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PubMed1991

Correlation of cytotoxicity, filler loading and curing time of dental composites.

Previous studies have shown that dental resin composites tested in cell culture produce cytotoxic effects on human gingival tissues. In this study, the cytotoxic potential of resin composites on primary human gingival fibroblast cultures was evaluated, based on inhibition of cellular protein synthesis measured by [35S] methionine incorporation. Both resin content and percentage of monomer conversion were considered as potential causes of cytotoxicity. Three resin composites were selected to provide a range of filler content from 45 to 86 wt%. Duplicate sample discs (1 mm thick x 10 mm diameter) of each composite were polymerized for 15, 30 and 60 s, followed by heat (110 degrees C, 10 min), and the degree of monomer conversion for each sample group was measured using Fourier transform infrared spectrophotometry. Identically fabricated discs were placed into 35 mm culture dishes with gingival fibroblasts and incubated for 24 h at 37 degrees C. The cell monolayers then were labelled at 24 h with [35S] methionine, washed and solubilized; then incorporated radioactivity was quantitated by liquid scintillation spectrometry. For each composite, as the percentage of monomer conversion increased, cellular toxicity decreased. In comparing different composites having similar monomer conversions, it was found that the filler/resin ratio was not the only factor determining the composite's relative toxicity.

Biocompatible Materials↗
PubMed1995

New polyurethane compositions able to bond high amounts of both albumin and heparin. Part I.

In order to prepare polymers provided with better haemocompatibility with respect both to the coagulative cascade and to platelet aggregation and activation, we have synthesized new polyurethanes containing in the chain-extender [di(2-hydroxyethyl)hexadecylamine] both a long chain alkyl group (able to bond albumin) and a tertiary ammonium group able, after suitable quaternization reaction, to bind ionically significant amounts of heparin. The amounts of heparin and albumin bonded to the polymer films were determined spectrophotometrically. A biological in vitro evaluation of the heparinized and albuminized films was also carried out with respect to blood coagulation factors (by activated partial thromboplastin time measurements) and to platelet adhesion and activation (by platelet count and scanning electron microscopy examination). It was seen that the type of adsorption sequence for albumin and heparin, respectively, onto the various homo- and copolymer films, plays an important role on their biological properties; the possible mechanisms involved are also discussed on the basis of X-ray photoelectron spectroscopy and attenuated transmission reflectance evaluation of the polymer surfaces.

Albumins↗
PubMed1992

Diuretic activity of organomercury (II) complexes of theophylline and theobromine.

Organomercury(II) complexes of the types, p-XC6H4HgL (A) and p-XC6H4HgCl(L') (B) [LH = theophylline; L' = theobromine; X = Me, NO2], have been synthesised and characterized. Conductance measurements indicate that the complexes are non-electrolytes. The structures of the complexes have been elucidated by spectral studies (IR, UV, and 1H, 13C NMR). The complexes have been tested for diuretic activity. The structure-activity relationship has been propounded.

Animals↗
PubMed1995

Synthesis, characterization, and crystal structure of [Cu(cinoxacinate)2].2H2O complex: a square-planar CuO4 chromophore. Antibacterial studies.

The structural and spectroscopic properties of a new copper (II) complex of cinoxacin (HCx) have been investigated. The complex [Cu(Cx)2].2H2O crystallizes in the monoclinic system, space group P2(1)/c. The cell dimensions are: a = 7.998(2), b = 7.622(1), c = 18.955(6) A, beta = 94.38(2) degree, V = 1154.6(6) A3, Z = 2. The structure was refined to R = 0.051. The crystal is composed of [Cu(Cx)2] units and uncoordinated water molecules. The Cu(II) ion, at a center of symmetry, is coordinated to two cinoxacinate (Cx) ligands related by the inversion center. Each cinoxacinate acts as bidentate ligand bonded to the cation through its carboxylate oxygen atom and through its exocyclic carbonyl oxygen atom, resulting in a CuO4 chromophore in a crystallographically planar configuration. The complex was screened for its activity against several bacteria, showing the same antimicrobial activity as the corresponding ligand.

Cinoxacin↗
PubMed1991

The identification of a new heterocyclic amine mutagen from a heated mixture of creatine, glutamic acid and glucose.

A new heterocyclic amine mutagen was isolated from a dry-heated reaction of the natural meat components creatine, glutamic acid and glucose. Heating creatine and glutamic acid alone had only one seventh of the Ames/Salmonella mutagenic activity of the glucose, creatine and glutamic acid mixture. The major mutagenic compound was purified by HPLC using the Ames/Salmonella test to guide the purification. The mutagen has a molecular weight of 244 and a composition of C12H12N4O2 as determined by high-resolution mass spectrometry. NMR and IR spectral data suggest the structure is a 2,6-diamino-3,4-dimethyl-7-oxo-pyrano[4,3-g]benzimidazole. Mutagenic activity in strains TA1538, TA98 and TA100, was approximately 7000, 5200, and 550 revertants per microgram, respectively. The formation of this mutagen from natural meat components suggests that it may be present in cooked food. The preferential formation of this mutagen with glucose shows that glucose can be important in dry-heated mutagen-forming reactions.

Chromatography, High Pressure Liquid↗
PubMed1983

Identification of a mutagenic substance, in Rubia tinctorum L. (madder) root, as lucidin.

Mutagenicity of the extract from Rubia tinctorum L. (madder) root was demonstrated on Salmonella typhimurium TA100 and TA98. The active substance wa purified and characterized by TLC, UV spectrum, IR spectrum, mass spectrum and [1H]NMR spectrum. All the mutagenic activity of the extract from the root of Rubia tinctorum L. was due to lucidin (1,3-dihydroxy,2-hydroxymethyl-9, 10-anthraquinone).

Anthraquinones↗
PubMed1990

Morphological changes of poly(ethylene terephthalate) on multiple steam sterilization.

Poly(ethylene terephthalate) (PET) was steam sterilized by autoclaving for 15, 30 and 60 min. The thermal properties, T m, delta-H and percent crystallinity were determined using differential scanning calorimetry. Molecular weight distribution was determined using gel permeation liquid chromatography. Crystallinity of PET was also monitored by infrared spectrophotometry. The analyses indicate that that chain scission and cyclization reactions take place in PET, forming cyclic oligomers, that can migrate to the polymer surface and which may affect long term performance of PET.

Calorimetry, Differential Scanning↗
PubMed1987

Occurrence of carotenoids and sporopollenin in Nanochlorum eucaryotum, a novel marine alga with unusual characteristics.

Pigment analysis of Nanochlorum eucaryotum on two strains grown under different gaseous conditions was performed. Air-gassed control cultures did not differ qualitatively with respect to the content of chlorophylls a and b, carotenes alpha and beta, lutein, violaxanthin, neoxanthin and cryptoxanthin in comparison with cultures grown under natural gas. The absolute pigment content per cell increased in cultures grown with natural gas. Growth of N. eucaryotum depends on CO2 which is present in concentrations up to 2.0 vol% in natural gas. N. eucaryotum cannot utilize methane and is therefore not methylotrophic. In cultures of N. eucaryotum grown with natural gas and in air-gassed cultures under nitrogen deficient conditions the secondary carotenoids canthaxanthin and astaxanthin could be detected. In air-gassed cultures of strain N. eucaryotum Colona the same secondary carotenoids have been found, while secondary carotenoids were never found in strain N. eucaryotum Mainz. Cell walls of N. eucaryotum always contain sporopollenin as confirmed by isolation, elemental analysis, infrared absorption spectrophotometry, acetolysis-resistance and electron microscopy.

Biopolymers↗
PubMed1991

Preparation and characterization of polymer coated small unilamellar vesicles.

Glucose oxidase was entrapped in small unilamellar vesicles composed of phosphatidylcholine, dicetyl phosphate and cholesterol. Prediction of the enzyme content of liposomes by calculations based on input concentrations of lipid and protein, dimensions of the lipids and the liposomes yielded one protein per vesicle. The entrapment efficiency was experimentally determined to be about 13%. On the other hand the entrapment efficiency for the small chromate ions was found to be significantly lower (0.1%). The liposomes were then coated with a polymer, poly(1,4-pyridinium diylethylene salt). It was possible to remove the lipoid material from underneath the polymer layer with various techniques. The effect of sonication and treatment with organic solvents (tested for this purpose) on enzyme activity were found to be very significant and Triton X-100 was chosen for this purpose. It was shown that the enzyme within the remaining net has 89% of its original activity.

Biomechanical Phenomena↗
PubMed1991

Isolation of estradiol-2,3-quinone and its intermediary role in melanin formation.

We have reported previously that 2-hydroxyestradiol can be oxidized in the presence of catechol by mushroom tyrosinase, with a stoichiometric requirement of molecular oxygen (Jacobsohn, G.M. and Jacobsohn, M.K. (1984) Arch. Biochem. Biophys. 232, 189-196). It is then incorporated into melanin (Jacobsohn et al. (1988) J. Steroid Biochem. 31, 377-385). We now report on the isolation and characterization of the o-quinone as a product of the enzyme reaction from 2-hydroxyestradiol. The o-quinone was isolated from incubates and identified by its FTIR spectrum, in particular, by the appearance of a new band at 1652 cm-1, its migration in HPLC systems, its ultraviolet spectrum, its derivatization with phenylenediamine and comparison of these properties with the periodate oxidation product of the same substrate. The enzyme oxidation of the catechol estrogen was performed at 37 degrees C and did not require an activator; dopa at concentrations higher than 5 microM was inhibitory. At concentrations lower than 5 microM, dopa acted catalytically and was not consumed during the course of reaction. Ascorbic acid inhibited the reaction. The quinone exhibited both reversible and irreversible binding to performed melanin and to melanin actively synthesized by the enzyme. Incubation of 18 microM newly synthesized [4-14C]estradiol-2,3- quinone with mushroom tyrosinase for 45 min at 37 degrees C in presence of 400 microM dopa showed incorporation (irreversible binding) of 6.3 +/- 0.3% of label into melanin produced during the course of reaction. Similar incubations for 45 min of pre-formed melanin prepared from 400 microM dopa showed incorporation of 4.4 +/- 0.2% of the label. Reversible binding was 10-times greater than incorporation for both actively synthesized and preformed melanins. In the absence of dopa or catechol, enzyme incubations of either 2-hydroxy-estradiol or its quinone did not yield melanin. Data suggest that estradiol-2,3-quinone is an intermediate in the incorporation of the catechol estrogen into melanin by tyrosinase.

Chromatography, High Pressure Liquid↗