Influence Of Calcium Research Articles

Calcium Carbonate as a Potential Intervention to Prevent Labor Dystocia: Narrative Review of the Literature.

Anecdotally, there are attestations from clinicians of calcium carbonate being used successfully for laboring people experiencing labor dystocia. The goal of this narrative review was to provide a synopsis of pertinent literature on calcium use in obstetrics to explore the potential benefit of calcium carbonate as a simple and low-cost intervention for prevention or treatment of labor dystocia. To answer how calcium and carbonate physiologically contribute to myometrium contractility, we conducted a literature search of English-language peer-reviewed articles, with no year limitation, consisting of the keywords "calcium," "calcium carbonate," "calcium gluconate," "pregnancy," "hemorrhage," and variations of "smooth muscle contractility" and "uterine contractions." Though no overt evidence on calcium carbonate's ability to prevent labor dystocia was identified; relevant information was found regarding smooth muscle contractility, calcium's influence on uterine muscle contractility, and carbonate's potential impact on reducing amniotic fluid lactate levels to restore uterine contractility during labor. Studies reporting the potential effectiveness of calcium gluconate and sodium bicarbonate in preventing labor dystocia offer background, safety information, and rationale for a future randomized control trial to evaluate the ability of calcium carbonate to prevent labor dystocia and reduce rates of cesarean section.

Influence of calcium(II) and chloride on the oxidative reactivity of a manganese(II) complex of a cross-bridged cyclen ligand.

Available data from different laboratories have confirmed that both Ca(2+) and Cl(-) are crucial for water oxidation in Photosystem II. However, their roles are still elusive. Using a manganese(II) complex having a cross-bridged cyclen ligand as a model, the influence of Ca(2+) on the oxidative reactivity of the manganese(II) complex and its corresponding manganese(IV) analogue were investigated. It has been found that adding Ca(2+) can significantly improve the oxygenation efficiency of the manganese(II) complex in sulfide oxidation and further accelerate the oxidation of sulfoxide to sulfone. Similar improvements have also been observed for Mg(2+), Sr(2+), and Ba(2+). A new monomeric manganese(IV) complex having two cis-hydroxide ligands has also been isolated through oxidation of the corresponding manganese(II) complex with H2O2 in the presence of NH4PF6. This rare cis-dihydroxomanganese(IV) species has been well characterized by X-ray crystallography, electrochemistry, electron paramagnetic resonance, and UV-vis spectroscopy. Notably, using the manganese(IV) complex as a catalyst demonstrates higher activity than the corresponding manganese(II) complex, and adding Ca(2+) further improves its catalytic efficiency. However, adding Cl(-) decreases its catalytic activity. In electrochemical studies of manganese(IV) complexes with no chloride ligand present, adding Ca(2+) positively shifted the redox potential of the Mn(IV)/Mn(III) couple but negatively shifted its Mn(V)/Mn(IV) couple. In the manganese(II) complex having a chloride ligand, adding Ca(2+) shifted both the Mn(IV)/Mn(III) and Mn(V)/Mn(IV) couples in the negative direction. The revealed oxidative reactivity and redox properties of the manganese species affected by Ca(2+) and Cl(-) may provide new clues to understanding their roles in the water oxidation process of Photosystem II.

Application of microscopy to the investigation of brown coal pyrolysis

To examine the influence of calcium on the mechanisms of brown coal pyrolysis and gasification, the morphology of chars from raw and calcium-exchanged Yallourn brown coal was analysed. The chars were obtained by slow pyrolysis in a thermo gravimetric analyser and rapid pyrolysis in fluidized bed reactors operating at atmospheric pressure and at 1.1 MPa. They were examined by optical microscopy to determine reflectance and the percentage of particles that had become plastic during pyrolysis. In addition to confirming calcium's inhibiting effect on tar yield, the results from the rapid pyrolysis experiments show that in the presence of calcium, char reflectivity decreases, char H/C ratio increases, and the proportion of particles going through a plastic stage decreases. Calcium's inhibition of plasticity development is augmented by high pressure in the fluidized bed reactor. The effects appear to be attributable to the action of carboxylate calcium as a cross-linking agent, leading to the formation of a tighter char structure which traps the organic material that would otherwise be liberated as tar. The presence of Ca also increases the H/C ratio of the chars produced by slow pyrolysis, but the mechanism of pyrolysis differs, since in slow pyrolysis none of the particles showed evidence of plasticity. In slow pyrolysis, calcium's influence on char reflectivity depends on the holding temperature, since temperature determines the extents of both coal devolatilization and catalytic transformations. The roles of calcium in these processes and their influence on optical anisotropy and reflectance are discussed.

The calcium-binding site of clathrin light chains.

Clathrin light chains are calcium-binding proteins (Mooibroek, M. J., Michiel, D. F., and Wang, J. H. (1987) J. Biol. Chem. 262, 25-28) and clathrin assembly can be modulated by calcium in vitro. Thus, intracellular calcium may play a regulatory role in the function of clathrin-coated vesicles. The structural basis for calcium's influence on clathrin-mediated processes has been defined using recombinant deletion mutants and isolated fragments of the light chains. A single calcium-binding site, formed by residues 85-96, is present in both mammalian light chains (LCa and LCb) and in the single yeast light chain. This sequence has structural similarity to the calcium-binding EF-hand loops of calmodulin and related proteins. In mammalian light chains, the calcium-binding sequence is flanked by domains that regulate clathrin assembly and disassembly.

The kinetics of dehydroxylation and mullitization of zettlitz kaolin in the presence of calcium(II) as an ingredient

The method of differential thermal analysis and Kissinger's approach were used in this study to investigate the kinetics of dehydroxylation and mullitization. The relatively high resistance to the breaking of structural bonds and the diffusion to water molecules through the lamellar gas layer of water vapour limits the activation energy to 178 kJ mol −1, as determined in the experimental work. It is assumed that the relatively moderate activation energy value of mullitization, 487 kJ mol −1, obtained during the exothermic reaction is the result of a moderately defective structure and of the influence of calcium(II) which decreases the activation energy.