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PubMed2005

Release of bioactive BMP from dextran-derived microspheres: a novel delivery concept.

Recent developments of biotechnology have produced a great variety of protein and bioactive drugs. For these drugs to be used therapeutically, suitable drug delivery systems have become increasingly essential. Dextran-derived biomaterials have been considered to be compatible matrices for protein and bioactive drugs because of their hydrophilic properties and ability to control drug dissolution and permeability. A novel class of dextran-glycidylmethacrylate (Dex-GMA)/poly(ethylene glycol) (PEG) microspheres were designed and synthesized by polymerization of Dex-GMA emulsified in an aqueous PEG solution. Dex-GMA was prepared by substituting the hydroxyl groups in Dex by GMA. The drug loading and in vitro drug release was evaluated by routine procedure and the biological activity of BMP-loaded microspheres was studied by experimental cytology methods. Recombinant human bone morphogenetic protein-2 (rhBMP-2) were entrapped in dextran-derived microspheres quantitatively and with full preservation of their biological activity. In vitro release kinetics indicated that dextran-derived microspheres could retain rhBMP-2 in a variable manner depending on the preparation and degradation of the microspheres. The release profiles of rhBMP-2 from microspheres as a function of time showed that rhBMP-2 releasing kinetics in vitro fitted to first-order and Higuchi equations. The release profile in vitro was in accord with two phases kinetics law and more than 60% drug were released during 20 days. Cytology studies showed rhBMP-2 microspheres have good biological effects on cultured periodontal ligament cells, and could achieve a longer action time than concentration of rhBMP-2 solution. These properties make those microspheres interesting osteo-conductive BMP carriers, allowing to decrease the amount of implanted factor required for tissue regeneration.

Alkaline Phosphatase↗
PubMed1997

Studies directed toward a mechanistic evaluation of aromatase inhibition by androst-5-ene-7,17-dione. Time-dependent inactivation by the 19-nor and 5 beta, 6 beta-epoxy derivatives.

To gain further insight into the mechanism for inactivation of aromatase by androst-5-ene-7,17-dione (1) and its 19-nor analog 4, 10 beta-oxygenated steroids 5 and 6, delta 1(10)-steroid 7, and 19-oxo-5 beta,6 beta-epoxy compound 8 were synthesized and tested for their ability to inhibit aromatase in human placental microsomes. All of the steroids studied inhibited the enzyme in a competitive manner with apparent Ki values ranging from 1.1 to 35 microM. The delta 1(10)-compound 7 was the most potent inhibitor among them. All of the inhibitors caused a time-dependent inactivation of aromatase in the presence of NADPH in air with the kinact values ranging from 0.036 to 0.190 min-1. The substrate androstenedione protected the inactivation, but a nucleophile, L-cysteine, did not, in each case. In contrast, each inhibitor did not cause the time-dependent inactivation in the absence of NADPH. These results show that the 5 beta,6 beta-epoxide 8 and/or the dienone 7 are not a reactive electrophile involved in the irreversible binding to the active site of aromatase during the mechanism-based inactivation caused by the suicide substrates 1 and/or 4.

Androstanes↗
PubMed1999

Dimethacrylate monomers with varied fluorine contents and distributions.

OBJECTIVES: There are many unique properties associated with fluorinated polymers that make these materials attractive for use in the challenging oral environment. This study was devised to better define the influence of fluorine content and its structural distribution on properties of fluorinated resins and composites, especially with regard to their water-related and mechanical properties. METHODS: A series of fluorinated dimethacrylate monomers was prepared by reaction of aromatic diepoxides with fluoroalcohols and subsequent conversion of the resulting diols to the methacrylates. Composites based on monomer systems comprised of the fluorinated monomers with 1,10-decamethylene dimethacrylate and reinforced with silanized quartz filler were evaluated for conversion, water contact angle, water sorption and diametral tensile strength. RESULTS: By selection of reactants, fluorine was introduced as trifluoromethyl groups, extended fluoroalkyl pendant chains, or combinations of the two. Photopolymerization conversion among the experimental composites was generally equal to or greater than that of a conventional Bis-GMA/TEGDMA composite. While the water contact angles generally increased with fluorine content, no correlation was obtained between fluorine content and water sorption of the composites. The mechanical strength of the fluorinated composites showed a general decline with increasing fluorine content and consistent variations due to specific structural features. SIGNIFICANCE: A versatile route to fluorinated dimethacrylates with diverse structural and fluorine distribution patterns is presented. Composites from these monomers are very hydrophobic but have relatively low mechanical strength. The monomers described can be considered as useful additives to moderate the water sorption of conventional resins. However, the results of this study point to specific fluorinated resin structures that are expected to provide a more optimal balance between hydrophobicity and mechanical strength that will improve the long-term performance of dental composites.

Alcohols↗
PubMed1998

Novel hydrophilic cyclic monomers in hydrogel synthesis.

A range of hydrogels was prepared by the copolymerisation of 2-hydroxyethyl methacrylate (HEMA) with various hydrophilic cyclic monomers (CM) derived from cis-1,2-dihydroxy-3,5-cyclohexadiene (DHCD). The specific systems investigated were the cis-1,2-bis(2,3-epoxybutanoyloxy)-, cis-1,2-bis(10,11-epoxyundecanoyloxy)-, cis-1,2-bis(trimethylsiloxy)- and cis-1,2-bis(tert-butyldimethylsiloxy)-3,5-cyclohexadienes. The EWC, tensile strength and initial modulus of the poly HEMA-CM hydrogels derived from the epoxy compounds showed lower EWCs but similar mechanical properties compared with polyHEMA itself. Treatment of the hydrogel derived from cis-1,2-bis(2,3-epoxybutanoyloxy)-3,5-cyclohexadiene with 20% sodium hydroxide increased the EWC value markedly but produced highly fragile materials.

Biocompatible Materials↗
PubMed2006

The phomactins. A novel group of terpenoid platelet activating factor antagonists related biogenetically to the taxanes.

A description of the structurally unusual "phomactin" family of platelet activating factor antagonists recently found in the marine fungus Phoma sp. is presented. The phomactins show an interesting structural and biosynthetic relationship with the more familiar taxane group of antitumor compounds isolated from yew trees. The Account highlights and discusses this unique relationship and also presents a cogent picture of plausible biogenetic interrelationships within the family of phomactins. Complementary synthetic endeavors with the phomactins are interwoven in the discussions, alongside contemporaneous biosynthetic studies with both the phomactins and the taxanes.

Animals↗
PubMed2004

New methodology for the determination of phthalate esters, bisphenol A, bisphenol A diglycidyl ether, and nonylphenol in commercial whole milk samples.

This paper reports a new methodology aimed at determining dimethyl phthalate, diethyl phthalate, di-n-butyl phthalate, butylbenzyl phthalate, bis(2-ethylhexyl) phthalate, nonylphenol, bisphenol A, and bisphenol A diglycidyl ether in commercial whole milk. These compounds are used as plastic additives, lacquers, resins, or surfactants and can be found in milk due to contact with plastic materials during food processing and storage. They are all suspected endocrine disrupters or mutagens. A multiresidue method based in solid-phase extraction with C-18 cartridges followed by a cleanup step using disposable cartridges was developed. Detection and quantification were performed by gas chromatography coupled to mass spectrometric (GC-MS) detection using an appropriate surrogate (4-n-nonylphenol) and internal standard [deuterated bis(2-ethylhexyl) phthalate]. Limits of detection were from 0.06 to 0.36 microg/kg and intraday variation from 3 and 27%, with recoveries between 73 and 119%. Five brands of commercial whole milk processed and packed in different ways were analyzed. All samples contained target compounds at concentrations between 0.28 and 85.3 microg/kg, and the total concentration ranged between 79.3 and 187.4 microg/kg, the levels being higher in sterilized milks. Nonylphenol, diethyl phthalate, dibutyl phthalate, and bis(2-ethylhexyl) phthalate were the major contributors.

Animals↗
PubMed2006

"Green" composites from renewable resources: preparation of epoxidized soybean oil and flax fiber composites.

In recent years there has been considerable interest in using natural plant fibers as reinforcements for plastics. The motivation includes cost, performance enhancement, weight reduction, and environment concerns. High performance flax fiber could potentially substitute for glass or carbon fibers as reinforcements for plastics. This study reports the "green" composites obtained from a mixture of epoxidized soybean oil and epoxy resin, 1,1,1-tris(p-hydroxyphenyl)ethane triglycidyl ether (THPE-GE), reinforced with flax fiber. The compression molding method is used for making the composites. Curing agents triethylenetetramine and diethylenetriamine provide better physical properties of the composites than Jeffamine agents D-230 and EDR-148. Both the flexural modulus and the tensile modulus of the composites increase as the amount of THPE-GE increases. The flexural modulus increased at a fiber content of <10 wt %, but there is a decrease beyond 10 wt %. The tensile modulus increases with fiber content until a maximum at 13.5 wt %, and then it decreases. The flax fiber length affected the mechanical properties of the composites: the longer the fiber length, the better are the mechanical properties observed.

Epoxy Compounds↗
PubMed2004

Divergence of carbonyl ylide reactions as a function of diazocarbonyl compound and aldehyde substituent: dioxolanes, dioxolenes, and epoxides.

The products from dirhodium(II) acetate-catalyzed reactions between diazocarbonyl compounds and a series of benzaldehydes demonstrate the extent of competition between intramolecular and intermolecular trapping of carbonyl ylide intermediates and the electronic effects that govern these transformations. With dimethyl diazomalonate, competition exists between dioxolane and epoxide formation so that with p-anisaldehyde only epoxide formation is observed and with p-nitrobenzaldehyde only 1,3-dioxolane products are formed. With methyl diazoacetoacetate, intramolecular trapping of the intermediate carbonyl ylide results in the sole production of dioxolenes. However, the vinyldiazoacetate analogue of methyl diazoacetoacetate, as its tert-butyldimethlsilyloxy derivative, only produces epoxides in its reactions with substituted benzaldehydes.

Benzaldehydes↗
PubMed2006

Anti versus syn opening of epoxides derived from 9-(3-deoxy-beta-D-glycero-pent-3-enofuranosyl)adenine with Me3Al: factors controlling the stereoselectivity.

Upon epoxidation with dimethyldioxirane, the 2',5'-bis-O-silyl derivatives of 9-(3-deoxy-beta-D-glycero-pent-3-enofuranosyl)adenine gave the respective "3',4'-up" epoxides exclusively. Reaction between these epoxides and Me3Al was investigated in detail. It was found that the stereoselectivity of epoxide ring opening (anti versus syn) varied significantly upon changing the amount of Me3Al, the solvent, the O-silyl protecting group, and the reaction temperature. A possible reaction mechanism is proposed.

Aluminum Compounds↗
PubMed1999

DNA alkylation and interstrand cross-linking by treosulfan.

The anti-tumour drug treosulfan (L-threitol 1,4-bismethanesulphonate, Ovastat) is a prodrug for epoxy compounds by converting non-enzymatically to L-diepoxybutane via the corresponding monoepoxide under physiological conditions. The present study supports the hypothesis that this conversion of treosulfan is required for cytotoxicity in vitro. DNA alkylation and interstrand cross-linking of plasmid DNA is observed after treosulfan treatment, but this is again produced via the epoxide species. Alkylation occurs at guanine bases with a sequence selectivity similar to other alkylating agents such as the nitrogen mustards. In treosulfan-treated K562 cells, cross-links form slowly, reaching a peak at approximately 24 h. Incubation of K562 cells with preformed epoxides shows faster and more efficient DNA cross-linking.

Antineoplastic Agents, Alkylating↗
PubMed2003

Treatment of hyperphosphatemia with sevelamer hydrochloride in hemodialysis patients: a comparison with calcium acetate.

BACKGROUND: Sevelamer hydrochloride is a recently approved calcium- and aluminium-free phosphate binder. A randomized study comparing sevelamer and calcium acetate was performed to assess the control of hyperphosphatemia in hemodialysis patients. METHODS: Administration of phosphate binders was discontinued during a two-week washout period. The patients were then randomized to receive sevelamer or calcium acetate. The laboratory tests were performed monthly for 34 weeks. RESULTS: There was a statistically significant decrease of serum phosphorus in both sevelamer and calcium acetate treatments. In addition, sevelamer improved the lipid profile. CONCLUSION: This study confirms that sevelamer is effective at lowering serum phosphorus in hemodialysis patients and that it has several striking properties that could be beneficial in atherosclerosis in dialysis patients.

Acetates↗
PubMed2002

Survey of bisphenol A and bisphenol F in canned foods.

Bisphenol A (BPA) and bisphenol F (BPF) have been determined in a range of canned foods. Sixty-two different canned foods were purchased from retail outlets in the UK from January to November 2000 and the contents extracted and analysed by GC-MS for BPA and BPF isomers. The following canned products were analysed: fish in aqueous media, 10 samples; vegetables, 10; beverages, 11; soup, 10; desserts, five; fruit, two; infant formula, four; pasta, five; and meat products, five. BPF isomers were not detected in any of the canned foods with detection limits of 0.005 mg kg(-1) for the 2,2' and 2,4' isomers and 0.01 mg kg(-1) for the 4,4' isomer. BPA was detected in 38 samples with a detection limit of 0.002 mg kg(-1). Of these, BPA was quantified in 37 canned foods at levels from 0.007 mg kg(-1), with one sample of meat containing a mean level of 0.38 mg kg(-1). All other samples contained <0.07 mg kg(-1) BPA.

Benzhydryl Compounds↗
PubMed1990

Contamination of a soft-drink manufacturing plant by 210Po.

An investigation was undertaken of the contamination of equipment and flooring by 210Po, released from a static eliminator source, at a soft-drink manufacturing plant. The detection and establishment of extent of contamination, development of decontamination and control procedures and difficulties in implementing those procedures are discussed. Additionally, the likely health effects to workers are assessed. The removal and disposal of contaminated equipment, the use of epoxy compound on the floor to seal fixed contamination and the implementation of a 5-y monitoring program are detailed. The estimated cost of decontamination is provided.

Australia↗
PubMed2001

Effect of pressure on the dynamics of glass formers.

A description of the pressure dependence of the structural relaxation time has been derived from the Adam-Gibbs theory by writing the configurational entropy in terms of the excess heat capacity and the molar thermal expansion. This new equation was tested successfully on dielectric relaxation data for an epoxy compound over a wide range of temperature and pressure.

Journal Article↗
PubMed1991

Contact allergens in registered chemical products.

A national database on chemical products (the Danish Product Register (PROBAS] was searched for products containing selected contact allergens. As of June 1990, a total of 47,400 products were registered in PROBAS. About 27,800 of these were fully computerized. A list of 43 allergens was established, based on the European standard patch test series, substances classified "May cause sensitization by skin contact", text books on contact dermatitis, and clinical experience. The number of products in which each of these allergens was registered varied from 30 to more than 1300. Formaldehyde was registered in all product categories included in the study. Benzyl alcohol, stearic acid, epoxy compounds, diethylenetriamine and butylated hydroxytoluene were registered in more than half of the product categories. Paints/lacquers and hardeners for two-component products (paints, glues, fillers, etc.), cleaning agents, binders, adhesives/glues and toiletries made up the most frequently registered product categories for the allergens listed. The possibilities and limitations of database information on chemical products are discussed.

Allergens↗