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At least 1,747 records · Page 97Linked to original sources
PubMed1999

Popliteal artery occlusion as a late complication of liquid acrylate embolization for cerebral vascular malformation.

Occlusion of arteriovenous malformations of the brain (BAVMs) by means of an endovascular approach with liquid acrylate glue is an established treatment modality. The specific hazards of this procedure are related to the central nervous system. In the case of unexpectedly rapid polymerization of the cyanoacrylate glue and adhesion of the delivering microcatheter to the BAVM, severing the catheter at the site of vascular access is considered an acceptable and safe management. We present a unique complication related to this technique that has not been described yet. Fragmentation and migration of the microcatheter, originally left in place, had caused popliteal artery occlusion, which required saphenous vein interposition, in a 25-year-old man. Suggestions for avoiding this complication are discussed.

Adult↗
PubMed1995

[Results 37 years after insertion of an acrylic implant for scaphoid pseudoarthrosis].

Prosthetic treatment by means of a scaphoid implant was described by Swanson in 1970. The authors report the long-term results of pseudoarthrosis of the scaphoid treated by an acrylic implant at the Rizzoli Orthopaedic Institute in Bologna in 1956. Only one other similar case of long-term treatment by an artificial Vitallium (r) prosthesis was found in the literature.

Carpal Bones↗
PubMed1995

Bacterial growth on antibiotic-loaded acrylic cement. A prospective in vivo retrieval study.

Twenty-three patients with intraoperative culture-proven periprosthetic infection of the hip or knee were enrolled in a prospective cement retrieval study. All were treated with a two-stage technique using antibiotic-loaded acrylic cement as an antibiotic depot. Staphylococcus epidermidis was the most commonly isolated organism (19 of 23 cases). Cement and tissue were examined at second-stage revision for the presence of viable organisms. In this series, no organisms were isolated from the surface of the cement, a 100% concordance with the tissue cultures. A subsequent failure rate of 4.4% (1 case) was seen in this series. Investigation suggests this may represent reinfection from a new strain of organism rather than failure of eradication of the original infection.

Adult↗
PubMed1987

Vacuum mixing of acrylic bone cement.

A partial-vacuum (500-550 mmHg), slow-speed (2 Hz) system for optimal blending of the liquid and powder components of Simplex-P acrylic bone cement was developed to eliminate five different sources of porosity observed with x-ray during the course of cement preparation and specimen fabrication. The vacuum mixing system produces set specimens of less than 1% porosity that have significant improvements over specimens prepared with conventional mixing in the mechanical properties of tensile and compressive strength and uniaxial tensile fatigue life. Hence, a much stronger cement can be available in surgery without any change in original chemical composition.

Bone Cements↗
PubMed1998

Long-term elution of antibiotics from bone-cement: an in vivo study using the prosthesis of antibiotic-loaded acrylic cement (PROSTALAC) system.

A prospective study of 49 patients undergoing a modified 2-stage exchange arthroplasty for infected total hip and knee arthroplasties using the prosthesis of antibiotic-loaded acrylic cement (PROSTALAC) system with a variety of doses of tobramycin and vancomycin was performed. The intra-articular concentrations of tobramycin and vancomycin were measured at the time of removal of the PROSTALAC temporary spacer and reimplantation of a definitive joint arthroplasty prosthesis, at a mean 118 days following initial implantation. The 95% confidence interval of the intra-articular concentration of tobramycin (4.35-123.88 mg/L) was entirely above the breakpoint sensitivity limit for sensitive organisms when at least 3.6 g of tobramycin was used per package of bone-cement but was entirely below it when at most 2.4 g was used. Vancomycin elution was not as good; however, detectable levels were still present in most patients. There was a statistically significant increase in the elution of vancomycin when the dose of tobramycin was increased from at most 2.4 g to at least 3.6 g. The dose of vancomycin in the cement did not influence the elution of either tobramycin or vancomycin. On the basis of these results, the use of at least 3.6 g of tobramycin and 1 g of vancomycin per package of bone-cement is recommended when antibiotic-loaded cement spacers are used in 2-stage exchange arthroplasty for infected total hip and knee arthroplasties.

Anti-Bacterial Agents↗
PubMed2000

Influence of relative humidity on the mechanical and drug release properties of theophylline pellets coated with an acrylic polymer containing methylparaben as a non-traditional plasticizer.

The purpose of this study was to investigate the influence of relative humidity (RH) on the mechanical and dissolution properties of theophylline pellets coated with Eudragit((R)) RS 30 D/RL 30 D containing methylparaben (MP) as a non-traditional plasticizer. The coated beads were stored at 23 degrees C and at different relative humidities (0, 29, 51, 75 and 84% RH). The effect of storage conditions on the rate of drug release from coated beads was determined in pH 7.4 phosphate buffer solution. The mechanical properties, including tensile strength and Young's modulus, of individual beads were determined by a diametral compression method with a Chatillon((R)) tension/compression apparatus. The morphology of the intact and fractured beads was investigated using scanning electron microscopy (SEM). The moisture content of the polymeric films was determined using a Karl Fischer coulometric moisture analyzer. The results from the mechanical studies demonstrated that an increase in the relative humidity resulted in a decrease in the tensile strength and Young's modulus of the coated beads. SEM photographs showed that coated beads stored at 0% RH exhibited brittle fracture failure. The coated beads stored at 84% RH showed ductile behavior, which was attributed to the hydroplasticization effect on the acrylic polymer due to the uptake of moisture. The moisture content in the films was also shown to influence the rate of drug release from Eudragit((R)) RS 30 D/RL 30 D coated beads containing MP as the plasticizer. The change in release profiles could be minimized when the relative humidity was reduced to zero. The dissolution rate of theophylline from the coated beads decreased when stored at high relative humidities. This trend was reversed when the coated beads that were stored at 84% RH for 5 weeks, were then equilibrated at 0% RH.

Humidity↗
PubMed2001

Open wedge tibial osteotomy with acrylic bone cement as bone substitute.

We studied the results of 245 valgus producing high tibial osteotomies performed with the use of an opening wedge technique and rigid internal fixation followed by early passive and active motion of the knee. Previous studies have used iliac bone grafts or hemicollastasis held by an external fixator for opening the osteotomy. In our series the opening was obtained by a block of cement interposed in the postero-medial part of the osteotomy. This series confirms that the opening wedge osteotomy allows good accuracy for the correction. Ninety-three percent of the knees had a correction adjusted between 180 and 187 degrees for the hip-knee-ankle angle. Survivorship analysis showed an expected rate of survival, with conversion to a total knee on the end point, of 94% at 5 years, 85% at 10 years and 68% at 15 years. Conversion to a total knee arthroplasty was accomplished without difficulty in the patients who had this procedure done. We recommend opening wedge tibial osteotomy with acrylic cement bone cement as bone substitute, rigid internal fixation, and early motion for patients who undergo high tibial osteotomy.

Adult↗
PubMed1988

Bone and soft connective tissue response to porous acrylic implants. A histokinetic study.

The ingrowth kinetics of soft and hard tissues near pre-polymerized and in-situ-polymerized large pore, in-situ-polymerized small pore and solid acrylic implants were investigated. Empty cavities served as controls. Aqueous sodium carboxymethyl cellulose (CMC) gel was dispersed in bone cement to create interconnected porosity. After periods of insertion from 2 days up to 26 weeks in frontal and parietal bones in pigs, tissue blocks containing implants were embedded in JB4 and studied by light microscopy. After the disappearance of the CMC-gel, at first only cells invaded the large pore implants but necrotized when at some distance from the implant surface. Later, when blood vessels grew into the pores, accompanying vital fibrous connective tissue was observed. Finally, all pores were filled with connective tissue. Surrounding bone was first resorbed, starting at day 7, creating a soft tissue interface. A zone of bone deposition, starting deep in the remaining bone at day 2, moved towards the implant, thereby bridging the soft tissue interface. At 6 weeks bone grew into the pores, thus anchoring the implant. Continuing deposition of bone around the implant provided a so-called lamina dura effect with all implants. Qualitatively similar tissue kinetics were observed around solid and pre-polymerized large pore implants, evidently in the case of solid implants without tissue ingrowth. Into the small pore implants only superficial soft or hard tissue ingrowth was seen because of the too small interconnections.

Animals↗
PubMed1996

In vivo evaluation of a fluorine-acryl-stylene-urethane-silicone antithrombogenic coating material copolymer for intravascular stents.

RATIONALE AND OBJECTIVES: We evaluated the effectiveness of a fluorine-acryl-styrene-urethane-silicone (FASUS) copolymer as an antithrombogenic coating material for intravascular stents in dogs. METHODS: FASUS copolymer-coated stents were placed in the right iliac veins, and uncoated 304 stainless steel stents were placed in the left iliac veins. We examined platelet deposition, microthrombus formation, and neointimal hyperplasia 4 weeks after stent placement by measuring the activity of 111In-labeled platelets, by using scanning electron microscopy, and by measuring neointimal thickness. RESULTS: Platelet deposition was significantly decreased on coated than on uncoated stents (p < .05). A less pronounced increase in red blood cell deposition was observed at the sites of the coated than uncoated stents (p < .05). Neointimal thickness 4 weeks after stent placement also was significantly less at the sites of the coated stents (0.27 +/- 0.08 mm versus 0.48 +/- 0.23 mm, p < .05). CONCLUSION: FASUS copolymer coating over the vascular stent is effective for preventing thrombus formation and neointimal hyperplasia.

Animals↗
PubMed2002

Polymerization rate and mechanism of ultrasonically initiated emulsion polymerization of n-butyl acrylate.

The factors affecting the induction period and polymerization rate in ultrasonically initiated emulsion polymerization of n-butyl acrylate (BA) were investigated. The induction period takes only an instant in ultrasonically initiated emulsion polymerization of BA without any added initiator by enhancing the N2 flow rate. Increasing temperature, power output and SDS concentration, decreasing the monomer concentration results in further decreasing induction period and enhanced polymerization rate. Under optimized reaction conditions the conversion of BA reaches 92% in 11 min. The polymerization rate can be controlled by varying reaction parameters. The apparatus of ultrasonically initiated semi-continuous and continuous emulsion polymerization were set up and the feasibility was first studied. Based on the experimental results, a free radical polymerization mechanism for ultrasonically initiated emulsion polymerization was proposed, including the sources of the radicals, the process of radical formation, the locus of polymerization and the polymerization process. Compared with conventional emulsion polymerization, where the radicals come from thermal decomposition of a chemical initiator, ultrasonically initiated emulsion polymerization has attractive features such as no need for a chemical initiator, lower reaction temperature, faster polymerization rate, and higher molecular weight of the polymer prepared.

Journal Article↗
PubMedDate not supplied

A study on the random distribution of a red acrylic target fibre.

This project was a target fibre study carried out by the European Fibres Group. Thirty-eight participating laboratories in nineteen countries searched four hundred and thirty five randomly selected top outer garments. The acrylonitrile/vinyl acetate co-polymer target fibre matched those in a red acrylic scarf, marketed in nine of those countries. The sales figures for the last five years were between 5- and 10,000 scarves annually. Matching fibres were found on only two garments, one fibre per garment. The possible origin of these two fibres is discussed. The result showed that the chances of finding a 'collective' of target fibres on a piece of clothing selected at random can be said to be extremely remote.

Acrylonitrile↗
PubMed2005

Surface-reactive acrylic copolymer for fabrication of microfluidic devices.

A surface-reactive acrylic polymer, poly(glycidyl methacrylate-co-methyl methacrylate) (PGMAMMA), was synthesized and evaluated for suitability as a substrate for fabrication of microfluidic devices for chemical analysis. This polymer has good thermal and optical properties and is mechanically robust for cutting and hot embossing. A key advantage of this polymeric material is that the surface can be easily modified to control inertness and electroosmotic flow using a variety of chemical procedures. In this work, the procedures for aminolysis, photografting of linear polyacrylamide, and atom-transfer radical polymerization on microchannel surfaces in PGMAMMA substrates were developed, and the performance of resultant microfluidic electrophoresis devices was demonstrated for the separation of amino acids, peptides, and proteins. Separation efficiencies as high as 4.6 x 10(4) plates for a 3.5-cm-long separation channel were obtained. The results indicate that PGMAMMA is an excellent substrate for microfabricated fluidic devices, and a broad range of applications should be possible.

Amines↗
PubMed2000

Preparation and characterization of thermoresponsive poly(N-isopropylacrylamide-co-acrylic acid) hydrogels: studies with electroactive probes

A new method of preparing thermoresponsive hydrogels consisting of N-isopropylacrylamide (NIPA) and acrylic acid (AA), with a well-defined concentration of an electroactive probe, 1,1'-ferrocenedimethanol (Fc(MeOH)2), is described, and a comparison of the physical and electrochemical properties of NIPA-AA gels with those of aqueous solutions is presented. The NIPA-AA gels undergo a discontinuous volume phase transition at 45 degrees C; this transition results in a release of approximately 40% of the solution mass from the gel phase. Characterization of hydrogels with electroactive probes is performed using electroanalytical techniques and FTIR and UV/vis spectroscopies. Steady-state voltammetry and chronoamperometry at platinum disk microelectrodes are used to measure the diffusion coefficient of Fc(MeOH)2 in gels under a wide range of experimental conditions. Similar diffusion coefficients for Fc(MeOH)2 in NIPA-AA gels are obtained by either electroanalytical technique at temperatures lower than 20 degrees C. The uncertainty in the Fc(MeOH)2 concentration in the gels, resulting from the discontinuous volume change transition, necessitated the use of concentration-independent chronoamperometric data (i.e. the chronoamperometric response divided by the steady-state current obtained at sufficiently long times) to obtain reliable diffusion coefficient values for Fc(MeOH)2. For temperatures above the volume phase transition, changes of concentration of Fc(MeOH)2 are detected in a copolymeric collapsed phase.

Journal Article↗
PubMedDate not supplied

Immobilization of potato tuber lipoxygenase on oxirane acrylic beads.

In this study, lipoxygenase from potato tuber has been purified by a method involving hydrophobic chromatography and the purified enzyme immobilized by covalent coupling to oxirane acrylic beads. The immobilized lipoxygenase exhibited increased long-term stability without a significant modification of the kinetic parameters. The comparative study on the effects of inhibitors such as dithizone, NDGA, phenidone, and beta-mercaptoethanol on the free and immobilized enzyme highlighted the importance of the lipoxygenase--support interaction, concluding that the immobilization process could cause the protection of the iron atom in the enzyme. The enzymatic specificity was maintained for the immobilized lipoxygenase, and their stability increased as compared to the free enzyme, making if feasible to use the enzyme in a multistep reaction to produce large quantities of leukotriene A4 or other related compounds of interest in the chemical industry and medicine.

Arachidonate 5-Lipoxygenase↗
PubMed2005

Knotted network consisting of 3-threads and a zwitterionic one-dimensional polymorphs of trans-3-(3-pyridyl)acrylate of cobalt and nickel, MII(C8H6NO2)2(H2O)2.

We present the hydrothermal synthesis, characterization (IR, DT-TGA), single-crystal structures, and magnetic properties of two polymorphs of trans-3(3-pyridyl)acrylate of cobalt(II) and of nickel(II), M(II)(C(8)H(6)NO(2))(2)(H(2)O)(2). Hydrothermal reaction at 120 or 170 degrees C results exclusively in the different polymorphs. The infrared spectra and thermogravimetric analyses of the complexes are almost similar for the two polymorphs but show a difference between cobalt and nickel in energies of the vibrational modes and in the decomposition temperatures. The crystal structures of the two polymorphs are quite different; one crystallizes in a monoclinic space group and the other in a triclinic. This major difference is due to the different stereochemistry, cis or trans, of the coordination at the metal sites. When it is trans-MN(2)O(4), it results in the monoclinic cell consisting of a 3D-network of metals bridged by the ligands through single bonds (M-N and M-O). There is threading of three sublattices up to 2a x 4b x 2c, at which point the three sublattices are knotted into one infinite framework. When it is cis-MN(2)O(4), it results in the triclinic cell and consists of Zwitterionic linear chains of metals bridged by one single ligand via the pyridine and a bidentate carboxylate group and the other ligand is bonded only via the pyridine while its carboxylate end is free. All four compounds are paramagnetic with Weiss constants suggesting weak interactions.

Journal Article↗
PubMed2002

Mechanism of asymmetric hydrogenation of alpha-(acylamino)acrylic esters catalyzed by BINAP-ruthenium(II) diacetate.

The mechanism of asymmetric hydrogenation of alpha-(acylamino)acrylic esters with Ru(CH(3)COO)(2)[(S)-binap] (BINAP = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl), giving the S saturated products in >90% ee, has been investigated by means of a kinetic study, deuterium labeling experiments, isotope effect measurements, and NMR and X-ray analysis of certain Ru complexes. The hydrogenation in methanol under a low H2 pressure proceeds via a monohydride-unsaturate mechanism that involves the initial RuH formation followed by a reaction with an olefinic substrate. The migratory insertion in the enamide-RuH chelate complex occurs reversibly and endergonically in an exo manner, giving a five-membered metallacycle intermediate. The cleavage of the Ru-C bond is achieved with either H2 (major) or CH3OH (minor). Both of the pathways result in overall cis hydrogenation products. The hydrogen at C3 is mainly from an H2 molecule, and the C2 hydrogen is from another H2 or protic CH3OH. The major S and minor R enantiomers are produced via the same mechanism involving diastereomeric intermediates. The turnover rate is limited by the step of hydrogenolysis of a half-hydrogenated metallacyclic intermediate. The participation of two different hydrogen donor molecules is in contrast to the pairwise dihydrogenation using a single H2 molecule in the RhI-catalyzed reaction which occurs via a dihydride mechanism. In addition, the sense of asymmetric induction is opposite to that observed with S-BINAP-RhI catalysts. The origin of this phenomenon is interpreted in terms of stereocomplementary models of the enamide/metal chelate complexes. A series of model stoichiometric reactions mimicking the catalytic steps has indicated that most NMR-observable Ru complexes are not directly involved in the catalytic hydrogenation but are reservoirs of real catalytic complexes or even side products that retard the reaction.

Journal Article↗
PubMed2003

Role of charge-transfer configurations on the addition reaction of aminoalkyl radicals onto acrylate double bonds.

The major factors affecting the reactivity of the important class of aminoalkyl radicals toward the addition reaction onto acrylate double bonds were studied. The rate constants of interaction, directly measured by using laser-induced photoacoustic calorimetry, range from 2.5 x 10(7) to 4.5 x 10(7) M(-)(1) s(-)(1). The reactivity of these radicals was compared to that of alkyl radicals. Calculations show that the reaction enthalpy is not the driving factor. Molecular orbital calculations of the transition states clearly demonstrated the large participation of charge-transfer configurations relative to nonpolar configurations, leading to a decrease of the barrier height. Moreover a quite good correlation is found when plotting the charge-transfer character in the transition state against the ionization potential. The roles of the different factors governing the reactivity of these species were elucidated.

Journal Article↗