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Sample records for intracellular calcium spikes

  1. Intracellular calcium spikes in rat suprachiasmatic nucleus neurons induced by BAPTA-based calcium dyes.

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    Jin Hee Hong

    Full Text Available BACKGROUND: Circadian rhythms in spontaneous action potential (AP firing frequencies and in cytosolic free calcium concentrations have been reported for mammalian circadian pacemaker neurons located within the hypothalamic suprachiasmatic nucleus (SCN. Also reported is the existence of "Ca(2+ spikes" (i.e., [Ca(2+](c transients having a bandwidth of 10 approximately 100 seconds in SCN neurons, but it is unclear if these SCN Ca(2+ spikes are related to the slow circadian rhythms. METHODOLOGY/PRINCIPAL FINDINGS: We addressed this issue based on a Ca(2+ indicator dye (fluo-4 and a protein Ca(2+ sensor (yellow cameleon. Using fluo-4 AM dye, we found spontaneous Ca(2+ spikes in 18% of rat SCN cells in acute brain slices, but the Ca(2+ spiking frequencies showed no day/night variation. We repeated the same experiments with rat (and mouse SCN slice cultures that expressed yellow cameleon genes for a number of different circadian phases and, surprisingly, spontaneous Ca(2+ spike was barely observed (<3%. When fluo-4 AM or BAPTA-AM was loaded in addition to the cameleon-expressing SCN cultures, however, the number of cells exhibiting Ca(2+ spikes was increased to 13 approximately 14%. CONCLUSIONS/SIGNIFICANCE: Despite our extensive set of experiments, no evidence of a circadian rhythm was found in the spontaneous Ca(2+ spiking activity of SCN. Furthermore, our study strongly suggests that the spontaneous Ca(2+ spiking activity is caused by the Ca(2+ chelating effect of the BAPTA-based fluo-4 dye. Therefore, this induced activity seems irrelevant to the intrinsic circadian rhythm of [Ca(2+](c in SCN neurons. The problems with BAPTA based dyes are widely known and our study provides a clear case for concern, in particular, for SCN Ca(2+ spikes. On the other hand, our study neither invalidates the use of these dyes as a whole, nor undermines the potential role of SCN Ca(2+ spikes in the function of SCN.

  2. Cytoplasmic tail of coronavirus spike protein has intracellular

    Indian Academy of Sciences (India)

    Intracellular trafficking and localization studies of spike protein from SARS and OC43 showed that SARS spikeprotein is localized in the ER or ERGIC compartment and OC43 spike protein is predominantly localized in thelysosome. Differential localization can be explained by signal sequence. The sequence alignment ...

  3. Stochastic models of intracellular calcium signals

    Energy Technology Data Exchange (ETDEWEB)

    Rüdiger, Sten, E-mail: sten.ruediger@physik.hu-berlin.de

    2014-01-10

    Cellular signaling operates in a noisy environment shaped by low molecular concentrations and cellular heterogeneity. For calcium release through intracellular channels–one of the most important cellular signaling mechanisms–feedback by liberated calcium endows fluctuations with critical functions in signal generation and formation. In this review it is first described, under which general conditions the environment makes stochasticity relevant, and which conditions allow approximating or deterministic equations. This analysis provides a framework, in which one can deduce an efficient hybrid description combining stochastic and deterministic evolution laws. Within the hybrid approach, Markov chains model gating of channels, while the concentrations of calcium and calcium binding molecules (buffers) are described by reaction–diffusion equations. The article further focuses on the spatial representation of subcellular calcium domains related to intracellular calcium channels. It presents analysis for single channels and clusters of channels and reviews the effects of buffers on the calcium release. For clustered channels, we discuss the application and validity of coarse-graining as well as approaches based on continuous gating variables (Fokker–Planck and chemical Langevin equations). Comparison with recent experiments substantiates the stochastic and spatial approach, identifies minimal requirements for a realistic modeling, and facilitates an understanding of collective channel behavior. At the end of the review, implications of stochastic and local modeling for the generation and properties of cell-wide release and the integration of calcium dynamics into cellular signaling models are discussed.

  4. Intracellular calcium homeostasis and signaling.

    Science.gov (United States)

    Brini, Marisa; Calì, Tito; Ottolini, Denis; Carafoli, Ernesto

    2013-01-01

    Ca(2+) is a universal carrier of biological information: it controls cell life from its origin at fertilization to its end in the process of programmed cell death. Ca(2+) is a conventional diffusible second messenger released inside cells by the interaction of first messengers with plasma membrane receptors. However, it can also penetrate directly into cells to deliver information without the intermediation of first or second messengers. Even more distinctively, Ca(2+) can act as a first messenger, by interacting with a plasma membrane receptor to set in motion intracellular signaling pathways that involve Ca(2+) itself. Perhaps the most distinctive property of the Ca(2+) signal is its ambivalence: while essential to the correct functioning of cells, Ca(2+) becomes an agent that mediates cell distress, or even (toxic) cell death, if its concentration and movements inside cells are not carefully tuned. Ca(2+) is controlled by reversible complexation to specific proteins, which could be pure Ca(2+) buffers, or which, in addition to buffering Ca(2+), also decode its signal to pass it on to targets. The most important actors in the buffering of cell Ca(2+) are proteins that transport it across the plasma membrane and the membrane of the organelles: some have high Ca(2+) affinity and low transport capacity (e.g., Ca(2+) pumps), others have opposite properties (e.g., the Ca(2+) uptake system of mitochondria). Between the initial event of fertilization, and the terminal event of programmed cell death, the Ca(2+) signal regulates the most important activities of the cell, from the expression of genes, to heart and muscle contraction and other motility processes, to diverse metabolic pathways involved in the generation of cell fuels.

  5. Intracellular sphingosine releases calcium from lysosomes

    Science.gov (United States)

    Höglinger, Doris; Haberkant, Per; Aguilera-Romero, Auxiliadora; Riezman, Howard; Porter, Forbes D; Platt, Frances M; Galione, Antony; Schultz, Carsten

    2015-01-01

    To elucidate new functions of sphingosine (Sph), we demonstrate that the spontaneous elevation of intracellular Sph levels via caged Sph leads to a significant and transient calcium release from acidic stores that is independent of sphingosine 1-phosphate, extracellular and ER calcium levels. This photo-induced Sph-driven calcium release requires the two-pore channel 1 (TPC1) residing on endosomes and lysosomes. Further, uncaging of Sph leads to the translocation of the autophagy-relevant transcription factor EB (TFEB) to the nucleus specifically after lysosomal calcium release. We confirm that Sph accumulates in late endosomes and lysosomes of cells derived from Niemann-Pick disease type C (NPC) patients and demonstrate a greatly reduced calcium release upon Sph uncaging. We conclude that sphingosine is a positive regulator of calcium release from acidic stores and that understanding the interplay between Sph homeostasis, calcium signaling and autophagy will be crucial in developing new therapies for lipid storage disorders such as NPC. DOI: http://dx.doi.org/10.7554/eLife.10616.001 PMID:26613410

  6. Calcium spikes and calcium plateaux evoked by differential polarization in dendrites of turtle motoneurones in vitro

    DEFF Research Database (Denmark)

    Hounsgaard, J; Kiehn, O

    1993-01-01

    The ability of dendrites in turtle motoneurones to support calcium spikes and calcium plateaux was investigated using differential polarization by applied electric fields. 2. Electric fields were generated by passing current through transverse slices of the turtle spinal cord between two plate......+ spikes and Ca2+ plateaux are present in dendrites of spinal motoneurones of the turtle....

  7. Intracellular transport of recombinant coronavirus spike proteins: implications for virus assembly

    NARCIS (Netherlands)

    Horzinek, M.C.; Vennema, H.; Heijnen, L.; Zijderveld, A.; Spaan, W.J.M.

    1990-01-01

    Coronavirus spike protein genes were expressed in vitro by using the recombinant vaccinia virus expression system. Recombinant spike proteins were expressed at the cell surface and induced cell fusion in a host-cell-dependent fashion. The intracellular transport of recombinant spike proteins was

  8. Cytoplasmic tail of Coronavirus spike protein has intracellular ...

    Indian Academy of Sciences (India)

    58

    Transfection ability of YFP tagged spike protein constructs are much more efficient. 220 compared to wild type spike construct, the reasons for which are unclear (data not. 221 shown). Because of efficient detection of YFP fluorescence and the limitations of spike. 222 specific antibodies, we decided to use the YFP tagged ...

  9. Cadmium Induces Transcription Independently of Intracellular Calcium Mobilization

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    Tvermoes, Brooke E.; Bird, Gary S.; Freedman, Jonathan H.

    2011-01-01

    Background Exposure to cadmium is associated with human pathologies and altered gene expression. The molecular mechanisms by which cadmium affects transcription remain unclear. It has been proposed that cadmium activates transcription by altering intracellular calcium concentration ([Ca2+]i) and disrupting calcium-mediated intracellular signaling processes. This hypothesis is based on several studies that may be technically problematic; including the use of BAPTA chelators, BAPTA-based fluorescent sensors, and cytotoxic concentrations of metal. Methodology/Principal Finding In the present report, the effects of cadmium on [Ca2+]i under non-cytotoxic and cytotoxic conditions was monitored using the protein-based calcium sensor yellow cameleon (YC3.60), which was stably expressed in HEK293 cells. In HEK293 constitutively expressing YC3.60, this calcium sensor was found to be insensitive to cadmium. Exposing HEK293::YC3.60 cells to non-cytotoxic cadmium concentrations was sufficient to induce transcription of cadmium-responsive genes but did not affect [Ca2+]i mobilization or increase steady-state mRNA levels of calcium-responsive genes. In contrast, exposure to cytotoxic concentrations of cadmium significantly reduced intracellular calcium stores and altered calcium-responsive gene expression. Conclusions/Significance These data indicate that at low levels, cadmium induces transcription independently of intracellular calcium mobilization. The results also support a model whereby cytotoxic levels of cadmium activate calcium-responsive transcription as a general response to metal-induced intracellular damage and not via a specific mechanism. Thus, the modulation of intracellular calcium may not be a primary mechanism by which cadmium regulates transcription. PMID:21694771

  10. Cytoplasmic tail of coronavirus spike protein has intracellular ...

    Indian Academy of Sciences (India)

    2017-04-18

    Apr 18, 2017 ... if the histidine residue is protonated. Lontok et al., in their chimeric S protein studies used C terminal 11 amino acids of SARS-S protein attached to the plasma membrane re- porter protein VSV-G to show KXHXX motif is an intra- cellular localization signal for SARS, and the intracellular distribution closely ...

  11. Intracellular calcium levels can regulate Importin-dependent nuclear import

    International Nuclear Information System (INIS)

    Kaur, Gurpreet; Ly-Huynh, Jennifer D.; Jans, David A.

    2014-01-01

    Highlights: • High intracellular calcium inhibits Impα/β1- or Impβ1-dependent nuclear protein import. • The effect of Ca 2+ on nuclear import does not relate to changes in the nuclear pore. • High intracellular calcium can result in mislocalisation of Impβ1, Ran and RCC1. - Abstract: We previously showed that increased intracellular calcium can modulate Importin (Imp)β1-dependent nuclear import of SRY-related chromatin remodeling proteins. Here we extend this work to show for the first time that high intracellular calcium inhibits Impα/β1- or Impβ1-dependent nuclear protein import generally. The basis of this relates to the mislocalisation of the transport factors Impβ1 and Ran, which show significantly higher nuclear localization in contrast to various other factors, and RCC1, which shows altered subnuclear localisation. The results here establish for the first time that intracellular calcium modulates conventional nuclear import through direct effects on the nuclear transport machinery

  12. Calcium, channels, intracellular signaling and autoimmunity.

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    Izquierdo, Jorge-Hernán; Bonilla-Abadía, Fabio; Cañas, Carlos A; Tobón, Gabriel J

    2014-01-01

    Calcium (Ca²⁺) is an important cation able to function as a second messenger in different cells of the immune system, particularly in B and T lymphocytes, macrophages and mastocytes, among others. Recent discoveries related to the entry of Ca²⁺ through the store-operated calcium entry (SOCE) has opened a new investigation area about the cell destiny regulated by Ca²⁺ especially in B and T lymphocytes. SOCE acts through calcium-release-activated calcium (CRAC) channels. The function of CRAC depends of two recently discovered regulators: the Ca²⁺ sensor in the endoplasmic reticulum or stromal interaction molecule (STIM-1) and one subunit of CRAC channels called Orai1. This review focuses on the role of Ca²⁺ signals in B and T lymphocytes functions, the signalling pathways leading to Ca²⁺ influx, and the relationship between Ca²⁺ signals and autoimmune diseases. Copyright © 2013 Elsevier España, S.L. All rights reserved.

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

    OpenAIRE

    Petrou, Terry; Olsen, Herv?r L.; Thrasivoulou, Christopher; Masters, John R.; Ashmore, Jonathan F.; Ahmed, Aamir

    2017-01-01

    Free intracellular calcium ([Ca2+]i), in addition to being an important second messenger, is a key regulator of many cellular processes including the cell membrane potential, proliferation and apoptosis. In many cases, the mobilization of [Ca2+]i is controlled by intracellular store activation and calcium influx. We have investigated the effect of several ion channel modulators, which have been used to treat a range of human diseases, on [Ca2+]i release, by ratiometric calcium imaging. We sho...

  14. FLIPR assays of intracellular calcium in GPCR drug discovery

    DEFF Research Database (Denmark)

    Hansen, Kasper Bø; Bräuner-Osborne, Hans

    2009-01-01

    Fluorescent dyes sensitive to changes in intracellular calcium have become increasingly popular in G protein-coupled receptor (GPCR) drug discovery for several reasons. First of all, the assays using the dyes are easy to perform and are of low cost compared to other assays. Second, most non...

  15. Vasomotion dynamics following calcium spiking depend on both cell signalling and limited constriction velocity in rat mesenteric small arteries

    NARCIS (Netherlands)

    VanBavel, Ed; van der Meulen, Esther T.; Spaan, Jos A. E.

    2008-01-01

    Vascular smooth muscle cell contraction depends on intracellular calcium. However, calcium-contraction coupling involves a complex array of intracellular processes. Quantitating the dynamical relation between calcium perturbations and resulting changes in tone may help identifying these processes.

  16. Resveratrol Interferes with Fura-2 Intracellular Calcium Measurements.

    Science.gov (United States)

    Kopp, Richard F; Leech, Colin A; Roe, Michael W

    2014-03-01

    Resveratrol, a naturally occurring polyphenol found in some fruits and especially in grapes, has been reported to provide diverse health benefits. Resveratrol's mechanism of action is the subject of many investigations, and some studies using the ratiometric calcium indicator Fura-2 suggest that it modulates cellular calcium responses. In the current study, contradictory cellular calcium responses to resveratrol applied at concentrations exceeding 10 μM were observed during in vitro imaging studies depending on the calcium indicator used, with Fura-2 indicating an increase in intracellular calcium while Fluo-4 and the calcium biosensor YC3.60 indicated no response. When cells loaded with Fura-2 were treated with 100 μM resveratrol, excitation at 340 nm resulted in a large intensity increase at 510 nm, but the expected concurrent decline with 380 nm excitation was not observed. Pre-treatment of cells with the calcium chelator BAPTA-AM did not prevent a rise in the 340/380 ratio when resveratrol was present, but it did prevent an increase in 340/380 when ATP was applied, suggesting that the resveratrol response was an artifact. Cautious data interpretation is recommended from imaging experiments using Fura-2 concurrently with resveratrol in calcium imaging experiments.

  17. Expanding the neuron's calcium signaling repertoire: intracellular calcium release via voltage-induced PLC and IP3R activation.

    Directory of Open Access Journals (Sweden)

    Stefanie Ryglewski

    2007-04-01

    Full Text Available Neuronal calcium acts as a charge carrier during information processing and as a ubiquitous intracellular messenger. Calcium signals are fundamental to numerous aspects of neuronal development and plasticity. Specific and independent regulation of these vital cellular processes is achieved by a rich bouquet of different calcium signaling mechanisms within the neuron, which either can operate independently or may act in concert. This study demonstrates the existence of a novel calcium signaling mechanism by simultaneous patch clamping and calcium imaging from acutely isolated central neurons. These neurons possess a membrane voltage sensor that, independent of calcium influx, causes G-protein activation, which subsequently leads to calcium release from intracellular stores via phospholipase C and inositol 1,4,5-trisphosphate receptor activation. This allows neurons to monitor activity by intracellular calcium release without relying on calcium as the input signal and opens up new insights into intracellular signaling, developmental regulation, and information processing in neuronal compartments lacking calcium channels.

  18. Biophysical properties and computational modeling of calcium spikes in serotonergic neurons of the dorsal raphe nucleus.

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    Tuckwell, Henry C

    2013-06-01

    Serotonergic neurons of the dorsal raphe nuclei, with their extensive innervation of nearly the whole brain have important modulatory effects on many cognitive and physiological processes. They play important roles in clinical depression and other psychiatric disorders. In order to quantify the effects of serotonergic transmission on target cells it is desirable to construct computational models and to this end these it is necessary to have details of the biophysical and spike properties of the serotonergic neurons. Here several basic properties are reviewed with data from several studies since the 1960s to the present. The quantities included are input resistance, resting membrane potential, membrane time constant, firing rate, spike duration, spike and afterhyperpolarization (AHP) amplitude, spike threshold, cell capacitance, soma and somadendritic areas. The action potentials of these cells are normally triggered by a combination of sodium and calcium currents which may result in autonomous pacemaker activity. We here analyse the mechanisms of high-threshold calcium spikes which have been demonstrated in these cells the presence of TTX (tetrodotoxin). The parameters for calcium dynamics required to give calcium spikes are quite different from those for regular spiking which suggests the involvement of restricted parts of the soma-dendritic surface as has been found, for example, in hippocampal neurons. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  19. The mechanical environment modulates intracellular calcium oscillation activities of myofibroblasts.

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    Charles Godbout

    Full Text Available Myofibroblast contraction is fundamental in the excessive tissue remodeling that is characteristic of fibrotic tissue contractures. Tissue remodeling during development of fibrosis leads to gradually increasing stiffness of the extracellular matrix. We propose that this increased stiffness positively feeds back on the contractile activities of myofibroblasts. We have previously shown that cycles of contraction directly correlate with periodic intracellular calcium oscillations in cultured myofibroblasts. We analyze cytosolic calcium dynamics using fluorescent calcium indicators to evaluate the possible impact of mechanical stress on myofibroblast contractile activity. To modulate extracellular mechanics, we seeded primary rat subcutaneous myofibroblasts on silicone substrates and into collagen gels of different elastic modulus. We modulated cell stress by cell growth on differently adhesive culture substrates, by restricting cell spreading area on micro-printed adhesive islands, and depolymerizing actin with Cytochalasin D. In general, calcium oscillation frequencies in myofibroblasts increased with increasing mechanical challenge. These results provide new insight on how changing mechanical conditions for myofibroblasts are encoded in calcium oscillations and possibly explain how reparative cells adapt their contractile behavior to the stresses occurring in normal and pathological tissue repair.

  20. Role of intracellular calcium in cellular volume regulation

    International Nuclear Information System (INIS)

    Wong, S.M.; Chase, H.S. Jr.

    1986-01-01

    We investigated the role of intracellular calcium in epithelial cell volume regulation using cells isolated from the toad urinary bladder. A suspension of cells was prepared by treatment of the bladder with collagenase followed by ethyleneglycol-bis(beta-aminoethylether)-N,N'-tetraacetic acid. The cells retained their ion-transporting capabilities: ouabain (1 mM) and amiloride (10 microM) inhibited cellular uptake of 86 Rb and 22 Na, respectively. Using a Coulter counter to measure cellular volume, we found that we could swell cells either by reducing the extracellular osmolality or by adding the permeant solute urea (45 mM) isosmotically. Under both conditions, cells first swelled and then returned to their base-line volume, in spite of the continued presence of the stimulus to swell. Volume regulation was inhibited when cells were swelled at low extracellular [Ca] (100 nM) and was retarded in cells preloaded with the calcium buffer quin 2. Swelling increased the intracellular free calcium concentration ([Ca]i), as measured by quin 2 fluorescence: [Ca]i increased 35 +/- 9 nM (n = 6) after hypotonic swelling and 42 +/- 3 nM (n = 3) after urea swelling. Reducing extracellular [Ca] to less than 100 nM prevented the swelling-induced increase in [Ca]i, suggesting that the source of the increase in [Ca]i was extracellular. This result was confirmed in measurements of cellular uptake of 45Ca: the rate of uptake was significantly higher in swollen cells compared with control (1.1 +/- 0.2 vs. 0.4 +/- 0.1 fmol . cell-1 X 5 min-1). Our experiments provide the first demonstration that cellular swelling increases [Ca]i. This increase is likely to play a critical role in cellular volume regulation

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

    Science.gov (United States)

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

    2017-02-01

    Free intracellular calcium ([Ca 2+ ] i ), in addition to being an important second messenger, is a key regulator of many cellular processes including cell membrane potential, proliferation, and apoptosis. In many cases, the mobilization of [Ca 2+ ] i is controlled by intracellular store activation and calcium influx. We have investigated the effect of several ion channel modulators, which have been used to treat a range of human diseases, on [Ca 2+ ] i release, by ratiometric calcium imaging. We show that six such modulators [amiodarone (Ami), dofetilide, furosemide (Fur), minoxidil (Min), loxapine (Lox), and Nicorandil] initiate release of [Ca 2+ ] i in prostate and breast cancer cell lines, PC3 and MCF7, respectively. Whole-cell currents in PC3 cells were inhibited by the compounds tested in patch-clamp experiments in a concentration-dependent manner. In all cases [Ca 2+ ] i was increased by modulator concentrations comparable to those used clinically. The increase in [Ca 2+ ] i in response to Ami, Fur, Lox, and Min was reduced significantly (P calcium was reduced to nM concentration by chelation with EGTA. The data suggest that many ion channel regulators mobilize [Ca 2+ ] i We suggest a mechanism whereby calcium-induced calcium release is implicated; such a mechanism may be important for understanding the action of these compounds. Copyright © 2017 by The Author(s).

  2. Allopregnanolone-induced rise in intracellular calcium in embryonic hippocampal neurons parallels their proliferative potential

    Directory of Open Access Journals (Sweden)

    Brinton Roberta

    2008-12-01

    Full Text Available Abstract Background Factors that regulate intracellular calcium concentration are known to play a critical role in brain function and neural development, including neural plasticity and neurogenesis. We previously demonstrated that the neurosteroid allopregnanolone (APα; 5α-pregnan-3α-ol-20-one promotes neural progenitor proliferation in vitro in cultures of rodent hippocampal and human cortical neural progenitors, and in vivo in triple transgenic Alzheimer's disease mice dentate gyrus. We also found that APα-induced proliferation of neural progenitors is abolished by a calcium channel blocker, nifedipine, indicating a calcium dependent mechanism for the proliferation. Methods In the present study, we investigated the effect of APα on the regulation of intracellular calcium concentration in E18 rat hippocampal neurons using ratiometric Fura2-AM imaging. Results Results indicate that APα rapidly increased intracellular calcium concentration in a dose-dependent and developmentally regulated manner, with an EC50 of 110 ± 15 nM and a maximal response occurring at three days in vitro. The stereoisomers 3β-hydroxy-5α-hydroxy-pregnan-20-one, and 3β-hydroxy-5β-hydroxy-pregnan-20-one, as well as progesterone, were without significant effect. APα-induced intracellular calcium concentration increase was not observed in calcium depleted medium and was blocked in the presence of the broad spectrum calcium channel blocker La3+, or the L-type calcium channel blocker nifedipine. Furthermore, the GABAA receptor blockers bicuculline and picrotoxin abolished APα-induced intracellular calcium concentration rise. Conclusion Collectively, these data indicate that APα promotes a rapid, dose-dependent, stereo-specific, and developmentally regulated increase of intracellular calcium concentration in rat embryonic hippocampal neurons via a mechanism that requires both the GABAA receptor and L-type calcium channel. These data suggest that AP

  3. Vitamin D is positively associated with sperm motility and increases intracellular calcium in human spermatozoa

    DEFF Research Database (Denmark)

    Blomberg Jensen, Martin; Bjerrum, Poul J; Jessen, Torben E

    2011-01-01

    BACKGROUND The vitamin D receptor (VDR) is expressed in human spermatozoa, and VDR-knockout mice and vitamin D (VD) deficiency in rodents results in impaired fertility, low sperm counts and a low number of motile spermatozoa. We investigated the role of activated VD (1,25(OH)(2)D(3)) in human...... spermatozoa and whether VD serum levels are associated with semen quality. METHODS Cross-sectional association study of semen quality and VD serum level in 300 men from the general population, and in vitro studies on spermatozoa from 40 men to investigate the effects of VD on intracellular calcium, sperm......M). 1,25(OH)(2)D(3) increased intracellular calcium concentration in human spermatozoa through VDR-mediated calcium release from an intracellular calcium storage, increased sperm motility and induced the acrosome reaction in vitro. CONCLUSIONS 1,25(OH)(2)D(3) increased intracellular calcium...

  4. The calcium feedback loop and T cell activation: how cytoskeleton networks control intracellular calcium flux.

    Science.gov (United States)

    Joseph, Noah; Reicher, Barak; Barda-Saad, Mira

    2014-02-01

    During T cell activation, the engagement of a T cell with an antigen-presenting cell (APC) results in rapid cytoskeletal rearrangements and a dramatic increase of intracellular calcium (Ca(2+)) concentration, downstream to T cell antigen receptor (TCR) ligation. These events facilitate the organization of an immunological synapse (IS), which supports the redistribution of receptors, signaling molecules and organelles towards the T cell-APC interface to induce downstream signaling events, ultimately supporting T cell effector functions. Thus, Ca(2+) signaling and cytoskeleton rearrangements are essential for T cell activation and T cell-dependent immune response. Rapid release of Ca(2+) from intracellular stores, e.g. the endoplasmic reticulum (ER), triggers the opening of Ca(2+) release-activated Ca(2+) (CRAC) channels, residing in the plasma membrane. These channels facilitate a sustained influx of extracellular Ca(2+) across the plasma membrane in a process termed store-operated Ca(2+) entry (SOCE). Because CRAC channels are themselves inhibited by Ca(2+) ions, additional factors are suggested to enable the sustained Ca(2+) influx required for T cell function. Among these factors, we focus here on the contribution of the actin and microtubule cytoskeleton. The TCR-mediated increase in intracellular Ca(2+) evokes a rapid cytoskeleton-dependent polarization, which involves actin cytoskeleton rearrangements and microtubule-organizing center (MTOC) reorientation. Here, we review the molecular mechanisms of Ca(2+) flux and cytoskeletal rearrangements, and further describe the way by which the cytoskeletal networks feedback to Ca(2+) signaling by controlling the spatial and temporal distribution of Ca(2+) sources and sinks, modulating TCR-dependent Ca(2+) signals, which are required for an appropriate T cell response. This article is part of a Special Issue entitled: Reciprocal influences between cell cytoskeleton and membrane channels, receptors and transporters

  5. Transport phenomena in intracellular calcium dynamics driven by non-Gaussian noises

    Science.gov (United States)

    Lin, Ling; Duan, Wei-Long

    2018-02-01

    The role of non-Gaussian noises on transport characteristic of Ca2+ in intracellular calcium oscillation system driven by non-Gaussian noises is studied by means of second-order stochastic Runge-Kutta type algorithm. The statistical properties of velocity of cytosolic and calcium store's Ca2+ concentration are simulated. The results exhibit, as parameter p(which is used to control the degree of the departure from the non-Gaussian noise and Gaussian noise.)increases, calcium in cytosol shows positive, zero, and negative transport, but in calcium store always hold positive value. As non-Gaussian noises increase, calcium in cytosol appears negative and zero transport, and in calcium store appears positive transport. As correlation time of non-Gaussian noises varies, calcium in both cytosol and calcium store occur negative, zero, and positive transport.

  6. The effect of intracellular calcium oscillations on fluid secretion in airway epithelium.

    Science.gov (United States)

    Warren, N J; Tawhai, M H; Crampin, E J

    2010-08-07

    Airway epithelium has been shown to elicit fluid secretion after a rise in intracellular calcium. This rise in intracellular calcium has been shown to display complex oscillations in many species after the binding of particular agonists to extracellular receptors. Fluid secreted by the airway epithelium is used to maintain the depth of the periciliary liquid (PCL) above the apical membrane of the epithelial cells lining the bronchial airways. Previous mathematical models have been published which separately consider the electrophysiology involved in regulating periciliary liquid depth, and the transmission of intracellular calcium waves in airway epithelial tissue. In this paper we present a mathematical model that combines these previous models and allows the effect of oscillations in intracellular calcium on fluid secretion by airway epithelial cells to be investigated. We show that an oscillatory calcium response produces different fluid secretion properties to that elicited by a tonic rise in intracellular calcium. These differences are shown to be due to saturation of the Ca(2+) activated ion channels. Copyright 2010 Elsevier Ltd. All rights reserved.

  7. Role of time delay on intracellular calcium dynamics driven by non-Gaussian noises.

    Science.gov (United States)

    Duan, Wei-Long; Zeng, Chunhua

    2016-04-28

    Effect of time delay (τ) on intracellular calcium dynamics with non-Gaussian noises in transmission processes of intracellular Ca(2+) is studied by means of second-order stochastic Runge-Kutta type algorithm. By simulating and analyzing time series, normalized autocorrelation function, and characteristic correlation time of cytosolic and calcium store's Ca(2+) concentration, the results exhibit: (i) intracellular calcium dynamics's time coherence disappears and stability strengthens as τ → 0.1s; (ii) for the case of τ short, but they trend to a level line as τ → 0.1s, and for the case of τ > 0.1s, they show different variation as τ increases, the former changes from underdamped motion to a level line, but the latter changes from damped motion to underdamped motion; and (iii) at the moderate value of time delay, reverse resonance occurs both in cytosol and calcium store.

  8. Release of intracellular Calcium increase production of mitochondrial reactive oxygen species in renal distal epithelial cells

    DEFF Research Database (Denmark)

    Bjerregaard, Henning F.

    was inhibited by buffering of intracellular calcium with BAPTA, by the antioxidant N-acetylcysteine and by uncoupling of mitochondrial oxidative phosphorylation from respiration with CCCP. These results indicate that Cd generate a prompt initiation of ROS production from mitochondria due to an increase......Release of intracellular Calcium increase production of mitochondrial reactive oxygen species in renal distal epithelial cells. Henning F. Bjerregaard, Roskilde University, Department of Science, Systems and Models , 4000 Roskilde, Denmark. HFB@ RUC.DK Reactive oxygen species (ROS) like, hydrogen...... dynamics in living cells in response to hormonal signal events in the A6 cell culture. A6 cells have a divalent cation-sensing receptor (the extracellular calcium receptor) that can be stimulated with cadmium (Cd) and thereby induce a fast and transient liberation of calcium from intracellular stores, due...

  9. Voltage-dependent mobilization of intracellular calcium in skeletal muscle.

    Science.gov (United States)

    Schneider, M F

    1986-01-01

    In skeletal muscle calcium is released from the sarcoplasmic reticulum (SR), an internal organelle, in response to changes in the voltage across the transverse tubule (T-tubule) membrane, an external membrane system that is distinct from the SR but in close proximity to it. For T-tubule voltage changes within the physiological range, calcium release can be turned on or off on a time scale of milliseconds. The control of calcium release from the SR appears to involve at least three functional components: a voltage sensor in the T-tubule membrane, a calcium channel in the SR, and a mechanism for coupling the voltage sensor to the channel. Movement of charged or dipolar molecules within the T-tubule membrane is thought to serve as the voltage sensor. Such intramembrane charge movement (Q) can be monitored electrically and can be compared with the rate of calcium release from the SR. Calcium release is calculated from cytosolic calcium transients measured with a metallochromic indicator. Comparison of Q and the rate of release in the same isolated muscle fibre indicates that this rate is directly proportional to the amount of charge displaced in excess of a 'threshold' amount. The nature of the coupling mechanism between T-tubules and SR remains to be established but present observations impose some restrictions on possible mechanisms.

  10. Regulating Intracellular Calcium in Plants: From Molecular Genetics to Physiology

    International Nuclear Information System (INIS)

    Sze, Heven

    2008-01-01

    To grow, develop, adapt, and reproduce, plants have evolved mechanisms to regulate the uptake, translocation and sorting of calcium ions into different cells and subcellular compartments. Yet how plants accomplish this remarkable feat is still poorly understood. The spatial and temporal changes in intracellular (Ca2+) during growth and during responses to hormonal and environmental stimuli indicate that Ca2+ influx and efflux transporters are diverse and tightly regulated in plants. The specific goals were to determine the biological roles of multiple Ca pumps (ECAs) in the model plant Arabidopsis thaliana. We had pioneered the use of K616 yeast strain to functionally express plant Ca pumps, and demonstrated two distinct types of Ca pumps in plants (Sze et al., 2000. Annu Rev Plant Biol. 51,433). ACA2 represented one type that was auto-inhibited by the N-terminal region and stimulated by calmodulin. ECA1 represented another type that was not sensitive to calmodulin and phylogenetically distinct from ACAs. The goal to determine the biological roles of multiple ECA-type Ca pumps in Arabidopsis has been accomplished. Although we demonstrated ECA1 was a Ca pump by functional expression in yeast, the in vivo roles of ECAs was unclear. A few highlights are described. ECA1 and/or ECA4 are Ca/Mn pumps localized to the ER and are highly expressed in all cell types. Using homozygous T-DNA insertional mutants of eca1, we demonstrated that the ER-bound ECA1 supports growth and confers tolerance of plants growing on medium low in Ca or containing toxic levels of Mn. This is the first genetic study to determine the in vivo function of a Ca pump in plants. A phylogenetically distinct ECA3 is also a Ca/Mn pump that is localized to endosome, such as post-Golgi compartments. Although it is expressed at lower levels than ECA1, eca3 mutants are impaired in Ca-dependent root growth and in pollen tube elongation. Increased secretion of wall proteins in mutants suggests that Ca and Mn

  11. Regulating Intracellular Calcium in Plants: From Molecular Genetics to Physiology

    Energy Technology Data Exchange (ETDEWEB)

    Heven Sze

    2008-06-22

    To grow, develop, adapt, and reproduce, plants have evolved mechanisms to regulate the uptake, translocation and sorting of calcium ions into different cells and subcellular compartments. Yet how plants accomplish this remarkable feat is still poorly understood. The spatial and temporal changes in intracellular [Ca2+] during growth and during responses to hormonal and environmental stimuli indicate that Ca2+ influx and efflux transporters are diverse and tightly regulated in plants. The specific goals were to determine the biological roles of multiple Ca pumps (ECAs) in the model plant Arabidopsis thaliana. We had pioneered the use of K616 yeast strain to functionally express plant Ca pumps, and demonstrated two distinct types of Ca pumps in plants (Sze et al., 2000. Annu Rev Plant Biol. 51,433). ACA2 represented one type that was auto-inhibited by the N-terminal region and stimulated by calmodulin. ECA1 represented another type that was not sensitive to calmodulin and phylogenetically distinct from ACAs. The goal to determine the biological roles of multiple ECA-type Ca pumps in Arabidopsis has been accomplished. Although we demonstrated ECA1 was a Ca pump by functional expression in yeast, the in vivo roles of ECAs was unclear. A few highlights are described. ECA1 and/or ECA4 are Ca/Mn pumps localized to the ER and are highly expressed in all cell types. Using homozygous T-DNA insertional mutants of eca1, we demonstrated that the ER-bound ECA1 supports growth and confers tolerance of plants growing on medium low in Ca or containing toxic levels of Mn. This is the first genetic study to determine the in vivo function of a Ca pump in plants. A phylogenetically distinct ECA3 is also a Ca/Mn pump that is localized to endosome, such as post-Golgi compartments. Although it is expressed at lower levels than ECA1, eca3 mutants are impaired in Ca-dependent root growth and in pollen tube elongation. Increased secretion of wall proteins in mutants suggests that Ca and Mn

  12. Evaluation of a novel method for measurement of intracellular calcium ion concentration in fission yeast.

    Science.gov (United States)

    Ogata, Fumihiko; Satoh, Ryosuke; Kita, Ayako; Sugiura, Reiko; Kawasaki, Naohito

    2017-01-01

    The distribution of metal and metalloid species in each of the cell compartments is termed as "metallome". It is important to elucidate the molecular mechanism underlying the beneficial or toxic effects exerted by a given metal or metalloid on human health. Therefore, we developed a method to measure intracellular metal ion concentration (particularly, intracellular calcium ion) in fission yeast. We evaluated the effects of nitric acid (HNO 3 ), zymolyase, and westase treatment on cytolysis in fission yeast. Moreover, we evaluated the changes in the intracellular calcium ion concentration in fission yeast in response to treatment with/without micafungin. The fission yeast undergoes lysis when treated with 60% HNO 3 , which is simpler and cheaper compared to the other treatments. Additionally, the intracellular calcium ion concentration in 60% HNO 3 -treated fission yeast was determined by inductively coupled plasma atomic emission spectrometry. This study yields significant information pertaining to measurement of the intracellular calcium ion concentration in fission yeast, which is useful for elucidating the physiological or pathological functions of calcium ion in the biological systems. This study is the first step to obtain perspective view on the effect of the metallome in biological systems.

  13. Pulsed electromagnetic fields promote the proliferation and differentiation of osteoblasts by reinforcing intracellular calcium transients.

    Science.gov (United States)

    Tong, Jie; Sun, Lijun; Zhu, Bin; Fan, Yun; Ma, Xingfeng; Yu, Liyin; Zhang, Jianbao

    2017-10-01

    Pulsed electromagnetic fields (PEMF) can be used to treat bone-related diseases, but the underlying mechanism remains unclear, especially the process by which PEMFs initiate biological effects. In this study, we demonstrated the effects of PEMF on proliferation and differentiation of osteoblasts using the model of calcium transients induced by high extracellular calcium. Our results showed that PEMF can increase both the percentage of responding cells and amplitude of intracellular calcium transients induced by high extracellular calcium stimulation. Compared with corresponding extracellular calcium levels, PEMF stimulation increased proliferation and differentiation of osteoblasts and related gene expressions, such as insulin-like growth factor 1 (IGF-1), alkaline phosphatase (ALP), runt-related transcription factor 2 (Runx2), and osteocalcin (OCN), which can be completely abolished by BAPTA-AM. Moreover, PEMF did not affect proliferation and differentiation of osteoblasts if no intracellular calcium transient was present in osteoblasts during PEMF exposure. Our results revealed that PEMF affects osteoblast proliferation and differentiation through enhanced intracellular calcium transients, which provided a cue to treat bone-related diseases with PEMF. Bioelectromagnetics. 38:541-549, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  14. Atomic structure of intracellular amorphous calcium phosphate deposits.

    Science.gov (United States)

    Betts, F; Blumenthal, N C; Posner, A S; Becker, G L; Lehninger, A L

    1975-06-01

    The radial distribution function calculated from x-ray diffraction of mineralized cytoplasmic structures isolated from the hepatopancreas of the blue crab (Callinectes sapidus) is very similar to that previously found for synthetic amorphous calcium phosphate. Both types of mineral apparently have only short-range atomic order, represented as a neutral ion cluster of about 10 A in longest dimension, whose probable composition is expressed by the formula Ca9(PO4)6. The minor differences observed are attributed to the presence in the biological mineral of significant amounts of Mg-2+ and ATP. Synthetic amorphous calcium phosphate in contact with a solution containing an amount of ATP equivalent to that of the biological mineral failed to undergo conversion to the thermodynamically more stable hydroxyapatite. The amorphous calcium phosphate of the cytoplasmic mineral granules is similarly stable, and does not undergo conversion to hydroxyapatite, presumably owing to the presence of ATP and Mg-2+, known in inhibitors of the conversion process. The physiological implications of mineral deposits consisting of stabilized calcium phosphate ion clusters are discussed.

  15. Reduced levels of intracellular calcium releasing in spermatozoa from asthenozoospermic patients

    Science.gov (United States)

    Espino, Javier; Mediero, Matías; Lozano, Graciela M; Bejarano, Ignacio; Ortiz, Águeda; García, Juan F; Pariente, José A; Rodríguez, Ana B

    2009-01-01

    Background Asthenozoospermia is one of the most common findings present in infertile males characterized by reduced or absent sperm motility, but its aetiology remains unknown in most cases. In addition, calcium is one of the most important ions regulating sperm motility. In this study we have investigated the progesterone-evoked intracellular calcium signal in ejaculated spermatozoa from men with normospermia or asthenozoospermia. Methods Human ejaculates were obtained from healthy volunteers and asthenospermic men by masturbation after 4–5 days of abstinence. For determination of cytosolic free calcium concentration, spermatozoa were loaded with the fluorescent ratiometric calcium indicator Fura-2. Results Treatment of spermatozoa from normospermic men with 20 micromolar progesterone plus 1 micromolar thapsigargin in a calcium free medium induced a typical transient increase in cytosolic free calcium concentration due to calcium release from internal stores. Similar results were obtained when spermatozoa were stimulated with progesterone alone. Subsequent addition of calcium to the external medium evoked a sustained elevation in cytosolic free calcium concentration indicative of capacitative calcium entry. However, when progesterone plus thapsigargin were administered to spermatozoa from patients with asthenozoospermia, calcium signal and subsequent calcium entry was much smaller compared to normospermic patients. As expected, pretreatment of normospermic spermatozoa with both the anti-progesterone receptor c262 antibody and with progesterone receptor antagonist RU-38486 decreased the calcium release induced by progesterone. Treatment of spermatozoa with cytochalasin D or jasplakinolide decreased the calcium entry evoked by depletion of internal calcium stores in normospermic patients, whereas these treatments proved to be ineffective at modifying the calcium entry in patients with asthenozoospermia. Conclusion Our results suggest that spermatozoa from

  16. 3-Methylcholanthrene inhibits lymphocyte proliferation and increases intracellular calcium levels in common carp (Cyprinus carpio L)

    International Nuclear Information System (INIS)

    Reynaud, S.; Duchiron, C.; Deschaux, P.

    2003-01-01

    Polycyclic aromatic hydrocarbons (PAHs) are an important class of environmental pollutants that are known to be carcinogenic and immunotoxic. Many authors have focused on macrophage activities in fish exposed to PAHs. However, fewer studies have reported decrease in specific immunity in such fish. We investigated the intracellular mechanisms by which the 3-methylcholanthrene (3-MC) decreased lymphocyte proliferation in carp. T- and B-lymphocyte proliferation induced by Concanavalin A (Con A) and lipopolysaccharide (LPS) were inhibited by 3-MC (0.5-50 μM). 3-MC also produced a rapid and a sustained increase in intracellular calcium concentration ([Ca 2+ ] i ) (2 h minimum). However, the cytochrome P450 1A and Ah receptor inhibitor, α-naphtoflavone (a-NF), also inhibited lymphocyte proliferation and did not reverse the effects of 3-MC. Moreover, since a-NF and 3-MC increased [Ca 2+ ] i and inhibited lymphocyte proliferation it was possible that calcium release played a role in 3-MC-inhibited lymphocyte proliferation. The rise in [Ca 2+ ] i induced by 3-MC was potentiated by the inhibitor of the endoplasmic reticulum calcium ATPases, thapsigargin. Treating cells with 3-MC decreased calcium mobilization caused by thapsigargin. These results suggest that 3-MC acts on the endoplasmic reticulum, perhaps directly on calcium ATPases, to increase intracellular calcium levels in carp leucocytes

  17. Modulation of intracellular calcium levels by calcium lactate affects colon cancer cell motility through calcium-dependent calpain.

    Directory of Open Access Journals (Sweden)

    Pasupathi Sundaramoorthy

    Full Text Available Cancer cell motility is a key phenomenon regulating invasion and metastasis. Focal adhesion kinase (FAK plays a major role in cellular adhesion and metastasis of various cancers. The relationship between dietary supplementation of calcium and colon cancer has been extensively investigated. However, the effect of calcium (Ca2+ supplementation on calpain-FAK-motility is not clearly understood. We sought to identify the mechanism of FAK cleavage through Ca2+ bound lactate (CaLa, its downstream signaling and role in the motility of human colon cancer cells. We found that treating HCT116 and HT-29 cells with CaLa immediately increased the intracellular Ca2+ (iCa2+ levels for a prolonged period of time. Ca2+ influx induced cleavage of FAK into an N-terminal FAK (FERM domain in a dose-dependent manner. Phosphorylated FAK (p-FAK was also cleaved in to its p-N-terminal FAK. CaLa increased colon cancer cells motility. Calpeptin, a calpain inhibitor, reversed the effects of CaLa on FAK and pFAK cleavage in both cancer cell lines. The cleaved FAK translocates into the nucleus and modulates p53 stability through MDM2-associated ubiquitination. CaLa-induced Ca2+ influx increased the motility of colon cancer cells was mediated by calpain activity through FAK and pFAK protein destabilization. In conclusion, these results suggest that careful consideration may be given in deciding dietary Ca2+ supplementation to patient undergoing treatment for metastatic cancer.

  18. Diffusive spatio-temporal noise in a first-passage time model for intracellular calcium release

    KAUST Repository

    Flegg, Mark B.

    2013-01-01

    The intracellular release of calcium from the endoplasmic reticulum is controlled by ion channels. The resulting calcium signals exhibit a rich spatio-temporal signature, which originates at least partly from microscopic fluctuations. While stochasticity in the gating transition of ion channels has been incorporated into many models, the distribution of calcium is usually described by deterministic reaction-diffusion equations. Here we test the validity of the latter modeling approach by using two different models to calculate the frequency of localized calcium signals (calcium puffs) from clustered IP3 receptor channels. The complexity of the full calcium system is here limited to the basic opening mechanism of the ion channels and, in the mathematical reduction simplifies to the calculation of a first passage time. Two models are then studied: (i) a hybrid model, where channel gating is treated stochastically, while calcium concentration is deterministic and (ii) a fully stochastic model with noisy channel gating and Brownian calcium ion motion. The second model utilises the recently developed two-regime method [M. B. Flegg, S. J. Chapman, and R. Erban, "The two-regime method for optimizing stochastic reaction-diffusion simulations," J. R. Soc., Interface 9, 859-868 (2012)] in order to simulate a large domain with precision required only near the Ca2+ absorbing channels. The expected time for a first channel opening that results in a calcium puff event is calculated. It is found that for a large diffusion constant, predictions of the interpuff time are significantly overestimated using the model (i) with a deterministic non-spatial calcium variable. It is thus demonstrated that the presence of diffusive noise in local concentrations of intracellular Ca2+ ions can substantially influence the occurrence of calcium signals. The presented approach and results may also be relevant for other cell-physiological first-passage time problems with small ligand concentration

  19. Axotomy depletes intracellular calcium stores in primary sensory neurons.

    Science.gov (United States)

    Rigaud, Marcel; Gemes, Geza; Weyker, Paul D; Cruikshank, James M; Kawano, Takashi; Wu, Hsiang-En; Hogan, Quinn H

    2009-08-01

    The cellular mechanisms of neuropathic pain are inadequately understood. Previous investigations have revealed disrupted Ca signaling in primary sensory neurons after injury. The authors examined the effect of injury on intracellular Ca stores of the endoplasmic reticulum, which critically regulate the Ca signal and neuronal function. Intracellular Ca levels were measured with Fura-2 or mag-Fura-2 microfluorometry in axotomized fifth lumbar (L5) dorsal root ganglion neurons and adjacent L4 neurons isolated from hyperalgesic rats after L5 spinal nerve ligation, compared to neurons from control animals. Endoplasmic reticulum Ca stores released by the ryanodine-receptor agonist caffeine decreased by 46% in axotomized small neurons. This effect persisted in Ca-free bath solution, which removes the contribution of store-operated membrane Ca channels, and after blockade of the mitochondrial, sarco-endoplasmic Ca-ATPase and the plasma membrane Ca ATPase pathways. Ca released by the sarco-endoplasmic Ca-ATPase blocker thapsigargin and by the Ca-ionophore ionomycin was also diminished by 25% and 41%, respectively. In contrast to control neurons, Ca stores in axotomized neurons were not expanded by neuronal activation by K depolarization, and the proportionate rate of refilling by sarco-endoplasmic Ca-ATPase was normal. Luminal Ca concentration was also reduced by 38% in axotomized neurons in permeabilized neurons. The adjacent neurons of the L4 dorsal root ganglia showed modest and inconsistent changes after L5 spinal nerve ligation. Painful nerve injury leads to diminished releasable endoplasmic reticulum Ca stores and a reduced luminal Ca concentration. Depletion of Ca stores may contribute to the pathogenesis of neuropathic pain.

  20. Effect of calcium electroporation in combination with metformin in vivo and correlation between viability and intracellular ATP level after calcium electroporation in vitro

    DEFF Research Database (Denmark)

    Frandsen, Stine Krog; Gehl, Julie

    2017-01-01

    was limited when investigated in a 3D in vitro spheroid model. We aimed to investigate the effect of calcium electroporation in combination with metformin, a drug that affects intracellular ATP level. We also aimed to study the relationship between the viability and intracellular ATP levels after calcium...... electroporation in vitro. METHODS: In this study, we investigated the effect of calcium electroporation with metformin on NMRI-Foxn1nu mice in vivo on tumor size, survival, and intracellular ATP. We further investigated viability and intracellular ATP level in vitro after calcium electroporation in two human...... electroporation significantly reduced the size and ATP level of bladder cancer tumors treated in vivo but no increased effect of metformin combined with calcium electroporation was shown on neither tumor size, survival, nor ATP level. Calcium electroporation in vitro significantly decreased viability compared...

  1. Intracellular free calcium rise triggers nuclear envelope breakdown in the sea urchin embryo.

    Science.gov (United States)

    Steinhardt, R A; Alderton, J

    1988-03-24

    Cytosolic free calcium has recently been implicated in the regulation of mitosis in plant and animal cells. We have previously found correlations between increases in the levels of intracellular free calcium [Ca2+]i and visible transitions of structure at nuclear envelope breakdown (NEBD) and the onset of anaphase during mitosis in sea urchin embryos and tissue culture cells. To go beyond correlations it is necessary to manipulate [Ca2+]i, and in sea urchin embryos this requires the injection of calcium-chelator buffer solutions as the changes in free calcium in the cell cycle are dependent on intracellular stores. We report here that blocking the increase in [Ca2+]i which just precedes NEBD prevents this from taking place and halts mitosis. Subsequent injections which momentarily increase [Ca2+]i, or a natural recovery of the higher calcium levels, result in NEBD and the successful continuation of mitosis. Similarly, artificially increasing calcium by early injections results in early NEBD. We conclude that the increase in [Ca2+]i preceding NEBD is an essential regulatory step required for entry into mitosis.

  2. Mouse neuroblastoma cell-based model and the effect of epileptic events on calcium oscillations and neural spikes

    Science.gov (United States)

    Kim, Suhwan; Jung, Unsang; Baek, Juyoung; Lee, Sangwon; Jung, Woonggyu; Kim, Jeehyun; Kang, Shinwon

    2013-01-01

    Recently, mouse neuroblastoma cells have been considered as an attractive model for the study of human neurological and prion diseases, and they have been intensively used as a model system in different areas. For example, the differentiation of neuro2a (N2A) cells, receptor-mediated ion current, and glutamate-induced physiological responses have been actively investigated with these cells. These mouse neuroblastoma N2A cells are of interest because they grow faster than other cells of neural origin and have a number of other advantages. The calcium oscillations and neural spikes of mouse neuroblastoma N2A cells in epileptic conditions are evaluated. Based on our observations of neural spikes in these cells with our proposed imaging modality, we reported that they can be an important model in epileptic activity studies. We concluded that mouse neuroblastoma N2A cells produce epileptic spikes in vitro in the same way as those produced by neurons or astrocytes. This evidence suggests that increased levels of neurotransmitter release due to the enhancement of free calcium from 4-aminopyridine causes the mouse neuroblastoma N2A cells to produce epileptic spikes and calcium oscillations.

  3. Mouse neuroblastoma cell based model and the effect of epileptic events on calcium oscillations and neural spikes

    Science.gov (United States)

    Kim, Suhwan; Baek, Juyeong; Jung, Unsang; Lee, Sangwon; Jung, Woonggyu; Kim, Jeehyun; Kang, Shinwon

    2013-05-01

    Recently, Mouse neuroblastoma cells are considered as an attractive model for the study of human neurological and prion diseases, and intensively used as a model system in different areas. Among those areas, differentiation of neuro2a (N2A) cells, receptor mediated ion current, and glutamate induced physiological response are actively investigated. The reason for the interest to mouse neuroblastoma N2A cells is that they have a fast growing rate than other cells in neural origin with a few another advantages. This study evaluated the calcium oscillations and neural spikes recording of mouse neuroblastoma N2A cells in an epileptic condition. Based on our observation of neural spikes in mouse N2A cell with our proposed imaging modality, we report that mouse neuroblastoma N2A cells can be an important model related to epileptic activity studies. It is concluded that the mouse neuroblastoma N2A cells produce the epileptic spikes in vitro in the same way as produced by the neurons or the astrocytes. This evidence advocates the increased and strong level of neurotransmitters release by enhancement in free calcium using the 4-aminopyridine which causes the mouse neuroblastoma N2A cells to produce the epileptic spikes and calcium oscillation.

  4. Impaired mitochondria and intracellular calcium transients in the salivary glands of obese rats.

    Science.gov (United States)

    Ittichaicharoen, Jitjiroj; Apaijai, Nattayaporn; Tanajak, Pongpan; Sa-Nguanmoo, Piangkwan; Chattipakorn, Nipon; Chattipakorn, Siriporn C

    2017-04-01

    Long-term consumption of a high-fat diet (HFD) causes not only obese-insulin resistance, but is also associated with mitochondrial dysfunction in several organs. However, the effect of obese-insulin resistance on salivary glands has not been investigated. We hypothesized that obese-insulin resistance induced by HFD impaired salivary gland function by reducing salivation, increasing inflammation, and fibrosis, as well as impairing mitochondrial function and calcium transient signaling. Male Wistar rats (200-220 g) were fed either a ND or an HFD (n = 8/group) for 16 weeks. At the end of week 16, salivary flow rates, metabolic parameters, and plasma oxidative stress were determined. Rats were then sacrificed and submandibular glands were removed to determine inflammation, fibrosis, apoptosis, mitochondrial function and dynamics, and intracellular calcium transient signaling. Long-term consumption of an HFD caused obese-insulin resistance and increased oxidative stress, fibrosis, inflammation, and apoptosis in the salivary glands. In addition, impaired mitochondrial function, as indicated by increased mitochondrial reactive oxygen species, mitochondrial membrane depolarization, and mitochondrial swelling in salivary glands and impaired intracellular calcium regulation, as indicated by a reduced intracellular calcium transient rising rate, decay rates, and amplitude of salivary acinar cells, were observed in HFD-fed rats. However, salivary flow rate and level of aquaporin 5 protein were not different between both groups. Although HFD consumption did not affect salivation, it caused obese-insulin resistance, leading to pathophysiological alteration of salivary glands, including impaired intracellular calcium transients, increased oxidative stress and inflammation, and salivary mitochondrial dysfunction.

  5. Intracellular calcium stores in beta-escin skinned rat and guinea-pig bladders.

    Science.gov (United States)

    Tugba Durlu-Kandilci, N; Brading, Alison F

    2007-07-02

    Intracellular Ca2+ stores in rat and guinea-pig bladders and taenia caecum were studied in beta-escin skinned smooth muscle strips. 30 min of skinning with 40 microM and 80 microM beta-escin were the best parameters found to obtain good calcium response curves (10(-7)-10(-4) M) in rat and guinea pig, respectively. Calmodulin (1 microM) increased the calcium contractions significantly. pCa 6 was used to load intracellular stores and application of carbachol (50 microM) in all tissues then only contracted the tissues in the presence of guanosine-5'-triphosphate (GTP; 100 microM). Inositol triphosphate (IP3; 50 microM), applied after pCa 6, contracted all tissues. Carbachol added after IP3 or heparin (1 mg/ml) no longer caused a contraction in any of them. In bladders, caffeine (30 mM) but not ryanodine (5 microM) prevented the subsequent carbachol contraction. A slowly rising contraction with carbachol was elicited after caffeine (30 mM) or ryanodine (5 microM) in the taenia and after ryanodine in the bladders. Caffeine (30 mM) suppressed the calcium response curves in all tissues. Procaine (30 mM) blocked the carbachol (50 microM) contractions in bladders but not in taenia. These results suggest that calcium induced calcium release (CICR) and IP3 induced calcium release (IICR) release calcium from a common store in bladder but two different compartments in taenia.

  6. Effects of arachnotoxin on intracellular pH and calcium in human spermatozoa.

    Science.gov (United States)

    Romero, Fernando; Cunha, Maria Adelaide; Sanchez, Raul; Ferreira, Alice Teixeira; Schor, Nestor; Oshiro, Maria Etsuko Miyamoto

    2007-06-01

    To determine the effect of arachnotoxin (ATx), a venom extracted from the Chilean spider Latrodectus mactans, on intracellular calcium ([Ca(2+)](i)) and pH (pH(i)) in capacitated human spermatozoa. Spermatozoa were collected from fertile adult men (n = 8). Mobile spermatozoa were collected by the "swim up" technique and stimulated with the crude extract of ATx and with progesterone (P). Hospital of the Federal University of São Paulo, São Paulo, Brazil. [Ca(2+)](i) was measured in fura2-AM-loaded spermatozoa, and pH(i) was measured in spermatozoa loaded with the pH-sensitive dye [(2',7')-bis (carboxymethyl)-(5,6)-carboxyfluorescein]-AM (BCECF). The ATx and P induced a biphasic change in [Ca(2+)](i) consisting of a peak followed by a small but sustained elevation. The response to ATx was greatly reduced by pretreatment with P. The ATx caused intracellular acidification, whereas P induced alkalinization. Blockade of the NA(+)/H(+) exchanger with ethylisopropylamiloride (EIPA) sharply increased ATx-induced acidification. Arachnotoxin increased [Ca(2+)](i) through the opening of calcium channels and release of calcium from intracellular stores. The ATx reduced pH(i) in human sperm, possibly by inhibiting the Na(+)/H(+) exchanger.

  7. Ultrafine particles cause cytoskeletal dysfunctions in macrophages: role of intracellular calcium

    Directory of Open Access Journals (Sweden)

    Brown David M

    2005-10-01

    Full Text Available Abstract Background Particulate air pollution is reported to cause adverse health effects in susceptible individuals. Since most of these particles are derived form combustion processes, the primary composition product is carbon with a very small diameter (ultrafine, less than 100 nm in diameter. Besides the induction of reactive oxygen species and inflammation, ultrafine particles (UFP can cause intracellular calcium transients and suppression of defense mechanisms of alveolar macrophages, such as impaired migration or phagocytosis. Methods In this study the role of intracellular calcium transients caused by UFP was studied on cytoskeleton related functions in J774A.1 macrophages. Different types of fine and ultrafine carbon black particles (CB and ufCB, respectively, such as elemental carbon (EC90, commercial carbon (Printex 90, diesel particulate matter (DEP and urban dust (UD, were investigated. Phagosome transport mechanisms and mechanical cytoskeletal integrity were studied by cytomagnetometry and cell viability was studied by fluorescence microscopy. Macrophages were exposed in vitro with 100 and 320 μg UFP/ml/million cells for 4 hours in serum free medium. Calcium antagonists Verapamil, BAPTA-AM and W-7 were used to block calcium channels in the membrane, to chelate intracellular calcium or to inhibit the calmodulin signaling pathways, respectively. Results Impaired phagosome transport and increased cytoskeletal stiffness occurred at EC90 and P90 concentrations of 100 μg/ml/million cells and above, but not with DEP or UD. Verapamil and W-7, but not BAPTA-AM inhibited the cytoskeletal dysfunctions caused by EC90 or P90. Additionally the presence of 5% serum or 1% bovine serum albumin (BSA suppressed the cytoskeletal dysfunctions. Cell viability showed similar results, where co-culture of ufCB together with Verapamil, W-7, FCS or BSA produced less cell dead compared to the particles only.

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

    Directory of Open Access Journals (Sweden)

    HERMANSYAH

    2010-03-01

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

  9. Antagonists of the TMEM16A calcium-activated chloride channel modulate airway smooth muscle tone and intracellular calcium.

    Science.gov (United States)

    Danielsson, Jennifer; Perez-Zoghbi, Jose; Bernstein, Kyra; Barajas, Matthew B; Zhang, Yi; Kumar, Satish; Sharma, Pawan K; Gallos, George; Emala, Charles W

    2015-09-01

    Perioperative bronchospasm refractory to β agonists continues to challenge anesthesiologists and intensivists. The TMEM16A calcium-activated chloride channel modulates airway smooth muscle (ASM) contraction. The authors hypothesized that TMEM16A antagonists would relax ASM contraction by modulating membrane potential and calcium flux. Human ASM, guinea pig tracheal rings, or mouse peripheral airways were contracted with acetylcholine or leukotriene D4 and then treated with the TMEM16A antagonists: benzbromarone, T16Ainh-A01, N-((4-methoxy)-2-naphthyl)-5-nitroanthranilic acid, or B25. In separate studies, guinea pig tracheal rings were contracted with acetylcholine and then exposed to increasing concentrations of isoproterenol (0.01 nM to 10 μM) ± benzbromarone. Plasma membrane potential and intracellular calcium concentrations were measured in human ASM cells. Benzbromarone was the most potent TMEM16A antagonist tested for relaxing an acetylcholine -induced contraction in guinea pig tracheal rings (n = 6). Further studies were carried out to investigate the clinical utility of benzbromarone. In human ASM, benzbromarone relaxed either an acetylcholine- or a leukotriene D4-induced contraction (n = 8). Benzbromarone was also effective in relaxing peripheral airways (n = 9) and potentiating relaxation by β agonists (n = 5 to 10). In cellular mechanistic studies, benzbromarone hyperpolarized human ASM cells (n = 9 to 12) and attenuated intracellular calcium flux from both the plasma membrane and the sarcoplasmic reticulum (n = 6 to 12). TMEM16A antagonists work synergistically with β agonists and through a novel pathway of interrupting ion flux at both the plasma membrane and sarcoplasmic reticulum to acutely relax human ASM.

  10. [Effects of grape procyanidins on the concentration of intracellular calcium and the proliferation activity of the hepatoma cells].

    Science.gov (United States)

    Zhong, Jin-Yi; Li, Jie; Liu, Hui; Zhang, She-Hua

    2006-09-01

    To investigate the effects of grape procyanidins (GPC) on concentration of intracellular calcium and the proliferation activity of normal hepatic cells and the hepatic cell injuried by alcohol. Rat hepatic cells and the cell injuried by alcohol were cultured with different concentration of GPC. The proliferation activity and concentration of intracellular calcium of the hepatic cells were measured by MTT assay and Fura-2 fluorescence methods. (1) The concentration of intracellular calcium of the normal control group and alcohol injury group were (108.26 +/- 14.17) and (651.24 +/- 47.95) nmol/L respectively, and that of both the high and the medium dose GPC groups were lower than the alcohol injury group, all differences are significant (P calcium in the normal hepatic cells treated with GPC is the group with calcium of extracellular fluid > the group free from calcium of extracellular fluid > the normal control group. (3) The proliferation activity of the high and the medium dose GPC group of normal hepatic cell and the cell injuried by alcohol were higher than the normal control group and alcohol injury group, all differences are significant (P calcium concentration of normal hepatic cell by increasing extracellular fluidca introaffluxion and release from calcium pool, and enhance the proliferation activity of hepatic cells. It also can inhibit the abnormal rise (overload) of intracellular calcium concentration and the proliferation activity injury of hepatic cell induced by alcohol.

  11. Differences between negative inotropic and vasodilator effects of calcium antagonists acting on extra- and intracellular calcium movements in rat and guinea-pig cardiac preparations

    NARCIS (Netherlands)

    Hugtenburg, J. G.; Mathy, M. J.; Boddeke, H. W.; Beckeringh, J. J.; van Zwieten, P. A.

    1989-01-01

    In order to get more insight into the utilization of calcium in the mammalian heart and the influence of calcium antagonists on this process we have evaluated the negative inotropic and vasodilator effect of nifedipine, diltiazem, verapamil, bepridil and lidoflazine as well as of the intracellularly

  12. Calcium influx affects intracellular transport and membrane repair following nanosecond pulsed electric field exposure.

    Science.gov (United States)

    Thompson, Gary Lee; Roth, Caleb C; Dalzell, Danielle R; Kuipers, Marjorie; Ibey, Bennett L

    2014-05-01

    The cellular response to subtle membrane damage following exposure to nanosecond pulsed electric fields (nsPEF) is not well understood. Recent work has shown that when cells are exposed to nsPEF, ion permeable nanopores (2  nm) created by longer micro- and millisecond duration pulses. Nanoporation of the plasma membrane by nsPEF has been shown to cause a transient increase in intracellular calcium concentration within milliseconds after exposure. Our research objective is to determine the impact of nsPEF on calcium-dependent structural and repair systems in mammalian cells. Chinese hamster ovary (CHO-K1) cells were exposed in the presence and absence of calcium ions in the outside buffer to either 1 or 20, 600-ns duration electrical pulses at 16.2  kV/cm, and pore size was determined using propidium iodide and calcium green. Membrane organization was observed with morphological changes and increases in FM1-43 fluorescence. Migration of lysosomes, implicated in membrane repair, was followed using confocal microscopy of red fluorescent protein-tagged LAMP1. Microtubule structure was imaged using mEmerald-tubulin. We found that at high 600-ns PEF dosage, calcium-induced membrane restructuring and microtubule depolymerization coincide with interruption of membrane repair via lysosomal exocytosis.

  13. Calcium influx affects intracellular transport and membrane repair following nanosecond pulsed electric field exposure

    Science.gov (United States)

    Thompson, Gary Lee; Roth, Caleb C.; Dalzell, Danielle R.; Kuipers, Marjorie; Ibey, Bennett L.

    2014-05-01

    The cellular response to subtle membrane damage following exposure to nanosecond pulsed electric fields (nsPEF) is not well understood. Recent work has shown that when cells are exposed to nsPEF, ion permeable nanopores (2 nm) created by longer micro- and millisecond duration pulses. Nanoporation of the plasma membrane by nsPEF has been shown to cause a transient increase in intracellular calcium concentration within milliseconds after exposure. Our research objective is to determine the impact of nsPEF on calcium-dependent structural and repair systems in mammalian cells. Chinese hamster ovary (CHO-K1) cells were exposed in the presence and absence of calcium ions in the outside buffer to either 1 or 20, 600-ns duration electrical pulses at 16.2 kV/cm, and pore size was determined using propidium iodide and calcium green. Membrane organization was observed with morphological changes and increases in FM1-43 fluorescence. Migration of lysosomes, implicated in membrane repair, was followed using confocal microscopy of red fluorescent protein-tagged LAMP1. Microtubule structure was imaged using mEmerald-tubulin. We found that at high 600-ns PEF dosage, calcium-induced membrane restructuring and microtubule depolymerization coincide with interruption of membrane repair via lysosomal exocytosis.

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

    Directory of Open Access Journals (Sweden)

    Milos B. Rokic

    2018-04-01

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

  15. The decompensated detrusor I: the effects of bladder outlet obstruction on the use of intracellular calcium stores.

    Science.gov (United States)

    Rohrmann, D; Levin, R M; Duckett, J W; Zderic, S A

    1996-08-01

    As in other smooth muscle groups, extracellular calcium influx as well as the release of calcium from intracellular storage sites or sarcoplasmic reticulum occur in response to receptor stimulation. The relative participation of extracellular influx versus intracellular release has recently been shown to be influenced by developmental stage and obstruction. Partial bladder outlet obstruction results in marked hypertrophy of the bladder and produces alterations in contractile function. To understand better how this contractile dysfunction after outlet obstruction is influenced by intracellular calcium handling we tested the effects of 2 drugs with known effects on the sarcoplasmic reticulum. We evaluated ryanodine, which blocks the release of calcium from the sarcoplasmic reticulum, and thapsigargin, which blocks the ability of the sarcoplasmic reticulum to pump cytosolic calcium back into the storage sites. Rabbit bladders were obstructed for different periods, after which detrusor muscle strips were harvested and contractile performance was evaluated in the absence and presence of ryanodine and thapsigargin. In the early phases of outlet obstruction the release of intracellular calcium increased significantly. With prolonged obstruction and detrusor decompensation the intracellular storage sites lost the ability to contribute to the generation of contractile force. Alterations in the calcium handling ability of the smooth muscle cell appear to have an important role in the process of decompensation of bladder function in infravesical obstruction.

  16. Raised Intracellular Calcium Contributes to Ischemia-Induced Depression of Evoked Synaptic Transmission.

    Directory of Open Access Journals (Sweden)

    Shirin Jalini

    Full Text Available Oxygen-glucose deprivation (OGD leads to depression of evoked synaptic transmission, for which the mechanisms remain unclear. We hypothesized that increased presynaptic [Ca2+]i during transient OGD contributes to the depression of evoked field excitatory postsynaptic potentials (fEPSPs. Additionally, we hypothesized that increased buffering of intracellular calcium would shorten electrophysiological recovery after transient ischemia. Mouse hippocampal slices were exposed to 2 to 8 min of OGD. fEPSPs evoked by Schaffer collateral stimulation were recorded in the stratum radiatum, and whole cell current or voltage clamp recordings were performed in CA1 neurons. Transient ischemia led to increased presynaptic [Ca2+]i, (shown by calcium imaging, increased spontaneous miniature EPSP/Cs, and depressed evoked fEPSPs, partially mediated by adenosine. Buffering of intracellular Ca2+ during OGD by membrane-permeant chelators (BAPTA-AM or EGTA-AM partially prevented fEPSP depression and promoted faster electrophysiological recovery when the OGD challenge was stopped. The blocker of BK channels, charybdotoxin (ChTX, also prevented fEPSP depression, but did not accelerate post-ischemic recovery. These results suggest that OGD leads to elevated presynaptic [Ca2+]i, which reduces evoked transmitter release; this effect can be reversed by increased intracellular Ca2+ buffering which also speeds recovery.

  17. Raised Intracellular Calcium Contributes to Ischemia-Induced Depression of Evoked Synaptic Transmission.

    Science.gov (United States)

    Jalini, Shirin; Ye, Hui; Tonkikh, Alexander A; Charlton, Milton P; Carlen, Peter L

    2016-01-01

    Oxygen-glucose deprivation (OGD) leads to depression of evoked synaptic transmission, for which the mechanisms remain unclear. We hypothesized that increased presynaptic [Ca2+]i during transient OGD contributes to the depression of evoked field excitatory postsynaptic potentials (fEPSPs). Additionally, we hypothesized that increased buffering of intracellular calcium would shorten electrophysiological recovery after transient ischemia. Mouse hippocampal slices were exposed to 2 to 8 min of OGD. fEPSPs evoked by Schaffer collateral stimulation were recorded in the stratum radiatum, and whole cell current or voltage clamp recordings were performed in CA1 neurons. Transient ischemia led to increased presynaptic [Ca2+]i, (shown by calcium imaging), increased spontaneous miniature EPSP/Cs, and depressed evoked fEPSPs, partially mediated by adenosine. Buffering of intracellular Ca2+ during OGD by membrane-permeant chelators (BAPTA-AM or EGTA-AM) partially prevented fEPSP depression and promoted faster electrophysiological recovery when the OGD challenge was stopped. The blocker of BK channels, charybdotoxin (ChTX), also prevented fEPSP depression, but did not accelerate post-ischemic recovery. These results suggest that OGD leads to elevated presynaptic [Ca2+]i, which reduces evoked transmitter release; this effect can be reversed by increased intracellular Ca2+ buffering which also speeds recovery.

  18. Abortive and propagating intracellular calcium waves: analysis from a hybrid model.

    Directory of Open Access Journals (Sweden)

    Nara Guisoni

    Full Text Available The functional properties of inositol(1,4,5-triphosphate (IP3 receptors allow a variety of intracellular Ca(2+ phenomena. In this way, global phenomena, such as propagating and abortive Ca(2+ waves, as well as local events such as puffs, have been observed. Several experimental studies suggest that many features of global phenomena (e.g., frequency, amplitude, speed wave depend on the interplay of biophysical processes such as diffusion, buffering, efflux and influx rates, which in turn depend on parameters such as buffer concentration, Ca(2+ pump density, cytosolic IP3 level, and intercluster distance. Besides, it is known that cells are able to modify some of these parameters in order to regulate the Ca(2+ signaling. By using a hybrid model, we analyzed different features of the hierarchy of calcium events as a function of two relevant parameters for the calcium signaling, the intercluster distance and the pump strength or intensity. In the space spanned by these two parameters, we found two modes of calcium dynamics, one dominated by abortive calcium waves and the other by propagating waves. Smaller distances between the release sites promote propagating calcium waves, while the increase of the efflux rate makes the transition from propagating to abortive waves occur at lower values of intercluster distance. We determined the frontier between these two modes, in the parameter space defined by the intercluster distance and the pump strength. Furthermore, we found that the velocity of simulated calcium waves accomplishes Luther's law, and that an effective rate constant for autocatalytic calcium production decays linearly with both the intercluster distance and the pump strength.

  19. Regulation of granule cell excitability by a low-threshold calcium spike in turtle olfactory bulb

    DEFF Research Database (Denmark)

    Pinato, Giulietta; Midtgaard, Jens

    2003-01-01

    Granule cells excitability in the turtle olfactory bulb was analyzed using whole cell recordings in current- and voltage-clamp mode. Low-threshold spikes (LTSs) were evoked at potentials that are subthreshold for Na spikes in normal medium. The LTSs were evoked from rest, but hyperpolarization...

  20. BDNF-Induced Potentiation of Spontaneous Twitching in Innervated Myocytes Requires Calcium Release From Intracellular Stores

    Science.gov (United States)

    KLEIMAN, ROBIN J.; TIAN, NING; KRIZAJ, DAVID; HWANG, THOMAS N.; COPENHAGEN, DAVID R.; REICHARDT, LOUIS F.

    2009-01-01

    Brain-derived neurotrophic factor (BDNF) can potentiate synaptic release at newly developed frog neuromuscular junctions. Although this potentiation depends on extracellular Ca2+ and reflects changes in acetylcholine release, little is known about the intracellular transduction or calcium signaling pathways. We have developed a video assay for neurotrophin-induced potentiation of myocyte twitching as a measure of potentiation of synaptic activity. We use this assay to show that BDNF-induced synaptic potentiation is not blocked by cadmium, indicating that Ca2+ influx through voltage-gated Ca2+ channels is not required. TrkB autophosphorylation is not blocked in Ca2+-free conditions, indicating that TrkB activity is not Ca2+ dependent. Additionally, an inhibitor of phospholipase C interferes with BDNF-induced potentiation. These results suggest that activation of the TrkB receptor activates phospholipase C to initiate intracellular Ca2+ release from stores which subsequently potentiates transmitter release. PMID:10899220

  1. Cytosolic calcium homeostasis in fungi: Roles of plasma membrane transport and intracellular sequestration of calcium

    International Nuclear Information System (INIS)

    Miller, A.J.; Vogg, G.; Sanders, D.

    1990-01-01

    Cytosolic free calcium ([Ca 2+ ] c ) has been measured in the mycelial fungus Neurospora crassa with Ca 2+ - selective microelectrodes. The mean value of [Ca 2+ ] c is 92 ± 15 nM and it is insensitive to external pH values between 5.8 and 8.4. Simultaneous measurement of membrane potential enables the electrochemical potential difference for Ca 2+ across the plasma membrane to be estimated as about -60 kJmol -1 - a value that cannot be sustained either by a simple Ca 2+ - ATPase, or, in alkaline conditions, by straightforward H + /Ca 2+ exchange with a stoichiometric ratio of + /Ca 2+ . The authors propose that the most likely alternative mechanism of Ca 2+ efflux is ATP-driven H + /Ca 2+ exchange, with a stoichiometric ratio of at least 2 H + /Ca 2+ . The increase in [Ca 2+ ] c in the presence of CN - at pH 8.4 is compared with 45 Ca 2+ influx under the same conditions. The proportion of entering Ca 2+ remaining free in the cytosol is only 8 x 10 -5 , and since the concentration of available chelation sites on Ca 2+ binding proteins is unlikely to exceed 100 μM, a major role for the fungal vacuole in short-term Ca 2+ homeostasis is indicated. This notion is supported by the observation that cytosolic Ca 2+ homeostasis is disrupted by a protonophore, which rapidly abolishes the driving force for Ca 2+ uptake into fungal vacuoles

  2. Agouti regulation of intracellular calcium: Role in the insulin resistance of viable yellow mice

    Energy Technology Data Exchange (ETDEWEB)

    Zemel, M.B.; Kim, J.H. [Univ. of Tennessee, Knoxville, TN (United States); Woychik, R.P.; Michaud, E.J. [Oak Ridge National Laboratory, Oak Ridge, TN (United States); Hadwell, S.H.; Patel, I.R.; Wilkison, W.O. [Research Institute, Research Triangle Park, NC (United States)

    1995-05-23

    Several dominant mutations at the agouti locus in the mouse cause a syndrome of marked obesity, hyperinsulinemia, and insulin resistance. Although it is known that the agouti gene is expressed in an ectopic manner in these mutants, the precise mechanism by which the agouti gene product mediates these effects is unclear. Since intracellular Ca{sup 2+} is believed to play a role in mediating insulin action and dysregulation of Ca{sup 2+} flux is observed in diabetic animals and humans, we examined the status of intracellular Ca{sup 2+} in mice carrying the dominant agouti allele, viable yellow (A{sup vy}). We show here that in mice carrying this mutation, the intracellular free calcium concentration ([Ca{sup 2+}]{sub i}) is elevated in skeletal muscle, and the degree of elevation is closely correlated with the degree to which the mutant traits are expressed in individual animals. Moreover, we demonstrate that the agouti gene product is capable of inducing increased [Ca{sup 2+}]{sub i} in cultured and freshly isolated skeletal muscle myocytes from wild-type mice. Based on these findings, we present a model in which we propose that the agouti polypeptide promotes insulin resistance in mutant animals through its ability to increase [Ca{sup 2+}]{sub i}. 36 refs., 3 figs., 2 tabs.

  3. Intracellular Calcium Decreases Upon Hyper Gravity-Treatment of Arabidopsis Thaliana Cell Cultures

    Science.gov (United States)

    Neef, Maren; Denn, Tamara; Ecke, Margret; Hampp, Rüdiger

    2016-06-01

    Cell cultures of Arabidopsis thaliana ( A. t.) respond to changes in the gravitational field strength with fluctuations of the amount of cytosolic calcium (Ca2+). In parabolic flight experiments, where hyper- and μg phases follow each other, μg clearly increased Ca2+, while hyper-g caused a slight reduction. Since the latter observation had not been reported before, we studied this effect in more detail. Using a special centrifuge for heavy items (ZARM, Bremen, Germany), we determined the hyper-g-dependent intracellular Ca2+ level with transgenic cell lines expressing the Ca2+ sensor, cameleon. This sensor exhibits a shift in fluorescence from 480 to 530 nm in response to Ca2+ binding. The data show a drop in the intracellular Ca2+ concentration with a threshold gravity of around 3 g. This is above hypergravity levels achieved during parabolic flights (1.8 g). The use of mutants with different sub-cellular targets of cameleon expression (nucleus, tonoplast, plasma membrane) gave the same results, i.e. Ca2+ is obviously exported from several intracellular compartments.

  4. Cannabinoid Receptor Activation Modifies NMDA Receptor Mediated Release of Intracellular Calcium: Implications for Endocannabinoid Control of Hippocampal Neural Plasticity

    Science.gov (United States)

    Hampson, Robert E.; Miller, Frances; Palchik, Guillermo; Deadwyler, Sam A.

    2011-01-01

    Chronic activation or inhibition of cannabinoid receptors (CB1) leads to continuous suppression of neuronal plasticity in hippocampus and other brain regions, suggesting that endocannabinoids may have a functional role in synaptic processes that produce state-dependent transient modulation of hippocampal cell activity. In support of this, it has previously been shown in vitro that cannabinoid CB1 receptors modulate second messenger systems in hippocampal neurons that can modulate intracellular ion channels, including channels which release calcium from intracellular stores. Here we demonstrate in hippocampal slices a similar endocannabinoid action on excitatory glutamatergic synapses via modulation of NMDA-receptor mediated intracellular calcium levels in confocal imaged neurons. Calcium entry through glutamatergic NMDA-mediated ion channels increases intracellular calcium concentrations via modulation of release from ryanodine-sensitive channels in endoplasmic reticulum. The studies reported here show that NMDA-elicited increases in Calcium Green fluorescence are enhanced by CB1 receptor antagonists (i.e. rimonabant), and inhibited by CB1 agonists (i.e. WIN 55,212-2). Suppression of endocannabinoid breakdown by either reuptake inhibition (AM404) or fatty-acid amide hydrolase inhibition (URB597) produced suppression of NMDA elicited calcium increases comparable to WIN 55,212-2, while enhancement of calcium release provoked by endocannabinoid receptor antagonists (Rimonabant) was shown to depend on the blockade of CB1 receptor mediated de-phosphorylation of Ryanodine receptors. Such CB1 receptor modulation of NMDA elicited increases in intracellular calcium may account for the respective disruption and enhancement by CB1 agents of trial-specific hippocampal neuron ensemble firing patterns during performance of a short-term memory task, reported previously from this laboratory. PMID:21288475

  5. Regulation of neural cell adhesion molecule polysialylation: evidence for nontranscriptional control and sensitivity to an intracellular pool of calcium.

    Science.gov (United States)

    Brusés, J L; Rutishauser, U

    1998-03-09

    The up- and downregulation of polysialic acid-neural cell adhesion molecule (PSA-NCAM) expression on motorneurons during development is associated respectively with target innervation and synaptogenesis, and is regulated at the level of PSA enzymatic biosynthesis involving specific polysialyltransferase activity. The purpose of this study has been to describe the cellular mechanisms by which that regulation might occur. It has been found that developmental regulation of PSA synthesis by ciliary ganglion motorneurons is not reflected in the levels of polysialyltransferase-1 (PST) or sialyltransferase-X (STX) mRNA. On the other hand, PSA synthesis in both the ciliary ganglion and the developing tectum appears to be coupled to the concentration of calcium in intracellular compartments. This study documents a calcium dependence of polysialyltransferase activity in a cell-free assay over the range of 0.1-1 mM, and a rapid sensitivity of new PSA synthesis, as measured in a pulse-chase analysis of tissue explants, to calcium ionophore perturbation of intracellular calcium levels. Moreover, the relevant calcium pool appears to be within a specific intracellular compartment that is sensitive to thapsigargin and does not directly reflect the level of cytosolic calcium. Perturbation of other major second messenger systems, such as cAMP and protein kinase-dependent pathways, did not affect polysialylation in the pulse chase analysis. These results suggest that the shuttling of calcium to different pools within the cell can result in the rapid regulation of PSA synthesis in developing tissues.

  6. PeakCaller: an automated graphical interface for the quantification of intracellular calcium obtained by high-content screening.

    Science.gov (United States)

    Artimovich, Elena; Jackson, Russell K; Kilander, Michaela B C; Lin, Yu-Chih; Nestor, Michael W

    2017-10-16

    Intracellular calcium is an important ion involved in the regulation and modulation of many neuronal functions. From regulating cell cycle and proliferation to initiating signaling cascades and regulating presynaptic neurotransmitter release, the concentration and timing of calcium activity governs the function and fate of neurons. Changes in calcium transients can be used in high-throughput screening applications as a basic measure of neuronal maturity, especially in developing or immature neuronal cultures derived from stem cells. Using human induced pluripotent stem cell derived neurons and dissociated mouse cortical neurons combined with the calcium indicator Fluo-4, we demonstrate that PeakCaller reduces type I and type II error in automated peak calling when compared to the oft-used PeakFinder algorithm under both basal and pharmacologically induced conditions. Here we describe PeakCaller, a novel MATLAB script and graphical user interface for the quantification of intracellular calcium transients in neuronal cultures. PeakCaller allows the user to set peak parameters and smoothing algorithms to best fit their data set. This new analysis script will allow for automation of calcium measurements and is a powerful software tool for researchers interested in high-throughput measurements of intracellular calcium.

  7. Intracellular calcium movements of boar spermatozoa during 'in vitro' capacitation and subsequent acrosome exocytosis follow a multiple-storage place, extracellular calcium-dependent model.

    Science.gov (United States)

    Yeste, M; Fernández-Novell, J M; Ramió-Lluch, L; Estrada, E; Rocha, L G; Cebrián-Pérez, J A; Muiño-Blanco, T; Concha, I I; Ramírez, A; Rodríguez-Gil, J E

    2015-07-01

    This work analysed intracellular calcium stores of boar spermatozoa subjected to 'in vitro' capacitation (IVC) and subsequent progesterone-induced acrosome exocytosis (IVAE). Intracellular calcium was analysed through two calcium markers with different physico-chemical properties, Fluo-3 and Rhod-5N. Indicative parameters of IVC and IVAE were also evaluated. Fluo-3 was located at both the midpiece and the whole head. Rhod-5N was present at the sperm head. This distribution did not change in any of the assayed conditions. Induction of IVC was concomitant with an increase in both head and midpiece Ca(2+) signals. Additionally, while IVC induction was concurrent with a significant (p spermatozoa in the absence of calcium showed a loss of both Ca(2+) labellings concomitantly with the sperm's inability to achieve IVC. The absence of extracellular calcium also induced a severe decrease in the percentage of spermatozoa exhibiting high mitochondrial membrane potential (hMMP). The IVAE was accompanied by a fast increase in both Ca(2+) signalling in control spermatozoa. These peaks were either not detected or much lessened in the absence of calcium. Remarkably, Fluo-3 marking at the midpiece increased after progesterone addition to sperm cells incubated in a medium without Ca(2+) . The simultaneous addition of progesterone with the calcium chelant EGTA inhibited IVAE, and this was accompanied by a significant (p spermatozoa present different calcium deposits with a dynamic equilibrium among them and with the extracellular environment. Additionally, the modulation role of the intracellular calcium in spermatozoa function seems to rely on its precise localization in boar spermatozoa. © 2015 American Society of Andrology and European Academy of Andrology.

  8. Release of intracellular Calcium increase production of mitochondrial reactive oxygen species in renal distal epithelial cells

    DEFF Research Database (Denmark)

    Bjerregaard, Henning F.

    to G-protein stimulation of phospholipase C and release of inositol -3 phosphate. Cd (0.4 mM) treatment of A6 cells enhanced the ROS production after one minutes incubation. The production rate was constant for at least 10 to 20 min. Experiments showed that the Cd induced increase in ROS production......Release of intracellular Calcium increase production of mitochondrial reactive oxygen species in renal distal epithelial cells. Henning F. Bjerregaard, Roskilde University, Department of Science, Systems and Models , 4000 Roskilde, Denmark. HFB@ RUC.DK Reactive oxygen species (ROS) like, hydrogen...... peroxide (H2O2) has traditionally been regarded as toxic by-products of aerobic metabolism. However, recent findings indicate that H2O2 act as a signalling molecule. The aim of the present study was to monitor, in real time, the rates of ROS generation in order to directly determine their production...

  9. [Progress of Researches on Protective Effect of Acupuncture and Moxibustion in Relieving Intracellular Calcium Overload of Cradiomyocytes].

    Science.gov (United States)

    Xiao, Yan; Gu, Yi-Huang; Chen, Hao

    2016-06-25

    Myocardial contraction and relaxation are regulated by increases and decreases of the intracellular cytoplasmic calcium (Ca 2+ ) concentration. Intracellular calcium ion is also a ubiquitous second messenger, and its related signal transduction pathways involve a variety of physiological activities and pathological changes. It has been well documented that intracellular calcium overload is involved in myocardial cellular injury. In the present paper, the authors make a review about experimental researches on the underlying mechanisms of acupuncture and moxibustion in the prevention and treatment of ischemic myocardial injury from reducing calcium overload in recent 10 years. Results of recent studies indicate that acupuncture and moxibustion interventions have a cardioprotective effect by raising Ca 2+ -ATPase activity and nitric oxide content, lowering L-type voltage depen-dent calcium channel activity, and ameliorating calcium overload in ischemic cardiomyocytes mainly through cytomembrane, sarcoplasmic reticulum membrane and mitochondrial membrane pathways. However, the current studies on the mechanisms of acupuncture in the improvement of the ischemic myocardial injury are far unclear up to now and do not closely combine the clinical application.

  10. Inclusões intracelulares associadas à "espiga branca" do trigo Intracellular inclusions associated with white spike disease of wheat

    Directory of Open Access Journals (Sweden)

    E. W. Kitajima

    1971-05-01

    Full Text Available Fragmentos da epiderme inferior de fôlhas de trigo com sintomas típicos da anomalia conhecida como "espiga branca", examinados ao microscópio convencional, mostraram a constante ocorrência de inclusões intracelulares, de dimensões avantajadas e de aspecto fibrilar e enovelado. Freqüentemente, células adjacentes aquelas que continham inclusões apresentavam formações aciculares, em seu interior. Seções ultrafinas dessas folhas, examinadas ao microscópio electrô-nico, revelaram que tais inclusões eram de localização citoplasmática e formadas por uma massa de partículas filamentosas de 7-10 m¼ em diâmetro e de comprimento indeterminado, idênticas àquelas encontradas em preparações "leaf dip". Várias alterações celulares, como hipertrofia do nucléolo, degeneração dos cloroplastos e vesicularização do retículo endoplasmático, puderam também ser notadas. Ocasionalmente, formações cristalinas foram notadas na periferia e mesmo no interior do núcleo. A semelhança das inclusões citoplasmáticas e das partículas que as compõem, com aquelas descritas, associadas à infecção do vírus da "hoja blanca" do arroz, e também o fato de o trigo desenvolver sintomas do tipo espiga branca quando inoculado experimentalmente com o vírus da "hoja blanca", parecem reforçar a sugestão de que a espiga branca do trigo teria etiologia virosa e que o agente causal seria do grupo do vírus da "hoja blanca" do arroz. A constante associação das inclusões celulares com a condição de espiga branca, em trigo, constitui mais um elemento para sua rápida diagnose.Light microscopic examination of epidermal strips from leaves of wheat (Triticum sativumL. showing typical symptoms of the white spike (WS disease, demonstrated the constant occurrence of huge, fibrous and whorled intracellular inclusions. Occasionally cells adjacent to those having inclusions contained needle-like formations. The whorled inclusions appeared in ultrathin

  11. Detection and Measurement of the Intracellular Calcium Variation in Follicular Cells

    Directory of Open Access Journals (Sweden)

    Ana M. Herrera-Navarro

    2014-01-01

    Full Text Available This work presents a new method for measuring the variation of intracellular calcium in follicular cells. The proposal consists in two stages: (i the detection of the cell’s nuclei and (ii the analysis of the fluorescence variations. The first stage is performed via watershed modified transformation, where the process of labeling is controlled. The detection process uses the contours of the cells as descriptors, where they are enhanced with a morphological filter that homogenizes the luminance variation of the image. In the second stage, the fluorescence variations are modeled as an exponential decreasing function, where the fluorescence variations are highly correlated with the changes of intracellular free Ca2+. Additionally, it is introduced a new morphological called medium reconstruction process, which helps to enhance the data for the modeling process. This filter exploits the undermodeling and overmodeling properties of reconstruction operators, such that it preserves the structure of the original signal. Finally, an experimental process shows evidence of the capabilities of the proposal.

  12. The Role of Intracellular Calcium for the Development and Treatment of Neuroblastoma

    Energy Technology Data Exchange (ETDEWEB)

    Satheesh, Noothan Jyothi; Büsselberg, Dietrich, E-mail: dib2015@qatar-med.cornell.edu [Weill Cornell Medical College in Qatar, Qatar Foundation-Education City, POB 24144, Doha (Qatar)

    2015-05-22

    Neuroblastoma is the second most common paediatric cancer. It develops from undifferentiated simpatico-adrenal lineage cells and is mostly sporadic; however, the aetiology behind the development of neuroblastoma is still not fully understood. Intracellular calcium ([Ca{sup 2+}]{sub i}) is a secondary messenger which regulates numerous cellular processes and, therefore, its concentration is tightly regulated. This review focuses on the role of [Ca{sup 2+}]{sub i} in differentiation, apoptosis and proliferation in neuroblastoma. It describes the mechanisms by which [Ca{sup 2+}]{sub i} is regulated and how it modulates intracellular pathways. Furthermore, the importance of [Ca{sup 2+}]{sub i} for the function of anti-cancer drugs is illuminated in this review as [Ca{sup 2+}]{sub i} could be a target to improve the outcome of anti-cancer treatment in neuroblastoma. Overall, modulations of [Ca{sup 2+}]{sub i} could be a key target to induce apoptosis in cancer cells leading to a more efficient and effective treatment of neuroblastoma.

  13. Association of serine protease with the rise of intracellular calcium in cytotoxic T lymphocytes.

    Science.gov (United States)

    Koo, G C; Luk, Y; Talento, A; Wu, J; Sirotina, A; Fischer, P A; Blake, J T; Nguyen, M P; Parsons, W; Poe, M

    1996-12-15

    The precise role of the granular enzyme A (granzyme A), a serine protease, in the lytic process of cytotoxic T lymphocytes (CTL) is not clear. We have recently constructed a CTL line transfected with the antisense gene of granzyme A (a-GrA). These a-GrA CTL had lower GrA activity as well as decreased lytic activities, as measured by 51Cr and by DNA degradation assays. Furthermore, at low effector:target ratio (1:8) in prolonged lytic assays, they could not lyse targets as rapidly as the control CTL. When we examined their ability to exocytose BLT (CBZ-L-lys-thiobenzyl)-esterase in the presence of anti-CD3 antibody, the a-GrA CTL exocytosed poorly compared to the parental CTL or control transfectant with a CAT gene. Most strikingly, a-GrA cells could not release intracellular stores of Ca2+ in response to anti-CD3 induction, although the Ca2+ flux was normal when they were stimulated with ionomycin. When the parental CTL was treated with a specific benzyllactam inhibitor of BLT-esterase or N-tosyl-L-phenylalanylchloromethyl ketone, the Ca2+ flux induced by anti-CD3 was also suppressed. We propose that granzyme A is involved in the signal transduction pathway that causes the rise of the intracellular calcium.

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

    Science.gov (United States)

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

    2012-05-01

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

  15. Dehydroepiandrosterone inhibits intracellular calcium release in beta-cells by a plasma membrane-dependent mechanism.

    Science.gov (United States)

    Liu, Dongmin; Ren, Min; Bing, Xinyu; Stotts, Corey; Deorah, Sundeep; Love-Homan, Laurie; Dillon, Joseph S

    2006-08-01

    Both dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEAS) affect glucose stimulated insulin secretion, though their cellular mechanisms of action are not well characterized. We tested the hypothesis that human physiological concentrations of DHEA alter insulin secretion by an action initiated at the plasma membrane of beta-cells. DHEA alone had no effect on intracellular calcium concentration ([Ca(2+)](i)) in a rat beta-cell line (INS-1). However, it caused an immediate and dose-dependent inhibition of carbachol-induced Ca(2+) release from intracellular stores, with a 25% inhibition at zero. One nanometer DHEA. DHEA also inhibited the Ca(2+) mobilizing effect of bombesin (29% decrease), but did not inhibit the influx of extracellular Ca(2+) evoked by glyburide (100 microM) or glucose (15 mM). The steroids (androstenedione, 17-alpha-hydroxypregnenolone, and DHEAS) had no inhibitory effect on carbachol-induced intracellular Ca(2+) release. The action of DHEA depended on a signal initiated at the plasma membrane, since membrane impermeant DHEA-BSA complexes also inhibited the carbachol effect on [Ca(2+)](i) (39% decrease). The inhibition of carbachol-induced Ca(2+) release by DHEA was blocked by pertussis toxin (PTX). DHEA also inhibited the carbachol induction of phosphoinositide generation, with a maximal inhibition at 0.1 nM DHEA. Furthermore, DHEA inhibited insulin secretion induced by carbachol in INS-1 cells by 25%, and in human pancreatic islets by 53%. Taken together, this is the first report showing that human physiological concentrations of DHEA decrease agonist-induced Ca(2+) release by a rapid, non-genomic mechanism in INS-1 cells. Furthermore, these data provide evidence consistent with the existence of a specific plasma membrane DHEA receptor, mediating this signal transduction pathway by pertussis toxin-sensitive G-proteins.

  16. Muscarinic signalling affects intracellular calcium concentration during the first cell cycle of sea urchin embryos.

    Science.gov (United States)

    Harrison, P K; Falugi, C; Angelini, C; Whitaker, M J

    2002-06-01

    The existence of a response to acetylcholine (ACh) and cholinomimetic drugs in sea urchin eggs and zygotes was investigated in two sea urchin species: Paracentrotus lividus and Lytechinus pictus. The calcium sensitive fluorescent probe, Fura-2 dextran, was employed to investigate the regulation of cytosolic free calcium concentration ([Ca(2+)](i)) by cholinomimetic drugs in unfertilised and fertilised eggs of both the sea urchin species. Exposure to cholinomimetic agonists/antagonists, either extracellularly or intracellularly, had no effect either on resting [Ca(2+)](i) levels in the unfertilised sea urchin egg, or on the transient [Ca(2+)](i) increase at fertilisation. However, following fertilisation, extracellular application of ACh receptors agonists, such as ACh and carbachol, predominantly muscarinic agonist, but not nicotine, induced a significant increase in [Ca(2+)](i), which was partially inhibited by atropine. As a consequence of exposure after fertilisation to the agonists of ACh receptors, chromatin structure was transiently affected. The hypothesis is proposed that muscarinic receptors may be involved in the (presumably Ca(2+)-dependent) modulation of the nuclear status during the first cell cycles.

  17. 14-3-3 Proteins Buffer Intracellular Calcium Sensing Receptors to Constrain Signaling.

    Directory of Open Access Journals (Sweden)

    Michael P Grant

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

  18. Biochemical and ultrastructural studies suggest that the effects of thapsigargin on human platelets are mediated by changes in intracellular calcium but not by intracellular histamine

    DEFF Research Database (Denmark)

    Saxena, S P; McNicol, A; Becker, A B

    1992-01-01

    -fluoromethyl histidine (alpha-FMH) failed to inhibit Tg-induced aggregation. The intracellular histamine receptor antagonist, N,N-diethyl-2-[4-(phenylmethyl)phenoxy] ethanamine. HCl (DPPE), inhibited Tg-induced aggregation but with IC50 values dependent on the concentration of agonist used. The inhibitory effects...... of DPPE on Tg-induced aggregation were not reversed by the addition of histamine to saponin-permeabilized platelets suggesting non-histamine mediated effects of DPPE on Tg-induced aggregation. Tg stimulated an increase in the cytosolic free calcium concentration which was unaffected by DPPE indicating...... that the effects of DPPE are also not due to the inhibition of mobilization of cytosolic calcium. The ultrastructural studies suggest that the major Tg-induced changes (pseudopod formation and granule centralization) are consistent with a primary role for Tg to mobilize calcium; DPPE had very little effect...

  19. p53 increases intra-cellular calcium release by transcriptional regulation of calcium channel TRPC6 in GaQ3-treated cancer cells.

    Directory of Open Access Journals (Sweden)

    Esha Madan

    Full Text Available p53 and calcium signaling are inter-dependent and are known to show both synergistic and antagonistic effects on each other in the cellular environment. However, no molecular mechanism or cellular pathway is known which shows direct regulation between these important cellular signaling molecules. Here we have shown that in cancer cells treated with anti-neoplastic drug GaQ3, p53, there is an increase in intracellular calcium levels by transcriptional regulation of a novel calcium channel gene TRPC6. p53 directly binds to a 22 bp response element in the TRPC6 gene promoter and increase its mRNA and protein expression. Over-expression of TRPC6 results in calcium-dependent apoptotic death and activation of apoptotic genes in a variety of cancer cells. This research work shows that p53 and its transcriptional activity is critical in regulation of calcium signaling and an increase in the intracellular calcium level might be one of the anti-cancer strategies to induce apoptosis in cancer cells.

  20. p53 increases intra-cellular calcium release by transcriptional regulation of calcium channel TRPC6 in GaQ3-treated cancer cells.

    Science.gov (United States)

    Madan, Esha; Gogna, Rajan; Keppler, Bernhard; Pati, Uttam

    2013-01-01

    p53 and calcium signaling are inter-dependent and are known to show both synergistic and antagonistic effects on each other in the cellular environment. However, no molecular mechanism or cellular pathway is known which shows direct regulation between these important cellular signaling molecules. Here we have shown that in cancer cells treated with anti-neoplastic drug GaQ3, p53, there is an increase in intracellular calcium levels by transcriptional regulation of a novel calcium channel gene TRPC6. p53 directly binds to a 22 bp response element in the TRPC6 gene promoter and increase its mRNA and protein expression. Over-expression of TRPC6 results in calcium-dependent apoptotic death and activation of apoptotic genes in a variety of cancer cells. This research work shows that p53 and its transcriptional activity is critical in regulation of calcium signaling and an increase in the intracellular calcium level might be one of the anti-cancer strategies to induce apoptosis in cancer cells.

  1. Azelnidipine prevents cardiac dysfunction in streptozotocin-diabetic rats by reducing intracellular calcium accumulation, oxidative stress and apoptosis

    Directory of Open Access Journals (Sweden)

    Kain Vasundhara

    2011-11-01

    Full Text Available Abstract Background Numerous evidences suggest that diabetic heart is characterized by compromised ventricular contraction and prolonged relaxation attributable to multiple causative factors including calcium accumulation, oxidative stress and apoptosis. Therapeutic interventions to prevent calcium accumulation and oxidative stress could be therefore helpful in improving the cardiac function under diabetic condition. Methods This study was designed to examine the effect of long-acting calcium channel blocker (CCB, Azelnidipine (AZL on contractile dysfunction, intracellular calcium (Ca2+ cycling proteins, stress-activated signaling molecules and apoptosis on cardiomyocytes in diabetes. Adult male Wistar rats were made diabetic by a single intraperitoneal (IP injection of streptozotocin (STZ. Contractile functions were traced from live diabetic rats to isolated individual cardiomyocytes including peak shortening (PS, time-to-PS (TPS, time-to-relengthening (TR90, maximal velocity of shortening/relengthening (± dL/dt and intracellular Ca2+ fluorescence. Results Diabetic heart showed significantly depressed PS, ± dL/dt, prolonged TPS, TR90 and intracellular Ca2+ clearing and showed an elevated resting intracellular Ca2+. AZL itself exhibited little effect on myocyte mechanics but it significantly alleviated STZ-induced myocyte contractile dysfunction. Diabetes increased the levels of superoxide, enhanced expression of the cardiac damage markers like troponin I, p67phox NADPH oxidase subunit, restored the levels of the mitochondrial superoxide dismutase (Mn-SOD, calcium regulatory proteins RyR2 and SERCA2a, and suppressed the levels of the anti-apoptotic Bcl-2 protein. All of these STZ-induced alterations were reconciled by AZL treatment. Conclusion Collectively, the data suggest beneficial effect of AZL in diabetic cardiomyopathy via altering intracellular Ca2+ handling proteins and preventing apoptosis by its antioxidant property.

  2. The cannabinoid agonist WIN55,212-2 increases intracellular calcium via CB1 receptor coupling to Gq/11 G proteins

    OpenAIRE

    Lauckner, Jane E.; Hille, Bertil; Mackie, Ken

    2005-01-01

    Central nervous system responses to cannabis are primarily mediated by CB1 receptors, which couple preferentially to Gi/o G proteins. Here, we used calcium photometry to monitor the effect of CB1 activation on intracellular calcium concentration. Perfusion with 5 μM CB1 aminoalkylindole agonist, WIN55,212-2 (WIN), increased intracellular calcium by several hundred nanomolar in human embryonic kidney 293 cells stably expressing CB1 and in cultured hippocampal neurons. The increase was blocked ...

  3. Nicotine-induced embryonic malformations mediated by apoptosis from increasing intracellular calcium and oxidative stress.

    Science.gov (United States)

    Zhao, Zhiyong; Reece, E Albert

    2005-10-01

    Tobacco smoking by women during pregnancy increases the risk of congenital birth defects in the infants. Among the smoke products, nicotine is believed to be the major teratogenic factor that perturbs embryonic development. However, the role of nicotine in embryonic malformations has not been addressed, and the mechanisms by which nicotine affects embryonic development remain to be delineated. To investigate the effects of nicotine on early embryogenesis, murine embryos at embryonic day (E) 8.5 were dissected out of the uteri, cultured in a roller bottle system, and treated with nicotine (0.6-6 microM) or vehicle. Embryonic morphogenesis and growth were examined in terms of structural morphology and crown/rump length, respectively. Programmed cell death (apoptosis) was assessed using LysoTracker Red staining of whole mount embryos and TUNEL assay of tissue sections. Changes in intracellular calcium concentration ([Ca2+]i) and reactive oxygen species (ROS) production were assessed using fluorescent dyes (Flu-4, AM; H2DCFDA, respectively) under a confocal microscope. To further investigate the role of intracellular calcium and ROS in nicotine-induced embryopathy, embryos were treated with BAPTA-AM (2 microM) to inhibit [Ca2+]i elevation and ascorbic acid (vitamin C; 100 microg/ml) to scavenge ROS in presence of nicotine (6 microM). The embryos treated with nicotine in 3-6 microM were smaller than those treated with vehicle. Most of the embryos had open neural tube in the anterior (brain) regions. The embryos treated with 6 microM nicotine also exhibited severe defects in the posterior trunk, resembling caudal dysplasia. Excessive apoptosis was observed in the deformed structures. Significant increases in [Ca2+]i and ROS were seen in the tissues that had higher levels of apoptosis. Furthermore, inhibition of [Ca2+]i and scavenging of ROS significantly reduced embryonic malformation and apoptotic rates in the embryos. Nicotine affects embryonic development in a

  4. Fluorochloridone induces primary cultured Sertoli cells apoptosis: Involvement of ROS and intracellular calcium ions-mediated ERK1/2 activation.

    Science.gov (United States)

    Liu, Luqing; Chang, Xiuli; Zhang, Yubin; Wu, Chunhua; Li, Rui; Tang, Liming; Zhou, Zhijun

    2018-03-01

    Fluorochloridone (FLC) is a widely used pyrrolidone selective herbicide and reported to induce testis injuries in male rats, but the underlying mechanism is largely unknown. In the present study, primary-cultured Sertoli cells were exposed to FLC at the concentration of 0-10.00μM to study the mechanism of FLC-induced apoptosis. The roles of ROS, intracellular calcium, endoplasmic reticulum (ER), and ERK1/2 were looked at with ROS scavenger N-acetyl-cysteine (NAC), intracellular calcium chelator BAPTA-AM, ER calcium depleting agent thapsigargin (TG), and ERK1/2 inhibitor U0126, respectively. FLC induced dose-dependent apoptosis increase as well as the elevation in levels of ROS, intracellular calcium, and ERK1/2 activation. FLC treatment led to constantly increasing apoptotic rates and ERK1/2 activation over time, while inversed-V shaped change tendencies of ROS and intracellular calcium levels were observed. FLC-induced ROS generation disrupted the intracellular calcium homeostasis by attacking the ER, and the elevated intracellular calcium levels resulted in ERK1/2 over-phosphorylation and consequently promoted Sertoli cell apoptosis. Taken together, ROS and intracellular calcium-mediated ERK1/2 activation led to FLC-induced Sertoli cell apoptosis. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Activation of Src and release of intracellular calcium by phosphatidic acid during Xenopus laevis fertilization

    Science.gov (United States)

    Bates, Ryan C.; Fees, Colby P.; Holland, William L.; Winger, Courtney C.; Batbayar, Khulan; Ancar, Rachel; Bergren, Todd; Petcoff, Douglas; Stith, Bradley J.

    2014-01-01

    We report a new step in the fertilization in Xenopus laevis which has been found to involve activation of Src tyrosine kinase to stimulate phospholipase C-γ (PLC- γ) which increases inositol 1,4,5-trisphosphate (IP3) to release intracellular calcium ([Ca]i). Molecular species analysis and mass measurements suggested that sperm activate phospholipase D (PLD) to elevate phosphatidic acid (PA). We now report that PA mass increased 2.7 fold by 1 minute after insemination and inhibition of PA production by two methods inhibited activation of Src and PLCγ, increased [Ca]i and other fertilization events. As compared to 14 other lipids, PA strongly bound Xenopus Src but not PLCγ. Addition of synthetic PA activated egg Src (an action requiring intact lipid rafts) and PLCγ as well as doubling the amount of PLCγ in rafts. In the absence of elevated [Ca]i, PA addition elevated IP3 mass to levels equivalent to that induced by sperm (but twice that achieved by calcium ionophore). Finally, PA induced [Ca]i release that was blocked by an IP3 receptor inhibitor. As only PLD1b message was detected, and Western blotting did not detect PLD2, we suggest that sperm activate PLD1b to elevate PA which then binds to and activates Src leading to PLCγ stimulation, IP3 elevation and [Ca]i release. Due to these and other studies, PA may also play a role in membrane fusion events such as sperm-egg fusion, cortical granule exocytosis, the elevation of phosphatidylinositol 4,5-bisphosphate and the large, late increase in sn 1,2-diacylglycerol in fertilization. PMID:24269904

  6. Effects of potassium concentration on firing patterns of low-calcium epileptiform activity in anesthetized rat hippocampus: inducing of persistent spike activity.

    Science.gov (United States)

    Feng, Zhouyan; Durand, Dominique M

    2006-04-01

    It has been shown that a low-calcium high-potassium solution can generate ictal-like epileptiform activity in vitro and in vivo. Moreover, during status epileptiform activity, the concentration of [K+]o increases, and the concentration of [Ca2+]o decreases in brain tissue. Therefore we tested the hypothesis that long-lasting persistent spike activity, similar to one of the patterns of status epilepticus, could be generated by a high-potassium, low-calcium solution in the hippocampus in vivo. Artificial cerebrospinal fluid was perfused over the surface of the exposed left dorsal hippocampus of anesthetized rats. A stimulating electrode and a recording probe were placed in the CA1 region. By elevating K+ concentration from 6 to 12 mM in the perfusate solution, the typical firing pattern of low-calcium ictal bursts was transformed into persistent spike activity in the CA1 region with synaptic transmission being suppressed by calcium chelator EGTA. The activity was characterized by double spikes repeated at a frequency approximately 4 Hz that could last for >1 h. The analysis of multiple unit activity showed that both elevating [K+]o and lowering [Ca2+]o decreased the inhibition period after the response of paired-pulse stimulation, indicating a suppression of the after-hyperpolarization (AHP) activity. These results suggest that persistent status epilepticus-like spike activity can be induced by nonsynaptic mechanisms when synaptic transmission is blocked. The unique double-spike pattern of this activity is presumably caused by higher K+ concentration augmenting the frequency of typical low-calcium nonsynaptic burst activity.

  7. Estradiol coupling to human monocyte nitric oxide release is dependent on intracellular calcium transients: evidence for an estrogen surface receptor.

    Science.gov (United States)

    Stefano, G B; Prevot, V; Beauvillain, J C; Fimiani, C; Welters, I; Cadet, P; Breton, C; Pestel, J; Salzet, M; Bilfinger, T V

    1999-10-01

    We tested the hypothesis that estrogen acutely stimulates constitutive NO synthase (cNOS) activity in human peripheral monocytes by acting on an estrogen surface receptor. NO release was measured in real time with an amperometric probe. 17beta-estradiol exposure to monocytes stimulated NO release within seconds in a concentration-dependent manner, whereas 17alpha-estradiol had no effect. 17beta-estradiol conjugated to BSA (E2-BSA) also stimulated NO release, suggesting mediation by a membrane surface receptor. Tamoxifen, an estrogen receptor inhibitor, antagonized the action of both 17beta-estradiol and E2-BSA, whereas ICI 182,780, a selective inhibitor of the nuclear estrogen receptor, had no effect. We further showed, using a dual emission microfluorometry in a calcium-free medium, that the 17beta-estradiol-stimulated release of monocyte NO was dependent on the initial stimulation of intracellular calcium transients in a tamoxifen-sensitive process. Leeching out the intracellular calcium stores abolished the effect of 17beta-estradiol on NO release. RT-PCR analysis of RNA obtained from the cells revealed a strong estrogen receptor-alpha amplification signal and a weak beta signal. Taken together, a physiological dose of estrogen acutely stimulates NO release from human monocytes via the activation of an estrogen surface receptor that is coupled to increases in intracellular calcium.

  8. Biochemical and ultrastructural studies suggest that the effects of thapsigargin on human platelets are mediated by changes in intracellular calcium but not by intracellular histamine

    DEFF Research Database (Denmark)

    Saxena, S P; McNicol, A; Becker, A B

    1992-01-01

    was observed at 1 microM Tg. Preincubation of platelets with inhibitors of histamine metabolizing enzymes had little effect on intracellular histamine levels in platelets stimulated by 0.5 microM Tg. In addition, the inhibitors of histidine decarboxylase (HDC), alpha-methyl histidine (alpha-MH) and alpha......-fluoromethyl histidine (alpha-FMH) failed to inhibit Tg-induced aggregation. The intracellular histamine receptor antagonist, N,N-diethyl-2-[4-(phenylmethyl)phenoxy] ethanamine. HCl (DPPE), inhibited Tg-induced aggregation but with IC50 values dependent on the concentration of agonist used. The inhibitory effects...... of DPPE on Tg-induced aggregation were not reversed by the addition of histamine to saponin-permeabilized platelets suggesting non-histamine mediated effects of DPPE on Tg-induced aggregation. Tg stimulated an increase in the cytosolic free calcium concentration which was unaffected by DPPE indicating...

  9. Effect of Tetrodotoxin from Crude Puffer Fish (Tetraodon fluviatilis Liver Extract on Intracellular Calcium Level and Apoptosis of HeLa Cell Culture

    Directory of Open Access Journals (Sweden)

    Natanael Untario

    2017-01-01

    Full Text Available Cervical cancer is the third most commonly diagnosed cancer and fourth leading cause of women death with 8% of total death caused by cancer in women in 2008. Tetrodotoxin (TTX is a potent neurotoxin found in inner organs puffer fish, with the specific mechanism of sodium channel blocking, and widely used for research purposes. Previous reports claimed that TTX has the capability of inhibiting the metastatic process of cancer and apoptotic effect. Studies also show that apoptosis is a process involving the increase of intracellular calcium level, yet the connection between TTX and increase of intracellular calcium level, therefore triggering apoptosis, has not been established. This is an experimental study with post test only control group design, carried out by exposing HeLa cell culture to a crude liver extract of a puffer fish species, Tetraodon fluviatilis. Crude puffer fish liver extract is administered into HeLa cell culture well in different concentrations 10-4, 10-2, and 10-1. Intracellular calcium level and apoptosis were then measured after 18 hours of incubation. Measurements of intracellular calcium level were done by using CLSM with Fura-2AM staining, and apoptosis by using flowcytometry with Annexin V/PI.  The result shows that there is a significant difference between samples both in intracellular calcium (p < 0.05 and apoptosis (p < 0,05. Both intracellular calcium and apoptosis levels are proportional to liver fish extract concentration. Pearson’s correlation test shows correlation between treatment and intracellular calcium levels (p = 0.000, between treatment and apoptosis (p = 0.002, but not between intracellular calcium and apoptosis (p = 0.05. These results suggest that TTX induces an increase in intracellular calcium level and apoptosis, but calcium pathway is not the sole cause of the apoptosis.

  10. The influence of statins on the free intracellular calcium concentration in human umbilical vein endothelial cells

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    Figulla Hans R

    2004-05-01

    Full Text Available Abstract Background Statins are cholesterol-lowering drugs that are widely used to reduce the risk of cardiac infarction. Their beneficial clinical effects, however, are not restricted to their influence on cholesterol production. As several studies have shown that they have a potency of relaxing blood vessels. Methods We measured the effects of statins on the intracellular free calcium concentration ([Ca2+]i in human umbilical vein endothelial cells (HUVEC after acute application and 24-h-preincubation of statins. Results Incubation of the cells for 24 h with cerivastatin or fluvastatin significantly increased the resting [Ca2+]i. For cerivastatin this effect manifested at a concentration of 1 μM. Increase of resting [Ca2+]i in the presence of cerivastatin also occurred when the nitric oxide synthase was inhibited. Transient Ca2+ release induced by histamine was not affected. Conclusions The increase of resting [Ca2+]i after incubation with cerivastatin or fluvastatin may provide an explanation for the direct effects of statins on the endothelial-dependent vasodilatation and restoration of endothelial activity in vivo.

  11. Genetic analysis of hyperemesis gravidarum reveals association with intracellular calcium release channel (RYR2).

    Science.gov (United States)

    Fejzo, Marlena Schoenberg; Myhre, Ronny; Colodro-Conde, Lucía; MacGibbon, Kimber W; Sinsheimer, Janet S; Reddy, M V Prasad Linga; Pajukanta, Päivi; Nyholt, Dale R; Wright, Margaret J; Martin, Nicholas G; Engel, Stephanie M; Medland, Sarah E; Magnus, Per; Mullin, Patrick M

    2017-01-05

    Hyperemesis Gravidarum (HG), severe nausea/vomiting in pregnancy (NVP), can cause poor maternal/fetal outcomes. Genetic predisposition suggests the genetic component is essential in discovering an etiology. We performed whole-exome sequencing of 5 families followed by analysis of variants in 584 cases/431 controls. Variants in RYR2 segregated with disease in 2 families. The novel variant L3277R was not found in any case/control. The rare variant, G1886S was more common in cases (p = 0.046) and extreme cases (p = 0.023). Replication of G1886S using Norwegian/Australian data was supportive. Common variants rs790899 and rs1891246 were significantly associated with HG and weight loss. Copy-number analysis revealed a deletion in a patient. RYR2 encodes an intracellular calcium release channel involved in vomiting, cyclic-vomiting syndrome, and is a thyroid hormone target gene. Additionally, RYR2 is a downstream drug target of Inderal, used to treat HG and CVS. Thus, herein we provide genetic evidence for a pathway and therapy for HG. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  12. Single organelle fret-based analysis of intracellular calcium: different effects of presinilis carrying Familial Alzheimer's Disease mutations

    OpenAIRE

    wong, andrea kuan cie

    2014-01-01

    Calcium (Ca2+) is one of the major intracellular messengers that impacts nearly every aspect of cell life. In particular, it plays essential roles in neuronal development, synaptic transmission and plasticity, as well as in the regulation of metabolic pathways and cell fate decisions. The first goal of my work was to study more in details the Golgi apparatus (GA), as an intracellular Ca2+ store. The Golgi complex may store up to 5% of the total cellular Ca2+ at higher concentrations an...

  13. Deglacial Millennial-scale Calcium Carbonate Spikes in the North Pacific Ocean

    Science.gov (United States)

    Chikamoto, M. O.; Timmermann, A.; Harada, N.; Okazaki, Y.

    2015-12-01

    Numerous paleoproxy records from the subarctic Pacific Ocean show two very pronounced deglacial peaks in calcium carbonate content for the Heinrich 1/ Bolling-Allerod (H1-BA) transition (at 14 ka) and for the Younger Dryas/Preboreal transition (at 11 ka). Focusing on the H1-BA transition, some model simulations capture the North Pacific shift from ventilated to stratified conditions and from cooling to warming conditions via oceanic and atmospheric connections between Atlantic and Pacific Oceans. To test the impact of these physical scenarios (variations in ocean stratification and temperature during the H1-BA transition) on calcite production or preservation, we conduct a series of idealized experiments using the Earth System Model Intermediate Complexity LOVECLIM. The variations in North Pacific Ocean stratification by anomalous freshwater forcing show low calcite productivity in associated with the subsurface nutrient decline. On the other hand, the rapid H1-BA warming of the North Pacific Ocean induced by anomalous heat forcing in turn increases calcite productivity due to the temperature-dependent growth rate of phytoplankton. These results suggest the possibility that the millennial-scale calcium carbonate peaks are the result of surface biogeochemical responses to the climate transition, not by the deep circulation response.

  14. Calcium Imaging Reveals Coordinated Simple Spike Pauses in Populations of Cerebellar Purkinje Cells

    Directory of Open Access Journals (Sweden)

    Jorge E. Ramirez

    2016-12-01

    Full Text Available The brain’s control of movement is thought to involve coordinated activity between cerebellar Purkinje cells. The results reported here demonstrate that somatic Ca2+ imaging is a faithful reporter of Na+-dependent “simple spike” pauses and enables us to optically record changes in firing rates in populations of Purkinje cells in brain slices and in vivo. This simultaneous calcium imaging of populations of Purkinje cells reveals a striking spatial organization of pauses in Purkinje cell activity between neighboring cells. The source of this organization is shown to be the presynaptic gamma-Aminobutyric acid producing (GABAergic network, and blocking ionotropic gamma-Aminobutyric acid receptor (GABAARs abolishes the synchrony. These data suggest that presynaptic interneurons synchronize (inactivity between neighboring Purkinje cells, and thereby maximize their effect on downstream targets in the deep cerebellar nuclei.

  15. Mango Fruit Extracts Differentially Affect Proliferation and Intracellular Calcium Signalling in MCF-7 Human Breast Cancer Cells

    OpenAIRE

    Taing, Meng-Wong; Pierson, Jean-Thomas; Shaw, Paul N.; Dietzgen, Ralf G.; Roberts-Thomson, Sarah J.; Gidley, Michael J.; Monteith, Gregory R.

    2015-01-01

    The assessment of human cancer cell proliferation is a common approach in identifying plant extracts that have potential bioactive effects. In this study, we tested the hypothesis that methanolic extracts of peel and flesh from three archetypal mango cultivars, Irwin (IW), Nam Doc Mai (NDM), and Kensington Pride (KP), differentially affect proliferation, extracellular signal-regulated kinase (ERK) activity, and intracellular calcium ([Ca2+]I) signalling in MCF-7 human breast cancer cells. Man...

  16. Cell growth, intracellular calcium concentration and metabolic cooperation measured in cells exposed to 50 Hz electromagnetic fields

    International Nuclear Information System (INIS)

    Skauli, K.S.

    1996-08-01

    Colony-forming efficiency, DNA/protein and DNA/cell were measured in cells exposed to magnetic fields of 0.2 and 1 mT at a frequency of 50 Hz. Intracellular calcium concentrations were measured in cells exposed to 0.3 and 1 mT at 50 Hz. Metabolic cooperation was measured in cells exposed to 1 mT at 50 Hz. No significant effects of the fields were observed. 20 refs., 10 figs

  17. Intracellular calcium signals display an avalanche-like behavior over multiple lengthscales.

    Directory of Open Access Journals (Sweden)

    Lucía eLopez

    2012-09-01

    Full Text Available Many natural phenomena display "self-organized criticality'' (SOC. This refers to spatially extended systems for which patterns of activity characterized by different lengthscales can occur with a probability density that follows a power law with pattern size. Differently from power laws at phase transitions, systems displaying SOC do not need the tuning of an external parameter. Here we analyze intracellular calcium Ca2+ signals, a key component of the signaling toolkit of almost any cell type. Ca2+ signals can either be spatially restricted (local or propagate throughout the cell (global. Different models have suggested that the transition from local to global signals is similar to that of directed percolation. Directed percolation has been associated, in turn, to the appearance of self-organized criticality. In this paper we discuss these issues within the framework of simple models of Ca2+ signal propagation. We also analyze the size distribution of local signals ("puffs'' observed in immature Xenopus Laevis oocytes. The puff amplitude distribution obtained from observed local signals is not Gaussian with a noticeable fraction of large size events. The experimental distribution of puff areas in the spatio-temporal record of the image has a long tail that is approximately log-normal. The distribution can also be fitted with a power law relationship albeit with a smaller goodness of fit. The power law behavior is encountered within a simple model that includes some coupling among individual signals for a wide range of parameter values. An analysis of the model shows that a global elevation of the Ca2+ concentration plays a major role in determining whether the puff size distribution is long-tailed or not. This suggests that Ca2+-clearing from the cytosol is key to determine whether IP3-mediated Ca2+ signals can display a SOC-like behavior or not.

  18. Dysregulation of intracellular calcium transporters in animal models of sepsis-induced cardiomyopathy.

    Science.gov (United States)

    Hobai, Ion A; Edgecomb, Jessica; LaBarge, Kara; Colucci, Wilson S

    2015-01-01

    Sepsis-induced cardiomyopathy (SIC) develops as the result of myocardial calcium (Ca) dysregulation. Here we reviewed all published studies that quantified the dysfunction of intracellular Ca transporters and the myofilaments in animal models of SIC. Cardiomyocytes isolated from septic animals showed, invariably, a decreased twitch amplitude, which is frequently caused by a decrease in the amplitude of cellular Ca transients (ΔCai) and sarcoplasmic reticulum (SR) Ca load (CaSR). Underlying these deficits, the L-type Ca channel is downregulated, through mechanisms that may involve adrenomedullin-mediated redox signaling. The SR Ca pump is also inhibited, through oxidative modifications (sulfonylation) of one reactive thiol group (on Cys) and/or modulation of phospholamban. Diastolic Ca leak of ryanodine receptors is frequently increased. In contrast, Na/Ca exchange inhibition may play a partially compensatory role by increasing CaSR and ΔCai. The action potential is usually shortened. Myofilaments show a bidirectional regulation, with decreased Ca sensitivity in milder forms of disease (due to troponin I hyperphosphorylation) and an increase (redox mediated) in more severe forms. Most deficits occurred similarly in two different disease models, induced by either intraperitoneal administration of bacterial lipopolysaccharide or cecal ligation and puncture. In conclusion, substantial cumulative evidence implicates various Ca transporters and the myofilaments in SIC pathology. What is less clear, however, are the identity and interplay of the signaling pathways that are responsible for Ca transporters dysfunction. With few exceptions, all studies we found used solely male animals. Identifying sex differences in Ca dysregulation in SIC becomes, therefore, another priority.

  19. Dysregulation of intracellular calcium transporters in animal models of sepsis induced cardiomyopathy

    Science.gov (United States)

    Hobai, Ion A.; Edgecomb, Jessica; LaBarge, Kara; Colucci, Wilson S.

    2014-01-01

    Sepsis induced cardiomyopathy (SIC) develops as the result of myocardial calcium (Ca2+) dysregulation. Here we reviewed all published studies that quantified the dysfunction of intracellular Ca2+ transporters and the myofilaments in animal models of SIC. Cardiomyocytes isolated from septic animals showed, invariably, a decreased twitch amplitude, which is frequently caused by a decrease in the amplitude of cellular Ca2+ transients (ΔCai) and sarcoplasmic reticulum (SR) Ca2+ load (CaSR). Underlying these deficits, the L-type Ca2+ channel is downregulated, through mechanisms that may involve adrenomedullin-mediated redox signaling. SR Ca2+ pump (SERCA) is also inhibited, through oxidative modifications (sulphonylation) of one reactive thiol group (on Cys674), and/or modulation of phospholamban. Diastolic Ca2+ leak of ryanodine receptors is frequently increased. In contrast, Na+/Ca2+ exchange inhibition may play a partially compensatory role by increasing CaSR and ΔCai. The action potential is usually shortened. Myofilaments show a bidirectional regulation, with decreased Ca2+ sensitivity in milder forms of disease (due to troponin I hyperphosphorylation) and a (redox mediated) increase in more severe forms. Most deficits occurred similarly in two different disease models, induced by either intraperitoneal administration of bacterial lipopolysaccharide (LPS) or cecal ligation and puncture (CLP). In conclusion, substantial cumulative evidence implicates various Ca2+ transporters and the myofilaments in SIC pathology. What is less clear, however, is the identity and interplay of the signaling pathways that are responsible for Ca2+ transporters dysfunction. With few exceptions, all studies we found used solely male animals. Identifying sex differences in Ca2+ dysregulation in SIC becomes, therefore, another priority. PMID:25186837

  20. Hearts of surviving MLP-KO mice show transient changes of intracellular calcium handling.

    Science.gov (United States)

    Kemecsei, Péter; Miklós, Zsuzsanna; Bíró, Tamás; Marincsák, Rita; Tóth, Balázs I; Komlódi-Pásztor, Edina; Barnucz, Eniko; Mirk, Eva; Van der Vusse, Ger J; Ligeti, László; Ivanics, Tamás

    2010-09-01

    The muscle Lim protein knock-out (MLP-KO) mouse model is extensively used for studying the pathophysiology of dilated cardiomyopathy. However, explanation is lacking for the observed long survival of the diseased mice which develop until adulthood despite the gene defect, which theoretically predestines them to early death due to heart failure. We hypothesized that adaptive changes of cardiac intracellular calcium (Ca(i)(2+)) handling might explain the phenomenon. In order to study the progression of changes in cardiac function and Ca(i)(2+) cycling, myocardial Ca(i)(2+)-transients recorded by Indo-1 surface fluorometry were assessed with concomitant measurement of hemodynamic performance in isolated Langendorff-perfused hearts of 3- and 9-month old MLP-KO animals. Hearts were challenged with beta-agonist isoproterenol and the sarcoplasmic reticular Ca(2+)-ATPase (SERCA2a) inhibitor cyclopiazonic acid (CPA). Cardiac mRNA content and levels of key Ca(2+) handling proteins were also measured. A decline in lusitropic function was observed in 3-month old, but not in 9-month old MLP-KO mice under unchallenged conditions. beta-adrenergic responses to isoproterenol were similar in all the studied groups. The CPA induced an increase in end-diastolic Ca(i)(2+)-level and a decrease in Ca(2+)-sequestration capacity in 3-month old MLP-KO mice compared to age-matched controls. This unfavorable condition was absent at 9 months of age. SERCA2a expression was lower in 3-month old MLP-KO than in the corresponding controls and in 9-month old MLP-KO hearts. Our results show time-related recovery of hemodynamic function and an age-dependent compensatory upregulation of Ca(i)(2+) handling in hearts of MLP-KO mice, which most likely involve the normalization of the expression of SERCA2a in the affected hearts.

  1. Intracellular calcium promotes radioresistance of non-small cell lung cancer A549 cells through activating Akt signaling.

    Science.gov (United States)

    Wang, Yiling; He, Jiantao; Zhang, Shenghui; Yang, Qingbo

    2017-03-01

    Radiotherapy is a major therapeutic approach in non-small cell lung cancer but is restricted by radioresistance. Although Akt signaling promotes radioresistance in non-small cell lung cancer, it is not well understood how Akt signaling is activated. Since intracellular calcium (Ca 2+ ) could activate Akt in A549 cells, we investigated the relationship between intracellular calcium (Ca 2+ ) and Akt signaling in radioresistant A549 cells by establishing radioresistant non-small cell lung cancer A549 cells. The radioresistant cell line A549 was generated by dose-gradient irradiation of the parental A549 cells. The cell viability, proliferation, and apoptosis were, respectively, assessed using the cell counting kit-8, EdU labeling, and flow cytometry analysis. The phosphorylation of Akt was evaluated by Western blotting, and the intracellular Ca 2+ concentration was assessed by Fluo 4-AM. The radioresistant A549 cells displayed mesenchymal morphology. After additional irradiation, the radioresistant A549 cells showed decreased cell viability and proliferation but increased apoptosis. Moreover, the intracellular Ca 2+ concentration and the phosphorylation level on the Akt473 site in radioresistant A549 cells were higher than those in original cells, whereas the percentage of apoptosis in radioresistant A549 cells was less. All these results could be reversed by verapamil. In conclusion, our study found that intracellular Ca 2+ could promote radioresistance of non-small cell lung cancer cells through phosphorylating of Akt on the 473 site, which contributes to a better understanding on the non-small cell lung cancer radioresistance, and may provide a new target for radioresistance management.

  2. Miro1 Regulates Activity-Driven Positioning of Mitochondria within Astrocytic Processes Apposed to Synapses to Regulate Intracellular Calcium Signaling

    Science.gov (United States)

    Stephen, Terri-Leigh; Higgs, Nathalie F.; Sheehan, David F.; Al Awabdh, Sana; López-Doménech, Guillermo; Arancibia-Carcamo, I. Lorena

    2015-01-01

    It is fast emerging that maintaining mitochondrial function is important for regulating astrocyte function, although the specific mechanisms that govern astrocyte mitochondrial trafficking and positioning remain poorly understood. The mitochondrial Rho-GTPase 1 protein (Miro1) regulates mitochondrial trafficking and detachment from the microtubule transport network to control activity-dependent mitochondrial positioning in neurons. However, whether Miro proteins are important for regulating signaling-dependent mitochondrial dynamics in astrocytic processes remains unclear. Using live-cell confocal microscopy of rat organotypic hippocampal slices, we find that enhancing neuronal activity induces transient mitochondrial remodeling in astrocytes, with a concomitant, transient reduction in mitochondrial trafficking, mediated by elevations in intracellular Ca2+. Stimulating neuronal activity also induced mitochondrial confinement within astrocytic processes in close proximity to synapses. Furthermore, we show that the Ca2+-sensing EF-hand domains of Miro1 are important for regulating mitochondrial trafficking in astrocytes and required for activity-driven mitochondrial confinement near synapses. Additionally, activity-dependent mitochondrial positioning by Miro1 reciprocally regulates the levels of intracellular Ca2+ in astrocytic processes. Thus, the regulation of intracellular Ca2+ signaling, dependent on Miro1-mediated mitochondrial positioning, could have important consequences for astrocyte Ca2+ wave propagation, gliotransmission, and ultimately neuronal function. SIGNIFICANCE STATEMENT Mitochondria are key cellular organelles that play important roles in providing cellular energy and buffering intracellular calcium ions. The mechanisms that control mitochondrial distribution within the processes of glial cells called astrocytes and the impact this may have on calcium signaling remains unclear. We show that activation of glutamate receptors or increased neuronal

  3. Altered Mitochondrial Metabolism and Mechanosensation in the Failing Heart: Focus on Intracellular Calcium Signaling

    Directory of Open Access Journals (Sweden)

    Aderville Cabassi

    2017-07-01

    Full Text Available The heart consists of millions of cells, namely cardiomyocytes, which are highly organized in terms of structure and function, at both macroscale and microscale levels. Such meticulous organization is imperative for assuring the physiological pump-function of the heart. One of the key players for the electrical and mechanical synchronization and contraction is the calcium ion via the well-known calcium-induced calcium release process. In cardiovascular diseases, the structural organization is lost, resulting in morphological, electrical, and metabolic remodeling owing the imbalance of the calcium handling and promoting heart failure and arrhythmias. Recently, attention has been focused on the role of mitochondria, which seem to jeopardize these events by misbalancing the calcium processes. In this review, we highlight our recent findings, especially the role of mitochondria (dysfunction in failing cardiomyocytes with respect to the calcium machinery.

  4. Intracellular calcium modulates basolateral K(+)-permeability in frog skin epithelium

    DEFF Research Database (Denmark)

    Brodin, Birger; Rytved, K A; Nielsen, R

    1994-01-01

    Cytosolic calcium ([Ca2+]i) has been suggested as a key modulator in the regulation of active sodium transport across electrically "tight" (high resistance) epithelia. In this study we investigated the effects of calcium on cellular electrophysiological parameters in a classical model tissue, the......, the frog skin. [Ca2+]i was measured with fura-2 in an epifluorescence microscope setup. An inhibition of basolateral potassium permeability was observed when cytosolic calcium was increased. This inhibition was reversible upon removal of calcium from the serosal solution....

  5. Intracellular Calcium Plays a Critical Role in the Microcystin-LR-Elicited Neurotoxicity Through PLC/IP3 Pathway.

    Science.gov (United States)

    Cai, Fei; Liu, Jue; Li, Cairong; Wang, Jianghua

    2015-01-01

    Neurotoxicity of microcystin-leucine-arginine (MCLR) has been widely reported. However, the mechanism is not fully understood. Using primary hippocampal neurons, we tested the hypothesis that MCLR-triggered activation in intracellular free calcium concentration ([Ca(2+)](i)) induces the death of neurons. Microcystin-leucine-arginine inhibited cell viability at a range of 0.1 to 30 μmol/L and caused a dose-dependent increase in [Ca(2+)](i). This increase in [Ca(2+)](i) was observed in Ca(2+)-free media and blocked by an endoplasmic reticulum Ca(2+) pump inhibitor, suggesting intracellular Ca(2+) release. Moreover, pretreatment of hippocampal neurons with intracellular Ca(2+) chelator (O,O'-bis (2-aminophenyl) ethyleneglycol-N,N,N',N'-tetraacetic acid, tetraacetoxy-methyl ester) and inositol 1,4,5-trisphosphate receptor antagonist (2-aminoethoxydiphenyl borate) could block both the Ca(2+) mobilization and the neuronal death following MCLR exposure. In contrast, the ryanodine receptor inhibitor (dantrolene) did not ameliorate the effect of MCLR. In conclusion, MCLR disrupts [Ca(2+)](i) homeostasis in neurons by releasing Ca(2+) from intracellular stores, and this increase in [Ca(2+)](i) may be a key determinant in the mechanism underlying MCLR-induced neurotoxicity. © The Author(s) 2015.

  6. Up-regulation of Intracellular Calcium Handling Underlies the Recovery of Endotoxemic Cardiomyopathy in Mice.

    Science.gov (United States)

    Morse, Justin C; Huang, Joanne; Khona, Natasha; Miller, Edward J; Siwik, Deborah A; Colucci, Wilson S; Hobai, Ion A

    2017-06-01

    In surviving patients, sepsis-induced cardiomyopathy is spontaneously reversible. In the absence of any experimental data, it is generally thought that cardiac recovery in sepsis simply follows the remission of systemic inflammation. Here the authors aimed to identify the myocardial mechanisms underlying cardiac recovery in endotoxemic mice. Male C57BL/6 mice were challenged with lipopolysaccharide (7 μg/g, intraperitoneally) and followed for 12 days. The authors assessed survival, cardiac function by echocardiography, sarcomere shortening, and calcium transients (with fura-2-acetoxymethyl ester) in electrically paced cardiomyocytes (5 Hz, 37°C) and myocardial protein expression by immunoblotting. Left ventricular ejection fraction, cardiomyocyte sarcomere shortening, and calcium transients were depressed 12 h after lipopolysaccharide challenge, started to recover by 24 h (day 1), and were back to baseline at day 3. The recovery of calcium transients at day 3 was associated with the up-regulation of the sarcoplasmic reticulum calcium pump to 139 ± 19% (mean ± SD) of baseline and phospholamban down-regulation to 35 ± 20% of baseline. At day 6, calcium transients were increased to 123 ± 31% of baseline, associated with increased sarcoplasmic reticulum calcium load (to 126 ± 32% of baseline, as measured with caffeine) and inhibition of sodium/calcium exchange (to 48 ± 12% of baseline). In mice surviving lipopolysaccharide challenge, the natural recovery of cardiac contractility was associated with the up-regulation of cardiomyocyte calcium handling above baseline levels, indicating the presence of an active myocardial recovery process, which included sarcoplasmic reticulum calcium pump activation, the down-regulation of phospholamban, and sodium/calcium exchange inhibition.

  7. Silver ions increase plasma membrane permeability through modulation of intracellular calcium levels in tobacco BY-2 cells.

    Science.gov (United States)

    Klíma, Petr; Laňková, Martina; Vandenbussche, Filip; Van Der Straeten, Dominique; Petrášek, Jan

    2018-03-03

    Silver ions increase plasma membrane permeability for water and small organic compounds through their stimulatory effect on plasma membrane calcium channels, with subsequent modulation of intracellular calcium levels and ion homeostasis. The action of silver ions at the plant plasma membrane is largely connected with the inhibition of ethylene signalling thanks to the ability of silver ion to replace the copper cofactor in the ethylene receptor. A link coupling the action of silver ions and cellular auxin efflux has been suggested earlier by their possible direct interaction with auxin efflux carriers or by influencing plasma membrane permeability. Using tobacco BY-2 cells, we demonstrate here that besides a dramatic increase of efflux of synthetic auxins 2,4-dichlorophenoxyacetic acid (2,4-D) and 1-naphthalene acetic acid (NAA), treatment with AgNO 3 resulted in enhanced efflux of the cytokinin trans-zeatin (tZ) as well as the auxin structural analogues tryptophan (Trp) and benzoic acid (BA). The application of AgNO 3 was accompanied by gradual water loss and plasmolysis. The observed effects were dependent on the availability of extracellular calcium ions (Ca 2+ ) as shown by comparison of transport assays in Ca 2+ -rich and Ca 2+ -free buffers and upon treatment with inhibitors of plasma membrane Ca 2+ -permeable channels Al 3+ and ruthenium red, both abolishing the effect of AgNO 3 . Confocal microscopy of Ca 2+ -sensitive fluorescence indicator Fluo-4FF, acetoxymethyl (AM) ester suggested that the extracellular Ca 2+ availability is necessary to trigger the response to silver ions and that the intracellular Ca 2+ pool alone is not sufficient for this effect. Altogether, our data suggest that in plant cells the effects of silver ions originate from the primal modification of the internal calcium levels, possibly by their interaction with Ca 2+ -permeable channels at the plasma membrane.

  8. Activation of PKA and Epac proteins by cyclic AMP depletes intracellular calcium stores and reduces calcium availability for vasoconstriction.

    Science.gov (United States)

    Cuíñas, Andrea; García-Morales, Verónica; Viña, Dolores; Gil-Longo, José; Campos-Toimil, Manuel

    2016-06-15

    We investigated the implication of PKA and Epac proteins in the endothelium-independent vasorelaxant effects of cyclic AMP (cAMP). Cytosolic Ca(2+) concentration ([Ca(2+)]c) was measured by fura-2 imaging in rat aortic smooth muscle cells (RASMC). Contraction-relaxation experiments were performed in rat aortic rings deprived of endothelium. In extracellular Ca(2+)-free solution, cAMP-elevating agents induced an increase in [Ca(2+)]c in RASMC that was reproduced by PKA and Epac activation and reduced after depletion of intracellular Ca(2+) reservoirs. Arginine-vasopressin (AVP)-evoked increase of [Ca(2+)]c and store-operated Ca(2+) entry (SOCE) were inhibited by cAMP-elevating agents, PKA or Epac activation in these cells. In aortic rings, the contractions induced by phenylephrine in absence of extracellular Ca(2+) were inhibited by cAMP-elevating agents, PKA or Epac activation. In these conditions, reintroduction of Ca(2+) induced a contraction that was inhibited by cAMP-elevating agents, an effect reduced by PKA inhibition and reproduced by PKA or Epac activators. Our results suggest that increased cAMP depletes intracellular, thapsigargin-sensitive Ca(2+) stores through activation of PKA and Epac in RASMC, thus reducing the amount of Ca(2+) released by IP3-generating agonists during the contraction of rat aorta. cAMP rise also inhibits the contraction induced by depletion of intracellular Ca(2+), an effect mediated by reduction of SOCE after PKA or Epac activation. Both effects participate in the cAMP-induced endothelium-independent vasorelaxation. Copyright © 2016 Elsevier Inc. All rights reserved.

  9. The cannabinoid agonist WIN55,212-2 increases intracellular calcium via CB1 receptor coupling to Gq/11 G proteins.

    Science.gov (United States)

    Lauckner, Jane E; Hille, Bertil; Mackie, Ken

    2005-12-27

    Central nervous system responses to cannabis are primarily mediated by CB(1) receptors, which couple preferentially to G(i/o) G proteins. Here, we used calcium photometry to monitor the effect of CB(1) activation on intracellular calcium concentration. Perfusion with 5 microM CB(1) aminoalkylindole agonist, WIN55,212-2 (WIN), increased intracellular calcium by several hundred nanomolar in human embryonic kidney 293 cells stably expressing CB(1) and in cultured hippocampal neurons. The increase was blocked by coincubation with the CB(1) antagonist, SR141716A, and was absent in nontransfected human embryonic kidney 293 cells. The calcium rise was WIN-specific, being essentially absent in cells treated with other classes of cannabinoid agonists, including Delta(9)-tetrahydrocannabinol, HU-210, CP55,940, 2-arachidonoylglycerol, methanandamide, and cannabidiol. The increase in calcium elicited by WIN was independent of G(i/o), because it was present in pertussis toxin-treated cells. Indeed, pertussis toxin pretreatment enhanced the potency and efficacy of WIN to increase intracellular calcium. The calcium increases appeared to be mediated by G(q) G proteins and phospholipase C, because they were markedly attenuated in cells expressing dominant-negative G(q) or treated with the phospholipase C inhibitors U73122 and ET-18-OCH(3) and were accompanied by an increase in inositol phosphates. The calcium increase was blocked by the sarco/endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin, the inositol trisphosphate receptor inhibitor xestospongin D, and the ryanodine receptor inhibitors dantrolene and 1,1'-diheptyl-4,4'-bipyridinium dibromide, but not by removal of extracellular calcium, showing that WIN releases calcium from intracellular stores. In summary, these results suggest that WIN stabilizes CB(1) receptors in a conformation that enables G(q) signaling, thus shifting the G protein specificity of the receptor.

  10. Honey bee dopamine and octopamine receptors linked to intracellular calcium signaling have a close phylogenetic and pharmacological relationship.

    Directory of Open Access Journals (Sweden)

    Kyle T Beggs

    Full Text Available BACKGROUND: Three dopamine receptor genes have been identified that are highly conserved among arthropod species. One of these genes, referred to in honey bees as Amdop2, shows a close phylogenetic relationship to the a-adrenergic-like octopamine receptor family. In this study we examined in parallel the functional and pharmacological properties of AmDOP2 and the honey bee octopamine receptor, AmOA1. For comparison, pharmacological properties of the honey bee dopamine receptors AmDOP1 and AmDOP3, and the tyramine receptor AmTYR1, were also examined. METHODOLOGY/PRINCIPAL FINDINGS: Using HEK293 cells heterologously expressing honey bee biogenic amine receptors, we found that activation of AmDOP2 receptors, like AmOA1 receptors, initiates a rapid increase in intracellular calcium levels. We found no evidence of calcium signaling via AmDOP1, AmDOP3 or AmTYR1 receptors. AmDOP2- and AmOA1-mediated increases in intracellular calcium were inhibited by 10 µM edelfosine indicating a requirement for phospholipase C-β activity in this signaling pathway. Edelfosine treatment had no effect on AmDOP2- or AmOA1-mediated increases in intracellular cAMP. The synthetic compounds mianserin and epinastine, like cis-(Z-flupentixol and spiperone, were found to have significant antagonist activity on AmDOP2 receptors. All 4 compounds were effective antagonists also on AmOA1 receptors. Analysis of putative ligand binding sites offers a possible explanation for why epinastine acts as an antagonist at AmDOP2 receptors, but fails to block responses mediated via AmDOP1. CONCLUSIONS/SIGNIFICANCE: Our results indicate that AmDOP2, like AmOA1, is coupled not only to cAMP, but also to calcium-signalling and moreover, that the two signalling pathways are independent upstream of phospholipase C-β activity. The striking similarity between the pharmacological properties of these 2 receptors suggests an underlying conservation of structural properties related to receptor

  11. Acanthamoeba castellanii metabolites increase the intracellular calcium level and cause cytotoxicity in wish cells.

    Science.gov (United States)

    Mattana, A; Bennardini, F; Usai, S; Fiori, P L; Franconi, F; Cappuccinelli, P

    1997-08-01

    Previous studies have shown that trophozoites of the pathogenic free-living amoeba Acanthamoeba castellanii rapidly lyse a variety of cells in vitro. However, the role played by cytolitic molecules that may participate in Acanthamoebal cytopathogenicity has yet to be completely elucidated. The aim of this work was to study whether soluble molecules released by A. castellanii trophozoites could induce cytopathic effect in human epithelial cells in vitro. The results obtained indicate that A. castellanii trophozoites constitutively elaborate and release soluble factors that immediately elicit a cytosolic free-calcium increase in target cells. This phenomenon is induced by low molecular weight amoebic metabolites and depends on a transmembrane influx of extracellular calcium. Morphological changes, cytoskeletal damage, cell death and cytolysis followed the elevation of cytosolic free-calcium levels. Calcium ions are very important for cell homeostasis, in fact, they control the functions of a variety of cellular responses, including secretion, cell proliferation and apoptosis. Our results suggest that the substained elevation of the cytosolic free-calcium in response to A. castellanii metabolites might play a fundamental role in target cell damage during Acanthamoeba infections.

  12. An atmospheric-pressure cold plasma leads to apoptosis in Saccharomyces cerevisiae by accumulating intracellular reactive oxygen species and calcium

    Science.gov (United States)

    Ma, R. N.; Feng, H. Q.; Liang, Y. D.; Zhang, Q.; Tian, Y.; Su, B.; Zhang, J.; Fang, J.

    2013-07-01

    A non-thermal plasma is known to induce apoptosis of various cells but the mechanism is not yet clear. A eukaryotic model organism Saccharomyces cerevisiaewas used to investigate the cellular and biochemical regulations of cell apoptosis and cell cycle after an atmospheric-pressure cold plasma treatment. More importantly, intracellular calcium (Ca2+) was first involved in monitoring the process of plasma-induced apoptosis in this study. We analysed the cell apoptosis and cell cycle by flow cytometry and observed the changes in intracellular reactive oxygen species (ROS) and Ca2+ concentration, cell mitochondrial membrane potential (Δψm) as well as nuclear DNA morphology via fluorescence staining assay. All experimental results indicated that plasma-generated ROS leads to the accumulation of intracellular ROS and Ca2+ that ultimately contribute to apoptosis associated with cell cycle arrest at G1 phase through depolarization of Δψm and fragmenting nuclear DNA. This work provides a novel insight into the physical and biological mechanism of apoptosis induced by a plasma which could benefit for promoting the development of plasmas applied to cancer therapy.

  13. Effect of Cu2+ and pH on intracellular calcium content and lipid peroxidation in winter wheat roots

    Directory of Open Access Journals (Sweden)

    M. E. Riazanova

    2015-06-01

    Full Text Available The study investigates the effect of copper ions and pH of external solution on intracellular calcium homeostasis and lipid peroxidation in winter wheat roots. Experiment was carried out with winter wheat. Sterile seeds were germinated in Petri dishes on the filter paper soaked with acetic buffer (pH 4.7 and 6.2 at 20 °Cin the dark for 48 hours. Copper was added as CuSO4. It’s concentrations varied from 0 to 50 µM. The Ca2+-fluorescent dye Fluo-3/AM ester was loaded on 60 hour. Root fluorescence with Fluo-3 loading was detected using X-Cite Series 120 Q unit attached to microscope Olympus BX53 with camera Olympus DP72. Imaging of root cells was achieved after exciting with 488 nm laser and collection of emission signals above 512 nm. Preliminary analysis of the images was performed using software LabSens; brightness (fluorescence intensity analysis was carried out by means of ImageJ. Peroxidation of lipids was determined according to Kumar and Knowles method. It was found that pH of solution had effect on release of calcium from intracellular stores. Low pH provokes an increase of [Ca2+]cyt which may be reaction of roots to acidic medium. Copper induces increase in non-selective permeability of plasma membrane and leads to its faster depolarization. This probably initiates Ca-dependent depolarization channels which are responsible for the influx of calcium from apoplast into the cell. Changing of the membrane permeability may occur due to interaction between Cu2+ ions and Ca-binding sites on plasma membrane or may be due to binding of copper with sulfhydryl groups and increasing of POL. Copper may also damage lipid bilayer and change the activity of some non-selective channels and transporters. Reactive oxygen species which are formed under some types of stress factors, especially the effect of heavy metals, can be activators of Ca-channels. Cu2+ ions rise MDA content and promote the oxidative stress. Low medium pH also induces its

  14. The transduction channel TRPM5 is gated by intracellular calcium in taste cells.

    Science.gov (United States)

    Zhang, Zheng; Zhao, Zhen; Margolskee, Robert; Liman, Emily

    2007-05-23

    Bitter, sweet, and umami tastants are detected by G-protein-coupled receptors that signal through a common second-messenger cascade involving gustducin, phospholipase C beta2, and the transient receptor potential M5 (TRPM5) ion channel. The mechanism by which phosphoinositide signaling activates TRPM5 has been studied in heterologous cell types with contradictory results. To resolve this issue and understand the role of TRPM5 in taste signaling, we took advantage of mice in which the TRPM5 promoter drives expression of green fluorescent protein and mice that carry a targeted deletion of the TRPM5 gene to unequivocally identify TRPM5-dependent currents in taste receptor cells. Our results show that brief elevation of intracellular inositol trisphosphate or Ca2+ is sufficient to gate TRPM5-dependent currents in intact taste cells, but only intracellular Ca2+ is able to activate TRPM5-dependent currents in excised patches. Detailed study in excised patches showed that TRPM5 forms a nonselective cation channel that is half-activated by 8 microM Ca2+ and that desensitizes in response to prolonged exposure to intracellular Ca2+. In addition to channels encoded by the TRPM5 gene, we found that taste cells have a second type of Ca2+-activated nonselective cation channel that is less sensitive to intracellular Ca2+. These data constrain proposed models for taste transduction and suggest a link between receptor signaling and membrane potential in taste cells.

  15. Parvalbumin overexpression alters immune-mediated increases in intracellular calcium, and delays disease onset in a transgenic model of familial amyotrophic lateral sclerosis

    Science.gov (United States)

    Beers, D. R.; Ho, B. K.; Siklos, L.; Alexianu, M. E.; Mosier, D. R.; Mohamed, A. H.; Otsuka, Y.; Kozovska, M. E.; McAlhany, R. E.; Smith, R. G.; hide

    2001-01-01

    Intracellular calcium is increased in vulnerable spinal motoneurons in immune-mediated as well as transgenic models of amyotrophic lateral sclerosis (ALS). To determine whether intracellular calcium levels are influenced by the calcium-binding protein parvalbumin, we developed transgenic mice overexpressing parvalbumin in spinal motoneurons. ALS immunoglobulins increased intracellular calcium and spontaneous transmitter release at motoneuron terminals in control animals, but not in parvalbumin overexpressing transgenic mice. Parvalbumin transgenic mice interbred with mutant SOD1 (mSOD1) transgenic mice, an animal model of familial ALS, had significantly reduced motoneuron loss, and had delayed disease onset (17%) and prolonged survival (11%) when compared with mice with only the mSOD1 transgene. These results affirm the importance of the calcium binding protein parvalbumin in altering calcium homeostasis in motoneurons. The increased motoneuron parvalbumin can significantly attenuate the immune-mediated increases in calcium and to a lesser extent compensate for the mSOD1-mediated 'toxic-gain-of-function' in transgenic mice.

  16. Activation of Intracellular Calcium by Multiple Wnt Ligands and Translocation of β-Catenin into the Nucleus

    Science.gov (United States)

    Thrasivoulou, Christopher; Millar, Michael; Ahmed, Aamir

    2013-01-01

    Ca2+ and β-catenin, a 92-kDa negatively charged transcription factor, transduce Wnt signaling via the non-canonical, Wnt/Ca2+ and canonical, Wnt/β-catenin pathways independently. The nuclear envelope is a barrier to large protein entry, and this process is regulated by intracellular calcium [Ca2+]i and trans-nuclear potential. How β-catenin traverses the nuclear envelope is not well known. We hypothesized that Wnt/Ca2+ and Wnt/β-catenin pathways act in a coordinated manner and that [Ca2+]i release facilitates β-catenin entry into the nucleus in mammalian cells. In a live assay using calcium dyes in PC3 prostate cancer cells, six Wnt peptides (3A, 4, 5A, 7A, 9B, and 10B) mobilized [Ca2+]i but Wnt11 did not. Based upon dwell time (range = 15–30 s) of the calcium waveform, these Wnts could be classified into three classes: short, 3A and 5A; long, 7A and 10B; and very long, 4 and 9B. Wnt-activated [Ca2+]i release was followed by an increase in intranuclear calcium and the depolarization of both the cell and nuclear membranes, determined by using FM4-64. In cells treated with Wnts 5A, 9B, and 10B, paradigm substrates for each Wnt class, increased [Ca2+]i was followed by β-catenin translocation into the nucleus in PC3, MCF7, and 253J, prostate, breast, and bladder cancer cell lines; both the increase in Wnt 5A, 9B, and 10B induced [Ca2+]i release and β-catenin translocation are suppressed by thapsigargin in PC3 cell line. We propose a convergent model of Wnt signaling network where Ca2+ and β-catenin pathways may act in a coordinated, interdependent, rather than independent, manner. PMID:24158438

  17. Enhanced NMDA receptor-mediated intracellular calcium signaling in magnocellular neurosecretory neurons in heart failure rats.

    Science.gov (United States)

    Stern, Javier E; Potapenko, Evgeniy S

    2013-08-15

    An enhanced glutamate excitatory function within the hypothalamic supraoptic and paraventricluar nuclei is known to contribute to increased neurosecretory and presympathetic neuronal activity, and hence, neurohumoral activation, during heart failure (HF). Still, the precise mechanisms underlying enhanced glutamate-driven neuronal activity in HF remain to be elucidated. Here, we performed simultaneous electrophysiology and fast confocal Ca²⁺ imaging to determine whether altered N-methyl-d-aspartate (NMDA) receptor-mediated changes in intracellular Ca²⁺ levels (NMDA-ΔCa²⁺) occurred in hypothalamic magnocellular neurosecretory cells (MNCs) in HF rats. We found that activation of NMDA receptors resulted in a larger ΔCa²⁺ in MNCs from HF when compared with sham rats. The enhanced NMDA-ΔCa²⁺ was neither dependent on the magnitude of the NMDA-mediated current (voltage clamp) nor on the degree of membrane depolarization or firing activity evoked by NMDA (current clamp). Differently from NMDA receptor activation, firing activity evoked by direct membrane depolarization resulted in similar changes in intracellular Ca²⁺ in sham and HF rats. Taken together, our results support a relatively selective alteration of intracellular Ca²⁺ homeostasis and signaling following activation of NMDA receptors in MNCs during HF. The downstream functional consequences of such altered ΔCa²⁺ signaling during HF are discussed.

  18. Dystrophin gene expression and intracellular calcium changes in the giant freshwater prawn, Macrobrachium rosenbergii, in response to white spot symptom disease infection

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    Anees Fathima Noor

    2017-12-01

    Discussion: Both the functionality of the dystrophin protein and the intracellular calcium concentration were affected by WSSV infection which resulted in progressive muscle degeneration. An increased understanding of the role of dystrophin-calcium in MrDys and the interactions between these two components is necessary to prevent or reduce occurrences of muscle degeneration caused by WSSV infection, thereby reducing economic losses in the prawn farming industry from such disease.

  19. Influence of dietary cholesterol on 26-hydroxycholesterol and the effect of 26-hydroxycholesterol on the intracellular free calcium level

    International Nuclear Information System (INIS)

    Kou, I.L.

    1987-01-01

    The purpose of this study was to investigate the factors influencing serum level of 26-hydroxycholesterol after long-term consumption of cholesterol by animals. It is also to examine the effect of this sterol on intracellular free calcium level. Purified 26-hydroxycholesterol was synthesized from kryptogenin by the Clemmemsen and Wolff-Kishner reduction method. 26-Hydroxycholesterol was also used for fatty acid esters syntheses, and to study its influence on membranes. Tritiated 26-hydroxycholesterol which was synthesized by an enzymatic method, was used to monitor the 26-hydroxycholesterol loss during the procedure. The ester form of 26-hydroxycholesterol was also synthesized, and used to investigate its effects on membranes. The HPLC method that was developed for the analysis of 26-hydroxycholesterol levels in animal tissues was accurate, efficient, and reproducible for the determination of 26-hydroxycholesterol in plasma. However, it was not suitable for the analysis of other tissues, due to the overlapping of peaks making quantitation difficult

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

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    Zhenghang Zhao

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

  1. Inhibitory effect of donepezil on bradykinin-induced increase in the intracellular calcium concentration in cultured cortical astrocytes.

    Science.gov (United States)

    Makitani, Kouki; Nakagawa, Shota; Izumi, Yasuhiko; Akaike, Akinori; Kume, Toshiaki

    2017-05-01

    Donepezil is a potent and selective acetylcholinesterase inhibitor developed for the treatment of Alzheimer's disease. In the present study, we investigated the responses of astrocytes to bradykinin, an inflammatory mediator, and the effect of donepezil on these responses using cultured cortical astrocytes. Bradykinin induced a transient increase of intracellular calcium concentration ([Ca 2+ ] i ) in cultured astrocytes. Bradykinin-induced [Ca 2+ ] i increase was inhibited by the exposure to thapsigargin, which depletes Ca 2+ stores on endoplasmic reticulum, but not by the exclusion of extracellular Ca 2+ . Twenty four hours pretreatment of donepezil reduced the bradykinin-induced [Ca 2+ ] i increase. This reduction was inhibited not only by mecamylamine, a nAChR antagonist, but also by PI3K and Akt inhibitors. In addition, donepezil inhibited bradykinin-induced increase of the intracellular reactive oxygen species level in astrocytes. These results suggest that donepezil inhibits the inflammatory response induced by bradykinin via nAChR and PI3K-Akt pathway in astrocytes. Copyright © 2017 The Authors. Production and hosting by Elsevier B.V. All rights reserved.

  2. Inhibitory effect of donepezil on bradykinin-induced increase in the intracellular calcium concentration in cultured cortical astrocytes

    Directory of Open Access Journals (Sweden)

    Kouki Makitani

    2017-05-01

    Full Text Available Donepezil is a potent and selective acetylcholinesterase inhibitor developed for the treatment of Alzheimer's disease. In the present study, we investigated the responses of astrocytes to bradykinin, an inflammatory mediator, and the effect of donepezil on these responses using cultured cortical astrocytes. Bradykinin induced a transient increase of intracellular calcium concentration ([Ca2+]i in cultured astrocytes. Bradykinin-induced [Ca2+]i increase was inhibited by the exposure to thapsigargin, which depletes Ca2+ stores on endoplasmic reticulum, but not by the exclusion of extracellular Ca2+. Twenty four hours pretreatment of donepezil reduced the bradykinin-induced [Ca2+]i increase. This reduction was inhibited not only by mecamylamine, a nAChR antagonist, but also by PI3K and Akt inhibitors. In addition, donepezil inhibited bradykinin-induced increase of the intracellular reactive oxygen species level in astrocytes. These results suggest that donepezil inhibits the inflammatory response induced by bradykinin via nAChR and PI3K-Akt pathway in astrocytes.

  3. Differential intracellular calcium influx, nitric oxide production, ICAM-1 and IL8 expression in primary bovine endothelial cells exposed to nonesterified fatty acids.

    Science.gov (United States)

    Loaiza, Anitsi; Carretta, María D; Taubert, Anja; Hermosilla, Carlos; Hidalgo, María A; Burgos, Rafael A

    2016-02-25

    Nonesterified fatty acids (NEFAs) are involved in proinflammatory processes in cattle, including in the increased expression of adhesion molecules in endothelial cells. However, the mechanisms underlying these effects are still unknown. The aim of this study was to assess the effects of NEFAs on the intracellular calcium (Ca(2+) i) influx, nitric oxide production, and ICAM-1 and IL-8 expression in primary bovine umbilical vein endothelial cells (BUVECs). Myristic (MA), palmitic (PA), stearic (SA), oleic (OA) and linoleic acid (LA) rapidly increased Ca(2+) i. The calcium response to all tested NEFAs showed an extracellular calcium dependence and only the LA response was significantly inhibited until the intracellular calcium was chelated. The EC50 values for MA and LA were 125 μM and 37 μM, respectively, and the MA and LA effects were dependent on calcium release from the endoplasmic reticulum stores and on the L-type calcium channels. Only the calcium response to MA was significantly reduced by GW1100, a selective G-protein-coupled free fatty acid receptor (GPR40) antagonist. We also detected a functional FFAR1/GPR40 protein in BUVECs by using western blotting and the FFAR1/GPR40 agonist TAK-875. Only LA increased the cellular nitric oxide levels in a calcium-dependent manner. LA stimulation but not MA stimulation increased ICAM-1 and IL-8-expression in BUVECs. This effect was inhibited by GW1100, an antagonist of FFAR1/GPR40, but not by U-73122, a phospholipase C inhibitor. These findings strongly suggest that each individual NEFA stimulates endothelial cells in a different way, with clearly different effects on intracellular calcium mobilization, NO production, and IL-8 and ICAM-1 expression in primary BUVECs. These findings not only extend our understanding of NEFA-mediated diseases in ruminants, but also provide new insight into the different molecular mechanisms involved during endothelial cell activation by NEFAs.

  4. Modulation of L-type calcium current by intracellular magnesium in differentiating cardiomyocytes derived from induced pluripotent stem cells.

    Science.gov (United States)

    Nguemo, Filomain; Semmler, Judith; Reppel, Michael; Hescheler, Jürgen

    2014-06-15

    Intracellular Mg(2+), which is implicated in arrhythmogenesis and transient cardiac ischemia, inhibits L-type Ca(2+) calcium channel current (ICaL) of adult cardiomyocytes (CMs). We take the advantage of an in vitro model of CMs based on induced pluripotent stem cells to investigate the effects of intracellular Mg(2+) on the phosphorylation or dephosphorylation processes of L-type Ca(2+) channels (LTCCs) at early and late stages of cardiac cell differentiation. Using the whole-cell patch-clamp technique, we demonstrate that increasing intracellular Mg(2+) concentration [Mg(2+)]i from 0.2 to 5 mM markedly reduced the peak of ICaL density, showing less effect on both the activation and inactivation properties in the late differentiation stage (LDS) of CMs more so than in the early differentiation stage (EDS). Increasing the [Mg(2+)]i from 0.2 to 2 mM in the presence of cAMP-dependent protein kinase A significantly decreased ICaL in LDS (70%) and in EDS (36%) CMs. In addition, the effect of forskolin was greatly attenuated in the presence of 2 mM [Mg(2+)]i in LDS but not in EDS CMs. The effect of forskolin was enhanced in the presence of ATP-γ-S in LDS CMs compared with EDS CMs. The exposure of both EDS and LDS CMs to 2 mM [Mg(2+)]i considerably reduced the effects of isobutylmethylxanthine (IBMX) and okadaic acid on ICaL. Our results provide evidence for differential regulation of LTCCs activities by cytosolic Mg(2+) concentration in developing cardiac cells and confirm that Mg(2+) acts under conditions that favor opening of the LTCCs caused by channel phosphorylation.

  5. Intracellular calcium levels determine differential modulation of allosteric interactions within G protein-coupled receptor heteromers.

    Science.gov (United States)

    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.

  6. Ciliary neurotrophic factor-treated astrocyte-conditioned medium increases the intracellular free calcium concentration in rat cortical neurons.

    Science.gov (United States)

    Sun, Meiqun; Liu, Hongli; Min, Shengping; Wang, Hongtao; Wang, Xiaojing

    2016-04-01

    Ciliary neurotrophic factor (CNTF) is involved in the activation of astrocytes. A previous study showed that CNTF-treated astrocyte-conditioned medium (CNTF-ACM) contributed to the increase of the calcium current and the elevation of corresponding ion channels in cortical neurons. On this basis, it is reasonable to assume that CNTF-ACM may increase the intracellular free calcium concentration ([Ca 2+ ] i ) in neurons. In the present study, the effects of CNTF-ACM on [Ca 2+ ] i in rat cortical neurons were determined, and on this basis, the aim was to investigate the potential active ingredients in ACM that are responsible for this biological process. As expected, the data indicated that CNTF-ACM resulted in a clear elevation of [Ca 2+ ] i in neurons. Additionally, the fibroblast growth factor-2 (FGF-2) contained in the CNTF-ACM was found to participate in the upregulation of [Ca 2+ ] i . Taken together, CNTF induces the production of active factors (at least including FGF-2) released from astrocytes, which finally potentiate the increase of [Ca 2+ ] i in cortical neurons.

  7. Developmental Axon Stretch Stimulates Neuron Growth While Maintaining Normal Electrical Activity, Intracellular Calcium Flux, and Somatic Morphology

    Directory of Open Access Journals (Sweden)

    Joseph R Loverde

    2015-08-01

    Full Text Available Elongation of nerve fibers intuitively occurs throughout mammalian development, and is synchronized with expansion of the growing body. While most tissue systems enlarge through mitosis and differentiation, elongation of nerve fibers is remarkably unique. The emerging paradigm suggests that axons undergo stretch as contiguous tissues enlarge between the proximal and distal segments of spanning nerve fibers. While stretch is distinct from growth, tension is a known stimulus which regulates the growth of axons. Here, we hypothesized that the axon stretch-growth process may be a natural form of injury, whereby regenerative processes fortify elongating axons in order to prevent disconnection. Harnessing the live imaging capability of our axon stretch-growth bioreactors, we assessed neurons both during and following stretch for biomarkers associated with injury. Utilizing whole-cell patch clamp recording, we found no evidence of changes in spontaneous action potential activity or degradation of elicited action potentials during real-time axon stretch at strains of up to 18 % applied over 5 minutes. Unlike traumatic axonal injury, functional calcium imaging of the soma revealed no shifts in free intracellular calcium during axon stretch. Finally, the cross-sectional areas of nuclei and cytoplasms were normal, with no evidence of chromatolysis following week-long stretch-growth limited to the lower of 25 % strain or 3 mm total daily stretch. The neuronal growth cascade coupled to stretch was concluded to be independent of the changes in membrane potential, action potential generation, or calcium flux associated with traumatic injury. While axon stretch-growth is likely to share overlap with regenerative processes, we conclude that developmental stretch is a distinct stimulus from traumatic axon injury.

  8. Developmental axon stretch stimulates neuron growth while maintaining normal electrical activity, intracellular calcium flux, and somatic morphology.

    Science.gov (United States)

    Loverde, Joseph R; Pfister, Bryan J

    2015-01-01

    Elongation of nerve fibers intuitively occurs throughout mammalian development, and is synchronized with expansion of the growing body. While most tissue systems enlarge through mitosis and differentiation, elongation of nerve fibers is remarkably unique. The emerging paradigm suggests that axons undergo stretch as contiguous tissues enlarge between the proximal and distal segments of spanning nerve fibers. While stretch is distinct from growth, tension is a known stimulus which regulates the growth of axons. Here, we hypothesized that the axon stretch-growth process may be a natural form of injury, whereby regenerative processes fortify elongating axons in order to prevent disconnection. Harnessing the live imaging capability of our axon stretch-growth bioreactors, we assessed neurons both during and following stretch for biomarkers associated with injury. Utilizing whole-cell patch clamp recording, we found no evidence of changes in spontaneous action potential activity or degradation of elicited action potentials during real-time axon stretch at strains of up to 18% applied over 5 min. Unlike traumatic axonal injury, functional calcium imaging of the soma revealed no shifts in free intracellular calcium during axon stretch. Finally, the cross-sectional areas of nuclei and cytoplasms were normal, with no evidence of chromatolysis following week-long stretch-growth limited to the lower of 25% strain or 3 mm total daily stretch. The neuronal growth cascade coupled to stretch was concluded to be independent of the changes in membrane potential, action potential generation, or calcium flux associated with traumatic injury. While axon stretch-growth is likely to share overlap with regenerative processes, we conclude that developmental stretch is a distinct stimulus from traumatic axon injury.

  9. The effect and mechanism of endothelin-1-induced intracellular free calcium in human lung adenocarcinoma cells SPC-A1

    Directory of Open Access Journals (Sweden)

    Juan ZHOU

    2008-08-01

    Full Text Available Background and objective Endothelin-1 (ET-1 is a potent mitogen involved in cell growth in human lung adenocarcinoma cells SPC-A1. The increase in intracellular free calcium ([Ca2+]i plays a great role in this process. The aim of this study is to investigate the ET-1-induced [Ca2+]i responses in SPC-A1 cells and to explore its cellular mechanism. Methods [Ca2+]i was measured by Fura-2/AM fluorescent assay. Endothelin receptors antagonists, calcium channel blockers and intracellular signal transduction blockers were used to study the underlying mechanism of ET-1-induced [Ca2+]i responses in SPC-A1 cells. Results At the concentration of 1×10-15 mol/L-1×10-8 mol/L, ET-1 caused a dose-dependent increase of [Ca2+]i in SPC-A1 cells (P0.05, a highly selective endothelin receptor B (ETBR antagonist. Depletion of extracellular Ca2+ with free Ca2+ solution and 0.1mmol/L ethyleneglycol bis (2-aminoethyl ether tetraacetic acid (EGTA or blockade of voltage dependent calcium channel with nifedipine at 1×10-6 mol/L significantly reduced the ET-1-induced increase of [Ca2+]i. The ET-1-induced (1×10-10 mol/L increase of [Ca2+]i was also significantly attenuated by U73122 at 1×10-5 mol/L (P<0.05, a phospholipase C inhibitor, and by Ryanodine at 50×10-6 mol/L. However, Staurosporine (2×10-9 mol/L, a protein kinas C inhibitor, exerted no significant effect on the ET-1-induced (1×10-10 mol/L increase of [Ca2+]i. Conclusion ET-1 elevates [Ca2+]i via activation of ETA receptor. Both phospholipase C/Ca2+ pathway and Ca2+ influx through voltage dependent Ca2+ channel activate by ETAR contribute to this process.

  10. ERK1/2 mediates sperm acrosome reaction through elevation of intracellular calcium concentration.

    Science.gov (United States)

    Jaldety, Yael; Breitbart, Haim

    2015-10-01

    Mammalian sperm acquire fertilization capacity after residing in the female reproductive tract for a few hours in a process called capacitation. Only capacitated sperm can bind the zona pellucida (ZP) of the egg and undergo the acrosome reaction, a process that allows penetration and fertilization. Extracellular signal regulated kinase (ERK1/2) mediates signalling in many cell types, however its role in sperm function is largely unknown. Here we show that ERK1/2 is highly phosphorylated/activated after a short incubation of mouse sperm under capacitation conditions and that this phosphorylation is reduced after longer incubation. Further phosphorylation was observed upon addition of crude extract of egg ZP or epidermal growth factor (EGF). The mitogen-activated ERK-kinase (MEK) inhibitor U0126 abolished ERK1/2 phosphorylation, in vitro fertilization rate and the acrosome reaction induced by ZP or EGF but not by the Ca2+-ionophore A23187. Moreover, inhibition of ERK1/2 along the capacitation process diminished almost completely the sperm's ability to go through the acrosome reaction, while inhibition at the end of capacitation attenuated the acrosome reaction rate by only 45%. The fact that the acrosome reaction, induced by the Ca2+ -ionophore A23187, was not inhibited by U0126 suggests that ERK1/2 mediates the acrosome reaction by activating Ca2+ transport into the cell. Direct determination of intracellular [Ca2+] revealed that Ca2+ influx induced by EGF or ZP was completely blocked by U0126. Thus, it has been established that the increase in ERK1/2 phosphorylation/activation in response to ZP or by activation of the EGF receptor (EGFR) by EGF, is a key event for intracellular Ca2+ elevation and the subsequent occurrence of the acrosome reaction.

  11. Anabolic Androgenic Steroids and Intracellular Calcium Signaling: A Mini Review on Mechanisms and Physiological Implications

    Science.gov (United States)

    Vicencio, J.M.; Estrada, M.; Galvis, D.; Bravo, R.; Contreras, A.E.; Rotter, D.; Szabadkai, G.; Hill, J.A.; Rothermel, B.A.; Jaimovich, E.; Lavandero, S.

    2015-01-01

    Increasing evidence suggests that nongenomic effects of testosterone and anabolic androgenic steroids (AAS) operate concertedly with genomic effects. Classically, these responses have been viewed as separate and independent processes, primarily because nongenomic responses are faster and appear to be mediated by membrane androgen receptors, whereas long-term genomic effects are mediated through cytosolic androgen receptors regulating transcriptional activity. Numerous studies have demonstrated increases in intracellular Ca2+ in response to AAS. These Ca2+ mediated responses have been seen in a diversity of cell types, including osteoblasts, platelets, skeletal muscle cells, cardiac myocytes and neurons. The versatility of Ca2+ as a second messenger provides these responses with a vast number of pathophysiological implications. In cardiac cells, testosterone elicits voltage-dependent Ca2+ oscillations and IP3R-mediated Ca2+ release from internal stores, leading to activation of MAPK and mTOR signaling that promotes cardiac hypertrophy. In neurons, depending upon concentration, testosterone can provoke either physiological Ca2+ oscillations, essential for synaptic plasticity, or sustained, pathological Ca2+ transients that lead to neuronal apoptosis. We propose therefore, that Ca2+ acts as an important point of crosstalk between nongenomic and genomic AAS signaling, representing a central regulator that bridges these previously thought to be divergent responses. PMID:21443511

  12. Use of multiple singular value decompositions to analyze complex intracellular calcium ion signals

    KAUST Repository

    Martinez, Josue G.

    2009-12-01

    We compare calcium ion signaling (Ca(2+)) between two exposures; the data are present as movies, or, more prosaically, time series of images. This paper describes novel uses of singular value decompositions (SVD) and weighted versions of them (WSVD) to extract the signals from such movies, in a way that is semi-automatic and tuned closely to the actual data and their many complexities. These complexities include the following. First, the images themselves are of no interest: all interest focuses on the behavior of individual cells across time, and thus, the cells need to be segmented in an automated manner. Second, the cells themselves have 100+ pixels, so that they form 100+ curves measured over time, so that data compression is required to extract the features of these curves. Third, some of the pixels in some of the cells are subject to image saturation due to bit depth limits, and this saturation needs to be accounted for if one is to normalize the images in a reasonably un-biased manner. Finally, the Ca(2+) signals have oscillations or waves that vary with time and these signals need to be extracted. Thus, our aim is to show how to use multiple weighted and standard singular value decompositions to detect, extract and clarify the Ca(2+) signals. Our signal extraction methods then lead to simple although finely focused statistical methods to compare Ca(2+) signals across experimental conditions.

  13. Correlation between oxidative stress and alteration of intracellular calcium handling in isoproterenol-induced myocardial infarction.

    Science.gov (United States)

    Díaz-Muñoz, Mauricio; Alvarez-Pérez, Marco Antonio; Yáñez, Lucía; Vidrio, Susana; Martínez, Lidia; Rosas, Gisele; Yáñez, Mario; Ramírez, Sotero; de Sánchez, Victoria Chagoya

    2006-09-01

    Myocardial Ca(2+) overload and oxidative stress are well documented effects associated to isoproterenol (ISO)-induced myocardial necrosis, but information correlating these two issues is scarce. Using an ISO-induced myocardial infarction model, 3 stages of myocardial damage were defined: pre-infarction (0-12 h), infarction (12-24 h) and post-infarction (24-96 h). Alterations in Ca(2+) homeostasis and oxidative stress were studied in mitochondria, sarcoplasmic reticulum and plasmalemma by measuring the Ca(2+) content, the activity of Ca(2+) handling proteins, and by quantifying TBARs, nitric oxide (NO) and oxidative protein damage (changes in carbonyl and thiol groups). Free radicals generated system, antioxidant enzymes and oxidative stress (GSH/GSSG ratio) were also monitored at different times of ISO-induced cardiotoxicity. The Ca(2+) overload induced by ISO was counterbalanced by a diminution in the ryanodine receptor activity and the Na(+)-Ca(+2) exchanger as well as by the increase in both calcium ATPases activities (vanadate- and thapsigargine-sensitive) and mitochondrial Ca(2+) uptake during pre-infarction and infarction stages. Pro-oxidative reactions and antioxidant defences during the 3 stages of cardiotoxicity were observed, with maximal oxidative stress during the infarction. Significant correlations were found among pro-oxidative reactions with plasmalemma and sarcoplasmic reticulum Ca(2+) ATPases, and ryanodine receptor activities at the onset and development of ISO-induced infarction. These findings could be helpful in the design of antioxidant therapies in this pathology.

  14. Selective effect of hydroxyapatite nanoparticles on osteoporotic and healthy bone formation correlates with intracellular calcium homeostasis regulation.

    Science.gov (United States)

    Zhao, Rui; Xie, Pengfei; Zhang, Kun; Tang, Zhurong; Chen, Xuening; Zhu, Xiangdong; Fan, Yujiang; Yang, Xiao; Zhang, Xingdong

    2017-09-01

    Adequate bone substitutes osseointegration has been difficult to achieve in osteoporosis. Hydroxyapatite of the osteoporotic bone, secreted by pathologic osteoblasts, had a smaller crystal size and lower crystallinity than that of the normal. To date, little is known regarding the interaction of synthetic hydroxyapatite nanoparticles (HANPs) with osteoblasts born in bone rarefaction. The present study investigated the biological effects of HANPs on osteoblastic cells derived from osteoporotic rat bone (OVX-OB), in comparison with the healthy ones (SHM-OB). A selective effect of different concentrations of HANPs on the two cell lines was observed that the osteoporotic osteoblasts had a higher tolerance. Reductions in cell proliferation, ALP activity, collagen secretion and osteoblastic gene expressions were found in the SHM-OB when administered with HANPs concentration higher than 25µg/ml. In contrast, those of the OVX-OB suffered no depression but benefited from 25 to 250µg/ml HANPs in a dose-dependent manner. We demonstrated that the different effects of HANPs on osteoblasts were associated with the intracellular calcium influx into the endoplasmic reticulum. The in vivo bone defect model further confirmed that, with a critical HANPs concentration administration, the osteoporotic rats had more and mechanically matured new bone formation than the non-treated ones, whilst the sham rats healed no better than the natural healing control. Collectively, the observed epigenetic regulation of osteoblastic cell function by HANPs has significant implication on defining design parameters for a potential therapeutic use of nanomaterials. In this study, we investigated the biological effects of hydroxyapatite nanoparticles (HANPs) on osteoporotic rat bone and the derived osteoblast. Our findings revealed a previously unrecognized phenomenon that the osteoporotic individuals could benefit from higher concentrations of HANPs, as compared with the healthy individuals. The in

  15. A method for decoding the neurophysiological spike-response transform.

    Science.gov (United States)

    Stern, Estee; García-Crescioni, Keyla; Miller, Mark W; Peskin, Charles S; Brezina, Vladimir

    2009-11-15

    Many physiological responses elicited by neuronal spikes-intracellular calcium transients, synaptic potentials, muscle contractions-are built up of discrete, elementary responses to each spike. However, the spikes occur in trains of arbitrary temporal complexity, and each elementary response not only sums with previous ones, but can itself be modified by the previous history of the activity. A basic goal in system identification is to characterize the spike-response transform in terms of a small number of functions-the elementary response kernel and additional kernels or functions that describe the dependence on previous history-that will predict the response to any arbitrary spike train. Here we do this by developing further and generalizing the "synaptic decoding" approach of Sen et al. (1996). Given the spike times in a train and the observed overall response, we use least-squares minimization to construct the best estimated response and at the same time best estimates of the elementary response kernel and the other functions that characterize the spike-response transform. We avoid the need for any specific initial assumptions about these functions by using techniques of mathematical analysis and linear algebra that allow us to solve simultaneously for all of the numerical function values treated as independent parameters. The functions are such that they may be interpreted mechanistically. We examine the performance of the method as applied to synthetic data. We then use the method to decode real synaptic and muscle contraction transforms.

  16. Chronic ethanol exposure induces SK-N-SH cell apoptosis by increasing N-methyl-D-aspartic acid receptor expression and intracellular calcium.

    Science.gov (United States)

    Wang, Hongbo; Wang, Xiaolong; Li, Yan; Yu, Hao; Wang, Changliang; Feng, Chunmei; Xu, Guohui; Chen, Jiajun; You, Jiabin; Wang, Pengfei; Wu, Xu; Zhao, Rui; Zhang, Guohua

    2018-04-01

    It has been identified that chronic ethanol exposure damages the nervous system, particularly neurons. There is scientific evidence suggesting that neuronal loss caused by chronic ethanol exposure has an association with neuron apoptosis and intracellular calcium oscillation is one of the primary inducers of apoptosis. Therefore, the present study aimed to investigate the inductive effects of intracellular calcium oscillation on apoptosis in SK-N-SH human neuroblastoma cells and the protective effects of the N-methyl-D-aspartic acid receptor (NMDAR) antagonist, memantine, on SK-N-SH cell apoptosis caused by chronic ethanol exposure. SK-N-SH cells were treated with 100 mM ethanol and memantine (4 µM) for 2 days. Protein expression of NR1 was downregulated by RNA interference (RNAi). Apoptosis was detected by Annexin V/propidium iodide (PI) double-staining and flow cytometry and cell viability was detected using an MTS kit. Fluorescence dual wavelength spectrophotometry was used to determine the intracellular calcium concentration and the levels of NR1 and caspase-3 were detected using western blotting. NR1 mRNA levels were also detected using qPCR. It was found that chronic ethanol exposure reduced neuronal cell viability and caused apoptosis of SK-N-SH cells, and the extent of damage in SK-N-SH cells was associated with ethanol exposure concentration and time. In addition, chronic ethanol exposure increased the concentration of intracellular calcium in SK-N-SH cells by inducing the expression of NMDAR, resulting in apoptosis, and memantine treatment reduced ethanol-induced cell apoptosis. The results of the present study indicate that the application of memantine may provide a novel strategy for the treatment of alcoholic dementia.

  17. Japanese Cedar (Cryptomeria japonica) pollen allergen induces elevation of intracellular calcium in human keratinocytes and impairs epidermal barrier function of human skin ex vivo.

    Science.gov (United States)

    Kumamoto, Junichi; Tsutsumi, Moe; Goto, Makiko; Nagayama, Masaharu; Denda, Mitsuhiro

    2016-01-01

    Cry j1 is the major peptide allergen of Japanese cedar (Sugi), Cryptomeria japonica. Since some allergens disrupt epidermal permeability barrier homeostasis, we hypothesized that Cry j1 might have a similar effect. Intracellular calcium level in cultured human keratinocytes was measured with a ratiometric fluorescent probe, Fura-2 AM. Application of Cry j1 significantly increased the intracellular calcium level of keratinocytes, and this increase was inhibited by trypsin inhibitor or a protease-activated receptor 2 (PAR-2) antagonist. We found that Cry j1 itself did not show protease activity, but application of Cry j1 to cultured keratinocytes induced a rapid (within 30 s) and transient increase of protease activity in the medium. This transient increase was blocked by trypsin inhibitor or PAR-2 antagonist. The effect of Cry j1 on transepidermal water loss (TEWL) of cultured human skin was measured in the presence and absence of a trypsin inhibitor and PAR-2 antagonist. Cry j1 significantly impaired the barrier function of human skin ex vivo, and this action was blocked by co-application of trypsin inhibitor or PAR-2 antagonist. Our results suggested that interaction of Cry j1 with epidermal keratinocytes leads to the activation of PAR-2, which induces elevation of intracellular calcium and disruption of barrier function. Blocking the interaction of Cry j1 with epidermal keratinocytes might ameliorate allergic reaction and prevent disruption of epidermal permeability barrier homeostasis.

  18. [Mechanism of 17β-estrogen on intracellular free calcium regulation in smooth muscle cells at the endometrial-myometrial interface in uteri with adenomyosis].

    Science.gov (United States)

    Wang, Sha; Duan, Hua; Zhang, Ying; Wang, Liping; Zhang, Henghui; Li, Guoli

    2015-07-01

    To investigate the regulation mechanism of estrogen on the free calcium of smooth muscle cells at the endometrial-myometrial interface (EMI) in uteri with adenomyosis. From September 2011 to November 2012, 59 uterine myometrial specimens were obtained from 59 cases underwent hysterectomy, including 28 adenomyosis patients as adenomyosis (ADS) group and 31 patients with cervical intraepithelial neoplasia III as control group. EMI smooth muscle cells were cultured and loaded with calcium ion fluorescent probe fluo-4/AM. After treated with trisphosphate (IP3) receptor antagonist, blocker of sarcoplasmic reticulum calcium-adenosine triphosphate (ATP), depleted agent of the ryanodine receptor-operated Ca(2+), inhibitor of L-type calcium channel, inhibitor of Na(+)-Ca(2+) exchanger, the labeled cells were stimulated with estrogen. The changes of intracellular Ca(2+) fluorescence intensity were detected by laser scanning microscopy. The changes of intracellular Ca(2+) concentration was indicated by △F[Ca(2+)](i). (1) Under normal calcium conditions, after the stimulation of estrogen, intracellular Ca(2+) fluorescence intensity in ADS group and control group both increased than those without estrogen. The △F[Ca(2+)](i) in ADS group was 384 ± 26, and in the control group △F[Ca(2+)](i) was 235 ± 20. The △F[Ca(2+)](i) in ADS group was higher than that in the control (P calcium conditions, the △F[Ca(2+)](i) in ADS group was 207 ± 17, and in the control group △F[Ca(2+)](i) was 221 ± 19. The △F[Ca(2+)](i) in ADS group was almost the same with the increase in the control (P = 0.731). The △F[Ca(2+)](i) in ADS group was significantly decreased compared with the calcium condition (P calcium conditions (P = 0.060). (2) After treated with IP3 receptor antagonist, blocker of sarcoplasmic reticulum calcium-ATP, depleted agent of the ryanodine receptor-operated Ca(2+), the △F[Ca(2+)]i in both groups were significantly reduced (P calcium channel, the △F[Ca(2+)](i

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

    International Nuclear Information System (INIS)

    Liu, P.-S.; Chiung, Y.-M.; Kao, Y.-Y.

    2006-01-01

    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 2+ ] 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 2+ mobilization in human neuroblastoma SH-SY5Y cells. TDI was found to elevate [Ca 2+ ] c by releasing Ca 2+ from the intracellular stores and extracellular Ca 2+ influx. 500 μM TDI induced a net [Ca 2+ ] c increase of 112 ± 8 and 78 ± 6 nM in the presence and absence of extracellular Ca 2+ , respectively. In Ca 2+ -free buffer, TDI induced Ca 2+ release from internal stores to reduce their Ca 2+ content and this reduction was evidenced by a suppression occurring on the [Ca 2+ ] c rise induced by thapsigargin, ionomycin, and methacholine after TDI incubation. In the presence of extracellular Ca 2+ , simultaneous exposure to TDI and methacholine led a higher level of [Ca 2+ ] 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 2+ ] c homeostasis including releasing Ca 2+ from internal stores and inducing extracellular Ca 2+ influx. The interaction of this novel character and bronchial hyperreactivity need further investigation

  20. Impaired recovery of intracellular calcium and force after activation in isolated myometrial and subcutaneous resistance arteries from women with preeclampsia.

    Science.gov (United States)

    Wimalasundera, Ruwan C; Wijetunge, Sumangali; Thom, Simon M; Regan, Lesley; Hughes, Alun D

    2010-03-01

    Preeclampsia is a major cause of maternal and perinatal morbidity and mortality, but its cause is poorly understood. This study investigated whether there is an abnormality of intracellular calcium ([Ca2=]i) and tension during recovery from activation in isolated resistance arteries in preeclampsia and investigated the underlying mechanisms. Subcutaneous and myometrial resistance arteries from preeclamptic, normotensive pregnant and nonpregnant women were mounted on an isometric myograph and loaded with fura-2 to allow simultaneous measurement of force and [Ca2+]i. Arteries were activated by a high-potassium solution or noradrenaline, and the rate of decline in force and [Ca2+]i examined following washout. Basal tone and [Ca2+]i and rise in force and [Ca2+]i induced by high-potassium solution did not differ between groups but the rate of decline after washout was significantly slowed in both subcutaneous and myometrial arteries from preeclamptic women as compared with normotensive pregnant or nonpregnant women. The rate of decline in force after noradrenaline was also slowed in arteries from preeclamptic women. In subcutaneous resistance arteries from nonpregnant women, removal of the endothelium did not affect the rate of decline in force after high-potassium solution. However, inhibition of the plasma membrane Ca ATPase with carboxyeosin mimicked the findings seen in preeclampsia. In contrast, inhibition of the sarcoplasmic endoreticulum Ca ATPase with cyclopiazonic acid had no effect on the rate of decline in force or [Ca2+]i. The rate of relaxation and decline in [Ca2+]i in resistance arteries are impaired in preeclampsia. This may be mediated by decreased activity of plasma membrane Ca2+ ATPase and could be a mechanism contributing to elevated peripheral resistance and raised blood pressure in preeclampsia.

  1. Resveratrol inhibits the intracellular calcium increase and angiotensin/endothelin system activation induced by soluble uric acid in mesangial cells

    Directory of Open Access Journals (Sweden)

    G. Albertoni

    2015-01-01

    Full Text Available Resveratrol (Resv is natural polyphenol found in grapes. This study evaluated the protective effect of Resv against the effects of uric acid (UA in immortalized human mesangial cells (ihMCs. ihMCs were preincubated with Resv (12.5 µM for 1 h and treated with UA (10 mg/dL for 6 or 12 h. The intracellular calcium concentration [Ca2+]i was quantified by fluorescence using flow cytometry. Angiotensinogen (AGT and pre-pro endothelin-1 (ppET-1 mRNA were assayed by quantitative real-time RT-PCR. Angiotensin II (AII and endothelin-1 (ET-1 were assayed by ELISA. UA significantly increased [Ca2+]i. Pre-incubation with Resv significantly reduced the change in [Ca2+]i induced by UA. Incubation with UA for 6 or 12 h also increased AGT mRNA expression and AII protein synthesis. Resv blunted these increases in AGT mRNA expression and AII protein. Incubation with UA in the ihMCs increased ppET-1 expression and ET-1 protein synthesis at 6 and 12 h. When ihMCs were pre-incubated with Resv, UA had a significantly diminished effect on ppET-1 mRNA expression and ET-1 protein synthesis at 6 and 12 h, respectively. Our results suggested that UA triggers reactions including AII and ET-1 production in mesangial cells. The renin-angiotensin system may contribute to the pathogenesis of renal function and chronic kidney disease. Resv can minimize the impact of UA on AII, ET-1 and the increase of [Ca2+]i in mesangial cells, suggesting that, at least in part, Resv can prevent the effects of soluble UA in mesangial cells.

  2. Resveratrol inhibits the intracellular calcium increase and angiotensin/endothelin system activation induced by soluble uric acid in mesangial cells

    Energy Technology Data Exchange (ETDEWEB)

    Albertoni, G.; Schor, N. [Divisão de Nefrologia, Departamento de Medicina, Universidade Federal de São Paulo, São Paulo, SP (Brazil)

    2014-10-24

    Resveratrol (Resv) is natural polyphenol found in grapes. This study evaluated the protective effect of Resv against the effects of uric acid (UA) in immortalized human mesangial cells (ihMCs). ihMCs were preincubated with Resv (12.5 µM) for 1 h and treated with UA (10 mg/dL) for 6 or 12 h. The intracellular calcium concentration [Ca{sup 2+}]i was quantified by fluorescence using flow cytometry. Angiotensinogen (AGT) and pre-pro endothelin-1 (ppET-1) mRNA were assayed by quantitative real-time RT-PCR. Angiotensin II (AII) and endothelin-1 (ET-1) were assayed by ELISA. UA significantly increased [Ca{sup 2+}]i. Pre-incubation with Resv significantly reduced the change in [Ca{sup 2+}]i induced by UA. Incubation with UA for 6 or 12 h also increased AGT mRNA expression and AII protein synthesis. Resv blunted these increases in AGT mRNA expression and AII protein. Incubation with UA in the ihMCs increased ppET-1 expression and ET-1 protein synthesis at 6 and 12 h. When ihMCs were pre-incubated with Resv, UA had a significantly diminished effect on ppET-1 mRNA expression and ET-1 protein synthesis at 6 and 12 h, respectively. Our results suggested that UA triggers reactions including AII and ET-1 production in mesangial cells. The renin-angiotensin system may contribute to the pathogenesis of renal function and chronic kidney disease. Resv can minimize the impact of UA on AII, ET-1 and the increase of [Ca{sup 2+}]i in mesangial cells, suggesting that, at least in part, Resv can prevent the effects of soluble UA in mesangial cells.

  3. Taurine prevention of calcium paradox-related damage in cardiac muscle. Its regulatory action on intracellular cation contents.

    Science.gov (United States)

    Yamauchi-Takihara, K; Azuma, J; Kishimoto, S; Onishi, S; Sperelakis, N

    1988-07-01

    The present study was designed to investigate in chick heart whether oral pretreatment with taurine or taurine added directly to the perfusate has any effect upon calcium paradox-induced heart failure. In both protocols, taurine significantly reduced the mechanical dysfunction resulting from the calcium paradox. Taurine pretreatment partially inhibited the excess accumulation of calcium in the myocardium that occurs upon calcium repletion, and microscopy revealed almost normal structure. This protective effect of taurine was accompanied by (a) reduction of the gain of sodium content that occurs during calcium depletion, and (b) reduction of the late gain in calcium that occurs during calcium repletion. It is proposed that taurine plays a role in the regulation of calcium homeostasis and membrane stabilization.

  4. Evidence for a role of intracellular stored parathyroid hormone in producing hysteresis of the PTH-calcium relationship in normal humans

    DEFF Research Database (Denmark)

    Schwarz, Peter; Madsen, J C; Rasmussen, A Q

    1998-01-01

    OBJECTIVE: Despite the clear recognition that extracellular ionized calcium controls PTH secretion, there have been suggestions of hysteresis in the relationship between extracellular ionized calcium and PTH during recovery from induced hypo- and hypercalcaemia in vivo in humans. In this study, we...... examined the possibility that release of intracellular stored PTH during induced hypocalcaemia may explain hysteresis. VOLUNTEERS: Eleven volunteers, five women and six men, were recruited to participate in the study. DESIGN: A series of three protocols of repeated induction of hypocalcaemia or sequential...... induction of hypo- and hypercalcaemia. RESULTS: We observed in a total of 13 trials that a drastic lowering of blood ionized calcium by 0.20 mmol/l within 30 min elicited an immediate large, transient peak release of PTH amounting to 6-16 times the baseline concentration. However, following a steady...

  5. Dystrophin gene expression and intracellular calcium changes in the giant freshwater prawn,Macrobrachium rosenbergii, in response to white spot symptom disease infection.

    Science.gov (United States)

    Noor, Anees Fathima; Soo, Tze Chiew Christie; Ghani, Farhana Mohd; Goh, Zee Hong; Khoo, Li Teng; Bhassu, Subha

    2017-12-01

    Dystrophin, an essential protein functional in the maintenance of muscle structural integrity is known to be responsible for muscle deterioration during white spot syndrome virus (WSSV) infection among prawn species. Previous studies have shown the upregulation of dystrophin protein in Macrobrachium rosenbergii (the giant freshwater prawn) upon white spot syndrome virus (WSSV) infection. The literature has also suggested the important role of calcium ion alterations in causing such muscle diseases. Thus, the interest of this study lies within the linkage between dystrophin functioning, intracellular calcium and white spot syndrome virus (WSSV) infection condition. In this study, the dystrophin gene from M. rosenbergii (MrDys) was first characterised followed by the characterization of dystrophin gene from a closely related shrimp species, Penaeus monodon (PmDys). Dystrophin sequences from different phyla were then used for evolutionary comparison through BLAST analysis, conserved domain analysis and phylogenetic analysis. The changes in mRNA expression levels of dystrophin and the alteration of intracellular calcium concentrations in WSSV infected muscle cells were then studied. A 1246 base pair long dystrophin sequence was identified in the giant freshwater prawn, Macrobrachium rosenbergii ( MrDys ) followed by 1082 base pair long dystrophin sequence in P. monodon ( PmDys ). Four conserved domains were identified from the thirteen dystrophin sequences compared which were classified into 5 different phyla. From the phylogenetic analysis, aside from PmDys, the characterised MrDys was shown to be most similar to the invertebrate phylum of Nematoda. In addition, an initial down-regulation of dystrophin gene expression followed by eventual up-regulation, together with an increase in intracellular calcium concentration [Ca 2+ ] i were shown upon WSSV experimental infection. Both the functionality of the dystrophin protein and the intracellular calcium concentration were

  6. 17beta-estradiol rapidly mobilizes intracellular calcium from ryanodine-receptor-gated stores via a PKC-PKA-Erk-dependent pathway in the human eccrine sweat gland cell line NCL-SG3.

    LENUS (Irish Health Repository)

    Muchekehu, Ruth W

    2008-09-01

    We describe a novel rapid non-genomic effect of 17beta-estradiol (E2) on intracellular Ca2+ ([Ca2+]i) signalling in the eccrine sweat gland epithelial cell line NCL-SG3. E2 had no observable effect on basal [Ca2+]i, however exposure of cells to E2 in the presence of the microsomal Ca2+ ATPase pump inhibitor, thapsigargin, produced a secondary, sustained increase in [Ca2+]i compared to thapsigargin treatment alone, where cells responded with a transient single spike-like increase in [Ca2+]i. The E2-induced increase in [Ca2+]i was not dependent on the presence of extracellular calcium and was completely abolished by ryanodine (100 microM). The estrogen receptor antagonist ICI 182,780 (1 microM) prevented the E2-induced effects suggesting a role for the estrogen receptor in the release of [Ca2+]i from ryanodine-receptor-gated stores. The E2-induced effect on [Ca2+]i could also be prevented by the protein kinase C delta (PKCdelta)-specific inhibitor rottlerin (10 microM), the protein kinase A (PKA) inhibitor Rp-adenosine 3\\

  7. Developmental regulation of intracellular calcium by N-methyl-D-aspartate and noradrenaline in rat visual cortex.

    Science.gov (United States)

    Kobayashi, M; Imamura, K; Kaub, P A; Nakadate, K; Watanabe, Y

    1999-01-01

    The effects of N-methyl-D-aspartate and noradrenaline on intracellular Ca2+ concentration in slices of rat visual cortex were studied using a fluorescent indicator, Fura-2. Bath application of N-methyl-D-aspartate (1-100 microM) increased intracellular Ca2+ concentration in a dose-dependent manner, especially in layers II/III. Noradrenaline (1-100 microM) also increased intracellular Ca2+ concentration in a dose-dependent manner, especially in layers I and IV. However, the maximum increase in intracellular Ca2+ concentration after 100 microM noradrenaline application was less than half of that after 100 microM N-methyl-D-aspartate application in slices obtained from animals in the sensitive period. The effect of noradrenaline was most prominent in slices of the sensitive period, whereas the N-methyl-D-aspartate-induced intracellular Ca2+ concentration response decreased with age. Additive effects from application of both N-methyl-D-aspartate and noradrenaline on intracellular Ca2+ concentration were found only in the neonatal stage. Pharmacological experiments showed that alpha1-adrenergic receptors play a major role in the noradrenaline-induced intracellular Ca2+ concentration response, although both alpha2- and beta-adrenergic receptors were also partially involved. The release of Ca2+ from intracellular storage underlay the early phase of the noradrenaline-induced intracellular Ca2+ concentration response, while extracellular Ca2+ influxes contributed to the sustained phase. Experiments using a gliotoxin, fluorocitric acid, suggested that the function of glial cells is involved in the noradrenaline-induced increase of intracellular Ca2+ concentration. The larger intracellular Ca2+ concentration response to noradrenaline during the sensitive period may modulate the increase in intracellular Ca2+ concentration by N-methyl-D-aspartate to maintain a higher level of cortical plasticity during this period.

  8. Acetylcholine Attenuates Hydrogen Peroxide-Induced Intracellular Calcium Dyshomeostasis Through Both Muscarinic and Nicotinic Receptors in Cardiomyocytes.

    Science.gov (United States)

    Palee, Siripong; Apaijai, Nattayaporn; Shinlapawittayatorn, Krekwit; Chattipakorn, Siriporn C; Chattipakorn, Nipon

    2016-01-01

    Oxidative stress induced intracellular Ca2+ overload plays an important role in the pathophysiology of several heart diseases. Acetylcholine (ACh) has been shown to suppress reactive oxygen species generation during oxidative stress. However, there is little information regarding the effects of ACh on the intracellular Ca2+ regulation in the presence of oxidative stress. Therefore, we investigated the effects of ACh applied before or after hydrogen peroxide (H2O2) treatment on the intracellular Ca2+ regulation in isolated cardiomyocytes. Single ventricular myocytes were isolated from the male Wistar rats for the intracellular Ca2+ transient study by a fluorimetric ratio technique. H2O2 significantly decreased both of intracellular Ca2+ transient amplitude and decay rate. ACh applied before, but not after, H2O2 treatment attenuated the reduction of intracellular Ca2+ transient amplitude and decay rate. Both atropine (a muscarinic acetylcholine receptor blocker) and mecamylamine (a nicotinic acetylcholine receptor blocker) significantly decreased the protective effects of acetylcholine on the intracellular Ca2+ regulation. Moreover, the combination of atropine and mecamylamine completely abolished the protective effects of acetylcholine on intracellular Ca2+ transient amplitude and decay rate. ACh pretreatment attenuates H2O2-induced intracellular Ca2+ dyshomeostasis through both muscarinic and nicotinic receptors. © 2016 The Author(s) Published by S. Karger AG, Basel.

  9. Calcium

    Science.gov (United States)

    ... absorb calcium as well. Sufficient calcium intake from food, and supplements if needed, can slow the rate of bone loss. Women of childbearing ... calcium absorption. People who eat a variety of foods don't have to consider ... include consumption of alcohol- and caffeine-containing beverages as well ...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-11-06

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

  11. Prostaglandin E2 Stimulates EP2, Adenylate Cyclase, Phospholipase C, and Intracellular Calcium Release to Mediate Cyclic Adenosine Monophosphate Production in Dental Pulp Cells.

    Science.gov (United States)

    Chang, Mei-Chi; Lin, Szu-I; Lin, Li-Deh; Chan, Chiu-Po; Lee, Ming-Shu; Wang, Tong-Mei; Jeng, Po-Yuan; Yeung, Sin-Yuet; Jeng, Jiiang-Huei

    2016-04-01

    Prostaglandin E2 (PGE2) plays a crucial role in pulpal inflammation and repair. However, its induction of signal transduction pathways is not clear but is crucial for future control of pulpal inflammation. Primary dental pulp cells were exposed to PGE2 and 19R-OH PGE2 (EP2 agonist) or sulprostone (EP1/EP3 agonist) for 5 to 40 minutes. Cellular cyclic adenosine monophosphate (cAMP) levels were measured using the enzyme-linked immunosorbent assay. In some experiments, cells were pretreated with SQ22536 (adenylate cyclase inhibitor), H89 (protein kinase A inhibitor), dorsomorphin (adenosine monophosphate-activated protein kinase inhibitor), U73122 (phospholipase C inhibitor), thapsigargin (inhibitor of intracellular calcium release), W7 (calmodulin antagonist), verapamil (L-type calcium channel blocker), and EGTA (extracellular calcium chelator) for 20 minutes before the addition of PGE2. PGE2 and 19R-OH PGE2 (EP2 agonist) stimulated cAMP production, whereas sulprostone (EP1/EP3 agonist) shows little effect. PGE2-induced cAMP production was attenuated by SQ22536 and U73122 but not H89 and dorsomorphin. Intriguingly, thapsigargin and W7 prevented PGE2-induced cAMP production, but verapamil and EGTA showed little effect. These results indicate that PGE2-induced cAMP production is associated with EP2 receptor and adenylate cyclase activation. These events are mediated by phospholipase C, intracellular calcium release, and calcium-calmodulin signaling. These results are helpful for understanding the role of PGE2 in pulpal inflammation and repair and possible future drug intervention. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  12. Neurosteroids block the increase in intracellular calcium level induced by Alzheimer’s β-amyloid protein in long-term cultured rat hippocampal neurons

    Directory of Open Access Journals (Sweden)

    Midori Kato-Negishi

    2008-03-01

    Full Text Available Midori Kato-Negishi1, Masahiro Kawahara21Department of Developmental Morphology, Tokyo Metropolitan Institute for Neuroscience, 2-6 Musashidai, Fuchu-shi, Tokyo 183- 8526, Japan; 2Department of Analytical Chemistry, School of Pharmaceutical Sciences, Kyushu University of Health and Welfare, 1714-1 Yoshino-cho, Nobeoka-shi, Miyazaki 882-8508, JapanAbstract: The neurotoxicity of β-amyloid protein (AβP is implicated in the etiology of Alzheimer’s disease. We previously have demonstrated that AβP forms Ca2+-permeable pores on neuronal membranes, causes a marked increase in intracellular calcium level, and leads to neuronal death. Here, we investigated in detail the features of AβP-induced changes in intracellular Ca2+ level in primary cultured rat hippocampal neurons using a multisite Ca2+- imaging system with fura-2 as a fluorescent probe. Only a small fraction of short-term cultured hippocampal neurons (ca 1 week in vitro exhibited changes in intracellular Ca2+ level after AβP exposure. However, AβP caused an acute increase in intracellular Ca2+ level in long-term cultured neurons (ca 1 month in vitro. The responses to AβP were highly heterogeneous, and immunohistochemical analysis using an antibody to AβP revealed that AβP is deposited on some but not all neurons. Considering that the disruption of Ca2+ homeostasis is the primary event in AβP neurotoxicity, substances that protect neurons from an AβP-induced intracellular Ca2+ level increase may be candidates as therapeutic drugs for Alzheimer’s disease. In line with the search for such protective substances, we found that the preadministration of neurosteroids including dehydroepiandrosterone, dehydroepiandrosterone sulfate, and pregnenolone significantly inhibits the increase in intracellular calcium level induced by AβP. Our results suggest the possible significance of neurosteroids, whose levels are reduced in the elderly, in preventing AβP neurotoxicity

  13. Ratiometric analysis of fura red by flow cytometry: a technique for monitoring intracellular calcium flux in primary cell subsets.

    Directory of Open Access Journals (Sweden)

    Emily R Wendt

    Full Text Available Calcium flux is a rapid and sensitive measure of cell activation whose utility could be enhanced with better techniques for data extraction. We describe a technique to monitor calcium flux by flow cytometry, measuring Fura Red calcium dye by ratiometric analysis. This technique has several advantages: 1 using a single calcium dye provides an additional channel for surface marker characterization, 2 allows robust detection of calcium flux by minority cell populations within a heterogeneous population of primary T cells and monocytes 3 can measure total calcium flux and additionally, the proportion of responding cells, 4 can be applied to studying the effects of drug treatment, simultaneously stimulating and monitoring untreated and drug treated cells. Using chemokine receptor activation as an example, we highlight the utility of this assay, demonstrating that only cells expressing a specific chemokine receptor are activated by cognate chemokine ligand. Furthermore, we describe a technique for simultaneously stimulating and monitoring calcium flux in vehicle and drug treated cells, demonstrating the effects of the Gαi inhibitor, pertussis toxin (PTX, on chemokine stimulated calcium flux. The described real time calcium flux assay provides a robust platform for characterizing cell activation within primary cells, and offers a more accurate technique for studying the effect of drug treatment on receptor activation in a heterogeneous population of primary cells.

  14. Rhein triggers apoptosis via induction of endoplasmic reticulum stress, caspase-4 and intracellular calcium in primary human hepatic HL-7702 cells

    Energy Technology Data Exchange (ETDEWEB)

    KoraMagazi, Arouna [Department of Clinical Pharmacy, China Pharmaceutical University, Nanjing, Jiangsu (China); Wang, Dandan [Department of Pharmacology, China Pharmaceutical University, Nanjing, Jiangsu (China); Yousef, Bashir; Guerram, Mounia [Jiangsu Key Laboratory of Drug Screening, China Pharmaceutical University, Nanjing, Jiangsu (China); Yu, Feng, E-mail: yufengcpu14@yahoo.com [Department of Clinical Pharmacy, China Pharmaceutical University, Nanjing, Jiangsu (China); Department of Pharmacology, China Pharmaceutical University, Nanjing, Jiangsu (China); Key Laboratory of Drug Quality Control and Pharmacovigilance, China Pharmaceutical University, Nanjing, Jiangsu (China)

    2016-04-22

    Rhein is an active component of rhubarb; a traditional Chinese medicine reported to induce apoptosis and cause liver toxicity. However, rhein's apoptotic-inducing effects, as well as its molecular mechanisms of action on hepatic cells need to be further explored. In the present study, rhein was found to trigger apoptosis in primary human hepatic HL-7702 cells as showed by annexin V/PI double staining assay and nuclear morphological changes demonstrated by Hoechst 33258 staining. Moreover, it was observed that the mechanism implicated in rhein-induced apoptosis was caspase-dependent, presumably via ER-stress associated pathways, as illustrated by up-regulation of glucose-regulated protein 78 (GRP 78), PKR-like ER kinase (PERK), C-Jun N-terminal kinase (JNK) and CCAAT/enhancer-binding protein homologous protein (CHOP). Meanwhile, caspase-4 as a hallmark of ER-stress, was also showed to be activated following by caspase-3 activation. Furthermore, rhein also promoted intracellular elevation of calcium that contributed in apoptosis induction. Interestingly, pre-treatment with calpain inhibitor I reduced the effects of rhein on apoptosis induction and JNK activation. These data suggested that rhein-induced apoptosis through ER-stress and elevated intracellular calcium level in HL-7702 cells. - Highlights: • Rhein triggers apoptotic cell death on primary human hepatic HL-7702 cells. • Rhein leads to caspase-4 activation in HL-7702 cells. • Rhein induces endoplasmic reticulum stress pathways in HL-7702 cells. • Rhein causes elevation of intracellular calcium concentrations in HL-7702 cells.

  15. Mechanical strain stimulates vasculogenesis and expression of angiogenesis guidance molecules of embryonic stem cells through elevation of intracellular calcium, reactive oxygen species and nitric oxide generation.

    Science.gov (United States)

    Sharifpanah, Fatemeh; Behr, Sascha; Wartenberg, Maria; Sauer, Heinrich

    2016-12-01

    Differentiation of embryonic stem (ES) cells may be regulated by mechanical strain. Herein, signaling molecules underlying mechanical stimulation of vasculogenesis and expression of angiogenesis guidance cues were investigated in ES cell-derived embryoid bodies. Treatment of embryoid bodies with 10% static mechanical strain using a Flexercell strain system significantly increased CD31-positive vascular structures and the angiogenesis guidance molecules plexinB1, ephrin B2, neuropilin1 (NRP1), semaphorin 4D (sem4D) and robo4 as well as vascular endothelial growth factor (VEGF), fibroblast growth factor-2 (FGF-2) and platelet-derived growth factor-BB (PDGF-BB) as evaluated by Western blot and real time RT-PCR. In contrast ephrin type 4 receptor B (EphB4) expression was down-regulated upon mechanical strain, indicating an arterial-type differentiation. Robo1 protein expression was modestly increased with no change in mRNA expression. Mechanical strain increased intracellular calcium as well as reactive oxygen species (ROS) and nitric oxide (NO). Mechanical strain-induced vasculogenesis was abolished by the NOS inhibitor L-NAME, the NADPH oxidase inhibitor VAS2870, upon chelation of intracellular calcium by BAPTA as well as upon siRNA inactivation of ephrin B2, NRP1 and robo4. BAPTA blunted the strain-induced expression of angiogenic growth factors, the increase in NO and ROS as well as the expression of NRP1, sem4D and plexinB1, whereas ephrin B2, EphB4 as well as robo1 and robo4 expression were not impaired. Mechanical strain stimulates vasculogenesis of ES cells by the intracellular messengers ROS, NO and calcium as well as by upregulation of angiogenesis guidance molecules and the angiogenic growth factors VEGF, FGF-2 and PDGF-BB. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Acrolein produces nitric oxide through the elevation of intracellular calcium levels to induce apoptosis in human umbilical vein endothelial cells: implications for smoke angiopathy.

    Science.gov (United States)

    Misonou, Yoshiko; Asahi, Michio; Yokoe, Shunichi; Miyoshi, Eiji; Taniguchi, Naoyuki

    2006-03-01

    Acrolein is a highly electrophilic alpha, beta-unsaturated aldehyde, the levels of which are increased in the blood of smokers. To determine if acrolein is involved in the pathology of smoke angiopathy, the effect of acrolein on human umbilical vein endothelial cells (HUVEC) was examined. Intracellular nitric oxide (NO) levels, determined using diaminofluorescein-2 diacetate (DAF-2 DA), an NO sensitive fluorescent dye, were found to be increased after treatment in HUVEC with 10 microM acrolein. The measurement of nitrite with 2,3-diaminonaphthalene and a Western blot analysis revealed that nitrite and S-nitroso-cysteine levels were increased in a dose-dependent manner, confirming that NO production is increased by acrolein. The increase was not reduced by treatment with 10mM N-acetyl-l-cysteine (NAC), an anti-oxidant, but was reduced with 10 microM of the intracellular calcium chelator, 1,2-bis (o-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid tetra (acetoxymethyl) ester. Acrolein-stimulated NO production was significantly reduced by pretreatment with 1mM N(G)-nitro-l-arginine-methyl ester (L-NAME), an NO synthase inhibitor. The cytotoxicity of acrolein was reduced by pretreatment with 10 microM 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (carboxy-PTIO), an intracellular NO scavenger, or 1mM L-NAME, whereas it was not reduced by 10mM NAC, 20 microM Curcumin, another peroxide scavenger, or 100 microM Mn(III)TMPyP, a superoxide dismutase mimic. Nuclear staining and a Western blot analysis using an anti-cleaved caspase 3 antibody revealed that the reduced viability of HUVEC by acrolein was due to apoptosis, which was reversed after pretreatment with 0.1mM carboxy-PTIO or 1mM L-NAME. Thus, acrolein increases intracellular calcium production to induce intracellular NO production by a calcium-dependent NO synthase, possibly eNOS, and the excess and rapid increase in NO might lead to the apoptosis of HUVEC. These data suggest that acrolein might be

  17. Impact of human D398N single nucleotide polymorphism on intracellular calcium response mediated by α3β4α5 nicotinic acetylcholine receptors

    Science.gov (United States)

    Tammimäki, Anne; Herder, Penelope; Li, Ping; Esch, Caroline; Laughlin, James R.; Akk, Gustav; Stitzel, Jerry A.

    2013-01-01

    The human CHRNA5 D398N polymorphism (rs16969968) causes an aspartic acid to asparagine change in the nicotinic acetylcholine receptor (nAChR) α5 subunit gene. The N398 variant of CHRNA5 is linked to increased risk for nicotine dependence. In this study, we explored the effect of the CHRNA5 D398N polymorphism on the properties of human α3β4* nicotinic acetylcholine receptors in human embryonic kidney (HEK) cells. Addition of either D398 or N398 variant of α5 subunit in the α3β4* receptor did not affect total [125I]-epibatidine binding or surface expression of the receptor. However, addition of α5D398 into α3β4* receptor decreased the maximal response to agonist without significantly affecting EC50 in aequorin intracellular calcium assay. α3β4α5N398 nAChRs showed further decreased maximal response. The differences in agonist efficacy between the receptor subtypes were found to be dependent upon the concentration of external calcium but independent of external sodium. Moreover, activation of α3β4α5 nAChRs led to significantly greater intracellular calcium release from IP3 stores relative to α3β4 nAChRs although no effect of the α5 polymorphism was observed. Finally, inclusion of the α5 variant caused a small shift to the left in IC50 for some of the antagonists tested, depending upon α5 variant but did not affect sensitivity of α3β4* receptors to desensitization in response to incubation with nicotine. In conclusion, addition of either variant of a5 into an α3β4α5 receptor similarly effects receptor pharmacology and function. However, the N398 variant exhibits a reduced response to agonists when extracellular calcium is high and it may lead to distinct downstream cellular signaling. PMID:22820273

  18. Regulation of NKG2D-ligand cell surface expression by intracellular calcium after HDAC-inhibitor treatment

    DEFF Research Database (Denmark)

    Jensen, Helle; Hagemann-Jensen, Michael Henrik; Lauridsen, Felicia Kathrine Bratt

    2013-01-01

    cell surface expression on melanoma cells and Jurkat T-cells. A NKG2D-dependent cytolytic assay and staining with a recombinant NKG2D-Fc fusion protein showed that calcium chelation impaired the functional ability of NKG2D-ligands induced by HDAC-inhibitor treatment. The HDAC-inhibitor induced cell...... surface expression of ULBP2, but not MICA/B, was sensitive to treatment calmidazolium and trifluoperazine, two agents known to block calcium signaling. siRNA-mediated knock-down of the calcium-regulated proteins calmodulin or calpain did however not affect NKG2D-ligand cell surface expression on Jurkat T...

  19. Calcium

    Science.gov (United States)

    ... and blood vessels contract and expand, to secrete hormones and enzymes and to send messages through the nervous system. It is important to get plenty of calcium in the foods you eat. Foods rich in calcium include Dairy products such as milk, cheese, and yogurt Leafy, green vegetables Fish with ...

  20. Absence of the ER Cation Channel TMEM38B/TRIC-B Disrupts Intracellular Calcium Homeostasis and Dysregulates Collagen Synthesis in Recessive Osteogenesis Imperfecta.

    Science.gov (United States)

    Cabral, Wayne A; Ishikawa, Masaki; Garten, Matthias; Makareeva, Elena N; Sargent, Brandi M; Weis, MaryAnn; Barnes, Aileen M; Webb, Emma A; Shaw, Nicholas J; Ala-Kokko, Leena; Lacbawan, Felicitas L; Högler, Wolfgang; Leikin, Sergey; Blank, Paul S; Zimmerberg, Joshua; Eyre, David R; Yamada, Yoshihiko; Marini, Joan C

    2016-07-01

    Recessive osteogenesis imperfecta (OI) is caused by defects in proteins involved in post-translational interactions with type I collagen. Recently, a novel form of moderately severe OI caused by null mutations in TMEM38B was identified. TMEM38B encodes the ER membrane monovalent cation channel, TRIC-B, proposed to counterbalance IP3R-mediated Ca2+ release from intracellular stores. The molecular mechanisms by which TMEM38B mutations cause OI are unknown. We identified 3 probands with recessive defects in TMEM38B. TRIC-B protein is undetectable in proband fibroblasts and osteoblasts, although reduced TMEM38B transcripts are present. TRIC-B deficiency causes impaired release of ER luminal Ca2+, associated with deficient store-operated calcium entry, although SERCA and IP3R have normal stability. Notably, steady state ER Ca2+ is unchanged in TRIC-B deficiency, supporting a role for TRIC-B in the kinetics of ER calcium depletion and recovery. The disturbed Ca2+ flux causes ER stress and increased BiP, and dysregulates synthesis of proband type I collagen at multiple steps. Collagen helical lysine hydroxylation is reduced, while telopeptide hydroxylation is increased, despite increased LH1 and decreased Ca2+-dependent FKBP65, respectively. Although PDI levels are maintained, procollagen chain assembly is delayed in proband cells. The resulting misfolded collagen is substantially retained in TRIC-B null cells, consistent with a 50-70% reduction in secreted collagen. Lower-stability forms of collagen that elude proteasomal degradation are not incorporated into extracellular matrix, which contains only normal stability collagen, resulting in matrix insufficiency. These data support a role for TRIC-B in intracellular Ca2+ homeostasis, and demonstrate that absence of TMEM38B causes OI by dysregulation of calcium flux kinetics in the ER, impacting multiple collagen-specific chaperones and modifying enzymes.

  1. Absence of the ER Cation Channel TMEM38B/TRIC-B Disrupts Intracellular Calcium Homeostasis and Dysregulates Collagen Synthesis in Recessive Osteogenesis Imperfecta.

    Directory of Open Access Journals (Sweden)

    Wayne A Cabral

    2016-07-01

    Full Text Available Recessive osteogenesis imperfecta (OI is caused by defects in proteins involved in post-translational interactions with type I collagen. Recently, a novel form of moderately severe OI caused by null mutations in TMEM38B was identified. TMEM38B encodes the ER membrane monovalent cation channel, TRIC-B, proposed to counterbalance IP3R-mediated Ca2+ release from intracellular stores. The molecular mechanisms by which TMEM38B mutations cause OI are unknown. We identified 3 probands with recessive defects in TMEM38B. TRIC-B protein is undetectable in proband fibroblasts and osteoblasts, although reduced TMEM38B transcripts are present. TRIC-B deficiency causes impaired release of ER luminal Ca2+, associated with deficient store-operated calcium entry, although SERCA and IP3R have normal stability. Notably, steady state ER Ca2+ is unchanged in TRIC-B deficiency, supporting a role for TRIC-B in the kinetics of ER calcium depletion and recovery. The disturbed Ca2+ flux causes ER stress and increased BiP, and dysregulates synthesis of proband type I collagen at multiple steps. Collagen helical lysine hydroxylation is reduced, while telopeptide hydroxylation is increased, despite increased LH1 and decreased Ca2+-dependent FKBP65, respectively. Although PDI levels are maintained, procollagen chain assembly is delayed in proband cells. The resulting misfolded collagen is substantially retained in TRIC-B null cells, consistent with a 50-70% reduction in secreted collagen. Lower-stability forms of collagen that elude proteasomal degradation are not incorporated into extracellular matrix, which contains only normal stability collagen, resulting in matrix insufficiency. These data support a role for TRIC-B in intracellular Ca2+ homeostasis, and demonstrate that absence of TMEM38B causes OI by dysregulation of calcium flux kinetics in the ER, impacting multiple collagen-specific chaperones and modifying enzymes.

  2. Absence of the ER Cation Channel TMEM38B/TRIC-B Disrupts Intracellular Calcium Homeostasis and Dysregulates Collagen Synthesis in Recessive Osteogenesis Imperfecta

    Science.gov (United States)

    Cabral, Wayne A.; Ishikawa, Masaki; Garten, Matthias; Makareeva, Elena N.; Sargent, Brandi M.; Weis, MaryAnn; Barnes, Aileen M.; Webb, Emma A.; Shaw, Nicholas J.; Ala-Kokko, Leena; Lacbawan, Felicitas L.; Högler, Wolfgang; Leikin, Sergey; Blank, Paul S.; Zimmerberg, Joshua; Eyre, David R.; Yamada, Yoshihiko; Marini, Joan C.

    2016-01-01

    Recessive osteogenesis imperfecta (OI) is caused by defects in proteins involved in post-translational interactions with type I collagen. Recently, a novel form of moderately severe OI caused by null mutations in TMEM38B was identified. TMEM38B encodes the ER membrane monovalent cation channel, TRIC-B, proposed to counterbalance IP3R-mediated Ca2+ release from intracellular stores. The molecular mechanisms by which TMEM38B mutations cause OI are unknown. We identified 3 probands with recessive defects in TMEM38B. TRIC-B protein is undetectable in proband fibroblasts and osteoblasts, although reduced TMEM38B transcripts are present. TRIC-B deficiency causes impaired release of ER luminal Ca2+, associated with deficient store-operated calcium entry, although SERCA and IP3R have normal stability. Notably, steady state ER Ca2+ is unchanged in TRIC-B deficiency, supporting a role for TRIC-B in the kinetics of ER calcium depletion and recovery. The disturbed Ca2+ flux causes ER stress and increased BiP, and dysregulates synthesis of proband type I collagen at multiple steps. Collagen helical lysine hydroxylation is reduced, while telopeptide hydroxylation is increased, despite increased LH1 and decreased Ca2+-dependent FKBP65, respectively. Although PDI levels are maintained, procollagen chain assembly is delayed in proband cells. The resulting misfolded collagen is substantially retained in TRIC-B null cells, consistent with a 50–70% reduction in secreted collagen. Lower-stability forms of collagen that elude proteasomal degradation are not incorporated into extracellular matrix, which contains only normal stability collagen, resulting in matrix insufficiency. These data support a role for TRIC-B in intracellular Ca2+ homeostasis, and demonstrate that absence of TMEM38B causes OI by dysregulation of calcium flux kinetics in the ER, impacting multiple collagen-specific chaperones and modifying enzymes. PMID:27441836

  3. P2Y13 receptor-mediated rapid increase in intracellular calcium induced by ADP in cultured dorsal spinal cord microglia.

    Science.gov (United States)

    Zeng, Junwei; Wang, Gaoxia; Liu, Xiaohong; Wang, Chunmei; Tian, Hong; Liu, Aidong; Jin, Huan; Luo, Xiaomei; Chen, Yuanshou

    2014-11-01

    P2Y receptors have been implicated in the calcium mobilization by the response to neuroexcitatory substances in neurons and astrocytes, but little is known about P2Y receptors in microglia cells. In the present study, the effects of ADP on the intracellular calcium concentration ([Ca(2+)]i) in cultured dorsal spinal cord microglia were detected with confocal laser scanning microscopy using fluo-4/AM as a calcium fluorescence indicator that could monitor real-time alterations of [Ca(2+)]i. Here we show that ADP (0.01-100 μM) causes a rapid increase in [Ca(2+)]i with a dose-dependent manner in cultured microglia. The action of ADP on [Ca(2+)]i was significantly blocked by MRS2211 (a selective P2Y13 receptor antagonist), but was unaffected by MRS2179 (a selective P2Y1 receptor antagonist) or MRS2395 (a selective P2Y12 receptor antagonist), which suggest that P2Y13 receptor may be responsible for ADP-evoked Ca(2+) mobilization in cultured microglia. P2Y13-evoked Ca(2+) response can be obviously inhibited by BAPTA-AM and U-73122, respectively. Moreover, removal of extracellular Ca(2+) (by EGTA) also can obvious suppress the Ca(2+) mobilization. These results means both intracellular calcium and extracellular calcium are potentially important mechanisms in P2Y13 receptor-evoked Ca(2+) mobilization. However, P2Y13 receptor-evoked Ca(2+) response was not impaired after CdCl2 and verapamil administration, which suggest that voltage-operated Ca(2+) channels may be not related with P2Y13-evoked Ca(2+) response. In addition, Ca(2+) mobilization induced by ADP was abolished by different store-operated Ca(2+) channels (SOCs) blocker, 2-APB (50 μM) and SKF-96365 (1 mM), respectively. These observations suggest that the activation of P2Y13 receptor might be involved in the effect of ADP on [Ca(2+)]i in cultured dorsal spinal cord microglia. Furthermore, our results raise a possibility that P2Y13 receptor activation causes Ca(2+) release from Ca(2+) store, which leads to the

  4. Is Increased Intracellular Calcium in Red Blood Cells a Common Component in the Molecular Mechanism Causing Anemia?

    Directory of Open Access Journals (Sweden)

    Laura Hertz

    2017-09-01

    Full Text Available For many hereditary disorders, although the underlying genetic mutation may be known, the molecular mechanism leading to hemolytic anemia is still unclear and needs further investigation. Previous studies revealed an increased intracellular Ca2+ in red blood cells (RBCs from patients with sickle cell disease, thalassemia, or Gardos channelopathy. Therefore we analyzed RBCs' Ca2+ content from 35 patients with different types of anemia (16 patients with hereditary spherocytosis, 11 patients with hereditary xerocytosis, 5 patients with enzymopathies, and 3 patients with hemolytic anemia of unknown cause. Intracellular Ca2+ in RBCs was measured by fluorescence microscopy using the fluorescent Ca2+ indicator Fluo-4 and subsequent single cell analysis. We found that in RBCs from patients with hereditary spherocytosis and hereditary xerocytosis the intracellular Ca2+ levels were significantly increased compared to healthy control samples. For enzymopathies and hemolytic anemia of unknown cause the intracellular Ca2+ levels in RBCs were not significantly different. These results lead us to the hypothesis that increased Ca2+ levels in RBCs are a shared component in the mechanism causing an accelerated clearance of RBCs from the blood stream in channelopathies such as hereditary xerocytosis and in diseases involving defects of cytoskeletal components like hereditary spherocytosis. Future drug developments should benefit from targeting Ca2+ entry mediating molecular players leading to better therapies for patients.

  5. Y1 receptors for neuropeptide Y are coupled to mobilization of intracellular calcium and inhibition of adenylate cyclase

    DEFF Research Database (Denmark)

    Aakerlund, L; Gether, U; Fuhlendorff, J

    1990-01-01

    Two types of binding sites have previously been described for neuropeptide Y (NPY), called Y1 and Y2 receptors. The intracellular events following Y1 receptor activation was studied in the human neuroblastoma cell line SK-N-MC. Both NPY and the specific Y1 receptor ligand, [Leu31,Pro34]-NPY, caused...

  6. Glucocorticoids can affect Pseudomonas aeruginosa (ATCC 27853) internalization and intracellular calcium concentration in cystic fibrosis bronchial epithelial cells.

    Science.gov (United States)

    Hussain, Rashida; Shahror, Rami; Karpati, Ferenc; Roomans, Godfried M

    2015-01-01

    Glucocorticoids (GCs) are anti-inflammatory agents, but their use in cystic fibrosis (CF) is controversial. In CF, the early colonization with Pseudomonas aeruginosa is mainly due to nonmucoid strains that can internalize, and induce apoptosis in the epithelial cells. Uptake of P. aeruginosa by the epithelial cells and subsequent apoptosis may prevent colonization of P. aeruginosa in CF airways. In the airway epithelia, several other biological effects, including an anti-secretory role by decreasing intracellular Ca(2+) concentration have been described for this anti-inflammatory drug. However, the effects of GCs on the nonmucoid P. aeruginosa internalization and intracellular Ca(2+) in CF bronchial epithelial cells have not been evaluated. We used cultured human CF bronchial airway epithelial cell (CFBE) monolayers to determine P. aeruginosa internalization, apoptosis, and intracellular Ca(2+)concentration in CF bronchial epithelial cells. Cells were treated with IL-6, IL-8, dexamethasone, betamethasone, or budesonide. GCs in co-treatments with IL-6 reversed the effect of IL-6 by decreasing the internalization of P. aeruginosa in the CFBE cells. GCs decreased the extent of apoptosis in CFBE cells infected with internalized P. aeruginosa, and increased the intracellular Ca(2+) concentration. These findings suggest that if internalization of P. aeruginosa reduces infection, GC therapy would increase the risk of pulmonary infection by decreasing the internalization of P. aeruginosa in CF cells, but GCs may improve airway hydration by increasing the intracellular Ca(2+) concentration. Whether the benefits of GC treatment outweigh the negative effects is questionable, and further clinical studies need to be carried out.

  7. Intracellular calcium measurements as a method in studies on activity of purinergic P2X receptor channels

    Czech Academy of Sciences Publication Activity Database

    He, M. L.; Zemková, Hana; Koshimizu, T.; Tomič, M.; Stojilkovic, S. S.

    2003-01-01

    Roč. 285, č. 2 (2003), s. C467-C479 ISSN 0363-6143 Institutional research plan: CEZ:AV0Z5011922 Keywords : P2X purinergic receptor * calcium signaling * membrane current Subject RIV: ED - Physiology Impact factor: 4.103, year: 2003

  8. Ca analysis: An Excel based program for the analysis of intracellular calcium transients including multiple, simultaneous regression analysis☆

    Science.gov (United States)

    Greensmith, David J.

    2014-01-01

    Here I present an Excel based program for the analysis of intracellular Ca transients recorded using fluorescent indicators. The program can perform all the necessary steps which convert recorded raw voltage changes into meaningful physiological information. The program performs two fundamental processes. (1) It can prepare the raw signal by several methods. (2) It can then be used to analyze the prepared data to provide information such as absolute intracellular Ca levels. Also, the rates of change of Ca can be measured using multiple, simultaneous regression analysis. I demonstrate that this program performs equally well as commercially available software, but has numerous advantages, namely creating a simplified, self-contained analysis workflow. PMID:24125908

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

    Science.gov (United States)

    Greensmith, David J

    2014-01-01

    Here I present an Excel based program for the analysis of intracellular Ca transients recorded using fluorescent indicators. The program can perform all the necessary steps which convert recorded raw voltage changes into meaningful physiological information. The program performs two fundamental processes. (1) It can prepare the raw signal by several methods. (2) It can then be used to analyze the prepared data to provide information such as absolute intracellular Ca levels. Also, the rates of change of Ca can be measured using multiple, simultaneous regression analysis. I demonstrate that this program performs equally well as commercially available software, but has numerous advantages, namely creating a simplified, self-contained analysis workflow. Copyright © 2013 The Author. Published by Elsevier Ireland Ltd.. All rights reserved.

  10. Role of intracellular calcium in the spermicidal action of 2',4'-dichlorobenzamil, a novel contact spermicide.

    Science.gov (United States)

    Patni, A K; Gupta, S; Sharma, A; Tiwary, A K; Garg, S K

    2001-10-01

    The Na+-Ca2+ exchanger and Ca2+-ATPase pumps reported to be present on the sperm membrane are responsible for maintaining the intracellular Ca2+ concentration that is involved in regulation of sperm function. We have investigated the role of intracellular Ca2+ in the presence of 2',4'-dichlorobenzamil hydrochloride (benzamil), a Na+-Ca2+ exchange inhibitor, on human sperm motility. The mechanism of the complementary spermicidal action produced by a combination of benzamil and propranolol on human spermatozoa has been investigated also. When administered alone benzamil and propranolol produced a dose- and time-dependent decrease in motility of sperm in ejaculated semen and spermatozoa separated from semen. A combination of benzamil and propranolol exhibited a complementary spermicidal action, thereby resulting in dose reduction of both drugs for obtaining total immotility within 1 min of administration. An increase in the intracellular Ca2+ level was found to contribute to the spermicidal activity. Inhibition of the Na+-Ca2+ exchange system on sperm membrane by benzamil and membrane stabilization by propranolol resulted in accumulation of Ca2+ inside the sperm cells. When the two drugs were used in combination the time required for the total loss of motility of spermatozoa was significantly reduced due to a similar mechanism of action of both drugs.

  11. Intracellular calcium oscillations in strongly metastatic human breast and prostate cancer cells: control by voltage-gated sodium channel activity.

    Science.gov (United States)

    Rizaner, Nahit; Onkal, Rustem; Fraser, Scott P; Pristerá, Alessandro; Okuse, Kenji; Djamgoz, Mustafa B A

    2016-10-01

    The possible association of intracellular Ca 2+ with metastasis in human cancer cells is poorly understood. We have studied Ca 2+ signaling in human prostate and breast cancer cell lines of strongly versus weakly metastatic potential in a comparative approach. Intracellular free Ca 2+ was measured using a membrane-permeant fluorescent Ca 2+ -indicator dye (Fluo-4 AM) and confocal microscopy. Spontaneous Ca 2+ oscillations were observed in a proportion of strongly metastatic human prostate and breast cancer cells (PC-3M and MDA-MB-231, respectively). In contrast, no such oscillations were observed in weakly/non metastatic LNCaP and MCF-7 cells, although a rise in the resting Ca 2+ level could be induced by applying a high-K + solution. Various parameters of the oscillations depended on extracellular Ca 2+ and voltage-gated Na + channel activity. Treatment with either tetrodotoxin (a general blocker of voltage-gated Na + channels) or ranolazine (a blocker of the persistent component of the channel current) suppressed the Ca 2+ oscillations. It is concluded that the functional voltage-gated Na + channel expression in strongly metastatic cancer cells makes a significant contribution to generation of oscillatory intracellular Ca 2+ activity. Possible mechanisms and consequences of the Ca 2+ oscillations are discussed.

  12. Intracellular calcium movements during excitation–contraction coupling in mammalian slow-twitch and fast-twitch muscle fibers

    Science.gov (United States)

    Hollingworth, Stephen

    2012-01-01

    In skeletal muscle fibers, action potentials elicit contractions by releasing calcium ions (Ca2+) from the sarcoplasmic reticulum. Experiments on individual mouse muscle fibers micro-injected with a rapidly responding fluorescent Ca2+ indicator dye reveal that the amount of Ca2+ released is three- to fourfold larger in fast-twitch fibers than in slow-twitch fibers, and the proportion of the released Ca2+ that binds to troponin to activate contraction is substantially smaller. PMID:22450485

  13. Vcx1 and ESCRT components regulate intracellular pH homeostasis in the response of yeast cells to calcium stress

    Czech Academy of Sciences Publication Activity Database

    Papoušková, Klára; Jiang, L.; Sychrová, Hana

    2015-01-01

    Roč. 15, č. 2 (2015), fov007 ISSN 1567-1356 R&D Projects: GA ČR(CZ) GAP503/10/0307; GA MŠk(CZ) LH14297; GA MŠk(CZ) ED1.1.00/02.0109 Institutional support: RVO:67985823 Keywords : calcium * ESCRT * pHin * Vcx1 Subject RIV: EE - Microbiology, Virology Impact factor: 2.479, year: 2015

  14. Silver ions increase plasma membrane permeability through modulation of intracellular calcium levels in tobacco BY-2 cells

    Czech Academy of Sciences Publication Activity Database

    Klíma, Petr; Laňková, Martina; Vandenbussche, F.; Van Der Straeten, D.; Petrášek, Jan

    2018-01-01

    Roč. 37, č. 5 (2018), s. 809-818 ISSN 0721-7714 R&D Projects: GA ČR GA16-10948S Grant - others:OPPK(XE) CZ.2.16/3.1.00/21519 Institutional support: RVO:61389030 Keywords : Auxin * Calcium * Ethylene * Silver ions * Tobacco BY-2 cells * Transmembrane transport Subject RIV: ED - Physiology OBOR OECD: Cell biology Impact factor: 2.869, year: 2016

  15. The effect of tetraethylammonium on intracellular calcium concentration in Alzheimer's disease fibroblasts with APP, S182 and E5-1 missense mutations.

    Science.gov (United States)

    Failli, P; Tesco, G; Ruocco, C; Ginestroni, A; Amaducci, L; Giotti, A; Sorbi, S

    1996-04-26

    It has been proposed that the lack of intracellular calcium concentration ([Ca2+]i) increase induced by the potassium channel blocker tetraethylammonium (TEA) in skin fibroblast cell lines identifies patients with both sporadic and familial Alzheimer's disease (AD). In order to verify this hypothesis, the effect of TEA on [Ca2+]i was studied in single fura-2-loaded skin fibroblast cell lines available in the Tissue Bank of the Italian Research Council. Four out of eight familial AD patients (one patient with S182 mutation, one patient with E5-1 mutation and two patients with 717 Val-->Ile APP mutation) and two out of five sporadic AD patients showed a positive response to TEA, whereas five out of 11 control lines were unresponsive. Our data suggest that the absence of the TEA-induced increase in [Ca2+]i in skin fibroblast cell lines does not identify all AD patients.

  16. Heat shock protein 90 has roles in intracellular calcium homeostasis, protein tyrosine phosphorylation regulation, and progesterone-responsive sperm function in human sperm.

    Science.gov (United States)

    Li, Kun; Xue, Yamei; Chen, Aijun; Jiang, Youfang; Xie, Haifeng; Shi, Qixian; Zhang, Songying; Ni, Ya

    2014-01-01

    Heat shock protein 90 plays critical roles in client protein maturation, signal transduction, protein folding and degradation, and morphological evolution; however, its function in human sperm is not fully understood. Therefore, our objective in this study was to elucidate the mechanism by which heat shock protein 90 exerts its effects on human sperm function. By performing indirect immunofluorescence staining, we found that heat shock protein 90 was localized primarily in the neck, midpiece, and tail regions of human sperm, and that its expression increased with increasing incubation time under capacitation conditions. Geldanamycin, a specific inhibitor of heat shock protein 90, was shown to inhibit this increase in heat shock protein 90 expression in western blotting analyses. Using a multifunctional microplate reader to examine Fluo-3 AM-loaded sperm, we observed for the first time that inhibition of heat shock protein 90 by using geldanamycin significantly decreased intracellular calcium concentrations during capacitation. Moreover, western blot analysis showed that geldanamycin enhanced tyrosine phosphorylation of several proteins, including heat shock protein 90, in a dose-dependent manner. The effects of geldanamycin on human sperm function in the absence or presence of progesterone was evaluated by performing chlortetracycline staining and by using a computer-assisted sperm analyzer. We found that geldanamycin alone did not affect sperm capacitation, hyperactivation, and motility, but did so in the presence of progesterone. Taken together, these data suggest that heat shock protein 90, which increases in expression in human sperm during capacitation, has roles in intracellular calcium homeostasis, protein tyrosine phosphorylation regulation, and progesterone-stimulated sperm function. In this study, we provide new insights into the roles of heat shock protein 90 in sperm function.

  17. A novel role of the L-type calcium channel α1D subunit as a gatekeeper for intracellular zinc signaling: zinc wave.

    Directory of Open Access Journals (Sweden)

    Satoru Yamasaki

    Full Text Available Recent studies have shown that zinc ion (Zn can behave as an intracellular signaling molecule. We previously demonstrated that mast cells stimulated through the high-affinity IgE receptor (FcεRI rapidly release intracellular Zn from the endoplasmic reticulum (ER, and we named this phenomenon the "Zn wave". However, the molecules responsible for releasing Zn and the roles of the Zn wave were elusive. Here we identified the pore-forming α(1 subunit of the Cav1.3 (α(1D L-type calcium channel (LTCC as the gatekeeper for the Zn wave. LTCC antagonists inhibited the Zn wave, and an agonist was sufficient to induce it. Notably, α(1D was mainly localized to the ER rather than the plasma membrane in mast cells, and the Zn wave was impaired by α(1D knockdown. We further found that the LTCC-mediated Zn wave positively controlled cytokine gene induction by enhancing the DNA-binding activity of NF-κB. Consistent with this finding, LTCC antagonists inhibited the cytokine-mediated delayed-type allergic reaction in mice without affecting the immediate-type allergic reaction. These findings indicated that the LTCC α(1D subunit located on the ER membrane has a novel function as a gatekeeper for the Zn wave, which is involved in regulating NF-κB signaling and the delayed-type allergic reaction.

  18. Extra and intracellular calcium signaling pathway(s) differentially regulate histamine-induced myometrial contractions during early and mid-pregnancy stages in buffaloes (Bubalus bubalis).

    Science.gov (United States)

    Sharma, Abhishek; Nakade, Udayraj P; Choudhury, Soumen; Yadav, Rajkumar Singh; Garg, Satish Kumar

    2017-04-01

    This study examines the differential role of calcium signaling pathway(s) in histamine-induced uterotonic action during early and mid-pregnancy stages in buffaloes. Compared to mid pregnancy, tonic contraction, amplitude and mean-integral tension were significantly increased by histamine to produce myometrial contraction during early pregnancy with small effects on phasic contraction and frequency. Although uterotonic action of histamine during both stages of pregnancy is sensitive to nifedipine (a L-type Ca 2+ channels blocker) and NNC55-0396 (T-type Ca 2+ channels blocker), the role of extracellular calcium seems to be more significant during mid-pregnancy as in this stage histamine produced only 9.38±0.96% contraction in Ca 2+ free-RLS compared to 21.60±1.45% in uteri of early pregnancy stage. Intracellular calcium plays major role in histamine-induced myometrial contraction during early pregnancy as compared to mid pregnancy, as in the presence of cyclopiazonic acid (CPA) Ca 2+ -free RLS, histamine produced significantly higher contraction in myometrial strips of early-pregancy in comparison to mid-pregnancy (10.59±1.58% and 3.13±0.46%, respectively). In the presence of U-73122, the DRC of histamine was significantly shifted towards right with decrease in maximal effect (E max ) only in early pregnancy suggesting the predominant role of phospholipase-C (PL-C) in this stage of pregnancy. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. 17β-estradiol rapidly activates calcium release from intracellular stores via the GPR30 pathway and MAPK phosphorylation in osteocyte-like MLO-Y4 cells

    KAUST Repository

    Ren, Jian

    2012-03-06

    Estrogen regulates critical cellular functions, and its deficiency initiates bone turnover and the development of bone mass loss in menopausal females. Recent studies have demonstrated that 17β-estradiol (E 2) induces rapid non-genomic responses that activate downstream signaling molecules, thus providing a new perspective to understand the relationship between estrogen and bone metabolism. In this study, we investigated rapid estrogen responses, including calcium release and MAPK phosphorylation, in osteocyte-like MLO-Y4 cells. E 2 elevated [Ca 2+] i and increased Ca 2+ oscillation frequency in a dose-dependent manner. Immunolabeling confirmed the expression of three estrogen receptors (ERα, ERβ, and G protein-coupled receptor 30 [GPR30]) in MLO-Y4 cells and localized GPR30 predominantly to the plasma membrane. E 2 mobilized calcium from intracellular stores, and the use of selective agonist(s) for each ER showed that this was mediated mainly through the GPR30 pathway. MAPK phosphorylation increased in a biphasic manner, with peaks occurring after 7 and 60 min. GPR30 and classical ERs showed different temporal effects on MAPK phosphorylation and contributed to MAPK phosphorylation sequentially. ICI182,780 inhibited E 2 activation of MAPK at 7 min, while the GPR30 agonist G-1 and antagonist G-15 failed to affect MAPK phosphorylation levels. G-1-mediated MAPK phosphorylation at 60 min was prevented by prior depletion of calcium stores. Our data suggest that E 2 induces the non-genomic responses Ca 2+ release and MAPK phosphorylation to regulate osteocyte function and indicate that multiple receptors mediate rapid E 2 responses. © 2012 Springer Science+Business Media, LLC.

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

    Science.gov (United States)

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

    2009-01-01

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

  1. Effect of atorvastatin on intracellular calcium uptake in coronary smooth muscle cells from diabetic pigs fed an atherogenic diet.

    Science.gov (United States)

    Hill, B J; Dixon, J L; Sturek, M

    2001-11-01

    Intracellular Ca(2+) store loading has been shown to alter proliferation and apoptosis of several cell types. In addition, HMG-CoA reductase inhibitors (i.e. atorvastatin) are effective in treating diabetic dyslipidemic patients. Thus, we hypothesized that chronic atorvastatin treatment would prevent increased Ca(2+) uptake into intracellular Ca(2+) stores in vascular smooth muscle cells from diabetic dyslipidemic pigs. Male Yucatan pigs were divided into four groups for 20 weeks-- (1) low fat fed (control); (2) hyperlipidemic (F); (3) alloxan-induced diabetic dyslipidemic (DF); and (4) diabetic dyslipidemic pigs treated with atorvastatin (DFA). The F, DF, and DFA groups were fed a high fat/cholesterol diet. Cells were isolated from the coronary artery and the myoplasmic Ca(2+) (Ca(m)) response measured using single cell fura-2 imaging. The Ca(m) response to caffeine (5 mM to release Ca(2+) from the sarcoplasmic reticulum, SR) and ionomycin (10 microM; to release the total Ca(2+) store) was determined in either the presence of low Na (19Na; inhibits Na(+)-Ca(2+) exchange), thapsigargin (TSG; inhibits the SR Ca(2+) pump), and a 19Na+TSG solution. Low Na induced the uptake of Ca(2+) into both SR and non-SR Ca(2+) stores in the DF group, but not the DFA group. Furthermore, after depletion of the SR Ca(2+) store with TSG, 19Na evoked Ca(2+) uptake into non-SR Ca(2+) stores in all three groups except in the DFA group. In summary, this study demonstrates that atorvastatin prevents the enhanced uptake of Ca(2+) by SR and non-SR Ca(2+) stores in diabetic dyslipidemic pigs.

  2. Synaptic plasticity at the interface of health and disease: New insights on the role of endoplasmic reticulum intracellular calcium stores.

    Science.gov (United States)

    Maggio, N; Vlachos, A

    2014-12-05

    Work from the past 40years has unraveled a wealth of information on the cellular and molecular mechanisms underlying synaptic plasticity and their relevance in physiological brain function. At the same time, it has been recognized that a broad range of neurological diseases may be accompanied by severe alterations in synaptic plasticity, i.e., 'maladaptive synaptic plasticity', which could initiate and sustain the remodeling of neuronal networks under pathological conditions. Nonetheless, our current knowledge on the specific contribution and interaction of distinct forms of synaptic plasticity (including metaplasticity and homeostatic plasticity) in the context of pathological brain states remains limited. This review focuses on recent experimental evidence, which highlights the fundamental role of endoplasmic reticulum-mediated Ca(2+) signals in modulating the duration, direction, extent and type of synaptic plasticity. We discuss the possibility that intracellular Ca(2+) stores may regulate synaptic plasticity and hence behavioral and cognitive functions at the interface between physiology and pathology. Copyright © 2014 IBRO. Published by Elsevier Ltd. All rights reserved.

  3. Methylmercury-induced toxicity is mediated by enhanced intracellular calcium through activation of phosphatidylcholine-specific phospholipase C

    International Nuclear Information System (INIS)

    Kang, Mi Sun; Jeong, Ju Yeon; Seo, Ji Heui; Jeon, Hyung Jun; Jung, Kwang Mook; Chin, Mi-Reyoung; Moon, Chang-Kiu; Bonventre, Joseph V.; Jung, Sung Yun; Kim, Dae Kyong

    2006-01-01

    Methylmercury (MeHg) is a ubiquitous environmental toxicant to which humans can be exposed by ingestion of contaminated food. MeHg has been suggested to exert its toxicity through its high reactivity to thiols, generation of arachidonic acid and reactive oxygen species (ROS), and elevation of free intracellular Ca 2+ levels ([Ca 2+ ] i ). However, the precise mechanism has not been fully defined. Here we show that phosphatidylcholine-specific phospholipase C (PC-PLC) is a critical pathway for MeHg-induced toxicity in MDCK cells. D609, an inhibitor of PC-PLC, significantly reversed the toxicity in a time- and dose-dependent manner with concomitant inhibition of the diacylglycerol (DAG) generation and the phosphatidylcholine (PC)-breakdown. MeHg activated the group IV cytosolic phospholipase A 2 (cPLA 2 ) and acidic form of sphingomyelinase (A-SMase) downstream of PC-PLC, but these enzymes as well as protein kinase C (PKC) were not linked to the toxicity by MeHg. Furthermore, MeHg produced ROS, which did not affect the toxicity. Addition of EGTA to culture media resulted in partial decrease of [Ca 2+ ] i and partially blocked the toxicity. In contrast, when the cells were treated with MeHg in the presence of Ca 2+ in the culture media, D609 completely prevented cell death with parallel decrease in [Ca 2+ ] i . Our results demonstrated that MeHg-induced toxicity was linked to elevation of [Ca 2+ ] i through activation of PC-PLC, but not attributable to the signaling pathways such as cPLA 2 , A-SMase, and PKC, or to the generation of ROS

  4. Intracellular calcium is a target of modulation of apoptosis in MCF-7 cells in the presence of IgA adsorbed to polyethylene glycol

    Science.gov (United States)

    Honorio-França, Adenilda Cristina; Nunes, Gabriel Triches; Fagundes, Danny Laura Gomes; de Marchi, Patrícia Gelli Feres; Fernandes, Rubian Trindade da Silva; França, Juliana Luzia; França-Botelho, Aline do Carmo; Moraes, Lucélia Campelo Albuquerque; Varotti, Fernando de Pilla; França, Eduardo Luzía

    2016-01-01

    Purpose Clinical and epidemiological studies have indicated that breastfeeding has a protective effect on breast cancer risk. Protein-based drugs, including antibodies, are being developed to attain better forms of cancer therapy. Secretory IgA (SIgA) is the antibody class in human breast milk, and its activity can be linked to the protective effect of breastfeeding. The aim of this study was to investigate the effect of polyethylene glycol (PEG) microspheres with adsorbed SIgA on MCF-7 human breast cancer cells. Methods The PEG microspheres were characterized by flow cytometry and fluorescence microscopy. The MCF-7 cells were obtained from American Type Culture Collection. MCF-7 cells were pre-incubated for 24 hours with or without SIgA (100 ng/mL), PEG microspheres or SIgA adsorbed in PEG microspheres (100 ng/mL). Viability, intracellular calcium release, and apoptosis in MCF-7 cells were determined by flow cytometry. Results Fluorescence microscopy and flow cytometry analyses revealed that SIgA was able to adsorb to the PEG microspheres. The MCF-7 cells that were incubated with PEG microspheres with adsorbed SIgA showed decreased viability. MCF-7 cells that were incubated with SIgA or PEG microspheres with adsorbed SIgA had increased intracellular Ca2+ levels. In the presence of SIgA, an increase in the percentage of apoptotic cells was observed. The highest apoptosis index was observed when the cells were treated with PEG microspheres with adsorbed SIgA. Conclusion These data suggest that colostral SIgA adsorbed to PEG microspheres has antitumor effects on human MCF-7 breast cancer cells and that the presence of large amounts of this protein in secreted breast milk may provide protection against breast tumors in women who breastfed. PMID:26893571

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

    Science.gov (United States)

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

    2014-05-01

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

  6. Arsenic-induced alteration in intracellular calcium homeostasis induces head kidney macrophage apoptosis involving the activation of calpain-2 and ERK in Clarias batrachus

    International Nuclear Information System (INIS)

    Banerjee, Chaitali; Goswami, Ramansu; Datta, Soma; Rajagopal, R.; Mazumder, Shibnath

    2011-01-01

    We had earlier shown that exposure to arsenic (0.50 μM) caused caspase-3 mediated head kidney macrophage (HKM) apoptosis involving the p38-JNK pathway in Clarias batrachus. Here we examined the roles of calcium (Ca 2+ ) and extra-cellular signal-regulated protein kinase (ERK), the other member of MAPK-pathway on arsenic-induced HKM apoptosis. Arsenic-induced HKM apoptosis involved increased expression of ERK and calpain-2. Nifedipine, verapamil and EGTA pre-treatment inhibited the activation of calpain-2, ERK and reduced arsenic-induced HKM apoptosis as evidenced from reduced caspase-3 activity, Annexin V-FITC-propidium iodide and Hoechst 33342 staining. Pre-incubation with ERK inhibitor U 0126 inhibited the activation of calpain-2 and interfered with arsenic-induced HKM apoptosis. Additionally, pre-incubation with calpain-2 inhibitor also interfered with the activation of ERK and inhibited arsenic-induced HKM apoptosis. The NADPH oxidase inhibitor apocynin and diphenyleneiodonium chloride also inhibited ERK activation indicating activation of ERK in arsenic-exposed HKM also depends on signals from NADPH oxidase pathway. Our study demonstrates the critical role of Ca 2+ homeostasis on arsenic-induced HKM apoptosis. We suggest that arsenic-induced alteration in intracellular Ca 2+ levels initiates pro-apoptotic ERK and calpain-2; the two pathways influence each other positively and induce caspase-3 mediated HKM apoptosis. Besides, our study also indicates the role of ROS in the activation of ERK pathway in arsenic-induced HKM apoptosis in C. batrachus. - Highlights: → Altered Ca 2+ homeostasis leads to arsenic-induced HKM apoptosis. → Calpain-2 plays a critical role in the process. → ERK is pro-apoptotic in arsenic-induced HKM apoptosis. → Arsenic-induced HKM apoptosis involves cross talk between calpain-2 and ERK.

  7. GABAAα1 and GABAAρ1 subunits are expressed in cultured human RPE cells and GABAA receptor agents modify the intracellular calcium concentration.

    Science.gov (United States)

    Cheng, Zhen-Ying; Wang, Xu-Ping; Schmid, Katrina L; Han, Xu-Guang; Song, Hui; Tang, Xin

    2015-01-01

    Gamma-aminobutyric acid A (GABAA) receptors (GABAARs), which are ionotropic receptors involving chloride channels, have been identified in various neural (e.g., mouse retinal ganglion cells) and nonneural cells (e.g., mouse lens epithelial cells) regulating the intracellular calcium concentration ([Ca(2+)]i). GABAAR β-subunit protein has been isolated in the cultured human and rat RPE, and GABAAα1 and GABAAρ1 mRNAs and proteins are present in the chick RPE. The purpose of this study was to investigate the expression of GABAAα1 and GABAAρ1, two important subunits in forming functional GABAARs, in the cultured human RPE, and further to explore whether altering receptor activation modifies [Ca(2+)]i. Human RPE cells were separately cultured from five donor eye cups. Real-time PCR, western blots, and immunofluorescence were used to test for GABAAα1 and GABAAρ1 mRNAs and proteins. The effects of the GABAAR agonist muscimol, antagonist picrotoxin, or the specific GABAAρ antagonist 1,2,5,6-tetrahydropyridin-4-yl) methylphosphinic acid (TPMPA) on [Ca(2+)]i in cultured human RPE were demonstrated using Fluo3-AM. Both GABAAα1 and GABAAρ1 mRNAs and proteins were identified in cultured human RPE cells; antibody staining was mainly localized to the cell membrane and was also present in the cytoplasm but not in the nucleus. Muscimol (100 μM) caused a transient increase of the [Ca(2+)]i in RPE cells regardless of whether Ca(2+) was added to the buffer. Muscimol-induced increases in the [Ca(2+)]i were inhibited by pretreatment with picrotoxin (300 μM) or TPMPA (500 μM). GABAAα1 and GABAAρ1 are expressed in cultured human RPE cells, and GABAA agents can modify [Ca(2+)]i.

  8. The effect of TGF-beta-induced epithelial-mesenchymal transition on the expression of intracellular calcium-handling proteins in T47D and MCF-7 human breast cancer cells.

    Science.gov (United States)

    Mahdi, Shah H A; Cheng, Huanyi; Li, Jinfeng; Feng, Renqing

    2015-10-01

    The contribution of Ca(2+) in TGF-β-induced EMT is poorly understood. We aimed to confirm the effect of TGF-β on the gene expression of intracellular calcium-handling proteins and to investigate the potential underlying mechanisms in TGF-β-induced EMT. T47D and MCF-7 cells were cultured in vitro and treated with TGF-β. The mRNA expression of EMT marker genes and intracellular calcium-handling proteins were quantified by qRT-PCR. qRT-PCR and Western blot analysis results verified the changes of EMT marker gene expression. Furthermore, we found that TGF-β induced cell morphological changes significantly with an increase of cell surface area and cell length. These results indicated that TGF-β induced EMT. The mRNA expression levels of SPCA1, SPCA2 and MCU were not influenced by TGF-β treatment, while NCX1 expression was decreased in T47D cells. In addition, the mRNA levels of SERCAs and IP3Rs were significantly changed due to TGF-β-induced EMT. The TGF-β-treated T47D cells exhibited markedly greater response to ATP than the control cells, and the descent velocity of cytosolic calcium concentration was faster in TGF-β-treated cells than in control cells. This is the first report to demonstrate that TGF-β-induced EMT in human breast cancer cells is associated with alterations in endoplasmic reticulum calcium homeostasis. Copyright © 2015 Elsevier Inc. All rights reserved.

  9. Low-concentration hydrogen peroxide can upregulate keratinocyte intracellular calcium and PAR-2 expression in a human keratinocyte-melanocyte co-culture system.

    Science.gov (United States)

    Li, Jian; Tang, Lu-Yan; Fu, Wen-Wen; Yuan, Jin; Sheng, You-Yu; Yang, Qin-Ping

    2016-12-01

    Hydrogen peroxide (H 2 O 2 ) may have a biphasic effect on melanin synthesis and melanosome transfer. High H 2 O 2 concentrations are involved in impaired melanosome transfer in vitiligo. However, low H 2 O 2 concentration promotes the beneficial proliferation and migration of melanocytes. The aim of this study was to explore low H 2 O 2 and its mechanism in melanosome transfer, protease-activated receptor-2 (PAR-2) expression and calcium balance. Melanosomes were fluorescein-labeled for clear visualization of their transfer. The expression of protease-activated receptor-2 (PAR-2) in keratinocytes was determined by western blot analysis. Flow cytometry was employed to evaluate the effects of H 2 O 2 on calcium levels in keratinocytes. Fluorescence microscopy showed the upregulation of melanosome transfer into keratinocytes following 0.3 mM H 2 O 2 treatment in the co-cultures rather than in the untreated control groups, which was associated with higher expression of PAR-2 protein and increased calcium concentration. The addition of a PAR-2 antagonist inhibited the positive activity of H 2 O 2 and calcium flow in keratinocytes. When calcium flow was blocked by a calcium chelator, the addition of H 2 O 2 did not increase the PAR-2 expression level in keratinocytes, therefore, inhibiting dendrite formation and melanosome transfer. Low H 2 O 2 concentration promotes melanosome transfer with increased PAR-2 expression level and calcium concentration in keratinocytes. In addition, the interaction between melanocytes and keratinocytes is more beneficial to enhance calcium levels in keratinocytes which mediate melanin transfer. Moreover, low H 2 O 2 concentration promotes dendrite formation, in which extracellular calcium and Par-2 were involved.

  10. Contribution of α4β2 nAChR in nicotine-induced intracellular calcium response and excitability of MSDB neurons.

    Science.gov (United States)

    Wang, Jiangang; Wang, Yali; Wang, Yang; Wang, Ran; Zhang, Yunpeng; Zhang, Qian; Lu, Chengbiao

    2014-12-10

    The neurons of medial septal diagonal band of broca (MSDB) project to hippocampus and play an important role in MSDB-hippocampal synaptic transmission, plasticity and network oscillation. Nicotinic acetylcholine receptor (nAChR) subunits, α4β2 and α7 nAChRs, are expressed in MSDB neurons and permeable to calcium ions, which may modulate the function of MSDB neurons. The aims of this study are to determine the roles of selective nAChR activation on the calcium responses and membrane currents in MSDB neurons. Our results showed that nicotine increased calcium responses in the majority of MSDB neurons, pre-treatment of MSDB slices with a α4β2 nAChR antagonist, DhβE but not a α7 nAChR antagonist, MLA prevented nicotine-induced calcium responses. The whole cell patch clamp recordings showed that nicotine-induced inward current and acetylcholine (ACh) induced-firing activity can be largely reduced or prevented by DhβE in MSDB neurons. Surprisingly, post-treatment of α4β2 or α7 nAChR antagonists failed to block nicotine׳s role, they increased calcium responses instead. Application of calcium chelator EGTA reduced calcium responses in all neurons tested. These results suggest that there was a subtype specific modulation of nAChRs on calcium signaling and membrane currents in MSDB neurons and nAChR antagonists were also able to induce calcium responses involving a distinct mechanism.

  11. Deep Spiking Networks

    NARCIS (Netherlands)

    O'Connor, P.; Welling, M.

    2016-01-01

    We introduce an algorithm to do backpropagation on a spiking network. Our network is "spiking" in the sense that our neurons accumulate their activation into a potential over time, and only send out a signal (a "spike") when this potential crosses a threshold and the neuron is reset. Neurons only

  12. Selenium potentiates the anticancer effect of cisplatin against oxidative stress and calcium ion signaling-induced intracellular toxicity in MCF-7 breast cancer cells: involvement of the TRPV1 channel.

    Science.gov (United States)

    Sakallı Çetin, Esin; Nazıroğlu, Mustafa; Çiğ, Bilal; Övey, İshak Suat; Aslan Koşar, Pınar

    2017-02-01

    In breast cancers, calcium signaling is a main cause of proliferation and apoptosis of breast cancer cells. Although previous studies have implicated the transient receptor potential vanilloid 1 (TRPV1) cation channel, the synergistic inhibition effects of selenium (Se) and cisplatin in cancer and the suppression of ongoing apoptosis have not yet been investigated in MCF-7 breast cancer cells. This study investigates the anticancer properties of Se through TRPV1 channel activity in MCF-7 breast cancer cell line cultures when given alone or in combination with cisplatin. The MCF-7 cells were divided into four groups: the control group, the Se-treated group (200 nM), the cisplatin-treated group (40 μM) and the Se + cisplatin-treated group. The intracellular free calcium ion concentration and current densities increased with TRPV1 channel activator capsaicin (0.01 mM), but they decreased with the TRPV1 blocker capsazepine (0.1 mM), Se, cisplatin, and Se + cisplatin incubations. However, mitochondrial membrane depolarization, apoptosis, and the caspase 3, and caspase 9 values increased in the Se-treated group and the cisplatin-treated group, although Western blot (procaspase 3 and 9) results and the cell viability levels decreased with the Se and Se + cisplatin treatments. Apoptosis and caspase-3 were further increased with the Se + cisplatin treatment. Intracellular reactive oxygen species production increased with the cisplatin treatment, but not with the Se treatment. This study's results report, for the first time, that at a cellular level, Se and cisplatin interact on the same intracellular toxic cascade, and the combination of these two drugs can result in a remarkable anticancer effect through modulation of the TRPV1.

  13. PDGF-mediated protection of SH-SY5Y cells against Tat toxin involves regulation of extracellular glutamate and intracellular calcium

    International Nuclear Information System (INIS)

    Zhu Xuhui; Yao Honghong; Peng Fuwang; Callen, Shannon; Buch, Shilpa

    2009-01-01

    The human immunodeficiency virus (HIV-1) protein Tat has been implicated in mediating neuronal apoptosis, one of the hallmark features of HIV-associated dementia (HAD). Mitigation of the toxic effects of Tat could thus be a potential mechanism for reducing HIV toxicity in the brain. In this study we demonstrated that Tat-induced neurotoxicity was abolished by NMDA antagonist-MK801, suggesting the role of glutamate in this process. Furthermore, we also found that pretreatment of SH-SY5Y cells with PDGF exerted protection against Tat toxicity by decreasing extracellular glutamate levels. We also demonstrated that extracellular calcium chelator EGTA was able to abolish PDGF-mediated neuroprotection, thereby underscoring the role of calcium signaling in PDGF-mediated neuroprotection. We also showed that Erk signaling pathway was critical for PDGF-mediated protection of cells. Additionally, blocking calcium entry with EGTA resulted in suppression of PDGF-induced Erk activation. These findings thus underscore the role of PDGF-mediated calcium signaling and Erk phosphorylation in the protection of cells against HIV Tat toxicity.

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

    International Nuclear Information System (INIS)

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

    2010-01-01

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

  15. Activation of intracellular calcium by multiple Wnt ligands and translocation of β-catenin into the nucleus: a convergent model of Wnt/Ca2+ and Wnt/β-catenin pathways.

    Science.gov (United States)

    Thrasivoulou, Christopher; Millar, Michael; Ahmed, Aamir

    2013-12-13

    Ca(2+) and β-catenin, a 92-kDa negatively charged transcription factor, transduce Wnt signaling via the non-canonical, Wnt/Ca(2+) and canonical, Wnt/β-catenin pathways independently. The nuclear envelope is a barrier to large protein entry, and this process is regulated by intracellular calcium [Ca(2+)]i and trans-nuclear potential. How β-catenin traverses the nuclear envelope is not well known. We hypothesized that Wnt/Ca(2+) and Wnt/β-catenin pathways act in a coordinated manner and that [Ca(2+)]i release facilitates β-catenin entry into the nucleus in mammalian cells. In a live assay using calcium dyes in PC3 prostate cancer cells, six Wnt peptides (3A, 4, 5A, 7A, 9B, and 10B) mobilized [Ca(2+)]i but Wnt11 did not. Based upon dwell time (range = 15-30 s) of the calcium waveform, these Wnts could be classified into three classes: short, 3A and 5A; long, 7A and 10B; and very long, 4 and 9B. Wnt-activated [Ca(2+)]i release was followed by an increase in intranuclear calcium and the depolarization of both the cell and nuclear membranes, determined by using FM4-64. In cells treated with Wnts 5A, 9B, and 10B, paradigm substrates for each Wnt class, increased [Ca(2+)]i was followed by β-catenin translocation into the nucleus in PC3, MCF7, and 253J, prostate, breast, and bladder cancer cell lines; both the increase in Wnt 5A, 9B, and 10B induced [Ca(2+)]i release and β-catenin translocation are suppressed by thapsigargin in PC3 cell line. We propose a convergent model of Wnt signaling network where Ca(2+) and β-catenin pathways may act in a coordinated, interdependent, rather than independent, manner.

  16. Calcium Electroporation

    DEFF Research Database (Denmark)

    Frandsen, Stine Krog; Gibot, Laure; Madi, Moinecha

    2015-01-01

    ), and a breast adenocarcinoma (MDA-MB231), as well as on primary normal human dermal fibroblasts (HDF-n). RESULTS: The results showed a clear reduction in spheroid size in all three cancer cell spheroids three days after treatment with respectively calcium electroporation (p...-malignant as well as normal. CONCLUSION: In conclusion, calcium electroporation seems to be more effective in inducing cell death in cancer cell spheroids than in a normal fibroblast spheroid, even though intracellular ATP level is depleted in all spheroid types after treatment. These results may indicate......BACKGROUND: Calcium electroporation describes the use of high voltage electric pulses to introduce supraphysiological calcium concentrations into cells. This promising method is currently in clinical trial as an anti-cancer treatment. One very important issue is the relation between tumor cell kill...

  17. Butyrate increases intracellular calcium levels and enhances growth hormone release from rat anterior pituitary cells via the G-protein-coupled receptors GPR41 and 43.

    Directory of Open Access Journals (Sweden)

    Maria Consolata Miletta

    Full Text Available Butyrate is a short-chain fatty acid (SCFA closely related to the ketone body ß-hydroxybutyrate (BHB, which is considered to be the major energy substrate during prolonged exercise or starvation. During fasting, serum growth hormone (GH rises concomitantly with the accumulation of BHB and butyrate. Interactions between GH, ketone bodies and SCFA during the metabolic adaptation to fasting have been poorly investigated to date. In this study, we examined the effect of butyrate, an endogenous agonist for the two G-protein-coupled receptors (GPCR, GPR41 and 43, on non-stimulated and GH-releasing hormone (GHRH-stimulated hGH secretion. Furthermore, we investigated the potential role of GPR41 and 43 on the generation of butyrate-induced intracellular Ca2+ signal and its ultimate impact on hGH secretion. To study this, wt-hGH was transfected into a rat pituitary tumour cell line stably expressing the human GHRH receptor. Treatment with butyrate promoted hGH synthesis and improved basal and GHRH-induced hGH-secretion. By acting through GPR41 and 43, butyrate enhanced intracellular free cytosolic Ca2+. Gene-specific silencing of these receptors led to a partial inhibition of the butyrate-induced intracellular Ca2+ rise resulting in a decrease of hGH secretion. This study suggests that butyrate is a metabolic intermediary, which contributes to the secretion and, therefore, to the metabolic actions of GH during fasting.

  18. Butyrate increases intracellular calcium levels and enhances growth hormone release from rat anterior pituitary cells via the G-protein-coupled receptors GPR41 and 43.

    Science.gov (United States)

    Miletta, Maria Consolata; Petkovic, Vibor; Eblé, Andrée; Ammann, Roland A; Flück, Christa E; Mullis, Primus-E

    2014-01-01

    Butyrate is a short-chain fatty acid (SCFA) closely related to the ketone body ß-hydroxybutyrate (BHB), which is considered to be the major energy substrate during prolonged exercise or starvation. During fasting, serum growth hormone (GH) rises concomitantly with the accumulation of BHB and butyrate. Interactions between GH, ketone bodies and SCFA during the metabolic adaptation to fasting have been poorly investigated to date. In this study, we examined the effect of butyrate, an endogenous agonist for the two G-protein-coupled receptors (GPCR), GPR41 and 43, on non-stimulated and GH-releasing hormone (GHRH)-stimulated hGH secretion. Furthermore, we investigated the potential role of GPR41 and 43 on the generation of butyrate-induced intracellular Ca2+ signal and its ultimate impact on hGH secretion. To study this, wt-hGH was transfected into a rat pituitary tumour cell line stably expressing the human GHRH receptor. Treatment with butyrate promoted hGH synthesis and improved basal and GHRH-induced hGH-secretion. By acting through GPR41 and 43, butyrate enhanced intracellular free cytosolic Ca2+. Gene-specific silencing of these receptors led to a partial inhibition of the butyrate-induced intracellular Ca2+ rise resulting in a decrease of hGH secretion. This study suggests that butyrate is a metabolic intermediary, which contributes to the secretion and, therefore, to the metabolic actions of GH during fasting.

  19. Characterization of Helicobacter pylori VacA-containing vacuoles (VCVs), VacA intracellular trafficking and interference with calcium signalling in T lymphocytes.

    Science.gov (United States)

    Kern, Beate; Jain, Utkarsh; Utsch, Ciara; Otto, Andreas; Busch, Benjamin; Jiménez-Soto, Luisa; Becher, Dörte; Haas, Rainer

    2015-12-01

    The human pathogen Helicobacter pylori colonizes half of the global population. Residing at the stomach epithelium, it contributes to the development of diseases such as gastritis, duodenal and gastric ulcers, and gastric cancer. A major factor is the secreted vacuolating toxin VacA, which forms anion-selective channels in the endosome membrane that cause the compartment to swell, but the composition and purpose of the resulting VacA-containing vacuoles (VCVs) are still unknown. VacA exerts influence on the host immune response in various ways, including inhibition of T-cell activation and proliferation and suppression of the host immune response. In this study, for the first time the composition of VCVs from T cells was comprehensively analysed to investigate VCV function. VCVs were successfully isolated via immunomagnetic separation, and the purified vacuoles were analysed by mass spectrometry. We detected a set of 122 VCV-specific proteins implicated among others in immune response, cell death and cellular signalling processes, all of which VacA is known to influence. One of the individual proteins studied further was stromal interaction molecule (STIM1), a calcium sensor residing in the endoplasmic reticulum (ER) that is important in store-operated calcium entry. Live cell imaging microscopy data demonstrated colocalization of VacA with STIM1 in the ER and indicated that VacA may interfere with the movement of STIM1 towards the plasma membrane-localized calcium release activated calcium channel protein ORAI1 in response to Ca(2+) store depletion. Furthermore, VacA inhibited the increase of cytosolic-free Ca(2+) in the Jurkat E6-1 T-cell line and human CD4(+) T cells. The presence of VacA in the ER and its trafficking to the Golgi apparatus was confirmed in HeLa cells, identifying these two cellular compartments as novel VacA target structures. © 2015 John Wiley & Sons Ltd.

  20. Spike train encoding by regular-spiking cells of the visual cortex.

    Science.gov (United States)

    Carandini, M; Mechler, F; Leonard, C S; Movshon, J A

    1996-11-01

    1. To study the encoding of input currents into output spike trains by regular-spiking cells, we recorded intracellularly from slices of the guinea pig visual cortex while injecting step, sinusoidal, and broadband noise currents. 2. When measured with sinusoidal currents, the frequency tuning of the spike responses was markedly band-pass. The preferred frequency was between 8 and 30 Hz, and grew with stimulus amplitude and mean intensity. 3. Stimulation with broadband noise currents dramatically enhanced the gain of the spike responses at low and high frequencies, yielding an essentially flat frequency tuning between 0.1 and 130 Hz. 4. The averaged spike responses to sinusoidal currents exhibited two nonlinearities: rectification and spike synchronization. By contrast, no nonlinearity was evident in the averaged responses to broadband noise stimuli. 5. These properties of the spike responses were not present in the membrane potential responses. The latter were roughly linear, and their frequency tuning was low-pass and well fit by a single-compartment passive model of the cell membrane composed of a resistance and a capacitance in parallel (RC circuit). 6. To account for the spike responses, we used a "sandwich model" consisting of a low-pass linear filter (the RC circuit), a rectification nonlinearity, and a high-pass linear filter. The model is described by six parameters and predicts analog firing rates rather than discrete spikes. It provided satisfactory fits to the firing rate responses to steps, sinusoids, and broadband noise currents. 7. The properties of spike encoding are consistent with temporal nonlinearities of the visual responses in V1, such as the dependence of response frequency tuning and latency on stimulus contrast and bandwidth. We speculate that one of the roles of the high-frequency membrane potential fluctuations observed in vivo could be to amplify and linearize the responses to lower, stimulus-related frequencies.

  1. An Overview of Bayesian Methods for Neural Spike Train Analysis

    Directory of Open Access Journals (Sweden)

    Zhe Chen

    2013-01-01

    Full Text Available Neural spike train analysis is an important task in computational neuroscience which aims to understand neural mechanisms and gain insights into neural circuits. With the advancement of multielectrode recording and imaging technologies, it has become increasingly demanding to develop statistical tools for analyzing large neuronal ensemble spike activity. Here we present a tutorial overview of Bayesian methods and their representative applications in neural spike train analysis, at both single neuron and population levels. On the theoretical side, we focus on various approximate Bayesian inference techniques as applied to latent state and parameter estimation. On the application side, the topics include spike sorting, tuning curve estimation, neural encoding and decoding, deconvolution of spike trains from calcium imaging signals, and inference of neuronal functional connectivity and synchrony. Some research challenges and opportunities for neural spike train analysis are discussed.

  2. The intracellular delivery of TAT-aequorin reveals calcium-mediated sensing of environmental and symbiotic signals by the arbuscular mycorrhizal fungus Gigaspora margarita.

    Science.gov (United States)

    Moscatiello, Roberto; Sello, Simone; Novero, Mara; Negro, Alessandro; Bonfante, Paola; Navazio, Lorella

    2014-08-01

    Arbuscular mycorrhiza (AM) is an ecologically relevant symbiosis between most land plants and Glomeromycota fungi. The peculiar traits of AM fungi have so far limited traditional approaches such as genetic transformation. The aim of this work was to investigate whether the protein transduction domain of the HIV-1 transactivator of transcription (TAT) protein, previously shown to act as a potent nanocarrier for macromolecule delivery in both animal and plant cells, may translocate protein cargoes into AM fungi. We evaluated the internalization into germinated spores of Gigaspora margarita of two recombinant TAT fusion proteins consisting of either a fluorescent (GFP) or a luminescent (aequorin) reporter linked to the TAT peptide. Both TAT-fused proteins were found to enter AM fungal mycelia after a short incubation period (5-10 min). Ca2+ measurements in G. margarita mycelia pre-incubated with TAT-aequorin demonstrated the occurrence of changes in the intracellular free Ca2+ concentration in response to relevant stimuli, such as touch, cold, salinity, and strigolactones, symbiosis-related plant signals. These data indicate that the cell-penetrating properties of the TAT peptide can be used as an effective strategy for intracellularly delivering proteins of interest and shed new light on Ca2+ homeostasis and signalling in AM fungi. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

  3. Strategies for mapping synaptic inputs on dendrites in vivo by combining two-photon microscopy, sharp intracellular recording and pharmacology

    Directory of Open Access Journals (Sweden)

    Manuel eLevy

    2012-12-01

    Full Text Available Uncovering the functional properties of individual synaptic inputs on single neurons is critical for understanding the computational role of synapses and dendrites. Previous studies combined whole-cell patch recording to load neurons with a fluorescent calcium indicator and two-photon imaging to map subcellular changes in fluorescence upon sensory stimulation. By hyperpolarizing the neuron below spike threshold, the patch electrode ensured that changes in fluorescence associated with synaptic events were isolated from those caused by back-propagating action potentials. This technique holds promise for determining whether the existence of unique cortical feature maps across different species may be associated with distinct wiring diagrams. However, the use of whole-cell patch for mapping inputs on dendrites is challenging in large mammals, due to brain pulsations and the accumulation of fluorescent dye in the extracellular milieu. Alternatively, sharp intracellular electrodes have been used to label neurons with fluorescent dyes, but the current passing capabilities of these high impedance electrodes may be insufficient to prevent spiking. In this study, we tested whether sharp electrode recording is suitable for mapping functional inputs on dendrites in the cat visual cortex. We compared three different strategies for suppressing visually evoked spikes: (1 hyperpolarization by intracellular current injection, (2 pharmacological blockade of voltage-gated sodium channels by intracellular QX-314, and (3 GABA iontophoresis from a perisomatic electrode glued to the intracellular electrode. We found that functional inputs on dendrites could be successfully imaged using all three strategies. However, the best method for preventing spikes was GABA iontophoresis with low currents (5 to 10 nA, which minimally affected the local circuit. Our methods advance the possibility of determining functional connectivity in preparations where whole-cell patch may be

  4. Functional proteins involved in regulation of intracellular Ca(2+) for drug development: the extracellular calcium receptor and an innovative medical approach to control secondary hyperparathyroidism by calcimimetics.

    Science.gov (United States)

    Nagano, Nobuo; Nemeth, Edward F

    2005-03-01

    Circulating levels of calcium ion (Ca(2+)) are maintained within a narrow physiological range mainly by the action of parathyroid hormone (PTH) secreted from parathyroid cells. Parathyroid cells can sense small fluctuations in plasma Ca(2+) levels by virtue of a cell surface Ca(2+) receptor (CaR) that belongs to the superfamily of G-protein-coupled receptors. Calcimimetics are positive allosteric modulators that activate the CaR on parathyroid cells and thereby immediately suppress PTH secretion. Pre-clinical studies with NPS R-568, a first generation calcimimetic compound, have demonstrated that daily oral administration inhibits the elevation of plasma PTH levels and parathyroid gland hyperplasia and ameliorates impaired bone qualities in rats with chronic renal insufficiency. The results of clinical trials with cinacalcet hydrochloride, a second generation calcimimetic compound, have shown that calcimimetics possess lowering effects not only on serum PTH levels but also on serum calcium x phosphorus product levels, a hallmark of an increased risk for cardiovascular death in dialysis patients with end-stage renal disease (ESRD). Thus, calcimimetics have considerable potential as an innovative medical approach to manage secondary hyperparathyroidism associated with ESRD. Indeed, cinacalcet hydrochloride has been approved in several countries and is the first positive allosteric modulator of any G protein-coupled receptor to reach the market.

  5. Aniracetam restores the effects of amyloid-beta protein or ageing on membrane fluidity and intracellular calcium concentration in mice synaptosomes.

    Science.gov (United States)

    Li, Y; Wang, J-J; Cai, J-X

    2007-01-01

    In the present study, we observed the in vitro effect of aniracetam on membrane fluidity and free calcium concentrations ([Ca(2+)]i) of frontal cortical (FC) and hippocampal (HP) synaptosomes of aged mice and young mice treated with amyloid-beta protein (Abeta) Membrane fluidity was measured by using fluorescence anisotropy of the lipophilic probe, 1,6-diphenyl-1,3,5-hexatriene (DPH). [Ca(2+)]i was measured by using Fura 2-AM fluorescent spectrophotometry. We found that membrane fluidity of the FC and HP synaptosomes was decreased in 14 months old mice compared with that in 3 months old mice. Similarly, Abeta25-35 (1 microM) decreased the membrane fluidity in 3 months old mice. These effects of ageing and Abeta25-35 on membrane fluidity were restored by aniracetam in a concentration-dependent manner. Furthermore, Abeta25-35 (1 microM) largely increased [Ca(2+)]i in FC and HP synaptosomes in 3 months old mice, but this effect on HP synaptosomes was effectively reversed by aniracetam (1-4 mM). The present findings suggest that aniracetam restores age- and Abeta-induced alterations in membrane fluidity or Abeta-induced increase in [Ca(2+)]i, demonstrating a possible beneficial role of aniracetam in the clinic treatment for senile dementia or Alzheimer's disease.

  6. Preeclampsia serum-induced collagen I expression and intracellular calcium levels in arterial smooth muscle cells are mediated by the PLC-γ1 pathway.

    Science.gov (United States)

    Jiang, Rongzhen; Teng, Yincheng; Huang, Yajuan; Gu, Jinghong; Ma, Li; Li, Ming; Zhou, Yuedi

    2014-09-26

    In women with preeclampsia (PE), endothelial cell (EC) dysfunction can lead to altered secretion of paracrine factors that induce peripheral vasoconstriction and proteinuria. This study examined the hypothesis that PE sera may directly or indirectly, through human umbilical vein ECs (HUVECs), stimulate phospholipase C-γ1-1,4,5-trisphosphate (PLC-γ1-IP3) signaling, thereby increasing protein kinase C-α (PKC-α) activity, collagen I expression and intracellular Ca(2+) concentrations ([Ca(2+)]i) in human umbilical artery smooth muscle cells (HUASMCs). HUASMCs and HUVECs were cocultured with normal or PE sera before PLC-γ1 silencing. Increased PLC-γ1 and IP3 receptor (IP3R) phosphorylation was observed in cocultured HUASMCs stimulated with PE sera (P<0.05). In addition, PE serum significantly increased HUASMC viability and reduced their apoptosis (P<0.05); these effects were abrogated with PLC-γ1 silencing. Compared with normal sera, PE sera increased [Ca(2+)]i in cocultured HUASMCs (P<0.05), which was inhibited by PLC-γ1 and IP3R silencing. Finally, PE sera-induced PKC-α activity and collagen I expression was inhibited by PLC-γ1 small interfering RNA (siRNA) (P<0.05). These results suggest that vasoactive substances in the PE serum may induce deposition in the extracellular matrix through the activation of PLC-γ1, which may in turn result in thickening and hardening of the placental vascular wall, placental blood supply shortage, fetal hypoxia-ischemia and intrauterine growth retardation or intrauterine fetal death. PE sera increased [Ca(2+)]i and induced PKC-α activation and collagen I expression in cocultured HUASMCs via the PLC-γ1 pathway.

  7. The effect of pulsed electric fields on the electrotactic migration of human neural progenitor cells through the involvement of intracellular calcium signaling.

    Science.gov (United States)

    Hayashi, Hisamitsu; Edin, Fredrik; Li, Hao; Liu, Wei; Rask-Andersen, Helge

    2016-12-01

    Endogenous electric fields (EFs) are required for the physiological control of the central nervous system development. Application of the direct current EFs to neural stem cells has been studied for the possibility of stem cell transplantation as one of the therapies for brain injury. EFs generated within the nervous system are often associated with action potentials and synaptic activity, apparently resulting in a pulsed current in nature. The aim of this study is to investigate the effect of pulsed EF, which can reduce the cytotoxicity, on the migration of human neural progenitor cells (hNPCs). We applied the mono-directional pulsed EF with a strength of 250mV/mm to hNPCs for 6h. The migration distance of the hNPCs exposed to pulsed EF was significantly greater compared with the control not exposed to the EF. Pulsed EFs, however, had less of an effect on the migration of the differentiated hNPCs. There was no significant change in the survival of hNPCs after exposure to the pulsed EF. To investigate the role of Ca 2+ signaling in electrotactic migration of hNPCs, pharmacological inhibition of Ca 2+ channels in the EF-exposed cells revealed that the electrotactic migration of hNPCs exposed to Ca 2+ channel blockers was significantly lower compared to the control group. The findings suggest that the pulsed EF induced migration of hNPCs is partly influenced by intracellular Ca 2+ signaling. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. The Analysis of Intracellular and Intercellular Calcium Signaling in Human Anterior Lens Capsule Epithelial Cells with Regard to Different Types and Stages of the Cataract.

    Directory of Open Access Journals (Sweden)

    Marko Gosak

    Full Text Available In this work we investigated how modifications of the Ca2+ homeostasis in anterior lens epithelial cells (LECs are associated with different types of cataract (cortical or nuclear and how the progression of the cataract (mild or moderate affects the Ca2+ signaling. We systematically analyzed different aspects of intra- and inter-cellular Ca2+ signaling in the human LECs, which are attached to surgically isolated lens capsule (LC, obtained during cataract surgery. We monitored the temporal and spatial changes in intracellular Ca2+ concentration after stimulation with acetylcholine by means of Fura-2 fluorescence captured with an inverted microscope. In our analysis we compared the features of Ca2+ signals in individual cells, synchronized activations, spatio-temporal grouping and the nature of intercellular communication between LECs. The latter was assessed by using the methodologies of the complex network theory. Our results point out that at the level of individual cells there are no significant differences when comparing the features of the signals with regard either to the type or the stage of the cataract. On the other hand, noticeable differences are observed at the multicellular level, despite inter-capsule variability. LCs associated with more developed cataracts were found to exhibit a slower collective response to stimulation, a less pronounced spatio-temporal clustering of LECs with similar signaling characteristics. The reconstructed intercellular networks were found to be sparser and more segregated than in LCs associated with mild cataracts. Moreover, we show that spontaneously active LECs often operate in localized groups with quite well aligned Ca2+ activity. The presence of spontaneous activity was also found to affect the stimulated Ca2+ responses of individual cells. Our findings indicate that the cataract progression entails the impairment of intercellular signaling thereby suggesting the functional importance of altered Ca2

  9. Computational modeling of spike generation in serotonergic neurons of the dorsal raphe nucleus.

    Science.gov (United States)

    Tuckwell, Henry C; Penington, Nicholas J

    2014-07-01

    Serotonergic neurons of the dorsal raphe nucleus, with their extensive innervation of limbic and higher brain regions and interactions with the endocrine system have important modulatory or regulatory effects on many cognitive, emotional and physiological processes. They have been strongly implicated in responses to stress and in the occurrence of major depressive disorder and other psychiatric disorders. In order to quantify some of these effects, detailed mathematical models of the activity of such cells are required which describe their complex neurochemistry and neurophysiology. We consider here a single-compartment model of these neurons which is capable of describing many of the known features of spike generation, particularly the slow rhythmic pacemaking activity often observed in these cells in a variety of species. Included in the model are 11 kinds of ion channels: a fast sodium current INa, a delayed rectifier potassium current IKDR, a transient potassium current IA, a slow non-inactivating potassium current IM, a low-threshold calcium current IT, two high threshold calcium currents IL and IN, small and large conductance potassium currents ISK and IBK, a hyperpolarization-activated cation current IH and a leak current ILeak. In Sections 3-8, each current type is considered in detail and parameters estimated from voltage clamp data where possible. Three kinds of model are considered for the BK current and two for the leak current. Intracellular calcium ion concentration Cai is an additional component and calcium dynamics along with buffering and pumping is discussed in Section 9. The remainder of the article contains descriptions of computed solutions which reveal both spontaneous and driven spiking with several parameter sets. Attention is focused on the properties usually associated with these neurons, particularly long duration of action potential, steep upslope on the leading edge of spikes, pacemaker-like spiking, long-lasting afterhyperpolarization

  10. Aqueous extract of tamarind seeds selectively increases glucose transporter-2, glucose transporter-4, and islets' intracellular calcium levels and stimulates β-cell proliferation resulting in improved glucose homeostasis in rats with streptozotocin-induced diabetes mellitus.

    Science.gov (United States)

    Sole, Sushant Shivdas; Srinivasan, B P

    2012-08-01

    Tamarindus indica Linn. has been in use for a long time in Asian food and traditional medicine for different diseases including diabetes and obesity. However, the molecular mechanisms of these effects have not been fully understood. In view of the multidimensional activity of tamarind seeds due to their having high levels of polyphenols and flavonoids, we hypothesized that the insulin mimetic effect of aqueous tamarind seed extract (TSE) might increase glucose uptake through improvement in the expression of genes of the glucose transporter (GLUT) family and sterol regulatory element-binding proteins (SREBP) 1c messenger RNA (mRNA) in the liver. Daily oral administration of TSE to streptozotocin (STZ)-induced (90 mg/kg intraperitoneally) type 2 diabetic male Wistar rats at different doses (120 and 240 mg/kg body weight) for 4 weeks showed positive correlation with intracellular calcium and insulin release in isolated islets of Langerhans. Tamarind seed extract supplementation significantly improved the GLUT-2 protein and SREBP-1c mRNA expression in the liver and GLUT-4 protein and mRNA expression in the skeletal muscles of diabetic rats. The elevated levels of serum nitric oxide (NO), glycosylated hemoglobin level (hemoglobin (A1c)) and tumor necrosis factor α (TNF-α) decreased after TSE administration. Immunohistochemical findings revealed that TSE abrogated STZ-induced apoptosis and increased β-cell neogenesis, indicating its effect on islets and β-cell mass. In conclusion, it was found that the antidiabetic effect of TSE on STZ-induced diabetes resulted from complex mechanisms of β-cell neogenesis, calcium handling, GLUT-2, GLUT-4, and SREBP-1c. These findings show the scope for formulating a new herbal drug for diabetes therapy. Copyright © 2012 Elsevier Inc. All rights reserved.

  11. Spike Frequency Adaptation in Neurons of the Central Nervous System.

    Science.gov (United States)

    Ha, Go Eun; Cheong, Eunji

    2017-08-01

    Neuronal firing patterns and frequencies determine the nature of encoded information of the neurons. Here we discuss the molecular identity and cellular mechanisms of spike-frequency adaptation in central nervous system (CNS) neurons. Calcium-activated potassium (K Ca ) channels such as BK Ca and SK Ca channels have long been known to be important mediators of spike adaptation via generation of a large afterhyperpolarization when neurons are hyper-activated. However, it has been shown that a strong hyperpolarization via these K Ca channels would cease action potential generation rather than reducing the frequency of spike generation. In some types of neurons, the strong hyperpolarization is followed by oscillatory activity in these neurons. Recently, spike-frequency adaptation in thalamocortical (TC) and CA1 hippocampal neurons is shown to be mediated by the Ca 2+ -activated Cl- channel (CACC), anoctamin-2 (ANO2). Knockdown of ANO2 in these neurons results in significantly reduced spike-frequency adaptation accompanied by increased number of spikes without shifting the firing mode, which suggests that ANO2 mediates a genuine form of spike adaptation, finely tuning the frequency of spikes in these neurons. Based on the finding of a broad expression of this new class of CACC in the brain, it can be proposed that the ANO2-mediated spike-frequency adaptation may be a general mechanism to control information transmission in the CNS neurons.

  12. Curcumin inhibits apoptosis by regulating intracellular calcium release, reactive oxygen species and mitochondrial depolarization levels in SH-SY5Y neuronal cells.

    Science.gov (United States)

    Uğuz, Abdülhadi Cihangir; Öz, Ahmi; Nazıroğlu, Mustafa

    2016-08-01

    Neurological diseases such as Alzheimer's and Parkinson's diseases are incurable progressive neurological disorders caused by the degeneration of neuronal cells and characterized by motor and non-motor symptoms. Curcumin, a turmeric product, is an anti-inflammatory agent and an effective reactive oxygen and nitrogen species scavenging molecule. Hydrogen peroxide (H2O2) is the main source of oxidative stress, which is claimed to be the major source of neurological disorders. Hence, in this study we aimed to investigate the effect of curcumin on Ca(2+) signaling, oxidative stress parameters, mitochondrial depolarization levels and caspase-3 and -9 activities that are induced by the H2O2 model of oxidative stress in SH-SY5Y neuronal cells. SH-SY5Y neuronal cells were divided into four groups namely, the control, curcumin, H2O2, and curcumin + H2O2 groups. The dose and duration of curcumin and H2O2 were determined from published data. The cells in the curcumin, H2O2, and curcumin + H2O2 groups were incubated for 24 h with 5 µM curcumin and 100 µM H2O2. Lipid peroxidation and cytosolic free Ca(2+) concentrations were higher in the H2O2 group than in the control group; however, their levels were lower in the curcumin and curcumin + H2O2 groups than in the H2O2 group alone. Reduced glutathione (GSH) and glutathione peroxidase (GSH-Px) values were lower in the H2O2 group although they were higher in the curcumin and curcumin + H2O2 groups than in the H2O2 group. Caspase-3 activity was lower in the curcumin group than in the H2O2 group. In conclusion, curcumin strongly induced modulator effects on oxidative stress, intracellular Ca(2+) levels, and the caspase-3 and -9 values in an experimental oxidative stress model in SH-SY5Y cells.

  13. Role of Calcium and Calmodulin in Plant Cell Regulation

    Science.gov (United States)

    Cormier, M. J.

    1983-01-01

    The role of calcium and calmodulin in plant cell regulation is discussed. Experiments are done to discover the level of calcium in plants and animals. The effect of intracellular calcium on photosynthesis is discussed.

  14. Calcium dynamics predict direction of synaptic plasticity in striatal spiny projection neurons.

    Science.gov (United States)

    Jędrzejewska-Szmek, Joanna; Damodaran, Sriraman; Dorman, Daniel B; Blackwell, Kim T

    2017-04-01

    The striatum is a major site of learning and memory formation for sensorimotor and cognitive association. One of the mechanisms used by the brain for memory storage is synaptic plasticity - the long-lasting, activity-dependent change in synaptic strength. All forms of synaptic plasticity require an elevation in intracellular calcium, and a common hypothesis is that the amplitude and duration of calcium transients can determine the direction of synaptic plasticity. The utility of this hypothesis in the striatum is unclear in part because dopamine is required for striatal plasticity and in part because of the diversity in stimulation protocols. To test whether calcium can predict plasticity direction, we developed a calcium-based plasticity rule using a spiny projection neuron model with sophisticated calcium dynamics including calcium diffusion, buffering and pump extrusion. We utilized three spike timing-dependent plasticity (STDP) induction protocols, in which postsynaptic potentials are paired with precisely timed action potentials and the timing of such pairing determines whether potentiation or depression will occur. Results show that despite the variation in calcium dynamics, a single, calcium-based plasticity rule, which explicitly considers duration of calcium elevations, can explain the direction of synaptic weight change for all three STDP protocols. Additional simulations show that the plasticity rule correctly predicts the NMDA receptor dependence of long-term potentiation and the L-type channel dependence of long-term depression. By utilizing realistic calcium dynamics, the model reveals mechanisms controlling synaptic plasticity direction, and shows that the dynamics of calcium, not just calcium amplitude, are crucial for synaptic plasticity. © 2016 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

  15. Spiking and bursting patterns of fractional-order Izhikevich model

    Science.gov (United States)

    Teka, Wondimu W.; Upadhyay, Ranjit Kumar; Mondal, Argha

    2018-03-01

    Bursting and spiking oscillations play major roles in processing and transmitting information in the brain through cortical neurons that respond differently to the same signal. These oscillations display complex dynamics that might be produced by using neuronal models and varying many model parameters. Recent studies have shown that models with fractional order can produce several types of history-dependent neuronal activities without the adjustment of several parameters. We studied the fractional-order Izhikevich model and analyzed different kinds of oscillations that emerge from the fractional dynamics. The model produces a wide range of neuronal spike responses, including regular spiking, fast spiking, intrinsic bursting, mixed mode oscillations, regular bursting and chattering, by adjusting only the fractional order. Both the active and silent phase of the burst increase when the fractional-order model further deviates from the classical model. For smaller fractional order, the model produces memory dependent spiking activity after the pulse signal turned off. This special spiking activity and other properties of the fractional-order model are caused by the memory trace that emerges from the fractional-order dynamics and integrates all the past activities of the neuron. On the network level, the response of the neuronal network shifts from random to scale-free spiking. Our results suggest that the complex dynamics of spiking and bursting can be the result of the long-term dependence and interaction of intracellular and extracellular ionic currents.

  16. Cytoplasmic tail of coronavirus spike protein has intracellular ...

    Indian Academy of Sciences (India)

    2017-04-18

    Apr 18, 2017 ... protein, hemagglutinin from the influenza virus, sorts to the apical domain (Mora et al. 2002). To mediate budding ..... After 48 h of post-transfection, cell was immunolabelled using rabbit anti-HCoV-SARS S protein antisera for SARS-S-Y construct (b) and rabbit anti-BCV antisera for OC43-S-Y construct (e) ...

  17. Cytoplasmic tail of coronavirus spike protein has intracellular ...

    Indian Academy of Sciences (India)

    Journal of Biosciences. Current Issue : Vol. 43, Issue 1 · Current Issue Volume 43 | Issue 1. March 2018. Home · Volumes & Issues · Special Issues · Forthcoming Articles · Gallery of Cover Art · Search · Online submission at eBiosciences · Editorial Board · Information for Authors · Subscription ...

  18. Spiking Neurons for Analysis of Patterns

    Science.gov (United States)

    Huntsberger, Terrance

    2008-01-01

    neurons). These features enable the neurons to adapt their responses to high-rate inputs from sensors, and to adapt their firing thresholds to mitigate noise or effects of potential sensor failure. The mathematical derivation of the SVM starts from a prior model, known in the art as the point soma model, which captures all of the salient properties of neuronal response while keeping the computational cost low. The point-soma latency time is modified to be an exponentially decaying function of the strength of the applied potential. Choosing computational efficiency over biological fidelity, the dendrites surrounding a neuron are represented by simplified compartmental submodels and there are no dendritic spines. Updates to the dendritic potential, calcium-ion concentrations and conductances, and potassium-ion conductances are done by use of equations similar to those of the point soma. Diffusion processes in dendrites are modeled by averaging among nearest-neighbor compartments. Inputs to each of the dendritic compartments come from sensors. Alternatively or in addition, when an affected neuron is part of a pool, inputs can come from other spiking neurons. At present, SVM neural networks are implemented by computational simulation, using algorithms that encode the SVM and its submodels. However, it should be possible to implement these neural networks in hardware: The differential equations for the dendritic and cellular processes in the SVM model of spiking neurons map to equivalent circuits that can be implemented directly in analog very-large-scale integrated (VLSI) circuits.

  19. Role of oxidative stress and intracellular calcium in nickel carbonate hydroxide-induced sister-chromatid exchange, and alterations in replication index and mitotic index in cultured human peripheral blood lymphocytes

    Energy Technology Data Exchange (ETDEWEB)

    M' Bemba-Meka, Prosper [Universite de Montreal, Human Toxicology Research Group (TOXHUM), Department of Environmental and Occupational Health, Main Station, P.O. Box 6128, Montreal, QC (Canada); University of Louisville, Department of Pharmacology and Toxicology, Center for Genetics and Molecular Medicine, Louisville, KY (United States); Lemieux, Nicole [Universite de Montreal, Department of Pathology and Cellular Biology, Faculty of Medicine, Main Station, P.O. Box 6128, Montreal, QC (Canada); Chakrabarti, Saroj K. [Universite de Montreal, Human Toxicology Research Group (TOXHUM), Department of Environmental and Occupational Health, Main Station, P.O. Box 6128, Montreal, QC (Canada)

    2007-02-15

    Human peripheral lymphocytes from whole blood cultures were exposed to either soluble form of nickel carbonate hydroxide (NiCH) (0-60 {mu}M), or of nickel subsulfide (Ni{sub 3}S{sub 2}) (0-120 {mu}M), or of nickel oxide (NiO) (0-120 {mu}M), or nickel sulfate (NiSO{sub 4}) (0-120 {mu}M) for a short duration of 2 h. The treatments occurred 46 h after the beginning of the cultures. The cultures were harvested after a total incubation of 72 h, and sister-chromatid exchange (SCE), replication index (RI), and mitotic index (MI) were measured for each nickel compound. The soluble form of NiCH at 30 {mu}M but those of Ni{sub 3}S{sub 2} and NiO at 120 {mu}M produced significant increase in the SCE per cell compared to the control value, whereas NiSO{sub 4} failed to produce any such significant increase. Except NiSO{sub 4}, the soluble forms of NiCH, Ni{sub 3}S{sub 2}, and NiO produced significant cell-cycle delay (as measured by the inhibition of RI) as well as significant inhibition of the MI at respective similar concentrations as mentioned above. Pretreatment of human blood lymphocytes with catalase (H{sub 2}O{sub 2} scavenger), or superoxide dismutase (superoxide anion scavenger), or dimethylthiourea (hydroxyl radical scavenger), or deferoxamine (iron chelator), or N-acetylcysteine (general antioxidant) inhibited NiCH-induced SCE, and changes in RI and MI. This suggests the participation of oxidative stress involving H{sub 2}O{sub 2}, the superoxide anion radical, the hydroxyl radical, and iron in the NiCH-induced genotoxic responses. Cotreatment of NiCH with either verapamil (inhibitor of intracellular calcium ion ([Ca{sup 2+}]{sub i}) movement through plasma membranes), or dantrolene (inhibitor of [Ca{sup 2+}]{sub i} release from sarcoplasmic reticulum), or BAPTA (Ca{sup 2+} chelator) also inhibited the NiCH-induced responses. These results suggest that [Ca{sup 2+}]{sub i} is also implicated in the genotoxicity of NiCH. Overall these data indicate that various types

  20. The variational spiked oscillator

    International Nuclear Information System (INIS)

    Aguilera-Navarro, V.C.; Ullah, N.

    1992-08-01

    A variational analysis of the spiked harmonic oscillator Hamiltonian -d 2 / d x 2 + x 2 + δ/ x 5/2 , δ > 0, is reported in this work. A trial function satisfying Dirichlet boundary conditions is suggested. The results are excellent for a large range of values of the coupling parameter. (author)

  1. Response Features Determining Spike Times

    Directory of Open Access Journals (Sweden)

    Barry J. Richmond

    1999-01-01

    redundant with that carried by the coarse structure. Thus, the existence of precisely timed spike patterns carrying stimulus-related information does not imply control of spike timing at precise time scales.

  2. Spiking neural network for recognizing spatiotemporal sequences of spikes

    International Nuclear Information System (INIS)

    Jin, Dezhe Z.

    2004-01-01

    Sensory neurons in many brain areas spike with precise timing to stimuli with temporal structures, and encode temporally complex stimuli into spatiotemporal spikes. How the downstream neurons read out such neural code is an important unsolved problem. In this paper, we describe a decoding scheme using a spiking recurrent neural network. The network consists of excitatory neurons that form a synfire chain, and two globally inhibitory interneurons of different types that provide delayed feedforward and fast feedback inhibition, respectively. The network signals recognition of a specific spatiotemporal sequence when the last excitatory neuron down the synfire chain spikes, which happens if and only if that sequence was present in the input spike stream. The recognition scheme is invariant to variations in the intervals between input spikes within some range. The computation of the network can be mapped into that of a finite state machine. Our network provides a simple way to decode spatiotemporal spikes with diverse types of neurons

  3. Estimating short-term synaptic plasticity from pre- and postsynaptic spiking

    Science.gov (United States)

    Malyshev, Aleksey; Stevenson, Ian H.

    2017-01-01

    Short-term synaptic plasticity (STP) critically affects the processing of information in neuronal circuits by reversibly changing the effective strength of connections between neurons on time scales from milliseconds to a few seconds. STP is traditionally studied using intracellular recordings of postsynaptic potentials or currents evoked by presynaptic spikes. However, STP also affects the statistics of postsynaptic spikes. Here we present two model-based approaches for estimating synaptic weights and short-term plasticity from pre- and postsynaptic spike observations alone. We extend a generalized linear model (GLM) that predicts postsynaptic spiking as a function of the observed pre- and postsynaptic spikes and allow the connection strength (coupling term in the GLM) to vary as a function of time based on the history of presynaptic spikes. Our first model assumes that STP follows a Tsodyks-Markram description of vesicle depletion and recovery. In a second model, we introduce a functional description of STP where we estimate the coupling term as a biophysically unrestrained function of the presynaptic inter-spike intervals. To validate the models, we test the accuracy of STP estimation using the spiking of pre- and postsynaptic neurons with known synaptic dynamics. We first test our models using the responses of layer 2/3 pyramidal neurons to simulated presynaptic input with different types of STP, and then use simulated spike trains to examine the effects of spike-frequency adaptation, stochastic vesicle release, spike sorting errors, and common input. We find that, using only spike observations, both model-based methods can accurately reconstruct the time-varying synaptic weights of presynaptic inputs for different types of STP. Our models also capture the differences in postsynaptic spike responses to presynaptic spikes following short vs long inter-spike intervals, similar to results reported for thalamocortical connections. These models may thus be useful

  4. Presynaptic calcium signalling in cerebellar mossy fibres

    DEFF Research Database (Denmark)

    Thomsen, Louiza Bohn; Jörntell, Henrik; Midtgaard, Jens

    2010-01-01

    affected burst firing in mossy fibres; this paired-pulse depression was reduced by GABA B antagonists. While our results indicated that a presynaptic rosette electrophysiologically functioned as a unit, topical GABA application showed that calcium signals in the branches of complex rosettes could......Whole-cell recordings were obtained from mossy fibre terminals in adult turtles in order to characterize the basic membrane properties. Calcium imaging of presynaptic calcium signals was carried out in order to analyse calcium dynamics and presynaptic GABA B inhibition. A tetrodotoxin (TTX......)-sensitive fast Na(+) spike faithfully followed repetitive depolarizing pulses with little change in spike duration or amplitude, while a strong outward rectification dominated responses to long-lasting depolarizations. High-threshold calcium spikes were uncovered following addition of potassium channel blockers...

  5. Multiplexed Spike Coding and Adaptation in the Thalamus

    Directory of Open Access Journals (Sweden)

    Rebecca A. Mease

    2017-05-01

    Full Text Available High-frequency “burst” clusters of spikes are a generic output pattern of many neurons. While bursting is a ubiquitous computational feature of different nervous systems across animal species, the encoding of synaptic inputs by bursts is not well understood. We find that bursting neurons in the rodent thalamus employ “multiplexing” to differentially encode low- and high-frequency stimulus features associated with either T-type calcium “low-threshold” or fast sodium spiking events, respectively, and these events adapt differently. Thus, thalamic bursts encode disparate information in three channels: (1 burst size, (2 burst onset time, and (3 precise spike timing within bursts. Strikingly, this latter “intraburst” encoding channel shows millisecond-level feature selectivity and adapts across statistical contexts to maintain stable information encoded per spike. Consequently, calcium events both encode low-frequency stimuli and, in parallel, gate a transient window for high-frequency, adaptive stimulus encoding by sodium spike timing, allowing bursts to efficiently convey fine-scale temporal information.

  6. Store-Operated Calcium Channel and Cancer

    OpenAIRE

    Yang S; Chang WC

    2012-01-01

    The increase of intracellular Ca2+ concentration is an important mechanism that regulates a variety of physiological processes ranging from exocytosis to gene regulation and cell proliferation [1]. Calcium release from intracellular stores (mainly endoplasmic reticulum, ER) or calcium entry through calcium channels can be used by cells to evoke a higher level of cytosolic Ca2+ concentration. In non-excitable cells, a major pathway for Ca2+ influx is via store-operated Ca2+ channels (also know...

  7. Mechanism of store-operated calcium entry

    Indian Academy of Sciences (India)

    Activation of receptors coupled to the phospholipase C/IP3 signalling pathway results in a rapid release of calcium from its intracellular stores, eventually leading to depletion of these stores. Calcium store depletion triggers an influx of extracellular calcium across the plasma membrane, a mechanism known as the ...

  8. Modularized study of human calcium signalling pathway

    Indian Academy of Sciences (India)

    PRAKASH KUMAR

    The idea is used here to break human calcium signalling pathway into simple entities known as ... [Nayak L and De R K 2007 Modularized study of human calcium signalling pathway; J. Biosci. 32 1009–1017] http://www.ias.ac.in/ ..... cellular physiology of intracellular calcium stores; Physiol. Rev. 74 595–636. Bertram R ...

  9. Layer-specific high-frequency spiking in the prefrontal cortex of awake rats

    Directory of Open Access Journals (Sweden)

    Zimbo Saroeni Raymond Maria Boudewijns

    2013-06-01

    Full Text Available Cortical pyramidal neurons show irregular in vivo action potential (AP spiking with high frequency bursts occurring on sparse background activity. Somatic APs can backpropagate from soma into basal and apical dendrites and locally generate dendritic calcium spikes. The critical AP frequency for generation of such dendritic calcium spikes can be very different depending on cell-type or brain area involved. Previously, it was shown in vitro that calcium electrogenesis can also be induced in L(ayer 5 pyramidal neurons of prefrontal cortex (PFC. It remains an open question whether somatic burst spiking and resulting dendritic calcium electrogenesis also occur in morphologically more compact L2/3 pyramidal neurons. Furthermore, it is not known whether critical frequencies that trigger dendritic calcium electrogenesis occur in PFC under awake conditions in vivo. Here, we addressed these issues and found that pyramidal neurons in both PFC L2/3 and L5 in awake rats spike APs in short bursts, but with different probabilities. The critical frequency for calcium electrogenesis in vitro was layer-specific and lower in L5 neurons compared to L2/3. Taking the in vitro critical frequency as predictive measure for dendritic electrogenesis during in vivo spontaneous activity, supracritical bursts in vivo were observed in a larger fraction of L5 neurons compared to L2/3 neurons but with similar incidence within these subpopulations. Together, these results show that in PFC of awake rats, AP spiking occurs at frequencies that are relevant for dendritic calcium electrogenesis and suggest that in awake rat PFC, dendritic calcium electrogenesis may be involved in neuronal computation.

  10. Coronavirus spike-receptor interactions

    NARCIS (Netherlands)

    Mou, H.

    2015-01-01

    Coronaviruses cause important diseases in humans and animals. Coronavirus infection starts with the virus binding with its spike proteins to molecules present on the surface of host cells that act as receptors. This spike-receptor interaction is highly specific and determines the virus’ cell, tissue

  11. Calcium signaling in neurodegeneration

    Directory of Open Access Journals (Sweden)

    Dreses-Werringloer Ute

    2009-05-01

    Full Text Available Abstract Calcium is a key signaling ion involved in many different intracellular and extracellular processes ranging from synaptic activity to cell-cell communication and adhesion. The exact definition at the molecular level of the versatility of this ion has made overwhelming progress in the past several years and has been extensively reviewed. In the brain, calcium is fundamental in the control of synaptic activity and memory formation, a process that leads to the activation of specific calcium-dependent signal transduction pathways and implicates key protein effectors, such as CaMKs, MAPK/ERKs, and CREB. Properly controlled homeostasis of calcium signaling not only supports normal brain physiology but also maintains neuronal integrity and long-term cell survival. Emerging knowledge indicates that calcium homeostasis is not only critical for cell physiology and health, but also, when deregulated, can lead to neurodegeneration via complex and diverse mechanisms involved in selective neuronal impairments and death. The identification of several modulators of calcium homeostasis, such as presenilins and CALHM1, as potential factors involved in the pathogenesis of Alzheimer's disease, provides strong support for a role of calcium in neurodegeneration. These observations represent an important step towards understanding the molecular mechanisms of calcium signaling disturbances observed in different brain diseases such as Alzheimer's, Parkinson's, and Huntington's diseases.

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

    Directory of Open Access Journals (Sweden)

    Dmitry eSamigullin

    2015-01-01

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

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

    Science.gov (United States)

    Samigullin, Dmitry; Fatikhov, Nijaz; Khaziev, Eduard; Skorinkin, Andrey; Nikolsky, Eugeny; Bukharaeva, Ellya

    2014-01-01

    At the frog neuromuscular junction, under physiological conditions, the direct measurement of calcium currents and of the concentration of intracellular calcium buffers-which determine the kinetics of calcium concentration and neurotransmitter release from the nerve terminal-has hitherto been technically impossible. With the aim of quantifying both Ca(2+) currents and the intracellular calcium buffers, we measured fluorescence signals from nerve terminals loaded with the low-affinity calcium dye Magnesium Green or the high-affinity dye Oregon Green BAPTA-1, simultaneously with microelectrode recordings of nerve-action potentials and end-plate currents. The action-potential-induced fluorescence signals in the nerve terminals developed much more slowly than the postsynaptic response. To clarify the reasons for this observation and to define a spatiotemporal profile of intracellular calcium and of the concentration of mobile and fixed calcium buffers, mathematical modeling was employed. The best approximations of the experimental calcium transients for both calcium dyes were obtained when the calcium current had an amplitude of 1.6 ± 0.08 pA and a half-decay time of 1.2 ± 0.06 ms, and when the concentrations of mobile and fixed calcium buffers were 250 ± 13 μM and 8 ± 0.4 mM, respectively. High concentrations of endogenous buffers define the time course of calcium transients after an action potential in the axoplasm, and may modify synaptic plasticity.

  14. Calcium metabolism and cardiovascular function after spaceflight

    Science.gov (United States)

    Hatton, Daniel C.; Yue, Qi; Dierickx, Jacqueline; Roullet, Chantal; Otsuka, Keiichi; Watanabe, Mitsuaki; Coste, Sarah; Roullet, Jean Baptiste; Phanouvang, Thongchan; Orwoll, Eric; hide

    2002-01-01

    To determine the influence of dietary calcium on spaceflight-induced alterations in calcium metabolism and blood pressure (BP), 9-wk-old spontaneously hypertensive rats, fed either high- (2%) or low-calcium (0.02%) diets, were flown on an 18-day shuttle flight. On landing, flight animals had increased ionized calcium (P Basal and thrombin-stimulated platelet free calcium (intracellular calcium concentration) were also reduced (P metabolism (P metabolism are relatively impervious to dietary calcium in the short term, 2) increased ionized calcium did not normalize low-calcium-induced elevations of BP, and 3) parathyroid hormone was paradoxically increased in the high-calcium-fed flight animals after landing.

  15. Spike-Triggered Regression for Synaptic Connectivity Reconstruction in Neuronal Networks.

    Science.gov (United States)

    Zhang, Yaoyu; Xiao, Yanyang; Zhou, Douglas; Cai, David

    2017-01-01

    How neurons are connected in the brain to perform computation is a key issue in neuroscience. Recently, the development of calcium imaging and multi-electrode array techniques have greatly enhanced our ability to measure the firing activities of neuronal populations at single cell level. Meanwhile, the intracellular recording technique is able to measure subthreshold voltage dynamics of a neuron. Our work addresses the issue of how to combine these measurements to reveal the underlying network structure. We propose the spike-triggered regression (STR) method, which employs both the voltage trace and firing activity of the neuronal population to reconstruct the underlying synaptic connectivity. Our numerical study of the conductance-based integrate-and-fire neuronal network shows that only short data of 20 ~ 100 s is required for an accurate recovery of network topology as well as the corresponding coupling strength. Our method can yield an accurate reconstruction of a large neuronal network even in the case of dense connectivity and nearly synchronous dynamics, which many other network reconstruction methods cannot successfully handle. In addition, we point out that, for sparse networks, the STR method can infer coupling strength between each pair of neurons with high accuracy in the absence of the global information of all other neurons.

  16. Wavelet analysis of epileptic spikes

    CERN Document Server

    Latka, M; Kozik, A; West, B J; Latka, Miroslaw; Was, Ziemowit; Kozik, Andrzej; West, Bruce J.

    2003-01-01

    Interictal spikes and sharp waves in human EEG are characteristic signatures of epilepsy. These potentials originate as a result of synchronous, pathological discharge of many neurons. The reliable detection of such potentials has been the long standing problem in EEG analysis, especially after long-term monitoring became common in investigation of epileptic patients. The traditional definition of a spike is based on its amplitude, duration, sharpness, and emergence from its background. However, spike detection systems built solely around this definition are not reliable due to the presence of numerous transients and artifacts. We use wavelet transform to analyze the properties of EEG manifestations of epilepsy. We demonstrate that the behavior of wavelet transform of epileptic spikes across scales can constitute the foundation of a relatively simple yet effective detection algorithm.

  17. Non-Hebbian spike-timing-dependent plasticity in cerebellar circuits

    Science.gov (United States)

    Piochon, Claire; Kruskal, Peter; MacLean, Jason; Hansel, Christian

    2013-01-01

    Spike-timing-dependent plasticity (STDP) provides a cellular implementation of the Hebb postulate, which states that synapses, whose activity repeatedly drives action potential firing in target cells, are potentiated. At glutamatergic synapses onto hippocampal and neocortical pyramidal cells, synaptic activation followed by spike firing in the target cell causes long-term potentiation (LTP)—as predicted by Hebb—whereas excitatory postsynaptic potentials (EPSPs) evoked after a spike elicit long-term depression (LTD)—a phenomenon that was not specifically addressed by Hebb. In both instances the action potential in the postsynaptic target neuron is an instructive signal that is capable of supporting synaptic plasticity. STDP generally relies on the propagation of Na+ action potentials that are initiated in the axon hillhock back into the dendrite, where they cause depolarization and boost local calcium influx. However, recent studies in CA1 hippocampal pyramidal neurons have suggested that local calcium spikes might provide a more efficient trigger for LTP induction than backpropagating action potentials. Dendritic calcium spikes also play a role in an entirely different type of STDP that can be observed in cerebellar Purkinje cells. These neurons lack backpropagating Na+ spikes. Instead, plasticity at parallel fiber (PF) to Purkinje cell synapses depends on the relative timing of PF-EPSPs and activation of the glutamatergic climbing fiber (CF) input that causes dendritic calcium spikes. Thus, the instructive signal in this system is externalized. Importantly when EPSPs are elicited before CF activity, PF-LTD is induced rather than LTP. Thus, STDP in the cerebellum follows a timing rule that is opposite to its hippocampal/neocortical counterparts. Regardless, a common motif in plasticity is that LTD/LTP induction depends on the relative timing of synaptic activity and regenerative dendritic spikes which are driven by the instructive signal. PMID:23335888

  18. A Bayesian approach to modelling heterogeneous calcium responses in cell populations.

    Directory of Open Access Journals (Sweden)

    Agne Tilūnaitė

    2017-10-01

    Full Text Available Calcium responses have been observed as spikes of the whole-cell calcium concentration in numerous cell types and are essential for translating extracellular stimuli into cellular responses. While there are several suggestions for how this encoding is achieved, we still lack a comprehensive theory. To achieve this goal it is necessary to reliably predict the temporal evolution of calcium spike sequences for a given stimulus. Here, we propose a modelling framework that allows us to quantitatively describe the timing of calcium spikes. Using a Bayesian approach, we show that Gaussian processes model calcium spike rates with high fidelity and perform better than standard tools such as peri-stimulus time histograms and kernel smoothing. We employ our modelling concept to analyse calcium spike sequences from dynamically-stimulated HEK293T cells. Under these conditions, different cells often experience diverse stimulus time courses, which is a situation likely to occur in vivo. This single cell variability and the concomitant small number of calcium spikes per cell pose a significant modelling challenge, but we demonstrate that Gaussian processes can successfully describe calcium spike rates in these circumstances. Our results therefore pave the way towards a statistical description of heterogeneous calcium oscillations in a dynamic environment.

  19. Effect of heavy metals on pH buffering capacity and solubility of Ca, Mg, K, and P in non-spiked and heavy metal-spiked soils.

    Science.gov (United States)

    Najafi, Sarvenaz; Jalali, Mohsen

    2016-06-01

    In many parts of the world, soil acidification and heavy metal contamination has become a serious concern due to the adverse effects on chemical properties of soil and crop yield. The aim of this study was to investigate the effect of pH (in the range of 1 to 3 units above and below the native pH of soils) on calcium (Ca), magnesium (Mg), potassium (K), and phosphorus (P) solubility in non-spiked and heavy metal-spiked soil samples. Spiked samples were prepared by cadmium (Cd), copper (Cu), nickel (Ni), and zinc (Zn) as chloride salts and incubating soils for 40 days. The pH buffering capacity (pHBC) of each sample was determined by plotting the amount of H(+) or OH(-) added (mmol kg(-1)) versus the related pH value. The pHBC of soils ranged from 47.1 to 1302.5 mmol kg(-1) for non-spiked samples and from 45.0 to 1187.4 mmol kg(-1) for spiked soil samples. The pHBC values were higher in soil 2 (non-spiked and spiked) which had higher calcium carbonate content. The results indicated the presence of heavy metals in soils generally decreased the solution pH and pHBC values in spiked samples. In general, solubility of Ca, Mg, and K decreased with increasing equilibrium pH of non-spiked and spiked soil samples. In the case of P, increasing the pH to about 7, decreased the solubility in all soils but further increase of pH from 7, enhanced P solubility. The solubility trends and values for Ca, Mg, and K did not differed significantly in non-spiked and spiked samples. But in the case of P, a reduction in solubility was observed in heavy metal-spiked soils. The information obtained in this study can be useful to make better estimation of the effects of soil pollutants on anion and cation solubility from agricultural and environmental viewpoints.

  20. Calcium-activated potassium channels in insect pacemaker neurons as unexpected target site for the novel fumigant dimethyl disulfide.

    Science.gov (United States)

    Gautier, Hélène; Auger, Jacques; Legros, Christian; Lapied, Bruno

    2008-01-01

    Dimethyl disulfide (DMDS), a plant-derived insecticide, is a promising fumigant as a substitute for methyl bromide. To further understand the mode of action of DMDS, we examined its effect on cockroach octopaminergic neurosecretory cells, called dorsal unpaired median (DUM) neurons, using whole-cell patch-clamp technique, calcium imaging and antisense oligonucleotide strategy. At low concentration (1 microM), DMDS modified spontaneous regular spike discharge into clear bursting activity associated with a decrease of the amplitude of the afterhyperpolarization. This effect led us to suspect alterations of calcium-activated potassium currents (IKCa) and [Ca(2+)](i) changes. We showed that DMDS reduced amplitudes of both peak transient and sustained components of the total potassium current. IKCa was confirmed as a target of DMDS by using iberiotoxin, cadmium chloride, and pSlo antisense oligonucleotide. In addition, we showed that DMDS induced [Ca(2+)](i) rise in Fura-2-loaded DUM neurons. Using calcium-free solution, and (R,S)-(3,4-dihydro-6,7-dimethoxy-isoquinoline-1-yl)-2-phenyl-N,N-di-[2-(2,3,4-trimethoxy-phenyl)ethyl]-acetamide (LOE 908) [an inhibitor of transient receptor potential (TRP)gamma], we demonstrated that TRPgamma initiated calcium influx. By contrast, omega-conotoxin GVIA (an inhibitor of N-type high-voltage-activated calcium channels), did not affect the DMDS-induced [Ca(2+)](i) rise. Finally, the participation of the calcium-induced calcium release mechanism was investigated using thapsigargin, caffeine, and ryanodine. Our study revealed that DMDS-induced elevation in [Ca(2+)](i) modulated IKCa in an unexpected bell-shaped manner via intracellular calcium. In conclusion, DMDS affects multiple targets, which could be an effective way to improve pest control efficacy of fumigation.

  1. Facilitation of plateau potentials in turtle motoneurones by a pathway dependent on calcium and calmodulin

    DEFF Research Database (Denmark)

    Perrier, J F; Mejia-Gervacio, S; Hounsgaard, J

    2000-01-01

    1. The involvement of intracellular calcium and calmodulin in the modulation of plateau potentials in motoneurones was investigated using intracellular recordings from a spinal cord slice preparation. 2. Chelation of intracellular calcium with BAPTA-AM or inactivation of calmodulin with W-7 or tr...

  2. Structure-activity relationship study and discovery of indazole 3-carboxamides as calcium-release activated calcium channel blockers

    OpenAIRE

    Bai, Sha; Nagai, Masazumi; Koerner, Steffi K.; Veves, Aristidis; Sun, Lijun

    2016-01-01

    Aberrant activation of mast cells contributes to the development of numerous diseases including cancer, autoimmune disorders, as well as diabetes and its complications. The influx of extracellular calcium via the highly calcium selective calcium-release activated calcium (CRAC) channel controls mast cell functions. Intracellular calcium homeostasis in mast cells can be maintained via the modulation of the CRAC channel, representing a critical point for therapeutic interventions. We describe t...

  3. Calcium signals in olfactory neurons.

    Science.gov (United States)

    Tareilus, E; Noé, J; Breer, H

    1995-11-09

    Laser scanning confocal microscopy in combination with the fluorescent calcium indicators Fluo-3 and Fura-Red was employed to estimate the intracellular concentration of free calcium ions in individual olfactory receptor neurons and to monitor temporal and spatial changes in the Ca(2+)-level upon stimulation. The chemosensory cells responded to odorants with a significant increase in the calcium concentration, preferentially in the dendritic knob. Applying various stimulation paradigma, it was found that in a population of isolated cells, subsets of receptor neurons display distinct patterns of responsiveness.

  4. Calcium chromate process related investigations

    International Nuclear Information System (INIS)

    Dillard, B.M.

    1979-01-01

    A pilot plant for production of calcium chromate has been scaled up to a small production facility at the General Electric Neutron Devices Department. In preparation for this scale-up, the process and final product were studied in order to evaluate problems not considered previously. The variables and processes studied included: (1) the determination of optimum drying temperature and time for product analysis; (2) the effect of the grade of lime used as the precipitating agent on the purity of the calcium chromate; (3) product purity when calcium chromate is precipitated by the addition of ammonium chromate to slaked lime; (4) the reagents best suited for cleaning calcium chromate spills; and (5) methods for determining hydroxide ion concentration in calcium chromate. The optimum drying time for the product before analysis is four hours at 600 0 C. Gases evolved at various temperatures during the drying process were carbon dioxide and water vapor. Technical grade lime produced calcium chromate of the highest purity. Both nitric and acetic acids were efficient dissolvers of calcium chromate spills. Direct titration of hydroxide ion with sulfuric acid gave an average recovery of 93% for samples spiked with calcium hydroxide. 1 figure, 17 tables

  5. Neural spike sorting using iterative ICA and a deflation-based approach.

    Science.gov (United States)

    Tiganj, Z; Mboup, M

    2012-12-01

    We propose a spike sorting method for multi-channel recordings. When applied in neural recordings, the performance of the independent component analysis (ICA) algorithm is known to be limited, since the number of recording sites is much lower than the number of neurons. The proposed method uses an iterative application of ICA and a deflation technique in two nested loops. In each iteration of the external loop, the spiking activity of one neuron is singled out and then deflated from the recordings. The internal loop implements a sequence of ICA and sorting for removing the noise and all the spikes that are not fired by the targeted neuron. Then a final step is appended to the two nested loops in order to separate simultaneously fired spikes. We solve this problem by taking all possible pairs of the sorted neurons and apply ICA only on the segments of the signal during which at least one of the neurons in a given pair was active. We validate the performance of the proposed method on simulated recordings, but also on a specific type of real recordings: simultaneous extracellular-intracellular. We quantify the sorting results on the extracellular recordings for the spikes that come from the neurons recorded intracellularly. The results suggest that the proposed solution significantly improves the performance of ICA in spike sorting.

  6. Subcellular distribution of calcium during spermatogenesis of zebrafish, Danio rerio.

    Science.gov (United States)

    Golpour, Amin; Pšenička, Martin; Niksirat, Hamid

    2017-08-01

    Calcium plays a variety of vital regulatory functions in many physiological and biochemical events in the cell. The aim of this study was to describe the ultrastructural distribution of calcium during different developmental stages of spermatogenesis in a model organism, the zebrafish (Danio rerio), using a combined oxalate-pyroantimonate technique. Samples were treated by potassium oxalate and potassium pyroantimonate during two fixation stages and examined using transmission electron microscopy to detect electron dense intracellular calcium. The subcellular distribution of intracellular calcium was characterized in spermatogonium, spermatocyte, spermatid, and spermatozoon stages. The area which is covered by intracellular calcium in different stages was quantified and compared using software. Isolated calcium deposits were mainly detectable in the cytoplasm and the nucleus of the spermatogonium and spermatocyte. In the spermatid, calcium was partially localized in the cytoplasm as isolated deposits. However, most calcium was transformed from isolated deposits into an unbound pool (free calcium) within the nucleus of the spermatid and the spermatozoon. Interestingly, in the spermatozoon, calcium was mainly localized in a form of an unbound pool which was detectable as an electron-dense mass within the nucleus. Also, sporadic calcium deposits were scattered in the midpiece and flagellum. The proportional area which was covered by intracellular calcium increased significantly from early to late stages of spermatogenesis. The extent of the area which was covered by intracellular calcium in the spermatozoon was the highest compared to earlier stages. Calcium deposits were also observed in the somatic cells (Sertoli, myoid, Leydig) of zebrafish testis. The notable changes in the distribution of intracellular calcium of germ cells during different developmental stages of zebrafish spermatogenesis suggest its different homeostasis and physiological functions during the

  7. Training spiking neural networks to associate spatio-temporal input-output spike patterns

    OpenAIRE

    Mohemmed, A; Schliebs, S; Matsuda, S; Kasabov, N

    2013-01-01

    In a previous work (Mohemmed et al., Method for training a spiking neuron to associate input–output spike trains) [1] we have proposed a supervised learning algorithm based on temporal coding to train a spiking neuron to associate input spatiotemporal spike patterns to desired output spike patterns. The algorithm is based on the conversion of spike trains into analogue signals and the application of the Widrow–Hoff learning rule. In this paper we present a mathematical formulation of the prop...

  8. Intracellular ion channels and cancer

    Directory of Open Access Journals (Sweden)

    Luigi eLeanza

    2013-09-01

    Full Text Available Several types of channels play a role in the maintenance of ion homeostasis in subcellular organelles including endoplasmatic reticulum, nucleus, lysosome, endosome and mitochondria. Here we give a brief overview of the contribution of various mitochondrial and other organellar channels to cancer cell proliferation or death. Much attention is focused on channels involved in intracellular calcium signaling and on ion fluxes in the ATP-producing organelle mitochondria. Mitochondrial K+ channels (Ca2+-dependent BKCa and IKCa, ATP-dependent KATP, Kv1.3, two-pore TWIK-related Acid-Sensitive K+ channel-3 (TASK-3, Ca2+ uniporter MCU, Mg2+-permeable Mrs2, anion channels (voltage-dependent chloride channel VDAC, intracellular chloride channel CLIC and the Permeability Transition Pore (MPTP contribute importantly to the regulation of function in this organelle. Since mitochondria play a central role in apoptosis, modulation of their ion channels by pharmacological means may lead to death of cancer cells. The nuclear potassium channel Kv10.1 and the nuclear chloride channel CLIC4 as well as the endoplasmatic reticulum (ER-located inositol 1,4,5-trisphosphate (IP3 receptor, the ER-located Ca2+ depletion sensor STIM1 (stromal interaction molecule 1, a component of the store-operated Ca2+ channel and the ER-resident TRPM8 are also mentioned. Furthermore, pharmacological tools affecting organellar channels and modulating cancer cell survival are discussed. The channels described in this review are summarized on Figure 1. Overall, the view is emerging that intracellular ion channels may represent a promising target for cancer treatment.

  9. Energetics based spike generation of a single neuron: simulation results and analysis

    Directory of Open Access Journals (Sweden)

    Nagarajan eVenkateswaran

    2012-02-01

    Full Text Available Existing current based models that capture spike activity, though useful in studying information processing capabilities of neurons, fail to throw light on their internal functioning. It is imperative to develop a model that captures the spike train of a neuron as a function of its intra cellular parameters for non-invasive diagnosis of diseased neurons. This is the first ever article to present such an integrated model that quantifies the inter-dependency between spike activity and intra cellular energetics. The generated spike trains from our integrated model will throw greater light on the intra-cellular energetics than existing current models. Now, an abnormality in the spike of a diseased neuron can be linked and hence effectively analyzed at the energetics level. The spectral analysis of the generated spike trains in a time-frequency domain will help identify abnormalities in the internals of a neuron. As a case study, the parameters of our model are tuned for Alzheimer disease and its resultant spike trains are studied and presented.

  10. Models of calcium signalling

    CERN Document Server

    Dupont, Geneviève; Kirk, Vivien; Sneyd, James

    2016-01-01

    This book discusses the ways in which mathematical, computational, and modelling methods can be used to help understand the dynamics of intracellular calcium. The concentration of free intracellular calcium is vital for controlling a wide range of cellular processes, and is thus of great physiological importance. However, because of the complex ways in which the calcium concentration varies, it is also of great mathematical interest.This book presents the general modelling theory as well as a large number of specific case examples, to show how mathematical modelling can interact with experimental approaches, in an interdisciplinary and multifaceted approach to the study of an important physiological control mechanism. Geneviève Dupont is FNRS Research Director at the Unit of Theoretical Chronobiology of the Université Libre de Bruxelles;Martin Falcke is head of the Mathematical Cell Physiology group at the Max Delbrück Center for Molecular Medicine, Berlin;Vivien Kirk is an Associate Professor in the Depar...

  11. Neuronal coding and spiking randomness

    Czech Academy of Sciences Publication Activity Database

    Košťál, Lubomír; Lánský, Petr; Rospars, J. P.

    2007-01-01

    Roč. 26, č. 10 (2007), s. 2693-2988 ISSN 0953-816X R&D Projects: GA MŠk(CZ) LC554; GA AV ČR(CZ) 1ET400110401; GA AV ČR(CZ) KJB100110701 Grant - others:ECO-NET(FR) 112644PF Institutional research plan: CEZ:AV0Z50110509 Keywords : spike train * variability * neurovědy Subject RIV: FH - Neurology Impact factor: 3.673, year: 2007

  12. Prospective Coding by Spiking Neurons.

    Directory of Open Access Journals (Sweden)

    Johanni Brea

    2016-06-01

    Full Text Available Animals learn to make predictions, such as associating the sound of a bell with upcoming feeding or predicting a movement that a motor command is eliciting. How predictions are realized on the neuronal level and what plasticity rule underlies their learning is not well understood. Here we propose a biologically plausible synaptic plasticity rule to learn predictions on a single neuron level on a timescale of seconds. The learning rule allows a spiking two-compartment neuron to match its current firing rate to its own expected future discounted firing rate. For instance, if an originally neutral event is repeatedly followed by an event that elevates the firing rate of a neuron, the originally neutral event will eventually also elevate the neuron's firing rate. The plasticity rule is a form of spike timing dependent plasticity in which a presynaptic spike followed by a postsynaptic spike leads to potentiation. Even if the plasticity window has a width of 20 milliseconds, associations on the time scale of seconds can be learned. We illustrate prospective coding with three examples: learning to predict a time varying input, learning to predict the next stimulus in a delayed paired-associate task and learning with a recurrent network to reproduce a temporally compressed version of a sequence. We discuss the potential role of the learning mechanism in classical trace conditioning. In the special case that the signal to be predicted encodes reward, the neuron learns to predict the discounted future reward and learning is closely related to the temporal difference learning algorithm TD(λ.

  13. Khz (fusion of Ganoderma lucidum and Polyporus umbellatus mycelia induces apoptosis by increasing intracellular calcium levels and activating JNK and NADPH oxidase-dependent generation of reactive oxygen species.

    Directory of Open Access Journals (Sweden)

    Tae Hwan Kim

    Full Text Available Khz is a compound derived from the fusion of Ganoderma lucidum and Polyporus umbellatus mycelia that inhibits the growth of cancer cells. The results of the present study show that Khz induced apoptosis preferentially in transformed cells and had only minimal effects on non-transformed cells. Furthermore, Khz induced apoptosis by increasing the intracellular Ca(2+ concentration ([Ca(2+](i and activating JNK to generate reactive oxygen species (ROS via NADPH oxidase and the mitochondria. Khz-induced apoptosis was caspase-dependent and occurred via a mitochondrial pathway. ROS generation by NADPH oxidase was critical for Khz-induced apoptosis, and although mitochondrial ROS production was also required, it appeared to occur secondary to ROS generation by NADPH oxidase. Activation of NADPH oxidase was demonstrated by the translocation of regulatory subunits p47(phox and p67(phox to the cell membrane and was necessary for ROS generation by Khz. Khz triggered a rapid and sustained increase in [Ca(2+](i, which activated JNK. JNK plays a key role in the activation of NADPH oxidase because inhibition of its expression or activity abrogated membrane translocation of the p47(phox and p67(phox subunits and ROS generation. In summary, these data indicate that Khz preferentially induces apoptosis in cancer cells, and the signaling mechanisms involve an increase in [Ca(2+](i, JNK activation, and ROS generation via NADPH oxidase and mitochondria.

  14. iSpike: a spiking neural interface for the iCub robot

    International Nuclear Information System (INIS)

    Gamez, D; Fidjeland, A K; Lazdins, E

    2012-01-01

    This paper presents iSpike: a C++ library that interfaces between spiking neural network simulators and the iCub humanoid robot. It uses a biologically inspired approach to convert the robot’s sensory information into spikes that are passed to the neural network simulator, and it decodes output spikes from the network into motor signals that are sent to control the robot. Applications of iSpike range from embodied models of the brain to the development of intelligent robots using biologically inspired spiking neural networks. iSpike is an open source library that is available for free download under the terms of the GPL. (paper)

  15. Information transmission with spiking Bayesian neurons

    International Nuclear Information System (INIS)

    Lochmann, Timm; Deneve, Sophie

    2008-01-01

    Spike trains of cortical neurons resulting from repeatedpresentations of a stimulus are variable and exhibit Poisson-like statistics. Many models of neural coding therefore assumed that sensory information is contained in instantaneous firing rates, not spike times. Here, we ask how much information about time-varying stimuli can be transmitted by spiking neurons with such input and output variability. In particular, does this variability imply spike generation to be intrinsically stochastic? We consider a model neuron that estimates optimally the current state of a time-varying binary variable (e.g. presence of a stimulus) by integrating incoming spikes. The unit signals its current estimate to other units with spikes whenever the estimate increased by a fixed amount. As shown previously, this computation results in integrate and fire dynamics with Poisson-like output spike trains. This output variability is entirely due to the stochastic input rather than noisy spike generation. As a result such a deterministic neuron can transmit most of the information about the time varying stimulus. This contrasts with a standard model of sensory neurons, the linear-nonlinear Poisson (LNP) model which assumes that most variability in output spike trains is due to stochastic spike generation. Although it yields the same firing statistics, we found that such noisy firing results in the loss of most information. Finally, we use this framework to compare potential effects of top-down attention versus bottom-up saliency on information transfer with spiking neurons

  16. Feature Representations for Neuromorphic Audio Spike Streams.

    Science.gov (United States)

    Anumula, Jithendar; Neil, Daniel; Delbruck, Tobi; Liu, Shih-Chii

    2018-01-01

    Event-driven neuromorphic spiking sensors such as the silicon retina and the silicon cochlea encode the external sensory stimuli as asynchronous streams of spikes across different channels or pixels. Combining state-of-art deep neural networks with the asynchronous outputs of these sensors has produced encouraging results on some datasets but remains challenging. While the lack of effective spiking networks to process the spike streams is one reason, the other reason is that the pre-processing methods required to convert the spike streams to frame-based features needed for the deep networks still require further investigation. This work investigates the effectiveness of synchronous and asynchronous frame-based features generated using spike count and constant event binning in combination with the use of a recurrent neural network for solving a classification task using N-TIDIGITS18 dataset. This spike-based dataset consists of recordings from the Dynamic Audio Sensor, a spiking silicon cochlea sensor, in response to the TIDIGITS audio dataset. We also propose a new pre-processing method which applies an exponential kernel on the output cochlea spikes so that the interspike timing information is better preserved. The results from the N-TIDIGITS18 dataset show that the exponential features perform better than the spike count features, with over 91% accuracy on the digit classification task. This accuracy corresponds to an improvement of at least 2.5% over the use of spike count features, establishing a new state of the art for this dataset.

  17. Ca2+ Binding/Permeation via Calcium Channel, CaV1.1, Regulates the Intracellular Distribution of the Fatty Acid Transport Protein, CD36, and Fatty Acid Metabolism.

    Science.gov (United States)

    Georgiou, Dimitra K; Dagnino-Acosta, Adan; Lee, Chang Seok; Griffin, Deric M; Wang, Hui; Lagor, William R; Pautler, Robia G; Dirksen, Robert T; Hamilton, Susan L

    2015-09-25

    Ca(2+) permeation and/or binding to the skeletal muscle L-type Ca(2+) channel (CaV1.1) facilitates activation of Ca(2+)/calmodulin kinase type II (CaMKII) and Ca(2+) store refilling to reduce muscle fatigue and atrophy (Lee, C. S., Dagnino-Acosta, A., Yarotskyy, V., Hanna, A., Lyfenko, A., Knoblauch, M., Georgiou, D. K., Poché, R. A., Swank, M. W., Long, C., Ismailov, I. I., Lanner, J., Tran, T., Dong, K., Rodney, G. G., Dickinson, M. E., Beeton, C., Zhang, P., Dirksen, R. T., and Hamilton, S. L. (2015) Skelet. Muscle 5, 4). Mice with a mutation (E1014K) in the Cacna1s (α1 subunit of CaV1.1) gene that abolishes Ca(2+) binding within the CaV1.1 pore gain more body weight and fat on a chow diet than control mice, without changes in food intake or activity, suggesting that CaV1.1-mediated CaMKII activation impacts muscle energy expenditure. We delineate a pathway (Cav1.1→ CaMKII→ NOS) in normal skeletal muscle that regulates the intracellular distribution of the fatty acid transport protein, CD36, altering fatty acid metabolism. The consequences of blocking this pathway are decreased mitochondrial β-oxidation and decreased energy expenditure. This study delineates a previously uncharacterized CaV1.1-mediated pathway that regulates energy utilization in skeletal muscle. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  18. Visually Evoked Spiking Evolves While Spontaneous Ongoing Dynamics Persist

    DEFF Research Database (Denmark)

    Huys, Raoul; Jirsa, Viktor K; Darokhan, Ziauddin

    2016-01-01

    by evoked spiking. This study of laminar recordings of spontaneous spiking and visually evoked spiking of neurons in the ferret primary visual cortex shows that the spiking dynamics does not change: the spontaneous spiking as well as evoked spiking is controlled by a stable and persisting fixed point...

  19. Khz-cp (crude polysaccharide extract obtained from the fusion of Ganoderma lucidum and Polyporus umbellatus mycelia) induces apoptosis by increasing intracellular calcium levels and activating P38 and NADPH oxidase-dependent generation of reactive oxygen species in SNU-1 cells.

    Science.gov (United States)

    Kim, Tae Hwan; Kim, Ju Sung; Kim, Zoo Haye; Huang, Ren Bin; Chae, Young Lye; Wang, Ren Sheng

    2014-07-10

    Khz-cp is a crude polysaccharide extract that is obtained after nuclear fusion in Ganoderma lucidum and Polyporus umbellatus mycelia (Khz). It inhibits the growth of cancer cells. Khz-cp was extracted by solvent extraction. The anti-proliferative activity of Khz-cp was confirmed by using Annexin-V/PI-flow cytometry analysis. Intracellular calcium increase and measurement of intracellular reactive oxygen species (ROS) were performed by using flow cytometry and inverted microscope. SNU-1 cells were treated with p38, Bcl-2 and Nox family siRNA. siRNA transfected cells was employed to investigate the expression of apoptotic, growth and survival genes in SNU-1 cells. Western blot analysis was performed to confirm the expression of the genes. In the present study, Khz-cp induced apoptosis preferentially in transformed cells and had only minimal effects on non-transformed cells. Furthermore, Khz-cp was found to induce apoptosis by increasing the intracellular Ca2+ concentration ([Ca2+]i) and activating P38 to generate reactive oxygen species (ROS) via NADPH oxidase and the mitochondria. Khz-cp-induced apoptosis was caspase dependent and occurred via a mitochondrial pathway. ROS generation by NADPH oxidase was critical for Khz-cp-induced apoptosis, and although mitochondrial ROS production was also required, it appeared to occur secondary to ROS generation by NADPH oxidase. Activation of NADPH oxidase was shown by the translocation of the regulatory subunits p47phox and p67phox to the cell membrane and was necessary for ROS generation by Khz-cp. Khz-cp triggered a rapid and sustained increase in [Ca2+]i that activated P38. P38 was considered to play a key role in the activation of NADPH oxidase because inhibition of its expression or activity abrogated membrane translocation of the p47phox and p67phox subunits and ROS generation. In summary, these data indicate that Khz-cp preferentially induces apoptosis in cancer cells and that the signaling mechanisms involve an

  20. The dynamic relationship between cerebellar Purkinje cell simple spikes and the spikelet number of complex spikes.

    Science.gov (United States)

    Burroughs, Amelia; Wise, Andrew K; Xiao, Jianqiang; Houghton, Conor; Tang, Tianyu; Suh, Colleen Y; Lang, Eric J; Apps, Richard; Cerminara, Nadia L

    2017-01-01

    Purkinje cells are the sole output of the cerebellar cortex and fire two distinct types of action potential: simple spikes and complex spikes. Previous studies have mainly considered complex spikes as unitary events, even though the waveform is composed of varying numbers of spikelets. The extent to which differences in spikelet number affect simple spike activity (and vice versa) remains unclear. We found that complex spikes with greater numbers of spikelets are preceded by higher simple spike firing rates but, following the complex spike, simple spikes are reduced in a manner that is graded with spikelet number. This dynamic interaction has important implications for cerebellar information processing, and suggests that complex spike spikelet number may maintain Purkinje cells within their operational range. Purkinje cells are central to cerebellar function because they form the sole output of the cerebellar cortex. They exhibit two distinct types of action potential: simple spikes and complex spikes. It is widely accepted that interaction between these two types of impulse is central to cerebellar cortical information processing. Previous investigations of the interactions between simple spikes and complex spikes have mainly considered complex spikes as unitary events. However, complex spikes are composed of an initial large spike followed by a number of secondary components, termed spikelets. The number of spikelets within individual complex spikes is highly variable and the extent to which differences in complex spike spikelet number affects simple spike activity (and vice versa) remains poorly understood. In anaesthetized adult rats, we have found that Purkinje cells recorded from the posterior lobe vermis and hemisphere have high simple spike firing frequencies that precede complex spikes with greater numbers of spikelets. This finding was also evident in a small sample of Purkinje cells recorded from the posterior lobe hemisphere in awake cats. In addition

  1. Intracellular recording from a spider vibration receptor.

    Science.gov (United States)

    Gingl, Ewald; Burger, Anna-M; Barth, Friedrich G

    2006-05-01

    The present study introduces a new preparation of a spider vibration receptor that allows intracellular recording of responses to natural mechanical or electrical stimulation of the associated mechanoreceptor cells. The spider vibration receptor is a lyriform slit sense organ made up of 21 cuticular slits located on the distal end of the metatarsus of each walking leg. The organ is stimulated when the tarsus receives substrate vibrations, which it transmits to the organ's cuticular structures, reducing the displacement to about one tenth due to geometrical reasons. Current clamp recording was used to record action potentials generated by electrical or mechanical stimuli. Square pulse stimulation identified two groups of sensory cells, the first being single-spike cells which generated only one or two action potentials and the second being multi-spike cells which produced bursts of action potentials. When the more natural mechanical sinusoidal stimulation was applied, differences in adaptation rate between the two cell types remained. In agreement with prior extracellular recordings, both cell types showed a decrease in the threshold tarsus deflection with increasing stimulus frequency. Off-responses to mechanical stimuli have also been seen in the metatarsal organ for the first time.

  2. Robust spike-train learning in spike-event based weight update.

    Science.gov (United States)

    Shrestha, Sumit Bam; Song, Qing

    2017-12-01

    Supervised learning algorithms in a spiking neural network either learn a spike-train pattern for a single neuron receiving input spike-train from multiple input synapses or learn to output the first spike time in a feedforward network setting. In this paper, we build upon spike-event based weight update strategy to learn continuous spike-train in a spiking neural network with a hidden layer using a dead zone on-off based adaptive learning rate rule which ensures convergence of the learning process in the sense of weight convergence and robustness of the learning process to external disturbances. Based on different benchmark problems, we compare this new method with other relevant spike-train learning algorithms. The results show that the speed of learning is much improved and the rate of successful learning is also greatly improved. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Spiking Neuron Network Helmholtz Machine

    Directory of Open Access Journals (Sweden)

    Pavel eSountsov

    2015-04-01

    Full Text Available An increasing amount of behavioral and neurophysiological data suggests that the brain performs optimal (or near-optimal probabilistic inference and learning during perception and other tasks. Although many machine learning algorithms exist that perform inference and learning in an optimal way, the complete description of how one of those algorithms (or a novel algorithm can be implemented in the brain is currently incomplete. There have been many proposed solutions that address how neurons can perform optimal inference but the question of how synaptic plasticity can implement optimal learning is rarely addressed. This paper aims to unify the two fields of probabilistic inference and synaptic plasticity by using a neuronal network of realistic model spiking neurons to implement a well studied computational model called the Helmholtz Machine. The Helmholtz Machine is amenable to neural implementation as the algorithm it uses to learn its parameters, called the wake-sleep algorithm, uses a local delta learning rule. Our spiking-neuron network implements both the delta rule and a small example of a Helmholtz machine. This neuronal network can learn an internal model of continuous-valued training data sets without supervision. The network can also perform inference on the learned internal models. We show how various biophysical features of the neural implementation constrain the parameters of the wake-sleep algorithm, such as the duration of the wake and sleep phases of learning and the minimal sample duration. We examine the deviations from optimal performance and tie them to the properties of the synaptic plasticity rule.

  4. The Second Spiking Threshold: Dynamics of Laminar Network Spiking in the Visual Cortex

    DEFF Research Database (Denmark)

    Forsberg, Lars E.; Bonde, Lars H.; Harvey, Michael A.

    2016-01-01

    visually evoked spiking driven by sharp transients. Here we examine whether this second threshold exists outside the granular layer and examine details of transitions between spiking states in ferrets exposed to moving objects. We found the second threshold, separating spiking states evoked by stationary...

  5. Cortico-Striatal Spike-Timing Dependent Plasticity After Activation of Subcortical Pathways

    OpenAIRE

    Schulz, Jan M.; Redgrave, Peter; Reynolds, John N. J.

    2010-01-01

    Cortico-striatal spike-timing dependent plasticity (STDP) is modulated by dopamine in vitro. The present study investigated STDP in vivo using alternative procedures for modulating dopaminergic inputs. Postsynaptic potentials (PSP) were evoked in intracellularly recorded spiny neurons by electrical stimulation of the contralateral motor cortex. PSPs often consisted of up to three distinct components, likely representing distinct cortico-striatal pathways. After baseline recording, bicucullin...

  6. Understanding calcium dynamics experiments and theory

    CERN Document Server

    Malchow, Dieter

    2003-01-01

    Intracellular Calcium is an important messenger in living cells. Calcium dynamics display complex temporal and spatial structures created by the concentration patterns which are characteristic for a nonlinear system operating far from thermodynamic equilibrium. Written as a set of tutorial reviews on both experimental facts and theoretical modelling, this volume is intended as an introduction and modern reference in the field for graduate students and researchers in biophysics, biochemistry and applied mathematics.

  7. Cortico-striatal spike-timing dependent plasticity after activation of subcortical pathways

    Directory of Open Access Journals (Sweden)

    Jan M Schulz

    2010-07-01

    Full Text Available Cortico-striatal spike-timing dependent plasticity (STDP is modulated by dopamine in vitro. The present study investigated STDP in vivo using alternative procedures for modulating dopaminergic inputs. Postsynaptic potentials (PSP were evoked in intracellularly recorded spiny neurons by electrical stimulation of the contralateral motor cortex. PSPs often consisted of up to three distinct components, likely representing distinct cortico-striatal pathways. After baseline recording, bicuculline (BIC was ejected into the superior colliculus (SC to disinhibit visual pathways to the dopamine cells and striatum. Repetitive cortical stimulation (~60; 0.2 Hz was then paired with postsynaptic spike discharge induced by an intracellular current pulse, with each pairing followed 250 ms later by a light flash to the contralateral eye (n=13. Changes in PSPs, measured as the maximal slope normalised to 5 min pre, ranged from potentiation (~120% to depression (~80%. The determining factor was the relative timing between PSP components and spike: PSP components coinciding or closely following the spike tended towards potentiation, whereas PSP components preceding the spike were depressed. Importantly, STDP was only seen in experiments with successful BIC-mediated disinhibition (n=10. Cortico-striatal high-frequency stimulation (50 pulses at 100 Hz followed 100 ms later by a light flash did not induce more robust synaptic plasticity (n=9. However, an elevated post-light spike rate correlated with depression across plasticity protocols (R2=0.55, p=0.009, n=11 active neurons. These results confirm that the direction of cortico-striatal plasticity is determined by the timing of pre- and postsynaptic activity and that synaptic modification is dependent on the activation of additional subcortical inputs.

  8. Localization of calcium changes in stimulated rat mast cells.

    Science.gov (United States)

    Horoyan, M; Soler, M; Benoliel, A M; Fraterno, M; Passerel, M; Subra, H; Martin, J M; Bongrand, P; Foa, C

    1992-01-01

    We studied intracellular free, bound, and sequestered calcium in rat mast cells after various stimulations. The use of a fluorescent probe combined with digitized imaging on individual living cells demonstrated transient increases of free Ca2+ in the micromolar range. The use of histochemical techniques (K pyroantimonate and anhydrous fixation), together with X-ray microanalysis, energy electron-loss spectroscopy, and electron spectroscopic imaging, revealed large amounts of stored calcium within the cells (in the millimolar range). Chelation experiments and stimulations enabled us to identify at least two pools of bound calcium which exhibited different dynamic behaviors. Stimulation in the presence of EGTA did not modify calcium from granules, granule membranes, and heterochromatin, whereas it decreased calcium from other cell compartments. Stimulation triggered variations in the amount of bound calcium but they did not parallel free calcium movements. Hence, whereas free calcium is implicated in exocytosis, bound calcium may be involved in altogether different cell functions.

  9. Linking investment spikes and productivity growth

    NARCIS (Netherlands)

    Geylani, P.C.; Stefanou, S.E.

    2013-01-01

    We investigate the relationship between productivity growth and investment spikes using Census Bureau’s plant-level dataset for the U.S. food manufacturing industry. There are differences in productivity growth and investment spike patterns across different sub-industries and food manufacturing

  10. Intracellular Renin Disrupts Chemical Communication between Heart Cells. Pathophysiological Implications.

    Science.gov (United States)

    De Mello, Walmor C

    2014-01-01

    HighlightsIntracellular renin disrupts chemical communication in the heartAngiotensinogen enhances the effect of reninIntracellular enalaprilat reduces significantly the effect of reninIntracellular renin increases the inward calcium currentHarmful versus beneficial effect during myocardial infarction The influence of intracellular renin on the process of chemical communication between cardiac cells was investigated in cell pairs isolated from the left ventricle of adult Wistar Kyoto rats. The enzyme together with Lucifer yellow CH was dialyzed into one cell of the pair using the whole cell clamp technique. The diffusion of the dye in the dialyzed and in non-dialyzed cell was followed by measuring the intensity of fluorescence in both cells as a function of time. The results indicated that; (1) under normal conditions, Lucifer Yellow flows from cell to cell through gap junctions; (2) the intracellular dialysis of renin (100 nM) disrupts chemical communication - an effect enhanced by simultaneous administration of angiotensinogen (100 nM); (3) enalaprilat (10(-9) M) administered to the cytosol together with renin reduced drastically the uncoupling action of the enzyme; (4) aliskiren (10(-8) M) inhibited the effect of renin on chemical communication; (5) the possible role of intracellular renin independently of angiotensin II (Ang II) was evaluated including the increase of the inward calcium current elicited by the enzyme and the possible role of oxidative stress on the disruption of cell communication; (6) the possible harmful versus the beneficial effect of intracellular renin during myocardial infarction was discussed; (7) the present results indicate that intracellular renin due to internalization or in situ synthesis causes a severe impairment of chemical communication in the heart resulting in derangement of metabolic cooperation with serious consequences for heart function.

  11. Stochastic Variational Learning in Recurrent Spiking Networks

    Directory of Open Access Journals (Sweden)

    Danilo eJimenez Rezende

    2014-04-01

    Full Text Available The ability to learn and perform statistical inference with biologically plausible recurrent network of spiking neurons is an important step towards understanding perception and reasoning. Here we derive and investigate a new learning rule for recurrent spiking networks with hidden neurons, combining principles from variational learning and reinforcement learning. Our network defines a generative model over spike train histories and the derived learning rule has the form of a local Spike Timing Dependent Plasticity rule modulated by global factors (neuromodulators conveying information about ``novelty on a statistically rigorous ground.Simulations show that our model is able to learn bothstationary and non-stationary patterns of spike trains.We also propose one experiment that could potentially be performed with animals in order to test the dynamics of the predicted novelty signal.

  12. Calcium antagonist induced vasodilation in peripheral, coronary and cerebral vasculature as important factors in the treatment of elderly hypertensives

    OpenAIRE

    Erne, P.; Conen, D.; Kiowski, W.; Bolli, P.; Müller, F. B.; Bühler, F. R.

    2017-01-01

    Increased arteriolar tone is the pathophysiological hallmark of essential hypertension and is determined by the intracellular free calcium concentration in the vascular smooth muscle cell. Calcium influx is an important determinant of vasoconstriction and excess calcium influx-dependent vasoconstriction has been shown by plethysmographical studies in patients with essential hypertension. Calcium antagonists acutely lower BP by reducing calcium influx, calcium concentration and peripheral resi...

  13. The Effect of Calcium Treatment on Pitting Corrosion of Type 316L Austenitic Stainless steel

    International Nuclear Information System (INIS)

    Lee, Yong Heon; LeeSoo Chan; Kim, Yong Hwan; Kim, Hee San

    2001-01-01

    Pitting in chloride containing aqueous solution occurs mainly on manganese sulphide. Adding a slight amount of Ca as an alloying element prevents the MnS formation, since Ca is a stronger sulphide former than Mn. In this work, calcium treated Type 316L austenitic stainless steels have been investigated electrochemically to evaluate the effect of modified inclusions on pitting corrosion. Staircase polarization measurements were performed in 3.5% NaCl solution, where the occurrence of pits in materials caused current spikes. During staircase polarization test, steels with calcium treatment show low and discontinuous current spikes while those without calcium treatment show high and continuous current spikes. The results show that calcium treatment in Ca/S ratio of 1 ∼ 2 leads to an increase in the pitting potential of several hundred mV. A relationship between the calcium treatment and pit initiation sites was described

  14. Assessment of membrane protection by 31P-NMR effects of lidocaine on calcium-paradox in myocardium

    International Nuclear Information System (INIS)

    Sakai, Hirosumi; Yoshiyama, Minoru; Teragaki, Masakazu; Takeuchi, Kazuhide; Takeda, Takeda; Ikata, Mari; Ishikawa, Makoto; Miura, Iwao

    1989-01-01

    In studying calcium paradox, perfused rat hearts were used to investigate the myocardial protective effects of lidocaine. Intracellular contents of phosphates were measured using the 31 P-NMR method. In hearts reexposed to calcium, following 3 minute calcium-free perfusion, a rapid contracture occurred, followed by rapid and complete disappearance of intracellular phosphates with no resumption of cardiac function. In hearts where lidocaine was administered from the onset of the calcium-free perfusion until 2 minutes following the onset of reexposure to calcium, both intracellular phosphates and cardiac contractility were maintained. Therefore, it can be said that cell membranes were protected by lidocaine

  15. Assessment of membrane protection by /sup 31/P-NMR effects of lidocaine on calcium-paradox in myocardium

    Energy Technology Data Exchange (ETDEWEB)

    Sakai, Hirosumi; Yoshiyama, Minoru; Teragaki, Masakazu; Takeuchi, Kazuhide; Takeda, Takeda; Ikata, Mari; Ishikawa, Makoto; Miura, Iwao

    1989-01-01

    In studying calcium paradox, perfused rat hearts were used to investigate the myocardial protective effects of lidocaine. Intracellular contents of phosphates were measured using the /sup 31/P-NMR method. In hearts reexposed to calcium, following 3 minute calcium-free perfusion, a rapid contracture occurred, followed by rapid and complete disappearance of intracellular phosphates with no resumption of cardiac function. In hearts where lidocaine was administered from the onset of the calcium-free perfusion until 2 minutes following the onset of reexposure to calcium, both intracellular phosphates and cardiac contractility were maintained. Therefore, it can be said that cell membranes were protected by lidocaine.

  16. Serial Spike Time Correlations Affect Probability Distribution of Joint Spike Events.

    Science.gov (United States)

    Shahi, Mina; van Vreeswijk, Carl; Pipa, Gordon

    2016-01-01

    Detecting the existence of temporally coordinated spiking activity, and its role in information processing in the cortex, has remained a major challenge for neuroscience research. Different methods and approaches have been suggested to test whether the observed synchronized events are significantly different from those expected by chance. To analyze the simultaneous spike trains for precise spike correlation, these methods typically model the spike trains as a Poisson process implying that the generation of each spike is independent of all the other spikes. However, studies have shown that neural spike trains exhibit dependence among spike sequences, such as the absolute and relative refractory periods which govern the spike probability of the oncoming action potential based on the time of the last spike, or the bursting behavior, which is characterized by short epochs of rapid action potentials, followed by longer episodes of silence. Here we investigate non-renewal processes with the inter-spike interval distribution model that incorporates spike-history dependence of individual neurons. For that, we use the Monte Carlo method to estimate the full shape of the coincidence count distribution and to generate false positives for coincidence detection. The results show that compared to the distributions based on homogeneous Poisson processes, and also non-Poisson processes, the width of the distribution of joint spike events changes. Non-renewal processes can lead to both heavy tailed or narrow coincidence distribution. We conclude that small differences in the exact autostructure of the point process can cause large differences in the width of a coincidence distribution. Therefore, manipulations of the autostructure for the estimation of significance of joint spike events seem to be inadequate.

  17. Modulation of the spike activity of neocortex neurons during a conditioned reflex.

    Science.gov (United States)

    Storozhuk, V M; Sanzharovskii, A V; Sachenko, V V; Busel, B I

    2000-01-01

    Experiments were conducted on cats to study the effects of iontophoretic application of glutamate and a number of modulators on the spike activity of neurons in the sensorimotor cortex during a conditioned reflex. These studies showed that glutamate, as well as exerting a direct influence on neuron spike activity, also had a delayed facilitatory action lasting 10-20 min after iontophoresis was finished. Adrenomimetics were found to have a double modulatory effect on intracortical glutamate connections: inhibitory and facilitatory effects were mediated by beta1 and beta2 adrenoceptors respectively. Although dopamine, like glutamate, facilitated neuron spike activity during the period of application, the simultaneous facilitatory actions of glutamate and L-DOPA were accompanied by occlusion of spike activity, and simultaneous application of glutamate and haloperidol suppressed spike activity associated with the conditioned reflex response. Facilitation thus appears to show a significant level of dependence on metabotropic glutamate receptors which, like dopamine receptors, are linked to the intracellular medium via Gi proteins.

  18. Calcium Signaling Is Required for Erythroid Enucleation.

    Directory of Open Access Journals (Sweden)

    Christina B Wölwer

    Full Text Available Although erythroid enucleation, the property of erythroblasts to expel their nucleus, has been known for 7ore than a century, surprisingly little is known regarding the molecular mechanisms governing this unique developmental process. Here we show that similar to cytokinesis, nuclear extrusion requires intracellular calcium signaling and signal transduction through the calmodulin (CaM pathway. However, in contrast to cytokinesis we found that orthochromatic erythroblasts require uptake of extracellular calcium to enucleate. Together these functional studies highlight a critical role for calcium signaling in the regulation of erythroid enucleation.

  19. Memristors Empower Spiking Neurons With Stochasticity

    KAUST Repository

    Al-Shedivat, Maruan

    2015-06-01

    Recent theoretical studies have shown that probabilistic spiking can be interpreted as learning and inference in cortical microcircuits. This interpretation creates new opportunities for building neuromorphic systems driven by probabilistic learning algorithms. However, such systems must have two crucial features: 1) the neurons should follow a specific behavioral model, and 2) stochastic spiking should be implemented efficiently for it to be scalable. This paper proposes a memristor-based stochastically spiking neuron that fulfills these requirements. First, the analytical model of the memristor is enhanced so it can capture the behavioral stochasticity consistent with experimentally observed phenomena. The switching behavior of the memristor model is demonstrated to be akin to the firing of the stochastic spike response neuron model, the primary building block for probabilistic algorithms in spiking neural networks. Furthermore, the paper proposes a neural soma circuit that utilizes the intrinsic nondeterminism of memristive switching for efficient spike generation. The simulations and analysis of the behavior of a single stochastic neuron and a winner-take-all network built of such neurons and trained on handwritten digits confirm that the circuit can be used for building probabilistic sampling and pattern adaptation machinery in spiking networks. The findings constitute an important step towards scalable and efficient probabilistic neuromorphic platforms. © 2011 IEEE.

  20. Factors correlated with volleyball spike velocity.

    Science.gov (United States)

    Forthomme, Bénédicte; Croisier, Jean-Louis; Ciccarone, Guido; Crielaard, Jean-Michel; Cloes, Marc

    2005-10-01

    Spike effectiveness represents a determining element in volleyball. To compete at a high level, the player must, in particular, produce a spike characterized by a high ball velocity. Some muscular and physical features could influence ball velocity during the volleyball spike. Descriptive laboratory study. A total of 19 male volleyball players from the 2 highest Belgian national divisions underwent an isokinetic assessment of the dominant shoulder and elbow. Ball velocity performance (radar gun) during a spike test, morphological feature, and jump capacity (ergo jump) of the player were measured. We tested the relationship between the isokinetic parameters or physical features and field performances represented by spike velocity. We also compared first-division and second-division player data. Spike velocity correlated significantly with strength performance of the dominant shoulder (internal rotators) and of the dominant elbow (flexors and extensors) in the concentric mode. Negative correlations were established with the concentric external rotator on internal rotator ratio at 400 deg/s and with the mixed ratio (external rotator at 60 deg/s in the eccentric mode on internal rotator at 240 deg/s in the concentric mode). Positive correlations appeared with both the volleyball players' jump capacity and body mass index. First-division players differed from second-division players by higher ball velocity and increased jump capacity. Some specific strength and physical characteristics correlated significantly with spike performance in high-level volleyball practice. Our results could provide useful information for training management and propose some reflections on injury prevention.

  1. Spike Bursts from an Excitable Optical System

    Science.gov (United States)

    Rios Leite, Jose R.; Rosero, Edison J.; Barbosa, Wendson A. S.; Tredicce, Jorge R.

    Diode Lasers with double optical feedback are shown to present power drop spikes with statistical distribution controllable by the ratio of the two feedback times. The average time between spikes and the variance within long time series are studied. The system is shown to be excitable and present bursting of spikes created with specific feedback time ratios and strength. A rate equation model, extending the Lang-Kobayashi single feedback for semiconductor lasers proves to match the experimental observations. Potential applications to construct network to mimic neural systems having controlled bursting properties in each unit will be discussed. Brazilian Agency CNPQ.

  2. Calcium model for mammalian skeletal muscle

    NARCIS (Netherlands)

    Wallinga, W.; Boom, H.B.K.; Heijink, R.J.; van der Vliet, G.H.

    1981-01-01

    A model is presented describing quantitatively the events between excitation and force development in skeletal muscle. It consists of a calcium mediated activation model (c.m.a.m.) in series with a force generator model (f.g.m.). The c.m.a.m. was based on intracellular processes such as cisternal

  3. Calcium ion currents mediating oocyte maturation events

    Directory of Open Access Journals (Sweden)

    Tosti Elisabetta

    2006-05-01

    Full Text Available Abstract During maturation, the last phase of oogenesis, the oocyte undergoes several changes which prepare it to be ovulated and fertilized. Immature oocytes are arrested in the first meiotic process prophase, that is morphologically identified by a germinal vesicle. The removal of the first meiotic block marks the initiation of maturation. Although a large number of molecules are involved in complex sequences of events, there is evidence that a calcium increase plays a pivotal role in meiosis re-initiation. It is well established that, during this process, calcium is released from the intracellular stores, whereas less is known on the role of external calcium entering the cell through the plasma membrane ion channels. This review is focused on the functional role of calcium currents during oocyte maturation in all the species, from invertebrates to mammals. The emerging role of specific L-type calcium channels will be discussed.

  4. Calcium-Induced calcium release during action potential firing in developing inner hair cells.

    Science.gov (United States)

    Iosub, Radu; Avitabile, Daniele; Grant, Lisa; Tsaneva-Atanasova, Krasimira; Kennedy, Helen J

    2015-03-10

    In the mature auditory system, inner hair cells (IHCs) convert sound-induced vibrations into electrical signals that are relayed to the central nervous system via auditory afferents. Before the cochlea can respond to normal sound levels, developing IHCs fire calcium-based action potentials that disappear close to the onset of hearing. Action potential firing triggers transmitter release from the immature IHC that in turn generates experience-independent firing in auditory neurons. These early signaling events are thought to be essential for the organization and development of the auditory system and hair cells. A critical component of the action potential is the rise in intracellular calcium that activates both small conductance potassium channels essential during membrane repolarization, and triggers transmitter release from the cell. Whether this calcium signal is generated by calcium influx or requires calcium-induced calcium release (CICR) is not yet known. IHCs can generate CICR, but to date its physiological role has remained unclear. Here, we used high and low concentrations of ryanodine to block or enhance CICR to determine whether calcium release from intracellular stores affected action potential waveform, interspike interval, or changes in membrane capacitance during development of mouse IHCs. Blocking CICR resulted in mixed action potential waveforms with both brief and prolonged oscillations in membrane potential and intracellular calcium. This mixed behavior is captured well by our mathematical model of IHC electrical activity. We perform two-parameter bifurcation analysis of the model that predicts the dependence of IHCs firing patterns on the level of activation of two parameters, the SK2 channels activation and CICR rate. Our data show that CICR forms an important component of the calcium signal that shapes action potentials and regulates firing patterns, but is not involved directly in triggering exocytosis. These data provide important insights

  5. Apamin-Sensitive Calcium-Activated Potassium Currents (SK) Are Activated by Persistent Calcium Currents in Rat Motoneurons

    OpenAIRE

    Li, X.; Bennett, D. J.

    2007-01-01

    Low voltage–activated persistent inward calcium currents (Ca PICs) occur in rat motoneurons and are mediated by Cav1.3 L-type calcium channels (L-Ca current). The objectives of this paper were to determine whether this L-Ca current activates a sustained calcium-activated potassium current (SK current) and examine how such SK currents change with spinal injury. For comparison, the SK current that produces the postspike afterhyperpolarization (mAHP) was also quantified. Intracellular recordings...

  6. Inferring oscillatory modulation in neural spike trains.

    Science.gov (United States)

    Arai, Kensuke; Kass, Robert E

    2017-10-01

    Oscillations are observed at various frequency bands in continuous-valued neural recordings like the electroencephalogram (EEG) and local field potential (LFP) in bulk brain matter, and analysis of spike-field coherence reveals that spiking of single neurons often occurs at certain phases of the global oscillation. Oscillatory modulation has been examined in relation to continuous-valued oscillatory signals, and independently from the spike train alone, but behavior or stimulus triggered firing-rate modulation, spiking sparseness, presence of slow modulation not locked to stimuli and irregular oscillations with large variability in oscillatory periods, present challenges to searching for temporal structures present in the spike train. In order to study oscillatory modulation in real data collected under a variety of experimental conditions, we describe a flexible point-process framework we call the Latent Oscillatory Spike Train (LOST) model to decompose the instantaneous firing rate in biologically and behaviorally relevant factors: spiking refractoriness, event-locked firing rate non-stationarity, and trial-to-trial variability accounted for by baseline offset and a stochastic oscillatory modulation. We also extend the LOST model to accommodate changes in the modulatory structure over the duration of the experiment, and thereby discover trial-to-trial variability in the spike-field coherence of a rat primary motor cortical neuron to the LFP theta rhythm. Because LOST incorporates a latent stochastic auto-regressive term, LOST is able to detect oscillations when the firing rate is low, the modulation is weak, and when the modulating oscillation has a broad spectral peak.

  7. Training Deep Spiking Neural Networks Using Backpropagation.

    Science.gov (United States)

    Lee, Jun Haeng; Delbruck, Tobi; Pfeiffer, Michael

    2016-01-01

    Deep spiking neural networks (SNNs) hold the potential for improving the latency and energy efficiency of deep neural networks through data-driven event-based computation. However, training such networks is difficult due to the non-differentiable nature of spike events. In this paper, we introduce a novel technique, which treats the membrane potentials of spiking neurons as differentiable signals, where discontinuities at spike times are considered as noise. This enables an error backpropagation mechanism for deep SNNs that follows the same principles as in conventional deep networks, but works directly on spike signals and membrane potentials. Compared with previous methods relying on indirect training and conversion, our technique has the potential to capture the statistics of spikes more precisely. We evaluate the proposed framework on artificially generated events from the original MNIST handwritten digit benchmark, and also on the N-MNIST benchmark recorded with an event-based dynamic vision sensor, in which the proposed method reduces the error rate by a factor of more than three compared to the best previous SNN, and also achieves a higher accuracy than a conventional convolutional neural network (CNN) trained and tested on the same data. We demonstrate in the context of the MNIST task that thanks to their event-driven operation, deep SNNs (both fully connected and convolutional) trained with our method achieve accuracy equivalent with conventional neural networks. In the N-MNIST example, equivalent accuracy is achieved with about five times fewer computational operations.

  8. Towards statistical summaries of spike train data.

    Science.gov (United States)

    Wu, Wei; Srivastava, Anuj

    2011-01-30

    Statistical inference has an important role in analysis of neural spike trains. While current approaches are mostly model-based, and designed for capturing the temporal evolution of the underlying stochastic processes, we focus on a data-driven approach where statistics are defined and computed in function spaces where individual spike trains are viewed as points. The first contribution of this paper is to endow spike train space with a parameterized family of metrics that takes into account different time warpings and generalizes several currently used metrics. These metrics are essentially penalized L(p) norms, involving appropriate functions of spike trains, with penalties associated with time-warpings. The second contribution of this paper is to derive a notion of a mean spike train in the case when p=2. We present an efficient recursive algorithm, termed Matching-Minimization algorithm, to compute the sample mean of a set of spike trains. The proposed metrics as well as the mean computations are demonstrated using an experimental recording from the motor cortex. Copyright © 2010 Elsevier B.V. All rights reserved.

  9. Macroscopic Description for Networks of Spiking Neurons

    Science.gov (United States)

    Montbrió, Ernest; Pazó, Diego; Roxin, Alex

    2015-04-01

    A major goal of neuroscience, statistical physics, and nonlinear dynamics is to understand how brain function arises from the collective dynamics of networks of spiking neurons. This challenge has been chiefly addressed through large-scale numerical simulations. Alternatively, researchers have formulated mean-field theories to gain insight into macroscopic states of large neuronal networks in terms of the collective firing activity of the neurons, or the firing rate. However, these theories have not succeeded in establishing an exact correspondence between the firing rate of the network and the underlying microscopic state of the spiking neurons. This has largely constrained the range of applicability of such macroscopic descriptions, particularly when trying to describe neuronal synchronization. Here, we provide the derivation of a set of exact macroscopic equations for a network of spiking neurons. Our results reveal that the spike generation mechanism of individual neurons introduces an effective coupling between two biophysically relevant macroscopic quantities, the firing rate and the mean membrane potential, which together govern the evolution of the neuronal network. The resulting equations exactly describe all possible macroscopic dynamical states of the network, including states of synchronous spiking activity. Finally, we show that the firing-rate description is related, via a conformal map, to a low-dimensional description in terms of the Kuramoto order parameter, called Ott-Antonsen theory. We anticipate that our results will be an important tool in investigating how large networks of spiking neurons self-organize in time to process and encode information in the brain.

  10. In vivo calcium imaging of evoked calcium waves in the embryonic cortex

    Directory of Open Access Journals (Sweden)

    Mikhail eYuryev

    2016-01-01

    Full Text Available The dynamics of intracellular calcium fluxes are instrumental in the proliferation, differentiation and migration of neuronal cells. Knowledge thus far of the relationship between these calcium changes and physiological processes in the developing brain has derived principally from ex vivo and in vitro experiments. Here, we present a new method to image intracellular calcium flux in the cerebral cortex of live rodent embryos, whilst attached to the dam through the umbilical cord. Using this approach we demonstrate induction of calcium waves by laser stimulation. These waves are sensitive to ATP-receptor blockade and are significantly increased by pharmacological facilitation of intracellular-calcium release. This approach is the closest to physiological conditions yet achieved for imaging of calcium in the embryonic brain and as such opens new avenues for the study of prenatal brain development. Furthermore, the developed method could open the possibilities of preclinical translational studies in embryos particularly important for developmentally related diseases such as schizophrenia and autism.

  11. Calcium supplements

    Science.gov (United States)

    ... and over: 1,200 mg/day The body needs vitamin D to help absorb calcium. You can get ... from your diet. Ask your provider whether you need to take a vitamin D supplement. SIDE EFFECTS AND SAFETY DO NOT ...

  12. Intracellular Signalling by C-Peptide

    Directory of Open Access Journals (Sweden)

    Claire E. Hills

    2008-01-01

    Full Text Available C-peptide, a cleavage product of the proinsulin molecule, has long been regarded as biologically inert, serving merely as a surrogate marker for insulin release. Recent findings demonstrate both a physiological and protective role of C-peptide when administered to individuals with type I diabetes. Data indicate that C-peptide appears to bind in nanomolar concentrations to a cell surface receptor which is most likely to be G-protein coupled. Binding of C-peptide initiates multiple cellular effects, evoking a rise in intracellular calcium, increased PI-3-kinase activity, stimulation of the Na+/K+ ATPase, increased eNOS transcription, and activation of the MAPK signalling pathway. These cell signalling effects have been studied in multiple cell types from multiple tissues. Overall these observations raise the possibility that C-peptide may serve as a potential therapeutic agent for the treatment or prevention of long-term complications associated with diabetes.

  13. Nuclear magnetic resonance studies of intracellular ions in perfused from heart

    International Nuclear Information System (INIS)

    Burnstein, D.; Fossel, E.T.

    1987-01-01

    Intracellular sodium, potassium, and lithium were observed in a perfused frog heart by nuclear magnetic resonance (NMR) spectroscopy. A perfusate buffer containing the shift reagent, dysprosium tripolyphosphate, was used in combination with mathematical filtering or presaturation of the extracellular resonance to separate the intra- and extracellular sodium NMR signals. Addition of 10 μM ouabain to the perfusate, perfusion with a zero potassium, low-calcium buffer, and replacement of 66% of the perfusate sodium with lithium resulted in changes in the intracellular sodium levels. An increase of 45% in the intracellular sodium was observed when changing the pacing rate from 0 to 60 beats/min (with proportional changes for intermediate pacing rates). The ratio of intracellular potassium to sodium concentration was determined to be 2.3 by NMR, indicating that a substantial amount of the intracellular potassium is undetectable with these NMR method. In addition, intracellular lithium was observed during perfusion with a lithium-containing perfusate

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

    International Nuclear Information System (INIS)

    Borle, A.B.

    1990-01-01

    An array of techniques can be used to study cell calcium metabolism that comprises several calcium compartments and many types of transport systems such as ion channels, ATP-dependent pumps, and antiporters. The measurement of total call calcium brings little information of value since 60 to 80% of total cell calcium is actually bound to the extracellular glycocalyx. Cell fractionation and differential centrifugation have been used to study intracellular Ca 2+ compartmentalization, but the methods suffer from the possibility of Ca 2+ loss or redistribution among cell fractions. Steady-state kinetic analyses of 45 Ca uptake or desaturation curves have been used to study the distribution of Ca 2+ among various kinetic pools in living cells and their rate of Ca 2+ exchange, but the analyses are constrained by many limitations. Nonsteady-state tracer studies can provide information about rapid changes in calcium influx or efflux in and out of the cell. Zero-time kinetics of 45 Ca uptake can detect instantaneous changes in calcium influx, while 45 Ca fractional efflux ratio, can detect rapid stimulations or inhibitions of calcium efflux out of cells. The best strategy to study cell calcium metabolism is to use several different methods that focus on a specific problem from widely different angles

  15. Intracellular mediators of potassium-induced aldosterone secretion

    International Nuclear Information System (INIS)

    Ganguly, A.; Chiou, S.; Davis, J.S.

    1990-01-01

    We have investigated the intracellular messengers of potassium in eliciting aldosterone secretion in calf adrenal glomerulosa cells since there were unresolved issues relating to the role of phosphoinositides, cAMP and protein kinases. We observed no evidence of hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP 2 ) in 3 H-inositol labeled alf adrenal cells or increase of cAMP in response to potassium. Addition of calcium channel blocker, nitrendipine after stimulating adrenal glomerulosa cells with potassium, markedly inhibited aldosterone secretion. A calmodulin inhibitor (W-7) produced greater reduction of aldosterone secretion than an inhibitor of protein kinase C (H-7). These results suggest that a rise in cytosolic free calcium concentration through voltage-dependent calcium channel and calmodulin are the critical determinants of aldosterone secretion stimulated by potassium

  16. Enhancement of Spike-Timing-Dependent Plasticity in Spiking Neural Systems with Noise.

    Science.gov (United States)

    Nobukawa, Sou; Nishimura, Haruhiko

    2016-08-01

    Synaptic plasticity is widely recognized to support adaptable information processing in the brain. Spike-timing-dependent plasticity, one subtype of plasticity, can lead to synchronous spike propagation with temporal spiking coding information. Recently, it was reported that in a noisy environment, like the actual brain, the spike-timing-dependent plasticity may be made efficient by the effect of stochastic resonance. In the stochastic resonance, the presence of noise helps a nonlinear system in amplifying a weak (under barrier) signal. However, previous studies have ignored the full variety of spiking patterns and many relevant factors in neural dynamics. Thus, in order to prove the physiological possibility for the enhancement of spike-timing-dependent plasticity by stochastic resonance, it is necessary to demonstrate that this stochastic resonance arises in realistic cortical neural systems. In this study, we evaluate this stochastic resonance phenomenon in the realistic cortical neural system described by the Izhikevich neuron model and compare the characteristics of typical spiking patterns of regular spiking, intrinsically bursting and chattering experimentally observed in the cortex.

  17. Excitability in a stochastic differential equation model for calcium puffs.

    Science.gov (United States)

    Rüdiger, S

    2014-06-01

    Calcium dynamics are essential to a multitude of cellular processes. For many cell types, localized discharges of calcium through small clusters of intracellular channels are building blocks for all spatially extended calcium signals. Because of the large noise amplitude, the validity of noise-approximating model equations for this system has been questioned. Here we revisit the master equations for local calcium release, examine the multiple scales of calcium concentrations in the cluster domain, and derive adapted stochastic differential equations. We show by comparison of discrete and continuous trajectories that the Langevin equations can be made consistent with the master equations even for very small channel numbers. In its deterministic limit, the model reveals that excitability, a dynamical phenomenon observed in many natural systems, is at the core of calcium puffs. The model also predicts a bifurcation from transient to sustained release which may link local and global calcium signals in cells.

  18. Epileptiform spike detection via convolutional neural networks

    DEFF Research Database (Denmark)

    Johansen, Alexander Rosenberg; Jin, Jing; Maszczyk, Tomasz

    2016-01-01

    The EEG of epileptic patients often contains sharp waveforms called "spikes", occurring between seizures. Detecting such spikes is crucial for diagnosing epilepsy. In this paper, we develop a convolutional neural network (CNN) for detecting spikes in EEG of epileptic patients in an automated...... fashion. The CNN has a convolutional architecture with filters of various sizes applied to the input layer, leaky ReLUs as activation functions, and a sigmoid output layer. Balanced mini-batches were applied to handle the imbalance in the data set. Leave-one-patient-out cross-validation was carried out...... to test the CNN and benchmark models on EEG data of five epilepsy patients. We achieved 0.947 AUC for the CNN, while the best performing benchmark model, Support Vector Machines with Gaussian kernel, achieved an AUC of 0.912....

  19. The electric potential of tripolar spikes

    International Nuclear Information System (INIS)

    Nocera, L.

    2010-01-01

    We present an analytical formula for the waveform of the electric potential associated with a tripolar spike in a plasma. This formula is based on the construction and on the subsequent solution of a differential equation for the waveform. We work out this equation as a direct consequence of the morphological and functional properties of the observed waveform, without making any reference to the velocity distributions of the electrons and of the ions which sustain the spike. In the approximation of small potential amplitudes, we solve this equation by quadrature. In particular, in the second order approximation, the solution of this equation is given in terms of elementary functions. This analytical solution is able to reproduce the potential waveforms associated with electron holes, ion holes, monotonic and nonmonotonic double layers and tripolar spikes, in excellent agreement with observations.

  20. Implementing Signature Neural Networks with Spiking Neurons.

    Science.gov (United States)

    Carrillo-Medina, José Luis; Latorre, Roberto

    2016-01-01

    Spiking Neural Networks constitute the most promising approach to develop realistic Artificial Neural Networks (ANNs). Unlike traditional firing rate-based paradigms, information coding in spiking models is based on the precise timing of individual spikes. It has been demonstrated that spiking ANNs can be successfully and efficiently applied to multiple realistic problems solvable with traditional strategies (e.g., data classification or pattern recognition). In recent years, major breakthroughs in neuroscience research have discovered new relevant computational principles in different living neural systems. Could ANNs benefit from some of these recent findings providing novel elements of inspiration? This is an intriguing question for the research community and the development of spiking ANNs including novel bio-inspired information coding and processing strategies is gaining attention. From this perspective, in this work, we adapt the core concepts of the recently proposed Signature Neural Network paradigm-i.e., neural signatures to identify each unit in the network, local information contextualization during the processing, and multicoding strategies for information propagation regarding the origin and the content of the data-to be employed in a spiking neural network. To the best of our knowledge, none of these mechanisms have been used yet in the context of ANNs of spiking neurons. This paper provides a proof-of-concept for their applicability in such networks. Computer simulations show that a simple network model like the discussed here exhibits complex self-organizing properties. The combination of multiple simultaneous encoding schemes allows the network to generate coexisting spatio-temporal patterns of activity encoding information in different spatio-temporal spaces. As a function of the network and/or intra-unit parameters shaping the corresponding encoding modality, different forms of competition among the evoked patterns can emerge even in the absence

  1. Prolonged response to calling songs by the L3 auditory interneuron in female crickets (Acheta domesticus): intracellular evaluation.

    Science.gov (United States)

    Navia, Benjamin; Stout, John; Atkins, Gordon

    2003-03-01

    The L3 auditory interneuron in female Acheta domesticus, produces two different responses to the male calling song: an immediate response and a prolonged response. The prolonged response exhibited spiking activity and a correlated prolonged depolarization, both of which are clearly seen in intracellular recordings. The morphology revealed by intracellular staining was clearly the L3 neuron. The amplitude of the prolonged depolarization associated with the prolonged response increased with increases in sound intensity, resulting in increased spiking rates. Both depolarization and sound presentation increased the spiking rate and the slope of pre-potentials (thus leading to spiking threshold more quickly). Injecting hyperpolarizing current had the expected opposite effect. The effects of positive current injection and sound presentation were additive, resulting in spiking rates that were approximately double the rates in response to sound alone. Short postsynaptic potentials (PSPs), whose duration ranged from 15-60 ms, which may lead to action potentials were also observed in all recordings and summated with the prolonged depolarization, increasing the probability of spiking. Copyright 2003 Wiley-Liss, Inc.

  2. Intracellular renin disrupts chemical communication between heart cells. Pathophysiological implications

    Directory of Open Access Journals (Sweden)

    Walmor eDe Mello

    2015-01-01

    Full Text Available The influence of intracellular renin on the process of chemical communication between cardiac cells was investigated in cell pairs isolated from the left ventricle of adult Wistar Kyoto rats. The enzyme together with Lucifer yellow CH was dialyzed into one cell of the pair using the whole cell clamp technique. The diffusion of the dye in the dialyzed and in non-dialyzed cell was followed by measuring the intensity of fluorescence in both cells as a function of time. The results indicated that; 1 under normal conditions, Lucifer Yellow flows from cell-to-cell through gap junctions; 2 the intracellular dialysis of renin (100nM disrupts chemical communication-an effect enhanced by simultaneous administration of angiotensinogen (100nM; 3 enalaprilat (10-9M administered to the cytosol together with renin reduced drastically the uncoupling action of the enzyme; 4 aliskiren (10-8M inhibited the effect of renin on chemical communication;5 the possible role of intracellular renin independently of angiotensin II (Ang II was evaluated including the increase of the inward calcium current elicited by the enzyme and the possible role of oxidative stress on the disruption of cell communication; 6 the possible harmful versus the beneficial effect of intracellular renin during myocardial infarction was discussed;7 the present results indicate that intracellular renin due to internalization or in situ synthesis, causes a severe impairment of chemical communication in the heart resulting in derangement of metabolic cooperation with serious consequences for heart function.

  3. Span: spike pattern association neuron for learning spatio-temporal spike patterns.

    Science.gov (United States)

    Mohemmed, Ammar; Schliebs, Stefan; Matsuda, Satoshi; Kasabov, Nikola

    2012-08-01

    Spiking Neural Networks (SNN) were shown to be suitable tools for the processing of spatio-temporal information. However, due to their inherent complexity, the formulation of efficient supervised learning algorithms for SNN is difficult and remains an important problem in the research area. This article presents SPAN - a spiking neuron that is able to learn associations of arbitrary spike trains in a supervised fashion allowing the processing of spatio-temporal information encoded in the precise timing of spikes. The idea of the proposed algorithm is to transform spike trains during the learning phase into analog signals so that common mathematical operations can be performed on them. Using this conversion, it is possible to apply the well-known Widrow-Hoff rule directly to the transformed spike trains in order to adjust the synaptic weights and to achieve a desired input/output spike behavior of the neuron. In the presented experimental analysis, the proposed learning algorithm is evaluated regarding its learning capabilities, its memory capacity, its robustness to noisy stimuli and its classification performance. Differences and similarities of SPAN regarding two related algorithms, ReSuMe and Chronotron, are discussed.

  4. Improved SpikeProp for Using Particle Swarm Optimization

    Directory of Open Access Journals (Sweden)

    Falah Y. H. Ahmed

    2013-01-01

    Full Text Available A spiking neurons network encodes information in the timing of individual spike times. A novel supervised learning rule for SpikeProp is derived to overcome the discontinuities introduced by the spiking thresholding. This algorithm is based on an error-backpropagation learning rule suited for supervised learning of spiking neurons that use exact spike time coding. The SpikeProp is able to demonstrate the spiking neurons that can perform complex nonlinear classification in fast temporal coding. This study proposes enhancements of SpikeProp learning algorithm for supervised training of spiking networks which can deal with complex patterns. The proposed methods include the SpikeProp particle swarm optimization (PSO and angle driven dependency learning rate. These methods are presented to SpikeProp network for multilayer learning enhancement and weights optimization. Input and output patterns are encoded as spike trains of precisely timed spikes, and the network learns to transform the input trains into target output trains. With these enhancements, our proposed methods outperformed other conventional neural network architectures.

  5. Verapamil inhibits L-type calcium channel mediated apoptosis in human colon cancer cells.

    Science.gov (United States)

    Zawadzki, Antoni; Liu, Qing; Wang, Yusheng; Melander, Arne; Jeppsson, Bengt; Thorlacius, Henrik

    2008-11-01

    Treatment with calcium channel blockers have been associated with increased colon cancer mortality in epidemiologic studies. We examined the potential expression and function of calcium channels in two human colon cancer cell lines. Both primary (collected at operation) and commercially-available human colon cancer cell lines were used. The colon cancer cells were incubated with a calcium channel blocker (verapamil) and a calcium channel agonist (BayK 8644) at clinically relevant concentrations. L-type calcium channel mRNA was determined by reverse-transcription polymerase chain reaction. Intracellular calcium ion levels were measured with fluorometry and apoptosis with flow cytometry. Both types of cells expressed L-type calcium channel mRNA, comprising an alpha-1D and a beta-3 subunit, whereas the cells were negative for N-type and P-type channels. The selective calcium channel agonist (BayK 8644), dose-dependently increased intracellular calcium ion levels and the level of apoptosis in primary human colon cancer cells. Pretreatment with verapamil completely abolished both calcium channel agonist-induced influx of calcium and apoptosis in these cells. These data demonstrate that human colon cancer cells express L-type calcium channels that mediate calcium influx and apoptosis, which warrants further studies to determine whether calcium channel blockers may promote colon cancer growth.

  6. Spike-timing control by dendritic plateau potentials in the presence of synaptic barrages

    Directory of Open Access Journals (Sweden)

    Adam Sol Shai

    2014-08-01

    Full Text Available Apical and tuft dendrites of pyramidal neurons support regenerative electrical potentials, giving rise to long-lasting (~ hundreds of milliseconds and strong (~50 mV from rest depolarizations. Such plateau events rely on clustered glutamatergic input, can be mediated by calcium and NMDA currents, and often generate somatic depolarizations that last for the time course of the dendritic plateau event. We address the computational significance of such single-neuron processing via reduced but biophysically realistic modeling. We introduce a model based on two discrete integration zones, a somatic and a dendritic one, that communicate via a long plateau-conductance. We show principled differences in the way dendritic versus somatic inhibition controls spike timing, and demonstrate how this could implement a mechanism of spike time control in the face of barrages of synaptic inputs.

  7. Calcium's Role in Mechanotransduction during Muscle Development

    Directory of Open Access Journals (Sweden)

    Tatiana Benavides Damm

    2014-01-01

    Full Text Available Mechanotransduction is a process where cells sense their surroundings and convert the physical forces in their environment into an appropriate response. Calcium plays a crucial role in the translation of such forces to biochemical signals that control various biological processes fundamental in muscle development. The mechanical stimulation of muscle cells may for example result from stretch, electric and magnetic stimulation, shear stress, and altered gravity exposure. The response, mainly involving changes in intracellular calcium concentration then leads to a cascade of events by the activation of downstream signaling pathways. The key calcium-dependent pathways described here include the nuclear factor of activated T cells (NFAT and mitogen-activated protein kinase (MAPK activation. The subsequent effects in cellular homeostasis consist of cytoskeletal remodeling, cell cycle progression, growth, differentiation, and apoptosis, all necessary for healthy muscle development, repair, and regeneration. A deregulation from the normal process due to disuse, trauma, or disease can result in a clinical condition such as muscle atrophy, which entails a significant loss of muscle mass. In order to develop therapies against such diseased states, we need to better understand the relevance of calcium signaling and the downstream responses to mechanical forces in skeletal muscle. The purpose of this review is to discuss in detail how diverse mechanical stimuli cause changes in calcium homeostasis by affecting membrane channels and the intracellular stores, which in turn regulate multiple pathways that impart these effects and control the fate of muscle tissue.

  8. Spike-timing theory of working memory.

    Directory of Open Access Journals (Sweden)

    Botond Szatmáry

    Full Text Available Working memory (WM is the part of the brain's memory system that provides temporary storage and manipulation of information necessary for cognition. Although WM has limited capacity at any given time, it has vast memory content in the sense that it acts on the brain's nearly infinite repertoire of lifetime long-term memories. Using simulations, we show that large memory content and WM functionality emerge spontaneously if we take the spike-timing nature of neuronal processing into account. Here, memories are represented by extensively overlapping groups of neurons that exhibit stereotypical time-locked spatiotemporal spike-timing patterns, called polychronous patterns; and synapses forming such polychronous neuronal groups (PNGs are subject to associative synaptic plasticity in the form of both long-term and short-term spike-timing dependent plasticity. While long-term potentiation is essential in PNG formation, we show how short-term plasticity can temporarily strengthen the synapses of selected PNGs and lead to an increase in the spontaneous reactivation rate of these PNGs. This increased reactivation rate, consistent with in vivo recordings during WM tasks, results in high interspike interval variability and irregular, yet systematically changing, elevated firing rate profiles within the neurons of the selected PNGs. Additionally, our theory explains the relationship between such slowly changing firing rates and precisely timed spikes, and it reveals a novel relationship between WM and the perception of time on the order of seconds.

  9. Physics of volleyball: Spiking with a purpose

    Science.gov (United States)

    Behroozi, F.

    1998-05-01

    A few weeks ago our volleyball coach telephoned me with a problem: How high should a player jump to "spike" a "set" ball so it would clear the net and land at a known distance on the other side of the net?

  10. Investment spikes in Dutch greenhouse horticulture

    NARCIS (Netherlands)

    Goncharova, N.; Oskam, A.; Oude Lansink, A.G.J.M.; Vlist, van der A.J.; Verstegen, J.A.A.M.

    2008-01-01

    The presence of investment cycles demonstrates the long-run policy of firms investing in particular periods (investment spikes) with lower or zero investment levels in between, which contradicts the smooth pattern predicted by a convex adjustment model. This paper investigates the spells between

  11. Food Price Spikes, Price Insulation, and Poverty

    OpenAIRE

    Anderson, Kym; Ivanic, Maros; Martin, Will

    2013-01-01

    This paper has two purposes. It first considers the impact on world food prices of the changes in restrictions on trade in staple foods during the 2008 world food price crisis. Those changes -- reductions in import protection or increases in export restraints -- were meant to partially insulate domestic markets from the spike in international prices. The authors find that this insulation a...

  12. Gymnosporia montana Benth.(Mountain Spike Thorn)

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 23; Issue 2. Gymnosporia montana Benth. (Mountain Spike Thorn). Flowering Trees Volume 23 Issue 2 February 2018 pp 245-245. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/023/02/0245-0245 ...

  13. The intracellular pharmacokinetics of terminally capped peptides.

    NARCIS (Netherlands)

    Ruttekolk, I.R.R.; Witsenburg, J.J.; Glauner, H.B.; Bovee-Geurts, P.H.M.; Ferro, E.S.; Verdurmen, W.P.R.; Brock, R.E.

    2012-01-01

    With significant progress in delivery technologies, peptides and peptidomimetics are receiving increasing attention as potential therapeutics also for intracellular applications. However, analyses of the intracellular behavior of peptides are a challenge; therefore, knowledge on the intracellular

  14. Latency modulation of collicular neurons induced by electric stimulation of the auditory cortex in Hipposideros pratti: In vivo intracellular recording.

    Directory of Open Access Journals (Sweden)

    Kang Peng

    Full Text Available In the auditory pathway, the inferior colliculus (IC receives and integrates excitatory and inhibitory inputs from the lower auditory nuclei, contralateral IC, and auditory cortex (AC, and then uploads these inputs to the thalamus and cortex. Meanwhile, the AC modulates the sound signal processing of IC neurons, including their latency (i.e., first-spike latency. Excitatory and inhibitory corticofugal projections to the IC may shorten and prolong the latency of IC neurons, respectively. However, the synaptic mechanisms underlying the corticofugal latency modulation of IC neurons remain unclear. Thus, this study probed these mechanisms via in vivo intracellular recording and acoustic and focal electric stimulation. The AC latency modulation of IC neurons is possibly mediated by pre-spike depolarization duration, pre-spike hyperpolarization duration, and spike onset time. This study suggests an effective strategy for the timing sequence determination of auditory information uploaded to the thalamus and cortex.

  15. Spiking Neural P Systems with Communication on Request.

    Science.gov (United States)

    Pan, Linqiang; Păun, Gheorghe; Zhang, Gexiang; Neri, Ferrante

    2017-12-01

    Spiking Neural [Formula: see text] Systems are Neural System models characterized by the fact that each neuron mimics a biological cell and the communication between neurons is based on spikes. In the Spiking Neural [Formula: see text] systems investigated so far, the application of evolution rules depends on the contents of a neuron (checked by means of a regular expression). In these [Formula: see text] systems, a specified number of spikes are consumed and a specified number of spikes are produced, and then sent to each of the neurons linked by a synapse to the evolving neuron. [Formula: see text]In the present work, a novel communication strategy among neurons of Spiking Neural [Formula: see text] Systems is proposed. In the resulting models, called Spiking Neural [Formula: see text] Systems with Communication on Request, the spikes are requested from neighboring neurons, depending on the contents of the neuron (still checked by means of a regular expression). Unlike the traditional Spiking Neural [Formula: see text] systems, no spikes are consumed or created: the spikes are only moved along synapses and replicated (when two or more neurons request the contents of the same neuron). [Formula: see text]The Spiking Neural [Formula: see text] Systems with Communication on Request are proved to be computationally universal, that is, equivalent with Turing machines as long as two types of spikes are used. Following this work, further research questions are listed to be open problems.

  16. Functional genomics of intracellular bacteria.

    Science.gov (United States)

    de Barsy, Marie; Greub, Gilbert

    2013-07-01

    During the genomic era, a large amount of whole-genome sequences accumulated, which identified many hypothetical proteins of unknown function. Rapidly, functional genomics, which is the research domain that assign a function to a given gene product, has thus been developed. Functional genomics of intracellular pathogenic bacteria exhibit specific peculiarities due to the fastidious growth of most of these intracellular micro-organisms, due to the close interaction with the host cell, due to the risk of contamination of experiments with host cell proteins and, for some strict intracellular bacteria such as Chlamydia, due to the absence of simple genetic system to manipulate the bacterial genome. To identify virulence factors of intracellular pathogenic bacteria, functional genomics often rely on bioinformatic analyses compared with model organisms such as Escherichia coli and Bacillus subtilis. The use of heterologous expression is another common approach. Given the intracellular lifestyle and the many effectors that are used by the intracellular bacteria to corrupt host cell functions, functional genomics is also often targeting the identification of new effectors such as those of the T4SS of Brucella and Legionella.

  17. Impact of spike train autostructure on probability distribution of joint spike events.

    Science.gov (United States)

    Pipa, Gordon; Grün, Sonja; van Vreeswijk, Carl

    2013-05-01

    The discussion whether temporally coordinated spiking activity really exists and whether it is relevant has been heated over the past few years. To investigate this issue, several approaches have been taken to determine whether synchronized events occur significantly above chance, that is, whether they occur more often than expected if the neurons fire independently. Most investigations ignore or destroy the autostructure of the spiking activity of individual cells or assume Poissonian spiking as a model. Such methods that ignore the autostructure can significantly bias the coincidence statistics. Here, we study the influence of the autostructure on the probability distribution of coincident spiking events between tuples of mutually independent non-Poisson renewal processes. In particular, we consider two types of renewal processes that were suggested as appropriate models of experimental spike trains: a gamma and a log-normal process. For a gamma process, we characterize the shape of the distribution analytically with the Fano factor (FFc). In addition, we perform Monte Carlo estimations to derive the full shape of the distribution and the probability for false positives if a different process type is assumed as was actually present. We also determine how manipulations of such spike trains, here dithering, used for the generation of surrogate data change the distribution of coincident events and influence the significance estimation. We find, first, that the width of the coincidence count distribution and its FFc depend critically and in a nontrivial way on the detailed properties of the structure of the spike trains as characterized by the coefficient of variation CV. Second, the dependence of the FFc on the CV is complex and mostly nonmonotonic. Third, spike dithering, even if as small as a fraction of the interspike interval, can falsify the inference on coordinated firing.

  18. Spike detection algorithm improvement, spike waveforms projections with PCA and hierarchical classification

    OpenAIRE

    Biffi, Emilia; Ghezzi, Diego; Pedrocchi, Alessandra; Ferrigno, Giancarlo

    2008-01-01

    Definition of single spikes from multiunit spike trains plays a critical role in neurophysiology and in neuroengineering. Moreover, long period analysis are needed to study synaptic plasticity effects and observe the long and medium term development on which all central nervous system (CNS) learning functions are based. Therefore, the increasing importance of long period recordings makes necessary on-line and real time analysis, memory use optimization and data transmission rate improvement. ...

  19. Calcium blood test

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/article/003477.htm Calcium blood test To use the sharing features on this page, please enable JavaScript. The calcium blood test measures the level of calcium in the blood. ...

  20. The host-binding domain of the P2 phage tail spike reveals a trimeric iron-binding structure

    International Nuclear Information System (INIS)

    Yamashita, Eiki; Nakagawa, Atsushi; Takahashi, Junichi; Tsunoda, Kin-ichi; Yamada, Seiko; Takeda, Shigeki

    2011-01-01

    The C-terminal domain of a bacteriophage P2 tail-spike protein, gpV, was crystallized and its structure was solved at 1.27 Å resolution. The refined model showed a triple β-helix structure and the presence of iron, calcium and chloride ions. The adsorption and infection of bacteriophage P2 is mediated by tail fibres and tail spikes. The tail spikes on the tail baseplate are used to irreversibly adsorb to the host cells. Recently, a P2 phage tail-spike protein, gpV, was purified and it was shown that a C-terminal domain, Ser87–Leu211, is sufficient for the binding of gpV to host Escherichia coli membranes [Kageyama et al. (2009 ▶), Biochemistry, 48, 10129–10135]. In this paper, the crystal structure of the C-terminal domain of P2 gpV is reported. The structure is a triangular pyramid and looks like a spearhead composed of an intertwined β-sheet, a triple β-helix and a metal-binding region containing iron, calcium and chloride ions

  1. Stochastic spike synchronization in a small-world neural network with spike-timing-dependent plasticity.

    Science.gov (United States)

    Kim, Sang-Yoon; Lim, Woochang

    2018-01-01

    We consider the Watts-Strogatz small-world network (SWN) consisting of subthreshold neurons which exhibit noise-induced spikings. This neuronal network has adaptive dynamic synaptic strengths governed by the spike-timing-dependent plasticity (STDP). In previous works without STDP, stochastic spike synchronization (SSS) between noise-induced spikings of subthreshold neurons was found to occur in a range of intermediate noise intensities. Here, we investigate the effect of additive STDP on the SSS by varying the noise intensity. Occurrence of a "Matthew" effect in synaptic plasticity is found due to a positive feedback process. As a result, good synchronization gets better via long-term potentiation of synaptic strengths, while bad synchronization gets worse via long-term depression. Emergences of long-term potentiation and long-term depression of synaptic strengths are intensively investigated via microscopic studies based on the pair-correlations between the pre- and the post-synaptic IISRs (instantaneous individual spike rates) as well as the distributions of time delays between the pre- and the post-synaptic spike times. Furthermore, the effects of multiplicative STDP (which depends on states) on the SSS are studied and discussed in comparison with the case of additive STDP (independent of states). These effects of STDP on the SSS in the SWN are also compared with those in the regular lattice and the random graph. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Short-range intercellular calcium signaling in bone

    DEFF Research Database (Denmark)

    Jørgensen, Niklas R

    2005-01-01

    different mechanisms for this propagation. One mechanism involves the secretion of a nucleotide, possibly ATP, acting in an autocrine action to purinergic P2Y2 receptors on the neighboring cells, leading to intracellular IP3 generation and subsequent release of calcium from intracellular stores. The other...... to osteoclasts as well. We demonstrated that paracrine action of ATP was responsible for the wave propagation, but now the purinergic P2X7 receptor was involved. Thus, the studies demonstrate that calcium signals can be propagated not only among osteoblasts, but also between osteoblasts and osteoclasts...

  3. Acute Cocaine Exposure elicits rises in calcium in Arousal Related Laterodorsal Tegmental Neurons

    DEFF Research Database (Denmark)

    Lambert, Mads; Ipsen, Theis; Kohlmeier, Kristi Anne

    2017-01-01

    Cocaine has strong reinforcing properties, which underlie its high addiction potential. Reinforcement of use of addictive drugs is associated with rises in dopamine (DA) in mesoaccumbal circuitry. Excitatory afferent input to mesoaccumbal circuitry sources from the laterodorsal tegmental nucleus...... (LDT). Chronic, systemic cocaine exposure has been shown to have cellular effects on LDT cells, but acute actions of local application have never been demonstrated. Using calcium imaging, we show that acute application of cocaine to mouse brain slices induces calcium spiking in cells of the LDT...... of synaptic DA, but via a different pharmacological action than cocaine, induced calcium spiking with similar profiles. Although large differences in spiking were not noted in an animal model associated with a heightened proclivity of acquiring addiction-related behavior, the prenatal nicotine exposed mouse...

  4. Host-directed antimicrobial drugs with broad-spectrum efficacy against intracellular bacterial pathogens.

    Science.gov (United States)

    Czyż, Daniel M; Potluri, Lakshmi-Prasad; Jain-Gupta, Neeta; Riley, Sean P; Martinez, Juan J; Steck, Theodore L; Crosson, Sean; Shuman, Howard A; Gabay, Joëlle E

    2014-07-29

    We sought a new approach to treating infections by intracellular bacteria, namely, by altering host cell functions that support their growth. We screened a library of 640 Food and Drug Administration (FDA)-approved compounds for agents that render THP-1 cells resistant to infection by four intracellular pathogens. We identified numerous drugs that are not antibiotics but were highly effective in inhibiting intracellular bacterial growth with limited toxicity to host cells. These compounds are likely to target three kinds of host functions: (i) G protein-coupled receptors, (ii) intracellular calcium signals, and (iii) membrane cholesterol distribution. The compounds that targeted G protein receptor signaling and calcium fluxes broadly inhibited Coxiella burnetii, Legionella pneumophila, Brucella abortus, and Rickettsia conorii, while those directed against cholesterol traffic strongly attenuated the intracellular growth of C. burnetii and L. pneumophila. These pathways probably support intracellular pathogen growth so that drugs that perturb them may be therapeutic candidates. Combining host- and pathogen-directed treatments is a strategy to decrease the emergence of drug-resistant intracellular bacterial pathogens. Importance: Although antibiotic treatment is often successful, it is becoming clear that alternatives to conventional pathogen-directed therapy must be developed in the face of increasing antibiotic resistance. Moreover, the costs and timing associated with the development of novel antimicrobials make repurposed FDA-approved drugs attractive host-targeted therapeutics. This paper describes a novel approach of identifying such host-targeted therapeutics against intracellular bacterial pathogens. We identified several FDA-approved drugs that inhibit the growth of intracellular bacteria, thereby implicating host intracellular pathways presumably utilized by bacteria during infection. Copyright © 2014 Czyż et al.

  5. Barbed micro-spikes for micro-scale biopsy

    Science.gov (United States)

    Byun, Sangwon; Lim, Jung-Min; Paik, Seung-Joon; Lee, Ahra; Koo, Kyo-in; Park, Sunkil; Park, Jaehong; Choi, Byoung-Doo; Seo, Jong Mo; Kim, Kyung-ah; Chung, Hum; Song, Si Young; Jeon, Doyoung; Cho, Dongil

    2005-06-01

    Single-crystal silicon planar micro-spikes with protruding barbs are developed for micro-scale biopsy and the feasibility of using the micro-spike as a micro-scale biopsy tool is evaluated for the first time. The fabrication process utilizes a deep silicon etch to define the micro-spike outline, resulting in protruding barbs of various shapes. Shanks of the fabricated micro-spikes are 3 mm long, 100 µm thick and 250 µm wide. Barbs protruding from micro-spike shanks facilitate the biopsy procedure by tearing off and retaining samples from target tissues. Micro-spikes with barbs successfully extracted tissue samples from the small intestines of the anesthetized pig, whereas micro-spikes without barbs failed to obtain a biopsy sample. Parylene coating can be applied to improve the biocompatibility of the micro-spike without deteriorating the biopsy function of the micro-spike. In addition, to show that the biopsy with the micro-spike can be applied to tissue analysis, samples obtained by micro-spikes were examined using immunofluorescent staining. Nuclei and F-actin of cells which are extracted by the micro-spike from a transwell were clearly visualized by immunofluorescent staining.

  6. The Mutation Frequency in Different Spike Categories in Barley

    DEFF Research Database (Denmark)

    Frydenberg, O.; Doll, Hans; Sandfær, J.

    1964-01-01

    After gamma irradiation of barley seeds, a comparison has been made between the chlorophyll-mutant frequencies in X1 spikes that had multicellular bud meristems in the seeds at the time of treatment (denoted as pre-formed spikes) and X1 spikes having no recognizable meristems at the time...

  7. Thermal impact on spiking properties in Hodgkin–Huxley neuron ...

    Indian Academy of Sciences (India)

    Abstract. The effect of environmental temperature on neuronal spiking behaviors is investigated by numerically simulating the temperature dependence of spiking threshold of the Hodgkin–Huxley neuron subject to synaptic stimulus. We find that the spiking threshold exhibits a global minimum in a specific temperature range ...

  8. Effects of calcium channel on ovarian cancer cells.

    Science.gov (United States)

    Zhang, Chunyun; Li, Hailing

    2017-12-01

    The aim of the present study was to examine the effects of calcium channel protein on ovarian cancer cells. The expression of calcium channel protein in normal ovarian cells and ovarian cancer cells was detected by fluorescence quantitative PCR. Subsequently, the ovarian cancer cells were added to calcium channel protein activator media at various concentrations of 0, 1, 4, 8, 12, 16 and 20 mmol/l. The concentration of calcium ion in different samples was produced, and using an MTT assay, ovarian cancer cell activity in various samples was detected. Finally, a flow cytometer was used to explore the apoptosis rate. It was found that there was a significant difference between the expression of calcium channel protein in normal ovarian tissue and ovarian cancer cells (Pcancer cells to a certain extent, in a dose-dependent manner, especially when the concentration was at 12 mmol/l at which the intracellular calcium concentration was similar to that in normal ovarian cells. In conclusion, calcium ions play an important role in promoting cell proliferation of ovarian cancer cells, and they were involved in apoptosis of ovarian cancer cells to some extent, which regulates apoptosis by controlling the content of intracellular calcium.

  9. Effects of Calcium Ion, Calpains, and Calcium Channel Blockers on Retinitis Pigmentosa

    Directory of Open Access Journals (Sweden)

    Mitsuru Nakazawa

    2011-01-01

    Full Text Available Recent advances in molecular genetic studies have revealed many of the causative genes of retinitis pigmentosa (RP. These achievements have provided clues to the mechanisms of photoreceptor degeneration in RP. Apoptosis is known to be a final common pathway in RP and, therefore, a possible therapeutic target for photoreceptor rescue. However, apoptosis is not a single molecular cascade, but consists of many different reactions such as caspase-dependent and caspase-independent pathways commonly leading to DNA fractionation and cell death. The intracellular concentration of calcium ions is also known to increase in apoptosis. These findings suggest that calpains, one of the calcium-dependent proteinases, play some roles in the process of photoreceptor apoptosis and that calcium channel antagonists may potentially inhibit photoreceptor apoptosis. Herein, the effects of calpains and calcium channel antagonists on photoreceptor degeneration are reviewed.

  10. Spiked instantons from intersecting D-branes

    Directory of Open Access Journals (Sweden)

    Nikita Nekrasov

    2017-01-01

    Full Text Available The moduli space of spiked instantons that arises in the context of the BPS/CFT correspondence [22] is realised as the moduli space of classical vacua, i.e. low-energy open string field configurations, of a certain stack of intersecting D1-branes and D5-branes in Type IIB string theory. The presence of a constant B-field induces an interesting dynamics involving the tachyon condensation.

  11. Non-singular spiked harmonic oscillator

    International Nuclear Information System (INIS)

    Aguilera-Navarro, V.C.; Guardiola, R.

    1990-01-01

    A perturbative study of a class of non-singular spiked harmonic oscillators defined by the hamiltonian H = d sup(2)/dr sup(2) + r sup(2) + λ/r sup(α) in the domain [0,∞] is carried out, in the two extremes of a weak coupling and a strong coupling regimes. A path has been found to connect both expansions for α near 2. (author)

  12. Nuclear Calcium Buffering Capacity Shapes Neuronal Architecture*

    Science.gov (United States)

    Mauceri, Daniela; Hagenston, Anna M.; Schramm, Kathrin; Weiss, Ursula; Bading, Hilmar

    2015-01-01

    Calcium-binding proteins (CaBPs) such as parvalbumin are part of the cellular calcium buffering system that determines intracellular calcium diffusion and influences the spatiotemporal dynamics of calcium signals. In neurons, CaBPs are primarily localized to the cytosol and function, for example, in nerve terminals in short-term synaptic plasticity. However, CaBPs are also expressed in the cell nucleus, suggesting that they modulate nuclear calcium signals, which are key regulators of neuronal gene expression. Here we show that the calcium buffering capacity of the cell nucleus in mouse hippocampal neurons regulates neuronal architecture by modulating the expression levels of VEGFD and the complement factor C1q-c, two nuclear calcium-regulated genes that control dendrite geometry and spine density, respectively. Increasing the levels of nuclear calcium buffers by means of expression of a nuclearly targeted form of parvalbumin fused to mCherry (PV.NLS-mC) led to a reduction in VEGFD expression and, as a result, to a decrease in total dendritic length and complexity. In contrast, mRNA levels of the synapse pruning factor C1q-c were increased in neurons expressing PV.NLS-mC, causing a reduction in the density and size of dendritic spines. Our results establish a close link between nuclear calcium buffering capacity and the transcription of genes that determine neuronal structure. They suggest that the development of cognitive deficits observed in neurological conditions associated with CaBP deregulation may reflect the loss of necessary structural features of dendrites and spines. PMID:26231212

  13. Basalt FRP Spike Repairing of Wood Beams

    Directory of Open Access Journals (Sweden)

    Luca Righetti

    2015-08-01

    Full Text Available This article describes aspects within an experimental program aimed at improving the structural performance of cracked solid fir-wood beams repaired with Basalt Fiber Reinforced Polymer (BFRP spikes. Fir wood is characterized by its low density, low compression strength, and high level of defects, and it is likely to distort when dried and tends to fail under tension due to the presence of cracks, knots, or grain deviation. The proposed repair technique consists of the insertion of BFRP spikes into timber beams to restore the continuity of cracked sections. The experimental efforts deal with the evaluation of the bending strength and deformation properties of 24 timber beams. An artificially simulated cracking was produced by cutting the wood beams in half or notching. The obtained results for the repaired beams were compared with those of solid undamaged and damaged beams, and increases of beam capacity, bending strength and of modulus of elasticity, and analysis of failure modes was discussed. For notched beams, the application of the BFRP spikes was able to restore the original bending capacity of undamaged beams, while only a small part of the original capacity was recovered for beams that were cut in half.

  14. Spiking Neural P Systems With Scheduled Synapses.

    Science.gov (United States)

    Cabarle, Francis George C; Adorna, Henry N; Jiang, Min; Zeng, Xiangxiang

    2017-12-01

    Spiking neural P systems (SN P systems) are models of computation inspired by biological spiking neurons. SN P systems have neurons as spike processors, which are placed on the nodes of a directed and static graph (the edges in the graph are the synapses). In this paper, we introduce a variant called SN P systems with scheduled synapses (SSN P systems). SSN P systems are inspired and motivated by the structural dynamism of biological synapses, while incorporating ideas from nonstatic (i.e., dynamic) graphs and networks. In particular, synapses in SSN P systems are available only at specific durations according to their schedules. The SSN P systems model is a response to the problem of introducing durations to synapses of SN P systems. Since SN P systems are in essence static graphs, it is natural to consider them for dynamic graphs also. We introduce local and global schedule types, also taking inspiration from the above-mentioned sources. We prove that SSN P systems are computationally universal as number generators and acceptors for both schedule types, under a normal form (i.e., a simplifying set of restrictions). The introduction of synapse schedules for either schedule type proves useful in programming the system, despite restrictions in the normal form.

  15. Precise-Spike-Driven Synaptic Plasticity: Learning Hetero-Association of Spatiotemporal Spike Patterns

    Science.gov (United States)

    Yu, Qiang; Tang, Huajin; Tan, Kay Chen; Li, Haizhou

    2013-01-01

    A new learning rule (Precise-Spike-Driven (PSD) Synaptic Plasticity) is proposed for processing and memorizing spatiotemporal patterns. PSD is a supervised learning rule that is analytically derived from the traditional Widrow-Hoff rule and can be used to train neurons to associate an input spatiotemporal spike pattern with a desired spike train. Synaptic adaptation is driven by the error between the desired and the actual output spikes, with positive errors causing long-term potentiation and negative errors causing long-term depression. The amount of modification is proportional to an eligibility trace that is triggered by afferent spikes. The PSD rule is both computationally efficient and biologically plausible. The properties of this learning rule are investigated extensively through experimental simulations, including its learning performance, its generality to different neuron models, its robustness against noisy conditions, its memory capacity, and the effects of its learning parameters. Experimental results show that the PSD rule is capable of spatiotemporal pattern classification, and can even outperform a well studied benchmark algorithm with the proposed relative confidence criterion. The PSD rule is further validated on a practical example of an optical character recognition problem. The results again show that it can achieve a good recognition performance with a proper encoding. Finally, a detailed discussion is provided about the PSD rule and several related algorithms including tempotron, SPAN, Chronotron and ReSuMe. PMID:24223789

  16. Precise-spike-driven synaptic plasticity: learning hetero-association of spatiotemporal spike patterns.

    Directory of Open Access Journals (Sweden)

    Qiang Yu

    Full Text Available A new learning rule (Precise-Spike-Driven (PSD Synaptic Plasticity is proposed for processing and memorizing spatiotemporal patterns. PSD is a supervised learning rule that is analytically derived from the traditional Widrow-Hoff rule and can be used to train neurons to associate an input spatiotemporal spike pattern with a desired spike train. Synaptic adaptation is driven by the error between the desired and the actual output spikes, with positive errors causing long-term potentiation and negative errors causing long-term depression. The amount of modification is proportional to an eligibility trace that is triggered by afferent spikes. The PSD rule is both computationally efficient and biologically plausible. The properties of this learning rule are investigated extensively through experimental simulations, including its learning performance, its generality to different neuron models, its robustness against noisy conditions, its memory capacity, and the effects of its learning parameters. Experimental results show that the PSD rule is capable of spatiotemporal pattern classification, and can even outperform a well studied benchmark algorithm with the proposed relative confidence criterion. The PSD rule is further validated on a practical example of an optical character recognition problem. The results again show that it can achieve a good recognition performance with a proper encoding. Finally, a detailed discussion is provided about the PSD rule and several related algorithms including tempotron, SPAN, Chronotron and ReSuMe.

  17. Precise-spike-driven synaptic plasticity: learning hetero-association of spatiotemporal spike patterns.

    Science.gov (United States)

    Yu, Qiang; Tang, Huajin; Tan, Kay Chen; Li, Haizhou

    2013-01-01

    A new learning rule (Precise-Spike-Driven (PSD) Synaptic Plasticity) is proposed for processing and memorizing spatiotemporal patterns. PSD is a supervised learning rule that is analytically derived from the traditional Widrow-Hoff rule and can be used to train neurons to associate an input spatiotemporal spike pattern with a desired spike train. Synaptic adaptation is driven by the error between the desired and the actual output spikes, with positive errors causing long-term potentiation and negative errors causing long-term depression. The amount of modification is proportional to an eligibility trace that is triggered by afferent spikes. The PSD rule is both computationally efficient and biologically plausible. The properties of this learning rule are investigated extensively through experimental simulations, including its learning performance, its generality to different neuron models, its robustness against noisy conditions, its memory capacity, and the effects of its learning parameters. Experimental results show that the PSD rule is capable of spatiotemporal pattern classification, and can even outperform a well studied benchmark algorithm with the proposed relative confidence criterion. The PSD rule is further validated on a practical example of an optical character recognition problem. The results again show that it can achieve a good recognition performance with a proper encoding. Finally, a detailed discussion is provided about the PSD rule and several related algorithms including tempotron, SPAN, Chronotron and ReSuMe.

  18. Nicotine-Mediated ADP to Spike Transition: Double Spiking in Septal Neurons.

    Science.gov (United States)

    Kodirov, Sodikdjon A; Wehrmeister, Michael; Colom, Luis

    2016-04-01

    The majority of neurons in lateral septum (LS) are electrically silent at resting membrane potential. Nicotine transiently excites a subset of neurons and occasionally leads to long lasting bursting activity upon longer applications. We have observed simultaneous changes in frequencies and amplitudes of spontaneous action potentials (AP) in the presence of nicotine. During the prolonged exposure, nicotine increased numbers of spikes within a burst. One of the hallmarks of nicotine effects was the occurrences of double spikes (known also as bursting). Alignment of 51 spontaneous spikes, triggered upon continuous application of nicotine, revealed that the slope of after-depolarizing potential gradually increased (1.4 vs. 3 mV/ms) and neuron fired the second AP, termed as double spiking. A transition from a single AP to double spikes increased the amplitude of after-hyperpolarizing potential. The amplitude of the second (premature) AP was smaller compared to the first one, and this correlation persisted in regard to their duration (half-width). A similar bursting activity in the presence of nicotine, to our knowledge, has not been reported previously in the septal structure in general and in LS in particular.

  19. Induction of epithelial-mesenchymal transition (EMT) in breast cancer cells is calcium signal dependent.

    Science.gov (United States)

    Davis, F M; Azimi, I; Faville, R A; Peters, A A; Jalink, K; Putney, J W; Goodhill, G J; Thompson, E W; Roberts-Thomson, S J; Monteith, G R

    2014-05-01

    Signals from the tumor microenvironment trigger cancer cells to adopt an invasive phenotype through epithelial-mesenchymal transition (EMT). Relatively little is known regarding key signal transduction pathways that serve as cytosolic bridges between cell surface receptors and nuclear transcription factors to induce EMT. A better understanding of these early EMT events may identify potential targets for the control of metastasis. One rapid intracellular signaling pathway that has not yet been explored during EMT induction is calcium. Here we show that stimuli used to induce EMT produce a transient increase in cytosolic calcium levels in human breast cancer cells. Attenuation of the calcium signal by intracellular calcium chelation significantly reduced epidermal growth factor (EGF)- and hypoxia-induced EMT. Intracellular calcium chelation also inhibited EGF-induced activation of signal transducer and activator of transcription 3 (STAT3), while preserving other signal transduction pathways such as Akt and extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation. To identify calcium-permeable channels that may regulate EMT induction in breast cancer cells, we performed a targeted siRNA-based screen. We found that transient receptor potential-melastatin-like 7 (TRPM7) channel expression regulated EGF-induced STAT3 phosphorylation and expression of the EMT marker vimentin. Although intracellular calcium chelation almost completely blocked the induction of many EMT markers, including vimentin, Twist and N-cadherin, the effect of TRPM7 silencing was specific for vimentin protein expression and STAT3 phosphorylation. These results indicate that TRPM7 is a partial regulator of EMT in breast cancer cells, and that other calcium-permeable ion channels are also involved in calcium-dependent EMT induction. In summary, this work establishes an important role for the intracellular calcium signal in the induction of EMT in human breast cancer cells. Manipulation of

  20. Calcium D-saccharate

    DEFF Research Database (Denmark)

    Garcia, André Castilho; Hedegaard, Martina Vavrusova; Skibsted, Leif Horsfelt

    2016-01-01

    -saccharate becomes spontaneously supersaturated with both d-gluconate and d-saccharate calcium salts, from which only calcium d-saccharate slowly precipitates. Calcium d-saccharate is suggested to act as a stabilizer of supersaturated solutions of other calcium hydroxycarboxylates with endothermic complex formation......Molar conductivity of saturated aqueous solutions of calcium d-saccharate, used as a stabilizer of beverages fortified with calcium d-gluconate, increases strongly upon dilution, indicating complex formation between calcium and d-saccharate ions, for which, at 25 °C, Kassoc = 1032 ± 80, ΔHassoc...

  1. Synchronous spikes are necessary but not sufficient for a synchrony code in populations of spiking neurons.

    Science.gov (United States)

    Grewe, Jan; Kruscha, Alexandra; Lindner, Benjamin; Benda, Jan

    2017-03-07

    Synchronous activity in populations of neurons potentially encodes special stimulus features. Selective readout of either synchronous or asynchronous activity allows formation of two streams of information processing. Theoretical work predicts that such a synchrony code is a fundamental feature of populations of spiking neurons if they operate in specific noise and stimulus regimes. Here we experimentally test the theoretical predictions by quantifying and comparing neuronal response properties in tuberous and ampullary electroreceptor afferents of the weakly electric fish Apteronotus leptorhynchus These related systems show similar levels of synchronous activity, but only in the more irregularly firing tuberous afferents a synchrony code is established, whereas in the more regularly firing ampullary afferents it is not. The mere existence of synchronous activity is thus not sufficient for a synchrony code. Single-cell features such as the irregularity of spiking and the frequency dependence of the neuron's transfer function determine whether synchronous spikes possess a distinct meaning for the encoding of time-dependent signals.

  2. Comparison of electrodialytic removal of Cu from spiked kaolinite, spiked soil and industrially polluted soil

    DEFF Research Database (Denmark)

    Ottosen, Lisbeth M.; Lepkova, Katarina; Kubal, Martin

    2006-01-01

    Electrokinetic remediation methods for removal of heavy metals from polluted soils have been subjected for quite intense research during the past years since these methods are well suitable for fine-grained soils where other remediation methods fail. Electrodialytic remediation is an electrokinetic...... remediation method which is based on applying an electric DC field and the use of ion exchange membranes that ensures the main transport of heavy metals to be out of the pollutes soil. An experimental investigation was made with electrodialytic removal of Cu from spiked kaolinite, spiked soil and industrially...... polluted soil under the same operational conditions (constant current density 0.2 mA/cm2 and duration 28 days). The results of the present paper show that caution must be taken when generalising results obtained in spiked kaolinite to remediation of industrially polluted soils, as it was shown...

  3. Calcium signals driven by single channel noise.

    Directory of Open Access Journals (Sweden)

    Alexander Skupin

    Full Text Available Usually, the occurrence of random cell behavior is appointed to small copy numbers of molecules involved in the stochastic process. Recently, we demonstrated for a variety of cell types that intracellular Ca2+ oscillations are sequences of random spikes despite the involvement of many molecules in spike generation. This randomness arises from the stochastic state transitions of individual Ca2+ release channels and does not average out due to the existence of steep concentration gradients. The system is hierarchical due to the structural levels channel--channel cluster--cell and a corresponding strength of coupling. Concentration gradients introduce microdomains which couple channels of a cluster strongly. But they couple clusters only weakly; too weak to establish deterministic behavior on cell level. Here, we present a multi-scale modelling concept for stochastic hierarchical systems. It simulates active molecules individually as Markov chains and their coupling by deterministic diffusion. Thus, we are able to follow the consequences of random single molecule state changes up to the signal on cell level. To demonstrate the potential of the method, we simulate a variety of experiments. Comparisons of simulated and experimental data of spontaneous oscillations in astrocytes emphasize the role of spatial concentration gradients in Ca2+ signalling. Analysis of extensive simulations indicates that frequency encoding described by the relation between average and standard deviation of interspike intervals is surprisingly robust. This robustness is a property of the random spiking mechanism and not a result of control.

  4. Calcium signals driven by single channel noise.

    Science.gov (United States)

    Skupin, Alexander; Kettenmann, Helmut; Falcke, Martin

    2010-08-05

    Usually, the occurrence of random cell behavior is appointed to small copy numbers of molecules involved in the stochastic process. Recently, we demonstrated for a variety of cell types that intracellular Ca2+ oscillations are sequences of random spikes despite the involvement of many molecules in spike generation. This randomness arises from the stochastic state transitions of individual Ca2+ release channels and does not average out due to the existence of steep concentration gradients. The system is hierarchical due to the structural levels channel--channel cluster--cell and a corresponding strength of coupling. Concentration gradients introduce microdomains which couple channels of a cluster strongly. But they couple clusters only weakly; too weak to establish deterministic behavior on cell level. Here, we present a multi-scale modelling concept for stochastic hierarchical systems. It simulates active molecules individually as Markov chains and their coupling by deterministic diffusion. Thus, we are able to follow the consequences of random single molecule state changes up to the signal on cell level. To demonstrate the potential of the method, we simulate a variety of experiments. Comparisons of simulated and experimental data of spontaneous oscillations in astrocytes emphasize the role of spatial concentration gradients in Ca2+ signalling. Analysis of extensive simulations indicates that frequency encoding described by the relation between average and standard deviation of interspike intervals is surprisingly robust. This robustness is a property of the random spiking mechanism and not a result of control.

  5. Protein kinase C interaction with calcium: a phospholipid-dependent process.

    LENUS (Irish Health Repository)

    Bazzi, M D

    1990-08-21

    The calcium-binding properties of calcium- and phospholipid-dependent protein kinase C (PKC) were investigated by equilibrium dialysis in the presence and the absence of phospholipids. Calcium binding to PKC displayed striking and unexpected behavior; the free proteins bound virtually no calcium at intracellular calcium concentrations and bound limited calcium (about 1 mol\\/mol of PKC) at 200 microM calcium. However, in the presence of membranes containing acidic phospholipids, PKC bound at least eight calcium ions per protein. The presence of 1 microM phorbol dibutyrate (PDBu) in the dialysis buffer had little effect on these calcium-binding properties. Analysis of PKC-calcium binding by gel filtration under equilibrium conditions gave similar results; only membrane-associated PKC bound significant amounts of calcium. Consequently, PKC is a member of what may be a large group of proteins that bind calcium in a phospholipid-dependent manner. The calcium concentrations needed to induce PKC-membrane binding were similar to those needed for calcium binding (about 40 microM calcium at the midpoint). However, the calcium concentration required for PKC-membrane binding was strongly influenced by the phosphatidylserine composition of the membranes. Membranes with higher percentages of phosphatidylserine required lower concentrations of calcium. These properties suggested that the calcium sites may be generated at the interface between PKC and the membrane. Calcium may function as a bridge between PKC and phospholipids. These studies also suggested that calcium-dependent PKC-membrane binding and PKC function could be regulated by a number of factors in addition to calcium levels and diacylglycerol content of the membrane.

  6. Diallel analysis to study the genetic makeup of spike and yield ...

    African Journals Online (AJOL)

    Five wheat genotypes were crossed in complete diallel fashion for gene action studies of spike length, spikelets per spike, grains per spike, grain weight per spike ... High magnitude of narrow sense heritability (h2n.s) was noticed for spikelets per spike (79%), and grains per spike (88%) thus illustrated fixable and additive ...

  7. Solving constraint satisfaction problems with networks of spiking neurons

    Directory of Open Access Journals (Sweden)

    Zeno eJonke

    2016-03-01

    Full Text Available Network of neurons in the brain apply – unlike processors in our current generation ofcomputer hardware – an event-based processing strategy, where short pulses (spikes areemitted sparsely by neurons to signal the occurrence of an event at a particular point intime. Such spike-based computations promise to be substantially more power-efficient thantraditional clocked processing schemes. However it turned out to be surprisingly difficult todesign networks of spiking neurons that can solve difficult computational problems on the levelof single spikes (rather than rates of spikes. We present here a new method for designingnetworks of spiking neurons via an energy function. Furthermore we show how the energyfunction of a network of stochastically firing neurons can be shaped in a quite transparentmanner by composing the networks of simple stereotypical network motifs. We show that thisdesign approach enables networks of spiking neurons to produce approximate solutions todifficult (NP-hard constraint satisfaction problems from the domains of planning/optimizationand verification/logical inference. The resulting networks employ noise as a computationalresource. Nevertheless the timing of spikes (rather than just spike rates plays an essential rolein their computations. Furthermore, networks of spiking neurons carry out for the Traveling Salesman Problem a more efficient stochastic search for good solutions compared with stochastic artificial neural networks (Boltzmann machines and Gibbs sampling.

  8. Calcium-regulated import of myosin IC into the nucleus.

    Science.gov (United States)

    Maly, Ivan V; Hofmann, Wilma A

    2016-06-01

    Myosin IC is a molecular motor involved in intracellular transport, cell motility, and transcription. Its mechanical properties are regulated by calcium via calmodulin binding, and its functions in the nucleus depend on import from the cytoplasm. The import has recently been shown to be mediated by the nuclear localization signal located within the calmodulin-binding domain. In the present paper, it is demonstrated that mutations in the calmodulin-binding sequence shift the intracellular distribution of myosin IC to the nucleus. The redistribution is displayed by isoform B, described originally as the "nuclear myosin," but is particularly pronounced with isoform C, the normally cytoplasmic isoform. Furthermore, experimental elevation of the intracellular calcium concentration induces a rapid import of myosin into the nucleus. The import is blocked by the importin β inhibitor importazole. These findings are consistent with a mechanism whereby calmodulin binding prevents recognition of the nuclear localization sequence by importin β, and the steric inhibition of import is released by cell signaling leading to the intracellular calcium elevation. The results establish a mechanistic connection between the calcium regulation of the motor function of myosin IC in the cytoplasm and the induction of its import into the nucleus. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  9. Serum Calcium Level is Associated with Lipids in Young Nigerian ...

    African Journals Online (AJOL)

    associated with high blood pressure in a representative sample of United States of American adults without cardiovascular diseases (CVDs) which was independent of age, sex, race, alcohol, smoking, diabetes, lipids, serum albumin, serum vitamin D and phosphorus.[23]. Calcium is an important intracellular messenger ...

  10. Calcium Signaling and Meiotic Exit at Fertilization in Xenopus Egg

    Science.gov (United States)

    Tokmakov, Alexander A.; Stefanov, Vasily E.; Iwasaki, Tetsushi; Sato, Ken-Ichi; Fukami, Yasuo

    2014-01-01

    Calcium is a universal messenger that mediates egg activation at fertilization in all sexually reproducing species studied. However, signaling pathways leading to calcium generation and the mechanisms of calcium-induced exit from meiotic arrest vary substantially among species. Here, we review the pathways of calcium signaling and the mechanisms of meiotic exit at fertilization in the eggs of the established developmental model, African clawed frog, Xenopus laevis. We also discuss calcium involvement in the early fertilization-induced events in Xenopus egg, such as membrane depolarization, the increase in intracellular pH, cortical granule exocytosis, cortical contraction, contraction wave, cortical rotation, reformation of the nuclear envelope, sperm chromatin decondensation and sister chromatid segregation. PMID:25322156

  11. A potential calcium antagonist and its antihypertensive effects.

    Science.gov (United States)

    Zhang, Yan; Cao, YanJun; Wang, QunLi; Zheng, Lei; Zhang, Jie; He, LangChong

    2011-10-01

    Imperatorin (Imp) as a hypotensive active ingredient, its hypotensive effect was evaluated in the SHRs, its calcium antagonism and affinity to L-type calcium channel was also confirmed. The results showed that the blood pressure was decreased in the SHRs treated with Imp, the aortic ring was relaxed with Imp, L-type calcium channel currents and intracellular calcium free ion rise was nearly disappeared when adding Imp. In addition, Imp displayed a chromatographic peak similar to nitrendipine and verapamil by the cell membrane chromatography, same results from protein-drug docking approaches. Hence, Imp target the L-type calcium channel, and may be used as a novel antihypertensive drug. Copyright © 2011 Elsevier B.V. All rights reserved.

  12. An anaphase calcium signal controls chromosome disjunction in early sea urchin embryos.

    Science.gov (United States)

    Groigno, L; Whitaker, M

    1998-01-23

    A transient increase in intracellular calcium concentration [Ca2+]i occurs throughout the cell as sea urchin embryos enter anaphase of the first cell cycle. The transient just precedes chromatid disjunction and spindle elongation. Microinjection of calcium chelators or heparin, an InsP3 receptor antagonist, blocks chromosome separation. Photorelease of calcium or InsP3 can reverse the block. Nuclear reformation is merely delayed by calcium antagonists at concentrations that block chromatid separation. Thus, the calcium signal triggers the separation of chromatids, while calcium-independent pathways can bring about the alterations in microtubule dynamics and nuclear events associated with anaphase progression. That calcium triggers chromosome disjunction alone is unexpected. It helps explain previous conflicting results and allows the prediction that calcium plays a similar role at anaphase in other cell types.

  13. Divergent calcium signaling in RBCs from Tropidurus torquatus (Squamata – Tropiduridae strengthen classification in lizard evolution

    Directory of Open Access Journals (Sweden)

    Garcia Célia RS

    2007-08-01

    Full Text Available Abstract Background We have previously reported that a Teiid lizard red blood cells (RBCs such as Ameiva ameiva and Tupinambis merianae controls intracellular calcium levels by displaying multiple mechanisms. In these cells, calcium stores could be discharged not only by: thapsigargin, but also by the Na+/H+ ionophore monensin, K+/H+ ionophore nigericin and the H+ pump inhibitor bafilomycin as well as ionomycin. Moreover, these lizards possess a P2Y-type purinoceptors that mobilize Ca2+ from intracellular stores upon ATP addition. Results Here we report, that RBCs from the tropidurid lizard Tropidurus torquatus store Ca2+ in endoplasmic reticulum (ER pool but unlike in the referred Teiidae, these cells do not store calcium in monensin-nigericin sensitive pools. Moreover, mitochondria from T. torquatus RBCs accumulate Ca2+. Addition of ATP to a calcium-free medium does not increase the [Ca2+]c levels, however in a calcium medium we observe an increase in cytosolic calcium. This is an indication that purinergic receptors in these cells are P2X-like. Conclusion T. torquatus RBCs present different mechanisms from Teiid lizard red blood cells (RBCs, for controlling its intracellular calcium levels. At T. torquatus the ion is only stored at endoplasmic reticulum and mitochondria. Moreover activation of purinergic receptor, P2X type, was able to induce an influx of calcium from extracelullar medium. These studies contribute to the understanding of the evolution of calcium homeostasis and signaling in nucleated RBCs.

  14. The central role of calcium in the effects of cytokines on beta-cell function: implications for type 1 and type 2 diabetes.

    Science.gov (United States)

    Ramadan, James W; Steiner, Stephen R; O'Neill, Christina M; Nunemaker, Craig S

    2011-12-01

    The appropriate regulation of intracellular calcium is a requirement for proper cell function and survival. This review focuses on the effects of proinflammatory cytokines on calcium regulation in the insulin-producing pancreatic beta-cell and how normal stimulus-secretion coupling, organelle function, and overall beta-cell viability are impacted. Proinflammatory cytokines are increasingly thought to contribute to beta-cell dysfunction not only in type 1 diabetes (T1D), but also in the progression of type 2 diabetes (T2D). Cytokine-induced disruptions in calcium handling result in reduced insulin release in response to glucose stimulation. Cytokines can alter intracellular calcium levels by depleting calcium from the endoplasmic reticulum (ER) and by increasing calcium influx from the extracellular space. Depleting ER calcium leads to protein misfolding and activation of the ER stress response. Disrupting intracellular calcium may also affect organelles, including the mitochondria and the nucleus. As a chronic condition, cytokine-induced calcium disruptions may lead to beta-cell death in T1D and T2D, although possible protective effects are also discussed. Calcium is thus central to both normal and pathological cell processes. Because the tight regulation of intracellular calcium is crucial to homeostasis, measuring the dynamics of calcium may serve as a good indicator of overall beta-cell function. Copyright © 2011 Elsevier Ltd. All rights reserved.

  15. Spike-timing-dependent learning rule to encode spatiotemporal patterns in a network of spiking neurons

    Science.gov (United States)

    Yoshioka, Masahiko

    2002-01-01

    We study associative memory neural networks based on the Hodgkin-Huxley type of spiking neurons. We introduce the spike-timing-dependent learning rule, in which the time window with the negative part as well as the positive part is used to describe the biologically plausible synaptic plasticity. The learning rule is applied to encode a number of periodical spatiotemporal patterns, which are successfully reproduced in the periodical firing pattern of spiking neurons in the process of memory retrieval. The global inhibition is incorporated into the model so as to induce the gamma oscillation. The occurrence of gamma oscillation turns out to give appropriate spike timings for memory retrieval of discrete type of spatiotemporal pattern. The theoretical analysis to elucidate the stationary properties of perfect retrieval state is conducted in the limit of an infinite number of neurons and shows the good agreement with the result of numerical simulations. The result of this analysis indicates that the presence of the negative and positive parts in the form of the time window contributes to reduce the size of crosstalk term, implying that the time window with the negative and positive parts is suitable to encode a number of spatiotemporal patterns. We draw some phase diagrams, in which we find various types of phase transitions with change of the intensity of global inhibition.

  16. Spike Pattern Recognition for Automatic Collimation Alignment

    CERN Document Server

    Azzopardi, Gabriella; Salvachua Ferrando, Belen Maria; Mereghetti, Alessio; Redaelli, Stefano; CERN. Geneva. ATS Department

    2017-01-01

    The LHC makes use of a collimation system to protect its sensitive equipment by intercepting potentially dangerous beam halo particles. The appropriate collimator settings to protect the machine against beam losses relies on a very precise alignment of all the collimators with respect to the beam. The beam center at each collimator is then found by touching the beam halo using an alignment procedure. Until now, in order to determine whether a collimator is aligned with the beam or not, a user is required to follow the collimator’s BLM loss data and detect spikes. A machine learning (ML) model was trained in order to automatically recognize spikes when a collimator is aligned. The model was loosely integrated with the alignment implementation to determine the classification performance and reliability, without effecting the alignment process itself. The model was tested on a number of collimators during this MD and the machine learning was able to output the classifications in real-time.

  17. Eliminating thermal violin spikes from LIGO noise

    Energy Technology Data Exchange (ETDEWEB)

    Santamore, D. H.; Levin, Yuri

    2001-08-15

    We have developed a scheme for reducing LIGO suspension thermal noise close to violin-mode resonances. The idea is to monitor directly the thermally induced motion of a small portion of (a 'point' on) each suspension fiber, thereby recording the random forces driving the test-mass motion close to each violin-mode frequency. One can then suppress the thermal noise by optimally subtracting the recorded fiber motions from the measured motion of the test mass, i.e., from the LIGO output. The proposed method is a modification of an analogous but more technically difficult scheme by Braginsky, Levin and Vyatchanin for reducing broad-band suspension thermal noise. The efficiency of our method is limited by the sensitivity of the sensor used to monitor the fiber motion. If the sensor has no intrinsic noise (i.e. has unlimited sensitivity), then our method allows, in principle, a complete removal of violin spikes from the thermal-noise spectrum. We find that in LIGO-II interferometers, in order to suppress violin spikes below the shot-noise level, the intrinsic noise of the sensor must be less than {approx}2 x 10{sup -13} cm/Hz. This sensitivity is two orders of magnitude greater than that of currently available sensors.

  18. Eliminating thermal violin spikes from LIGO noise

    International Nuclear Information System (INIS)

    Santamore, D. H.; Levin, Yuri

    2001-01-01

    We have developed a scheme for reducing LIGO suspension thermal noise close to violin-mode resonances. The idea is to monitor directly the thermally induced motion of a small portion of (a 'point' on) each suspension fiber, thereby recording the random forces driving the test-mass motion close to each violin-mode frequency. One can then suppress the thermal noise by optimally subtracting the recorded fiber motions from the measured motion of the test mass, i.e., from the LIGO output. The proposed method is a modification of an analogous but more technically difficult scheme by Braginsky, Levin and Vyatchanin for reducing broad-band suspension thermal noise. The efficiency of our method is limited by the sensitivity of the sensor used to monitor the fiber motion. If the sensor has no intrinsic noise (i.e. has unlimited sensitivity), then our method allows, in principle, a complete removal of violin spikes from the thermal-noise spectrum. We find that in LIGO-II interferometers, in order to suppress violin spikes below the shot-noise level, the intrinsic noise of the sensor must be less than ∼2 x 10 -13 cm/Hz. This sensitivity is two orders of magnitude greater than that of currently available sensors

  19. Phase Diagram of Spiking Neural Networks

    Directory of Open Access Journals (Sweden)

    Hamed eSeyed-Allaei

    2015-03-01

    Full Text Available In computer simulations of spiking neural networks, often it is assumed that every two neurons of the network are connected by a probablilty of 2%, 20% of neurons are inhibitory and 80% are excitatory. These common values are based on experiments, observations. but here, I take a different perspective, inspired by evolution. I simulate many networks, each with a different set of parameters, and then I try to figure out what makes the common values desirable by nature. Networks which are configured according to the common values, have the best dynamic range in response to an impulse and their dynamic range is more robust in respect to synaptic weights. In fact, evolution has favored networks of best dynamic range. I present a phase diagram that shows the dynamic ranges of different networks of different parameteres. This phase diagram gives an insight into the space of parameters -- excitatory to inhibitory ratio, sparseness of connections and synaptic weights. It may serve as a guideline to decide about the values of parameters in a simulation of spiking neural network.

  20. Spiking Neural Network in Precision Agriculture

    Directory of Open Access Journals (Sweden)

    Nadia Adnan Shiltagh

    2015-07-01

    Full Text Available In this paper, precision agriculture system is introduced based on Wireless Sensor Network (WSN. Soil moisture considered one of environment factors that effect on crop. The period of irrigation must be monitored. Neural network capable of learning the behavior of the agricultural soil in absence of mathematical model. This paper introduced modified type of neural network that is known as Spiking Neural Network (SNN. In this work, the precision agriculture system is modeled, contains two SNNs which have been identified off-line based on logged data, one of these SNNs represents the monitor that located at sink where the period of irrigation is calculated and the other represents the soil. In addition, to reduce power consumption of sensor nodes Modified Chain-Cluster based Mixed (MCCM routing algorithm is used. According to MCCM, the sensors will send their packets that are less than threshold moisture level to the sink. The SNN with Modified Spike-Prop (MSP training algorithm is capable of identifying soil, irrigation periods and monitoring the soil moisture level, this means that SNN has the ability to be an identifier and monitor. By applying this system the particular agriculture area reaches to the desired moisture level.

  1. A new supervised learning algorithm for spiking neurons.

    Science.gov (United States)

    Xu, Yan; Zeng, Xiaoqin; Zhong, Shuiming

    2013-06-01

    The purpose of supervised learning with temporal encoding for spiking neurons is to make the neurons emit a specific spike train encoded by the precise firing times of spikes. If only running time is considered, the supervised learning for a spiking neuron is equivalent to distinguishing the times of desired output spikes and the other time during the running process of the neuron through adjusting synaptic weights, which can be regarded as a classification problem. Based on this idea, this letter proposes a new supervised learning method for spiking neurons with temporal encoding; it first transforms the supervised learning into a classification problem and then solves the problem by using the perceptron learning rule. The experiment results show that the proposed method has higher learning accuracy and efficiency over the existing learning methods, so it is more powerful for solving complex and real-time problems.

  2. Effects of Spike Anticipation on the Spiking Dynamics of Neural Networks

    Directory of Open Access Journals (Sweden)

    Daniel ede Santos-Sierra

    2015-11-01

    Full Text Available Synchronization is one of the central phenomena involved in information processing in living systems. It is known that the nervous system requires the coordinated activity of both local and distant neural populations. Such an interplay allows to merge different information modalities in a whole processing supporting high-level mental skills as understanding, memory, abstraction, etc. Though the biological processes underlying synchronization in the brain are not fully understood there have been reported a variety of mechanisms supporting different types of synchronization both at theoretical and experimental level. One of the more intriguing of these phenomena is the anticipating synchronization, which has been recently reported in a pair of unidirectionally coupled artificial neurons under simple conditions cite{Pyragas}, where the slave neuron is able to anticipate in time the behaviour of the master one. In this paper we explore the effect of spike anticipation over the information processing performed by a neural network at functional and structural level. We show that the introduction of intermediary neurons in the network enhances spike anticipation and analyse how these variations in spike anticipation can significantly change the firing regime of the neural network according to its functional and structural properties. In addition we show that the interspike interval (ISI, one of the main features of the neural response associated to the information coding, can be closely related to spike anticipation by each spike, and how synaptic plasticity can be modulated through that relationship. This study has been performed through numerical simulation of a coupled system of Hindmarsh-Rose neurons.

  3. Stochastic models of intracellular transport

    KAUST Repository

    Bressloff, Paul C.

    2013-01-09

    The interior of a living cell is a crowded, heterogenuous, fluctuating environment. Hence, a major challenge in modeling intracellular transport is to analyze stochastic processes within complex environments. Broadly speaking, there are two basic mechanisms for intracellular transport: passive diffusion and motor-driven active transport. Diffusive transport can be formulated in terms of the motion of an overdamped Brownian particle. On the other hand, active transport requires chemical energy, usually in the form of adenosine triphosphate hydrolysis, and can be direction specific, allowing biomolecules to be transported long distances; this is particularly important in neurons due to their complex geometry. In this review a wide range of analytical methods and models of intracellular transport is presented. In the case of diffusive transport, narrow escape problems, diffusion to a small target, confined and single-file diffusion, homogenization theory, and fractional diffusion are considered. In the case of active transport, Brownian ratchets, random walk models, exclusion processes, random intermittent search processes, quasi-steady-state reduction methods, and mean-field approximations are considered. Applications include receptor trafficking, axonal transport, membrane diffusion, nuclear transport, protein-DNA interactions, virus trafficking, and the self-organization of subcellular structures. © 2013 American Physical Society.

  4. A mathematical model of T lymphocyte calcium dynamics derived from single transmembrane protein properties

    Directory of Open Access Journals (Sweden)

    Christine Dorothee Schmeitz

    2013-09-01

    Full Text Available Fate decision processes of T lymphocytes are crucial for health and disease. Whether a T lymphocyte is activated, divides, gets anergic or initiates apoptosis depends on extracellular triggers and intracellular signalling. Free cytosolic calcium dynamics plays an important role in this context. The relative contributions of store-derived calcium entry and calcium entry from extracellular space to T lymphocyte activation are still a matter of debate. Here we develop a quantitative mathematical model of T lymphocyte calcium dynamics in order to establish a tool which allows to disentangle cause-effect relationships between ion fluxes and observed calcium time courses. The model is based on single transmembrane protein characteristics which have been determined in independent experiments. This reduces the number of unknown parameters in the model to a minimum and ensures the predictive power of the model. Simulation results are subsequently used for an analysis of whole cell calcium dynamics measured under various experimental conditions. The model accounts for a variety of these conditions, which supports the suitability of the modelling approach. The simulation results suggest a model in which calcium dynamics dominantly relies on the opening of channels in calcium stores while calcium entry through calcium-release activated channels (CRAC is more associated with the maintenance of the T lymphocyte calcium levels and prevents the cell from calcium depletion. Our findings indicate that CRAC guarantees a long-term stable calcium level which is required for cell survival and sustained calcium enhancement.

  5. Calcium versus strontium handling by the heart muscle.

    Science.gov (United States)

    Hendrych, Michal; Olejnickova, Veronika; Novakova, Marie

    2016-01-01

    Calcium plays a crucial role in numerous processes in living systems, from both intracellular and intercellular signalling to blood clotting. Calcium can be replaced by strontium in various intracellular processes due to high level of their similarity and strontium thus may serve as a valuable tool for different experimental studies. On the other hand, strontium is also used in clinical medicine and is commonly taken to the human body with food and water. The negative cardiac side effects of strontium therapy of osteoporosis and bone metastases are well known, but still not fully explained. This fact explains enhanced interest in this element and its impact on human body. This article reviews effects of calcium and strontium on several biochemical and physiological processes, with special emphasis on cardiac muscle.

  6. Multimodal imaging of spike propagation: a technical case report.

    Science.gov (United States)

    Tanaka, N; Grant, P E; Suzuki, N; Madsen, J R; Bergin, A M; Hämäläinen, M S; Stufflebeam, S M

    2012-06-01

    We report an 11-year-old boy with intractable epilepsy, who had cortical dysplasia in the right superior frontal gyrus. Spatiotemporal source analysis of MEG and EEG spikes demonstrated a similar time course of spike propagation from the superior to inferior frontal gyri, as observed on intracranial EEG. The tractography reconstructed from DTI showed a fiber connection between these areas. Our multimodal approach demonstrates spike propagation and a white matter tract guiding the propagation.

  7. Spike timing precision in the visual front-end

    OpenAIRE

    Borghuis, B.G. (Bart Gerard)

    2003-01-01

    This thesis describes a series of investigations into the reliability of neural responses in the primary visual pathway. The results described in subsequent chapters are primarily based on extracellular recordings from single neurons in anaesthetized cats and area MT of an awake monkey, and computational model analysis. Comparison of spike timing precision in recorded and Poisson-simulated spike trains shows that spike timing in the front-end visual system is considerably more precise than on...

  8. Spike sorting for polytrodes: a divide and conquer approach

    OpenAIRE

    Swindale, Nicholas V.; Spacek, Martin A.

    2014-01-01

    In order to determine patterns of neural activity, spike signals recorded by extracellular electrodes have to be clustered (sorted) with the aim of ensuring that each cluster represents all the spikes generated by an individual neuron. Many methods for spike sorting have been proposed but few are easily applicable to recordings from polytrodes which may have 16 or more recording sites. As with tetrodes, these are spaced sufficiently closely that signals from single neurons will usually be rec...

  9. Calcium Channel Blockers

    Science.gov (United States)

    ... conditions, such as Raynaud's disease For people of African heritage and older people, calcium channel blockers might ... high-blood-pressure/in-depth/calcium-channel-blockers/ART-20047605 . Mayo Clinic Footer Legal Conditions and Terms ...

  10. The Severe Acute Respiratory Syndrome (SARS-coronavirus 3a protein may function as a modulator of the trafficking properties of the spike protein

    Directory of Open Access Journals (Sweden)

    Tan Yee-Joo

    2005-02-01

    Full Text Available Abstract Background A recent publication reported that a tyrosine-dependent sorting signal, present in cytoplasmic tail of the spike protein of most coronaviruses, mediates the intracellular retention of the spike protein. This motif is missing from the spike protein of the severe acute respiratory syndrome-coronavirus (SARS-CoV, resulting in high level of surface expression of the spike protein when it is expressed on its own in vitro. Presentation of the hypothesis It has been shown that the severe acute respiratory syndrome-coronavirus genome contains open reading frames that encode for proteins with no homologue in other coronaviruses. One of them is the 3a protein, which is expressed during infection in vitro and in vivo. The 3a protein, which contains a tyrosine-dependent sorting signal in its cytoplasmic domain, is expressed on the cell surface and can undergo internalization. In addition, 3a can bind to the spike protein and through this interaction, it may be able to cause the spike protein to become internalized, resulting in a decrease in its surface expression. Testing the hypothesis The effects of 3a on the internalization of cell surface spike protein can be examined biochemically and the significance of the interplay between these two viral proteins during viral infection can be studied using reverse genetics methodology. Implication of the hypothesis If this hypothesis is proven, it will indicate that the severe acute respiratory syndrome-coronavirus modulates the surface expression of the spike protein via a different mechanism from other coronaviruses. The interaction between 3a and S, which are expressed from separate subgenomic RNA, would be important for controlling the trafficking properties of S. The cell surface expression of S in infected cells significantly impacts viral assembly, viral spread and viral pathogenesis. Modulation by this unique pathway could confer certain advantages during the replication of the severe

  11. AMORE Mo-99 Spike Test Results

    Energy Technology Data Exchange (ETDEWEB)

    Youker, Amanda J. [Argonne National Lab. (ANL), Argonne, IL (United States); Krebs, John F. [Argonne National Lab. (ANL), Argonne, IL (United States); Quigley, Kevin J. [Argonne National Lab. (ANL), Argonne, IL (United States); Byrnes, James P. [Argonne National Lab. (ANL), Argonne, IL (United States); Rotsch, David A [Argonne National Lab. (ANL), Argonne, IL (United States); Brossard, Thomas [Argonne National Lab. (ANL), Argonne, IL (United States); Wesolowski, Kenneth [Argonne National Lab. (ANL), Argonne, IL (United States); Alford, Kurt [Argonne National Lab. (ANL), Argonne, IL (United States); Chemerisov, Sergey [Argonne National Lab. (ANL), Argonne, IL (United States); Vandegrift, George F. [Argonne National Lab. (ANL), Argonne, IL (United States)

    2017-09-27

    With funding from the National Nuclear Security Administrations Material Management and Minimization Office, Argonne National Laboratory (Argonne) is providing technical assistance to help accelerate the U.S. production of Mo-99 using a non-highly enriched uranium (non-HEU) source. A potential Mo-99 production pathway is by accelerator-initiated fissioning in a subcritical uranyl sulfate solution containing low enriched uranium (LEU). As part of the Argonne development effort, we are undertaking the AMORE (Argonne Molybdenum Research Experiment) project, which is essentially a pilot facility for all phases of Mo-99 production, recovery, and purification. Production of Mo-99 and other fission products in the subcritical target solution is initiated by putting an electron beam on a depleted uranium (DU) target; the fast neutrons produced in the DU target are thermalized and lead to fissioning of U-235. At the end of irradiation, Mo is recovered from the target solution and separated from uranium and most of the fission products by using a titania column. The Mo is stripped from the column with an alkaline solution. After acidification of the Mo product solution from the recovery column, the Mo is concentrated (and further purified) in a second titania column. The strip solution from the concentration column is then purified with the LEU Modified Cintichem process. A full description of the process can be found elsewhere [1–3]. The initial commissioning steps for the AMORE project include performing a Mo-99 spike test with pH 1 sulfuric acid in the target vessel without a beam on the target to demonstrate the initial Mo separation-and-recovery process, followed by the concentration column process. All glovebox operations were tested with cold solutions prior to performing the Mo-99 spike tests. Two Mo-99 spike tests with pH 1 sulfuric acid have been performed to date. Figure 1 shows the flow diagram for the remotely operated Mo-recovery system for the AMORE project

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

    Science.gov (United States)

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

    2013-01-01

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

  13. Calcium and Mitosis

    Science.gov (United States)

    Hepler, P.

    1983-01-01

    Although the mechanism of calcium regulation is not understood, there is evidence that calcium plays a role in mitosis. Experiments conducted show that: (1) the spindle apparatus contains a highly developed membrane system that has many characteristics of sarcoplasmic reticulum of muscle; (2) this membrane system contains calcium; and (3) there are ionic fluxes occurring during mitosis which can be seen by a variety of fluorescence probes. Whether the process of mitosis can be modulated by experimentally modulating calcium is discussed.

  14. Spike Pattern Structure Influences Synaptic Efficacy Variability under STDP and Synaptic Homeostasis. I: Spike Generating Models on Converging Motifs

    OpenAIRE

    Bi, Zedong; Zhou, Changsong

    2016-01-01

    In neural systems, synaptic plasticity is usually driven by spike trains. Due to the inherent noises of neurons and synapses as well as the randomness of connection details, spike trains typically exhibit variability such as spatial randomness and temporal stochasticity, resulting in variability of synaptic changes under plasticity, which we call efficacy variability. How the variability of spike trains influences the efficacy variability of synapses remains unclear. In this paper, we try to...

  15. The α2δ subunit and absence epilepsy: Beyond calcium channels?

    NARCIS (Netherlands)

    Celli, R.; Santolini, I.; Guiducci, M.; Luijtelaar, E.L.J.M. van; Parisi, P.; Striano, P.; Gradini, R.; Battaglia, G.; Ngomba, R.T.; Nicoletti, F.

    2017-01-01

    Spike-wave discharges, underlying absence seizures, are generated within a cortico-thalamo-cortical network that involves the somatosensory cortex, the reticular thalamic nucleus, and the ventrobasal thalamic nuclei. Activation of T-type voltage-sensitive calcium channels (VSCCs) contributes to the

  16. Calcium - Function and effects

    NARCIS (Netherlands)

    Liang, Jianfen; He, Yifan; Gao, Qian; Wang, Xuan; Nout, M.J.R.

    2016-01-01

    Rice is the primary food source for more than half of the world population. Levels of calcium contents and inhibitor - phytic acid are summarized in this chapter. Phytic acid has a very strong chelating ability and it is the main inhibit factor for calcium in rice products. Calcium contents in

  17. Calcium, An Overview-1989.

    Science.gov (United States)

    Wiercinski, Floyd J

    1989-06-01

    An overview of calcium is presented including introduction, pre-history, chronology of the research recorded in the literature, discussion, summary, recent references, literature cited, acknowledgments, and appendix. Elemental calcium began with the Earth's formation. Calcium was used for utilitarian purposes in B.C. times. In the 12th and 13th centuries A.D., calcium oxide was formed by roasting limestone to form calcium carbonate. A test for calcium was found in the 17th century, and "stones" were observed in humans (see appendix). In the 19th century, calcium was isolated and chemically identified by electrolysis, and later in that century calcium was found to be needed in a physiological solution similar to the ionic content of blood. In the 20th century it was found that, in the absence of calcium, living cells pulled away from one another. Anesthesia was produced by massive injection of magnesium salts into a mammal-conciousness could be restored by the addition of calcium, which neutralized the magnesium. Finally, calcium out of control in necrosis has an invasive action. Calcium antagonists and their mode of action were described in 1986.

  18. [Wide QRS tachycardia preceded by pacemaker spikes].

    Science.gov (United States)

    Romero, M; Aranda, A; Gómez, F J; Jurado, A

    2014-04-01

    The differential diagnosis and therapeutic management of wide QRS tachycardia preceded by pacemaker spike is presented. The pacemaker-mediated tachycardia, tachycardia fibrillo-flutter in patients with pacemakers, and runaway pacemakers, have a similar surface electrocardiogram, but respond to different therapeutic measures. The tachycardia response to the application of a magnet over the pacemaker could help in the differential diagnosis, and in some cases will be therapeutic, as in the case of a tachycardia-mediated pacemaker. Although these conditions are diagnosed and treated in hospitals with catheterization laboratories using the application programmer over the pacemaker, patients presenting in primary care clinic and emergency forced us to make a diagnosis and treat the haemodynamically unstable patient prior to referral. Copyright © 2012 Sociedad Española de Médicos de Atención Primaria (SEMERGEN). Publicado por Elsevier España. All rights reserved.

  19. Neuronal spike sorting based on radial basis function neural networks

    Directory of Open Access Journals (Sweden)

    Taghavi Kani M

    2011-02-01

    Full Text Available "nBackground: Studying the behavior of a society of neurons, extracting the communication mechanisms of brain with other tissues, finding treatment for some nervous system diseases and designing neuroprosthetic devices, require an algorithm to sort neuralspikes automatically. However, sorting neural spikes is a challenging task because of the low signal to noise ratio (SNR of the spikes. The main purpose of this study was to design an automatic algorithm for classifying neuronal spikes that are emitted from a specific region of the nervous system."n "nMethods: The spike sorting process usually consists of three stages: detection, feature extraction and sorting. We initially used signal statistics to detect neural spikes. Then, we chose a limited number of typical spikes as features and finally used them to train a radial basis function (RBF neural network to sort the spikes. In most spike sorting devices, these signals are not linearly discriminative. In order to solve this problem, the aforesaid RBF neural network was used."n "nResults: After the learning process, our proposed algorithm classified any arbitrary spike. The obtained results showed that even though the proposed Radial Basis Spike Sorter (RBSS reached to the same error as the previous methods, however, the computational costs were much lower compared to other algorithms. Moreover, the competitive points of the proposed algorithm were its good speed and low computational complexity."n "nConclusion: Regarding the results of this study, the proposed algorithm seems to serve the purpose of procedures that require real-time processing and spike sorting.

  20. A robust and biologically plausible spike pattern recognition network.

    Science.gov (United States)

    Larson, Eric; Perrone, Ben P; Sen, Kamal; Billimoria, Cyrus P

    2010-11-17

    The neural mechanisms that enable recognition of spiking patterns in the brain are currently unknown. This is especially relevant in sensory systems, in which the brain has to detect such patterns and recognize relevant stimuli by processing peripheral inputs; in particular, it is unclear how sensory systems can recognize time-varying stimuli by processing spiking activity. Because auditory stimuli are represented by time-varying fluctuations in frequency content, it is useful to consider how such stimuli can be recognized by neural processing. Previous models for sound recognition have used preprocessed or low-level auditory signals as input, but complex natural sounds such as speech are thought to be processed in auditory cortex, and brain regions involved in object recognition in general must deal with the natural variability present in spike trains. Thus, we used neural recordings to investigate how a spike pattern recognition system could deal with the intrinsic variability and diverse response properties of cortical spike trains. We propose a biologically plausible computational spike pattern recognition model that uses an excitatory chain of neurons to spatially preserve the temporal representation of the spike pattern. Using a single neural recording as input, the model can be trained using a spike-timing-dependent plasticity-based learning rule to recognize neural responses to 20 different bird songs with >98% accuracy and can be stimulated to evoke reverse spike pattern playback. Although we test spike train recognition performance in an auditory task, this model can be applied to recognize sufficiently reliable spike patterns from any neuronal system.

  1. Spike sorting for polytrodes: a divide and conquer approach

    Directory of Open Access Journals (Sweden)

    Nicholas V. Swindale

    2014-02-01

    Full Text Available In order to determine patterns of neural activity, spike signals recorded by extracellular electrodes have to be clustered (sorted with the aim of ensuring that each cluster represents all the spikes generated by an individual neuron. Many methods for spike sorting have been proposed but few are easily applicable to recordings from polytrodes which may have 16 or more recording sites. As with tetrodes, these are spaced sufficiently closely that signals from single neurons will usually be recorded on several adjacent sites. Although this offers a better chance of distinguishing neurons with similarly shaped spikes, sorting is difficult in such cases because of the high dimensionality of the space in which the signals must be classified. This report details a method for spike sorting based on a divide and conquer approach. Clusters are initially formed by assigning each event to the channel on which it is largest. Each channel-based cluster is then sub-divided into as many distinct clusters as possible. These are then recombined on the basis of pairwise tests into a final set of clusters. Pairwise tests are also performed to establish how distinct each cluster is from the others. A modified gradient ascent clustering (GAC algorithm is used to do the clustering. The method can sort spikes with minimal user input in times comparable to real time for recordings lasting up to 45 minutes. Our results illustrate some of the difficulties inherent in spike sorting, including changes in spike shape over time. We show that some physiologically distinct units may have very similar spike shapes. We show that RMS measures of spike shape similarity are not sensitive enough to discriminate clusters that can otherwise be separated by principal components analysis. Hence spike sorting based on least-squares matching to templates may be unreliable. Our methods should be applicable to tetrodes and scaleable to larger multi-electrode arrays (MEAs.

  2. Spike sorting for polytrodes: a divide and conquer approach.

    Science.gov (United States)

    Swindale, Nicholas V; Spacek, Martin A

    2014-01-01

    In order to determine patterns of neural activity, spike signals recorded by extracellular electrodes have to be clustered (sorted) with the aim of ensuring that each cluster represents all the spikes generated by an individual neuron. Many methods for spike sorting have been proposed but few are easily applicable to recordings from polytrodes which may have 16 or more recording sites. As with tetrodes, these are spaced sufficiently closely that signals from single neurons will usually be recorded on several adjacent sites. Although this offers a better chance of distinguishing neurons with similarly shaped spikes, sorting is difficult in such cases because of the high dimensionality of the space in which the signals must be classified. This report details a method for spike sorting based on a divide and conquer approach. Clusters are initially formed by assigning each event to the channel on which it is largest. Each channel-based cluster is then sub-divided into as many distinct clusters as possible. These are then recombined on the basis of pairwise tests into a final set of clusters. Pairwise tests are also performed to establish how distinct each cluster is from the others. A modified gradient ascent clustering (GAC) algorithm is used to do the clustering. The method can sort spikes with minimal user input in times comparable to real time for recordings lasting up to 45 min. Our results illustrate some of the difficulties inherent in spike sorting, including changes in spike shape over time. We show that some physiologically distinct units may have very similar spike shapes. We show that RMS measures of spike shape similarity are not sensitive enough to discriminate clusters that can otherwise be separated by principal components analysis (PCA). Hence spike sorting based on least-squares matching to templates may be unreliable. Our methods should be applicable to tetrodes and scalable to larger multi-electrode arrays (MEAs).

  3. Clustering predicts memory performance in networks of spiking and non-spiking neurons

    Directory of Open Access Journals (Sweden)

    Weiliang eChen

    2011-03-01

    Full Text Available The problem we address in this paper is that of finding effective and parsimonious patterns of connectivity in sparse associative memories. This problem must be addressed in real neuronal systems, so that results in artificial systems could throw light on real systems. We show that there are efficient patterns of connectivity and that these patterns are effective in models with either spiking or non-spiking neurons. This suggests that there may be some underlying general principles governing good connectivity in such networks. We also show that the clustering of the network, measured by Clustering Coefficient, has a strong linear correlation to the performance of associative memory. This result is important since a purely static measure of network connectivity appears to determine an important dynamic property of the network.

  4. Cell-cycle calcium transients driven by cyclic changes in inositol trisphosphate levels.

    Science.gov (United States)

    Ciapa, B; Pesando, D; Wilding, M; Whitaker, M

    1994-04-28

    Transient changes in intracellular calcium ([Ca2+]i) have been shown to punctuate the cell cycle in various types of cells in culture and in early embryos. The [Ca2+]i transients are correlated with cell-cycle events: pronuclear migration, nuclear envelope breakdown, the metaphase-anaphase transition of mitosis, and cytokinesis. Mitotic events can be induced by injecting calcium and prevented by injecting calcium chelators into the sea urchin embryo. Cell-cycle calcium transients differ from the transients linked to membrane signal transduction pathways: they are generated by an endogenous mechanism, not by plasma membrane receptor complexes, and their trigger is unknown. We report here that the phosphoinositide messenger system oscillates during the early embryonic cell cycle in the sea urchin, leading to cyclic increases in inositol trisphosphate that trigger cell-cycle [Ca2+]i transients and mitosis by calcium release from intracellular stores.

  5. Layer Specific Development of Neocortical Pyramidal to Fast Spiking Cells Synapses.

    Directory of Open Access Journals (Sweden)

    Olga eVoinova

    2016-01-01

    Full Text Available All cortical neurons are engaged in inhibitory feedback loops which ensure excitation-inhibition balance and are key elements for the development of coherent network activity. The resulting network patterns are strongly dependent on the strength and dynamic properties of these excitatory-inhibitory loops which show pronounced regional and developmental diversity. We therefore compared the properties and postnatal maturation of two different synapses between rat neocortical pyramidal cells (layer 2/3 and layer 5, respectively and fast spiking (FS interneurons in the corresponding layer. At P14, both synapses showed synaptic depression upon repetitive activation. Synaptic release properties between layer 2/3 pyramidal cells and FS cells were stable from P14 to P28. In contrast, layer 5 pyramidal to FS cell connections showed a significant increase in paired pulse ratio by P28. Presynaptic calcium dynamics did also change at these synapses, including the sensitivity to exogenously loaded calcium buffers and expression of presynaptic calcium channels subtypes. These results underline the large variety of properties at different, yet similar, synapses in the neocortex. They also suggest that postnatal maturation of the brain goes along with increasing differences between synaptically driven network activity in layer 5 and layer 2/3.

  6. Calcium regulation of EGF-induced ERK5 activation: role of Lad1-MEKK2 interaction.

    Directory of Open Access Journals (Sweden)

    Zhong Yao

    Full Text Available The ERK5 cascade is a MAPK pathway that transmits both mitogenic and stress signals, yet its mechanism of activation is not fully understood. Using intracellular calcium modifiers, we found that ERK5 activation by EGF is inhibited both by the depletion and elevation of intracellular calcium levels. This calcium effect was found to occur upstream of MEKK2, which is the MAP3K of the ERK5 cascade. Co-immunoprecipitation revealed that EGF increases MEKK2 binding to the adaptor protein Lad1, and this interaction was reduced by the intracellular calcium modifiers, indicating that a proper calcium concentration is required for the interactions and transmission of EGF signals to ERK5. In vitro binding assays revealed that the proper calcium concentration is required for a direct binding of MEKK2 to Lad1. The binding of these proteins is not affected by c-Src-mediated phosphorylation on Lad1, but slightly affects the Tyr phosphorylation of MEKK2, suggesting that the interaction with Lad1 is necessary for full Tyr phosphorylation of MEKK2. In addition, we found that changes in calcium levels affect the EGF-induced nuclear translocation of MEKK2 and thereby its effect on the nuclear ERK5 activity. Taken together, these findings suggest that calcium is required for EGF-induced ERK5 activation, and this effect is probably mediated by securing proper interaction of MEKK2 with the upstream adaptor protein Lad1.

  7. Simultaneous imaging and functional studies reveal a tight correlation between calcium and actin networks.

    Science.gov (United States)

    Bascom, Carlisle S; Winship, Lawrence J; Bezanilla, Magdalena

    2018-03-20

    Tip-growing cells elongate in a highly polarized manner via focused secretion of flexible cell-wall material. Calcium has been implicated as a vital factor in regulating the deposition of cell-wall material. However, deciphering the molecular and mechanistic calcium targets in vivo has remained challenging. Here, we investigated intracellular calcium dynamics in the moss Physcomitrella patens , which provides a system with an abundant source of genetically identical tip-growing cells, excellent cytology, and a large molecular genetic tool kit. To visualize calcium we used a genetically encoded cytosolic FRET probe, revealing a fluctuating tipward gradient with a complex oscillatory profile. Wavelet analysis coupled with a signal-sifting algorithm enabled the quantitative comparison of the calcium behavior in cells where growth was inhibited mechanically, pharmacologically, or genetically. We found that cells with suppressed growth have calcium oscillatory profiles with longer frequencies, suggesting that there is a feedback between the calcium gradient and growth. To investigate the mechanistic basis for this feedback we simultaneously imaged cytosolic calcium and actin, which has been shown to be essential for tip growth. We found that high cytosolic calcium promotes disassembly of a tip-focused actin spot, while low calcium promotes assembly. In support of this, abolishing the calcium gradient resulted in dramatic actin accumulation at the tip. Together these data demonstrate that tipward calcium is quantitatively linked to actin accumulation in vivo and that the moss P. patens provides a powerful system to uncover mechanistic links between calcium, actin, and growth.

  8. No WIMP mini-spikes in dwarf spheroidal galaxies

    NARCIS (Netherlands)

    Wanders, M.; Bertone, G.; Volonteri, M.; Weniger, C.

    2015-01-01

    The formation of black holes inevitably affects the distribution of dark and baryonic matter in their vicinity, leading to an enhancement of the dark matter density, called spike, and if dark matter is made of WIMPs, to a strong enhancement of the dark matter annihilation rate. Spikes at the center

  9. Grain price spikes and beggar-thy-neighbor policy responses

    DEFF Research Database (Denmark)

    Boysen, Ole; Jensen, Hans Grinsted

    Upward spikes in the international price of food in recent years led some countries to raise export barriers, thereby exacerbating both the price spike and reducing the terms of trade for food-importing countries (beggaring their neighbors). At the same time, and for similar political...

  10. Interictal spike EEG source analysis in hypothalamic hamartoma epilepsy.

    Science.gov (United States)

    Leal, Alberto J R; Passão, Vitorina; Calado, Eulália; Vieira, José P; Silva Cunha, João P

    2002-12-01

    The epilepsy associated with the hypothalamic hamartomas constitutes a syndrome with peculiar seizures, usually refractory to medical therapy, mild cognitive delay, behavioural problems and multifocal spike activity in the scalp electroencephalogram (EEG). The cortical origin of spikes has been widely assumed but not specifically demonstrated. We present results of a source analysis of interictal spikes from 4 patients (age 2-25 years) with epilepsy and hypothalamic hamartoma, using EEG scalp recordings (32 electrodes) and realistic boundary element models constructed from volumetric magnetic resonance imaging (MRIs). Multifocal spike activity was the most common finding, distributed mainly over the frontal and temporal lobes. A spike classification based on scalp topography was done and averaging within each class performed to improve the signal to noise ratio. Single moving dipole models were used, as well as the Rap-MUSIC algorithm. All spikes with good signal to noise ratio were best explained by initial deep sources in the neighbourhood of the hamartoma, with late sources located in the cortex. Not a single patient could have his spike activity explained by a combination of cortical sources. Overall, the results demonstrate a consistent origin of spike activity in the subcortical region in the neighbourhood of the hamartoma, with late spread to cortical areas.

  11. Spike protection device for electronics and communication appliances

    African Journals Online (AJOL)

    Experience shows that most failures of electronic and communication equipment result from damage caused by external electrical disturbances in the form of overvoltage, undervoltage, surge, sag, spike, or voltage dropout (blackout), the status of which is determined by the amplitude and duration of the disturbance. Spikes ...

  12. Diagrammatic scale for the assessment of blast on wheat spikes

    Directory of Open Access Journals (Sweden)

    João Leodato Nunes Maciel

    2013-09-01

    Full Text Available The correct quantification of blast caused by the fungus Magnaporthe oryzae on wheat (Triticum aestivum spikes is an important component to understand the development of this disease aimed at its control. Visual quantification based on a diagrammatic scale can be a practical and efficient strategy that has already proven to be useful against several plant pathosystems, including diseases affecting wheat spikes like glume blotch and fusarium head blight. Spikes showing different disease severity values were collected from a wheat field with the aim of elaborating a diagrammatic scale to quantify blast severity on wheat spikes. The spikes were photographed and blast severity was determined by using resources of the software ImageJ. A diagrammatic scale was developed with the following disease severity values: 3.7, 7.5, 21.4, 30.5, 43.8, 57.3, 68.1, 86.0, and 100.0%. An asymptomatic spike was added to the scale. Scale validation was performed by eight people who estimated blast severity by using digitalized images of 40 wheat spikes. The precision and the accuracy of the evaluations varied according to the rater (0.82spikes.

  13. SPIKY: a graphical user interface for monitoring spike train synchrony

    Science.gov (United States)

    Mulansky, Mario; Bozanic, Nebojsa

    2015-01-01

    Techniques for recording large-scale neuronal spiking activity are developing very fast. This leads to an increasing demand for algorithms capable of analyzing large amounts of experimental spike train data. One of the most crucial and demanding tasks is the identification of similarity patterns with a very high temporal resolution and across different spatial scales. To address this task, in recent years three time-resolved measures of spike train synchrony have been proposed, the ISI-distance, the SPIKE-distance, and event synchronization. The Matlab source codes for calculating and visualizing these measures have been made publicly available. However, due to the many different possible representations of the results the use of these codes is rather complicated and their application requires some basic knowledge of Matlab. Thus it became desirable to provide a more user-friendly and interactive interface. Here we address this need and present SPIKY, a graphical user interface that facilitates the application of time-resolved measures of spike train synchrony to both simulated and real data. SPIKY includes implementations of the ISI-distance, the SPIKE-distance, and the SPIKE-synchronization (an improved and simplified extension of event synchronization) that have been optimized with respect to computation speed and memory demand. It also comprises a spike train generator and an event detector that makes it capable of analyzing continuous data. Finally, the SPIKY package includes additional complementary programs aimed at the analysis of large numbers of datasets and the estimation of significance levels. PMID:25744888

  14. Calcium wave propagation in networks of endothelial cells: model-based theoretical and experimental study.

    Directory of Open Access Journals (Sweden)

    Juexuan Long

    Full Text Available In this paper, we present a combined theoretical and experimental study of the propagation of calcium signals in multicellular structures composed of human endothelial cells. We consider multicellular structures composed of a single chain of cells as well as a chain of cells with a side branch, namely a "T" structure. In the experiments, we investigate the result of applying mechano-stimulation to induce signaling in the form of calcium waves along the chain and the effect of single and dual stimulation of the multicellular structure. The experimental results provide evidence of an effect of architecture on the propagation of calcium waves. Simulations based on a model of calcium-induced calcium release and cell-to-cell diffusion through gap junctions shows that the propagation of calcium waves is dependent upon the competition between intracellular calcium regulation and architecture-dependent intercellular diffusion.

  15. Targeting calcium signaling in cancer therapy

    Directory of Open Access Journals (Sweden)

    Chaochu Cui

    2017-01-01

    Full Text Available The intracellular calcium ions (Ca2+ act as second messenger to regulate gene transcription, cell proliferation, migration and death. Accumulating evidences have demonstrated that intracellular Ca2+ homeostasis is altered in cancer cells and the alteration is involved in tumor initiation, angiogenesis, progression and metastasis. Targeting derailed Ca2+ signaling for cancer therapy has become an emerging research area. This review summarizes some important Ca2+ channels, transporters and Ca2+-ATPases, which have been reported to be altered in human cancer patients. It discusses the current research effort toward evaluation of the blockers, inhibitors or regulators for Ca2+ channels/transporters or Ca2+-ATPase pumps as anti-cancer drugs. This review is also aimed to stimulate interest in, and support for research into the understanding of cellular mechanisms underlying the regulation of Ca2+ signaling in different cancer cells, and to search for novel therapies to cure these malignancies by targeting Ca2+ channels or transporters.

  16. Spectral components of cytosolic [Ca2+] spiking in neurons

    DEFF Research Database (Denmark)

    Kardos, J; Szilágyi, N; Juhász, G

    1998-01-01

    We show here, by means of evolutionary spectral analysis and synthesis of cytosolic Ca2+ ([Ca2+]c) spiking observed at the single cell level using digital imaging fluorescence microscopy of fura-2-loaded mouse cerebellar granule cells in culture, that [Ca2+]c spiking can be resolved into evolutio......We show here, by means of evolutionary spectral analysis and synthesis of cytosolic Ca2+ ([Ca2+]c) spiking observed at the single cell level using digital imaging fluorescence microscopy of fura-2-loaded mouse cerebellar granule cells in culture, that [Ca2+]c spiking can be resolved...... into evolutionary spectra of a characteristic set of frequencies. Non-delayed small spikes on top of sustained [Ca2+]c were synthesized by a main component frequency, 0.132+/-0.012 Hz, showing its maximal amplitude in phase with the start of depolarization (25 mM KCI) combined with caffeine (10 mM) application...

  17. Spike detection II: automatic, perception-based detection and clustering.

    Science.gov (United States)

    Wilson, S B; Turner, C A; Emerson, R G; Scheuer, M L

    1999-03-01

    We developed perception-based spike detection and clustering algorithms. The detection algorithm employs a novel, multiple monotonic neural network (MMNN). It is tested on two short-duration EEG databases containing 2400 spikes from 50 epilepsy patients and 10 control subjects. Previous studies are compared for database difficulty and reliability and algorithm accuracy. Automatic grouping of spikes via hierarchical clustering (using topology and morphology) is visually compared with hand marked grouping on a single record. The MMNN algorithm is found to operate close to the ability of a human expert while alleviating problems related to overtraining. The hierarchical and hand marked spike groupings are found to be strikingly similar. An automatic detection algorithm need not be as accurate as a human expert to be clinically useful. A user interface that allows the neurologist to quickly delete artifacts and determine whether there are multiple spike generators is sufficient.

  18. A supervised learning rule for classification of spatiotemporal spike patterns.

    Science.gov (United States)

    Lilin Guo; Zhenzhong Wang; Adjouadi, Malek

    2016-08-01

    This study introduces a novel supervised algorithm for spiking neurons that take into consideration synapse delays and axonal delays associated with weights. It can be utilized for both classification and association and uses several biologically influenced properties, such as axonal and synaptic delays. This algorithm also takes into consideration spike-timing-dependent plasticity as in Remote Supervised Method (ReSuMe). This paper focuses on the classification aspect alone. Spiked neurons trained according to this proposed learning rule are capable of classifying different categories by the associated sequences of precisely timed spikes. Simulation results have shown that the proposed learning method greatly improves classification accuracy when compared to the Spike Pattern Association Neuron (SPAN) and the Tempotron learning rule.

  19. Local calcium elevation and cell elongation initiate guided motility in electrically stimulated osteoblast-like cells.

    Directory of Open Access Journals (Sweden)

    Nurdan Ozkucur

    Full Text Available BACKGROUND: Investigation of the mechanisms of guided cell migration can contribute to our understanding of many crucial biological processes, such as development and regeneration. Endogenous and exogenous direct current electric fields (dcEF are known to induce directional cell migration, however the initial cellular responses to electrical stimulation are poorly understood. Ion fluxes, besides regulating intracellular homeostasis, have been implicated in many biological events, including regeneration. Therefore understanding intracellular ion kinetics during EF-directed cell migration can provide useful information for development and regeneration. METHODOLOGY/PRINCIPAL FINDINGS: We analyzed the initial events during migration of two osteogenic cell types, rat calvarial and human SaOS-2 cells, exposed to strong (10-15 V/cm and weak (< or = 5 V/cm dcEFs. Cell elongation and perpendicular orientation to the EF vector occurred in a time- and voltage-dependent manner. Calvarial osteoblasts migrated to the cathode as they formed new filopodia or lamellipodia and reorganized their cytoskeleton on the cathodal side. SaOS-2 cells showed similar responses except towards the anode. Strong dcEFs triggered a rapid increase in intracellular calcium levels, whereas a steady state level of intracellular calcium was observed in weaker fields. Interestingly, we found that dcEF-induced intracellular calcium elevation was initiated with a local rise on opposite sides in calvarial and SaOS-2 cells, which may explain their preferred directionality. In calcium-free conditions, dcEFs induced neither intracellular calcium elevation nor directed migration, indicating an important role for calcium ions. Blocking studies using cadmium chloride revealed that voltage-gated calcium channels (VGCCs are involved in dcEF-induced intracellular calcium elevation. CONCLUSION/SIGNIFICANCE: Taken together, these data form a time scale of the morphological and physiological

  20. Structural dynamics of the cell nucleus: basis for morphology modulation of nuclear calcium signaling and gene transcription.

    Science.gov (United States)

    Queisser, Gillian; Wiegert, Simon; Bading, Hilmar

    2011-01-01

    Neuronal morphology plays an essential role in signal processing in the brain. Individual neurons can undergo use-dependent changes in their shape and connectivity, which affects how intracellular processes are regulated and how signals are transferred from one cell to another in a neuronal network. Calcium is one of the most important intracellular second messengers regulating cellular morphologies and functions. In neurons, intracellular calcium levels are controlled by ion channels in the plasma membrane such as NMDA receptors (NMDARs), voltage-gated calcium channels (VGCCs) and certain α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) as well as by calcium exchange pathways between the cytosol and internal calcium stores including the endoplasmic reticulum and mitochondria. Synaptic activity and the subsequent opening of ligand and/or voltage-gated calcium channels can initiate cytosolic calcium transients which propagate towards the cell soma and enter the nucleus via its nuclear pore complexes (NPCs) embedded in the nuclear envelope. We recently described the discovery that in hippocampal neurons the morphology of the nucleus affects the calcium dynamics within the nucleus. Here we propose that nuclear infoldings determine whether a nucleus functions as an integrator or detector of oscillating calcium signals. We outline possible ties between nuclear mophology and transcriptional activity and discuss the importance of extending the approach to whole cell calcium signal modeling in order to understand synapse-to-nucleus communication in healthy and dysfunctional neurons.

  1. Structure-activity relationship study and discovery of indazole 3-carboxamides as calcium-release activated calcium channel blockers.

    Science.gov (United States)

    Bai, Sha; Nagai, Masazumi; Koerner, Steffi K; Veves, Aristidis; Sun, Lijun

    2017-02-01

    Aberrant activation of mast cells contributes to the development of numerous diseases including cancer, autoimmune disorders, as well as diabetes and its complications. The influx of extracellular calcium via the highly calcium selective calcium-release activated calcium (CRAC) channel controls mast cell functions. Intracellular calcium homeostasis in mast cells can be maintained via the modulation of the CRAC channel, representing a critical point for therapeutic interventions. We describe the structure-activity relationship study (SAR) of indazole-3-carboxamides as potent CRAC channel blockers and their ability to stabilize mast cells. Our SAR results show that the unique regiochemistry of the amide linker is critical for the inhibition of calcium influx, the release of the pro-inflammatory mediators β-hexosaminidase and tumor necrosis factor α by activated mast cells. Thus, the indazole-3-carboxamide 12d actively inhibits calcium influx and stabilizes mast cells with sub-μM IC 50 . In contrast, its reverse amide isomer 9c is inactive in the calcium influx assay even at 100μM concentration. This requirement of the specific 3-carboxamide regiochemistry in indazoles is unprecedented in known CRAC channel blockers. The new structural scaffolds described in this report expand the structural diversity of the CRAC channel blockers and may lead to the discovery of novel immune modulators for the treatment of human diseases. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. Calcium signalling during zebrafish embryonic development.

    Science.gov (United States)

    Webb, S E; Miller, A L

    2000-02-01

    Calcium signals appear throughout the first 24 hours of zebrafish development. These begin at egg activation, then continue to be generated throughout the subsequent zygote, cleavage, blastula, gastrula, and segmentation periods. They are thus associated with the major phases of pattern formation: cell proliferation, cell differentiation, axis determination, the generation of primary germ layers, the emergence of rudimentary organ systems, and therefore the establishment of the basic vertebrate body plan. When signals need to be transmitted across significant distances they take the form of waves, either intracellular waves when the cell size is large, or later in development when the cell size is reduced, intercellular waves. We will consider both types of calcium signals and their integration into signalling networks, and discuss their possible functions and developmental significance with regard to pattern formation. BioEssays 22:113-123, 2000. Copyright 2000 John Wiley & Sons, Inc.

  3. Collective Calcium Signaling of Defective Multicellular Networks

    Science.gov (United States)

    Potter, Garrett; Sun, Bo

    2015-03-01

    A communicating multicellular network processes environmental cues into collective cellular dynamics. We have previously demonstrated that, when excited by extracellular ATP, fibroblast monolayers generate correlated calcium dynamics modulated by both the stimuli and gap junction communication between the cells. However, just as a well-connected neural network may be compromised by abnormal neurons, a tissue monolayer can also be defective with cancer cells, which typically have down regulated gap junctions. To understand the collective cellular dynamics in a defective multicellular network we have studied the calcium signaling of co-cultured breast cancer cells and fibroblast cells in various concentrations of ATP delivered through microfluidic devices. Our results demonstrate that cancer cells respond faster, generate singular spikes, and are more synchronous across all stimuli concentrations. Additionally, fibroblast cells exhibit persistent calcium oscillations that increase in regularity with greater stimuli. To interpret these results we quantitatively analyzed the immunostaining of purigenic receptors and gap junction channels. The results confirm our hypothesis that collective dynamics are mainly determined by the availability of gap junction communications.

  4. Stress enhanced calcium kinetics in a neuron.

    Science.gov (United States)

    Kant, Aayush; Bhandakkar, Tanmay K; Medhekar, Nikhil V

    2018-02-01

    Accurate modeling of the mechanobiological response of a Traumatic Brain Injury is beneficial toward its effective clinical examination, treatment and prevention. Here, we present a stress history-dependent non-spatial kinetic model to predict the microscale phenomena of secondary insults due to accumulation of excess calcium ions (Ca[Formula: see text]) induced by the macroscale primary injuries. The model is able to capture the experimentally observed increase and subsequent partial recovery of intracellular Ca[Formula: see text] concentration in response to various types of mechanical impulses. We further establish the accuracy of the model by comparing our predictions with key experimental observations.

  5. Effect of calcium on cell-wall degrading enzymes of Botrytis cinerea.

    Science.gov (United States)

    Sasanuma, Izumi; Suzuki, Takuya

    2016-09-01

    Effective anti-Botrytis strategies leading to reduce pesticides on strawberries are examined to provide the protection that is harmless to humans, higher animals and plants. Calcium treatments significantly inhibited the spore germination and mycelial growth of B. cinerea. The intracellular polygalacturonase and CMCase showed low activities in B. cinerea cultivated by medium containing calcium. On the other hand, calcium-stimulated β-glucosidases production occurred. Our findings suggest that the calcium treatments keep CMCase activity low and cause low activities of cell-wall degrading enzymes of B. cinerea in the late stage of growth.

  6. Caffeine-Induced Suppression of GABAergic Inhibition and Calcium-Independent Metaplasticity

    Directory of Open Access Journals (Sweden)

    Masako Isokawa

    2016-01-01

    Full Text Available GABAergic inhibition plays a critical role in the regulation of neuron excitability; thus, it is subject to modulations by many factors. Recent evidence suggests the elevation of intracellular calcium ([Ca2+]i and calcium-dependent signaling molecules underlie the modulations. Caffeine induces a release of calcium from intracellular stores. We tested whether caffeine modulated GABAergic transmission by increasing [Ca2+]i. A brief local puff-application of caffeine to hippocampal CA1 pyramidal cells transiently suppressed GABAergic inhibitory postsynaptic currents (IPSCs by 73.2 ± 6.98%. Time course of suppression and the subsequent recovery of IPSCs resembled DSI (depolarization-induced suppression of inhibition, mediated by endogenous cannabinoids that require a [Ca2+]i rise. However, unlike DSI, caffeine-induced suppression of IPSCs (CSI persisted in the absence of a [Ca2+]i rise. Intracellular applications of BAPTA and ryanodine (which blocks caffeine-induced calcium release from intracellular stores failed to prevent the generation of CSI. Surprisingly, ruthenium red, an inhibitor of multiple calcium permeable/release channels including those of stores, induced metaplasticity by amplifying the magnitude of CSI independently of calcium. This metaplasticity was accompanied with the generation of a large inward current. Although ionic basis of this inward current is undetermined, the present result demonstrates that caffeine has a robust Ca2+-independent inhibitory action on GABAergic inhibition and causes metaplasticity by opening plasma membrane channels.

  7. Calcium electrotransfer for termination of transgene expression in muscle

    DEFF Research Database (Denmark)

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

    2011-01-01

    Gene electrotransfer is expanding in clinical use, thus we have searched for an emergency procedure to stop transgene expression in case of serious adverse events. Calcium is cytotoxic at high intracellular levels, so we tested effects of calcium electrotransfer on transgene expression in muscle....... A clinical grade calcium solution (20 µl, 168 mM) was injected into transfected mouse or rat tibialis cranialis muscle. Ca(2+) uptake was quantified using calcium 45 ((45)Ca), and voltage and time between injection and pulsation were varied. Extinction of transgene expression was investigated by using both...... voltage pulses of 1000 V/cm. Using these parameters, in vivo imaging showed that transgene expression significantly decreased 4 hr after Ca(2+) electrotransfer and was eliminated within 24 hr. Similarly, serum erythropoietin was reduced by 46% at 4 hr and to control levels at 2 days. Histological analyses...

  8. Short-range intercellular calcium signaling in bone

    DEFF Research Database (Denmark)

    Jørgensen, Niklas Rye

    2005-01-01

    The regulation of bone turnover is a complex and finely tuned process. Many factors regulate bone remodeling, including hormones, growth factors, cytokines etc. However, little is known about the signals coupling bone formation to bone resorption, and how mechanical forces are translated...... into biological effects in bone. Intercellular calcium waves are increases in intracellular calcium concentration in single cells, subsequently propagating to adjacent cells, and can be a possible mechanism for the coupling of bone formation to bone resorption. The aim of the present studies was to investigate...... whether bone cells are capable of communicating via intercellular calcium signals, and determine by which mechanisms the cells propagate the signals. First, we found that osteoblastic cells can propagate intercellular calcium transients upon mechanical stimulation, and that there are two principally...

  9. Calcium absorption and achlorhydria

    International Nuclear Information System (INIS)

    Recker, R.R.

    1985-01-01

    Defective absorption of calcium has been thought to exist in patients with achlorhydria. The author compared absorption of calcium in its carbonate form with that in a pH-adjusted citrate form in a group of 11 fasting patients with achlorhydria and in 9 fasting normal subjects. Fractional calcium absorption was measured by a modified double-isotope procedure with 0.25 g of calcium used as the carrier. Mean calcium absorption (+/- S.D.) in the patients with achlorhydria was 0.452 +/- 0.125 for citrate and 0.042 +/- 0.021 for carbonate (P less than 0.0001). Fractional calcium absorption in the normal subjects was 0.243 +/- 0.049 for citrate and 0.225 +/- 0.108 for carbonate (not significant). Absorption of calcium from carbonate in patients with achlorhydria was significantly lower than in the normal subjects and was lower than absorption from citrate in either group; absorption from citrate in those with achlorhydria was significantly higher than in the normal subjects, as well as higher than absorption from carbonate in either group. Administration of calcium carbonate as part of a normal breakfast resulted in completely normal absorption in the achlorhydric subjects. These results indicate that calcium absorption from carbonate is impaired in achlorhydria under fasting conditions. Since achlorhydria is common in older persons, calcium carbonate may not be the ideal dietary supplement

  10. Transmitter modulation of spike-evoked calcium transients in arousal related neurons

    DEFF Research Database (Denmark)

    Kohlmeier, Kristi Anne; Leonard, Christopher S

    2006-01-01

    Nitric oxide synthase (NOS)-containing cholinergic neurons in the laterodorsal tegmentum (LDT) influence behavioral and motivational states through their projections to the thalamus, ventral tegmental area and a brainstem 'rapid eye movement (REM)-induction' site. Action potential-evoked intracel...

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

    DEFF Research Database (Denmark)

    Rossol, Manuela; Pierer, Matthias; Raulien, Nora

    2012-01-01

    calcium activates the NLRP3 inflammasome via stimulation of G protein-coupled calcium sensing receptors. Activation is mediated by signalling through the calcium-sensing receptor and GPRC6A via the phosphatidyl inositol/Ca(2+) pathway. The resulting increase in the intracellular calcium concentration......, and this effect was inhibited in GPRC6A(-/-) mice. Our results demonstrate that G-protein-coupled receptors can activate the inflammasome, and indicate that increased extracellular calcium has a role as a danger signal and amplifier of inflammation....

  12. Evaluation of cellular influences caused by calcium carbonate nanoparticles.

    Science.gov (United States)

    Horie, Masanori; Nishio, Keiko; Kato, Haruhisa; Endoh, Shigehisa; Fujita, Katsuhide; Nakamura, Ayako; Kinugasa, Shinichi; Hagihara, Yoshihisa; Yoshida, Yasukazu; Iwahashi, Hitoshi

    2014-03-05

    The cellular effects of calcium carbonate (CaCO₃) nanoparticles were evaluated. Three kinds of CaCO₃ nanoparticles were employed in our examinations. One of the types of CaCO₃ nanoparticles was highly soluble. And solubility of another type of CaCO₃ nanoparticle was lower. A stable CaCO₃ nanoparticle medium dispersion was prepared and applied to human lung carcinoma A549 cells and human keratinocyte HaCaT cells. Then, mitochondrial activity, cell membrane damage, colony formation ability, DNA injury, induction of oxidative stress, and apoptosis were evaluated. Although the influences of CaCO₃ nanoparticles on mitochondrial activity and cell membrane damage were small, "soluble" CaCO₃ nanoparticles exerted some cellular influences. Soluble CaCO₃ nanoparticles also induced a cell morphological change. Colony formation was inhibited by CaCO₃ nanoparticle exposure. In particular, soluble CaCO₃ nanoparticles completely inhibited colony formation. The influence on intracellular the reactive oxygen species (ROS) level was small. Soluble CaCO₃ nanoparticles caused an increase in C/EBP-homologous protein (CHOP) expression and the activation of caspase-3. Moreover, CaCO₃ exposure increased intracellular the Ca²⁺ level and activated calpain. These results suggest that cellular the influences of CaCO₃ nanoparticles are mainly caused by intracellular calcium release and subsequently disrupt the effect of calcium signaling. In conclusion, there is possibility that soluble CaCO₃ nanoparticles induce cellular influences such as a cell morphological change. Cellular influence of CaCO₃ nanoparticles is caused by intracellular calcium release. If inhaled CaCO₃ nanoparticles have the potential to influence cellular events. However, the effect might be not severe because calcium is omnipresent element in cell. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  13. Dose-dependent ATP depletion and cancer cell death following calcium electroporation, relative effect of calcium concentration and electric field strength

    DEFF Research Database (Denmark)

    Hansen, Emilie Louise; Sozer, Esin Bengisu; Romeo, Stefania

    2015-01-01

    death and could be a novel cancer treatment. This study aims at understanding the relationship between applied electric field, calcium concentration, ATP depletion and efficacy. METHODS: In three human cell lines--H69 (small-cell lung cancer), SW780 (bladder cancer), and U937 (leukaemia), viability...... was observed with fluorescence confocal microscopy of quinacrine-labelled U937 cells. RESULTS: Both H69 and SW780 cells showed dose-dependent (calcium concentration and electric field) decrease in intracellular ATP (p...-dependently reduced cell survival and intracellular ATP. Increasing extracellular calcium allows the use of a lower electric field. GENERAL SIGNIFICANCE: This study supports the use of calcium electroporation for treatment of cancer and possibly lowering the applied electric field in future trials....

  14. Phosphorylation of erythrocyte membrane liberates calcium

    International Nuclear Information System (INIS)

    Chauhan, V.P.S.; Brockerhoff, H.

    1986-01-01

    Phosphorylation of permeabilized erythrocyte ghost membranes with ATP results in an increase free calcium level as measured with the help of Ca 2+ electrode and 45 Ca. This effect could not be observed in the presence of p - chloromercuric benzoate, an inhibitor of kinases. The rise in the free calcium due to phosphorylation of the membrane was accompanied by a decrease in the level of phosphatidylinositol (PI) and an increase in phosphatidylinositolmonophosphate (PIP) and phosphatidylinositolbisphosphate (PIP 2 ). These results support the proposal that an inositol shuttle, PI ↔ PIP ↔ PIP 2 , operates to maintain the intracellular calcium concentration. The cation is believed to be sequestered in a cage formed by the head groups of two acidic phospholipid molecules, e.g., phosphatidylserine and phosphatidylinositol, with the participation of both PO and fatty acid ester CO groups. When the inositol group of such a cage is phosphorylated, inter-headgroup hydrogen bonding between the lipids is broken. As a result the cage opens and calcium is released

  15. Uroguanylin induces electroencephalographic spikes in rats

    Directory of Open Access Journals (Sweden)

    MDA. Teixeira

    Full Text Available Uroguanylin (UGN is an endogenous peptide that acts on membrane-bound guanylate cyclase receptors of intestinal and renal cells increasing cGMP production and regulating electrolyte and water epithelial transport. Recent research works demonstrate the expression of this peptide and its receptor in the central nervous system. The current work was undertaken in order to evaluate modifications of electroencephalographic spectra (EEG in anesthetized Wistar rats, submitted to intracisternal infusion of uroguanylin (0.0125 nmoles/min or 0.04 nmoles/min. The current observations demonstrate that 0.0125 nmoles/min and 0.04 nmoles/min intracisternal infusion of UGN significantly enhances amplitude and frequency of sharp waves and evoked spikes (p = 0.03. No statistical significance was observed on absolute alpha and theta spectra amplitude. The present data suggest that UGN acts on bioelectrogenesis of cortical cells by inducing hypersynchronic firing of neurons. This effect is blocked by nedocromil, suggesting that UGN acts by increasing the activity of chloride channels.

  16. Spiking irregularity and frequency modulate the behavioral report of single-neuron stimulation.

    Science.gov (United States)

    Doron, Guy; von Heimendahl, Moritz; Schlattmann, Peter; Houweling, Arthur R; Brecht, Michael

    2014-02-05

    The action potential activity of single cortical neurons can evoke measurable sensory effects, but it is not known how spiking parameters and neuronal subtypes affect the evoked sensations. Here, we examined the effects of spike train irregularity, spike frequency, and spike number on the detectability of single-neuron stimulation in rat somatosensory cortex. For regular-spiking, putative excitatory neurons, detectability increased with spike train irregularity and decreasing spike frequencies but was not affected by spike number. Stimulation of single, fast-spiking, putative inhibitory neurons led to a larger sensory effect compared to regular-spiking neurons, and the effect size depended only on spike irregularity. An ideal-observer analysis suggests that, under our experimental conditions, rats were using integration windows of a few hundred milliseconds or more. Our data imply that the behaving animal is sensitive to single neurons' spikes and even to their temporal patterning. Copyright © 2014 Elsevier Inc. All rights reserved.

  17. Generalized analog thresholding for spike acquisition at ultralow sampling rates.

    Science.gov (United States)

    He, Bryan D; Wein, Alex; Varshney, Lav R; Kusuma, Julius; Richardson, Andrew G; Srinivasan, Lakshminarayan

    2015-07-01

    Efficient spike acquisition techniques are needed to bridge the divide from creating large multielectrode arrays (MEA) to achieving whole-cortex electrophysiology. In this paper, we introduce generalized analog thresholding (gAT), which achieves millisecond temporal resolution with sampling rates as low as 10 Hz. Consider the torrent of data from a single 1,000-channel MEA, which would generate more than 3 GB/min using standard 30-kHz Nyquist sampling. Recent neural signal processing methods based on compressive sensing still require Nyquist sampling as a first step and use iterative methods to reconstruct spikes. Analog thresholding (AT) remains the best existing alternative, where spike waveforms are passed through an analog comparator and sampled at 1 kHz, with instant spike reconstruction. By generalizing AT, the new method reduces sampling rates another order of magnitude, detects more than one spike per interval, and reconstructs spike width. Unlike compressive sensing, the new method reveals a simple closed-form solution to achieve instant (noniterative) spike reconstruction. The base method is already robust to hardware nonidealities, including realistic quantization error and integration noise. Because it achieves these considerable specifications using hardware-friendly components like integrators and comparators, generalized AT could translate large-scale MEAs into implantable devices for scientific investigation and medical technology. Copyright © 2015 the American Physiological Society.

  18. Predictive coding of dynamical variables in balanced spiking networks.

    Science.gov (United States)

    Boerlin, Martin; Machens, Christian K; Denève, Sophie

    2013-01-01

    Two observations about the cortex have puzzled neuroscientists for a long time. First, neural responses are highly variable. Second, the level of excitation and inhibition received by each neuron is tightly balanced at all times. Here, we demonstrate that both properties are necessary consequences of neural networks that represent information efficiently in their spikes. We illustrate this insight with spiking networks that represent dynamical variables. Our approach is based on two assumptions: We assume that information about dynamical variables can be read out linearly from neural spike trains, and we assume that neurons only fire a spike if that improves the representation of the dynamical variables. Based on these assumptions, we derive a network of leaky integrate-and-fire neurons that is able to implement arbitrary linear dynamical systems. We show that the membrane voltage of the neurons is equivalent to a prediction error about a common population-level signal. Among other things, our approach allows us to construct an integrator network of spiking neurons that is robust against many perturbations. Most importantly, neural variability in our networks cannot be equated to noise. Despite exhibiting the same single unit properties as widely used population code models (e.g. tuning curves, Poisson distributed spike trains), balanced networks are orders of magnitudes more reliable. Our approach suggests that spikes do matter when considering how the brain computes, and that the reliability of cortical representations could have been strongly underestimated.

  19. Bursts generate a non-reducible spike-pattern code

    Directory of Open Access Journals (Sweden)

    Hugo G Eyherabide

    2009-05-01

    Full Text Available On the single-neuron level, precisely timed spikes can either constitute firing-rate codes or spike-pattern codes that utilize the relative timing between consecutive spikes. There has been little experimental support for the hypothesis that such temporal patterns contribute substantially to information transmission. Using grasshopper auditory receptors as a model system, we show that correlations between spikes can be used to represent behaviorally relevant stimuli. The correlations reflect the inner structure of the spike train: a succession of burst-like patterns. We demonstrate that bursts with different spike counts encode different stimulus features, such that about 20% of the transmitted information corresponds to discriminating between different features, and the remaining 80% is used to allocate these features in time. In this spike-pattern code, the "what" and the "when" of the stimuli are encoded in the duration of each burst and the time of burst onset, respectively. Given the ubiquity of burst firing, we expect similar findings also for other neural systems.

  20. A Simple Deep Learning Method for Neuronal Spike Sorting

    Science.gov (United States)

    Yang, Kai; Wu, Haifeng; Zeng, Yu

    2017-10-01

    Spike sorting is one of key technique to understand brain activity. With the development of modern electrophysiology technology, some recent multi-electrode technologies have been able to record the activity of thousands of neuronal spikes simultaneously. The spike sorting in this case will increase the computational complexity of conventional sorting algorithms. In this paper, we will focus spike sorting on how to reduce the complexity, and introduce a deep learning algorithm, principal component analysis network (PCANet) to spike sorting. The introduced method starts from a conventional model and establish a Toeplitz matrix. Through the column vectors in the matrix, we trains a PCANet, where some eigenvalue vectors of spikes could be extracted. Finally, support vector machine (SVM) is used to sort spikes. In experiments, we choose two groups of simulated data from public databases availably and compare this introduced method with conventional methods. The results indicate that the introduced method indeed has lower complexity with the same sorting errors as the conventional methods.

  1. Automated spike preparation system for Isotope Dilution Mass Spectrometry (IDMS)

    International Nuclear Information System (INIS)

    Maxwell, S.L. III; Clark, J.P.

    1990-01-01

    Isotope Dilution Mass Spectrometry (IDMS) is a method frequently employed to measure dissolved, irradiated nuclear materials. A known quantity of a unique isotope of the element to be measured (referred to as the ''spike'') is added to the solution containing the analyte. The resulting solution is chemically purified then analyzed by mass spectrometry. By measuring the magnitude of the response for each isotope and the response for the ''unique spike'' then relating this to the known quantity of the ''spike'', the quantity of the nuclear material can be determined. An automated spike preparation system was developed at the Savannah River Site (SRS) to dispense spikes for use in IDMS analytical methods. Prior to this development, technicians weighed each individual spike manually to achieve the accuracy required. This procedure was time-consuming and subjected the master stock solution to evaporation. The new system employs a high precision SMI Model 300 Unipump dispenser interfaced with an electronic balance and a portable Epson HX-20 notebook computer to automate spike preparation

  2. Calcium channel blocker poisoning

    Directory of Open Access Journals (Sweden)

    Miran Brvar

    2005-04-01

    Full Text Available Background: Calcium channel blockers act at L-type calcium channels in cardiac and vascular smooth muscles by preventing calcium influx into cells with resultant decrease in vascular tone and cardiac inotropy, chronotropy and dromotropy. Poisoning with calcium channel blockers results in reduced cardiac output, bradycardia, atrioventricular block, hypotension and shock. The findings of hypotension and bradycardia should suggest poisoning with calcium channel blockers.Conclusions: Treatment includes immediate gastric lavage and whole-bowel irrigation in case of ingestion of sustainedrelease products. All patients should receive an activated charcoal orally. Specific treatment includes calcium, glucagone and insulin, which proved especially useful in shocked patients. Supportive care including the use of catecholamines is not always effective. In the setting of failure of pharmacological therapy transvenous pacing, balloon pump and cardiopulmonary by-pass may be necessary.

  3. Dengue and Calcium

    OpenAIRE

    Shivanthan, Mitrakrishnan C; Rajapakse, Senaka

    2014-01-01

    Dengue is potentially fatal unless managed appropriately. No specific treatment is available and the mainstay of treatment is fluid management with careful monitoring, organ support, and correction of metabolic derangement. Evidence with regards to the role of calcium homeostasis in dengue is limited. Low blood calcium levels have been demonstrated in dengue infection and hypocalcemia maybe more pronounced in more severe forms. The cause of hypocalcemia is likely to be multifactorial. Calcium...

  4. Topological specificity and hierarchical network of the circadian calcium rhythm in the suprachiasmatic nucleus.

    Science.gov (United States)

    Enoki, Ryosuke; Kuroda, Shigeru; Ono, Daisuke; Hasan, Mazahir T; Ueda, Tetsuo; Honma, Sato; Honma, Ken-ichi

    2012-12-26

    The circadian pacemaker in the hypothalamic suprachiasmatic nucleus (SCN) is a hierarchical multioscillator system in which neuronal networks play crucial roles in expressing coherent rhythms in physiology and behavior. However, our understanding of the neuronal network is still incomplete. Intracellular calcium mediates the input signals, such as phase-resetting stimuli, to the core molecular loop involving clock genes for circadian rhythm generation and the output signals from the loop to various cellular functions, including changes in neurotransmitter release. Using a unique large-scale calcium imaging method with genetically encoded calcium sensors, we visualized intracellular calcium from the entire surface of SCN slice in culture including the regions where autonomous clock gene expression was undetectable. We found circadian calcium rhythms at a single-cell level in the SCN, which were topologically specific with a larger amplitude and more delayed phase in the ventral region than the dorsal. The robustness of the rhythm was reduced but persisted even after blocking the neuronal firing with tetrodotoxin (TTX). Notably, TTX dissociated the circadian calcium rhythms between the dorsal and ventral SCN. In contrast, a blocker of gap junctions, carbenoxolone, had only a minor effect on the calcium rhythms at both the single-cell and network levels. These results reveal the topological specificity of the circadian calcium rhythm in the SCN and the presence of coupled regional pacemakers in the dorsal and ventral regions. Neuronal firings are not necessary for the persistence of the calcium rhythms but indispensable for the hierarchical organization of rhythmicity in the SCN.

  5. Grain price spikes and beggar-thy-neighbor policy responses

    DEFF Research Database (Denmark)

    Boysen, Ole; Jensen, Hans Grinsted

    Upward spikes in the international price of food in recent years led some countries to raise export barriers, thereby exacerbating both the price spike and reducing the terms of trade for food-importing countries (beggaring their neighbors). At the same time, and for similar political......-economy reasons, numerous food-importing countries reduced or suspended their import tariffs, and some even provided food import subsidies -- which also exacerbated the international price spike, thus turning the terms of trade even further against food-importing countries. This issue became a major item...

  6. Boobs, Boxing, and Bombs: Problematizing the Entertainment of Spike TV

    OpenAIRE

    Walton, Gerald; Potvin, L.

    2009-01-01

    Spike is the only television network in North America “for men.” Its motto, “Get more action,” is suggestive of pursuits of various forms of violence. We conceptualize Spike not as trivial entertainment, but rather as a form of pop culture that erodes the gains of feminists who have challenged the prevalence of normalized hegemonic masculinity (HM). Our paper highlights themes of Spike content, and connects those themes to the literature on HM. Moreover, we validate the identities and lives ...

  7. MR imaging of intracellular and extracellular deoxyhemoglobin

    International Nuclear Information System (INIS)

    Janick, P.A.; Grossman, R.I.; Asakura, T.

    1989-01-01

    MR imaging was performed on varying concentrations of intracellular and extracellular deoxyhemoglobin as well as varying proportions of deoxyhemoglobin and oxyhemoglobin in vitro at 1.5T with use of standard spin-echo and gradient-refocused spin sequences. This study indicates that susceptibility-induced T2 shortening occurs over a broad range of intracellular deoxyhemoglobin concentrations (maximal at hematocrits between 20% and 45%), reflecting diffusional effects at the cellular level. T2* gradient-echo imaging enhances the observed hypointensity in images of intracellular deoxyhemoglobin. The characteristic MR appearance of acute hemotomas can be modeled by the behavior of intracellular and extracellular deoxyhemoglobin and oxyhemoglobin

  8. Heterogeneity of Purkinje cell simple spike-complex spike interactions: zebrin- and non-zebrin-related variations.

    Science.gov (United States)

    Tang, Tianyu; Xiao, Jianqiang; Suh, Colleen Y; Burroughs, Amelia; Cerminara, Nadia L; Jia, Linjia; Marshall, Sarah P; Wise, Andrew K; Apps, Richard; Sugihara, Izumi; Lang, Eric J

    2017-08-01

    Cerebellar Purkinje cells (PCs) generate two types of action potentials, simple and complex spikes. Although they are generated by distinct mechanisms, interactions between the two spike types exist. Zebrin staining produces alternating positive and negative stripes of PCs across most of the cerebellar cortex. Thus, here we compared simple spike-complex spike interactions both within and across zebrin populations. Simple spike activity undergoes a complex modulation preceding and following a complex spike. The amplitudes of the pre- and post-complex spike modulation phases were correlated across PCs. On average, the modulation was larger for PCs in zebrin positive regions. Correlations between aspects of the complex spike waveform and simple spike activity were found, some of which varied between zebrin positive and negative PCs. The implications of the results are discussed with regard to hypotheses that complex spikes are triggered by rises in simple spike activity for either motor learning or homeostatic functions. Purkinje cells (PCs) generate two types of action potentials, called simple and complex spikes (SSs and CSs). We first investigated the CS-associated modulation of SS activity and its relationship to the zebrin status of the PC. The modulation pattern consisted of a pre-CS rise in SS activity, and then, following the CS, a pause, a rebound, and finally a late inhibition of SS activity for both zebrin positive (Z+) and negative (Z-) cells, though the amplitudes of the phases were larger in Z+ cells. Moreover, the amplitudes of the pre-CS rise with the late inhibitory phase of the modulation were correlated across PCs. In contrast, correlations between modulation phases across CSs of individual PCs were generally weak. Next, the relationship between CS spikelets and SS activity was investigated. The number of spikelets/CS correlated with the average SS firing rate only for Z+ cells. In contrast, correlations across CSs between spikelet numbers and the

  9. Perceptron learning rule derived from spike-frequency adaptation and spike-time-dependent plasticity.

    Science.gov (United States)

    D'Souza, Prashanth; Liu, Shih-Chii; Hahnloser, Richard H R

    2010-03-09

    It is widely believed that sensory and motor processing in the brain is based on simple computational primitives rooted in cellular and synaptic physiology. However, many gaps remain in our understanding of the connections between neural computations and biophysical properties of neurons. Here, we show that synaptic spike-time-dependent plasticity (STDP) combined with spike-frequency adaptation (SFA) in a single neuron together approximate the well-known perceptron learning rule. Our calculations and integrate-and-fire simulations reveal that delayed inputs to a neuron endowed with STDP and SFA precisely instruct neural responses to earlier arriving inputs. We demonstrate this mechanism on a developmental example of auditory map formation guided by visual inputs, as observed in the external nucleus of the inferior colliculus (ICX) of barn owls. The interplay of SFA and STDP in model ICX neurons precisely transfers the tuning curve from the visual modality onto the auditory modality, demonstrating a useful computation for multimodal and sensory-guided processing.

  10. Cyclic AMP Pathway Activation and Extracellular Zinc Induce Rapid Intracellular Zinc Mobilization in Candida albicans

    Science.gov (United States)

    Kjellerup, Lasse; Winther, Anne-Marie L.; Wilson, Duncan; Fuglsang, Anja T.

    2018-01-01

    Zinc is an essential micronutrient, required for a range of zinc-dependent enzymes and transcription factors. In mammalian cells, zinc serves as a second messenger molecule. However, a role for zinc in signaling has not yet been established in the fungal kingdom. Here, we used the intracellular zinc reporter, zinbo-5, which allowed visualization of zinc in the endoplasmic reticulum and other components of the internal membrane system in Candida albicans. We provide evidence for a link between cyclic AMP/PKA- and zinc-signaling in this major human fungal pathogen. Glucose stimulation, which triggers a cyclic AMP spike in this fungus resulted in rapid intracellular zinc mobilization and this “zinc flux” could be stimulated with phosphodiesterase inhibitors and blocked via inhibition of adenylate cyclase or PKA. A similar mobilization of intracellular zinc was generated by stimulation of cells with extracellular zinc and this effect could be reversed with the chelator EDTA. However, zinc-induced zinc flux was found to be cyclic AMP independent. In summary, we show that activation of the cyclic AMP/PKA pathway triggers intracellular zinc mobilization in a fungus. To our knowledge, this is the first described link between cyclic AMP signaling and zinc homeostasis in a human fungal pathogen. PMID:29619016

  11. Action of serotonin antagonists on cytoplasmic calcium levels in early embryos of sea urchin Lytechinus pictus.

    Science.gov (United States)

    Shmukler, Y B; Buznikov, G A; Whitaker, M J

    1999-03-01

    Possible interaction of the serotonergic system with intracellular calcium mechanisms was investigated using techniques of ratio imaging measurement of intracellular Ca2+ and confocal microscopy in cleaving embryos of sea urchin Lytechinus pictus. Some serotonin antagonists specifically increase free intracellular Ca2+ and evoke transient regression of the first cleavage furrow, suggesting possible linkage of serotonergic and calcium mechanisms in the regulation of cellular events during cleavage divisions. These effects were more pronounced in the experiments with hydrophilic 5-HT-antagonists, quarternary ammonium salts that do not penetrate the cell membrane. Thus, it appears that 5-HT-receptors which mediate these effects are localised on the cell membrane, whereas previously studied receptors mediating the cytostatic action of lipophilic 5-HT-antagonists are localised intracellularly.

  12. Stochastic optimal control of single neuron spike trains

    DEFF Research Database (Denmark)

    Iolov, Alexandre; Ditlevsen, Susanne; Longtin, Andrë

    2014-01-01

    stimulation of a neuron to achieve a target spike train under the physiological constraint to not damage tissue. Approach. We pose a stochastic optimal control problem to precisely specify the spike times in a leaky integrate-and-fire (LIF) model of a neuron with noise assumed to be of intrinsic or synaptic...... to the spike times (open-loop control). Main results. We have developed a stochastic optimal control algorithm to obtain precise spike times. It is applicable in both the supra-threshold and sub-threshold regimes, under open-loop and closed-loop conditions and with an arbitrary noise intensity; the accuracy...... into account physiological constraints on the control. A precise and robust targeting of neural activity based on stochastic optimal control has great potential for regulating neural activity in e.g. prosthetic applications and to improve our understanding of the basic mechanisms by which neuronal firing...

  13. Higher Order Spike Synchrony in Prefrontal Cortex during visual memory

    Directory of Open Access Journals (Sweden)

    Gordon ePipa

    2011-06-01

    Full Text Available Precise temporal synchrony of spike firing has been postulated as an important neuronal mechanism for signal integration and the induction of plasticity in neocortex. As prefrontal cortex plays an important role in organizing memory and executive functions, the convergence of multiple visual pathways onto PFC predicts that neurons should preferentially synchronize their spiking when stimulus information is processed. Furthermore, synchronous spike firing should intensify if memory processes require the induction of neuronal plasticity, even if this is only for short-term. Here we show with multiple simultaneously recorded units in ventral prefrontal cortex that neurons participate in 3 ms precise synchronous discharges distributed across multiple sites separated by at least 500 µm. The frequency of synchronous firing is modulated by behavioral performance and is specific for the memorized visual stimuli. In particular, during the memory period in which activity is not stimulus driven, larger groups of up to 7 sites exhibit performance dependent modulation of their spike synchronization.

  14. Sonar target localization based on spike coded spectrograms

    Directory of Open Access Journals (Sweden)

    Bertrand FONTAINE

    2006-12-01

    Full Text Available Target location is coded into the pattern of spikes that run up the auditory nerve to the bat's brain. Realistic scenes containing multiple, closely spaced, reflectors give rise to complex echo signals consisting of multiple filtered copies of the bat's own vocalisation. Some of this filtering is due to the directivity of the bat’s reception system i.e., the outer ears, and some of it is due to sound absorption and the reflection process. The analysis below concentrates on the conspicuous ridges (notches these filter operations give rise to in the time-frequency representation of the echo as produced by the bat's inner ear. Assuming multiple threshold detecting neurons for each frequency channel it is shown how the distribution of spike times within the generated spike bursts is linked to the presence and characteristics of these notches. A neural network decoding the spike bursts in terms of target location is described.

  15. Human β-Cell Proliferation and Intracellular Signaling: Part 3

    Science.gov (United States)

    Hussain, Mehboob A.; García-Ocaña, Adolfo; Vasavada, Rupangi C.; Bhushan, Anil; Bernal-Mizrachi, Ernesto

    2015-01-01

    This is the third in a series of Perspectives on intracellular signaling pathways coupled to proliferation in pancreatic β-cells. We contrast the large knowledge base in rodent β-cells with the more limited human database. With the increasing incidence of type 1 diabetes and the recognition that type 2 diabetes is also due in part to a deficiency of functioning β-cells, there is great urgency to identify therapeutic approaches to expand human β-cell numbers. Therapeutic approaches might include stem cell differentiation, transdifferentiation, or expansion of cadaver islets or residual endogenous β-cells. In these Perspectives, we focus on β-cell proliferation. Past Perspectives reviewed fundamental cell cycle regulation and its upstream regulation by insulin/IGF signaling via phosphatidylinositol-3 kinase/mammalian target of rapamycin signaling, glucose, glycogen synthase kinase-3 and liver kinase B1, protein kinase Cζ, calcium-calcineurin–nuclear factor of activated T cells, epidermal growth factor/platelet-derived growth factor family members, Wnt/β-catenin, leptin, and estrogen and progesterone. Here, we emphasize Janus kinase/signal transducers and activators of transcription, Ras/Raf/extracellular signal–related kinase, cadherins and integrins, G-protein–coupled receptors, and transforming growth factor β signaling. We hope these three Perspectives will serve to introduce these pathways to new researchers and will encourage additional investigators to focus on understanding how to harness key intracellular signaling pathways for therapeutic human β-cell regeneration for diabetes. PMID:25999530

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

    Directory of Open Access Journals (Sweden)

    Katrin Feldbauer

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

  17. Differential inhibitory response to telcagepant on αCGRP induced vasorelaxation and intracellular Ca(2+) levels in the perfused and non-perfused isolated rat middle cerebral artery

    DEFF Research Database (Denmark)

    Erdling, André; Sheykhzade, Majid; Edvinsson, Lars

    2017-01-01

    and tension in rat middle cerebral arteries (MCA) by pressurized arteriography, FURA-2/wire myography and immunohistochemistry. METHODS: A pressurized arteriograph system was used to evaluate changes in MCA tension when subjected to CGRP and/or telcagepant. Intracellular calcium levels were evaluated using......, while abluminal telcagepant inhibited the relaxation (10(-6) M). Using the FURA-2 method in combination with wire myography we observed that αCGRP reduced intracellular calcium levels and in parallel the vascular tone. Telcagepant (10(-6) M) inhibited both vasorelaxation and drop in intracellular...... calcium levels. Both functional components of the CGRP receptor, CLR (calcitonin receptor-like receptor) and RAMP1 (receptor activity modifying peptide 1) were found in the smooth muscle cells but not in the endothelial cells of the cerebral vasculature. CONCLUSIONS: This study thus demonstrates...

  18. Discovery and Development of Calcium Channel Blockers

    Science.gov (United States)

    Godfraind, Théophile

    2017-01-01

    In the mid 1960s, experimental work on molecules under screening as coronary dilators allowed the discovery of the mechanism of calcium entry blockade by drugs later named calcium channel blockers. This paper summarizes scientific research on these small molecules interacting directly with L-type voltage-operated calcium channels. It also reports on experimental approaches translated into understanding of their therapeutic actions. The importance of calcium in muscle contraction was discovered by Sidney Ringer who reported this fact in 1883. Interest in the intracellular role of calcium arose 60 years later out of Kamada (Japan) and Heibrunn (USA) experiments in the early 1940s. Studies on pharmacology of calcium function were initiated in the mid 1960s and their therapeutic applications globally occurred in the the 1980s. The first part of this report deals with basic pharmacology in the cardiovascular system particularly in isolated arteries. In the section entitled from calcium antagonists to calcium channel blockers, it is recalled that drugs of a series of diphenylpiperazines screened in vivo on coronary bed precontracted by angiotensin were initially named calcium antagonists on the basis of their effect in depolarized arteries contracted by calcium. Studies on arteries contracted by catecholamines showed that the vasorelaxation resulted from blockade of calcium entry. Radiochemical and electrophysiological studies performed with dihydropyridines allowed their cellular targets to be identified with L-type voltage-operated calcium channels. The modulated receptor theory helped the understanding of their variation in affinity dependent on arterial cell membrane potential and promoted the terminology calcium channel blocker (CCB) of which the various chemical families are introduced in the paper. In the section entitled tissue selectivity of CCBs, it is shown that characteristics of the drug, properties of the tissue, and of the stimuli are important factors of

  19. Discovery and Development of Calcium Channel Blockers.

    Science.gov (United States)

    Godfraind, Théophile

    2017-01-01

    In the mid 1960s, experimental work on molecules under screening as coronary dilators allowed the discovery of the mechanism of calcium entry blockade by drugs later named calcium channel blockers. This paper summarizes scientific research on these small molecules interacting directly with L-type voltage-operated calcium channels. It also reports on experimental approaches translated into understanding of their therapeutic actions. The importance of calcium in muscle contraction was discovered by Sidney Ringer who reported this fact in 1883. Interest in the intracellular role of calcium arose 60 years later out of Kamada (Japan) and Heibrunn (USA) experiments in the early 1940s. Studies on pharmacology of calcium function were initiated in the mid 1960s and their therapeutic applications globally occurred in the the 1980s. The first part of this report deals with basic pharmacology in the cardiovascular system particularly in isolated arteries. In the section entitled from calcium antagonists to calcium channel blockers, it is recalled that drugs of a series of diphenylpiperazines screened in vivo on coronary bed precontracted by angiotensin were initially named calcium antagonists on the basis of their effect in depolarized arteries contracted by calcium. Studies on arteries contracted by catecholamines showed that the vasorelaxation resulted from blockade of calcium entry. Radiochemical and electrophysiological studies performed with dihydropyridines allowed their cellular targets to be identified with L-type voltage-operated calcium channels. The modulated receptor theory helped the understanding of their variation in affinity dependent on arterial cell membrane potential and promoted the terminology calcium channel blocker (CCB) of which the various chemical families are introduced in the paper. In the section entitled tissue selectivity of CCBs, it is shown that characteristics of the drug, properties of the tissue, and of the stimuli are important factors of

  20. Discovery and Development of Calcium Channel Blockers

    Directory of Open Access Journals (Sweden)

    Théophile Godfraind

    2017-05-01

    Full Text Available In the mid 1960s, experimental work on molecules under screening as coronary dilators allowed the discovery of the mechanism of calcium entry blockade by drugs later named calcium channel blockers. This paper summarizes scientific research on these small molecules interacting directly with L-type voltage-operated calcium channels. It also reports on experimental approaches translated into understanding of their therapeutic actions. The importance of calcium in muscle contraction was discovered by Sidney Ringer who reported this fact in 1883. Interest in the intracellular role of calcium arose 60 years later out of Kamada (Japan and Heibrunn (USA experiments in the early 1940s. Studies on pharmacology of calcium function were initiated in the mid 1960s and their therapeutic applications globally occurred in the the 1980s. The first part of this report deals with basic pharmacology in the cardiovascular system particularly in isolated arteries. In the section entitled from calcium antagonists to calcium channel blockers, it is recalled that drugs of a series of diphenylpiperazines screened in vivo on coronary bed precontracted by angiotensin were initially named calcium antagonists on the basis of their effect in depolarized arteries contracted by calcium. Studies on arteries contracted by catecholamines showed that the vasorelaxation resulted from blockade of calcium entry. Radiochemical and electrophysiological studies performed with dihydropyridines allowed their cellular targets to be identified with L-type voltage-operated calcium channels. The modulated receptor theory helped the understanding of their variation in affinity dependent on arterial cell membrane potential and promoted the terminology calcium channel blocker (CCB of which the various chemical families are introduced in the paper. In the section entitled tissue selectivity of CCBs, it is shown that characteristics of the drug, properties of the tissue, and of the stimuli are

  1. Spatiotemporal Dynamics and Reliable Computations in Recurrent Spiking Neural Networks

    Science.gov (United States)

    Pyle, Ryan; Rosenbaum, Robert

    2017-01-01

    Randomly connected networks of excitatory and inhibitory spiking neurons provide a parsimonious model of neural variability, but are notoriously unreliable for performing computations. We show that this difficulty is overcome by incorporating the well-documented dependence of connection probability on distance. Spatially extended spiking networks exhibit symmetry-breaking bifurcations and generate spatiotemporal patterns that can be trained to perform dynamical computations under a reservoir computing framework.

  2. Spike Neural Models Part II: Abstract Neural Models

    OpenAIRE

    Johnson, Melissa G.; Chartier, Sylvain

    2018-01-01

    Neurons are complex cells that require a lot of time and resources to model completely. In spiking neural networks (SNN) though, not all that complexity is required. Therefore simple, abstract models are often used. These models save time, use less computer resources, and are easier to understand. This tutorial presents two such models: Izhikevich's model, which is biologically realistic in the resulting spike trains but not in the parameters, and the Leaky Integrate and Fire (LIF) model whic...

  3. Characteristics of Spike motion in World top lever volleyball players

    OpenAIRE

    黒川, 貞生; 森田, 恭光; 亀ヶ谷, 純一; 加藤, 浩人; 松井, 泰二; 鈴木, 陽一; 矢島, 忠明

    2008-01-01

    The purpose of this study was to investigate the characteristics of spike motion in world top level volleyball players. Front- and back-spike motions were recorded by high-speed video camera system operating at 250Hz to obtain three dimensional coordinates of the body segments and the center of the ball. The velocity of the ball, wrist, shoulder and trunk twist angle was calculated using motion analyzer. There is no significant relationship between the initial ball velocity and the velocity o...

  4. EPILEPTIC ENCEPHALOPATHY WITH CONTINUOUS SPIKES-WAVES ACTIVITY DURING SLEEP

    OpenAIRE

    E. D. Belousova

    2012-01-01

    The author represents the review and discussion of current scientific literature devoted to epileptic encephalopathy with continuous spikes-waves activity during sleep — the special form of partly reversible age-dependent epileptic encephalopathy, characterized by triad of symptoms: continuous prolonged epileptiform (spike-wave) activity on EEG in sleep, epileptic seizures and cognitive disorders. The author describes the aspects of classification, pathogenesis and etiology, prevalence, clini...

  5. Nonlinear evolution of single spike in Richtmyer-Meshkov instability

    International Nuclear Information System (INIS)

    Fukuda, Y.; Nishihara, K.; Wouchuk, J.G.

    2000-01-01

    Nonlinear evolution of single spike structure and vortex in the Richtmyer-Meshkov instability is investigated with the use of a two-dimensional hydrodynamic code. It is shown that singularity appears in the vorticity left by transmitted and reflected shocks at a corrugated interface. This singularity results in opposite sign of vorticity along the interface that causes double spiral structure of the spike. (authors)

  6. Intracellular Polyamines Enhance Astrocytic Coupling

    Science.gov (United States)

    Benedikt, Jan; Inyushin, Mikhail; Kucheryavykh, Yuriy V.; Rivera, Yomarie; Kucheryavykh, Lilia Y.; Nichols, Colin G.; Eaton, Misty J.; Skatchkov, Serguei N.

    2013-01-01

    Spermine (SPM) and spermidine (SPD), endogenous polyamines (PA) with the ability to modulate various ion channels and receptors in the brain, exert neuroprotective, antidepressant, antioxidant and other effects in vivo such as increasing longevity. These PA are preferably accumulated in astrocytes, and we hypothesized that SPM increases glial intercellular communication by interacting with glial gap junctions. Results obtained in situ, using Lucifer yellow propagation in the astrocytic syncitium of 21–25 day old rat CA1 hippocampal slices, showed reduced coupling when astrocytes were dialyzed with standard intracellular solutions (ICS) without SPM. However, there was a robust increase in the spreading of Lucifer yellow via gap junctions to neighboring astrocytes when the cells were patched with ICS containing 1 mM SPM; a physiological concentration in glia. Lucifer yellow propagation was inhibited by gap junction blockers. Our findings show that the glial syncitium propagates SPM via gap junctions and further suggest a new role of polyamines in the regulation of the astroglial network in both normal and pathological conditions. PMID:23076119

  7. DIHYDROPYRIDINE CALCIUM- CHANNELBLOCKERSFOR ...

    African Journals Online (AJOL)

    and degenerative dementias the calcium-channel blocker nimodipine, compared with placebo, slightly improved the. MMSE scores." Thus, an additional or alternative explanation, albeit still unproven, could involve specific neuroprotection conferred by calcium-channel blockade.~Indeed, the ageing brain loses its ability to ...

  8. Calcium channel blocker overdose

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/002580.htm Calcium-channel blocker overdose To use the sharing features on this ... vary. However, the main ingredient is called a calcium-channel antagonist. It helps decrease the heart's pumping strength, which ...

  9. Extracellular Calcium and Magnesium

    African Journals Online (AJOL)

    ABSTRACT. The cause of preeclampsia remains unknown and calcium and magnesium supplement are being suggested as means of prevention. The objective of this study was to assess magnesium and calcium in the plasma and cerebrospinal fluid of Nigerian women with preedamp sia and eclampsia. Setting was ...

  10. Calcium and bones

    Science.gov (United States)

    ... eat in their diet. Vitamin D is the hormone that helps the gut absorb more calcium. Many older adults have common risks that make bone health worse. Calcium intake in the diet (milk, cheese, yogurt) is low. Vitamin D levels are ...

  11. Visualisation of an nsPEF induced calcium wave using the genetically encoded calcium indicator GCaMP in U87 human glioblastoma cells.

    Science.gov (United States)

    Carr, Lynn; Bardet, Sylvia M; Arnaud-Cormos, Delia; Leveque, Philippe; O'Connor, Rodney P

    2018-02-01

    Cytosolic, synthetic chemical calcium indicators are typically used to visualise the rapid increase in intracellular calcium ion concentration that follows nanosecond pulsed electric field (nsPEF) application. This study looks at the application of genetically encoded calcium indicators (GECIs) to investigate the spatiotemporal nature of nsPEF-induced calcium signals using fluorescent live cell imaging. Calcium responses to 44kV/cm, 10ns pulses were observed in U87-MG cells expressing either a plasma membrane targeted GECI (GCaMP5-G), or one cytosolically expressed (GCaMP6-S), and compared to the response of cells loaded with cytosolic or plasma membrane targeted chemical calcium indicators. Application of 100 pulses, to cells containing plasma membrane targeted indicators, revealed a wave of calcium across the cell initiating at the cathode side. A similar spatial wave was not observed with cytosolic indicators with mobile calcium buffering properties. The speed of the wave was related to pulse application frequency and it was not propagated by calcium induced calcium release. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. The Omega-Infinity Limit of Single Spikes

    CERN Document Server

    Axenides, Minos; Linardopoulos, Georgios

    A new infinite-size limit of strings in RxS2 is presented. The limit is obtained from single spike strings by letting their angular velocity omega become infinite. We derive the energy-momenta relation of omega-infinity single spikes as their linear velocity v-->1 and their angular momentum J-->1. Generally, the v-->1, J-->1 limit of single spikes is singular and has to be excluded from the spectrum and be studied separately. We discover that the dispersion relation of omega-infinity single spikes contains logarithms in the limit J-->1. This result is somewhat surprising, since the logarithmic behavior in the string spectra is typically associated with their motion in non-compact spaces such as AdS. Omega-infinity single spikes seem to completely cover the surface of the 2-sphere they occupy, so that they may essentially be viewed as some sort of "brany strings". A proof of the sphere-filling property of omega-infinity single spikes is given in the appendix.

  13. Automatic fitting of spiking neuron models to electrophysiological recordings

    Directory of Open Access Journals (Sweden)

    Cyrille Rossant

    2010-03-01

    Full Text Available Spiking models can accurately predict the spike trains produced by cortical neurons in response to somatically injected currents. Since the specific characteristics of the model depend on the neuron, a computational method is required to fit models to electrophysiological recordings. The fitting procedure can be very time consuming both in terms of computer simulations and in terms of code writing. We present algorithms to fit spiking models to electrophysiological data (time-varying input and spike trains that can run in parallel on graphics processing units (GPUs. The model fitting library is interfaced with Brian, a neural network simulator in Python. If a GPU is present it uses just-in-time compilation to translate model equations into optimized code. Arbitrary models can then be defined at script level and run on the graphics card. This tool can be used to obtain empirically validated spiking models of neurons in various systems. We demonstrate its use on public data from the INCF Quantitative Single-Neuron Modeling 2009 competition by comparing the performance of a number of neuron spiking models.

  14. Absolute Ca Isotopic Measurement Using an Improved Double Spike Technique

    Directory of Open Access Journals (Sweden)

    Jason Jiun-San Shen

    2009-01-01

    Full Text Available A new vector analytical method has been developed in order to obtain the true isotopic composition of the 42Ca-48Ca double spike. This is achieved by using two different sample-spike mixtures combined with the double spike and natural Ca data. Be cause the natural sample (two mixtures and the spike should all lie on a single mixing line, we are able to con strain the true isotopic composition of our double spike using this new approach. Once the isotopic composition of the Ca double spike is established, we are able to obtain the true Ca isotopic composition of the NIST Ca standard SRM915a, 40Ca/44Ca = 46.537 ± 2 (2sm, n = 55, 42Ca/44Ca = 0.31031 ± 1, 43Ca/44Ca = 0.06474 ± 1, and 48Ca/44Ca = 0.08956 ± 1. De spite an off set of 1.3% in 40Ca/44Ca between our result and the previously re ported value (Russell et al. 1978, our data indicate an off set of 1.89__in 40Ca/44Ca between SRM915a and seawater, entirely consistent with the published results.

  15. Microtubule-Dependent Mitochondria Alignment Regulates Calcium Release in Response to Nanomechanical Stimulus in Heart Myocytes

    Directory of Open Access Journals (Sweden)

    Michele Miragoli

    2016-01-01

    Full Text Available Arrhythmogenesis during heart failure is a major clinical problem. Regional electrical gradients produce arrhythmias, and cellular ionic transmembrane gradients are its originators. We investigated whether the nanoscale mechanosensitive properties of cardiomyocytes from failing hearts have a bearing upon the initiation of abnormal electrical activity. Hydrojets through a nanopipette indent specific locations on the sarcolemma and initiate intracellular calcium release in both healthy and heart failure cardiomyocytes, as well as in human failing cardiomyocytes. In healthy cells, calcium is locally confined, whereas in failing cardiomyocytes, calcium propagates. Heart failure progressively stiffens the membrane and displaces sub-sarcolemmal mitochondria. Colchicine in healthy cells mimics the failing condition by stiffening the cells, disrupting microtubules, shifting mitochondria, and causing calcium release. Uncoupling the mitochondrial proton gradient abolished calcium initiation in both failing and colchicine-treated cells. We propose the disruption of microtubule-dependent mitochondrial mechanosensor microdomains as a mechanism for abnormal calcium release in failing heart.

  16. Intracellular signal modulation by nanomaterials.

    Science.gov (United States)

    Hussain, Salik; Garantziotis, Stavros; Rodrigues-Lima, Fernando; Dupret, Jean-Marie; Baeza-Squiban, Armelle; Boland, Sonja

    2014-01-01

    A thorough understanding of the interactions of nanomaterials with biological systems and the resulting activation of signal transduction pathways is essential for the development of safe and consumer friendly nanotechnology. Here we present an overview of signaling pathways induced by nanomaterial exposures and describe the possible correlation of their physicochemical characteristics with biological outcomes. In addition to the hierarchical oxidative stress model and a review of the intrinsic and cell-mediated mechanisms of reactive oxygen species (ROS) generating capacities of nanomaterials, we also discuss other oxidative stress dependent and independent cellular signaling pathways. Induction of the inflammasome, calcium signaling, and endoplasmic reticulum stress are reviewed. Furthermore, the uptake mechanisms can be of crucial importance for the cytotoxicity of nanomaterials and membrane-dependent signaling pathways have also been shown to be responsible for cellular effects of nanomaterials. Epigenetic regulation by nanomaterials, effects of nanoparticle-protein interactions on cell signaling pathways, and the induction of various cell death modalities by nanomaterials are described. We describe the common trigger mechanisms shared by various nanomaterials to induce cell death pathways and describe the interplay of different modalities in orchestrating the final outcome after nanomaterial exposures. A better understanding of signal modulations induced by nanomaterials is not only essential for the synthesis and design of safer nanomaterials but will also help to discover potential nanomedical applications of these materials. Several biomedical applications based on the different signaling pathways induced by nanomaterials are already proposed and will certainly gain a great deal of attraction in the near future.

  17. Exposure dose response relationships of the freshwater bivalve Hyridella australis to cadmium spiked sediments

    International Nuclear Information System (INIS)

    Marasinghe Wadige, Chamani P.M.; Maher, William A.; Taylor, Anne M.; Krikowa, Frank

    2014-01-01

    Highlights: • The exposure–dose–response approach was used to assess cadmium exposure and toxicity. • Accumulated cadmium in H. australis reflected the sediment cadmium exposure. • Spill over of cadmium into the biologically active pool was observed. • Increased cadmium resulted in measurable biological effects. • H. australis has the potential to be a cadmium biomonitor in freshwater environments. - Abstract: To understand how benthic biota may respond to the additive or antagonistic effects of metal mixtures in the environment it is first necessary to examine their responses to the individual metals. In this context, laboratory controlled single metal-spiked sediment toxicity tests are useful to assess this. The exposure–dose–response relationships of Hyridella australis to cadmium-spiked sediments were, therefore, investigated in laboratory microcosms. H. australis was exposed to individual cadmium spiked sediments (<0.05 (control), 4 ± 0.3 (low) and 15 ± 1 (high) μg/g dry mass) for 28 days. Dose was measured as cadmium accumulation in whole soft body and individual tissues at weekly intervals over the exposure period. Dose was further examined as sub-cellular localisation of cadmium in hepatopancreas tissues. The biological responses in terms of enzymatic and cellular biomarkers were measured in hepatopancreas tissues at day 28. H. australis accumulated cadmium from spiked sediments with an 8-fold (low exposure organisms) and 16-fold (high exposure organisms) increase at day 28 compared to control organisms. The accumulated tissue cadmium concentrations reflected the sediment cadmium exposure at day 28. Cadmium accumulation in high exposure organisms was inversely related to the tissue calcium concentrations. Gills of H. australis showed significantly higher cadmium accumulation than the other tissues. Accumulated cadmium in biologically active and biologically detoxified metal pools was not significantly different in cadmium exposed

  18. Exposure dose response relationships of the freshwater bivalve Hyridella australis to cadmium spiked sediments

    Energy Technology Data Exchange (ETDEWEB)

    Marasinghe Wadige, Chamani P.M., E-mail: chamani.marasinghe.wadige@canberra.edu.au; Maher, William A.; Taylor, Anne M.; Krikowa, Frank

    2014-07-01

    Highlights: • The exposure–dose–response approach was used to assess cadmium exposure and toxicity. • Accumulated cadmium in H. australis reflected the sediment cadmium exposure. • Spill over of cadmium into the biologically active pool was observed. • Increased cadmium resulted in measurable biological effects. • H. australis has the potential to be a cadmium biomonitor in freshwater environments. - Abstract: To understand how benthic biota may respond to the additive or antagonistic effects of metal mixtures in the environment it is first necessary to examine their responses to the individual metals. In this context, laboratory controlled single metal-spiked sediment toxicity tests are useful to assess this. The exposure–dose–response relationships of Hyridella australis to cadmium-spiked sediments were, therefore, investigated in laboratory microcosms. H. australis was exposed to individual cadmium spiked sediments (<0.05 (control), 4 ± 0.3 (low) and 15 ± 1 (high) μg/g dry mass) for 28 days. Dose was measured as cadmium accumulation in whole soft body and individual tissues at weekly intervals over the exposure period. Dose was further examined as sub-cellular localisation of cadmium in hepatopancreas tissues. The biological responses in terms of enzymatic and cellular biomarkers were measured in hepatopancreas tissues at day 28. H. australis accumulated cadmium from spiked sediments with an 8-fold (low exposure organisms) and 16-fold (high exposure organisms) increase at day 28 compared to control organisms. The accumulated tissue cadmium concentrations reflected the sediment cadmium exposure at day 28. Cadmium accumulation in high exposure organisms was inversely related to the tissue calcium concentrations. Gills of H. australis showed significantly higher cadmium accumulation than the other tissues. Accumulated cadmium in biologically active and biologically detoxified metal pools was not significantly different in cadmium exposed

  19. Weighted spiking neural P systems with structural plasticity working in sequential mode based on maximum spike number

    Science.gov (United States)

    Sun, Mingming; Qu, Jianhua

    2017-10-01

    Spiking neural P systems (SNP systems, in short) are a group of parallel and distributed computing devices inspired by the function and structure of spiking neurons. Recently, a new variant of SNP systems, called SNP systems with structural plasticity (SNPSP systems, in short) was proposed. In SNPSP systems, neuron can use plasticity ru les to create and delete synapses. In this work, we consider many restrictions sequentiality on SNPSP systems: (1) neuron with the maximum number of spikes is chosen to fire; (2) we use the weighted synapses. Specifically, we investigate the computational power of weighted SNPSP systems working in the sequential mode based on maximum spike number (WSNPSPM systems, in short) and we proved that SNPSP systems with these new restrictions are universal as generating devices.

  20. A Markovian Entropy Measure for the Analysis of Calcium Activity Time Series.

    Directory of Open Access Journals (Sweden)

    John P Marken

    Full Text Available Methods to analyze the dynamics of calcium activity often rely on visually distinguishable features in time series data such as spikes, waves, or oscillations. However, systems such as the developing nervous system display a complex, irregular type of calcium activity which makes the use of such methods less appropriate. Instead, for such systems there exists a class of methods (including information theoretic, power spectral, and fractal analysis approaches which use more fundamental properties of the time series to analyze the observed calcium dynamics. We present a new analysis method in this class, the Markovian Entropy measure, which is an easily implementable calcium time series analysis method which represents the observed calcium activity as a realization of a Markov Process and describes its dynamics in terms of the level of predictability underlying the transitions between the states of the process. We applied our and other commonly used calcium analysis methods on a dataset from Xenopus laevis neural progenitors which displays irregular calcium activity and a dataset from murine synaptic neurons which displays activity time series that are well-described by visually-distinguishable features. We find that the Markovian Entropy measure is able to distinguish between biologically distinct populations in both datasets, and that it can separate biologically distinct populations to a greater extent than other methods in the dataset exhibiting irregular calcium activity. These results support the benefit of using the Markovian Entropy measure to analyze calcium dynamics, particularly for studies using time series data which do not exhibit easily distinguishable features.

  1. Spike Pattern Structure Influences Synaptic Efficacy Variability under STDP and Synaptic Homeostasis. II: Spike Shuffling Methods on LIF Networks

    Science.gov (United States)

    Bi, Zedong; Zhou, Changsong

    2016-01-01

    Synapses may undergo variable changes during plasticity because of the variability of spike patterns such as temporal stochasticity and spatial randomness. Here, we call the variability of synaptic weight changes during plasticity to be efficacy variability. In this paper, we investigate how four aspects of spike pattern statistics (i.e., synchronous firing, burstiness/regularity, heterogeneity of rates and heterogeneity of cross-correlations) influence the efficacy variability under pair-wise additive spike-timing dependent plasticity (STDP) and synaptic homeostasis (the mean strength of plastic synapses into a neuron is bounded), by implementing spike shuffling methods onto spike patterns self-organized by a network of excitatory and inhibitory leaky integrate-and-fire (LIF) neurons. With the increase of the decay time scale of the inhibitory synaptic currents, the LIF network undergoes a transition from asynchronous state to weak synchronous state and then to synchronous bursting state. We first shuffle these spike patterns using a variety of methods, each designed to evidently change a specific pattern statistics; and then investigate the change of efficacy variability of the synapses under STDP and synaptic homeostasis, when the neurons in the network fire according to the spike patterns before and after being treated by a shuffling method. In this way, we can understand how the change of pattern statistics may cause the change of efficacy variability. Our results are consistent with those of our previous study which implements spike-generating models on converging motifs. We also find that burstiness/regularity is important to determine the efficacy variability under asynchronous states, while heterogeneity of cross-correlations is the main factor to cause efficacy variability when the network moves into synchronous bursting states (the states observed in epilepsy). PMID:27555816

  2. Spike Pattern Structure Influences Synaptic Efficacy Variability Under STDP and Synaptic Homeostasis. II: Spike Shuffling Methods on LIF Networks

    Directory of Open Access Journals (Sweden)

    Zedong Bi

    2016-08-01

    Full Text Available Synapses may undergo variable changes during plasticity because of the variability of spike patterns such as temporal stochasticity and spatial randomness. Here, we call the variability of synaptic weight changes during plasticity to be efficacy variability. In this paper, we investigate how four aspects of spike pattern statistics (i.e., synchronous firing, burstiness/regularity, heterogeneity of rates and heterogeneity of cross-correlations influence the efficacy variability under pair-wise additive spike-timing dependent plasticity (STDP and synaptic homeostasis (the mean strength of plastic synapses into a neuron is bounded, by implementing spike shuffling methods onto spike patterns self-organized by a network of excitatory and inhibitory leaky integrate-and-fire (LIF neurons. With the increase of the decay time scale of the inhibitory synaptic currents, the LIF network undergoes a transition from asynchronous state to weak synchronous state and then to synchronous bursting state. We first shuffle these spike patterns using a variety of methods, each designed to evidently change a specific pattern statistics; and then investigate the change of efficacy variability of the synapses under STDP and synaptic homeostasis, when the neurons in the network fire according to the spike patterns before and after being treated by a shuffling method. In this way, we can understand how the change of pattern statistics may cause the change of efficacy variability. Our results are consistent with those of our previous study which implements spike-generating models on converging motifs. We also find that burstiness/regularity is important to determine the efficacy variability under asynchronous states, while heterogeneity of cross-correlations is the main factor to cause efficacy variability when the network moves into synchronous bursting states (the states observed in epilepsy.

  3. Spike Pattern Structure Influences Synaptic Efficacy Variability under STDP and Synaptic Homeostasis. II: Spike Shuffling Methods on LIF Networks

    OpenAIRE

    Bi, Zedong; Zhou, Changsong

    2016-01-01

    Synapses may undergo variable changes during plasticity because of the variability of spike patterns such as temporal stochasticity and spatial randomness. Here, we call the variability of synaptic weight changes during plasticity to be efficacy variability. In this paper, we investigate how four aspects of spike pattern statistics (i.e., synchronous firing, burstiness/regularity, heterogeneity of rates and heterogeneity of cross-correlations) influence the efficacy variability under pair-wis...

  4. Stress-Induced Impairment of a Working Memory Task: Role of Spiking Rate and Spiking History Predicted Discharge

    Science.gov (United States)

    Devilbiss, David M.; Jenison, Rick L.; Berridge, Craig W.

    2012-01-01

    Stress, pervasive in society, contributes to over half of all work place accidents a year and over time can contribute to a variety of psychiatric disorders including depression, schizophrenia, and post-traumatic stress disorder. Stress impairs higher cognitive processes, dependent on the prefrontal cortex (PFC) and that involve maintenance and integration of information over extended periods, including working memory and attention. Substantial evidence has demonstrated a relationship between patterns of PFC neuron spiking activity (action-potential discharge) and components of delayed-response tasks used to probe PFC-dependent cognitive function in rats and monkeys. During delay periods of these tasks, persistent spiking activity is posited to be essential for the maintenance of information for working memory and attention. However, the degree to which stress-induced impairment in PFC-dependent cognition involves changes in task-related spiking rates or the ability for PFC neurons to retain information over time remains unknown. In the current study, spiking activity was recorded from the medial PFC of rats performing a delayed-response task of working memory during acute noise stress (93 db). Spike history-predicted discharge (SHPD) for PFC neurons was quantified as a measure of the degree to which ongoing neuronal discharge can be predicted by past spiking activity and reflects the degree to which past information is retained by these neurons over time. We found that PFC neuron discharge is predicted by their past spiking patterns for nearly one second. Acute stress impaired SHPD, selectively during delay intervals of the task, and simultaneously impaired task performance. Despite the reduction in delay-related SHPD, stress increased delay-related spiking rates. These findings suggest that neural codes utilizing SHPD within PFC networks likely reflects an additional important neurophysiological mechanism for maintenance of past information over time. Stress

  5. Initial stages of calcium uptake and mineral deposition in sea urchin embryos.

    Science.gov (United States)

    Vidavsky, Netta; Addadi, Sefi; Mahamid, Julia; Shimoni, Eyal; Ben-Ezra, David; Shpigel, Muki; Weiner, Steve; Addadi, Lia

    2014-01-07

    Sea urchin larvae have an endoskeleton consisting of two calcitic spicules. We reconstructed various stages of the formation pathway of calcium carbonate from calcium ions in sea water to mineral deposition and integration into the forming spicules. Monitoring calcium uptake with the fluorescent dye calcein shows that calcium ions first penetrate the embryo and later are deposited intracellularly. Surprisingly, calcium carbonate deposits are distributed widely all over the embryo, including in the primary mesenchyme cells and in the surface epithelial cells. Using cryo-SEM, we show that the intracellular calcium carbonate deposits are contained in vesicles of diameter 0.5-1.5 μm. Using the newly developed airSEM, which allows direct correlation between fluorescence and energy dispersive spectroscopy, we confirmed the presence of solid calcium carbonate in the vesicles. This mineral phase appears as aggregates of 20-30-nm nanospheres, consistent with amorphous calcium carbonate. The aggregates finally are introduced into the spicule compartment, where they integrate into the growing spicule.

  6. Initial stages of calcium uptake and mineral deposition in sea urchin embryos

    Science.gov (United States)

    Vidavsky, Netta; Addadi, Sefi; Mahamid, Julia; Shimoni, Eyal; Ben-Ezra, David; Shpigel, Muki; Weiner, Steve; Addadi, Lia

    2014-01-01

    Sea urchin larvae have an endoskeleton consisting of two calcitic spicules. We reconstructed various stages of the formation pathway of calcium carbonate from calcium ions in sea water to mineral deposition and integration into the forming spicules. Monitoring calcium uptake with the fluorescent dye calcein shows that calcium ions first penetrate the embryo and later are deposited intracellularly. Surprisingly, calcium carbonate deposits are distributed widely all over the embryo, including in the primary mesenchyme cells and in the surface epithelial cells. Using cryo-SEM, we show that the intracellular calcium carbonate deposits are contained in vesicles of diameter 0.5–1.5 μm. Using the newly developed airSEM, which allows direct correlation between fluorescence and energy dispersive spectroscopy, we confirmed the presence of solid calcium carbonate in the vesicles. This mineral phase appears as aggregates of 20–30-nm nanospheres, consistent with amorphous calcium carbonate. The aggregates finally are introduced into the spicule compartment, where they integrate into the growing spicule. PMID:24344263

  7. Dopamine D4 receptor activation increases hippocampal gamma oscillations by enhancing synchronization of fast-spiking interneurons.

    Directory of Open Access Journals (Sweden)

    Richard Andersson

    Full Text Available BACKGROUND: Gamma oscillations are electric activity patterns of the mammalian brain hypothesized to serve attention, sensory perception, working memory and memory encoding. They are disrupted or altered in schizophrenic patients with associated cognitive deficits, which persist in spite of treatment with antipsychotics. Because cognitive symptoms are a core feature of schizophrenia it is relevant to explore signaling pathways that potentially regulate gamma oscillations. Dopamine has been reported to decrease gamma oscillation power via D1-like receptors. Based on the expression pattern of D4 receptors (D4R in hippocampus, and pharmacological effects of D4R ligands in animals, we hypothesize that they are in a position to regulate gamma oscillations as well. METHODOLOGY/PRINCIPAL FINDINGS: To address this hypothesis we use rat hippocampal slices and kainate-induced gamma oscillations. Local field potential recordings as well as intracellular recordings of pyramidal cells, fast-spiking and non-fast-spiking interneurons were carried out. We show that D4R activation with the selective ligand PD168077 increases gamma oscillation power, which can be blocked by the D4R-specific antagonist L745,870 as well as by the antipsychotic drug Clozapine. Pyramidal cells did not exhibit changes in excitatory or inhibitory synaptic current amplitudes, but inhibitory currents became more coherent with the oscillations after application of PD168077. Fast-spiking, but not non-fast spiking, interneurons, increase their action potential phase-coupling and coherence with regard to ongoing gamma oscillations in response to D4R activation. Among several possible mechanisms we found that the NMDA receptor antagonist AP5 also blocks the D4R mediated increase in gamma oscillation power. CONCLUSIONS/SIGNIFICANCE: We conclude that D4R activation affects fast-spiking interneuron synchronization and thereby increases gamma power by an NMDA receptor-dependent mechanism. This

  8. Joint Probability-Based Neuronal Spike Train Classification

    Directory of Open Access Journals (Sweden)

    Yan Chen

    2009-01-01

    Full Text Available Neuronal spike trains are used by the nervous system to encode and transmit information. Euclidean distance-based methods (EDBMs have been applied to quantify the similarity between temporally-discretized spike trains and model responses. In this study, using the same discretization procedure, we developed and applied a joint probability-based method (JPBM to classify individual spike trains of slowly adapting pulmonary stretch receptors (SARs. The activity of individual SARs was recorded in anaesthetized, paralysed adult male rabbits, which were artificially-ventilated at constant rate and one of three different volumes. Two-thirds of the responses to the 600 stimuli presented at each volume were used to construct three response models (one for each stimulus volume consisting of a series of time bins, each with spike probabilities. The remaining one-third of the responses where used as test responses to be classified into one of the three model responses. This was done by computing the joint probability of observing the same series of events (spikes or no spikes, dictated by the test response in a given model and determining which probability of the three was highest. The JPBM generally produced better classification accuracy than the EDBM, and both performed well above chance. Both methods were similarly affected by variations in discretization parameters, response epoch duration, and two different response alignment strategies. Increasing bin widths increased classification accuracy, which also improved with increased observation time, but primarily during periods of increasing lung inflation. Thus, the JPBM is a simple and effective method performing spike train classification.

  9. Blunted neuronal calcium response to hypoxia in naked mole-rat hippocampus.

    Directory of Open Access Journals (Sweden)

    Bethany L Peterson

    Full Text Available Naked mole-rats are highly social and strictly subterranean rodents that live in large communal colonies in sealed and chronically oxygen-depleted burrows. Brain slices from naked mole-rats show extreme tolerance to hypoxia compared to slices from other mammals, as indicated by maintenance of synaptic transmission under more hypoxic conditions and three fold longer latency to anoxic depolarization. A key factor in determining whether or not the cellular response to hypoxia is reversible or leads to cell death may be the elevation of intracellular calcium concentration. In the present study, we used fluorescent imaging techniques to measure relative intracellular calcium changes in CA1 pyramidal cells of hippocampal slices during hypoxia. We found that calcium accumulation during hypoxia was significantly and substantially attenuated in slices from naked mole-rats compared to slices from laboratory mice. This was the case for both neonatal (postnatal day 6 and older (postnatal day 20 age groups. Furthermore, while both species demonstrated more calcium accumulation at older ages, the older naked mole-rats showed a smaller calcium accumulation response than even the younger mice. A blunted intracellular calcium response to hypoxia may contribute to the extreme hypoxia tolerance of naked mole-rat neurons. The results are discussed in terms of a general hypothesis that a very prolonged or arrested developmental process may allow adult naked mole-rat brain to retain the hypoxia tolerance normally only seen in neonatal mammals.

  10. Blunted neuronal calcium response to hypoxia in naked mole-rat hippocampus.

    Science.gov (United States)

    Peterson, Bethany L; Larson, John; Buffenstein, Rochelle; Park, Thomas J; Fall, Christopher P

    2012-01-01

    Naked mole-rats are highly social and strictly subterranean rodents that live in large communal colonies in sealed and chronically oxygen-depleted burrows. Brain slices from naked mole-rats show extreme tolerance to hypoxia compared to slices from other mammals, as indicated by maintenance of synaptic transmission under more hypoxic conditions and three fold longer latency to anoxic depolarization. A key factor in determining whether or not the cellular response to hypoxia is reversible or leads to cell death may be the elevation of intracellular calcium concentration. In the present study, we used fluorescent imaging techniques to measure relative intracellular calcium changes in CA1 pyramidal cells of hippocampal slices during hypoxia. We found that calcium accumulation during hypoxia was significantly and substantially attenuated in slices from naked mole-rats compared to slices from laboratory mice. This was the case for both neonatal (postnatal day 6) and older (postnatal day 20) age groups. Furthermore, while both species demonstrated more calcium accumulation at older ages, the older naked mole-rats showed a smaller calcium accumulation response than even the younger mice. A blunted intracellular calcium response to hypoxia may contribute to the extreme hypoxia tolerance of naked mole-rat neurons. The results are discussed in terms of a general hypothesis that a very prolonged or arrested developmental process may allow adult naked mole-rat brain to retain the hypoxia tolerance normally only seen in neonatal mammals.

  11. Optogenetic monitoring identifies phosphatidylthreonine-regulated calcium homeostasis in Toxoplasma gondii

    Directory of Open Access Journals (Sweden)

    Arunakar Kuchipudi

    2016-05-01

    Full Text Available Toxoplasma gondii is an obligate intracellular parasite, which inflicts acute as well as chronic infections in a wide range of warm-blooded vertebrates. Our recent work has demonstrated the natural occurrence and autonomous synthesis of an exclusive lipid phosphatidylthreonine in T. gondii. Targeted gene disruption of phosphatidylthreonine synthase impairs the parasite virulence due to unforeseen attenuation of the consecutive events of motility, egress and invasion. However, the underlying basis of such an intriguing phenotype in the parasite mutant remains unknown. Using an optogenetic sensor (gene-encoded calcium indicator, GCaMP6s, we show that loss of phosphatidylthreonine depletes calcium stores in intracellular tachyzoites, which leads to dysregulation of calcium release into the cytosol during the egress phase of the mutant. Consistently, the parasite motility and egress phenotypes in the mutant can be entirely restored by ionophore-induced mobilization of calcium. Collectively, our results suggest a novel regulatory function of phosphatidylthreonine in calcium signaling of a prevalent parasitic protist. Moreover, our application of an optogenetic sensor to monitor subcellular calcium in a model intracellular pathogen exemplifies its wider utility to other entwined systems.

  12. Decreased intracellular [Ca2+ ] coincides with reduced expression of Dhprα1s, RyR1, and diaphragmatic dysfunction in a rat model of sepsis.

    Science.gov (United States)

    Wang, Meng-Meng; Hao, Li-Ying; Guo, Feng; Zhong, Bin; Zhong, Xiao-Mei; Yuan, Jing; Hao, Yi-Fei; Zhao, Shuang; Sun, Xue-Fei; Lei, Ming; Jiao, Guang-Yu

    2017-12-01

    Sepsis can cause decreased diaphragmatic contractility. Intracellular calcium as a second messenger is central to diaphragmatic contractility. However, changes in intracellular calcium concentration ([Ca 2+ ]) and the distribution and co-localization of relevant calcium channels [dihydropyridine receptors, (DHPRα1s) and ryanodine receptors (RyR1)] remain unclear during sepsis. In this study we investigated the effect of changed intracellular [Ca 2+ ] and expression and distribution of DHPRα1s and RyR1 on diaphragm function during sepsis. We measured diaphragm contractility and isolated diaphragm muscle cells in a rat model of sepsis. The distribution and co-localization of DHPRα1s and RyR1 were determined using immunohistochemistry and immunofluorescence, whereas intracellular [Ca 2+ ] was measured by confocal microscopy and fluorescence spectrophotometry. Septic rat diaphragm contractility, expression of DHPRα1s and RyR1, and intracellular [Ca 2+ ] were significantly decreased in the rat sepsis model compared with controls. Decreased intracellular [Ca 2+ ] coincides with diaphragmatic contractility and decreased expression of DHPRα1s and RyR1 in sepsis. Muscle Nerve 56: 1128-1136, 2017. © 2017 Wiley Periodicals, Inc.

  13. Calcium and phosphate effects on growth and alkaloid production in Coffea arabica: experimental results and mathematical model.

    Science.gov (United States)

    Bramble, J L; Graves, D J; Brodelius, P

    1991-04-15

    Plant, mammalian, and microbial cells are commonly immobilized in calcium alginate gels for the production of valuable secondary metabolites. However, calcium ions are known to inhibit growth in various types of cells, and calcium is an integral part of such gels. Therefore, an investigation was conducted to evaluate the effect of calcium on the growth and alkaloid production of a model cell-line, Coffea arabica, in suspension culture before, attempting to immobilize such cells in alginate. A kinetic model was then developed from the results to describe cell growth and alkaloid production and the mechanism by which calcium influences these variables. In addition, it was observed that there was a characteristic relationship between the concentration of calcium in the external medium and the concentration of extra cellular and intracellular phosphate. The intracellular phosphate level was, in turn, related to the production of alkaloids. Using these results, a dynamic mathematical model of cell growth and alkaloid production was developed based on the proposed roles of calcium and phosphate. The model showed satisfactory agreement with three sets of experiments at different calcium concentrations. A possible linkage between the calcium and phosphate results is postulated based on the limited solubility of calcium phosphate.

  14. T-type calcium channel: a privileged gate for calcium entry and control of adrenal steroidogenesis

    Directory of Open Access Journals (Sweden)

    Michel Florian Rossier

    2016-05-01

    Full Text Available Intracellular calcium plays a crucial role in modulating a variety of functions such as muscle contraction, hormone secretion, gene expression or cell growth. Calcium signaling has been however shown to be more complex than initially thought. Indeed, it is confined within cell microdomains and different calcium channels are associated with different functions, as shown by various channelopathies.Sporadic mutations on voltage-operated L-type calcium channels in adrenal glomerulosa cells have been shown recently to be the second most prevalent genetic abnormalities present in human aldosterone-producing adenoma. The observed modification of the threshold of activation of the mutated channels not only provides an explanation for this gain of function but reminds us on the importance of maintaining adequate electrophysiological characteristics to make channels able to exert specific cellular functions. Indeed, the contribution to steroid production of the various calcium channels expressed in adrenocortical cells is not equal and the reason has been investigated for a long time. Given the very negative resting potential of these cells, and the small membrane depolarization induced by their physiological agonists, low threshold T-type calcium channels are particularly well suited for responding under these conditions and conveying calcium into the cell, at the right place for controlling steroidogenesis. In contrast, high threshold L-type channels are normally activated by much stronger cell depolarizations. The fact that dihydropyridine calcium antagonists, specific for L-type channels, are poorly efficient for reducing aldosterone secretion either in vivo or in vitro, strongly supports the view that these two types of channels differently affect steroid biosynthesis.Whether a similar analysis is transposable to fasciculata cells and cortisol secretion is one of the questions addressed in the present review. No similar mutations on L-type or T

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

    Science.gov (United States)

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

    2014-02-28

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

  16. Benchmarking Spike-Based Visual Recognition: A Dataset and Evaluation

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    Liu, Qian; Pineda-García, Garibaldi; Stromatias, Evangelos; Serrano-Gotarredona, Teresa; Furber, Steve B.

    2016-01-01

    Today, increasing attention is being paid to research into spike-based neural computation both to gain a better understanding of the brain and to explore biologically-inspired computation. Within this field, the primate visual pathway and its hierarchical organization have been extensively studied. Spiking Neural Networks (SNNs), inspired by the understanding of observed biological structure and function, have been successfully applied to visual recognition and classification tasks. In addition, implementations on neuromorphic hardware have enabled large-scale networks to run in (or even faster than) real time, making spike-based neural vision processing accessible on mobile robots. Neuromorphic sensors such as silicon retinas are able to feed such mobile systems with real-time visual stimuli. A new set of vision benchmarks for spike-based neural processing are now needed to measure progress quantitatively within this rapidly advancing field. We propose that a large dataset of spike-based visual stimuli is needed to provide meaningful comparisons between different systems, and a corresponding evaluation methodology is also required to measure the performance of SNN models and their hardware implementations. In this paper we first propose an initial NE (Neuromorphic Engineering) dataset based on standard computer vision benchmarksand that uses digits from the MNIST database. This dataset is compatible with the state of current research on spike-based image recognition. The corresponding spike trains are produced using a range of techniques: rate-based Poisson spike generation, rank order encoding, and recorded output from a silicon retina with both flashing and oscillating input stimuli. In addition, a complementary evaluation methodology is presented to assess both model-level and hardware-level performance. Finally, we demonstrate the use of the dataset and the evaluation methodology using two SNN models to validate the performance of the models and their hardware

  17. Spike morphology in blast-wave-driven instability experiments

    International Nuclear Information System (INIS)

    Kuranz, C. C.; Drake, R. P.; Grosskopf, M. J.; Fryxell, B.; Budde, A.; Hansen, J. F.; Miles, A. R.; Plewa, T.; Hearn, N.; Knauer, J.

    2010-01-01

    The laboratory experiments described in the present paper observe the blast-wave-driven Rayleigh-Taylor instability with three-dimensional (3D) initial conditions. About 5 kJ of energy from the Omega laser creates conditions similar to those of the He-H interface during the explosion phase of a supernova. The experimental target is a 150 μm thick plastic disk followed by a low-density foam. The plastic piece has an embedded, 3D perturbation. The basic structure of the pattern is two orthogonal sine waves where each sine wave has an amplitude of 2.5 μm and a wavelength of 71 μm. In some experiments, an additional wavelength is added to explore the interaction of modes. In experiments with 3D initial conditions the spike morphology differs from what has been observed in other Rayleigh-Taylor experiments and simulations. Under certain conditions, experimental radiographs show some mass extending from the interface to the shock front. Current simulations show neither the spike morphology nor the spike penetration observed in the experiments. The amount of mass reaching the shock front is analyzed and potential causes for the spike morphology and the spikes reaching the shock are discussed. One such hypothesis is that these phenomena may be caused by magnetic pressure, generated by an azimuthal magnetic field produced by the plasma dynamics.

  18. A proteomic study of spike development inhibition in bread wheat.

    Science.gov (United States)

    Zheng, Yong-Sheng; Guo, Jun-Xian; Zhang, Jin-Peng; Gao, Ai-Nong; Yang, Xin-Ming; Li, Xiu-Quan; Liu, Wei-Hua; Li, Li-Hui

    2013-09-01

    Spike development in wheat is a complicated development process and determines the wheat propagation and survival. We report herein a proteomic study on the bread wheat mutant strain 5660M underlying spike development inhibition. A total of 121 differentially expressed proteins, which were involved in cold stress response, protein folding and assembly, cell-cycle regulation, scavenging of ROS, and the autonomous pathway were identified using MS/MS and database searching. We found that cold responsive proteins were highly expressed in the mutant in contrast to those expressed in the wild-type line. Particularly, the autonomous pathway protein FVE, which modulates flowering, was dramatically downregulated and closely related to the spike development inhibition phenotype of 5660M. A quantitative RT-PCR study demonstrated that the transcription of the FVE and other six genes in the autonomous pathway and downstream flowering regulators were all markedly downregulated. The results indicate that spike development of 5660M cannot complete the floral transition. FVE might play an important role in the spikes development of the wheat. Our results provide the theory basis for studying floral development and transition in the reproductive growth period, and further analysis of wheat yield formation. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. ViSAPy: A Python tool for biophysics-based generation of virtual spiking activity for evaluation of spike-sorting algorithms

    OpenAIRE

    Hagen, Espen; Ness, Torbjørn V.; Khosrowshahi, Amir; Sørensen, Christina; Fyhn, Marianne; Hafting, Torkel; Franke, Felix; Einevoll, Gaute T.

    2015-01-01

    Background: New, silicon-based multielectrodes comprising hundreds or more electrode contacts offer the possibility to record spike trains from thousands of neurons simultaneously. This potential cannot be realized unless accurate, reliable automated methods for spike sorting are developed, in turn requiring benchmarking data sets with known ground-truth spike times.New method: We here present a general simulation tool for computing benchmarking data for evaluation of spike-sorting algorithms...

  20. Calcium and Vitamin D

    Science.gov (United States)

    ... by supporting muscles needed to avoid falls. Children need vitamin D to build strong bones, and adults need ... be taken at one time. While your body needs vitamin D to absorb calcium, you do not need ...