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At least 1,261 records · Page 70Linked to original sources
PubMed1995

Attachment and proliferation of osteoblasts and fibroblasts on biomaterials for orthopaedic use.

Using a variety of cell types, cell attachment and growth was studied on prospective (polyethersulphone (PES) and polyetheretherketone) and currently used (titanium 318 alloy, cobalt chrome molybdenum alloy and ultra-high molecular weight polyethylene (UHMWPE)) orthopaedic biomaterials. Proliferation of fibroblasts and osteoblasts was measured using incorporation of tritiated thymidine into total DNA. Attachment of cells was assessed by indirect immunofluorescent labelling of vinculin, a component of the cell's focal adhesion plaque. The degree of cell attachment was quantified on the materials by determining the mean number of adhesion plaques and using an image analysis system to determine the mean total area of plaques per cell. Fibroblasts and osteoblasts responded differently to the materials tested. When grown on PES surfaces, rat tail fibroblasts synthesized significantly greater amounts of DNA than cells on all other surfaces, whilst fibroblasts on UHMWPE synthesized significantly less DNA than cells on all other materials. Interestingly, there was no significant difference between the amounts of DNA synthesized by osteoblasts grown on the various materials. Determination of the number of vinculin adhesion plaques per cell and the mean total area of the plaques per cell showed that the attachment of fibroblasts to UHMWPE was significantly reduced compared with other materials. In contrast there was no significant difference in the adhesion of osteoblasts to different materials. Scanning electron microscope (SEM) observations of cells on the materials correlated with the morphometric data. Cells with the greatest number and area of adhesion plaques were well spread and flattened whilst those with the least number of adhesion plaques were more rounded and less spread.

Actins↗
PubMed1995

In vitro biocompatibility testing of polymers for orthopaedic implants using cultured fibroblasts and osteoblasts.

The biocompatibility of two polymers for potential use as orthopaedic implant materials in an isoelastic hip prosthesis was investigated. The interactions of polyetheretherketone (PEEK) and epoxy resin polymers (with and without carbon fibre reinforcement) with both fibroblasts and osteoblasts were tested using cell protein, intracellular reduced glutathione (GSH), leakage of lactate dehydrogenase and the MTT assay as indices of cellular cytotoxicity. The epoxy resin polymer was slightly cytotoxic to and inhibited the growth rate of fibroblasts (as assessed by total cell protein), and depleted GSH in both cell types. In contrast, the PEEK material did not display overt signs of cytotoxicity and, in fact, increased osteoblast cell protein content. This suggests that, of these two materials, PEEK would be the one of choice for development of an isoelastic implant and, in view of its stimulatory effect on osteoblast protein content, it may encourage ingrowth of bone around the prosthesis and thus minimize joint loosening.

3T3 Cells↗
PubMed1996

Long-term compressive property durability of carbon fibre-reinforced polyetheretherketone composite in physiological saline.

In total hip arthroplasty, concerns such as corrosion and stress shielding associated with stiff metallic femoral components have led to the development of low stiffness advanced fibre-reinforced polymer (FRP) composite femoral components. Carbon fibre-reinforced polyetheretherketone (CF/PEEK) composite material is now one of the primary material systems being considered for composite hip stem development. As a hip stem, a composite material must be able to support a complex state of stress in the in vivo environment without failure. Considering the loading conditions of a hip stem (superimposed compression and bending), and the fact that FRP composites typically possess lower compressive than tensile strength, the compressive behaviour of FRP composites becomes very important for femoral component design. This paper presents an investigation of the long-term durability of 0 degree and 90 degrees compressive strengths of CF/PEEK composite following physiological saline saturation. 0 degree and 90 degrees compressive moduli and Poisson ratio (v12) properties are also reported. Samples were tested following conditioning in physiological saline at 37, 65 and 95 degrees C for time periods from 0 to 5000 h. Dry samples were tested as controls. Results show no significant loss in compressive property values of the saline-saturated or the dry control samples as a function of conditioning time or temperature.

Benzophenones↗
PubMed1996

Tissue engineering scaffolds using superstructures.

Here, scaffolds as cell and tissue carriers are approached from an engineering point of view, emphasizing material superstructuring in the design of supports. Superstructure engineering provides optimal spatial and nutritional conditions for cell maintenance by the arrangement of structural elements (e.g. pores or fibres) so as to vary the order of cell to cell contact. This approach is illustrated in the design of several scaffolds: knitted fabrics as three-dimensional superstructures for optimized osteosynthesis implants, a new injectable open porous implant system, an angiopolar non-degradable ceramic cell carrier, and an injectable or microsurgically implantable entangled carrier system. The implications for tissue engineering are discussed.

Anisotropy↗
PubMedDate not supplied

Gastrointestinal blood loss induced by bromfenac sodium, aspirin, and placebo.

The effects of bromfenac sodium, aspirin, and placebo on gastrointestinal (GI) blood loss were compared. In a 22-day, randomized study, healthy men received treatment with either bromfenac sodium 300 mg/d, aspirin 3900 mg/d, or placebo for 10 days. On days 3 through 9 and days 20 through 22, all patients received placebo. Fecal blood was measured using the chromium 51-labeled red blood cell technique. Thirty-seven subjects entered the treatment period (13 in the aspirin group, 12 in the bromfenac sodium group, and 12 in the placebo group). The mean change in fecal blood loss during the treatment period compared with the baseline period was significantly greater in the aspirin group (8.00 +/- 4.17 mL/d) than in the bromfenac sodium group (1.63 +/- 1.01 mL/d). Blood loss in both the aspirin and bromfenac sodium groups was significantly greater than in the placebo group (-0.12 +/- 0.25 mL/d). It is concluded that bromfenac sodium 300 mg/d, a higher daily dose than the proposed daily dose, causes significantly less GI blood loss than aspirin 3900 mg/d.

Adolescent↗
PubMed1991

Technique for quantification of LTB4-induced changes in peripheral granulocyte counts in vivo in the rabbit.

A method to quantify leukotriene B4-(LTB4)-induced changes in peripheral granulocyte counts in the rabbit is described. Rabbits were surgically prepared with vascular access ports cannulating the right external jugular vein. This preparation made possible rapid, accurate, and repeated sampling of venous blood. Intravenous infusion of LTB4 (0.5-2 micrograms/mL) into the left marginal ear vein was found reproducibly to cause an initial, rapid (1-5 min) leukopenia (64%-100% reduction) followed by an extended (20-30 min) leukocytosis (121%-178% increase). Saline infusion for 30 min resulted in no changes in peripheral granulocyte number. The method described was sensitive and reproducible enough to allow evaluation of the LTB4 receptor antagonist, LY223982 (10 mg/kg, i.v.), which was shown to block both the leukopenia and the leukocytosis induced by LTB4 infusion.

Animals↗
PubMed1991

Which components in broad-spectrum sunscreens are most necessary for adequate UVA protection?

There is an increasing need for broad-spectrum sunscreens that afford adequate UVA protection. In the selection of such a sunscreen, the sun protection factor is of no real value because it gives an indication of only the UVB protection. As long as the methods used to determine the real UVA protection factor are not standardized, the most valid information is the formula of the sunscreen. To determine the components that are most necessary for optimal UVA protection, different components were compared separately and in combination in human subjects by different methods. The physical agents tested gave only relatively weak UVA protection in both the shorter and the longer UVA ranges. Dibenzoylmethane derivatives are more efficient than the physical agents, but only in the shorter UVA range. The UVA protection afforded by the combination of a dibenzoylmethane derivative and physical agents appears to be cumulative.

Adult↗
PubMed1995

Effects of the catechol-O-methyltransferase inhibitor tolcapone in Parkinson's disease: correlations between concentrations of dopaminergic substances in the plasma and cerebrospinal fluid and clinical improvement.

We compared the concentrations of dopaminergic substances in the plasma and cerebrospinal fluid (CSF) with clinical severity in patients with Parkinson's disease (PD) under L-dopa/carbidopa treatment and under L-dopa/carbidopa+tolcapone treatment. Compared with treatment with L-dopa/carbidopa alone, the co-administration of tolcapone produced a significant decrease in clinical severity; a remarkable reduction in the 3-O-methyldopa (3-OMD) concentration and significant increase in the L-dopa concentration both in the plasma and CSF; and a significant increase in the dopamine concentration in the CSF. The clinical effects of tolcapone were closely correlated with the reduction in the 3-OMD concentration, but not with the increase in the dopamine and L-dopa concentrations in the CSF.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1994

General properties and clinical possibilities of new selective inhibitors of catechol O-methyltransferase.

1. The structure of catechol O-methyltransferase (COMT) has been recently characterized and a series of new and selective COMT inhibitors developed. 2. Entacapone, nitecapone and tolcapone are nitrocatechol-type potent COMT inhibitors in vitro (Ki in nanomolar range). They are also very selective for COMT and active in vivo even after oral administration. CGP 28014 is a pyridine derivative that is active only in vivo. 3. In animal studies, these compounds inhibit effectively the O-methylation of L-dopa, thus improving its bioavailability and brain penetration and potentiating its behavioural effects. 4. Entacapone and nitecapone have mainly a peripheral effect whereas tolcapone and CGP 28014 also inhibit O-methylation in the brain. 5. In man, entacapone, nitecapone and tolcapone all inhibit dose dependently the COMT activity in erythrocytes. These COMT inhibitors also decrease the amount of COMT dependent metabolites of adrenaline and noradrenaline in plasma. 6. In human volunteers, entacapone, tolcapone and CGP 28014 improve the bioavailability of L-dopa and inhibit the formation of 3-O-methyldopa. 7. In the first clinical studies in patients with Parkinson's disease, both entacapone and tolcapone potentiate and prolong the therapeutic effect of L-dopa.

Animals↗
PubMed1992

Separation and determination of aminohalogenbenzophenones by high-performance liquid chromatography with electrochemical detection.

A high-performance liquid chromatographic method with electrochemical detection has been developed for the determination of three aminohalogenbenzophenones: 2-amino-2',5-dichlorobenzophenone, 2-amino-5-chlorobenzophenone and 2-amino-5-bromo-2'-fluorobenzophenone, metabolites of benzodiazepinooxazoles and other psychotropic drugs. A mobile phase of methanol-water (65:35), containing 5 mM KH2PO4 appeared to be the optimal when a 4-microns, 60-A Nova-Pak C18 column and a flow-rate of 0.75 ml/min (130 bar) were used. The temperature was optimized at 30 degrees C. The amperometric detector, equipped with glassy carbon electrode, was operated at 1.3 V versus Ag/AgCl in the DC mode. The method was applied to the determination of these compounds at two concentration levels: ppm and ppb (ng/cm3) using 2-amino-5-chlorobenzophenone as internal standard. The limit of determination was 750 pg/ml of biological fluid for each compound, and recoveries greater than 97% were obtained for spiked samples of urine and serum, using C18 Sep-Pak cartridges in the sample clean-up procedure.

Anti-Anxiety Agents↗
PubMed1996

High-performance liquid chromatographic assay for common sunscreening agents in cosmetic products, bovine serum albumin solution and human plasma.

This paper reports the development of a reversed-phase high-performance liquid chromatographic assay for quantifying five of the most common sunscreen agents, namely 2-ethylhexyl-p-dimethyl aminobenzoate (Escalol 507), 2-ethylhexyl-p-methoxycinnamate (Parsol MCX); 4-tert.-butyl-4'-methoxydibenzoylmethane (Parsol 1789), 2-hydroxy-4-methoxybenzophenone-3 (oxybenzone) and 2-ethylhexyl-salicylate (octylsalicylate). The assay permits analysis of the sunscreen agents in formulations and in biological fluids, including bovine serum albumin (BSA) solution, a common additive to in vitro skin diffusion cell receptor fluids, as well as human plasma. Separation was achieved using an ODS C154 column with a methanol-water (88:12) mobile phase. The analytes were detected by ultraviolet light absorption at a wavelength of 315 nm. The assay was linear with minimum detectable limits, calculated as greater than 3-times the baseline noise level: for oxybenzone and Escalol 507, 0.05 microgram/ml; for Parsol 1789 and Parsol MCX, 0.1 microgram/ml; for octylsalicylate, 1 microgram/ml. Recoveries from both plasma and 2% BSA were within the range 89-107%. The inter- and intra-day coefficients of variation for the five agents were not more than 4% at the upper end of the linear range and not more than 10% at the lower end. Preliminary stability studies of the sunscreen agents in a commercial product and in two diffusion cell receptor fluids were also conducted.

4-Aminobenzoic Acid↗
PubMed1995

Positron emission tomography in drug evaluation: influence of three different catechol-O-methyltransferase inhibitors on metabolism of [NCA] 6-[18F]fluoro-L-dopa in rhesus monkey.

We compared the influence of three different catechol-O-methyltransferase (COMT) inhibitors (CGP 28014, OR-611 and Ro 40-7592) on the metabolism of no-carrier-added (NCA) 6-[18F]fluoro-L-dopa (6-FDOPA) in one Rhesus monkey. All three COMT inhibitors improved 6-FDOPA availability in plasma, increased the specific uptake in the brain and thus improved 6-FDOPA uptake measurements using positron emission tomography (PET). Best results were obtained with Ro 40-7592.

Amidines↗
PubMed1996

Synthesis and evaluation of an 18F-labeled dopa prodrug as a PET tracer for studying brain dopamine metabolism.

In the quantitative studies of presynaptic dopamine metabolism by PET with 6-[18F]fluoro-L-dopa (6-[18F]FDOPA), metabolic analysis in the plasma is required to determine the precise input function because of susceptibility of the compound to peripheral metabolism. In this study, we prepared 6-[18F]-fluoro-O-pivaloyl-L-dopa (6-[18F]FPDOPA) as a prodrug of 6-[18F]FDOPA, and evaluated its potential as a PET tracer in mice. If the 6-[18F]FPDOPA is stable peripherally and is hydrolyzed to 6-[18F]FDOPA in the brain tissues, disadvantage of the 6-[18F]FDOPA will be overcome. Compared with the 6-[18F]FDOPA, the initial brain uptake of the 6-[18F]FPDOPA was lower; however, the uptake in the latter become comparable, and the uptake ratios of striatum to other reference regions were larger. Medication of mice with inhibitors of aromatic amino acid decarboxylase and catechol-O-methyl transferase greatly enhanced the striatal uptake of the two compounds. The reduced brain uptake of the compounds by L-phenylalanine-loading suggested transport through the blood-brain barrier by the neutral amino acid transporter. HPLC analysis showed the presence of 6-[18F]FPDOPA, 6-[18F]FDOPA and 6-[18F]fluorodopamine in the striatum; however, 6-[18F]fluoro-3-O-methyl-L-dopa was a predominate metabolite in the brain and plasma as in the case of [18F]FDOPA. Results suggested that 6-[18F]FPDOPA had characteristics as a prodrug of 6-[18F]FDOPA; however, the compound was also labile to metabolic alteration in vivo.

Animals↗
PubMed1992

A rapid microtiter plate method for the detection of lysozyme release from human neutrophils.

An improved method was devised to measure lysozyme secreted from human neutrophils [polymorphonuclear leukocyte (PMN)] using a microtiter plate reader capable of analyzing enzyme kinetics. The assay is an adaptation of the classical photometric method which detects changes in the turbidity of a bacterial suspension, Micrococcus lysodeikticus, caused by the enzymatic activity of lysozyme. A standard curve using chicken egg white lysozyme was generated, and activity was detectable between the range of 1 and 100 ng/ml. Leukotriene B4 (LTB4)-induced lysozyme release from human PMN was comparable in both the standard assay and the microtiter plate adaptation with EC50 values of 6.5 and 7.2 nM, respectively. Other select stimuli and their receptor antagonists were also used to evaluate the method. Dose-response curves for chemotactic hexapeptide (CHP), recombinant human C5a (rhC5a), and platelet-activating factor (PAF) resulted in EC50 values of 0.14, 0.80, and 542.00 nM, respectively. Inhibition of lysozyme release was studied using receptor antagonists N-t-Boc-L-methionyl-L-leucyl-L-phenylalanine (N-t-Boc), LY223982, and protamine, which are putative inhibitors of formyl peptides (i.e., CHP), LTB4, and C5a, respectively. N-t-Boc inhibited CHP-induced (0.2 nM) enzyme release with an IC50 of 2 microM; LY223982 blocked LTB4-induced (20 nM) release resulting in an IC50 of 52 nM; and protamine inhibited rhC5a-induced (1.5 nM) release with an IC50 of 2 microM. Further studies revealed that CHP, LTB4, and rhC5a were selectively inhibited by their respective antagonists, albeit LY223982 and protamine were also weak inhibitors of CHP and LTB4, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed2004

Purification, tandem mass characterization, and inhibition studies of oxidosqualene-lanosterol cyclase enzyme from bovine liver.

The oxidosqualene-lanosterol cyclase (OSC) from bovine liver has been isolated from the microsomal membrane fraction and purified to homogeneity by ultracentrifugation, Q-Sepharose, hydroxyapatite, and HiTrap heparin chromatographies. The purified protein required Triton X-100 to retain its highest activity. The cyclase had a molecular mass of approximately 70 and approximately 140 kDa, as evidenced by a single protein band on silver-stained SDS-PAGE and Coomassie-stained PAGE, respectively. Results from Edman degradation of OSC suggested that it might have a blocked N-terminus. Further peptide mapping coupled with tandem mass spectrometric determination identified three peptide fragments, ILGVGPDDPDLVR, LSAEEGPLVQSLR, and NPDGGFATYETK, which are highly homologous to human, rat, and mouse OSCs. The purified cyclase showed pH and temperature optima at pH 7.4 and 37 degrees C, respectively. The apparent K(M) and k(cat)/K(M) values were estimated to be 11 microM and 1.45 mM(-1)min(-1), respectively. Inhibition studies using both Ro48-8071 and N-(4-methylenebenzophenonyl)pyridinium bromide showed potent inhibition of OSC with an IC(50) of 11 nM and 0.79 microM, respectively. Results from DTNB modification and DTNB coupled with Ro48-8071 competition study suggest that two sulfhydryl groups are involved in the catalysis but not located in the substrate binding pocket or catalytic active site. The purified OSC was maximally inactivated by diethyl pyrocarbonate near neutral pH and re-activated by hydroxylamine, indicating the modification of histidine residues. The stoichiometry of histidine modification and the extent of inactivation showed that two essential histidine residues per active site are necessary for complete bovine liver OSC activity.

Amino Acid Sequence↗