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Quantifying calcium fluxes underlying calcium puffs in Xenopus laevis oocytes

Bruno, Luciana, Solovey, Guillermo, Ventura, Alejandra C., Amici-Dargan, Sheila and Dawson, Silvina Ponce 2010. Quantifying calcium fluxes underlying calcium puffs in Xenopus laevis oocytes. Cell Calcium 47 (3) , pp. 273-286. 10.1016/j.ceca.2009.12.012

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We determine the calcium fluxes through inositol 1,4,5-trisphosphate receptor/channels underlying calcium puffs of Xenopus laevis oocytes using a simplified version of the algorithm of Ventura et al. [1]. An analysis of 130 puffs obtained with Fluo-4 indicates that Ca2+ release comes from a region of width ∼450 nm, that the release duration is peaked around 18 ms and that the underlying Ca2+ currents range between 0.12 and 0.95 pA. All these parameters are independent of IP3 concentration. We explore what distributions of channels that open during a puff, N p, and what relations between current and number of open channels, I (N p), are compatible with our findings and with the distribution of puff-to-trigger amplitude ratio reported in Rose et al. [2]. To this end, we use simple “mean field” models in which all channels open and close simultaneously. We find that the variability among clusters plays an important role in shaping the observed puff amplitude distribution and that a model for which I (N p) ∼ N p for small N p and I(Np)∼Np1/α (α > 1) for large Np, provides the best agreement. Simulations of more detailed models in which channels open and close stochastically show that this nonlinear behavior can be attributed to the limited time resolution of the observations and to the averaging procedure that is implicit in the mean-field models. These conclusions are also compatible with observations of ∼400 puffs obtained using the dye Oregon green.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Biosciences
Subjects: Q Science > Q Science (General)
Uncontrolled Keywords: Calcium fluxes; Puffs; Xenopus laevis; Confocal microscopy; IP3Rs; Backward methods.
Publisher: Elsevier
ISSN: 0143-4160
Last Modified: 04 Jun 2017 06:47

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