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    Mitochondrial respiration and Ca2+ waves are linked during fertilization and meiosis completion (2005)
    Company of Biologists Limited
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © Company of Biologists Limited, 2003. This article is posted here by permission of Company of Biologists Limited for personal use, not for redistribution. The definitive version was published in Development 130 (2003): 683-692, doi:10.1242/10.1242/dev.00296.
    Description: Fertilization increases both cytosolic Ca2+ concentration and oxygen consumption in the egg but the relationship between these two phenomena remains largely obscure. We have measured mitochondrial oxygen consumption and the mitochondrial NADH concentration on single ascidian eggs and found that they increase in phase with each series of meiotic Ca2+ waves emitted by two pacemakers (PM1 and PM2). Oxygen consumption also increases in response to Ins(1,4,5)P3-induced Ca2+ transients. Using mitochondrial inhibitors we show that active mitochondria sequester cytosolic Ca2+ during sperm-triggered Ca2+ waves and that they are strictly necessary for triggering and sustaining the activity of the meiotic Ca2+ wave pacemaker PM2. Strikingly, the activity of the Ca2+ wave pacemaker PM2 can be restored or stimulated by flash photolysis of caged ATP. Taken together our observations provide the first evidence that, in addition to buffering cytosolic Ca2+, the egg's mitochondria are stimulated by Ins(1,4,5)P3-mediated Ca2+ signals. In turn, mitochondrial ATP production is required to sustain the activity of the meiotic Ca2+ wave pacemaker PM2.
    Description: This work was supported by AFM and ARC grants to C. S.
    Keywords: Fertilization ; Respiration ; Ca2+ waves ; Mitochondria ; Endoplasmic reticulum ; ATP ; Ca2+ wave pacemakers ; Ascidian
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
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    Electrokinetic measurements of membrane capacitance and conductance for pancreatic β-cells (2006)
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    Publication Date: 2022-05-26
    Description: Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of IEE for personal use, not for redistribution. The definitive version was published in IEE Proceedings - Nanobiotechnology 152 (2005): 189-193, doi:10.1049/ip-nbt:20050040.
    Description: Membrane capacitance and membrane conductance values are reported for insulin secreting cells (primary β-cells and INS-1 insulinoma cells) determined using the methods of dielectrophoresis and electrorotation. The membrane capacitance value of 12.57 (± 1.46) mF/m2 obtained for β-cells, and the values 9.96 (± 1.89) mF/m2 to 10.65 (± 2.1) mF/m2 obtained for INS-1 cells, fall within the range expected for mammalian cells. The electrorotation results for the INS-1 cells lead to a value of 36 (± 22) S/m2 for the membrane conductance associated with ion channels, if values in the range 2nS to 3 nS are assumed for the membrane surface conductance. This membrane conductance value falls within the range reported for INS cells obtained using the whole-cell patch-clamp technique. However, the total ‘effective’ membrane conductance value of 601 (± 182) S/m2 obtained for the INS-1 cells by dielectrophoresis is significantly larger (by a factor of around three-fold) than the values obtained by electrorotation. This could result from an increased membrane surface conductance, or increased passive conduction of ions through membrane pores, induced by the larger electric field stresses experienced by cells in the dielectrophoresis experiments.
    Description: This study was financed by a gift from the Denis Robinson Memorial Fund to RP and NIH grants NCRR RR001395 and DK06984 to PJSS.
    Keywords: Electrokinetic measurements ; Membrane capacitance ; Pancreatic beta-cells ; Membrane conductance ; Insulin secreting cells ; Insulinoma cells ; Dielectrophoresis ; Electrorotation ; Mammalian cells ; Ion channels ; Membrane surface conductance ; Whole-cell patch-clamp technique ; Passive conduction ; Membrane pores ; Electric field stresses ; Dielectrophoresis experiments
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: 233829 bytes
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