calcium   584

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Carbonated (Sparkling) Water: Good or Bad?
In a controlled study in 18 postmenopausal women, drinking 34 ounces (1 liter) of sodium-rich sparkling water daily for 8 weeks led to better calcium retention than drinking plain mineral water (18Trusted Source).
pregnancy  calcium 
17 hours ago by brittanydael
Ca2+ ionophore A23187 can make mouse spermatozoa capable of fertilizing in vitro without activation of cAMP-dependent phosphorylation pathways | PNAS
Ca2+ ionophore A23187 is known to induce the acrosome reaction of mammalian spermatozoa, but it also quickly immobilizes them. Although mouse spermatozoa were immobilized by this ionophore, they initiated vigorous motility (hyperactivation) soon after this reagent was washed away by centrifugation. About half of live spermatozoa were acrosome-reacted at the end of 10 min of ionophore treatment; fertilization of cumulus-intact oocytes began as soon as spermatozoa recovered their motility and before the increase in protein tyrosine phosphorylation, which started 30–45 min after washing out the ionophore. When spermatozoa were treated with A23187, more than 95% of oocytes were fertilized in the constant presence of the protein kinase A inhibitor, H89. Ionophore-treated spermatozoa also fertilized 80% of oocytes, even in the absence of HCO3−, a component essential for cAMP synthesis under normal in vitro conditions. Under these conditions, fertilized oocytes developed into normal offspring. These data indicate that mouse spermatozoa treated with ionophore are able to fertilize without activation of the cAMP/PKA signaling pathway. Furthermore, they suggest that the cAMP/PKA pathway is upstream of an intracellular Ca2+ increase required for the acrosome reaction and hyperactivation of spermatozoa under normal in vitro conditions.
acrosome  sperm  calcium  a23187 
8 weeks ago by Segalllab
Two distinct actin filament populations have effects on mitochondria, with differences in stimuli and assembly factors | Journal of Cell Science
Recent studies show that mitochondria and actin filaments work together in two contexts: (1) increased cytoplasmic calcium induces cytoplasmic actin polymerization that stimulates mitochondrial fission and (2) mitochondrial depolarization causes actin assembly around mitochondria, with roles in mitophagy. It is unclear whether these two processes utilize similar actin assembly mechanisms. Here, we show that these are distinct actin assembly mechanisms in the acute phase after treatment (<10 min). Calcium-induced actin assembly is INF2 dependent and Arp2/3 complex independent, whereas depolarization-induced actin assembly is Arp2/3 complex dependent and INF2 independent. The two types of actin polymerization are morphologically distinct, with calcium-induced filaments throughout the cytosol and depolarization-induced filaments as ‘clouds’ around depolarized mitochondria. We have previously shown that calcium-induced actin stimulates increases in both mitochondrial calcium and recruitment of the dynamin GTPase Drp1 (also known as DNM1L). In contrast, depolarization-induced actin is temporally associated with extensive mitochondrial dynamics that do not result in mitochondrial fission, but in circularization of the inner mitochondrial membrane (IMM). These dynamics are dependent on the protease OMA1 and independent of Drp1. Actin cloud inhibition causes increased IMM circularization, suggesting that actin clouds limit these dynamics
calcium  mitochondria  actin_polymerization 
9 weeks ago by Segalllab
Dual Sensing of Physiologic pH and Calcium by EFCAB9 Regulates Sperm Motility - ScienceDirect
Notes stiffer waveform - fertility defect not as strong as KIF9.

Varying pH of luminal fluid along the female reproductive tract is a physiological cue that modulates sperm motility. CatSper is a sperm-specific, pH-sensitive calcium channel essential for hyperactivated motility and male fertility. Multi-subunit CatSper channel complexes organize linear Ca2+ signaling nanodomains along the sperm tail. Here, we identify EF-hand calcium-binding domain-containing protein 9 (EFCAB9) as a bifunctional, cytoplasmic machine modulating the channel activity and the domain organization of CatSper. Knockout mice studies demonstrate that EFCAB9, in complex with the CatSper subunit, CATSPERζ, is essential for pH-dependent and Ca2+-sensitive activation of the CatSper channel. In the absence of EFCAB9, sperm motility and fertility is compromised, and the linear arrangement of the Ca2+ signaling domains is disrupted. EFCAB9 interacts directly with CATSPERζ in a Ca2+-dependent manner and dissociates at elevated pH. These observations suggest that EFCAB9 is a long-sought, intracellular, pH-dependent Ca2+ sensor that triggers changes in sperm motility.
sperm_motility  calcium  pH 
august 2019 by Segalllab
Shear stress-induced nuclear shrinkage through activation of Piezo1 channels in epithelial cells | Journal of Cell Science
The cell nucleus responds to mechanical cues with changes in size, morphology and motility. Previous work has shown that external forces couple to nuclei through the cytoskeleton network, but we show here that changes in nuclear shape can be driven solely by calcium levels. Fluid shear stress applied to MDCK cells caused the nuclei to shrink through a Ca2+-dependent signaling pathway. Inhibiting mechanosensitive Piezo1 channels through treatment with GsMTx4 prevented nuclear shrinkage. Piezo1 knockdown also significantly reduced the nuclear shrinkage. Activation of Piezo1 with the agonist Yoda1 caused similar nucleus shrinkage in cells not exposed to shear stress. These results demonstrate that the Piezo1 channel is a key element for transmitting shear force input to nuclei. To ascertain the relative contribution of Ca2+ to cytoskeleton perturbation, we examined F-actin reorganization under shear stress and static conditions, and showed that reorganization of the cytoskeleton is not necessary for nuclear shrinkage. These results emphasize the role of the mechanosensitive channels as primary transducers in force transmission to the nucleus.
shear_stress  piezo1  calcium  nucleus 
july 2019 by Segalllab
Actin Remodeling in Regulated Exocytosis: Toward a Mesoscopic View - ScienceDirect
In several types of cells, the cortical F-actin meshwork is dynamically remodeled following stimuli that elevate the cytosolic Ca2+ concentration 8, 41, 42, 43. Early studies using neurosecretory cells showed that high cytosolic Ca2+ levels activate the actin-filament-severing protein scinderin, which disassembles the cortical actin network to allow secretory vesicles to reach the plasma membrane 41, 42. In antigen-triggered granule exocytosis of mast cells, a model of antigen-triggered mast cell activation and allergic responses [44], the depolymerization of the cortical actin due to the addition of latrunculin affects secretion in a biphasic manner. Although latrunculin causes a small increase in total secretion, the initial rate of exocytosis is actually reduced [8], suggesting that the cortical actin acts both to facilitate and hinder secretion. Single-cell secretion measurements using fluorescence de-quenching of previously endocytosed dextran–fluorescein isothiocyanate showed that activation of the FcεRI receptor results in cell-wide calcium oscillations and exocytosis events that occur at peak calcium in each cycle 8, 9. Further experimental and computational analyses have suggested that vesicle fusion correlates with the observed actin and Ca2+ oscillations 8, 9. A vesicle secretion cycle starts with the capture of vesicles by actin when cortical F-actin is high, followed by vesicle translocation through the cortex when F-actin levels are low, culminating in vesicle fusion with the plasma membrane when the Ca2+ level subsequently increases. In addition, it has also been reported that Ca2+ oscillations are coupled to the antigen-stimulated oscillation of phosphatidylinositol-4,5-biphosphate [PtdIns(4,5)P2], which is involved in exocytosis [45]. Thus, cells use oscillating levels of Ca2+, PtdIns(4,5)P2 and cortical F-actin to orchestrate the sequential stages of secretion (Figure 1).
calcium  ACTIN  oscillations 
june 2019 by Segalllab
The role of calcium in pancreatic secretion and disease.
Hypercalcemia stimulates enzyme secretion in the pancreas, hypocalcemia inhibits it.
calcium  pancreas  pancreatitis  bicarbonate 
june 2019 by cessationoftime

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