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PubMed2006

Interactions of pigments and opacifiers on color stability of MDX4-4210/type A maxillofacial elastomers subjected to artificial aging.

STATEMENT OF PROBLEM: The color instability and degradation of maxillofacial elastomers limit the function and cosmetic quality of facial prostheses. PURPOSE: The purpose of this study was to measure the interactions of oil pigments plus dry earth opacifiers at 5%, 10%, and 15% by volume in stabilizing the color of MDX4-4210/type A silicone elastomers before and after artificial aging. MATERIAL AND METHODS: In the first part of the study, each of 5 opacifiers (Georgia kaolin powder neutral, kaolin powder calcined, Artskin white, dry pigment titanium (Ti) white, or Ti white artists' oil color) at 10% concentrations were combined with each of 5 oil pigment types (no pigment, cadmium-barium red deep, yellow ochre, burnt sienna, or a mixture of the 3 pigments), for a total of 25 experimental groups of elastomers. In the second part of the study, 50 experimental groups of elastomers were made by combining 1 of 5 opacifiers at 5% and 15% concentrations with 1 of 5 oil pigments as in Part 1. Five specimens of each elastomer were tested, for a total of 375 specimens. In each part of the study, all specimens were aged in an artificial aging chamber. CIE L*a*b* values were measured by a spectrophotometer. The color differences (DeltaE*) were subjected to repeated-measures analysis of variance. Mean values were compared by Tukey-Kramer intervals (alpha = .05). RESULTS: In Part 1, when the opacifiers were tested at 10% concentration, Ti white oil color had the most color change, and dry pigment Ti white had the least; all other opacifiers were not significantly different from each other. In Part 2, at 5%, Ti white oil color had the most color change; all other opacifiers were not significantly different from the others. At 15%, Ti white oil color again had the most color change, followed by Artskin white, kaolin powder calcined, and Georgia kaolin; Ti white dry earth pigment had the least color change. Overall, 5% Artskin white had less color change than the 15%, whereas 15% dry pigment Ti white had less color change than the 5% (P < .001). The 5% and 15% of other opacifiers were not significantly different. CONCLUSIONS: At all 3 concentrations, oil pigments mixed with opacifiers helped protect the MDX4-4210/type A silicone elastomer from color degradation over time. Dry pigment Ti white remained the most color stable over time, followed by the pigments mixed with kaolin powder calcined, Georgia kaolin, Artskin white, and Ti white artists' oil color.

Barium Sulfate↗
PubMed1998

Comparative radical scavenging ability of bidentate iron (III) chelators.

Iron chelators can reduce radical damage inflicted on cells by two mechanisms, either direct scavenging of the radicals or by scavenging loosely bound iron which under aerobic conditions can generate radicals. Frequently it is not possible to distinguish between these two modes of action. 3-Hydroxypyridin-4-ones, in contrast to many iron(III) chelators are poor radical scavengers and therefore have potential in analysing mechanisms involved in biochemical and physiological processes which are centered on radical-induced cell injury.

Bepridil↗
PubMed1999

Phosphate-binding capacity of ferrihydrite versus calcium acetate in rats.

Calcium salts, such as calcium carbonate and calcium acetate, are the principal compounds used as phosphate binders in patients with chronic renal failure. The dose required is three to six times the normal requirement for calcium. Use of these large doses of calcium salts in the diet can result in hypercalcemia. Other compounds have been investigated as phosphate binders with varying degrees of success. Synthetic ferrihydrite (5Fe(2)O(3).9H(2)O) has a high adsorptive capacity for phosphate and may be an effective phosphate binder. The phosphate-binding capacity of ferrihydrite was compared with that of calcium acetate in 250-g male Sprague Dawley rats. After an overnight fast, rats (n = 5 per group) were gavaged with an American Institute of Nutrition (AIN) 76 formula containing one third the daily phosphorus intake labeled with phosphorus-32 ((32)P). Either two levels of calcium acetate, representing three (1/2X) or six (1X) times the usual calcium intake for one third of the day, or equivalent amounts of ferrihydrite were added to the diet. An additional group received two times (2X) the larger dose, and a sixth control group received no binder in the diet. Phosphorus absorption curves were determined from (32)P appearance in the serum. The 1/2X dose of ferrihydrite reduced (32)P by approximately one half, and the 2X dose nearly completely suppressed (32)P absorption, similar to the 1X dose of calcium acetate. The advantage of using a ferrihydrite binder would be to avoid the hypercalcemia resulting from the use of high-dose calcium salts. An added advantage may result from the small amounts of iron absorbed in these chronically iron-deficient patients.

Absorption↗
PubMed2005

Chemical differences between white and gray mineral trioxide aggregate.

The purpose of this research was to determine and compare the composition of white mineral trioxide aggregate and gray mineral trioxide aggregate. Electron probe microanalysis results indicated that lime (CaO), silica (SiO2), and bismuth oxide (Bi2O3) were the dominant compounds in each case and were present at comparable levels in either of the types of mineral trioxide aggregate analyzed. It was concluded that the most significant differences observed were between the measured concentrations of Al2O3 (+122%), MgO (+130%), and especially FeO (+1000%) when gray mineral trioxide aggregate was compared with white mineral trioxide aggregate.

Aluminum Compounds↗
PubMed2005

Supercritical fluid technology of nanoparticle coating for new ceramic materials.

This work highlights, for the first time, the coating of ferroelectric nanoparticles with a chemical fluid deposition process in supercritical fluids. BaTiO3 nanoparticles of about 50 nm are coated with a shell of a few nanometers of amorphous alumina and can be recovered as a dry powder for processing. The sintering of these core-shell nanoparticles gives access to a ceramic material with very interesting ferroelectric properties, in particular, dielectric losses below 1%.

Adsorption↗
PubMedDate not supplied

Comparison on reactivity of Fe(III) and Al(III) compounds in the presence of hydrogen peroxide: its relevance to possible origin for central nervous system toxicity by aluminum ion.

The iron(III) compounds with several aminocarboxylate chelates containing an aryl or furan substituent exhibit high activity in enhancement of the reactivity of hydrogen peroxide, leading to facile hydroxylation at benzene ring, and to degradation of furan ring, but no such activity was observed for the corresponding Al(III) compounds. These results were interpreted in terms of the molecular orbital consideration, and lack of the activity of the Al(III) complexes was attributed to lack of electrophilic nature of the peroxide adduct due to the absence of a d-orbital; this may explain the fact that there were no tumors in Al-NTA(nitrilotriacetic acid)-treated rats. Based on the facts observed in this study, the decreased function of iron(III) ions for synthesizing neurotransmitters in the brain was assumed to be one of the possible origin for the neurotoxicity by injection of the Al(III) salts in vivo.

Aluminum↗
PubMed2006

Characterization of phosphorus species in biosolids and manures using XANES spectroscopy.

Identification of the chemical P species in biosolids or manures will improve our understanding of the long-term potential for P loss when these materials are land applied. The objectives of this study were to determine the P species in dairy manures, poultry litters, and biosolids using X-ray absorption near-edge structure (XANES) spectroscopy and to determine if chemical fractionation techniques can provide useful information when interpreted based on the results of more definitive P speciation studies. Our XANES fitting results indicated that the predominant forms of P in organic P sources included hydroxylapatite, PO(4) sorbed to Al hydroxides, and phytic acid in lime-stabilized biosolids and manures; hydroxylapatite, PO(4) sorbed on ferrihydrite, and phytic acid in lime- and Fe-treated biosolids; and PO(4) sorbed on ferrihydrite, hydroxylapatite, beta-tricalcium phosphate (beta-TCP), and often PO(4) sorbed to Al hydroxides in Fe-treated and digested biosolids. Strong relationships existed between the proportions of XANES PO(4) sorbed to Al hydroxides and NH(4)Cl- + NH(4)F-extractable P, XANES PO(4) sorbed to ferrihydrite + phytic acid and NaOH-extractable P, and XANES hydroxylapatite + beta-TCP and dithionite-citrate-bicarbonate (DCB)- + H(2)SO(4)-extractable P (r(2) = 0.67 [P = 0.01], 0.78 [P = 0.01], and 0.89 [P = 0.001], respectively). Our XANES fitting results can be used to make predictions about long-term solubility of P when biosolids and manures are land applied. Fractionation techniques indicate that there are differences in the forms of P in these materials but should be interpreted based on P speciation data obtained using more advanced analytical tools.

Absorption↗
PubMed1984

Simultaneous demonstration of connective tissue elastica and fibrin by a combined Verhoeff's elastic-Martius-scarlet-blue trichrome stain.

A method for the routine combined demonstration of elastica, connective tissue in general, and fibrin is described. Elastica, stained blue-black by Verhoeff's iron hematoxylin, is contrasted with muscle and collagen, stained red and blue or green respectively, by a modification of the Martius-scarlet-blue (MSB) trichrome for fibrin of Lendrum et al. The MSB technique selectively stains fresh, mature and old fibrin orange-yellow, red and blue respectively; the Masson trichrome does not distinguish between erythrocytes and fibrin. Nuclei are stained at the same time as the elastica. The technique takes approximately one and a half hours and is ideal for the study of connective tissue and vascular pathology, especially the necrotizing vasculitides.

Azo Compounds↗
PubMed1980

Biosynthesis of bicyclomycin. II. Biosynthetic conditions and incorporation of radioactive precursors into bicyclomycin by washed mycelium.

The biosynthesis of bicyclomycin by Streptomyces sapporonensis was studied using suspensions of washed mycelium. Nicotinamide and Fe2+ were found to be essential cofactors in the biosynthesis. Production of bicyclomycin was enhanced most effectively in the presence of equal moles of L-leucine and L-isoleucine, which in experiments with radioactively labeled compounds were found to be incorporated into bicyclomycin at equivalent rates. These facts strongly suggest that bicyclomycin biosynthesis involves coupling of equal moles of these two amino acids.

Amino Acids↗
PubMedDate not supplied

[Complexes of DNA with trivalent metal ions in presence of manganese ions].

The interaction of DNA with Fe3+, Al3+, Co(NH3)6(3+) in a solution containing MnCl2 was studied. It was shown that there exists a competition for the binding sites between Mn2+ and Al3+, while the binding of Mn2+ to DNA does not depend on the presence of Fe3+ and Co(NH3)6(3+) in solution. We proposed that Fe3+ and Co(NH3)6(3+) ions prefer to bind to phosphates, and Al3+ ions are capable to bind to the nitrogen bases of DNA.

Aluminum Compounds↗
PubMed1991

Inhibition of mineralization of glutaraldehyde-pretreated bovine pericardium by AlCl3. Mechanisms and comparisons with FeCl3, LaCl3, and Ga(NO3)3 in rat subdermal model studies.

In the present study, the authors investigated the mechanism by which Al3+ preincubations inhibited the pathologic calcification of glutaraldehyde-pretreated bovine pericardium (GPBP) implanted subdermally in rats. The concentration dependency of the Al3+ anticalcification effect was compared with that of other trivalent metal ions (Fe3+, Ga3+, La3+) known to interact with calcium phosphates. In vitro incubations of GPBP were carried out in AlCl3 (10(-3) mol/l [molar] to 10(-1) mol/l) to ascertain both the optimal conditions for uptake of Al3+ and the time course of Al3+ dissociation. Al3+ uptake by GPBP was concentration dependent and occurred rapidly, with tissue levels after 1 hour not differing significantly from those after 72 hours of incubation. Analyses of GPBP samples preincubated in AlCl3 (0.1 mol/l, 24 hours) showed that more than 75% of the Al3+ remained tightly bound after 60 days' in vitro release at 37 degrees C, pH 7.4. Preincubations of GPBP in AlCl3 significantly inhibited calcification after subdermal implantation in rats for 60 days (Ca++ = 5.1 +/- 0.9 microgram/mg, 11.5 +/- 4.6 micrograms/mg, 70.3 +/- 23.0 micrograms/mg, mean +/- standard error [SE], for 10(-1) mol/l, 10(-2) mol/l, 10(-3) mol/l AlCl3, respectively), compared with controls (Ca++ = 110.0 +/- 9.3 micrograms/mg). All animals were free of Al3(+)-mediated adverse effects on bone, as determined by light microscopic evaluation of femoral epiphyseal growth plates. Transmission electron microscopy coupled with electron energy loss spectroscopy (EELS) of GPBP incubated in 10(-1) mol l AlCl3 for 24 hours demonstrated discrete Al3+ localization in the sarcolemma and cytoplasmic and nuclear membranes of devitalized pericardial connective tissue cells at intracellular sites coincident with phosphorus loci. Similar intracellular localization remained prominent in explants removed after 60 days; no calcific deposits were noted in these specimens. Preincubations in Fe3+ but not Ga3+ and La3+ solutions yielded significant inhibition of GPBP calcification, which did not differ significantly from that provided by Al3- and had a comparable concentration dependency. Light microscopic examination (Prussian blue staining) and EELS of FeCl3-preincubated explants demonstrated Fe3+ localization within devitalized GPBP connective tissue cells. The authors conclude that Al3+ and Fe3+ significantly inhibit the pathologic mineralization of glutaraldehyde-pretreated bovine pericardium by mechanisms that are likely related to the high affinity of these cations for membrane associated and other intracellular phosphorus loci.

Aluminum↗
PubMed2006

Magnetic and structural study of the state of iron in the oral haematinic ferrimannitol ovoalbumin.

From magnetic and structural analyses performed on ferrimannitol ovalbumin, iron in this drug is observed to be present as two-line ferrihydrite nanoparticles, of around 4 nm in diameter, which are superparamagnetic above approximately 20 K. Among other parameters, the temperature dependence of the magnetic out-of-phase susceptibility of this compound has been fully characterised and yields results clearly different from that of ferritin. This characterisation, performed for the first time for an oral haematinic, is of interest in the context of future pharmacological studies of this compound.

Ferric Compounds↗
PubMed1993

Review of the pH of hemostatic agents used in tissue displacement.

Newer hemostatic agents such as the tetrahydrozolines and oxymetazolines have a more acceptable pH and should be kinder to tooth structure and soft tissue than the conventional solutions. Although additional study is needed, it would seem prudent to be cautious in using low pH hemostatic agents and avoid the exposure to sensitive intraoral tissues-particularly delicate tissues--or tooth preparation close to the dental pulp.

Alum Compounds↗
PubMed2005

Examination of the jarosite-alunite precipitate addition in the raw meal for the production of sulfoaluminate cement clinker.

The aim of the present research work was to investigate the possibility of adding a jarosite-alunite chemical precipitate, a waste product of a new hydrometallurgical process developed to treat economically low-grade nickel oxides ores, in the raw meal for the production of sulfoaluminate cement clinker. For that reason, two samples of raw meals were prepared, one contained 20% gypsum, as a reference sample ((SAC)Ref) and another with 11.31% jarosite-alunite precipitate ((SAC)J/A). Both raw meals were sintered at 1300 degrees C. The results of chemical and mineralogical analyses as well as the microscopic examination showed that the use of the jarosite-alunite precipitate did not affect the mineralogical characteristics of the so produced sulfoaluminate cement clinker and there was confirmed the formation of the sulfoaluminate phase (C4A3S), the most typical phase of this cement type. Furthermore, both clinkers were tested by determining the grindability, setting time, compressive strength and expansibility. The hydration products were examined by XRD analysis at 2, 7, 28 and 90 days. The results of the physico-mechanical tests showed that the addition of jarosite-alunite precipitate did not negatively affect the quality of the produced cement.

Aluminum Compounds↗
PubMed2000

Phosphate immobilization using an acidic type F fly ash.

Batch equilibration experiments using a low calcium ( approximately 1 wt.% as CaO), acidic (pH approximately 4.5) Type F fly ash demonstrated phosphate immobilization on the order of 100% to 75% for 50 and 100 mg P/l solutions, respectively. A loosely compacted column of fly ash similarly removed 10 mg P/l for over 85 pore volumes. While the interactions between phosphate and calcium-rich (Type C) ashes are relatively well understood, insight into the mechanisms of phosphate immobilization in Type F ash necessitated a review of the phosphate chemistry and interactions with acidic geomedia. Phosphate adsorption was subsequently modeled using a constant capacitance model approach (CCM) excluding precipitation reactions. Our CCM predictions of total phosphate immobilization (20%) were substantially less than the results of the batch equilibration experiments and phosphate adsorption predicted by other researchers examining near pure natural and synthetic geomedia due to the compositional heterogeneity of the fly ash. Nevertheless, for the amorphous and crystalline phases studied, the immobilization of phosphate in the Type F fly ash is attributed to the formation of insoluble aluminum and iron phosphates at low to medium values of pH.

Adsorption↗
PubMed1998

L-374,087, an efficacious, orally bioavailable, pyridinone acetamide thrombin inhibitor.

Replacement of the amidinopiperidine P1 group of 3-benzylsulfonylamino-6-methyl-2-pyridinone acetamide thrombin inhibitor L-373,890 (2) with a mildly basic 5-linked 2-amino-6-methylpyridine results in an equipotent compound L-374,087 (5, Ki = 0.5 nM). Compound 5 is highly selective for thrombin over trypsin, is efficacious in the rat ferric chloride model of arterial thrombosis and is orally bioavailable in dogs and cynomolgus monkeys. The structural basis for the critical importance of both methyl groups in 5 was confirmed by X-ray crystallography.

Administration, Oral↗