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At least 703 records · Page 39Linked to original sources
PubMed1983

Calcium-independent activation of calcium ion dependent cyclic nucleotide phosphodiesterase by synthetic compounds: quinazolinesulfonamide derivatives.

Quinazolinesulfonamides are synthetic compounds which calcium-independently stimulate Ca2+-dependent cyclic nucleotide phosphodiesterase. As this activation was observed with 2,4-dipiperidino-6-quinazolinesulfonamides but not with 4-piperidino-6-quinazolinesulfonamides, the activation seems to be dependent on the piperidine residue at the 2 and 4 position of the quinazoline ring, and the extent of hydrophobicity of each compound was thus enhanced. 2,4-Dipiperidino-6-quinazolinesulfonamide activates Ca2+-dependent phosphodiesterase in the absence of Ca2+-calmodulin (CaM). These quinazolinesulfonamides did not further enhance the activity of Ca2+-dependent phosphodiesterase activated by the Ca2+-CaM complex. These compounds are also potent inhibitors of cyclic AMP and GMP phosphodiesterases. CaM antagonists such as N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), its derivatives, and chlorpromazine and prenylamine inhibited selectively the quinazolinesulfonamide-induced activations of the phosphodiesterase. These quinazolinesulfonamides, in a high concentration, had only a slight stimulatory effect on myosin light chain kinase activity. All these findings suggest that the quinazolinesulfonamides are calcium-independent activators of Ca2+-dependent phosphodiesterase and they are proving to be useful tools for the study of CaM and phosphodiesterase, in vitro.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2005

Decarboxylation is a significant reaction pathway for photolabile calcium chelators and related compounds.

Photolysis of amino acids that bear a 2-nitrobenzyl protecting group on the amino nitrogen involves a normal 2-nitrobenzyl-type photocleavage to release the amino acid but also a second mechanistic pathway, that appears to be initiated by single electron transfer from the amino group to the excited state of the nitroaromatic. The end result of this pathway is photodecarboxylation. Quantitative experiments suggest that this latter pathway can contribute between 10 and 80% of the total reaction flux in different compounds. It appears that the aminium radical, the first product of the single electron transfer, can be intercepted by certain amino acids, resulting in a transfer of decarboxylation to this "sacrificial" amino acid. Possible implications for precise details of calcium release from photolabile derivatives of EDTA and EGTA are discussed.

Calcium↗
PubMed2005

Characterization and preliminary assessment of a sorbent produced by accelerated mineral carbonation.

This study shows that calcium silicate/aluminate-based materials can be carbonated to produce sorbents for metal removal. The material chosen for investigation, cement clinker, was accelerated carbonated, and its structural properties were investigated using X-ray diffraction (XRD), scanning electron microscopy, thermal gravimetric and differential thermal analysis, nuclear magnetic resonance spectroscopy, and nitrogen gas adsorption techniques. The principal carbonation reactions involved the transformation of dicalcium silicate, tricalcium silicate, and tricalcium aluminate into a Ca/Al-modified amorphous silica and calcium carbonate. It was found that carbonated cement had high acid buffering capacity, and maintained its structural integrity within a wide pH range. The uptake of Pb(II), Cd(II), Zn(II), Ni(II), Cr(II), Sr(II), Mo(VI), Cs(II), Co(II), and Cu(II) from concentrated (1000 mg L(-1)) single-metal solutions varied from 35 to 170 mg g(-1) of the carbonate cement. The removal of metals was hardly effected by the initial solution pH due to the buffering capability of the carbonated material. The kinetics of Pb, Cd, Cr, Sr, Cs, and Co removal followed a pseudo-second-order kinetic model, whereas the equilibrium batch data for Cu fitted the pseudo-first-order rate equation. PHREEQC simulation supported by XRD analysis suggested the formation of metal carbonates and silicates, calcium molybdate, and chromium (hydro)oxide. Cesium was likely to be adsorbed by Ca/Al-modified amorphous silica.

Adsorption↗
PubMed2006

Mineral trioxide aggregate pulpotomies: a case series outcomes assessment.

BACKGROUND: The greatest threats to developing teeth are dental caries and traumatic injury. A primary goal of all restorative treatment is to maintain pulp vitality so that normal root development or apexogenesis can occur. If pulpal exposure occurs, then a pulpotomy procedure aims to preserve pulp vitality to allow for normal root development. Historically, calcium hydroxide has been the material of choice for pulpotomy procedures. Recently, an alternative material called mineral trioxide aggregate (MTA) has demonstrated the ability to induce hard-tissue formation in pulpal tissue. The authors describe the clinical and radiographic outcome of a series of cases involving the use of MTA in pulpotomy procedures. METHODS: Twenty-three cases in 18 patients were treated with MTA pulpotomy procedures in an endodontic private practice. All of the patients had been referred to the practice for diagnosis and treatment of a symptomatic tooth. All of the authors provided treatment. Pulpal exposures were either due to caries or complicated enamel dentin fractures. RESULTS: Nineteen teeth in 14 patients were available for recall. The mean time of recall was 19.7 months. Of the 19 cases, 15 involved healed teeth, and three involved teeth that were healing. One of 19 cases involved a tooth with persistent disease. CONCLUSIONS: MTA may be useful as a substitute for calcium hydroxide in pulpotomy procedures. Further research, however, is required to clarify this conclusion. CLINICAL IMPLICATIONS: MTA conceivably could replace calcium hydroxide as the material of choice for pulpotomy procedures, if future research continues to show promising results.

Adolescent↗
PubMed2005

Integral water treatment plant modeling: improvements for particle processes.

An update of research on particle behavior in water treatment plants first performed 25 years ago under the direction of Charles O'Melia is provided. The earlier work involved mathematical modeling of the changes in particle size distributions in the flocculation and sedimentation processes in water treatment plants. The current model includes corrections for short-range interactions between particles as they approach one another. These corrections severely reduce the expected collision frequency between particles that are very different in size and, therefore, substantially change the model predictions. Both experimental and field measurements of particle size distributions are provided; such measurements were unavailable in the earlier work and represent a touchstone to reality for the modeling efforts. The short-range model successfully fits experimental results for flocculation when the mechanism of particle destabilization is charge neutralization. However, the model does not account for the creation of new solids by precipitation either when hydrolyzing salts of aluminum or iron are added for particle destabilization by "sweep floc" destabilization or lime is added to remove calcium and magnesium as calcium carbonate and magnesium hydroxide in softening. The flocculent sedimentation model yields results that are in strong qualitative agreement with typical field measurements.

Aluminum Compounds↗
PubMed2001

Role of barium nitrate on the sulfur fixation of calcium oxide.

In this paper, the effect of Ba(NO3)2 on the efficiency of sulfur fixation of calcium oxide during coal combustion was studied. The results showed that addition of barium nitrate to the CaO can enhance the sulfur removal rate of CaO significantly. The X-ray diffraction spectrum of residual ash of coal added some sulfur fixative expressed that Ba2+ can form a compound of Ba-Al-Si-O which encloses the CaSO4 to prevent it's decomposition, so Ba2+ can improve the action of sulfur fixation of CaO. The combustion character of the original coal and original coal added sulfur fixative was researched with thermal-gravity analyzer and the results expressed that adding some sulfur fixative to the coal will make the combustion character of coal change little.

Air Pollutants↗
PubMed1989

The role of membrane bound sialic acid of rat mast cells in histamine release induced by compound 48/80 and derivatives as well as calcium.

Histamine release induced by compound 48/80 from rat mast cells is not dependent on extracellular Ca2+. Preincubation of mast cells with trypsin has only little effects on histamine release induced by this polycation. This work also demonstrates that histamine release induced by compound 48/80 and its analogues in the absence of extracellular Ca2+ depends on membrane bound sialic acid of the mast cell. Neuraminidase treatment of the cells in the presence of extracellular Ca2+ leads to histamine liberation. These findings suggest that sialic acid residues of the mast cell membrane constitute the site at which polycations exert their stimulatory actions of histamine liberation.

Animals↗
PubMed1992

Effects of photolabile calcium chelators on fluorescent calcium indicators.

The fluorescence properties of the calcium indicators Fura-2 and Fluo-3 have been investigated in the presence of the 'caged calcium' photolabile chelators Nitr-5 and DM-nitrophen. The excitation spectra of dilute solutions of these indicators was distorted by the presence of photolabile chelators, owing to differential absorbance of excitation light by the chelators, as well as calcium-dependent fluorescence of the chelators themselves. This distortion was altered on partial photolysis of the chelators, due to changes in their absorbance and fluorescence. At high concentrations of indicators (100 microM) and photolabile chelators (10 mM), similar to those used experimentally, DM-nitrophen quenched the fluorescence of Fluo-3 at low calcium concentrations. The results suggest that Fura-2 may be used with either chelator, and Fluo-3 with Nitr-5, to measure calcium released on photolysis of the caged compounds, but that careful calibration of the chelator-indicator mixture after the appropriate degree of photolysis is necessary.

Acetates↗