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At least 91 records · Page 5Linked to original sources

PubMed2005

Chronic inflammation from polycarbonate motility peg inhibits osteogenesis in a human hydroxyapatite orbital implant.

The histologic findings of a pegged hydroxyapatite orbital implant removed due to chronic inflammation and pain are described. A 44-year-old woman underwent explantation of a hydroxyapatite sphere and polycarbonate motility peg due to chronic redness, swelling, discharge, and pain. Histology revealed complete fibrovascularization of the implant, with approximately 90% ossification. No bone marrow was identified. Histologic sections revealed fibrous connective tissue at the periphery of a sclerotic bony mass with a granulomatous inflammatory infiltrate at the motility peg aperture. There were no bacterial, mycobacterial, or fungal organisms identified histologically or by culture. Consistent with previous reports, hydroxyapatite orbital implants are amenable to fibrovascular ingrowth and bony transformation. The presence of a granulomatous inflammatory reaction around the polycarbonate motility peg in this case may have prevented complete osseous transformation of the hydroxyapatite implant.

Adult↗

PubMed1974

Radioimmunoassay on polycarbonate membranes: a sensitive and simplified method for the detection and quantitation of antibody.

A new radioimmunoassay technique is described in which a sampling manifold and polycarbonate filter membranes are used. Antigen-antibody reactions take place on the membranes. The manifold permits the simultaneous running of 30 samples and a rapid wash technique in which the washing solution is introduced into the manifold wells and suctioned off from below. The polycarbonate membrane offers a distinct advantage over the cellulose acetate in that nonspecific protein adsorption is substantially reduced. Antigens employed are whole bacteria or soluble antigen coupled to Sepharose beads and are layered over the membrane surface. A radiolabeled antibody is used to measure the primary antigen-antibody interaction. The sensitivity of the procedure is equal to that of fluorescent antibody tests.

Acetates↗

PubMedDate not supplied

Comparative development of SIRC rabbit corneal cells grown on polycarbonate- and polyester-based filters.

Statens Seruminstitut Rabbit Cornea (SIRC) cells were grown on sterile polycarbonate- and polyester-based filter inserts to evaluate the feasibility of substituting the polyester-based filter inserts for use in a previously developed permeability model. The two filter types were compared for differences in cellular growth rate and morphological changes following days 3, 7 and 10 in culture. There were no significant differences in the number of cell layers formed on any day examined. The numbers of cell layers formed with the polycarbonate-based filter inserts were 1.75 +/- 0.09, 2.53 +/- 0.14 and 2.93 +/- 0.16, for days 3, 7 and 10, respectively. The numbers of cell layers formed with the polyester-based filter inserts were 1.79 +/- 0.07, 2.23 +/- 0.11 and 2.90 +/- 0.13, for days 3, 7 and 10, respectively. The SIRC cells had a similar comparative morphology on each of the above days. Active cell growth was seen on each day with signs of maturation evident by day 7 in culture. The polyester-based filter inserts can be substituted in the previously established permeability assay without alteration of morphology or rate of growth, thus allowing confirmation of cell confluency prior to use in the permeability assay. It will also allow for photographic documentation of cell injury prior to recovery studies, without necessitating the preparation of extra samples for fixation at the time of initial injury. Future studies will be required to determine if there will be any alteration in the rate of permeability with a previously tested standard, before adoption of the new filter.

Animals↗

PubMed1986

The polycarbonate hemodialysis membrane: neutrophil, platelet, complement and chemiluminescence kinetics during first and second use.

In a clinical comparative cross-over study of 12 chronically hemodialyzed patients, the polycarbonate hemodialyzer membrane disclosed the following features: A drop in neutrophil count to 45 +/- 11% predialysis values occurred 15 min after the start of dialysis. Plasmatic C3d increased at the initiation of dialysis simultaneously with the nadir of neutropenia but also towards the end of dialysis when neutrophil count was normal. An inhibition of chemiluminescence of neutrophils isolated 5 and 15 min after the start of dialysis was noted. Reuse of the membrane induced during the second use a significant aggravation of neutropenia (36 +/- 23% at 15 min), a drop in platelet count (91 +/- 10% at 15 min) and a return to normal of chemiluminescence. When compared to the results observed with cuprophane and polyacrilonitrile membranes in the sam patients, the polycarbonate membrane seems to possess intermediate biocompatibility properties.

Acrylic Resins↗

PubMed1992

Interleukin-8 and neutrophil leucocytes: adhesion, spreading, polarisation, random motility, chemotaxis and deactivation in assays using 'sparse-pore' polycarbonate (nuclepore) membranes in the Boyden chamber.

Adhesion, spreading, chemotaxis and deactivation of chemotactic responses of separated human peripheral blood neutrophil leucocytes under the influence of interleukin-8 (IL-8) were tested using a previously described Boyden chamber-type method involving 'sparse-pore' polycarbonate (Nuclepore) filtration membrane. The random motilities of neutrophils in similar concentrations of IL-8 were tested using corresponding chambers with polycarbonate membranes of standard pore densities. In addition, polarisation of neutrophils in suspension in various concentrations of IL-8, and the possibility of deactivation of this polarisation response by IL-8 itself or by N-formyl-methionyl-leucyl-phenylalanine (FMLP) were examined. Neutrophils exhibited maximum chemotaxis to IL-8 in a concentration of 100 ng/ml, and to a degree which was similar to the maximum response to FMLP (10(-7) M). This chemotactic response to IL-8 was markedly reduced by pretreatment of the cells with either 100 ng/ml IL-8 (deactivation) or 10(-7) M FMLP (cross-deactivation). On the other hand, the chemotactic response of the neutrophils to FMLP was reduced by pretreatment with FMLP but was not deactivated by pretreatment with IL-8 (i.e. deactivation but not cross-deactivation). Neutrophils in suspension were maximally polarised by 100 ng/ml IL-8, and to lesser degrees by 1, 10 and 1,000 ng/ml IL-8. The detailed morphology of the polar cells was not distinguishable from that induced by 10(-8) M FMLP. Pretreatment of the cells with either IL-8 or FMLP resulted in no reduction of polarisation in response to subsequent exposure to either agent (i.e. neither deactivation nor cross-deactivation).(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Adhesion↗

PubMed2002

Influence of surface morphology and chemistry on the enzyme catalyzed biodegradation of polycarbonate-urethanes.

Polycarbonate based polyurethanes were synthesized with varying hard segment content as well as hard segment chemistry based on three different diisocyanates,1,6-hexane diisocyanate (HDI), 4.4'-methylene bisphenyl diisocyanate (MDI) and 4,4-methylene biscyclohexyl diisocyanate (HMDI). The surface chemistry and morphology were characterized using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The polymers were incubated with cholesterol esterase (CE) in a phosphate buffer solution at 37 degrees C over 10 weeks. XPS results showed that the surface chemistry changed as the size and chemistry of the hard segment varied within the materials. AFM images exhibited distinctive surface morphologies for all polymers, and this was particularly apparent with changes in the hard segment chemistry. The results showed that the surface of HDI polymers consisted of relatively stiff rod-like structures, which corresponded to the soft segment domains. Polymers with a higher HDI content exhibited a dense top layer containing a relatively higher hard segment component, covering the sub-surface matrix of rod like structures. The MDI based polyurethane had large aggregates on its top surface, which corresponded to the aggregation of harder components. The HMDI based polycarbonate-urethane presented a relatively homogeneous surface where no phase separation could be detected. The relative differences in hard and soft segment content in their surface structure was supported by XPS findings. The analysis of the biodegradation results, concluded that enzyme catalyzed biodegradation within these materials was initiated in amorphous soft segment regions located in the region of the interface between hard and soft segments. A higher hard segment content at the surface contributed significantly to an increase in biostability. The findings provided an enhanced understanding for the role of surface molecular structure in the enzyme catalyzed biodegradation of polyurethanes.

Biocompatible Materials↗

PubMed1996

Trophoblast cell monolayers on polycarbonate membranes as a preparative approach for studies of transcellular transport.

To investigate mechanisms of transplacental transfer, the trophoblast-derived cells were cultured on a polycarbonate membrane with 0.4 micron pores and medium on each side. The cells could form microscopically continuous cellular sheets over Transwell polycarbonate membranes. Permeability studies suggested however that the cell layer possesses a significant leak that must be controlled for. The results indicate that the transfer of substances through lateral intercellular spaces must be considered when studies of trans-trophoblast transfer are performed using cell monolayers.

Biological Transport↗

PubMed1979

Evaluation of new membranes for hemodialysis: preliminary studies with a polycarbonate membrane.

A synthetic polycarbonate (PC) membrane supplied by C.R. Bard Inc. was assessed as to its clinical usefulness and suitability to regular use with artificial kidney. The permeability of the PC membrane to 11 solutes of increasing molecular volumes (Na+, Ca++, K+, Cl-, HPO4-, urea, creatinine, uric acid, glucose, BSP, cyanocobalamine) was measured in vitro by rotating dialysis cells, as compared to that of Cuprophan PT 150. The evaluation of the PC membrane in vivo was carried out during a regular hemodialytic treatment in 5 patients using a Kiil dialyzer. The dialysance of 6 solutes (HPO4-, urea, creatinine, uric acid, hypaque, cyanocobalamine) across the PC membrane was measured at 200 ml/min blood flow rate. Both in vitro and in vivo the PC membrane showed permeability and dialysance coefficients to small molecules approximately the same than standard PT 150; the ultrafiltration rate of the PC membrane was also superimposable to that of PT 150. On the contrary, larger molecules were removed much more efficiently by the polycarbonate membrane than by PT 150. These data suggest that the membrane evaluated in this study possesses some peculiar features which could possibly result in an improvement of the quality of regular hemodialysis.

Animals↗

PubMed1982

Improved phosphate clearances with polycarbonate membranes.

Clearance studies of urea, creatinine and inorganic phosphate have been carried out using polycarbonate dialysers on 20 occasions in two patients undergoing routine maintenance haemodialysis. Clearances were calculated using plasma concentrations and both measured blood flow and calculated plasma flow. Urea and creatinine clearances were comparable to those obtained with cellulose-based dialysers, but phosphate clearances were relatively increased, averaging over 70% of urea clearances. All clearances were reduced as TMP values increased, a feature at variance with the usual situation with cellulose membranes. Polycarbonate dialysers have the advantage of higher relative phosphate clearances in addition to the other advantages claimed for them.

Cellulose↗

PubMed1999

Amination of polycarbonate surface and its application for cell attachment.

The polycarbonate sheet was modified with ammonia gaseous plasma and characterized by the contact angle measurement and ESCA analysis. The contact angles decreased significantly from 77 degrees to about 20 degrees-40 degrees, indicate that the polycarbonate sheet become more hydrophilic after plasma treatment. The ESCA analysis results showed that the hydrophilicity was mainly derived from the amino groups on the modified surface. In this study, a flow-chamber system was also constructed to evaluate the 3T3 fibroblast cells attachment phenomena on these modified sheets. Before the experimental run, the parameters of inoculated cell number and cell passage were examined previously. The results revealed that these two parameters are independent in shear experiment. And besides, 3-hours plating time has the better adhering fraction. The experimental results showed that the 3T3 fibroblast cells adhesion strength increased significantly on the plasma modified sheet.

3T3 Cells↗

PubMed1999

Enzyme-catalyzed polycondensation reactions for the synthesis of aromatic polycarbonates and polyesters.

Aromatic polymers are widely used in products ranging from optical lenses to milk bottles because of their strength, thermal durability, and high glass transition temperatures. All of the commonly used routes employed to generate aromatic polycarbonates and polyesters generate large amounts of waste as by-products and require high energy input. For these reasons, alternate routes to aromatic polymers which involve either less energy input or less waste generation are being investigated. One such route may be enzymatic. Herein we describe enzyme-catalyzed AA-BB condensation polymerizations to form aromatic polycarbonates and polyesters with six different aromatic diols and molecular weights of up to 5,200 Daltons are generated. In addition, for reactions with benzenedimethanol the enzyme exhibits regioselectivity for parahydroxyls over meta- and orthohydroxyls.

Biotechnology↗

PubMed2000

[Cracks of polycarbonate three-way stopcock are caused by fat emulsion not by propofol].

We found fine cracks in a three-way stopcock after continuous infusion of propofol (Diprivan, Astra-Zeneca, UK). In this paper the possible mechanism was investigated. At first we checked various three-way stopcocks of various manufactures, such as JMS, Terumo, Nipro and Top. All of them were made with polycarbonate. Fine cracks were observed in all stopcocks after 6 hours of liquid contact with propofol between the three-way stopcock and male connector. Based on the mechanical stretch tests of polycarbonate plastic strips with saline, 10% fat emulsion (Intralipid, Otsuka, Japan), or 1% propofol in 10% fat emulsion (Diprivan), significantly greater cracks were observed in both fat group and propofol group, compared with the saline group. But there was no significant difference in cracks between fat and propofol groups. The size of crack increased in a time and strength dependent manner. We conclude that the cause of cracks in three-way stopcock is fat emulsion as a vehicle of propofol not propofol itself.

Anesthesiology↗

PubMed1975

Clinical use of NISR 440 polycarbonate membrane for hemodialysis.

1. In order to accredit the NISR440 Polycarbonate Membrane for clinical studies, the following was accomplished and/or established: a. Casting and synthesis were increased from the laboratory level to production scale. b. Quality control of permeabilities and physical properties was within +/- 5%, from membrane lot to lot and within the same roll. c. The target properties of the Artificial Kidney Program (NIH) were reached(7): 1) Middle M. W. solute permeability of marked molecules was established by 3 different laboratories and averaged: Vitamin B12 - 296 x Cuprophan¿; Inulin 3.6 x Cuprophan¿; Bacitracin 2.94 x Cuprophan¿. 2) Low M. W. species permeabilities were approximately the same as Cuprophan¿, to avoid a depletion syndrome. 3) Hydraulic permeability was essentially the same as Cuprophan¿ (UF rate 1.25 to 2.0 x Cuprophan¿) to avoid dehydration and hypotension. 4) Burst strength was 1.5 to 2.0 x Cuprophan¿. d. Toxicology studies were all negative in spot and in serial lot testing. e. Non-thrombogenicity tests (Lindholm test) were up to 36.6% better than Cuprophan¿. f. No protein adsorption was found. g. The membrane could be produced in the wet and dry state with the same permeability and physical properties. 2. In an earlier clinical study at USC, it was established that: a. There were no toxic effects manifested in patients in 25 episodic studies. b. Clearances forlow M. W. solutes and hydraulic permeabilities were, as targeted, approximately the same as Cuprophan¿. c. In 4 1/2 mos of a double blind study of 6 patients, no significant toxic effects were noted for either the patients on Cuprophan¿ or NISR 440 Polycarbonate Membrane. Two patients had an increase of hematocrit. 3. The ability to heat seal the membrane in the periphery and in channels through many layers, combined with its relative rigidity when wet, make possible clinical hemodialyzer designs approximately the size of a package of cigarettes and inexpensive to produce.

Adult↗

PubMedDate not supplied

A polycarbonate thin film technique for cytologic preparation of fluid specimens.

The use of polycarbonate membrane filters for the routine cytologic analysis of fluid specimens is well established. These filters are also currently used as integral components in some commercially available fully automated machines for the formation of monolayer cell spreads of cytologic specimens. We describe a simple manual polycarbonate filter technique for the production of similar preparations, utilizing commonly available laboratory materials, for all types of cytologic fluid specimens. The method is rapid, eliminates the cumbersome processing of whole filters, provides excellent morphologic detail and obviates the need for automated or cytocentrifugation instruments. The method is thus well suited to laboratories in which the number of fluid specimens is not large enough to justify the financial resources needed for these relatively expensive machines.

Body Fluids↗

PubMed1977

Evaluation of a polycarbonate filter for the detection of microfilaremia in dogs in central Michigan.

Several diagnostic techniques were used in determining the prevalence of microfilaremia in 479 dogs entering the holding facility for research animals at Michigan State University. The modified Knott test and cellulose filter procedures were initially applied, but persistent difficulties with the cellulose filter system prompted evaluation of the use of clear polycarbonate filters. This procedure was found to be equally as sensitive as the modified Knott test and more sensitive than the microhematocrit tube method. Microfilariae trapped on polycarbonate filters were easy to detect, and there were no problems with clogging of the filter pores. Losses of up to 3.5% of the microfilariae occurred with 8-micron pore size filters, but no more than 1% passed through 5-micron pore size filters. Identification of microfilariae was based on size and shape of the parasites. In questionable cases, the diagnosis was confirmed by means of the histochemical test for acid phosphatase distribution. Satisfactory results were obtained when the latter test was applied to microfilariae of Dirofilaria immitis trapped and fixed on filters. Twenty blood samples in the surgery (4.2%) contained microfilariae, all of which were classified as D imitis.

Animals↗

PubMed1993

Concentration and temperature dependence of diluent dynamics studied by line shape experiments on a phosphate ester in polycarbonate.

31P Hahn spin echo line shape and proton line shape experiments are reported on bisphenol A polycarbonate (BPAPC)-tris(2-ethylehexyl)phosphate (TOP) systems to study the concentration and temperature dependence of the local dynamics. In an earlier 31P line shape study a lattice model was presented as a framework to interpret the plasticization and antiplasticization behavior of the diluent based on a fractional population given by the type of nearest neighbor contacts in the mixed polymer-diluent glass. In this study, 31P spin echo line shapes of BPAPC, with 5%, 10% and 15% TOP, which monitor the diluent dynamics, at different temperatures and echo delay times are simulated in terms of fast- and slow-moving components, and the resulting fractional populations are compared with that predicted by the lattice model. Comparisons with the lattice model calculations are also made in the simulation of the 1H line shapes on BPAPC with 5% and 10% TOP, which probes both the polymer and diluent dynamics, and on BPAPC with 5% and 10% perdeuterated trioctylphosphate (DTOP), which detects only the polymer motion. Fairly good line shape simulations and agreement between the lattice model and the fitting results at low diluent concentrations are obtained in all cases. Restricted cone motion best describes the slow-moving component in the 31P line shape fittings. For the fast component, rotational Brownian diffusion with a distribution of correlation times corresponding to a stretched exponential function is used. An activation energy Ea of 56 kJ/mol and an exponent alpha of 0.7 for the fractional exponential correlation function are obtained and used to calculate the mechanical loss peak which was compared with the experimental loss data. The plateau character of the fractional population as a function of temperature can also be interpreted and understood in terms of the lattice model.

Benzhydryl Compounds↗

PubMed1997

Chemical stability of polyether urethanes versus polycarbonate urethanes.

The relative chemical stability of two commercially available polyurethanes-Pellethane, currently used in biomedical devices, and Corethane, considered as a potential biomaterial-was investigated following aging protocols in hydrolytic and oxidative conditions (HOC, water, hydrogen peroxide, and nitric acid) and in physiological media (PHM, phosphate buffer, lipid dispersion, and bile from human donors). The chemical modifications induced on these polymers were characterized using differential scanning calorimetry (DSC), gel permeation chromatography (GPC), and Fourier transform infrared spectroscopy (FTIR). With the exception of nitric acid, all of the aging media promoted a mild hydrolytic reaction leading to a slight molecular weight loss in both polymers. When aged in water and hydrogen peroxide, Pellethane experienced structural modifications through microdomain phase separation along with an increase of the order within the soft-hard segment domains. The incubation of Pellethane in nitric acid also resulted in an important decrease of the melting temperature of its hard segments with chain scission mechanisms. Moreover, incubation in PHM led to an increase of the order within shorter hard-segment domains. FTIR data revealed the presence of aliphatic amide molecules used as additives on the Pellethane's surface. The incubation of Corethane under the same conditions promoted an almost uniform molecular reorganization through a phase separation between the hard and soft segments as well as an increase of the short-range order within the hard-segment domains. Incubation of this polymer in nitric acid also resulted in a chain scission process that was less pronounced than that measured for the Pellethane samples. Finally, lipid adsorption occurred on the Corethane sample incubated in bile for 120 days. Overall data indicate that polycarbonate urethane presents a greater chemical stability than does polyetherurethane.

Calorimetry, Differential Scanning↗

PubMed2001

Elution of bisphenol-A from hemodialyzers consisting of polycarbonate and polysulfone resins.

This study deals with bisphenol-A (BPA) analysis of the BPA-derived polymer pellets, polycarbonate (PC) and polysulfone (PS), and in the hemodialyzer casings made of PC, and the leaching of BPA from commercially available hemodialyzers into water and bovine serum, using HPLC, GC-MS, and LC-MS analyses, and NMR spectroscopy. Total contents of BPA in polymer pellets of each resin were 4.0 and 7.2 microg/g (PC) and 34.5 microg/g (PS). Amounts of BPA released from hemodialyzer PC casings lacking PS hollow-fiber were 11.7 and 13.7 ng/casing by water extraction, and 296 and 345 ng/casing by methanol extraction. On the other hand, BPA of 3.78 to 141.8 ng/module was recovered using water circulation of hemodialyzers, and 140.7 to 2,090 ng/module was detected when bovine serum was used as a circulation solvent. The elution profiles using various concentrations of ethanol/water mixtures indicated that a 17.2% (v/v) ethanol solution rather than bovine serum can be used as an extraction solvent, where a similar amount of BPA as with bovine serum circulation was eluted from the hemodialyzer. Thus, this solvent may be useful for evaluating BPA elution from hemodialyers under similar conditions to medical use.

Animals↗