Hydrogen held by solids.  XII.  Hydroxyapatite catalysts

Bett, J.A.S.; Christner, L.; Hall, W. Keith

doi:10.1021/ja00998a003

Cited by 224 publications

(91 citation statements)

References 3 publications

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“…For non-stoichiometric HAp synthesised without NH 4 F (Figure 3a), a sudden weight loss between 880 o C and 931 o C occurs. This weight loss corresponds to 0.45% of the mass in an interval of temperature of only 50 o C and is due to the phase change nonstoichiometric HAp → α-TCP that is determined by the gradual loss of OH -and probably CO 2 from non-stoichiometric HAp and possible decomposition of the carbonates linked to the chain [66][67][68][69] . This same curve already occurs at 650 o C for HAp synthesised in presence of NH 4 F (Figure 3c), rising to 782 o C. The relative loss in weight (2.08%) is substantially larger than in the previous case.…”

Section: Resultsmentioning

confidence: 99%

Calcium phosphate biomaterials from marine algae. Hydrothermal synthesis and characterisation

Felício-Fernandes

Laranjeira

2000

Quím. Nova

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Recebido em 18/2/99; aceito em 27/1/00Calcium phosphate compounds such as Hydroxyapatite (HAp) were prepared by hydrothermal synthesis with phycogenic CaCO 3 as starting material. Material obtained was characterised by usual methods (XRD, FTIR, TG, N 2 -adsorption, SEM and EDX) in order to study its physical-chemical characteristics. The prepared HAp showed that it may be suitable for use as a biomaterial.

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Section: Resultsmentioning

confidence: 99%

Calcium phosphate biomaterials from marine algae. Hydrothermal synthesis and characterisation

Felício-Fernandes

Laranjeira

2000

Quím. Nova

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“…SAT was synthesized according to the procedure of Brown et al (18). BCP crystals were prepared by alkaline hydrolysis of brushite using a modification of the method of Bett et al (21). These crystals have a calcium/phosphate ratio of 1.59 and contained partially carbonate-substituted hydroxyapatite mixed with octacalcium phosphate by FTIR spectroscopy.…”

Section: Methodsmentioning

confidence: 99%

Phosphocitrate Inhibits a Basic Calcium Phosphate and Calcium Pyrophosphate Dihydrate Crystal-induced Mitogen-activated Protein Kinase Cascade Signal Transduction Pathway

Nair

Misra

Sallis

et al. 1997

Journal of Biological Chemistry

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Calcium deposition diseases caused by calcium pyrophosphate dihydrate (CPPD) and basic calcium phosphate (BCP) crystals are a significant source of morbidity in the elderly. We have shown previously that both types of crystals can induce mitogenesis, as well as metalloproteinase synthesis and secretion by fibroblasts and chondrocytes. These responses may promote degradation of articular tissues. We have also shown previously that both CPPD and BCP crystals activate expression of the c-fos and c-jun proto-oncogenes. Phosphocitrate (PC) can specifically block mitogenesis and proto-oncogene expression induced by either BCP or CPPD crystals in 3T3 cells and human fibroblasts, suggesting that PC may be an effective therapy for calcium deposition diseases. To understand how PC inhibits BCP and CPPD-mediated cellular effects, we have investigated the mechanism by which BCP and CPPD transduce signals to the nucleus. Here we demonstrate that BCP and CPPD crystals activate a protein kinase signal transduction pathway involving p42 and p44 mitogen-activated protein (MAP) kinases (ERK 2 and ERK 1). BCP and CPPD also cause phosphorylation of a nuclear transcription factor, cyclic AMP response element-binding protein (CREB), on serine 133, a residue essential for CREB's ability to transactivate. Treatment of cells with PC at concentrations of 10 ؊3 to 10 ؊5 M blocked both the activation of p42/p44 MAP kinases, and CREB serine 133 phosphorylation, in a dose-dependent fashion. At 10 ؊3 M, a PC analogue, n-sulfo-2-aminotricarballylate and citrate also modulate this signal transduction pathway. Inhibition by PC is specific for BCP-and CPPD-mediated signaling, since all three compounds had no effect on serum-induced p42/P44 or interleukin-1␤ induced p38 MAP kinase activities. Treatment of cells with an inhibitor of MEK1, an upstream activator of MAPKs, significantly inhibited crystal-induced cell proliferation, suggesting that the MAPK pathway is a significant mediator of crystal-induced signals.

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“…When both materials are subjected to outgassing temperatures above 500 "C, the librational band intensity rapidly decreases until final disappearance of the band above 600 "C. The band of the fluorided hydroxyapatite disappears at a slightly higher temperature, probably reflecting the increased stability brought about by fluoridation. It is not clear why the librational band disappears at a temperature well below 780 "C, the point of complete lattice collapse established by Bett et al (5) for calcium deficient hydroxyapatites. Our own data for the OH stretching mode, in agreement with the latter authors, also indicate considerable retention of OH species beyond 600 "C (Fig.…”

Section: Librational Hydroxyl Band Regionmentioning

confidence: 91%

“…conflicting views, two models involving ionic defects have been proposed without recourse to the presence of octacalcium phosphate, a phosphate of low calcium content (3)(4)(5). In support of these models, which may be represented by the formulae l,Calo -,(HP04)X(Po4)6 -,(OH), -, and 2, Cal 0 -x(HP04)x(P04)6 -.…”

Section: Introductionmentioning

confidence: 99%

The Fluoridation of Nonstoichiometric Calcium Hydroxyapatite. An Infrared Study

Amberg¹,

Luk²,

Wagstaff³

1974

Can. J. Chem.

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Calcium deficient hydroxyapatites were impregnated to varying degrees with fluoride in very dilute solutions of NaF at room temperature. Ca/P ratios were determined before and after fluoridation. Phosphate loss upon fluoridation was consistent with an initial mechanism of OH− vacancy filling by F−, with equivalent amounts of PO43− ions escaping to restore charge balance. Infrared measurements confirmed previous evidence of OH/F exchange and the formation of [Formula: see text] hydrogen bonds, which increased with progressive thermal activation, considerable exchange having occurred already at 120 °C and possibly below. The first signs of lattice collapse occurred near 600 °C, with the fluorided sample exhibiting somewhat better stability.

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Hydrogen held by solids. XII. Hydroxyapatite catalysts

Cited by 224 publications

References 3 publications

Calcium phosphate biomaterials from marine algae. Hydrothermal synthesis and characterisation

Calcium phosphate biomaterials from marine algae. Hydrothermal synthesis and characterisation

Phosphocitrate Inhibits a Basic Calcium Phosphate and Calcium Pyrophosphate Dihydrate Crystal-induced Mitogen-activated Protein Kinase Cascade Signal Transduction Pathway

The Fluoridation of Nonstoichiometric Calcium Hydroxyapatite. An Infrared Study

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