the ibGD group was significantly greater than that in the IGD group. Bupropion was effective in improving clinical symptoms in patients with IGD and ibGD. However, there were differences in the pharmacodynamics between the two groups. After 12 weeks of bupropion treatment, the FC within the DMN as well as between the DMN and CCN decreased in patients with IGD, whereas the FC within the CCN increased in patients with ibGD.

Alpha 2-adrenergic receptor stimulation of phospholipase A2 and of adenylate cyclase in transfected Chinese hamster ovary cells is mediated by different mechanisms

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

Jones, S.B.; Halenda, S.P.; Bylund, D.B.

1991-02-01

The effect of alpha 2-adrenergic receptor activation on adenylate cyclase activity in Chinese hamster ovary cells stably transfected with the alpha 2A-adrenergic receptor gene is biphasic. At lower concentrations of epinephrine forskolin-stimulated cyclic AMP production is inhibited, but at higher concentrations the inhibition is reversed. Both of these effects are blocked by the alpha 2 antagonist yohimbine but not by the alpha 1 antagonist prazosin. Pretreatment with pertussis toxin attenuates inhibition at lower concentrations of epinephrine and greatly potentiates forskolin-stimulated cyclic AMP production at higher concentrations of epinephrine. alpha 2-Adrenergic receptor stimulation also causes arachidonic acid mobilization, presumably via phospholipasemore » A2. This effect is blocked by yohimbine, quinacrine, removal of extracellular Ca2+, and pretreatment with pertussis toxin. Quinacrine and removal of extracellular Ca2+, in contrast, have no effect on the enhanced forskolin-stimulated cyclic AMP production. Thus, it appears that the alpha 2-adrenergic receptor in these cells can simultaneously activate distinct signal transduction systems; inhibition of adenylate cyclase and stimulation of phospholipase A2, both via G1, and potentiation of cyclic AMP production by a different (pertussis toxin-insensitive) mechanism.« less

Increased Resting Intracellular Calcium Modulates NF-κB-dependent Inducible Nitric-oxide Synthase Gene Expression in Dystrophic mdx Skeletal Myotubes*

PubMed Central

Altamirano, Francisco; López, Jose R.; Henríquez, Carlos; Molinski, Tadeusz; Allen, Paul D.; Jaimovich, Enrique

2012-01-01

Duchenne muscular dystrophy (DMD) is a genetic disorder caused by dystrophin mutations, characterized by chronic inflammation and severe muscle wasting. Dystrophic muscles exhibit activated immune cell infiltrates, up-regulated inflammatory gene expression, and increased NF-κB activity, but the contribution of the skeletal muscle cell to this process has been unclear. The aim of this work was to study the pathways that contribute to the increased resting calcium ([Ca2+]rest) observed in mdx myotubes and its possible link with up-regulation of NF-κB and pro-inflammatory gene expression in dystrophic muscle cells. [Ca2+]rest was higher in mdx than in WT myotubes (308 ± 6 versus 113 ± 2 nm, p < 0.001). In mdx myotubes, both the inhibition of Ca2+ entry (low Ca2+ solution, Ca2+-free solution, and Gd3+) and blockade of either ryanodine receptors or inositol 1,4,5-trisphosphate receptors reduced [Ca2+]rest. Basal activity of NF-κB was significantly up-regulated in mdx versus WT myotubes. There was an increased transcriptional activity and p65 nuclear localization, which could be reversed when [Ca2+]rest was reduced. Levels of mRNA for TNFα, IL-1β, and IL-6 were similar in WT and mdx myotubes, whereas inducible nitric-oxide synthase (iNOS) expression was increased 5-fold. Reducing [Ca2+]rest using different strategies reduced iNOS gene expression presumably as a result of decreased activation of NF-κB. We propose that NF-κB, modulated by increased [Ca2+]rest, is constitutively active in mdx myotubes, and this mechanism can account for iNOS overexpression and the increase in reactive nitrogen species that promote damage in dystrophic skeletal muscle cells. PMID:22549782

Monomeric and polymeric forms of ependymin: a brain extracellular glycoprotein implicated in memory consolidation processes.

PubMed

Shashoua, V E

1988-07-01

Ependymin, a brain extracellular glycoprotein that appears to be implicated in neural circuit modifications associated with the process of memory consolidation, can rapidly polymerize into fibrous aggregates when the Ca2+ concentration in solution is reduced by the addition of EGTA or by dialysis. Such aggregates, once formed, could not be redissolved in boiling 1% SDS in 6 M urea, acetic acid, saturated aqueous potassium thiocyanate, and trifluoroacetic acid. They were, however, soluble in formic acid. Investigations of the immunological properties of ependymin indicated that various monomers, oligomers and polymers of the molecule with differing carbohydrate contents can be obtained. The polymerization properties of the ependymins may play an important role in their functions in memory consolidation mechanisms.

[Application of T grain technique to the diagnosis of lung disease and analysis of its image quality].

PubMed

Liu, Xin-jun; Liu, Pei-cheng; Cai, Pei; Zhang, Dun; Yao, Shi-sheng

2003-06-01

To compare the image quality of T grain green sensitive film (TML-1) and Lanex Gd(2)O(2)S rare earth intensifying screen with that of XK-1 blue sensitive film and calcium tungstate (CaWO(4)) intensifying screen, and to study the application of T grain technic to the diagnosis of lung diseases. 160 coal miners were randomly selected to take both TML-1 and XK-1 chest film of high kV radiographs at the same time. Silver halide granule, fluorescence of intensifying screen, radiographic parameters, the density at different points in the lung and chest radiographs were observed. Silver grains in TML-1 film were more homogeneous in distribution than in XK-1 film. Luminous intensity of Lanex Gd(2)O(2)S rare earth intensifying screen was brighter than CaWO(4) intensifying screen in the same exposure. The exposure doses of TML-1 film was reduced to one third of XK-1 film. The density of chest radiographs was 0.24 to 2.74 in TML-1 film, and 0.30 to 2.60 in XK-1 film. There were greater exposure latitude and more informations in TML-1 film. By apertured-disc observation, the fine structure of lung in TML-1 film was clearer than in XK-1 film, the shape was more concrete and reliable, visualizability was stronger. T grain technique may obviously improve the clearness and resolution of image, and enhance the transmission of information, as well as increase the diagnostic informations.

Does diffusion-weighted imaging improve therapy response evaluation in patients with hepatocellular carcinoma after radioembolization? comparison of MRI using Gd-EOB-DTPA with and without DWI.

PubMed

Schelhorn, Juliane; Best, Jan; Reinboldt, Marcus P; Dechêne, Alexander; Gerken, Guido; Ruhlmann, Marcus; Lauenstein, Thomas C; Antoch, Gerald; Kinner, Sonja

2015-09-01

To investigate whether additional diffusion-weighted imaging (DWI) improves therapy response evaluation by Gd-EOB magnetic resonance imaging (MRI) in hepatocellular carcinoma (HCC) after radioembolization. Fifty patients with radioembolization for HCC underwent gadobutrol and Gd-EOB MRI with DWI prior to and 30, 90, and 180 days after radioembolization. A combination of gadobutrol MRI, alpha-fetoprotein, and imaging follow-up served as the reference standard. Two radiologists reviewed Gd-EOB alone (Gd-EOB), DWI alone (DWI), and the combination of both (Gd-EOB+DWI) separately and in consensus using a 4-point-scale: 1 = definitely no tumor progression (TP), 2 = probably no TP, 3 = probably TP, 4 = definitely TP. Receiver operating characteristic (ROC) and kappa analysis were performed. Kappa values for Gd-EOB, DWI, and Gd-EOB+DWI ranged between 0.712 and 0.892 (P < 0.001). 30 days after radioembolization three out of 38 patients showed TP, which was missed by DWI in one case. No significant area under the curve (AUC) difference between Gd-EOB (1.0, P = 0.004), DWI (0.881, P = 0.030), and Gd-EOB+DWI (1.0, P = 0.004) was found (P = 0.320). 90 days after radioembolization six out of 28 patients showed TP, which was detected in one patient only by DWI and Gd-EOB+DWI. The AUC did not differ significantly (P = 0.319) between Gd-EOB (0.890, P = 0.004), DWI (1.0, P < 0.001), and Gd-EOB+DWI (1.0, P < 0.001). 180 days after radioembolization five patients showed TP, which in one case was missed by DWI. The AUC did not differ significantly (P1 = 0.322, P2 = 0.369, P3 = 0.350) between Gd-EOB (1.0, P = 0.003), DWI (0.913, P = 0.016), and Gd-EOB+DWI (0.963, P = 0.007). Additional DWI does not substantially improve therapy response evaluation by Gd-EOB MRI in HCC after radioembolization but proved helpful in single cases. © 2014 Wiley Periodicals, Inc.

Different receptors binding to distinct interfaces on herpes simplex virus gD can trigger events leading to cell fusion and viral entry

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

Spear, Patricia G.; Manoj, Sharmila; Yoon, Miri

2006-01-05

One of the herpes simplex virus envelope glycoproteins, designated gD, is the principal determinant of cell recognition for viral entry. Other viral glycoproteins, gB, gH and gL, cooperate with gD to mediate the membrane fusion that is required for viral entry and cell fusion. Membrane fusion is triggered by the binding of gD to one of its receptors. These receptors belong to three different classes of cell surface molecules. This review summarizes recent findings on the structure and function of gD. The results presented indicate that gD may assume more than one conformation, one in the absence of receptor, anothermore » when gD is bound to the herpesvirus entry mediator, a member of the TNF receptor family, and a third when gD is bound to nectin-1, a cell adhesion molecule in the immunoglobulin superfamily. Finally, information and ideas are presented about a membrane-proximal region of gD that is required for membrane fusion, but not for receptor binding, and that may have a role in activating the fusogenic activity of gB, gH and gL.« less

[Diffusion of fluorescent and magnetic molecular probes in brain interstitial space].

PubMed

Li, Huai-ye; Zhao, Yue; Zuo, Long; Fu, Yu; Li, Nan; Yuan, Lan; Zhang, Shu-jia; Han, Hong-bin

2015-08-18

To compare the diffusion properties of fluorescent probes dextran-tetramethylrhodamine (DT) and lucifer yellow CH (LY) and magnetic probe gadolinium-diethylene triamine pentaacetic acid (Gd-DTPA) in porous media and to screen out a suitable fluorescent probe for optical imaging of brain interstitial space (ISS). Agarose gels sample were divided into DT group, LY group and Gd-DTPA group, and the corresponding molecular probes were imported in each group. The dynamic diffusions of DT and LY in agarose gels at different time points (15, 30, 45, 60, 90, and 120 min) were scanned with laser scanning confocal microscope, the dynamic diffusion of Gd-DTPA was imaged with magnetic resonance imaging. The average diffusion speed of LY were demonstrated to be consistent with those of Gd-DTPA. The LY was introduced into caudate putamen of 18 rats, respectively, the diffusion of LY in the sequential slices of rat brain at different time points (0.5, 1, 2, 3, 7, 11 h) were scanned, and the results were compared with those of rats' brain with Gd-DTPA imported and imaged in vivo with magnetic resonance imaging. The diffusions of the three probes were isotropic in the agarose gels, and the average diffusion speeds of DT, LY and Gd-DTPA were: (0.07±0.02)×10(-2) mm2/s, (1.54±0.47)×10(-2) mm2/s, (1.45±0.50)×10(-2) mm2/s, respectively. The speed of DT was more slower than both LY and Gd-DTPA (ANOVA, F=367.15, P<0.001; Post-Hoc LSD, P<0.001), and there was no significant difference between the speeds of LY and Gd-DTPA (Post-Hoc LSD, P=0.091). The variation tendency of diffusion area of DT was different with both that of LY and that of Gd-DTPA (Bonferroni correction, α=0.0125, P<0.001), and there was no significant difference between LY and Gd-DTPA (Bonferroni correction, α=0.0125, P=0.203), in analysis by repeated measures data of ANOVA. The diffusions of LY and Gd-DTPA were anisotropy in rat caudate putamen,and the average diffusion speeds of LY and Gd-DTPA were: (1.03±0.29)×10(-3) mm2/s, (0.81±0.27)×10(-3) mm2/s, respectively, no significant difference was demonstrated (t=0.759, P=0.490); half-time of single intensity of LY and Gd-DTPA was (2.58±0.04) h, (2.46±0.10) h, respectively, no significant difference was found (t=2.025, P=0.113). The diffusion area ratios between LY and Gd-DTPA in rat caudate putamen was not statistically different at hours 0.5, 1, 2, 3 and 7 (t=2.249, P=0.088; t=2.582, P=0.061; t=1.966, P=0.121; t=0.132, P=0.674; t=0.032, P=0.976), while, a slightly difference was found at 11 h (t=2.917, P=0.043,in analysis by t test). LY present the same diffusion property with Gd-DTPA in porous media witch including agarose gels and live rat brain tissue, indicates that LY is a suitable fluorescent probe for optical imaging of brain ISS, and it can be used for microscopic, macro and in vitro measure of brain ISS.

Fatty acid synthase as a tumor marker: its extracellular expression in human breast cancer.

PubMed

Wang, Young Y; Kuhajda, Francis P; Li, Jinong; Finch, Teia T; Cheng, Paul; Koh, Clare; Li, Tianwei; Sokoll, Lori J; Chan, Daniel W

2004-07-01

Overexpression of fatty acid synthase (FAS EC 2.3.1.85) is associated with certain cancers and therefore is a putative tumor marker. The presence of FAS in patients with breast, prostate, colon, ovarian, and other cancers has been reported. The mechanism of FAS overexpression in malignancies remains unknown. Here, we show that FAS is released into the extracellular space in cancer cells. The extracellular FAS are present in various immunoreactive forms, and show different expression patterns in various cancer cells. In serum of breast cancer patients, the FAS is a small molecule similar to the form in breast cancer cell lysate but not conditioned medium of cultured cells. The extracellular expression of FAS in breast cancer cells is time dependent and may be hormone independent. These results indicate that the FAS are an ordered cellular response of a living cell and actively exclude excess intracellular FAS molecules from the cell. This phenomenon is up-regulated in breast and may be in other cancer cells as well. Significant elevation of FAS was detected in serum of breast cancer patients compared to healthy subjects. In comparison with CA27.29, no correlation between these two tumor markers was found. Thus, the extracellular FAS may serve as a potential diagnostic and prognostic marker.

In vitro study of novel gadolinium-loaded liposomes guided by GBI-10 aptamer for promising tumor targeting and tumor diagnosis by magnetic resonance imaging

PubMed Central

Gu, Meng-Jie; Li, Kun-Feng; Zhang, Lan-Xin; Wang, Huan; Liu, Li-Si; Zheng, Zhuo-Zhao; Han, Nan-Yin; Yang, Zhen-Jun; Fan, Tian-Yuan

2015-01-01

Novel gadolinium-loaded liposomes guided by GBI-10 aptamer were developed and evaluated in vitro to enhance magnetic resonance imaging (MRI) diagnosis of tumor. Nontargeted gadolinium-loaded liposomes were achieved by incorporating amphipathic material, Gd (III) [N,N-bis-stearylamidomethyl-N′-amidomethyl] diethylenetriamine tetraacetic acid, into the liposome membrane using lipid film hydration method. GBI-10, as the targeting ligand, was then conjugated onto the liposome surface to get GBI-10-targeted gadolinium-loaded liposomes (GTLs). Both nontargeted gadolinium-loaded liposomes and GTLs displayed good dispersion stability, optimal size, and zeta potential for tumor targeting, as well as favorable imaging properties with enhanced relaxivity compared with a commercial MRI contrast agent (CA), gadopentetate dimeglumine. The use of GBI-10 aptamer in this liposomal system was intended to result in increased accumulation of gadolinium at the periphery of C6 glioma cells, where the targeting extracellular matrix protein tenascin-C is overexpressed. Increased cellular binding of GTLs to C6 cells was confirmed by confocal microscopy, flow cytometry, and MRI, demonstrating the promise of this novel delivery system as a carrier of MRI contrast agent for the diagnosis of tumor. These studies provide a new strategy furthering the development of nanomedicine for both diagnosis and therapy of tumor. PMID:26316749

Hydrogen peroxide generation by the pepper extracellular peroxidase CaPO2 activates local and systemic cell death and defense response to bacterial pathogens.

PubMed

Choi, Hyong Woo; Kim, Young Jin; Lee, Sung Chul; Hong, Jeum Kyu; Hwang, Byung Kook

2007-11-01

Reactive oxygen species (ROS) are responsible for mediating cellular defense responses in plants. Controversy has existed over the origin of ROS in plant defense. We have isolated a novel extracellular peroxidase gene, CaPO2, from pepper (Capsicum annuum). Local or systemic expression of CaPO2 is induced in pepper by avirulent Xanthomonas campestris pv vesicatoria (Xcv) infection. We examined the function of the CaPO2 gene in plant defense using the virus-induced gene silencing technique and gain-of-function transgenic plants. CaPO2-silenced pepper plants were highly susceptible to Xcv infection. Virus-induced gene silencing of the CaPO2 gene also compromised hydrogen peroxide (H(2)O(2)) accumulation and hypersensitive cell death in leaves, both locally and systemically, during avirulent Xcv infection. In contrast, overexpression of CaPO2 in Arabidopsis (Arabidopsis thaliana) conferred enhanced disease resistance accompanied by cell death, H(2)O(2) accumulation, and PR gene induction. In CaPO2-overexpression Arabidopsis leaves infected by Pseudomonas syringae pv tomato, H(2)O(2) generation was sensitive to potassium cyanide (a peroxidase inhibitor) but insensitive to diphenylene iodonium (an NADPH oxidase inhibitor), suggesting that H(2)O(2) generation depends on peroxidase in Arabidopsis. Together, these results indicate that the CaPO2 peroxidase is involved in ROS generation, both locally and systemically, to activate cell death and PR gene induction during the defense response to pathogen invasion.

Expression of extracellular calcium-sensing receptor in human osteoblastic MG-63 cell line

NASA Technical Reports Server (NTRS)

Yamaguchi, T.; Chattopadhyay, N.; Kifor, O.; Ye, C.; Vassilev, P. M.; Sanders, J. L.; Brown, E. M.

2001-01-01

We have previously shown the expression of the extracellular calcium (Ca2+o)-sensing receptor (CaR) in osteoblast-like cell lines, and others have documented its expression in sections of murine, bovine, and rat bone. The existence of the CaR in osteoblasts remains controversial, however, since some studies have failed to document its expression in the same osteoblast-like cell lines. The goals of the present study were twofold. 1) We sought to determine whether the CaR is expressed in the human osteoblast-like cell line, MG-63, which has recently been reported by others not to express this receptor. 2) We investigated whether the CaR, if present in MG-63 cells, is functionally active, since most previous studies have not proven the role of the CaR in mediating known actions of Ca2+o on osteoblast-like cells. We used immunocytochemistry and Western blotting with the specific, affinity-purified anti-CaR antiserum 4637 as well as Northern blot analysis and RT-PCR using a riboprobe and PCR primers specific for the human CaR, respectively, to show readily detectable CaR protein and mRNA expression in MG-63 cells. Finally, we employed the patch-clamp technique to show that an elevation in Ca2+o as well as the specific, allosteric CaR activator NPS R-467 (0.5 microM), but not its less active stereoisomer NPS S-467 (0.5 microM), activate an outward K+ channel in MG-63 cells, strongly suggesting that the CaR in MG-63 cells is not only expressed but is functionally active.

Effects of GABA and bicuculline on N-methyl-D-aspartate- and quisqualate-induced reductions in extracellular free calcium in area CA1 of the hippocampal slice.

PubMed

Hamon, B; Heinemann, U

1986-01-01

Decreases in extracellular free calcium ([Ca2+]o) and concomitant field potentials were recorded from the dendritic and cell body layers of the CA1 field in transverse hippocampal slices. They were elicited by tetanic stimulation of Schaffer collaterals and commissural fibers or by iontophoretic application of the excitatory amino acids N-methyl-D-aspartate (NMDA) and quisqualate (Quis). Under control conditions, decreases in [Ca2+]o were found to be maximal in stratum pyramidale (SP). In stratum radiatum (SR), 100 micron away from SP, decreases in [Ca2+]o were half the size of those observed in SP. Bicuculline methiodide, bath-applied at concentrations of 10-100 microM, enhanced the reductions in [Ca2+]o, increased the field potentials in all layers and also induced "spontaneous" epileptiform activity. In the presence of bicuculline, the decreases in [Ca2+]o were particularly enhanced in SR and were often greater than those recorded in SP. This was the case for changes in [Ca2+]o induced either by repetitive electrical stimulation or by application of NMDA and Quis. When synaptic transmission was blocked by perfusing the slices with a low Ca2+ medium, all NMDA and Quis-induced changes in [Ca2+]o were predictably reduced but there was a relative enhancement of changes in [Ca2+]o in SR with respect to those in SP. We propose that, under normal conditions, an inhibitory control mediated by GABA limits the reductions of [Ca2+]o particularly in SR. In support of this proposal, we found that bath-applied GABA had a depressant action on changes in [Ca2+]o.

Endoplasmic Reticulum Ca2+ Handling in Excitable Cells in Health and Disease

PubMed Central

Mattson, Mark P.

2011-01-01

The endoplasmic reticulum (ER) is a morphologically and functionally diverse organelle capable of integrating multiple extracellular and internal signals and generating adaptive cellular responses. It plays fundamental roles in protein synthesis and folding and in cellular responses to metabolic and proteotoxic stress. In addition, the ER stores and releases Ca2+ in sophisticated scenarios that regulate a range of processes in excitable cells throughout the body, including muscle contraction and relaxation, endocrine regulation of metabolism, learning and memory, and cell death. One or more Ca2+ ATPases and two types of ER membrane Ca2+ channels (inositol trisphosphate and ryanodine receptors) are the major proteins involved in ER Ca2+ uptake and release, respectively. There are also direct and indirect interactions of ER Ca2+ stores with plasma membrane and mitochondrial Ca2+-regulating systems. Pharmacological agents that selectively modify ER Ca2+ release or uptake have enabled studies that revealed many different physiological roles for ER Ca2+ signaling. Several inherited diseases are caused by mutations in ER Ca2+-regulating proteins, and perturbed ER Ca2+ homeostasis is implicated in a range of acquired disorders. Preclinical investigations suggest a therapeutic potential for use of agents that target ER Ca2+ handling systems of excitable cells in disorders ranging from cardiac arrhythmias and skeletal muscle myopathies to Alzheimer disease. PMID:21737534

Supported catalyst systems and method of making biodiesel products using such catalysts

DOEpatents

Kim, Manhoe; Yan, Shuli; Salley, Steven O.; Ng, K. Y. Simon

2015-10-20

A heterogeneous catalyst system, a method of preparing the catalyst system and a method of forming a biodiesel product via transesterification reactions using the catalyst system is disclosed. The catalyst system according to one aspect of the present disclosure represents a class of supported mixed metal oxides that include at least calcium oxide and another metal oxide deposited on a lanthanum oxide or cerium oxide support. Preferably, the catalysts include CaO--CeO.sub.2ZLa.sub.2O.sub.3 or CaO--La.sub.2O.sub.3/CeO.sub.2. Optionally, the catalyst may further include additional metal oxides, such as CaO--La.sub.2O.sub.3--GdOxZLa.sub.2O.sub.3.

Specific TRPC6 Channel Activation, a Novel Approach to Stimulate Keratinocyte Differentiation*S⃞

PubMed Central

Müller, Margarethe; Essin, Kirill; Hill, Kerstin; Beschmann, Heike; Rubant, Simone; Schempp, Christoph M.; Gollasch, Maik; Boehncke, W. Henning; Harteneck, Christian; Müller, Walter E.; Leuner, Kristina

2008-01-01

The protective epithelial barrier in our skin undergoes constant regulation, whereby the balance between differentiation and proliferation of keratinocytes plays a major role. Impaired keratinocyte differentiation and proliferation are key elements in the pathophysiology of several important dermatological diseases, including atopic dermatitis and psoriasis. Ca2+ influx plays an essential role in this process presumably mediated by different transient receptor potential (TRP) channels. However, investigating their individual role was hampered by the lack of specific stimulators or inhibitors. Because we have recently identified hyperforin as a specific TRPC6 activator, we investigated the contribution of TRPC6 to keratinocyte differentiation and proliferation. Like the endogenous differentiation stimulus high extracellular Ca2+ concentration ([Ca2+]o), hyperforin triggers differentiation in HaCaT cells and in primary cultures of human keratinocytes by inducing Ca2+ influx via TRPC6 channels and additional inhibition of proliferation. Knocking down TRPC6 channels prevents the induction of Ca2+- and hyperforin-induced differentiation. Importantly, TRPC6 activation is sufficient to induce keratinocyte differentiation similar to the physiological stimulus [Ca2+]o. Therefore, TRPC6 activation by hyperforin may represent a new innovative therapeutic strategy in skin disorders characterized by altered keratinocyte differentiation. PMID:18818211

Nonlinear optical crystal optimized for Ytterbium laser host wavelengths

DOEpatents

Ebbers, Christopher A [Pleasanton, CA; Schaffers, Kathleen I [Livermore, CA

2008-05-27

A material for harmonic generation has been made by substitutional changes to the crystal LaCa.sub.4 (BO.sub.3).sub.3 also known as LaCOB in the form Re1.sub.xRe2.sub.yRe3.sub.zCa.sub.4(B0.sub.3).sub.3O where Re1 and Re2, (rare earth ion 1 and rare earth ion 2) are selected from the group consisting of Sc, Yttrium, La, Ce, Pr, Nd, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb, and Lu; Re3 is Lanthanum; and x+y+z=1.

Nonlinear optical crystal optimized for Ytterbium laser host wavelengths

DOEpatents

Ebbers, Christopher A [Livermore, CA; Schaffers, Kathleen I [Pleasanton, CA

2007-02-20

A material for harmonic generation has been made by substitutional changes to the crystal LaCa.sub.4 (BO.sub.3).sub.3 also known as LaCOB in the form Re1.sub.xRe2.sub.yRe3.sub.zCa.sub.4(BO.sub.3).sub.3O where Re1 and Re2, (rare earth ion 1 and rare earth ion 2) are selected from the group consisting of Sc, Yttrium, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; Re3 is Lanthanum; and x+y+z=1.

Nonlinear optical crystal optimized for ytterbium laser host wavelengths

DOEpatents

Ebbers, Christopher A [Livermore, CA; Schaffers, Kathleen I [Pleasanton, CA

2007-08-21

A material for harmonic generation has been made by substitutional changes to the crystal LaCa.sub.4(BO.sub.3).sub.3 also known as LaCOB in the form Re1.sub.xRe2.sub.yRe3.sub.zCa.sub.4(B0.sub.3).sub.3O where Re1 and Re2, (rare earth ion 1 and rare earth ion 2) are selected from the group consisting of Sc, Yttrium, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; Re3 is Lanthanum; and x+y+z=1.

Modular Carbon and Gold Nanoparticles for High Field MR Imaging and Theranostics

NASA Astrophysics Data System (ADS)

Rammohan, Nikhil

The ability to track labeled cancer cells in vivo would allow researchers to study their distribution, growth and metastatic potential within the intact organism. Magnetic Resonance (MR) imaging is invaluable for tracking cancer cells in vivo as it benefits from high spatial resolution and absence of ionizing radiation. However, many MR contrast agents (CAs) required to label cells either do not significantly accumulate in cells or are not biologically compatible for translational studies. Accordingly, we have developed carbon- and gold-nanoparticles coupled to gadolinium(III) [Gd(III)] chelates for T1-weighted MR imaging that demonstrated remarkable properties for cell tracking in vitro and in vivo.. We created nanodiamond-Gd(III) aggregates (NDG) by peptide coupling Gd(III) chelates to aminated nanodiamonds. NDG had high relaxivity independent of field strength (unprecedented for Gd(III)-nanoparticle conjugates), and demonstrated a 300-fold increase in cellular delivery of Gd(III) compared to clinical Gd(III) chelates. Further, we were able to monitor the tumor growth of NDG-labeled flank tumors by T1-weighted MRI for 26 days in vivo, longer than reported for other MR CAs or nuclear agents. Further, theranostic nanodiamond-gadolinium(III)-doxorubicin (ND-Gd-Dox) aggregates were generated by conjugating doxorubicin (ND-Gd-Dox), which enabled efficient cancer chemotherapy in breast cancer cells. Further, we synthesized Gd(III)-gold nanoconjugates (Gd AuNPs) with varied chelate structure and nanoparticle-chelate linker length. Significantly enhanced cell labeling was demonstrated compared to previous gadolinium-gold-DNA nanoconstructs. Differences in Gd(III) loading, surface packing and cell uptake were observed between four different Gd AuNP formulations suggesting that linker length and surface charge play an important role in cell labeling. The best performing Gd AuNPs afforded 23.6 +/- 3.6 fmol of Gd(III) per cell at an incubation concentration of 27.5 microM. This efficiency of Gd(III) payload delivery (Gd(III)/cell normalized to dose) exceeds that of previously Gd(III)-Au conjugates and most other Gd(III)-nanoparticle formulations. Finally, Gd AuNPs were the first MR CAs of any type to effectively image the pancreas in vivo. . In summary, both Gd AuNPs and NDG support future MR-mediated cell tracking and theranostic applications in whole-animal models.

Extracellular protons enable activation of the calcium‐dependent chloride channel TMEM16A

PubMed Central

Cruz‐Rangel, Silvia; De Jesús‐Pérez, José J.; Aréchiga‐Figueroa, Iván A.; Rodríguez‐Menchaca, Aldo A.; Pérez‐Cornejo, Patricia; Hartzell, H. Criss

2017-01-01

Key points The calcium‐activated chloride channel TMEM16A provides a pathway for chloride ion movements that are key in preventing polyspermy, allowing fluid secretion, controlling blood pressure, and enabling gastrointestinal activity.TMEM16A is opened by voltage‐dependent calcium binding and regulated by permeant anions and intracellular protons.Here we show that a low proton concentration reduces TMEM16A activity while maximum activation is obtained when the external proton concentration is high.In addition, protonation conditions determine the open probability of TMEM16A without changing its calcium sensitivity. External glutamic acid 623 (E623) is key for TMEM16A's ability to respond to external protons.At physiological pH, E623 is un‐protonated and TMEM16A is activated when intracellular calcium increases; however, under acidic conditions E623 is partially protonated and works synergistically with intracellular calcium to activate the channel. These findings are critical for understanding physiological and pathological processes that involve changes in pH and chloride flux via TMEM16A. Abstract Transmembrane protein 16A (TMEM16A), also known as ANO1, the pore‐forming subunit of a Ca2+‐dependent Cl− channel (CaCC), is activated by direct, voltage‐dependent, binding of intracellular Ca2+. Endogenous CaCCs are regulated by extracellular protons; however, the molecular basis of such regulation remains unidentified. Here, we evaluated the effects of different extracellular proton concentrations ([H+]o) on mouse TMEM16A expressed in HEK‐293 cells using whole‐cell and inside‐out patch‐clamp recordings. We found that increasing the [H+]o from 10−10 to 10−5.5 m caused a progressive increase in the chloride current (I Cl) that is described by titration of a protonatable site with pK = 7.3. Protons regulate TMEM16A in a voltage‐independent manner, regardless of channel state (open or closed), and without altering its apparent Ca2+ sensitivity. Noise analysis showed that protons regulate TMEM16A by tuning its open probability without modifying the single channel current. We found a robust reduction of the proton effect at high [Ca2+]i. To identify protonation targets we mutated all extracellular glutamate and histidine residues and 4 of 11 aspartates. Most mutants were sensitive to protons. However, mutation that substituted glutamic acid (E) for glutamine (Q) at amino acid position 623 (E623Q) displayed a titration curve shifted to the left relative to wild type channels and the I Cl was nearly insensitive to proton concentrations between 10−5.5 and 10−9.0 m. Additionally, I Cl of the mutant containing an aspartic acid (D) to asparagine (N) substitution at position 405 (D405N) mutant was partially inhibited by a proton concentration of 10−5.5 m, but 10−9.0 m produced the same effect as in wild type. Based on our findings we propose that external protons titrate glutamic acid 623, which enables voltage activation of TMEM16A at non‐saturating [Ca2+]i. PMID:27859335

Extracellular protons enable activation of the calcium-dependent chloride channel TMEM16A.

PubMed

Cruz-Rangel, Silvia; De Jesús-Pérez, José J; Aréchiga-Figueroa, Iván A; Rodríguez-Menchaca, Aldo A; Pérez-Cornejo, Patricia; Hartzell, H Criss; Arreola, Jorge

2017-03-01

The calcium-activated chloride channel TMEM16A provides a pathway for chloride ion movements that are key in preventing polyspermy, allowing fluid secretion, controlling blood pressure, and enabling gastrointestinal activity. TMEM16A is opened by voltage-dependent calcium binding and regulated by permeant anions and intracellular protons. Here we show that a low proton concentration reduces TMEM16A activity while maximum activation is obtained when the external proton concentration is high. In addition, protonation conditions determine the open probability of TMEM16A without changing its calcium sensitivity. External glutamic acid 623 (E623) is key for TMEM16A's ability to respond to external protons. At physiological pH, E623 is un-protonated and TMEM16A is activated when intracellular calcium increases; however, under acidic conditions E623 is partially protonated and works synergistically with intracellular calcium to activate the channel. These findings are critical for understanding physiological and pathological processes that involve changes in pH and chloride flux via TMEM16A. Transmembrane protein 16A (TMEM16A), also known as ANO1, the pore-forming subunit of a Ca 2+ -dependent Cl - channel (CaCC), is activated by direct, voltage-dependent, binding of intracellular Ca 2+ . Endogenous CaCCs are regulated by extracellular protons; however, the molecular basis of such regulation remains unidentified. Here, we evaluated the effects of different extracellular proton concentrations ([H + ] o ) on mouse TMEM16A expressed in HEK-293 cells using whole-cell and inside-out patch-clamp recordings. We found that increasing the [H + ] o from 10 -10 to 10 -5.5  m caused a progressive increase in the chloride current (I Cl ) that is described by titration of a protonatable site with pK = 7.3. Protons regulate TMEM16A in a voltage-independent manner, regardless of channel state (open or closed), and without altering its apparent Ca 2+ sensitivity. Noise analysis showed that protons regulate TMEM16A by tuning its open probability without modifying the single channel current. We found a robust reduction of the proton effect at high [Ca 2+ ] i . To identify protonation targets we mutated all extracellular glutamate and histidine residues and 4 of 11 aspartates. Most mutants were sensitive to protons. However, mutation that substituted glutamic acid (E) for glutamine (Q) at amino acid position 623 (E623Q) displayed a titration curve shifted to the left relative to wild type channels and the I Cl was nearly insensitive to proton concentrations between 10 -5.5 and 10 -9.0  m. Additionally, I Cl of the mutant containing an aspartic acid (D) to asparagine (N) substitution at position 405 (D405N) mutant was partially inhibited by a proton concentration of 10 -5.5  m, but 10 -9.0  m produced the same effect as in wild type. Based on our findings we propose that external protons titrate glutamic acid 623, which enables voltage activation of TMEM16A at non-saturating [Ca 2+ ] i . © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

The effects of low sodium solutions on intracellular calcium concentration and tension in ferret ventricular muscle.

PubMed

Allen, D G; Eisner, D A; Lab, M J; Orchard, C H

1983-12-01

Papillary muscles from the right ventricles of ferrets were micro-injected with the photoprotein aequorin. Both tension and the light emitted by the aequorin, which is a measure of the free intracellular Ca concentration [( Ca2+]i), were monitored. Exposure of the papillary muscle to a solution in which all the Na had been replaced by K (0 Na(K) solution) resulted in an increase in tension which subsequently slowly decreased. This contracture was associated with a large increase in [Ca2+]i followed by a decrease to a steady-state-level which was often significantly greater than that in Na-containing solutions. If choline, Li or Tris was used instead of K as a substitute for Na, both the contracture and the associated increase of [Ca2+]i were reduced. The effects of depolarization alone (by raising external K at constant Na concentration) were compared with those of Na removal alone (at constant external K concentration). Na removal contributes more than depolarization to the effects of a Na-free, K-containing solution on the contracture and rise of [Ca2+]i. Increasing intracellular Na concentration [( Na+]i), by exposure to strophanthidin (10 mumol/l), increased the magnitude of both the contracture and [Ca2+]i in 0 Na(K) solutions. Conversely, decreasing [Na+]i by exposure to a solution containing a decreased extracellular Na concentration [( Na+]o), decreased the contracture and [Ca2+]i. When contractures were produced by solutions with various [Na+]o, the size of the resulting contracture and [Ca2+]i were inversely related to [Na+]o. No contracture was seen unless [Na+]o was reduced to below 70 mmol/l. A decrease in the extracellular Ca concentration [( Ca2+]o) from 2 to 0.5 mmol/l or an increase to 8 mmol/l produced, respectively, large decreases and increases of the twitch and accompanying Ca transient. However, if [Ca2+]o was changed at the same time as Na was replaced by K there was little effect on either the contracture or the rise of [Ca2+]i. If [Ca2+]o was changed before replacing Na by K then increasing [Ca2+]o from 2 to 8 mmol/l decreased, and decreasing [Ca2+]o from 2 to 0.5 mmol/l increased, the rise of [Ca2+]i produced by replacing Na by K. The difference between this result and that obtained when [Ca2+]o was changed at the same time as Na was removed may be due to changes of [Na+]i produced by prolonged exposure to an altered [Ca2+]o.(ABSTRACT TRUNCATED AT 400 WORDS)

The interplay of T1- and T2-relaxation on T1-weighted MRI of hMSCs induced by Gd-DOTA-peptides.

PubMed

Cao, Limin; Li, Binbin; Yi, Peiwei; Zhang, Hailu; Dai, Jianwu; Tan, Bo; Deng, Zongwu

2014-04-01

Three Gd-DOTA-peptide complexes with different peptide sequence are synthesized and used as T1 contrast agent to label human mesenchymal stem cells (hMSCs) for magnetic resonance imaging study. The peptides include a universal cell penetrating peptide TAT, a linear MSC-specific peptide EM7, and a cyclic MSC-specific peptide CC9. A significant difference in labeling efficacy is observed between the Gd-DOTA-peptides as well as a control Dotarem. All Gd-DOTA-peptides as well as Dotarem induce significant increase in T1 relaxation rate which is in favor of T1-weighted MR imaging. Gd-DOTA-CC9 yields the maximum labeling efficacy but poor T1 contrast enhancement. Gd-DOTA-EM7 yields the minimum labeling efficacy but better T1 contrast enhancement. Gd-DOTA-TAT yields a similar labeling efficacy as Gd-DOTA-CC9 and similar T1 contrast enhancement as Gd-DOTA-EM7. The underlying mechanism that governs T1 contrast enhancement effect is discussed. Our results suggest that T1 contrast enhancement induced by Gd-DOTA-peptides depends not only on the introduced cellular Gd content, but more importantly on the effect that Gd-DOTA-peptides exert on the T1-relaxation and T2-relaxation processes/rates. Both T1 and particularly T2 relaxation rate have to be taken into account to interpret T1 contrast enhancement. In addition, the interpretation has to be based on cellular instead of aqueous longitudinal and transverse relaxivities of Gd-DOTA-peptides. Copyright © 2014 Elsevier Ltd. All rights reserved.

Glucose-6-phosphate dehydrogenase status and severity of malarial anaemia in Nigerian children.

PubMed

Orimadegun, Adebola Emmanuel; Sodeinde, Olugbemiro

2011-11-15

Glucose-6-phosphate dehydrogenase (G6PD) deficiency (Gd-) contributes to morbidity and mortality in sub-Saharan Africa but recent data on the interaction between Gd- and malaria among children is scarce. We hypothesised that, being a haemolytic factor, Gd- makes severe malarial anaemia (SMA) more common and even more severe. We selected 930 children aged 0.5-12 years attending a reference hospital with microscopically proven falciparum malaria. G6PD and haemoglobin were typed by the fluorescent spot test and electrophoresis, respectively. Molecular typing by PCR and restriction enzyme digestion was also performed on 15% of randomly selected samples. Haematocrit (PCV) values, haemoglobin type, blood group, presence of sickle cell trait (HbAS), and parasite counts were compared between G6PD-normal and deficient children. Prevalence of Gd- was 16.4% and 8.1% among boys and girls with malaria, respectively. Mean PCV was 22.8% in deficient children compared with 21.0% in normal children (p = 0.041). In boys, 2.7% of Gd- had PCV ≤ 10%, as compared to 13.6% in Gd+ (p = 0.005). Similarly, 21.3% of Gd- had PCV ≤ 15% compared with 39.4% in Gd+ (p = 0.003). No such difference was found among girls. Overall, HbAS was typed in 7.6% and was more common in Gd- (13.0%) than in Gd+ (6.8%), but the difference was not statistically significant (p = 0.058). The mean parasite counts were significantly lower in Gd- (15477.5/µl) than in Gd+ (19784.4/µl; p = 0.013), and it was independent from HbAS. Gd- males but not females were significantly less likely to develop severe malarial anaemia.

Enrichment of Extracellular Carbonic Anhydrase in the Sea Surface Microlayer and Its Effect on Air-Sea CO2 Exchange

NASA Astrophysics Data System (ADS)

Mustaffa, N. I. H.; Striebel, M.; Wurl, O.

2017-12-01

This paper describes the quantification of extracellular carbonic anhydrase (eCA) concentrations in the sea surface microlayer (SML), the boundary layer between the ocean and the atmosphere of the Indo-West Pacific. We demonstrated that the SML is enriched with eCA by 1.5 ± 0.7 compared to the mixed underlying water. Enrichment remains up to a wind speed of 7 m s-1 (i.e., under typical oceanic conditions). As eCA catalyzes the interconversion of HCO3- and CO2, it has been hypothesized that its enrichment in the SML enhances the air-sea CO2 exchange. We detected concentrations in the range of 0.12 to 0.76 nM, which can enhance the exchange by up to 15% based on the model approach described in the literature.

Structure-function analysis of soluble forms of herpes simplex virus glycoprotein D.

PubMed Central

Nicola, A V; Willis, S H; Naidoo, N N; Eisenberg, R J; Cohen, G H

1996-01-01

Glycoprotein D (gD) of herpes simplex virus (HSV) is essential for virus entry. Truncated forms of gD lacking the transmembrane and cytoplasmic tail regions have been shown to bind to cells and block plaque formation. Using complementation analysis and a panel of gD mutants, we previously identified four regions of gD (regions I to IV) which are important for virus entry. Here, we used baculovirus vectors to overexpress truncated forms of wild-type gD from HSV type 1 (HSV-1) [gD-1(306t)] and HSV-2 [gD-2(306t)] and four mutants, gD-1(inverted delta 34t), gD-1(inverted delta 126t), gD-1(inverted delta 243t), and gD-1(delta 290-299t), each having a mutation in one of the four functional regions. We used an enzyme-linked immunosorbent assay and circular dichroism to analyze the structure of these proteins, and we used functional assays to study the role of gD in binding, penetration, and cell-to-cell spread. gD-1 and gD-2 are similar in antigenic structure and thermal stability but vary in secondary structure. Mutant proteins with insertions in region I or II were most altered in structure and stability, while mutants with insertions in region III or IV were less altered. gD-1(306t) and gD-2(306t) inhibited both plaque formation and cell-to-cell transmission of HSV-1. In spite of obvious structural differences, all of the mutant proteins bound to cells, confirming that binding is not the only function of gD. The region I mutant did not inhibit HSV plaque formation or cell-to-cell spread, suggesting that this region is necessary for the function of gD in these processes. Surprisingly, the other three mutant proteins functioned in all of the in vitro assays, indicating that the ability of gD to bind to cells and inhibit infection does not correlate with its ability to initiate infection as measured by the complementation assay. The region IV mutant, gD-1(delta 290-299t), had an unexpected enhanced inhibitory effect on HSV infection. Taken together, the results argue against a single functional domain in gD. It is likely that different gD structural elements are involved in successive steps of infection. PMID:8648717

Distinct roles for extracellular and intracellular domains in neuroligin function at inhibitory synapses.

PubMed

Nguyen, Quynh-Anh; Horn, Meryl E; Nicoll, Roger A

2016-11-02

Neuroligins (NLGNs) are postsynaptic cell adhesion molecules that interact trans-synaptically with neurexins to mediate synapse development and function. NLGN2 is only at inhibitory synapses while NLGN3 is at both excitatory and inhibitory synapses. We found that NLGN3 function at inhibitory synapses in rat CA1 depends on the presence of NLGN2 and identified a domain in the extracellular region that accounted for this functional difference between NLGN2 and 3 specifically at inhibitory synapses. We further show that the presence of a cytoplasmic tail (c-tail) is indispensible, and identified two domains in the c-tail that are necessary for NLGN function at inhibitory synapses. These domains point to a gephyrin-dependent mechanism that is disrupted by an autism-associated mutation at R705 and a gephyrin-independent mechanism reliant on a putative phosphorylation site at S714. Our work highlights unique and separate roles for the extracellular and intracellular regions in specifying and carrying out NLGN function respectively.

Glycoprotein D of herpes simplex virus (HSV) binds directly to HVEM, a member of the tumor necrosis factor receptor superfamily and a mediator of HSV entry.

PubMed Central

Whitbeck, J C; Peng, C; Lou, H; Xu, R; Willis, S H; Ponce de Leon, M; Peng, T; Nicola, A V; Montgomery, R I; Warner, M S; Soulika, A M; Spruce, L A; Moore, W T; Lambris, J D; Spear, P G; Cohen, G H; Eisenberg, R J

1997-01-01

Glycoprotein D (gD) is a structural component of the herpes simplex virus (HSV) envelope which is essential for virus entry into host cells. Chinese hamster ovary (CHO-K1) cells are one of the few cell types which are nonpermissive for the entry of many HSV strains. However, when these cells are transformed with the gene for the herpesvirus entry mediator (HVEM), the resulting cells, CHO-HVEM12, are permissive for many HSV strains, such as HSV-1(KOS). By virtue of its four cysteine-rich pseudorepeats, HVEM is a member of the tumor necrosis factor receptor superfamily of proteins. Recombinant forms of gD and HVEM, gD-1(306t) and HVEM(200t), respectively, were used to demonstrate a specific physical interaction between these two proteins. This interaction was dependent on native gD conformation but independent of its N-linked oligosaccharides, as expected from previous structure-function studies. Recombinant forms of gD derived from HSV-1(KOS)rid1 and HSV-1(ANG) did not bind to HVEM(200t), explaining the inability of these viruses to infect CHO-HVEM12 cells. A variant gD protein, gD-1(delta290-299t), showed enhanced binding to HVEM(200t) relative to the binding of gD-1(306t). Competition studies showed that gD-1(delta290-299t) and gD-1(306t) bound to the same region of HVEM(200t), suggesting that the differences in binding to HVEM are due to differences in affinity. These differences were also reflected in the ability of gD-1(delta290-299t) but not gD-1(306t) to block HSV type 1 infection of CHO-HVEM12 cells. By gel filtration chromatography, the complex between gD-1(delta290-299t) and HVEM(200t) had a molecular mass of 113 kDa and a molar ratio of 1:2. We conclude that HVEM interacts directly with gD, suggesting that HVEM is a receptor for virion gD and that the interaction between these proteins is a step in HSV entry into HVEM-expressing cells. PMID:9223502

Inhibitors of the 5-lipoxygenase arachidonic acid pathway induce ATP release and ATP-dependent organic cation transport in macrophages.

PubMed

da Silva-Souza, Hercules Antônio; Lira, Maria Nathalia de; Costa-Junior, Helio Miranda; da Cruz, Cristiane Monteiro; Vasconcellos, Jorge Silvio Silva; Mendes, Anderson Nogueira; Pimenta-Reis, Gabriela; Alvarez, Cora Lilia; Faccioli, Lucia Helena; Serezani, Carlos Henrique; Schachter, Julieta; Persechini, Pedro Muanis

2014-07-01

We have previously described that arachidonic acid (AA)-5-lipoxygenase (5-LO) metabolism inhibitors such as NDGA and MK886, inhibit cell death by apoptosis, but not by necrosis, induced by extracellular ATP (ATPe) binding to P2X7 receptors in macrophages. ATPe binding to P2X7 also induces large cationic and anionic organic molecules uptake in these cells, a process that involves at least two distinct transport mechanisms: one for cations and another for anions. Here we show that inhibitors of the AA-5-LO pathway do not inhibit P2X7 receptors, as judged by the maintenance of the ATPe-induced uptake of fluorescent anionic dyes. In addition, we describe two new transport phenomena induced by these inhibitors in macrophages: a cation-selective uptake of fluorescent dyes and the release of ATP. The cation uptake requires secreted ATPe, but, differently from the P2X7/ATPe-induced phenomena, it is also present in macrophages derived from mice deficient in the P2X7 gene. Inhibitors of phospholipase A2 and of the AA-cyclooxygenase pathway did not induce the cation uptake. The uptake of non-organic cations was investigated by measuring the free intracellular Ca(2+) concentration ([Ca(2+)]i) by Fura-2 fluorescence. NDGA, but not MK886, induced an increase in [Ca(2+)]i. Chelating Ca(2+) ions in the extracellular medium suppressed the intracellular Ca(2+) signal without interfering in the uptake of cationic dyes. We conclude that inhibitors of the AA-5-LO pathway do not block P2X7 receptors, trigger the release of ATP, and induce an ATP-dependent uptake of organic cations by a Ca(2+)- and P2X7-independent transport mechanism in macrophages. Copyright © 2014 Elsevier B.V. All rights reserved.

The Calcium-Sensing Receptor and Integrins in Cellular Differentiation and Migration

PubMed Central

Tharmalingam, Sujeenthar; Hampson, David R.

2016-01-01

The calcium-sensing receptor (CaSR) is a widely expressed homodimeric G-protein coupled receptor structurally related to the metabotropic glutamate receptors and GPRC6A. In addition to its well characterized role in maintaining calcium homeostasis and regulating parathyroid hormone release, evidence has accumulated linking the CaSR with cellular differentiation and migration, brain development, stem cell engraftment, wound healing, and tumor growth and metastasis. Elevated expression of the CaSR in aggressive metastatic tumors has been suggested as a potential novel prognostic marker for predicting metastasis, especially to bone tissue where extracellular calcium concentrations may be sufficiently high to activate the receptor. Recent evidence supports a model whereby CaSR-mediated activation of integrins promotes cellular migration. Integrins are single transmembrane spanning heterodimeric adhesion receptors that mediate cell migration by binding to extracellular matrix proteins. The CaSR has been shown to form signaling complexes with the integrins to facilitate both the movement and differentiation of cells, such as neurons during normal brain development and tumor cells under pathological circumstances. Thus, CaSR/integrin complexes may function as a universal cell migration or homing complex. Manipulation of this complex may be of potential interest for treating metastatic cancers, and for developmental disorders pertaining to aberrant neuronal migration. PMID:27303307

The augmenting action of banana tree juice on skeletal muscle contraction.

PubMed

Singh, Y N; Dryden, W F

1990-01-01

An extract obtained from juice expressed from the stem of the plantain banana tree (Musa sapientum L., var. paradisiaca) induces twitch augmentation in skeletal muscles. The mechanism of this action was investigated in the mouse hemi-diaphragm preparation. Directly evoked twitches and potassium induced (K+) contractures were both augmented by the extract. Twitch augmentation was partly dependent on extracellular Ca2+. The action on K(+)-contractures was unaffected by tetrodotoxin, but the rate of relaxation was enhanced in the absence of extracellular calcium (0[Ca2+]o). Muscle contracture induced by high concentrations of extract was also augmented in 0[Ca2+]o and in the presence of the Ca2(+)-channel blocking agent, nifedipine. The time course of the contracture was shortened in 0[Ca2+]o, but not by nifedipine. Nifedipine enhanced the augmenting effect of the extract on twitches but shortened the time-course of this action. In addition, a muscle contracture was superimposed on the twitching muscle at higher concentrations of nifedipine. Manganese, on the other hand, reduced or abolished the augmenting action of the extract. The results are consistent with an action of banana tree juice on the molecule responsible for excitation-contraction coupling in skeletal muscle, resulting in a labilization of intracellular Ca2+.

Paroxetine-induced apoptosis in human osteosarcoma cells: Activation of p38 MAP kinase and caspase-3 pathways without involvement of [Ca{sup 2+}]{sub i} elevation

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

Chou, C.-T.; Department of Biological Sciences, National Sun Yat-sen University, 804, Taiwan; He Shiping

2007-02-01

Selective serotonin reuptake inhibitors (SSRIs), a group of antidepressants, are generally used for treatment of various mood and anxiety disorders. There has been much research showing the anti-tumor and cytotoxic activities of some antidepressants; but the detailed mechanisms were unclear. In cultured human osteosarcoma cells (MG63), paroxetine reduced cell viability in a concentration- and time-dependent manner. Paroxetine caused apoptosis as assessed by propidium iodide-stained cells and increased caspase-3 activation. Although immunoblotting data revealed that paroxetine could activate the phosphorylation of extracellular signal-regulated kinase (ERK), c-Jun NH{sub 2}-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38 MAPK), only SB203580 (a p38more » MAPK inhibitor) partially prevented cells from apoptosis. Paroxetine also induced [Ca{sup 2+}]{sub i} increases which involved the mobilization of intracellular Ca{sup 2+} stored in the endoplasmic reticulum and Ca{sup 2+} influx from extracellular medium. However, pretreatment with BAPTA/AM, a Ca{sup 2+} chelator, to prevent paroxetine-induced [Ca{sup 2+}]{sub i} increases did not protect cells from death. The results suggest that in MG63 cells, paroxetine caused Ca{sup 2+}-independent apoptosis via inducing p38 MAPK-associated caspase-3 activation.« less

Calcimimetic and Calcilytic Drugs: Feats, Flops, and Futures.

PubMed

Nemeth, E F; Goodman, W G

2016-04-01

The actions of extracellular Ca(2+) in regulating parathyroid gland and kidney functions are mediated by the extracellular calcium receptor (CaR), a G protein-coupled receptor. The CaR is one of the essential molecules maintaining systemic Ca(2+) homeostasis and is a molecular target for drugs useful in treating bone and mineral disorders. Ligands that activate the CaR are termed calcimimetics and are classified as either agonists (type I) or positive allosteric modulators (type II); calcimimetics inhibit the secretion of parathyroid hormone (PTH). Cinacalcet is a type II calcimimetic that is used to treat secondary hyperparathyroidism in patients receiving dialysis and to treat hypercalcemia in some forms of primary hyperparathyroidism. The use of cinacalcet among patients with secondary hyperparathyroidism who are managed with dialysis effectively lowers circulating PTH levels, reduces serum phosphorus and FGF23 concentrations, improves bone histopathology, and may diminish skeletal fracture rates and the need for parathyroidectomy. A second generation type II calcimimetic (AMG 416) is currently under regulatory review. Calcilytics are CaR antagonists that stimulate the secretion of PTH. Several calcilytic compounds have been evaluated as orally active anabolic therapies for postmenopausal osteoporosis but clinical development of all of them has been abandoned because they lacked clinical efficacy. Calcilytics might be repurposed for new indications like autosomal dominant hypocalcemia or other disorders beyond those involving systemic Ca(2+) homeostasis.

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

PubMed

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

2014-09-11

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

Role of external and internal calcium on heterocarrier-mediated transmitter release.

PubMed

Fassio, A; Bonanno, G; Fontana, G; Usai, C; Marchi, M; Raiteri, M

1996-04-01

Release-regulating heterocarriers exist on brain nerve endings. We have investigated in this study the mechanisms involved in the neurotransmitter release evoked by GABA heterocarrier activation. GABA increased the basal release of [3H]acetylcholine and [3H]noradrenaline from rat hippocampal synaptosomes and of [3H]dopamine from striatal synaptosomes. These GABA effects, insensitive to GABA receptor antagonists, were prevented by inhibiting GABA uptake but not by blocking noradrenaline, choline, or dopamine transport. Lack of extracellular Ca2+ or addition of tetrodotoxin selectively abolished the GABA-evoked release of [3H]noradrenaline, leaving unaffected that of [3H]acetylcholine or [3H]dopamine. 1,2-Bis(2-aminophenoxyl)-ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester (BAPTA-AM) or vesamicol attenuated the release of [3H]acetylcholine elicited by GABA. Reserpine, but not BAPTA-AM, prevented the effect of GABA on [3H] dopamine release. Autoreceptor activation inhibited the GABA-evoked release of [3H]noradrenaline but not that of [3H]acetylcholine or [3H]dopamine. It is concluded that (a) the release of [3H]noradrenaline consequent to activation of GABA heterocarriers sited on noradrenergic terminals meets the criteria of a conventional exocytotic process, (b) the extracellular [Ca2+]-independent releases of [3H]acetylcholine and [3H]dopamine appear to occur from vesicles possibly through involvement of intraterminal Ca2+, and (c) autoreceptor activation only affects heterocarrier-mediated vesicular release linked to entry of extracellular Ca2+.

Zinc signaling in the hippocampus and its relation to pathogenesis of depression.

PubMed

Takeda, Atsushi

2012-06-01

Histochemically reactive zinc (Zn(2+)) is co-released with glutamate from zincergic neurons, a subclass of glutamatergic neurons. Zn(2+) serves as a signal factor in both the extracellular and intracellular compartments. Glucocorticoid-glutamatergic interactions have been proposed as a potential model to explain stress-mediated impairment of hippocampal function, i.e., cognition. However, it is unknown whether glucocorticoid-zincergic interactions are involved in this impairment. In the present study, involvement of synaptic Zn(2+) in stress-induced attenuation of CA1 LTP was examined in hippocampal slices from young rats after exposure to tail suspension stress for 30s, which significantly increased serum corticosterone. Stress-induced attenuation of CA1 LTP was ameliorated by administration of clioquinol, a membrane permeable zinc chelator, to rats prior to exposure to stress, implying that the reduction of synaptic Zn(2+) by clioquinol participates in this amelioration. To pursue the involvement of corticosterone-mediated Zn(2+) signal in the attenuated CA1 LTP by stress, dynamics of synaptic Zn(2+) was checked in hippocampal slices exposed to corticosterone. Corticosterone increased extracellular Zn(2+) levels measured with ZnAF-2 dose-dependently, as well as the intracellular Ca(2+) levels measured with calcium orange AM, suggesting that corticosterone excites zincergic neurons in the hippocampus and increases Zn(2+) release from the neuron terminals. Intracellular Zn(2+) levels measured with ZnAF-2DA were also increased dose-dependently, but not in the coexistence of CaEDTA, a membrane-impermeable zinc chelator, suggesting that intracellular Zn(2+) levels is increased by the influx of extracellular Zn(2+). Furthermore, corticosterone-induced attenuation of CA1 LTP was abolished in the coexistence of CaEDTA. The present study suggests that corticosterone-mediated increase in postsynaptic Zn(2+) signal in the cytosolic compartment is involved in the attenuation of CA1 LTP after exposure to acute stress. We propose that corticosterone-mediated increase in postsynaptic Zn(2+) signal, which is induced by acute stress, changes hippocampal function and then is possibly a risk factor under chronic stress circumstances to induce depressive symptoms. Copyright © 2012 Elsevier GmbH. All rights reserved.

Is there lattice contraction in multicomponent metal oxides? Case study for GdVO4:Eu3+ nanoparticles.

PubMed

Yang, Liusai; Li, Liping; Zhao, Minglei; Fu, Chaochao; Li, Guangshe

2013-08-02

Metal oxide nanomaterials have been found to have great potential for diverse applications due to their unique relationships between structure and properties. Lattice expansion as particle size reduces was previously considered to be general for metal oxide nanomaterials. It is now a great challenge to see if lattice contraction could be induced by the size effect for metal oxide nanomaterials. ABO4 metal oxides (e.g., CaWO4, GdVO4, and CdWO4) are some of the most important functional materials with many applications, while such oxides at the nanoscale are never reported to show a lattice contraction. This work presents a first report on the variation from lattice expansion to lattice contraction by tuning the microstructures of GdVO4:Eu(3+) nanocrystals. A hydrothermal method was adopted to synthesize GdVO4:Eu(3+) nanocrystals, and then these nanoparticles were calcined at 600 ° C in air. It is found that particle size reduction led to a lattice contraction for the calcined samples, which is in contrast to the lattice expansion observed for the hydrothermally synthesized counterparts or many other metal oxide nanomaterials. In addition, the lattice symmetry of the calcined samples remained almost a constant. The results indicate that the negative surface stress was eliminated by calcination treatment, leading to a homogeneous compression process in the lattice structure of the calcined GdVO4:Eu(3+) nanocrystals. Furthermore, Eu(3+) was taken as a structural probe and a luminescence center to study the local environments pertinent to these structural changes and to optimize the photoluminescence performance.

Optical properties in the visible luminescence of SiO2:B2O3:CaO:GdF3 glass scintillators containing CeF3

NASA Astrophysics Data System (ADS)

Park, J. M.; Kim, H. J.; Karki, Sujita; Kaewkhao, J.; Damdee, B.; Kothan, S.; Kaewjaeng, S.

2017-12-01

CeF3-doped silicaborate-calcium-gadolinium glass scintillators, with the formula 10SiO2:(55-x)B2O3:10CaO:25GdF3:xCeF3, were fabricated by the melt-quenching technique. The doping concentration of the CeF3 was from 0.00 mol% to 0.20 mol%. The optical properties of the CeF3 doped glass scintillators were studied by using various radiation sources. The transition state of the CeF3-doped glass scintillators studied by using the absorption and photo-luminescence spectrum results. The X-ray, photo, proton and laser-induced luminescence spectra were also studied to understand the luminescence mechanism under various conditions. To understand the temperature dependence, the laser-induced luminescence and the decay component of the CeF3-doped glass scintillator were studied while the temperature was varied from 300 K to 10 K. The emission wavelength spectrum showed from 350 nm to 55 nm under various radiation sources. Also the CeF3-doped glass scintillator have one decay component as 34 ns at room temperature.

Multivalent Protein Polymer MRI Contrast Agents: Controlling Relaxivity via Modulation of Amino Acid Sequence

PubMed Central

Karfeld-Sulzer, Lindsay S.; Waters, Emily A.; Davis, Nicolynn E.; Meade, Thomas J.; Barron, Annelise E.

2010-01-01

Magnetic Resonance Imaging (MRI) is a noninvasive imaging modality with high spatial and temporal resolution. Contrast agents (CAs) are frequently used to increase the contrast between tissues of interest. To increase the effectiveness of MR agents, small molecule CAs have been attached to macromolecules. We have created a family of biodegradable, macromolecular CAs based on protein polymers, allowing control over the CA properties. The protein polymers are monodisperse, random coil, and contain evenly spaced lysines that serve as reactive sites for Gd(III) chelates. The exact sequence and length of the protein can be specified, enabling controlled variation in lysine spacing and molecular weight. Relaxivity could be modulated by changing protein polymer length and lysine spacing. Relaxivities of up to ∼14 mM-1s-1 per Gd(III) and ∼461 mM-1s-1 per conjugate were observed. These CAs are biodegradable by incubation with plasmin, such that they can be easily excreted after use. They do not reduce cell viability, a prerequisite for future in vivo studies. The protein polymer CAs can be customized for different clinical diagnostic applications, including biomaterial tracking, as a balanced agent with high relaxivity and appropriate molar mass. PMID:20420441

Muscarinic receptor-mediated excitation of rat intracardiac ganglion neurons.

PubMed

Hirayama, Michiko; Ogata, Masanori; Kawamata, Tomoyuki; Ishibashi, Hitoshi

2015-08-01

Modulation of the membrane excitability of rat parasympathetic intracardiac ganglion neurons by muscarinic receptors was studied using an amphotericin B-perforated patch-clamp recording configuration. Activation of muscarinic receptors by oxotremorine-M (OxoM) depolarized the membrane, accompanied by repetitive action potentials. OxoM evoked inward currents under voltage-clamp conditions at a holding potential of -60 mV. Removal of extracellular Ca(2+) markedly increased the OxoM-induced current (IOxoM). The inward IOxoM in the absence of extracellular Ca(2+) was fully inhibited by removal of extracellular Na(+), indicating the involvement of non-selective cation channels. The IOxoM was inhibited by organic cation channel antagonists including SKF-96365 and ML-204. The IOxoM was antagonized by muscarinic receptor antagonists with the following potency: 4-DAMP > pirenzepine = darifenacin > methoctramine. Muscarinic toxin 7 (MT-7), a highly selective inhibitor for M1 receptor, produced partial inhibition of the IOxoM. In the presence of MT-7, concentration-inhibition curve of the M3-preferring antagonist darifenacin was shifted to the left. These results suggest the contribution of M1 and M3 receptors to the OxoM response. The IOxoM was inhibited by U-73122, a phospholipase C inhibitor. The membrane-permeable IP3 receptor blocker xestospongin C also inhibited the IOxoM. Furthermore, pretreatment with thapsigargin and BAPTA-AM inhibited the IOxoM, while KN-62, a blocker of Ca(2+)/calmodulin-dependent protein kinase II, had no effect. These results suggest that the activation mechanism involves a PLC pathway, release of Ca(2+) from intracellular Ca(2+) stores and calmodulin. The cation channels activated by muscarinic receptors may play an important role in neuronal membrane depolarization in rat intracardiac ganglion neurons. Copyright © 2015 Elsevier Ltd. All rights reserved.

Ca2+ current vs. Ca2+ channel cooperativity of exocytosis

PubMed Central

Matveev, Victor; Bertram, Richard; Sherman, Arthur

2009-01-01

Recently there has been significant interest and progress in the study of spatio-temporal dynamics of Ca2+ that triggers exocytosis at a fast chemical synapse, which requires understanding the contribution of individual calcium channels to the release of a single vesicle. Experimental protocols provide insight into this question by probing the sensitivity of exocytosis to Ca2+ influx. While varying extracellular or intracellular Ca2+ concentration assesses the intrinsic biochemical Ca2+ cooperativity of neurotransmitter release, varying the number of open Ca2+ channels using pharmacological channel block or the tail current titration probes the cooperativity between individual Ca2+ channels in triggering exocytosis. Despite the wide use of these Ca2+ sensitivity measurements, their interpretation often relies on heuristic arguments. Here we provide a detailed analysis of the Ca2+ sensitivity measures probed by these experimental protocols, present simple expressions for special cases, and demonstrate the distinction between the Ca2+ current cooperativity, defined by the relationship between exocytosis rate and the whole-terminal Ca2+ current magnitude, and the underlying Ca2+ channel cooperativity, defined as the average number of channels involved in the release of a single vesicle. We find simple algebraic expressions that show that the two are different but linearly related. Further, we use 3D computational modeling of buffered Ca2+ diffusion to analyze these distinct Ca2+ cooperativity measures, and demonstrate the role of endogenous Ca2+ buffers on such measures. We show that buffers can either increase or decrease the Ca2+ current cooperativity of exocytosis, depending on their concentration and the single-channel Ca2+ current. PMID:19793978

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

PubMed

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

2017-11-24

Objective: To investigate the interaction of Ca(2+) protein TRPC1 and STIM1 in extracellular Ca(2+) -sensing receptor (CaR)-induced extracellular Ca(2+) influx and the production of nitric oxide (NO). Methods: Human umbilical vein endothelial cells (HUVECs) were cultured and incubated with CaR agonist spermine (activating store-operates cation channels (SOC) and receptor-operated channels (ROC)), CaR negative allosteric modulator Calhex231 (blocking SOC, activating ROC) and ROC analogue TPA (activating ROC, blocking SOC), protein kinase C (PKC) inhibitor Ro31-8220, PKCs and PKCμ inhibitor Go6967(activate SOC, blocking ROC), respectively. The interaction of TRPC1 and STIM1 was determined using the immunofluorescence methods. The interaction between TRPC1 and STIM1 were examined by Co-immuno precipitation. The HUVECs were divided into: TRPC1 and STIM1 short hairpin RNA group (shTRPC1+ shSTIM1 group), vehicle-TRPC1+ vehicle-STIM1 group and control group. The cells were incubated with four different treatments under the action of above mentioned interventions, intracellular Ca(2+) concentration ([Ca(2+) ](i)) was detected using the fluorescence Ca(2+) indicator Fura-2/AM, the production of NO was determined by DAF-FM. Results: (1) The expression of TRPC1 and STIM1 proteins levels in HUVECs: Under the confocal microscope, TRPC1 and STIM1 protein expression showed masculine gender, both located in cytoplasm in the normal control group. Post incubation with Calhex231+ TPA, Ro31-8220 and Go6967, TRPC1 and STIM1 positioned in cytoplasm was significantly reduced, and the combined TRPC1 and STIM1 was also significantly reduced. (2) The interaction of TRPC1 and STIM1 in HUVECs: The relative ratios of Calhex231+ TPA+ Spermine+ Ca(2+) group, Ro31-8220+ Spermine+ Ca(2+) group and Go6976+ Spermine+ Ca(2+) group STIM1/TRPC1 and TRPC1/STIM1 were as follows: (25.98±2.17)% and (44.10±4.01)%, (20.85±1.01)% and (46.31±3.47)%, (23.88±2.05)% and (39.65±2.91)%, which were significantly lower than those in the control group (100.00±4.66)% and (100.00±6.40)% and in the Spermine+ Ca(2+) group (106.04±2.45)% and (107.78±2.66)% (all P <0.05). (3) The influence of joint TRPC1 and STIM1 transfection to four different drugs treated HUVECs on [Ca(2+) ](i) and NO generation: The changes of two excitation fluorescence intensity ratio and NO net fluorescence intensity values were consistent, [Ca(2+) ](i) and NO net fluorescence intensity values were significantly lower in the experimental group than the control group and the vehicle group (all P <0.05), while which were similar between the vehicle group and control group (all P >0.05). Conclusions: Our results indicate that TRPC1 and STIM1 jointly regulate CaR-mediated Ca(2+) influx and nitric oxide generation in HUVECs in the form of binary complex.

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

The impact of extracellular syntaxin4 on HaCaT keratinocyte behavior

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

Kadono, Nanako; Miyazaki, Takafumi; Okugawa, Yoji

2012-01-27

Highlights: Black-Right-Pointing-Pointer A subpopulation of syntaxin4 localizes extracellularly in the keratinocytes. Black-Right-Pointing-Pointer Epimorphin and syntaxin4 confer the resistance to the oxidative stress. Black-Right-Pointing-Pointer Epimorphin suppresses and syntaxin4 accelerates the CCE formation. Black-Right-Pointing-Pointer The antagonistic peptide to syntaxin4 blocks the syntaxin4-dependent CCE formation. -- Abstract: Syntaxin4 belongs to t-SNARE protein family and functions as a vesicular fusion mediator in the plasma membrane in a wide variety of cell types. This protein resembles another family member, epimorphin, a subpopulation of which has been shown to be secreted extracellularly in order to exert signaling functions. Here, we demonstrate the secretion of syntaxin4 viamore » a non-classical pathway and its extracellular functions by using the functionally normal keratinocyte HaCaT. Extracellularly presented syntaxin4 appeared to elicit many cell responses similar to epimorphin with an important exception: it clearly facilitated keratinocyte cornification. The circularized peptide ST4n1 was synthesized from the putative functional core of syntaxin4 (a.a. 103-108), which is equivalent to the previously generated antagonist of epimorphin, and neutralized this contradictory effect. Intriguingly, an epimorphin mutant (EP4M) in which the functional core was replaced by that of syntaxin4 behaved like epimorphin, which was again antagonized by ST4n1. Electrophoresis-based analyses demonstrated the distinct structure of syntaxin4 compared to epimorphin or EP4M. These results revealed, for the first time, the extracellular role of syntaxin4 and shed light on the division of the extracellular effects exerted by epimorphin and syntaxin4 on keratinocyte cornification.« less

Neurotransmitter modulation of extracellular H+ fluxes from isolated retinal horizontal cells of the skate

PubMed Central

Molina, Anthony J A; Verzi, Michael P; Birnbaum, Andrea D; Yamoah, Ebenezer N; Hammar, Katherine; Smith, Peter J S; Malchow, Robert Paul

2004-01-01

Self-referencing H+-selective microelectrodes were used to measure extracellular H+ fluxes from horizontal cells isolated from the skate retina. A standing H+ flux was detected from quiescent cells, indicating a higher concentration of free hydrogen ions near the extracellular surface of the cell as compared to the surrounding solution. The standing H+ flux was reduced by removal of extracellular sodium or application of 5-(N-ethyl-N-isopropyl) amiloride (EIPA), suggesting activity of a Na+–H+ exchanger. Glutamate decreased H+ flux, lowering the concentration of free hydrogen ions around the cell. AMPA/kainate receptor agonists mimicked the response, and the AMPA/kainate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) eliminated the effects of glutamate and kainate. Metabotropic glutamate agonists were without effect. Glutamate-induced alterations in H+ flux required extracellular calcium, and were abolished when cells were bathed in an alkaline Ringer solution. Increasing intracellular calcium by photolysis of the caged calcium compound NP-EGTA also altered extracellular H+ flux. Immunocytochemical localization of the plasmalemma Ca2+–H+-ATPase (PMCA pump) revealed intense labelling within the outer plexiform layer and on isolated horizontal cells. Our results suggest that glutamate modulation of H+ flux arises from calcium entry into cells with subsequent activation of the plasmalemma Ca2+–H+-ATPase. These neurotransmitter-induced changes in extracellular pH have the potential to play a modulatory role in synaptic processing in the outer retina. However, our findings argue against the hypothesis that hydrogen ions released by horizontal cells normally act as the inhibitory feedback neurotransmitter onto photoreceptor synaptic terminals to create the surround portion of the centre-surround receptive fields of retinal neurones. PMID:15272044

The biphasic effect of extracellular glucose concentration on carbachol-induced fluid secretion from mouse submandibular glands.

PubMed

Terachi, Momomi; Hirono, Chikara; Kitagawa, Michinori; Sugita, Makoto

2018-06-01

Cholinergic agonists evoke elevations of the cytoplasmic free-calcium concentration ([Ca 2+ ] i ) to stimulate fluid secretion in salivary glands. Salivary flow rates are significantly reduced in diabetic patients. However, it remains elusive how salivary secretion is impaired in diabetes. Here, we used an ex vivo submandibular gland perfusion technique to characterize the dependency of salivary flow rates on extracellular glucose concentration and activities of glucose transporters expressed in the glands. The cholinergic agonist carbachol (CCh) induced sustained fluid secretion, the rates of which were modulated by the extracellular glucose concentration in a biphasic manner. Both lowering the extracellular glucose concentration to less than 2.5 mM and elevating it to higher than 5 mM resulted in decreased CCh-induced fluid secretion. The CCh-induced salivary flow was suppressed by phlorizin, an inhibitor of the sodium-glucose cotransporter 1 (SGLT1) located basolaterally in submandibular acinar cells, which is altered at the protein expression level in diabetic animal models. Our data suggest that SGLT1-mediated glucose uptake in acinar cells is required to maintain the fluid secretion by sustaining Cl - secretion in real-time. High extracellular glucose levels may suppress the CCh-induced secretion of salivary fluid by altering the activities of ion channels and transporters downstream of [Ca 2+ ] i signals. © 2018 Eur J Oral Sci.

Comparative theoretical study of the structures and stabilities of four typical gadolinium carboxylates in different scintillator solvents.

PubMed

Huang, Pin-Wen

2016-03-01

The structural properties and stabilities of four typical gadolinium carboxylates (Gd-CBX) in toluene, linear alkyl benzene (LAB), and phenyl xylyl ethane (PXE) solvents were theoretically studied using density functional theory (DFT/B3LYP with the basis sets 6-311G(d) and MWB54) and the polarizable continuum model (PCM). The average Gd-ligand interaction energies (E int, corrected for dispersion) and the values of the energy gap between the highest occupied molecular orbital and lowest unoccupied molecular orbital (ΔHL) for the gadolinium complexes were calculated to compare the relative stabilities of the four Gd-CBX molecules in the three liquid scintillator solvents. According to the calculations, the values of E int and ΔHL for Gd-CBX in LAB are larger than the corresponding values in PXE and toluene. Gd-CBX may therefore be more compatible with LAB than with PXE and toluene. It was also found that, in the three scintillator solvents, the stabilities of the four Gd-CBX molecules increase in the order Gd-2EHA < Gd-2MVA < Gd-pivalate < Gd-TMHA.

A comparative study on the luminescence properties of Ce3+/Tb3+ doped Gd-based host nanomaterials

NASA Astrophysics Data System (ADS)

Jadhao, Charushila Vasant; Rani, Barkha; Sahu, Niroj Kumar

2018-04-01

A comparative study on the crystal phases and their respective luminescence behaviour of Gd3+ based host materials such as GdPO4, GdF3, GdVO4 and Gd2O3 sensitized with 7at.% Ce3+ and activated with 5 at.% Tb3+ have been reported. The nanomaterials were prepared by polyol method using ethylene glycol as solvent and found to have different crystal structures such as monoclinic, orthorhombic, tetragonal and cubic phase. Clear characteristics emission from Tb3+ has been observed in all the samples when excited in the absorption wavelength of Ce3+ and Gd3+ (˜280 nm). Among all the above materials, intense emission of Tb3+ is found in GdPO4 followed by GdF3, Gd2O3 and GdVO4 respectively. The Tb3+ emission is strongly influenced by the energy transfer process and crystal structure of the host materials and hence this study will be important for choosing suitable materials for display devices and biomedical applications.

CD38 Mediates Angiotensin II–Induced Intracellular Ca2+ Release in Rat Pulmonary Arterial Smooth Muscle Cells

PubMed Central

Lee, Suengwon; Paudel, Omkar; Jiang, Yongliang; Yang, Xiao-Ru

2015-01-01

CD38 is a multifunctional enzyme that catalyzes the formation of the endogenous Ca2+-mobilizing messengers cyclic ADP-ribose (cADPR) and nicotinic acid adenosine dinucleotide phosphate (NAADP) for the activation of ryanodine receptors (RyRs) of sarcoplasmic reticulum and NAADP-sensitive Ca2+ release channels in endolysosomes, respectively. It plays important roles in systemic vascular functions, but there is little information on CD38 in pulmonary arterial smooth muscle cells (PASMCs). Earlier studies suggested a redox-sensing role of CD38 in hypoxic pulmonary vasoconstriction. This study sought to characterize its roles in angiotensin II (Ang II)–induced Ca2+ release (AICR) in PASMCs. Examination of CD38 expression in various rat arteries found high levels of CD38 mRNA and protein in pulmonary arteries. The Ang II–elicited Ca2+ response consisted of extracellular Ca2+ influx and intracellular Ca2+ release in PASMCs. AICR activated in the absence of extracellular Ca2+ was reduced by pharmacological or siRNA inhibition of CD38, by the cADPR antagonist 8-bromo-cADPR or ryanodine, and by the NAADP antagonist Ned-19 or disruption of endolysosomal Ca2+ stores with the vacuolar H+-ATPase inhibitor bafilomycin A1. Suppression of AICR by the inhibitions of cADPR- and NAADP-dependent pathways were nonadditive, indicating interdependence of RyR- and NAADP-gated Ca2+ release. Furthermore, AICR was inhibited by the protein kinase C inhibitor staurosporine, the nonspecific NADPH oxidase (NOX) inhibitors apocynin and diphenyleneiodonium, the NOX2-specific inhibitor gp91ds-tat, and the scavenger of reactive oxygen species (ROS) tempol. These results provide the first evidence that Ang II activates CD38-dependent Ca2+ release via the NOX2-ROS pathway in PASMCs. PMID:25078456

DDPH ameliorated oxygen and glucose deprivation-induced injury in rat hippocampal neurons via interrupting Ca2+ overload and glutamate release.

PubMed

He, Zhi; Lu, Qing; Xu, Xulin; Huang, Lin; Chen, Jianguo; Guo, Lianjun

2009-01-28

Our previous work has demonstrated that DDPH (1-(2, 6-dimethylphenoxy)-2-(3, 4-dimethoxyphenylethylamino) propane hydrochloride), a competitive alpha(1)-adrenoceptor antagonist, could improve cognitive deficits, reduce histopathological damage and facilitate synaptic plasticity in vivo possibly via increasing NR2B (NMDA receptor 2B) expression and antioxidation of DDPH itself. The present study further evaluated effects of DDPH on OGD (Oxygen and glucose deprivation)-induced neuronal damage in rat primary hippocampal cells. The addition of DDPH to the cultured cells 12 h before OGD for 4 h significantly reduced neuronal damage as determined by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and LDH (lactate dehydrogenase) release experiments. The effects of DDPH on intracellular calcium concentration were explored by Fura-2 based calcium imaging techniques and results showed that DDPH at the dosages of 5 microM and 10 microM suppressed the increase of intracellular calcium ([Ca(2+)](i)) stimulated by 50 mM KCl in Ca(2+)-containing extracellular solutions. However, DDPH couldn't suppress the increase of [Ca(2+)](i) induced by both 50 microM glutamate in Ca(2+)-containing extracellular solutions and 20 microM ATP (Adenosine Triphosphate) in Ca(2+)-free solution. These results indicated that DDPH prevented [Ca(2+)](i) overload in hippocampal neurons by blocking Ca(2+) influx (voltage-dependent calcium channel) but not Ca(2+) mobilization from the intracellular Ca(2+) store in endoplasm reticulum (ER). We also demonstrated that DDPH could decrease glutamate release when hippocampal cells were subjected to OGD. These observations demonstrated that DDPH protected hippocampal neurons against OGD-induced damage by preventing the Ca(2+) influx and decreasing glutamate release.

Critical role of TRPP2 and TRPC1 channels in stretch-induced injury of blood-brain barrier endothelial cells.

PubMed

Berrout, Jonathan; Jin, Min; O'Neil, Roger G

2012-02-03

The microvessels of the brain are very sensitive to mechanical stresses such as observed in traumatic brain injury (TBI). Such stresses can quickly lead to dysfunction of the microvessel endothelial cells, including disruption of blood-brain barrier (BBB). It is now evident that elevation of cytosolic calcium levels ([Ca2+]i) can compromise the BBB integrity, however the mechanism by which mechanical injury can produce a [Ca2+]i increase in brain endothelial cells is unclear. To assess the effects of mechanical/stretch injury on [Ca2+]i signaling, mouse brain microvessel endothelial cells (bEnd3) were grown to confluency on elasticized membranes and [Ca2+]i monitored using fura 2 fluorescence imaging. Application of an injury, using a pressure/stretch pulse of 50 ms, induced a rapid transient increase in [Ca2+]i. In the absence of extracellular Ca2+, the injury-induced [Ca2+]i transient was greatly reduced, but not fully eliminated, while unloading of Ca2+ stores by thapsigargin treatment in the absence of extracellular Ca2+ abolished the injury transient. Application of LOE-908 and amiloride, TRPC and TRPP2 channel blockers, respectively, both reduced the transient [Ca2+]i increase. Further, siRNA knockdown assays directed at TRPC1 and TRPP2 expression also resulted in a reduction of the injury-induced [Ca2+]i response. In addition, stretch injury induced increases of NO production and actin stress fiber formation, both of which were markedly reduced upon treatment with LOE908 and/or amiloride. We conclude that mechanical injury of brain endothelial cells induces a rapid influx of calcium, mediated by TRPC1 and TRPP2 channels, which leads to NO synthesis and actin cytoskeletal rearrangement. Copyright © 2011. Published by Elsevier B.V.

A calcium influx is triggered and propagates in the zygote as a wavefront during in vitro fertilization of flowering plants.

PubMed

Antoine, A F; Faure, J E; Cordeiro, S; Dumas, C; Rougier, M; Feijó, J A

2000-09-12

In this paper, we report direct measurement of an influx of extracellular Ca(2+) induced by gamete fusion in flowering plants. This result was obtained during maize in vitro fertilization with the use of an extracellular Ca(2+)-selective vibrating probe. Ca(2+) influx recorded at the surface of isolated egg cells, with or without adhesion of a male sperm cell, was close to zero and stable over time. Gamete fusion, however, triggered a Ca(2+) influx in the vicinity of the sperm entry site with a delay of 1.8 +/- 0.6 sec. The Ca(2+) influx spread subsequently through the whole egg cell plasma membrane as a wavefront, progressing at an estimated rate of 1.13 micrometer.(-1). Once established, Ca(2+) influx intensities were sustained, monotonic and homogeneous over the whole egg cell, with an average peak influx of 14.92 pmol .cm(-2).(-1) and an average duration of 24.4 min. The wavefront spread of channel activation correlates well with the cytological modifications induced by fertilization, such as egg cell contraction, and with the cytosolic Ca(2+) ((c)[Ca(2+)]) elevation previously reported. Calcium influx was inhibited effectively by gadolinium, possibly implicating mechanosensitive channels. Furthermore, artificial influxes created by incubation with Ca(2+) ionophores mimicked some aspects of egg activation. Taken together, these results suggest that, during fertilization in higher plants, gamete membrane fusion starts the first embryonic events by channel opening and Ca(2+) influx. In turn, (c)[Ca(2+)] may work as a trigger and possibly a space and time coordinator of many aspects of egg activation.

Extracellular Ca2+ Sensing in Salivary Ductal Cells*

PubMed Central

Bandyopadhyay, Bidhan C.; Swaim, William D.; Sarkar, Ankana; Liu, Xibao; Ambudkar, Indu S.

2012-01-01

Ca2+ is secreted from the salivary acinar cells as an ionic constituent of primary saliva. Ions such as Na+ and Cl− get reabsorbed whereas primary saliva flows through the salivary ductal system. Although earlier studies have shown that salivary [Ca2+] decreases as it flows down the ductal tree into the oral cavity, ductal reabsorption of Ca2+ remains enigmatic. Here we report a potential role for the G protein-coupled receptor, calcium-sensing receptor (CSR), in the regulation of Ca2+ reabsorption by salivary gland ducts. Our data show that CSR is present in the apical region of ductal cells where it is co-localized with transient receptor potential canonical 3 (TRPC3). CSR is activated in isolated salivary gland ducts as well as a ductal cell line (SMIE) by altering extracellular [Ca2+] or by aromatic amino acid, l-phenylalanine (l-Phe, endogenous component of saliva), as well as neomycin. CSR activation leads to Ca2+ influx that, in polarized cells grown on a filter support, is initiated in the luminal region. We show that TRPC3 contributes to Ca2+ entry triggered by CSR activation. Further, stimulation of CSR in SMIE cells enhances the CSR-TRPC3 association as well as surface expression of TRPC3. Together our findings suggest that CSR could serve as a Ca2+ sensor in the luminal membrane of salivary gland ducts and regulate reabsorption of [Ca2+] from the saliva via TRPC3, thus contributing to maintenance of salivary [Ca2+]. CSR could therefore be a potentially important protective mechanism against formation of salivary gland stones (sialolithiasis) and infection (sialoadenitis). PMID:22778254

A calcium-sensing receptor mutation causing hypocalcemia disrupts a transmembrane salt bridge to activate β-arrestin-biased signaling.

PubMed

Gorvin, Caroline M; Babinsky, Valerie N; Malinauskas, Tomas; Nissen, Peter H; Schou, Anders J; Hanyaloglu, Aylin C; Siebold, Christian; Jones, E Yvonne; Hannan, Fadil M; Thakker, Rajesh V

2018-02-20

The calcium-sensing receptor (CaSR) is a G protein-coupled receptor (GPCR) that signals through G q/11 and G i/o to stimulate cytosolic calcium (Ca 2+ i ) and mitogen-activated protein kinase (MAPK) signaling to control extracellular calcium homeostasis. Studies of loss- and gain-of-function CASR mutations, which cause familial hypocalciuric hypercalcemia type 1 (FHH1) and autosomal dominant hypocalcemia type 1 (ADH1), respectively, have revealed that the CaSR signals in a biased manner. Thus, some mutations associated with FHH1 lead to signaling predominantly through the MAPK pathway, whereas mutations associated with ADH1 preferentially enhance Ca 2+ i responses. We report a previously unidentified ADH1-associated R680G CaSR mutation, which led to the identification of a CaSR structural motif that mediates biased signaling. Expressing CaSR R680G in HEK 293 cells showed that this mutation increased MAPK signaling without altering Ca 2+ i responses. Moreover, this gain of function in MAPK activity occurred independently of G q/11 and G i/o and was mediated instead by a noncanonical pathway involving β-arrestin proteins. Homology modeling and mutagenesis studies showed that the R680G CaSR mutation selectively enhanced β-arrestin signaling by disrupting a salt bridge formed between Arg 680 and Glu 767 , which are located in CaSR transmembrane domain 3 and extracellular loop 2, respectively. Thus, our results demonstrate CaSR signaling through β-arrestin and the importance of the Arg 680 -Glu 767 salt bridge in mediating signaling bias. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Cytosolic Calcium Coordinates Mitochondrial Energy Metabolism with Presynaptic Activity

PubMed Central

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

2012-01-01

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

Gadolinium oxide decorated multiwalled carbon nanotube/tridoped titania nanocomposites for improved dye degradation under simulated solar light irradiation

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

Mamba, Gcina; Nanotechnology and Water Sustainability Research Unit, College of Engineering, Science and Technology, University of South Africa Florida Science Campus, 1709 Florida; Mbianda, Xavier Yangkou

2016-03-15

Graphical abstract: Illustration of the collaborative effect between MWCNT-Gd and Gd,N,S-TiO{sub 2} towards degradation of AB 74. - Highlights: • MWCNT-Gd/tridoped titania was successfully prepared via a sol-gel method. • XPS revealed the presence of Ti, C, O, S, N and Gd in MWCNT-Gd/Gd,N,S-TiO{sub 2}. • MWCNT-Gd/Gd,N,S-TiO{sub 2} displayed 100% degradation of acid blue 74 in 150 min. • Over 60% TOC removal by MWCNT-Gd/Gd,N,S-TiO{sub 2}. - Abstract: Neodymium/gadolinium/europium, nitrogen and sulphur tridoped titania (Nd/Gd/Eu, N,S-TiO{sub 2}) was hybridised with pre-synthesised gadolinium oxide decorated multiwalled carbon nanotubes (MWCNT-Gd) using a sol–gel method. Subsequent to drying and calcination, composite photocatalysts: MWCNT-Gd/Nd,N,S-TiO{submore » 2}, MWCNT-Gd/Gd,N,S-TiO{sub 2} and MWCNT-Gd/Eu,N,S-TiO{sub 2}, were obtained and characterised using TEM, SEM-EDX, UV–vis, XPS, XRD and FT-IR. Acid blue 74 (AB74) was used as a model dye to investigate the photocatalytic degradation properties of the prepared materials under simulated solar light irradiation. Coupling the different tridoped titania with MWCNT-Gd enhanced their activity compared to MWCNT/TiO{sub 2}, MWCNT-Gd/TiO{sub 2} and MWCNT/Gd,N,S-TiO{sub 2}. MWCNT-Gd/Gd,N,S-TiO{sub 2} showed the highest activity towards AB74 degradation reaching 100% decolourisation after 150 min of irradiation. Total organic carbon analysis revealed that over 50% of the AB74 molecules were completely mineralised after 180 min of irradiation in the presence of MWCNT-Gd/Gd,N,S-TiO{sub 2}.« less

Mobiloization of intracellular calcium ions in chicken and rat lymphocytes induced by T cell mitogens.

PubMed

Gerilechaogetu; Narahara, Kiyoaki; Abe, Asaki; Kondo, Yasuhiro

2009-04-01

Cytosolic Ca(2+) is known to be an important factor in intracellular signaling pathways that regulate several cellular functions. The present study was designed to measure the intracellular concentrations of Ca(2+) ([Ca(2+)](i)) in T cell mitogen-stimulated chicken lymphocytes, and to compare the results with those in rat lymphocytes. [Ca(2+)](i) was increased in the thymocytes, splenocytes and bursacytes of chickens, and in the thymocytes and splenocytes of rats following exposure to the mitogens phytohaemagglutinin (PHA) and concanavalin A (ConA). Increases were greatest in the thymocytes followed by the splenocytes and bursacytes. The PHA-induced changes in the thymocytes and splenocytes were similar in chickens and rats, but the ConA-induced increases were significantly lower in the chickens than rats. Pretreatment with EGTA before the application of PHA and ConA completely suppressed the rise in [Ca(2+)](i) in all the chicken lymphocytes, indicating that the increases that occurred in PHA- and ConA-treated chicken lymphocytes could be entirely attributed to the influx of extracellular Ca(2+). On the other hand, the PHA- and ConA-induced increase in [Ca(2+)](i) in rat lymphocytes was not completely suppressed by EGTA, indicating the recruitment of Ca(2+) from the intracellular Ca(2+) pool. The results suggest species differences in the Ca(2+)-based responses to T cell mitogens between chicken lymphocytes and rat lymphocytes.

Effects of menadione, a reactive oxygen generator, on leukotriene secretion from RBL-2H3 cells.

PubMed

Kawamura, Fumio; Nakanishi, Mamoru; Hirashima, Naohide

2010-01-01

Reactive oxygen species (ROS) are produced in various cells and affect many biological processes. We previously reported that 2-methyl-1,4-naphtoquinone (menadione) inhibited Ca(2+) influx from the extracellular medium and exocytosis evoked by antigen stimulation in the mast cell line, RBL-2H3. Mast cells release various inflammatory mediators such as leukotrienes (LTs) and cytokines in addition to the exocytotic secretion of histamine. In this study, we investigated the effects of menadione on LT release in RBL-2H3. Treatment of RBL cells with menadione inhibited LTC(4) secretion induced by antigen stimulation. To elucidate the mechanism of this inhibition, we examined the effects of menadione on the activation process of 5-lipoxygenase that is responsible for the synthesis of LTs from arachidonic acid. Menadione did not affect the phosophorylation of mitogen activated protein (MAP) kinases, extracellular signal-regulated kinase (ERK) and p38, which regulates phosphorylation of 5-lipoxygenase. However, menadione inhibited the translocation of 5-lipoxygenase from the cytoplasm to the nuclear membrane. Together with the result that LT secretion was severely impaired in the absence of extracellular Ca2(2+), it is suggested that ROS produced by menadione inhibited LT secretion through impaired Ca2(2+) influx and 5-lipoxygenase translocation to the nuclear membrane.

Ionotropic P2X ATP Receptor Channels Mediate Purinergic Signaling in Mouse Odontoblasts

PubMed Central

Shiozaki, Yuta; Sato, Masaki; Kimura, Maki; Sato, Toru; Tazaki, Masakazu; Shibukawa, Yoshiyuki

2017-01-01

ATP modulates various functions in the dental pulp cells, such as intercellular communication and neurotransmission between odontoblasts and neurons, proliferation of dental pulp cells, and odontoblast differentiation. However, functional expression patterns and their biophysical properties of ionotropic ATP (P2X) receptors (P2X1–P2X7) in odontoblasts were still unclear. We examined these properties of P2X receptors in mouse odontoblasts by patch-clamp recordings. K+-ATP, nonselective P2X receptor agonist, induced inward currents in odontoblasts in a concentration-dependent manner. K+-ATP-induced currents were inhibited by P2X4 and P2X7 selective inhibitors (5-BDBD and KN62, respectively), while P2X1 and P2X3 inhibitors had no effects. P2X7 selective agonist (BzATP) induced inward currents dose-dependently. We could not observe P2X1, 2/3, 3 selective agonist (αβ-MeATP) induced currents. Amplitudes of K+-ATP-induced current were increased in solution without extracellular Ca2+, but decreased in Na+-free extracellular solution. In the absence of both of extracellular Na+ and Ca2+, K+-ATP-induced currents were completely abolished. K+-ATP-induced Na+ currents were inhibited by P2X7 inhibitor, while the Ca2+ currents were sensitive to P2X4 inhibitor. These results indicated that odontoblasts functionally expressed P2X4 and P2X7 receptors, which might play an important role in detecting extracellular ATP following local dental pulp injury. PMID:28163685

Ionotropic P2X ATP Receptor Channels Mediate Purinergic Signaling in Mouse Odontoblasts.

PubMed

Shiozaki, Yuta; Sato, Masaki; Kimura, Maki; Sato, Toru; Tazaki, Masakazu; Shibukawa, Yoshiyuki

2017-01-01

ATP modulates various functions in the dental pulp cells, such as intercellular communication and neurotransmission between odontoblasts and neurons, proliferation of dental pulp cells, and odontoblast differentiation. However, functional expression patterns and their biophysical properties of ionotropic ATP (P2X) receptors (P2X 1 -P2X 7 ) in odontoblasts were still unclear. We examined these properties of P2X receptors in mouse odontoblasts by patch-clamp recordings. K + -ATP, nonselective P2X receptor agonist, induced inward currents in odontoblasts in a concentration-dependent manner. K + -ATP-induced currents were inhibited by P2X 4 and P2X 7 selective inhibitors (5-BDBD and KN62, respectively), while P2X 1 and P2X 3 inhibitors had no effects. P2X 7 selective agonist (BzATP) induced inward currents dose-dependently. We could not observe P2X 1, 2/3, 3 selective agonist (αβ-MeATP) induced currents. Amplitudes of K + -ATP-induced current were increased in solution without extracellular Ca 2+ , but decreased in Na + -free extracellular solution. In the absence of both of extracellular Na + and Ca 2+ , K + -ATP-induced currents were completely abolished. K + -ATP-induced Na + currents were inhibited by P2X 7 inhibitor, while the Ca 2+ currents were sensitive to P2X 4 inhibitor. These results indicated that odontoblasts functionally expressed P2X 4 and P2X 7 receptors, which might play an important role in detecting extracellular ATP following local dental pulp injury.

Fructo-oligosaccharides and calcium absorption and retention in adolescent girls.

PubMed

Martin, Berdine R; Braun, Michelle M; Wigertz, Karin; Bryant, Rebecca; Zhao, Yongdong; Lee, WangHee; Kempa-Steczko, Ania; Weaver, Connie M

2010-08-01

Several studies have shown a positive effect of fructo-oligosaccharides on calcium absorption and retention in animals and humans. Effects of levels of these pre-biotics that can be functionally incorporated into manufactured foods, have not been studied in controlled feeding studies. This study was designed to evaluate the effect of 9 g/d of fructo-oligosaccharides as part of a controlled diet on calcium absorption and retention in adolescent girls. Fourteen healthy adolescent girls aged 11-13 y were studied in a metabolic setting for two 3-week periods separated by a 2-week washout period. In a randomized, double-blinded, crossover design, the teens received a diet containing either 9 g/d oligofructose-enriched inulin in a calcium-fortified cereal or the control cereal with no inulin. Both diets contained ~1500 mg calcium daily. Calcium retention was determined on the third week of each period. On day 14 of the diet period, fractional calcium absorption was determined from the enrichment of (44)Ca in 4-day urine collections. Calcium absorption (67 ± 3 vs. 66 ± 3%) and retention (409 ± 394 vs. 464 ± 241 mg/d) were not significantly different when diets contained 9 g/d oligofructose-enriched inulin or not in a calcium-fortified cereal. Daily consumption of cereal containing a combination of short- and long-chain fructo-oligosaccharides as part of a controlled diet did not benefit calcium absorption or retention in adolescent girls. Lack of response to the prebiotic in this cohort may relate to their already high calcium absorption efficiency.

Engineered contrast agents in a single structure for T1-T2 dual magnetic resonance imaging.

PubMed

Cabrera-García, Alejandro; Checa-Chavarria, Elisa; Pacheco-Torres, Jesús; Bernabeu-Sanz, Ángela; Vidal-Moya, Alejandro; Rivero-Buceta, Eva; Sastre, Germán; Fernández, Eduardo; Botella, Pablo

2018-04-05

The development of contrast agents (CAs) for Magnetic Resonance Imaging (MRI) with T1-T2 dual-mode relaxivity requires the accurate assembly of T1 and T2 magnetic centers in a single structure. In this context, we have synthesized a novel hybrid material by monitoring the formation of Prussian Blue analogue Gd(H2O)4[Fe(CN)6] nanoparticles with tailored shape (from nanocrosses to nanorods) and size, and further protection with a thin and homogeneous silica coating through hydrolysis and polymerization of silicate at neutral pH. The resulting Gd(H2O)4[Fe(CN)6]@SiO2 magnetic nanoparticles are very stable in biological fluids. Interestingly, this combination of Gd and Fe magnetic centers closely packed in the crystalline network promotes a magnetic synergistic effect, which results in significant improvement of longitudinal relaxivity with regards to soluble Gd3+ chelates, whilst keeping the high transversal relaxivity inherent to the iron component. As a consequence, this material shows excellent activity as MRI CA, improving positive and negative contrasts in T1- and T2-weighted MR images, both in in vitro (e.g., phantom) and in vivo (e.g., Sprague-Dawley rats) models. In addition, this hybrid shows a high biosafety profile and has strong ability to incorporate organic molecules on the surface with variable functionality, displaying great potential for further clinical application.

Investigating the beneficial traits of Trichoderma hamatum GD12 for sustainable agriculture—insights from genomics

PubMed Central

Studholme, David J.; Harris, Beverley; Le Cocq, Kate; Winsbury, Rebecca; Perera, Venura; Ryder, Lauren; Ward, Jane L.; Beale, Michael H.; Thornton, Chris R.; Grant, Murray

2013-01-01

Trichoderma hamatum strain GD12 is unique in that it can promote plant growth, activate biocontrol against pre- and post-emergence soil pathogens and can induce systemic resistance to foliar pathogens. This study extends previous work in lettuce to demonstrate that GD12 can confer beneficial agronomic traits to other plants, providing examples of plant growth promotion in the model dicot, Arabidopsis thaliana and induced foliar resistance to Magnaporthe oryzae in the model monocot rice. We further characterize the lettuce-T. hamatum interaction to show that bran extracts from GD12 and an N-acetyl-β-D-glucosamindase-deficient mutant differentially promote growth in a concentration dependent manner, and these differences correlate with differences in the small molecule secretome. We show that GD12 mycoparasitises a range of isolates of the pre-emergence soil pathogen Sclerotinia sclerotiorum and that this interaction induces a further increase in plant growth promotion above that conferred by GD12. To understand the genetic potential encoded by T. hamatum GD12 and to facilitate its use as a model beneficial organism to study plant growth promotion, induced systemic resistance and mycoparasitism we present de novo genome sequence data. We compare GD12 with other published Trichoderma genomes and show that T. hamatum GD12 contains unique genomic regions with the potential to encode novel bioactive metabolites that may contribute to GD12's agrochemically important traits. PMID:23908658

Comparison of the up-conversion photoluminescence for GAP, GAG and GAM phosphors

NASA Astrophysics Data System (ADS)

Deng, Taoli; Jiang, Xianbang

2018-04-01

GdAlO3:Er3+/Yb3+, Gd3Al5O12:Er3+/Yb3+ and Gd4Al2O9:Er3+/Yb3+ phosphors were prepared by co-precipitation. The effects for Gd2O3-Al2O3 composite oxides as the host materials with different crystal structures such as GdAlO3, Gd3Al5O12 and Gd4Al2O9 were investigated. It was found that the perovskite structured GdAlO3:Er3+/Yb3+ (GAP phosphor) could be obtained from the precursor when the calcination temperature was 1000 °C, while the garnet structured Gd3Al5O12:Er3+/Yb3+ (GAG phosphor) could be formed when the calcination temperature was 1300 °C, but the monoclinic-structured Gd4Al2O9:Er3+/Yb3+ (GAM phosphor) could be formed only when the calcination temperature was raised up to 1500 °C. The difference of the up-conversion photoluminescence (UCPL) spectra under 980 nm between the GAP, GAG and GAM phosphors was studied. The result showed that the UCPL intensity of the GAP phosphor was close to that of the GAM phosphor with much higher red-to-green intensity ratio than that of GAP phosphor. The UCPL intensity of GAG phosphor was the weakest among them. Finally, the factors which influenced on the UCPL of the GAP, GAG and GAM phosphors were discussed.

Chloride channels are necessary for full platelet phosphatidylserine exposure and procoagulant activity.

PubMed

Harper, M T; Poole, A W

2013-12-19

Platelets enhance thrombin generation at sites of vascular injury by exposing phosphatidylserine during necrosis-like cell death. Anoctamin 6 (Ano6) is required for Ca(2+)-dependent phosphatidylserine exposure and is defective in patients with Scott syndrome, a rare bleeding disorder. Ano6 may also form Cl(-) channels, though the role of Cl(-) fluxes in platelet procoagulant activity has not been explored. We found that Cl(-) channel blockers or removal of extracellular Cl(-) inhibited agonist-induced phosphatidylserine exposure. However, this was not due to direct inhibition of Ca(2+)-dependent scrambling since Ca(2+) ionophore-induced phosphatidylserine exposure was normal. This implies that the role of Ano6 in Ca(2+-)dependent PS exposure is likely to differ from any putative function of Ano6 as a Cl(-) channel. Instead, Cl(-) channel blockade inhibited agonist-induced Ca(2+) entry. Importantly, Cl(-) channel blockers also prevented agonist-induced membrane hyperpolarization, resulting in depolarization. We propose that Cl(-) entry through Cl(-) channels is required for this hyperpolarization, maintaining the driving force for Ca(2+) entry and triggering full phosphatidylserine exposure. This demonstrates a novel role for Cl(-) channels in controlling platelet death and procoagulant activity.

Ca2+ Modulation of ANF-RGC: New Signaling Paradigm Interlocked with Blood Pressure Regulation

PubMed Central

Duda, Teresa; Pertzev, Alexandre; Sharma, Rameshwar K.

2012-01-01

ANF-RGC is the prototype receptor membrane guanylate cyclase being both the receptor and the signal transducer of the most hypotensive hormones, ANF and BNP. It is a single trans-membrane protein. After binding these hormones at the extracellular domain, ANF-RGC at its intracellular domain signals the activation of the C-terminal catalytic module and accelerates the production of the second messenger, cyclic GMP, which controls blood pressure, cardiac vasculature, and fluid secretion. At present this is the sole transduction mechanism and the physiological function of ANF-RGC. Through comprehensive studies involving biochemistry, immunohistochemistry, and blood pressure measurements in mice with targeted gene deletions, the present study demonstrates a new signaling model of ANF-RGC that also controls blood pressure. In this model (1) ANF-RGC is not the transducer of ANF and BNP; (2) its extracellular domain is not used for signaling; and (3) the signal-flow is not downstream from the extracellular domain to the core catalytic domain. Instead, the signal is the intracellular Ca2+, which is translated at the site of its reception, at the core catalytic domain of ANF-RGC. A model for this Ca2+ signal transduction is diagrammed. It captures Ca2+ through its Ca2+ sensor myristoylated neurocalcin δ and up-regulates ANF-RGC activity with a K1/2 of 0.5 μM. The neurocalcin δ-modulated domain resides in the 849DIVGFTALSAESTPMQVV866 segment of ANF-RGC, which is a part of the core catalytic domain. Thereby, ANF-RGC is primed to receive, transmit and translate the Ca2+ signals into the generation of cyclic GMP at a rapid rate. The study defines a new paradigm of the membrane guanylate cyclase signaling, which is linked to the physiology of cardiac vasculature regulation and possibly also to fluid secretion. PMID:23088492

Mechanism of allosteric activation of TMEM16A/ANO1 channels by a commonly used chloride channel blocker

PubMed Central

Ta, Chau M; Adomaviciene, Aiste; Rorsman, Nils J G; Garnett, Hannah

2016-01-01

Background and Purpose Calcium‐activated chloride channels (CaCCs) play varied physiological roles and constitute potential therapeutic targets for conditions such as asthma and hypertension. TMEM16A encodes a CaCC. CaCC pharmacology is restricted to compounds with relatively low potency and poorly defined selectivity. Anthracene‐9‐carboxylic acid (A9C), an inhibitor of various chloride channel types, exhibits complex effects on native CaCCs and cloned TMEM16A channels providing both activation and inhibition. The mechanisms underlying these effects are not fully defined. Experimental Approach Patch‐clamp electrophysiology in conjunction with concentration jump experiments was employed to define the mode of interaction of A9C with TMEM16A channels. Key Results In the presence of high intracellular Ca2+, A9C inhibited TMEM16A currents in a voltage‐dependent manner by entering the channel from the outside. A9C activation, revealed in the presence of submaximal intracellular Ca2+ concentrations, was also voltage‐dependent. The electric distance of A9C inhibiting and activating binding site was ~0.6 in each case. Inhibition occurred according to an open‐channel block mechanism. Activation was due to a dramatic leftward shift in the steady‐state activation curve and slowed deactivation kinetics. Extracellular A9C competed with extracellular Cl−, suggesting that A9C binds deep in the channel's pore to exert both inhibiting and activating effects. Conclusions and Implications A9C is an open TMEM16A channel blocker and gating modifier. These effects require A9C to bind to a region within the pore that is accessible from the extracellular side of the membrane. These data will aid the future drug design of compounds that selectively activate or inhibit TMEM16A channels. PMID:26562072

Extracellular calcium regulates protein tyrosine phosphorylation through calcium-sensing receptor (CaSR) in stallion sperm.

PubMed

Macías-García, Beatriz; Rocha, Antonio; González-Fernández, Lauro

2016-03-01

Protein tyrosine phosphorylation (PY), a hallmark of sperm capacitation, is inhibited by extracellular calcium in stallion sperm. The objective of this study was to determine the presence and influence of the calcium-sensing receptor (CaSR) in this phenomenon. First, the presence of the CaSR was demonstrated in stallion sperm. We then tested its function in these gametes using its inhibitor NPS2143 or its agonist AC34356. Sperm were capacitated for 4 hr in modified Whitten's medium with 25 mM bicarbonate plus NPS2143 and 2.4 mM calcium or AC34356 alone, followed by analysis of PY. Inhibition of CaSR with NPS2143 prevented the calcium-dependent PY inhibition in a dose-dependent manner (5, 10, and 15 μM) whereas AC34356 (100 μM) inhibited PY similarly to calcium. Stallion sperm motility and viability significantly decreased in presence of 15 μM of NPS2143 whereas only sperm motility decreased with 100 μM of AC34356. CaSR function was also studied in the complete absence of calcium by including 2 mM ethylene glycol tetraacetic acid (EGTA); under these conditions, AC34356 again inhibited PY, but this time induced a significant increase in sperm motility. Inhibition of calmodulin by W-7 did not recover the AC34356-mediated PY inhibition. When stallion sperm were incubated under capacitating conditions (calcium, bicarbonate, plus bovine serum albumin) at elevated pH (7.9 or 8.5) AC34356 did not block PY. These results thus elucidate the effect of extracellular conditions on the regulation of CaSR, and point to its modulatory role on stallion sperm PY, motility, and viability. Mol. Reprod. Dev. 83: 236-245, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Chasing stress signals - Exposure to extracellular stimuli differentially affects the redox state of cell compartments in the wild type and signaling mutants of Botrytis cinerea.

PubMed

Marschall, Robert; Schumacher, Julia; Siegmund, Ulrike; Tudzynski, Paul

2016-05-01

Reactive oxygen species (ROS) are important molecules influencing intracellular developmental processes as well as plant pathogen interactions. They are produced at the infection site and affect the intracellular redox homeostasis. However, knowledge of ROS signaling pathways, their connection to other signaling cascades, and tools for the visualization of intra- and extracellular ROS levels and their impact on the redox state are scarce. By using the genetically encoded biosensor roGFP2 we studied for the first time the differences between the redox states of the cytosol, the intermembrane space of mitochondria and the ER in the filamentous fungus Botrytis cinerea. We showed that the ratio of oxidized to reduced glutathione inside of the cellular compartments differ and that the addition of hydrogen peroxide (H2O2), calcium chloride (CaCl2) and the fluorescent dye calcofluor white (CFW) have a direct impact on the cellular redox states. Dependent on the type of stress agents applied, the redox states were affected in the different cellular compartments in a temporally shifted manner. By integrating the biosensor in deletion mutants of bcnoxA, bcnoxB, bctrx1 and bcltf1 we further elucidated the putative roles of the different proteins in distinct stress-response pathways. We showed that the redox states of ΔbcnoxA and ΔbcnoxB display a wild-type pattern upon exposure to H2O2, but appear to be strongly affected by CaCl2 and CFW. Moreover, we demonstrated the involvement of the light-responsive transcription factor BcLtf1 in the maintenance of the redox state in the intermembrane space of the mitochondria. Finally, we report that CaCl2 as well as cell wall stress-inducing agents stimulate ROS production and that ΔbcnoxB produces significantly less ROS than the wild type and ΔbcnoxA. Copyright © 2016 Elsevier Inc. All rights reserved.

Cationic influences upon synaptic transmission at the hair cell-afferent fiber synapse of the frog

NASA Technical Reports Server (NTRS)

Cochran, S. L.

1995-01-01

The concentrations of inorganic cations (K+, Na+, and Ca2+) bathing the isolated frog labyrinth were varied in order to assess their role in influencing and mediating synaptic transmission at the hair cell-afferent fiber synapse. Experiments employed intracellular recordings of synaptic activity from VIIIth nerve afferents. Recordings were digitized continuously at 50 kHz, and excitatory postsynaptic potentials were detected and parameters quantified by computer algorithms. Particular attention was focused on cationic effects upon excitatory postsynaptic potential frequency of occurrence and excitatory postsynaptic potential amplitude, in order to discriminate between pre- and postsynaptic actions. Because the small size of afferents preclude long term stable recordings, alterations in cationic concentrations were applied transiently and their peak effects on synaptic activity were assessed. Increases in extracellular K+ concentration of a few millimolar produced a large increase in the frequency of occurrence of excitatory postsynaptic potentials with little change in amplitude, indicating that release of transmitter from the hair cell is tightly coupled to its membrane potential. Increasing extracellular Na+ concentration resulted in an increase in excitatory postsynaptic potential amplitude with no significant change in excitatory postsynaptic potential frequency of occurrence, suggesting that the transmitter-gated subsynaptic channel conducts Na+ ions. Decreases in extracellular Ca2+ concentration had little effect upon excitatory postsynaptic potential frequency, but increased excitatory postsynaptic potential frequency and amplitude. These findings suggest that at higher concentrations Ca2+ act presynaptically to prevent transmitter release and postsynaptically to prevent Na+ influx during the generation of the excitatory postsynaptic potential. The influences of these ions on synaptic activity at this synapse are remarkably similar to those reported at the vertebrate neuromuscular junction. The major differences between these two synapses are the neurotransmitters and the higher resting release rate and higher sensitivity of release to increased K+ concentrations of the hair cells over that of motor nerve terminals. These differences reflect the functional roles of the two synapses: the motor nerve terminal response in an all-or-nothing signal consequent from action potential invasion, while the hair cell releases transmitter in a graded fashion, proportionate to the extent of stereocilial deflection. Despite these differences between the two junctions, the similar actions of these elemental cations upon synaptic function at each implies that these ions may participate similarly in the operations of other synapses, independent of the neurotransmitter type.(ABSTRACT TRUNCATED AT 400 WORDS).