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At least 469 records · Page 26Linked to original sources

PubMed2001

Neurobehavioural changes and persistence of complaints in workers exposed to styrene in a polyester boat building plant: influence of exposure characteristics and microsomal epoxide hydrolase phenotype.

OBJECTIVES: To investigate neurobehavioural effects and the persistence of complaints in workers exposed to styrene relative to exposure characteristics and the enzyme microsomal epoxide hydrolase (mEH) activity. METHODS: A cross sectional study was performed in a retrospective cohort of workers of a polyester boat building plant 3 years after the main activity shut down in 1989. Workers still currently exposed to a much lower concentration of styrene in air than before (n=27) and formerly exposed workers (n=90) were compared with matched control workers (n=64). Currently and formerly exposed workers laminated 4700 and 3610 hours on average at mean exposure to styrene concentrations of 148 and 157 mg/m(3) respectively. A structured neurological anamnesis into former and present complaints, the NSC-60 questionnaire, and computer assisted neurobehavioural tests (NES) were administered. The mEH phenotype activity was measured in lymphocytes with a novel gas chromatography-mass spectroscopy (GC-MS) method. RESULTS: For the period before 1989, currently and formerly exposed workers reported more complaints than control workers which related well with the mean exposure to airborn styrene concentration (p=0.03). Most complaints disappeared after the end of exposure, although the chest, equilibrium, and somatic category scores of NSC-60 and the number of workers reporting diminished sense of smell remained increased in formerly exposed workers (p<or=0.05). Symbol-digit substitution and digit span forwards test results were worse in currently and formerly exposed workers (p<or=0.01). In the combined group of currently and formerly exposed workers, the symbol-digit substitution and colour-word vigilance results related well to duration of exposure (p<0.01 and p=0.03) and mEH phenotype activity (p=0.01 and p=0.05), whereas the digit span forwards results only showed associations of borderline significance (duration of exposure (p=0.08) and mEH phenotype activity (p=0.08)). CONCLUSION: Most subjective symptoms were reversible but some persisted after the end of exposure to styrene, whereas dysfunction of visuomotor performance and perceptual speed seemed to persist. Duration of exposure at lamination tasks and the interaction, duration of exposurexconcentration of exposure, were found to be the best predictors of worsening visuomotor and perceptual speed performances. Activity of the mEH phenotype may play a modulating part in styrene neurotoxicity. The results suggested that less than 10 years of exposure to atmospheric styrene at an average concentration of 155 mg/m(3) may result in persistent neurotoxic effects.

Adult↗

PubMed1984

Severe postural hypotension following home canoe construction from polyester resins.

On two occasions a 36-year-old man developed severe postural hypotension and neurological signs after working with a polyester resin canoe building kit in an unventilated shed. It is likely that his recurrent illness was caused by styrene intoxication. Postural hypotension secondary to styrene exposure has not previously been reported.

Hobbies↗

PubMed1988

Polyester arterial grafts impregnated with cross-linked albumin: the rate of degradation of the coating in vivo.

One of the techniques used to avoid preclotting a porous textile arterial prosthesis is to coat the graft with a layer of a bioerodible polymer. The efficacy of this treatment is dependent in part on the rate at which the polymer degrades after implantation. The focus of this study was therefore to investigate the rate of in vivo degradation of albumin-coated polyester (Dacron)-knitted vascular prostheses. Two types of cross-linked albumin were included: one using glutaraldehyde, the other using carbodiimide as the cross-linking agent. Radioactively labeled albumin-coated prostheses were implanted in the thoracic aorta and peritoneal cavity of dogs, and their rates of biodegradation in vivo were monitored over a 4-week period. The rate of biodegradation was found to depend upon the site of implantation. It occurred more rapidly in the peritoneal cavity where less than 20% of the albumin coating remained after 4 weeks in vivo in comparison to the approximately 30% in the thoracic aorta. The nature and intensity of the cellular response appeared to be related to the cytotoxic potential of the cross-linking agent. Glutaraldehyde induced an inflammatory response and a delay in healing, whereas carbodiimide caused only a mild tissue reaction.

Animals↗

PubMed1988

Characteristics of polyester arterial grafts coated with albumin: the role and importance of the cross-linking chemicals.

Preclotting is mandatory prior to implanting a knitted polyester arterial graft, unless the structure is made impermeable to blood by coating with a bioerodible material. Before achieving wide-spread clinical acceptance, the technique of impregnating with cross-linked albumin must be optimized in order to develop a graft that is immediately implantable, easy to handle and suture and has improved healing characteristics. The choice of the chemical to cross-link the albumin is of paramount importance. In this study two alternative candidates have been evaluated by using a series of tests to measure the physical properties, the morphology and the cytocompatibility of albumin-coated grafts. A carbodiimide cross-linking agent appears more promising than glutaraldehyde, since it is equally effective in producing a blood impermeable prosthesis, yet presents improved biocompatibility and provokes a less intense inflammatory response from the host.

Aldehydes↗

PubMed2000

Polymerization and surface analysis of electrically-conductive polypyrrole on surface-activated polyester fabrics for biomedical applications.

A new synthetic route is reported for the synthesis and covalent bonding of electrically conductive polypyrrole to a poly(ethylene terephthalate) fabric. It involves a three-step process including surface phosphorylation and graft polymerization from the gaseous phase. In the first step, the fibre surfaces are activated using phosphorus trichloride. Then, 1-(3-hydroxypropyl) pyrrole is introduced and grafted to the phosphorus chloride to create an ester bond between the fibres and the pyrrole. Finally, the pyrrole-grafted fibres are dipped in an aqueous FeCl3 catalyst and exposed to pyrrole monomer vapor for the final polymerization. This last step creates an electrically conductive polypyrrole layer covalently linked to the poly(ethylene terephthalate) fibres. ESCA analysis indicates a high degree of phosphorylation and grafting of the anchor molecules. Scanning electron microscopy reveals an overall smooth and uniform surface coating of polypyrrole on the polyester fibres. The use of ATR-FTIR spectroscopy is not able to distinguish between polypyrrole-coated and non-coated fabrics because of the extremely thin polypyrrole layer. Measurements of dynamic surface wetting indicated that the polypyrrole-coated fabric is more hydrophilic than the untreated control. With values for surface resistivity in the range 10(4)-10(5) ohmz/square, such polypyrrole-coated fabrics are considered attractive candidates for biomedical applications.

Biocompatible Materials↗

PubMed1994

Attempts to map the structure and degradation characteristics of aliphatic polyesters derived from lactic and glycolic acids.

During the past 5 years, important advances have been accomplished in the understanding of the fate of aliphatic polyesters derived from lactic acid (LA) and glycolic acid (GA) in aqueous media. Hydrolysis of solid LA/GA polymers is now regarded as dependent upon a diffusion-reaction mechanism. Faster central degradation, degradation-induced composition, and morphology changes are three of the most important findings which appeared to be composition-dependent as deduced from the behavior of different LA/GA polymers. An attempt is made to generalize these findings to the whole family and to elaborate a map which could be used to predict degradation characteristics of LA/GA polymers from their initial composition and morphology.

Hydrolysis↗

PubMed1995

New hydrophilic polyesters and related polymers as bioerodible polymeric matrices.

A survey is reported on our activity performed in the last few years on the preparation of new synthetic and semisynthetic polymeric materials endowed with bioerodible-biodegradable characteristics and designed for applications in the practice of controlled release of active principles of pharmaceutical and agrochemical significance. The presentation of the results will be arranged into the following sections: (1) hydroxyl containing polyesters, that comprise polymerization products based on racemic and optically active glyceric acid, or attained by polyaddition reactions among cyclic anhydrides, including also carbon dioxide, with monoglycidyl ethers of reversibly protected polyols. In this class are also presented the related polyhydroxylated systems obtained by selective grafting functional epoxides on cyclodextrins. (2) Bioerodible carboxyl containing polymeric systems as derived from the alternating copolymerization of maleic anhydride with alkyl vinyl ethers followed by partial esterification of maleic anhydride groups. (3) Linear and cross-linked functional polymers of synthetic and semisynthetic origin with hydrogel forming capability. Typical examples of their applications in the release of drugs and phytodrugs are also presented.

Biodegradation, Environmental↗

PubMed2006

Characterization and thermophysical properties of unsaturated polyester-layered silicate nanocomposites.

The thermophysical properties of unsaturated polyester (UPE) nanocomposites reinforced by organo-montmorillonite clay nanoplatelets are reported. The organo-clay nanoplatelets were sonicated in acetone for 2 hours to be dispersed in the UPE matrix. Vacuum extraction removed not only the acetone but also the styrene present in the UPE solution. The same mechanical and thermophysical properties of UPE were regained after adding the lost amount of styrene to the UPE solution. Both delaminated and intercalated clay morphologies were observed by transmission electron microscopy. It was found that the sonication process was effective to delaminate clay nanoplatelets for more homogeneous dispersion, dependent on organic chemical modifications for clay nanoplatelets. A higher storage modulus enhancement was obtained when the organo-clay nanoplatelets were delaminated and more homogeneously dispersed. The reinforcing effect of both delaminated and intercalated clay nanoplatelets was theoretically evaluated with the Halpin-Tsai equations. It was evaluated that the aspect ratio of delaminated clay nanoplatelets was approximately 150. The increase of the storage modulus below and above the glass transition temperature was achieved without reducing glass transition temperature and Izod impact strength with increasing clay content.

Materials Testing↗

PubMed2003

Hybridoma cells immobilized on nonwoven polyester fabric discs: proliferation and monoclonal antibody production in stationary culture.

Mouse hybridoma cells (O146S) producing a monoclonal antibody against the 146S antigenic particles of O type apthhoviruses were proliferated on the nonwoven polyester fabric (NWPF) discs in a stationary culture. A series of batch experiments were performed in Petri dishes containing RPMI 1640 medium supplemented with 10% (v/v) fetal bovine serum. During the cultivation period glucose and lactate concentrations were measured and monoclonal antibody concentration was determined by sandwich enzyme-linked immunosorbent assay (ELISA). The results showed that in the presence of the NWPF discs cell viability, cell yield, and total monoclonal antibody production was higher than that of the disc-free culture.

Animals↗

PubMed1988

Aliphatic polyesters and cellulose-based polymers for controlled release applications.

The general technologies for fabricating drug delivery systems are briefly discussed in the present review. Furthermore, two types of commonly used polymers, biodegradable aliphatic polyesters for parenteral administration and cellulose-based polymers for oral uses, are presented by means of selected examples of their properties and applications to control drug release.

Cellulose↗

PubMed2002

In vitro performance characteristics of a high-flux hemodialyzer with a novel polyester-polymer-alloy (PEPA) membrane.

Despite improvements in hemodialyzers with respect to their clearance of middle and high molecular mass molecules, accumulation of specific solutes in the circulation of dialysis patients continues to be a medical problem. A new membrane material, polyester-polymer alloy (PEPA) which has been developed to have a filtration profile akin to that of the natural kidney, is now being used in hemodialyzers. This study evaluates the performance of a PEPA-based hemodialyzer alongside a selection of available competing high-flux dialyzers using official standardized methods. The new membrane material appears to be a viable alternative which offers performance at least as good as that of the competition. The promising results obtained with the PEPA membrane suggest that a detailed clinical performance study should be undertaken.

Alloys↗

PubMed1997

A follow-up arthroscopy after anterior cruciate ligament reconstruction using the patellar tendon augmented by woven polyester.

Follow-up arthroscopy was performed on 9% patients who had undergone anterior cruciate ligament (ACL) reconstruction with patellar tendon augmented by woven polyester. The interval between surgery and arthroscopy ranged from 6 to 26 months, with a mean of 13.1 months. The patients were classified into 4 grades according to the arthroscopical findings as follows: grade 1, ligamentous tissue ruptured or not observed; grade II, loose and thin ligamentous tissue observed; grade III, thick and taut ligamentous tissue observed, but some ligamentous strands exposed from the synovial tissue: grade IV, thick and taut ligamentous tissue with a synovial tissue observed, as in normal ACL. Based on the arthroscopical findings, 4 of the 92 patients were rated as grade I, 11 as grade II, 24 as grade III, and 53 as grade IV. Correlation between the arthroscopical and functional test results indicated that the mean injured-to-uninjured differences of KT-1000 measurements were significantly smaller in the grade IV group than in the grade I and grade II groups (p < 0.05). These results suggest that postoperative anterior knee laxity correlate significantly with arthroscopical results, and is a useful parameter for evaluating ACL reconstruction.

Adolescent↗

PubMed2003

A long term comparison between Denacol EX-313-treated bovine jugular vein graft and ultrafine polyester fiber graft for reconstruction of tight ventricular outflow tract in dogs.

A Denacol EX-313 (Denacol)-treated bovine venous graft and an ultrafine polyester fiber (UFPF) graft were transplanted as patch graft into the right ventricular outflow tract under extracorporeal circulation in six dogs each experimentally. Hemodynamics in right heart and histological findings around the graft were compared between both groups over a period of one year after grafting. Pressure measurements and angiocardiography were performed through a cardiac catheter. Right ventricular pressure, pulmonary artery pessure, and right ventricle to pulmonary artery gradient were within normal limits in both groups at 1, 2, 3, 4, 6, and 12 months or more after grafting. No difference were seen between the values for the Denacol and the UFPF group. Histologically, the medial surface at the site of grafting was covered with vascular endothelial cells at one month after grafting in both groups. The density of the vascular endothelial cells increased with time after grafting, showing no clear difference between the two groups. Subendothelial layers comprised of collagen fibers, elastic fibers, and inflammatory cells decreased with time in both groups, but there was less cell infiltration in the Denacol group than in the UFPF group at all time points after grafting. In addition, the central cut thickness value of the graft tended to be thinner in the Denacol group than in the UFPF group at all observation time points after grafting. In the Denacol group, very slight metaplasia of cartilage was noted in a portion of the graft margin at six months or more after grafting, but no other abnormalities were observed. These results suggest that the Denacol-treated bovine venous graft has better grafting characteristics than the UFPF graft with easier intra-operative handlings and less tissue reactions after grafting.

Animals↗

PubMed1985

Strength of carbon and polyester fibre tendon replacements. Variation after operation in rabbits.

The calcaneal tendons of rabbits were excised and either replaced with a carbon or polyester fibre implant, or left as controls. The strength of the neotendons and their mode of failure under tension were examined at intervals up to six months after operation. Return to near normal strength took six months to develop, suggesting that patients having ligament or tendon reconstructions should not resume normal activity for several months. Carbon fibre-based neotendons showed progressive elongation which, unless avoided by a sufficient period of immobilisation, would affect the functional result.

Animals↗

PubMed1992

Anterior cruciate ligament replacement with polyester fibre. A long-term study of tissue reactions and joint stability in sheep.

We excised the anterior cruciate ligament from the left stifle of 24 sheep and replaced it by a polyester fibre implant routed 'over the top' of the femoral condyle and fixed, using grommets and screws. All the joints were sound, and the animals moved normally until they were killed at six, 12 and 24 months after operation. We found that the implants were always covered by host tissue, which matured into bundles with a histological appearance similar to the natural ligament. The implants were joined to the bones by organised fibrous tissue and there was no anchorage loosening. There was no synovitis, but the operated joints showed progressive cartilage degeneration. The reconstructed joints became less stable immediately after operation, but regained normal stability as the neoligaments developed. The neoligaments lost strength with time, despite tissue ingrowth. The good functional, biomechanical, and histological results justify clinical trials of this type of implant.

Animals↗

PubMed2002

Chronic rupture of tendo Achillis. Long-term results of operative management using polyester tape.

We report the long-term results of the surgical treatment of chronic rupture of tendo Achillis using polyester tape. This requires minimal postoperative splintage and allows early mobilisation and a prompt return to work and sport. We reviewed 16 patients (10 women and 6 men) at a mean period of three years after surgery. The median time from injury to operation was 16.8 months (3.9 months to 13 years), and the median age of the patients was 52 years (27 to 78). The median time to full weight-bearing was 40 days and the median time for return to sport was 18 weeks (5.4 to 32). One patient required further surgery and one had numbness along the distribution of the sural nerve. After surgery only two patients had increased dorsiflexion of the ankle compared with the uninjured side. There were no cases of rerupture. We recommend this technique for the treatment of chronic rupture of tendo Achillis.

Achilles Tendon↗

PubMed2004

Repair of acute rupture of the Achilles tendon: a new technique using polyester tape without external splintage.

INTRODUCTION: A new method of treating acute rupture of the Achilles tendon using polyester tape is reported. This requires no postoperative splintage, allows earlier mobilisation and prompt return to work and sport. PATIENTS AND METHODS: Thirty patients were reviewed prospectively and at a mean of 3 years from surgery. RESULTS: The average time of return to work, full weight-bearing and to driving was 40 days, 45 days and 49 days, respectively. The average time for return to sport was 122 days. Three patients required further surgery, two for infected wounds and one for scar release. There was one sural nerve injury. Twenty-two patients regained a normal range of ankle and subtalar movement, with the mean power of plantar flexion 84% of the opposite side. Of the 22 patients who played sport, 14 were still performing at the same or a higher level. There were no re-ruptures over this period. CONCLUSIONS: The technique is straightforward and avoids splintage. It also conveys other short- and long-term advantages over more established methods.

Achilles Tendon↗

PubMed1989

Efficacy and safety of a polyester leukocyte removal filter for whole blood and red cell concentrate filtration.

Patients receiving multiple whole blood transfusions often experience adverse clinical symptoms caused by leukocytes. In the present study, the efficacy and safety of a polyester filter for leukocytes (Sepacell R-500) was evaluated. Donor units of whole blood and red cell concentrate stored for varying lengths of time were filtered. Emphasis was placed on humoral parameters indicative of release and/or activation reactions of granulocytes (neutral proteinase elastase, lysozyme, aggregation, chemiluminescence) and erythrocytes (lactate dehydrogenase, plasma haemoglobin). Nonspecific adsorption effects were investigated by plasma protein determinations (albumin, alpha 2-macroglobulin). A complete blood cell count as well as values of haemoglobin and haematocrit were determined. Sepacell R-500 proved to be a highly efficient filter to the leukocyte depletion of blood. Our results of erythrocyte and granulocyte related humoral parameters provided no significant evidence of filtration mediated activation or releasing reactions of clinical consequence.

Blood Preservation↗