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At least 325 records · Page 18Linked to original sources
PubMed1981

The use of polystyrene microcarriers to prepare cell monolayers for transmission electron microscopy.

A simple method is described, using polystyrene microcarrier beads, that allows cell monolayers to be prepared without distortion for transmission electron microscopy. Cells cultured on polystyrene beads (Biosilon R, Nunc, Kamstrup, Denmark) are held in an agar matrix. Before embedding, the beads are dissolved in 1,2-epoxypropane. The technique increased the number of observable cells, when compared to preparations of planar monolayers, and there is good preservation of morphological detail.

Cell Line↗
PubMed1995

Mosquito control in Dar es Salaam. II. Impact of expanded polystyrene beads and pyriproxyfen treatment of breeding sites on Culex quinquefasciatus densities.

In two contrasting areas of Dar es Salaam (Ilala and Mikocheni) all enclosed breeding sites of Culex quinquefasciatus, such as latrines and septic tanks, were treated with a floating layer of expanded polystyrene beads. 7 months later checks in both study areas revealed only one site (from which the polystyrene had been removed during emptying) containing immature stages of Cx quinquefasciatus. Open breeding sites such as areas of flooded land and blocked drains were treated with pyriproxyfen (an insect growth regulator) at a concentration of 0.1 ppm. Emergence of Cx quinquefasciatus adults from these sites was inhibited for 4 weeks during the rainy season and for up to 11 weeks during the dry season. The problem of mosquito breeding sites caused by bathroom sullage water was addressed through a combination of health education and indirect pressure from the Urban Malaria Control Project (UMCP) via local community leaders. Households responsible for these sites were encouraged to eliminate them by diverting the water into an enclosed drainage structure, usually a pit latrine. After two weekly visits 64.7% of households had complied and 93.4% had complied after five visits. 5 months later, only 15.7% had reverted to allowing sullage water to collect into puddles. Densities of Cx quinquefasciatus adults dropped by 76.7% in Mikocheni and by 46.2% in Ilala following intervention, but increased by 84.9% and 25.6% in two untreated comparison areas. The reasons for differential success of the combined interventions in the two treated areas are discussed.

Animals↗
PubMed1993

Modification of the complement binding properties of polystyrene: effects of end-point heparin attachment.

In recent years, conjugation of heparin to biomaterials has been shown to improve its biocompatibility. The purpose of the present work was to compare complement activation and binding of C3 to unmodified and heparin-treated polystyrene surfaces of microtitre plates. When polystyrene was incubated with human serum, C3 was deposited on the surface by both adsorption and binding dependent on activation of the classical (CPW) and alternative (APW) pathways. After end-point attachment of heparin, significant C3 deposition, although at reduced levels, occurred only by CPW-mediated mechanisms, while adsorption and APW-mediated binding were strongly reduced. Generally, the modified surface bound lower amounts of protein, e.g. serum albumin and IgG, than the unmodified. By contrast, it had increased affinity for C1q which leads to binding of C1 and activation of complement via the CPW. Nevertheless, the net effect of the surface modification on the complement reaction was an overall reduction of C3 binding due to obliteration of APW. This can be related to an enhanced factor H/I-dependent down-regulation of C3b and to the lowered protein-adsorbing property of the surface, both of which have inhibitory effects on APW and on the C3 shunt-dependent activation of the complement system.

Complement Activation↗
PubMed1998

Synthesis of thioredoxin partial sequences on 1,6-hexanediol diacrylate (HDODA)-cross-linked polystyrene resin.

The continued and rapid discoveries of new peptides with interesting biological functions have created an unprecedented demand for the chemical synthesis of peptides required for structure-function correlations. Several strategic improvements have been suggested and tested to meet the demand for peptides in high purity and quantity. This article describes the synthesis of three partial sequences of thioredoxin, a naturally occurring sulfur-reducing protein containing 108 amino acid residues, on a newly developed flexible, cross-linked polystyrene support (2% polystyrene cross-linked with 1,6-hexanediol diacrylate) using the standard solid-phase methodology. The protected peptides were cleaved from the polymeric support by trifluoroacetic acid and purified by chromatography. The free peptides were shown to be homogeneous by high-performance liquid chromatography and were characterized by amino acid analysis and circular dichroism. The circular dichroism measurement revealed that the peptides possess a helical conformation. From the yield and purity of the peptides obtained, it was inferred that the favorable swelling and solvation characteristics of the support facilitated effective synthesis.

Acrylates↗
PubMed1994

Anisotropy measurements of a high dose rate Ir-192 source in air and in polystyrene.

Anisotropy measurements in air and in polystyrene were performed for a Nucletron microSelectron 10 Ci Ir-192 source. TLD rods of similar sensitivity (+/- 3%) were placed on a semicircle around the source center which had been precisely localized by either radiographic means or direct measurement. The anisotropy, expressed as a ratio of TLD reading at a given angle relative to the longitudinal source axis, over the reading at 90 degrees, was measured for distances between 1 and 10 cm from the source center. For both media, a marked anisotropy of the high dose rate source was found. In air, there is no detectable variation in anisotropy with distance up to 10 cm from the source. In polystyrene, however, the anisotropy becomes less pronounced with increasing distance due to scatter. For both media, no difference, within the estimated experimental accuracy of +/- 5%, was found between three consecutive sources installed by the vendor.

Air↗
PubMed1995

White polystyrene as a substitute for water in high energy photon dosimetry.

White polystyrene (C8H8 with 2 wt. % to TiO2) has been compared to water using photon beams with nominal accelerating potential of 4 MV, 6 MV, 15 MV and 25 MV. The absolute reading and hence the measured absorbed dose is found to be up to 3% lower in white polystyrene which can be taken into account by using a correction factor. From these data differences in relative measurements (TMR or percentage depth dose) can be calculated showing differences of less than 0.7% normalized to maximum dose. Since the correction factor shows a dependence on photon energy and field size the use of a common scaling factor is not possible. The effect on photon dosimetry is discussed.

Biophysical Phenomena↗
PubMed1987

Antimicrobial activity of tertiary amine covalently bonded to a polystyrene fiber.

Tertiary amine was covalently bonded to a polystyrene fiber and examined for antibacterial activity. The tertiary amine covalently bonded to a polystyrene fiber (TAF) showed a high antimicrobial activity against Escherichia coli. TAF exhibited a stronger antibacterial activity against gram-negative bacteria (E. coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Salmonella typhimurium, and Serratia marcescens) than against gram-positive bacteria (Staphylococcus aureus and Streptococcus faecalis) or Candida albicans. This activity against E. coli was accentuated by 0.1% deoxycholate or 10 mg of actinomycin D per ml, to which E. coli is normally not susceptible. This implies that TAF causes an increase of the bacterial outer membrane permeability. On the other hand, the antimicrobial activity was inhibited by adding Mg2+ or by lowering the pH. This suggest an electrostatic interaction between the bacterial cell wall and TAF. Scanning electron microscopy showed that E. coli cells were initially attached to TAF, with many projections on the cell surface, but then were apparently lysed after contact for 4 h. Taken together, these results imply that bacteria initially interact with TAF by an electrostatic force between the anionic bacterial outer membrane and the cationic tertiary amine residues of TAF and that longer contact with TAF damages the bacterial outer membrane structure and increases its permeability.

Anti-Bacterial Agents↗
PubMed1988

Specific and nonspecific inhibition of adhesion of oral actinomyces and streptococci to erythrocytes and polystyrene by caseinoglycopeptide derivatives.

Various caseinoglycopeptide derivatives prepared from mammalian milk were evaluated as inhibitors of hemagglutinations mediated by Actinomyces viscosus Ny1, Streptococcus sanguis OMZ9, and, for comparative purposes, plant lectins from Arachis hypogaea and Bauhinia purpurea. It was found that recognition of the beta-D-galactose-(1----3)-2-acetamido-2-deoxy-D-galactose carbohydrate chain by Actinomyces viscosus Ny1 organisms and Arachis hypogaea and B. purpurea agglutinins had similar structural requirements; in all cases, the desialylated bovine caseinoglycomacropeptide, on which several units of the above mentioned disaccharide are clustered, behaved as the most potent hemagglutination inhibitor. By contrast, none of the preparations tested inhibited erythrocyte agglutination by S. sanguis OMZ9. Thus, the desialylated bovine caseinoglycomacropeptide acts as a potent and specific inhibitor of oral Actinomyces adhesion to cell membranes (a soft surface) and could be used as a probe for the study of recognition mechanisms mediated by Actinomyces galactose-binding lectins. During the present study, both native and desialylated variants of the same bovine glycomacropeptide also totally prevented the adhesion of Actinomyces viscosus Ny1, S. sanguis OMZ9, and S. mutans OMZ176 to polystyrene surfaces. Comparative evaluations of various structurally different compounds gave the following results. Neither mono- nor disaccharides related to caseinoglycopeptide carbohydrates prevented adhesion; highly positively or negatively charged polypeptides and polysaccharides were either not or only moderately active. Besides these glycomacropeptides, an inhibitory activity was also exhibited by other mucin-type glycoproteins carrying short O-linked carbohydrate chains (including bovine submaxillary mucin), polyethylene glycol, and bovine serum albumin. Consequently, caseinoglycopeptide prevention of oral bacterial adhesion to polystyrene tubes (a hard surface) takes place with no species specificity and can be compared to nonspecific inhibition exhibited by various polymers with very different structural characteristics.

Actinomyces↗
PubMed1978

Microbial degradation of [C14C]polystyrene and 1,3-diphenylbutane.

Microbial degradation of [beta-14C]polystyrene and 1,3-diphenylbutane, a compound structurally representing the smallest repeating unit of styrene (dimer), was investigated in soil and liquid enrichment cultures. Degradation rates in soil, as determined by 14CO2 evolution from applied [14C]polystyrene, varied from 1.5 to 3.0% for a 4-month period. Although relatively low, these percentages were 15 to 30 times greater than values previously reported. Enrichment cultures, containing 1,3-diphenylbutane as the only carbon souce, were used to determine the mechanisms of microbial oxidation of the polymer chain ends. Metabolism of 1,3-diphenylbutane appeared to involve the attack by a monooxygenease to form 2-phenyl-4-hydroxyphenylbutane followed by a further oxidation and subsequent fission of the benzene ring to yield 4-phenylvaleric acid and an unidentified 5-carbon fragment via the classic meta-fission pathway. Phenylacetic acid was probably formed from 4-phenylvaleric acid by subsequent beta-oxidation of the side chain, methyl-oxidation and decarboxylation. An initial examination of the population of microorganisms in the diphenylbutane enrichment cultures indicated that these oxidative reactions are carried out by common soil microorganism of the genera Bacillus, Pseudomonas, Micrococcus, and Nocardia.

Bacteria↗
PubMed2005

Absence of NF-kappaB activation by a new polystyrene-type adsorbent designed for hemoperfusion.

AIM: The aim of the study was to evaluate biocompatibility of anew polystyrene-type adsorbent (BetaSorb) designed for hemoperfusion, using second-level biomolecular analyses. The device has recently been developed to enhance beta2-microglobulin removal during hemodialysis. Molecular structure and chemical modifications of the surface beads of this cartridge should prevent exposure of dense hydrophobic surface sites to proteins, and avoid the major drawbacks of previous polystyrene-type adsorbent materials. METHODS: Whole blood of healthy donors was incubated in sterile minicolumns packed with BetaSorb Cuprophan, Hemophan, polysulfone and cellulose acetate. In parallel experiments, whole blood was recirculated for 180 min in a sham dialysis circuit equipped with the study sorbent or Hemophan or polysulfone. Biocompatibility was assessed by means of new biomolecular approaches focused on nuclear factor kappaB (NF-kappaB) activation (assessed by electrophoretic mobility shift assay), TNF-alpha and IL-1beta gene expression (evaluated by real-time PCR), TNF-alpha and IL-1beta production (measured by Western blot assay and ELISA), nitric oxide (NO) generation (detected by electron paramagnetic resonance), free oxygen radical production (by chemiluminescence in a biological assay) and the generation of the complement breakdown product C3d. RESULTS: In coincubation experiments, 5-min contact with any dialysis device, but BetaSorb, was enough to induce activation of NF-kappaB. The amount of TNF-alpha precursor form was found to increase after 5 min of exposure to each tested polymer, but no traces of mature forms of TNF-alpha or IL-1beta were detected in in vitro experimental conditions using healthy blood. NO and free oxygen radical generation were significantly lower in blood samples exposed to BetaSorb than in control dialysis devices. C3d levels were found to be increased with Hemophan, unaffected by polysulfone, and remarkably decreased with the BetaSorb device. In the sham hemodialysis experiments, NF-kappaB activation and C3d and NO profiles were similar to direct incubation experiments. Compared to basal levels, quantitation of TNF-alpha and IL-1beta mRNA revealed a 15- and 9-fold increase, respectively, in samples exposed to Hemophan for 180 min. CONCLUSIONS: The new BetaSorb device not only appears to be highly biocompatible, but shares properties that make it probably able to interfere with the activation of the inflammatory state.

Adsorption↗
PubMedDate not supplied

Unstimulated and thrombin-stimulated platelets binding to immobilized fibrinogen and fibrin on polystyrene supports.

The binding of unstimulated and thrombin-stimulated platelets was studied with immobilized fibrinogen and fibrin on polystyrene. The amount of fibrinogen bound to the polystyrene support was 2 micrograms/tube, which represents 2.35 micrograms/cm2. Immobilized fibrin was obtained by adding thrombin (5 nM) to immobilized fibrinogen. The number of unstimulated 111In-platelets bound to immobilized fibrinogen and fibrin was similar (3.2 +/- 0.3 x 10(6) and 3.1 +/- 0.4 x 10(6) platelets/micrograms fibrin(ogen), respectively). The platelet binding steadily increased. In the first 2 min, the binding rate was 0.23 x 10(6) platelets/micrograms fibrinogen/min. The binding rate then increased rapidly and saturation was reached at 10 min. The extent of the adhesion of resting platelets to immobilized fibrinogen is about one half that of the same platelets stimulated with thrombin. In thrombin-stimulated 111In-platelets, the binding to immobilized fibrinogen and fibrin is time dependent, and saturation is reached at 5 min. The early rate of thrombin-stimulated platelet binding to fibrinogen is about twice that of binding to fibrin (1.25 and 0.74 x 10(6) platelets/micrograms fibrin(ogen)/min, respectively). In saturation conditions, 1 microgram fibrinogen binds 5.7 +/- 0.6 x 10(6) thrombin-stimulated platelets and 1 microgram fibrin binds 4.6 +/- 0.5 x 10(6) thrombin-stimulated platelets. Our results indicate that the rate of platelet aggregation is faster than fibrin formation, and the rate of fibrinogen-platelet binding is faster than that of fibrin-platelet binding. Therefore, after thrombin stimulation, the binding of platelets to fibrin must be secondary to the binding of platelets to fibrinogen.

Blood Platelets↗
PubMed1985

Antibody determination against Aspergillus fumigatus by means of the enzyme-linked immunosorbent assay. II. Physico- and immunochemical properties of the polystyrene-binding components.

Polystyrene-binding antigenic components (PBC) of Aspergillus fumigatus involved in ELISA IgG antibody determinations and the corresponding numbers of precipitates found by double immunodiffusion (DID) and/or crossed immunoelectrophoresis (CIE) were studied using culture filtrate antigenic preparations fractionated by Sephadex G-100 chromatography, concanavalin A (ConA) affinity chromatography, isoelectric focusing (IEF) and TCA precipitation. It is shown that PBC, immunologically active in ELISA, are characterized by high molecular weights and ConA-binding properties. The pI values of these components were 3.5-6 and above 8. The glycoprotein and/or mucopolysaccharide nature is suggested by the binding to ConA and their partial resistance to trichloroacetic acid treatment. By contrast, low-molecular weight components and antigenic components that are not absorbed by ConA being active in DID and/or CIE showed less or absence of binding to the polystyrene surface.

Antibodies, Fungal↗
PubMed1994

The adsorption of F(ab')2 on positively and negatively charged polystyrene beads.

An experimental study on the adsorption of F(ab')2 molecules onto positively and negatively charged polystyrene beads is described. Adsorption isotherms at low ionic strength and different pH were performed. In all cases the adsorption isotherms showed well-defined plateau. The positively charged polystyrene beads showed a higher adsorption of F(ab')2 molecules over a range of pH. This latex sample reached a maximum adsorption at pH 7, whereas the negatively charged sample showed a maximum at pH 5. The isoelectric points of the F(ab')2-PS complexes were around 7.5 and 4.5 respectively. The differences in the colloidal stability of the sensitized beads are not explained by the electrophoretic mobility values. The colloidal stability of the F(ab')2-PS complexes is not only determined by the electrical charge of the complexes but also by certain properties of the protein molecules, which can be closely related to the conformational changes undergone by the F(ab')2 molecules in the adsorption process on polymer surfaces.

Adsorption↗
PubMed1996

Poly(ethylene oxide)-modified carboxylated polystyrene latices--immobilization chemistry and protein adsorption.

alpha,omega-Diamino poly(ethylene oxides) (PEOs) with different molecular weights (148, 1000, and 3400) were covalently immobilized onto carboxylated polystyrene latices. The immobilization of PEO was carried out with N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide (EDC) and N-hydroxysuccinimide (NHS) in aqueous media. The reaction conditions were optimized to obtain a maximal coupling of PEO. The degree of coupling was determined by the surface concentration of amino groups. The maximal surface concentrations of amino groups were close to what is expected for a complete coverage of the surface with PEO. Adsorption of albumin from a buffer solution onto PEO-containing surfaces was about 85% less than the albumin uptake by unmodified polystyrene latices. Protein adsorption from plasma dilutions was lower on surfaces containing PEO molecules with a higher molecular weight. The reduction of the protein uptake from plasma by surfaces containing PEO-3400 molecules was only 40% compared to the adsorption to unmodified surfaces. These results indicate that plasma proteins have a low affinity for surfaces modified with PEO. However the PEO modified surfaces are by no means 'protein resistant' when exposed to plasma.

Adsorption↗
PubMed1997

Biospecific polymers: recognition of phosphorylated polystyrene derivatives by anti-DNA antibodies.

The recognition of DNA-like phosphorylated polymers by anti-DNA antibodies from the plasma of systemic lupus erythematosus patients was evidenced a few years ago by our research group. However, the radioimmunological Farr assay used for the assessment of anti-DNA antibodies adsorption was not sensitive enough to give accurate results, particularly in the case of weak levels of antibodies. An alternative method based on the use of radiolabelled species was set up in order to check the validity of previous results. Polystyrene resins with different levels in phosphate groups substitution were assessed with regard to their interactions with anti-DNA antibodies. Results show that the anti-DNA antibodies affinity is dependent on the composition of the polymers and reaches a maximum for a composition of 17.5-22.5 mol of phosphorus per 100 mol of monomeric units. This composition corresponds to the DNA-like polymer previously described. A computer-assisted method was used in order to have an insight into the structure of the active sites responsible for the DNA-like behaviour of this polymer. Numerical simulations of the phosphorylation reaction were performed using a Monte Carlo method, taking the structure predictions and the environment of the phosphorylated units into account. A number of thus generated virtual polymers correlated with the experimental results of the adsorption of anti-DNA antibodies. The chemical structure of the active site was determined by computations introducing selected hypotheses on the structure of the phosphorylated units. Moreover, since the number of active sites is directly related to the number of adsorbed anti-DNA antibodies in the experimental results, the most probable structure of the active sites is proposed and compared to a fragment of DNA. Conclusions are that the distances between the phosphate groups in the active sites of the DNA-like polymer and in the DNA fragment are similar. Optimal conditions for the purification of SLE sera by highly specific liquid chromatography using phosphorylated polystyrene resins of precise compositions as stationary phases can thus be envisaged, as well as a new method for the detection of anti-DNA antibodies.

Adsorption↗
PubMed2002

Polystyrene microspheres as a specific marker for the diagnosis of aspiration in hamsters.

The diagnosis of recurrent aspiration in young children is problematic because there is no specific gold standard test to be used. In the present work, normal saline or a suspension of white polystyrene microspheres in normal saline was instilled into hamsters' trachea (n = 42), and bronchoalveolar lavage (BAL) cytology, microsphere index (total microspheres/100 macrophages), and lung histology were followed for 90 d. Naive animals (n = 6) had no tracheal instillation. On Days 1, 3, 10, 32, 60, and 90 after tracheal instillation, animals were killed (saline-instilled animals, n = 3; and microsphere-instilled animals, n = 4), and BAL was performed. There was a marked inflammatory response in BAL on Day 1 after tracheal instillation of saline or microsphere suspension. White microspheres were clearly identified within alveolar macrophages in all studied days. Microsphere numbers showed a 50% disappearance rate of 10 d. A mild peribronchial inflammation was noted in lung histology only on Day 1 after instillation. Microspheres were not detected in extrapulmonary organs. We conclude that polystyrene microspheres instilled in hamsters' trachea can be easily identified in BAL macrophages for as long as 3 mo and could potentially be used as a sensitive, specific, and stable marker for the diagnosis of aspiration.

Animals↗
PubMed2006

In vitro and in vivo evaluation of single-unit commercial conventional tablet and sustained-release capsules compared with multiple-unit polystyrene microparticle dosage forms of Ibuprofen.

The major aims of the present study were (1) to select a multiple-unit formulation that matched the in vitro dissolution profile of single-unit sustained-release commercial capsules, (2) to compare the sustaining/controlling efficacy of the selected multiple-unit formulation with that of the single-unit commercial conventional tablet and sustained-release capsules, and (3) to determine whether an in vitro-in vivo correlation exists for single- and multiple-unit formulations. Ibuprofen (20%-60% wt/wt)-loaded multiple-unit polystyrene microparticles were prepared by an emulsion-solvent evaporation method from an aqueous system. The in vitro release profiles obtained in phosphate buffer of pH 6.8 for drug-loaded polystyrene microparticles and for commercial sustained-release capsules (Fenlong-SR, 400 mg) were compared. Since the microparticles with 30% ibuprofen load showed a release profile comparable to that of the Fenlong-SR release profile, the microparticles with this drug load were considered to be the optimized/selected formulation and, therefore, were subjected to stability study and in vivo study in human volunteers. A single-dose oral bioavailability study revealed significant differences in C(max), T(max), t(1/2a), t(1/2e), K(a), K(e), and AUC between the conventional tablet and optimized or Fenlong-SR capsule dosage forms. However, all the parameters, with the exception of K(a) along with relative bioavailability (F) and retard quotient (R(Delta)), obtained from the optimized ibuprofen-loaded microparticles were lower than that obtained from the commercial Fenlong-SR formulation. Furthermore, linear relationship obtained between the percentages dissolved and absorbed suggests a means to predict in vivo absorption by measuring in vitro dissolution.

Anti-Inflammatory Agents, Non-Steroidal↗