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At least 217 records · Page 12Linked to original sources

PubMed1994

[Improved sternotomy closure with polyester tapes and conventional wires].

In the purpose of reducing the occurrence of postoperative sternal dehiscence, improved technique of closure with supplemental use of polyester tapes was performed. To add to the conventional closure with wires, two polyester tapes were used around the body of sternum through the intercostal spaces just before approximation of sternum. The sternum was firmly fixed at the body and the tapes will prevent cut sternum by the wires and disruption of the wires themselves. In our series of recent 155 cases with this technique of closure, no sternal dehiscence occurred.

Bone Wires↗

PubMed1996

[Impregnated polyester prostheses: a theoretical advantage].

Leak-proof polyester grafts impregnated with collagen, gelatine or albumin are routinely used in vascular surgery. Theoretically, there are several advantages: no need for pre-coagulation, reduced operation time and graft manipulation, less blood loss during the operative period, better healing with a potentially greater resistance to infection. We analyzed all the publications in scientific journals to verify whether these theoretical advantages are validated by clinical trials. There have been 12 non-comparative series reporting favourable results but the lack of control groups makes it difficult to draw conclusions. Five comparative series with random assignment of patients have been reported. None of these series showed a substantial benefit from impregnation. Thus the use of an impregnated polyester graft would not appear to be justified for routine standard aorto-iliac surgery. Conversely, although no evidence has been provided by a comparative study, the major risk of haemorrhage in procedures such as extra-corporal circulation, the thoracic or abdominal aorta and in patients with a coagulation disorder, impregnated graft probably constitute an important progress.

Albumins↗

PubMed1997

The acceptability and effectiveness of a polyester drinking-water filter in a dracunculiasis-endemic village in northern region, Ghana.

In the global effort to eradicate dracunculiasis (guinea-worm disease) one of the main tools is the use of filters for filtering unsafe drinking-water. The expensive and high-quality monofilament nylon filters, which for many years were donated to all dracunculiasis-endemic countries, are now mainly reserved for highly endemic countries. Polyester cloth is less expensive, and we investigated the user acceptability and effectiveness of this material as a drinking-water filter in a dracunculiasis-endemic village in Northern Region, Ghana, over a 3-month period. The polyester cloth completely retained the stages of copepods that are responsible for transmitting dracunculiasis. Over the 3-month study period a majority of respondents found that the new cloth was superior to the nylon filter with regard to strength (83%), filtering time (80%), and the ease with which the filter could be cleaned (87%). Inspection revealed that the filters were used intensively and that the new cloth was damaged after 2-3 months of use, which is also the case for the monofilament nylon filters.

Animals↗

PubMed1998

Laparoscopic inguinal hernia repair using fine-caliber instruments and polyester mesh.

Laparoscopic inguinal hernia repair (LH) requires similar scar size to traditional open repair. To perform LH with minimal access, finer instruments were used. A 5-mm laparoscope was inserted from the umbilicus, and surgical instruments were inserted through 5- and 3-mm trocars to perform LH by the transabdominal preperitoneal approach. Polyester mesh was placed over the hernia orifice and the peritoneum was closed with 3-0 silk sutures. Sixteen patients underwent smaller access LH and 24 had standard LH. Although smaller access LH took longer (105.7 versus 83.9 min), significantly fewer patients required analgesia after smaller access LH than after standard LH (12.5 versus 70.8%), and the postoperative hospital stay was shorter (4.6 versus 5.6 days). In addition, a better cosmetic outcome was obtained with smaller access LH. In conclusion, access was minimized by using fine-caliber instruments and polyester mesh, making LH less invasive and improving the cosmetic outcome.

Adult↗

PubMed2002

Immunogenicity of polymeric implants: long-term antibody response against polyester (Dacron) following the implantation of vascular prostheses into LEW.1A rats.

Implanted biomaterials trigger acute and chronic inflammatory responses directly correlated to the central role of phagocytic cells at the host-implant interface. This study was designed to evaluate specific humoral immune responses following repeated intraperitoneal implantations of collagen-impregnated polyester (Dacron) prosthetic segments into LEWIS rats. Serum antibody detection was performed by enzyme immunoassay with the prosthetic segments as a target. Cutoff values for antibody positivity were greater than or equal to the 99th percentile for control rats. Polymer immunoglobiulin G (IgG) antibodies were significantly increased (p < 0.05) by repeated implantation and were subsequently followed until experimental day 293. Antibody formation was significantly enhanced through the application of complete Freund's adjuvant in combination with the first implantation. All rats within this group were antibody-positive on day 53, but only 6 of 10 animals that received the prosthesis without the adjuvant were. After preincubation of sera with bovine collagen type I (solid phase adsorbed or in solution), polymer antibody binding was discovered not to be diminished, indicating that the IgG antibodies detected were not directed against the prosthesis impregnation. Furthermore, a significant correlation was obtained between polymer antibody binding to collagen-impregnated and nonimpregnated prostheses (r(s) = 0.797, p < 0.001). There was no substantiated correlation between antibody binding to polyester and to an irrelevant polymer (Tecoflex EG 80). We conclude that specific polymer antibodies may indeed provide an additional parameter for biocompatibility testing as well as a possible serological marker of an inflammatory response to implants.

Animals↗

PubMed1986

The cytocompatibility of compound polyester-protein surfaces using an in vitro technique.

To avoid the need to preclot porous polyester (Dacron) vascular prostheses, we have proposed the use of a protein coating that will promote the growth and adhesion of endothelial cells. This study assessed the relative advantages of coating woven, knitted, and velour polyester fabrics with albumin, collagen, and a albumin-collagen mixture after preservation in saline or drying by a commercial dehydration process. Preclotted fabrics were used as controls. The cytocompatibility of these biopolymers was measured by an organotypic culture technique which relies on the migration of chick embryonic endothelial cells. After 7 d of culture the cytocompatibility was quantified by counting the cells in the area of migration and the morphology of the endothelial cells was observed by scanning electron microscopy. In general, the knitted and velour fabrics showed superior compatibility than the woven one. The results confirmed that collagen, either alone or combined with albumin, provides in most cases a more cytocompatible surface than albumin alone. A cell morphology most closely resembling that of natural arterial endothelial cells was observed on the albumin-collagen substrate.

Albumins↗

PubMed2003

Radiofrequency-generated glow discharge treatment: potential benefits for polyester ligaments.

This multicenter study has revealed that treating a woven polyethylene terephthalate (polyester) ligament with a radiofrequency (RF)-generated glow discharge (RFGD) produces marked benefits in terms of increased cell attachment and proliferation on the implant surface. In vitro tests of the same material revealed that the number of synovial fibroblasts attached to the treated samples after 14 days was four times that of the untreated material. Many of the cells were spread over the surface of a single filament, and some formed bridges between one filament and the next. The incorporation of [(3)H]-thymidine by synovial stromal cells (a measure of the amount of cell division) growing on the treated material was five times that on the untreated samples. The amount of DNA present on the treated material was also found to be almost an order of magnitude greater than that on untreated samples. This increase in cell attachment and proliferation is almost certainly related to a notable increase in wettability of the polyester surface induced by treatment. Mechanical tests revealed that, for ligaments with a nominal ultimate tensile strength of 2100 N, RF-generated glow treatment reduced the ligament's strength by 12% but increased its stiffness by 15%. After a medium-term fatigue test (10.8 million cycles), however, there appeared to be recovery of the mechanical properties, with the strength and stiffness of untreated and treated samples being essentially the same. After exhaustive fatigue tests (more than 62 million cycles) the residual strength of the treated ligaments was only 9% lower than that of the unfatigued and untreated ligaments.

Biomechanical Phenomena↗

PubMed1987

Radiosterilization of albuminated polyester prostheses.

The study reported here is concerned with the radio-sterilization of Dacron vascular prostheses coated with crosslinked albumin. gamma-Radiations have no effect on the mechanical properties of the polyester fibres or on their crystallinity, whether irradiated in a dry state or immersed in saline. Special attention has been paid to the release of the albumin, or protein fragments from the reticulum using 125I-labelled albumin as a radiotracer. The albumin leakage depends upon the type of Dacron fabrics considered but the values derived from radioactivity measurements are always greater than those directly measured, which indicates a radio-induced break of the bond between iodine and albumin; this has nothing to do with the break of the association between albumin and Dacron. Moreover no cytotoxicity of the irradiated immersion medium has been observed using a test based on organotypic culture in liquid medium. Thus radio-sterilization of an albuminated polyester vascular prosthesis immersed in saline appears to be a suitable procedure.

Albumins↗

PubMed1995

New bioactivation mode for vascular prostheses made of Dacron polyester.

The performance of vascular prostheses, especially those of small calibre, still presents several problems. The use of polyesters such as the well-known poly(ethylene terephthalate) (Dacron) and, more recently, poly(tetrafluoroethylene) and polyurethanes provides a marked improvement. We have developed a process to increase the efficiency of such prostheses, using the ability of the Dacron polyester to be covalently modified by proteins under mild chemical conditions. The biomaterial is obtained from the particular interaction of elastin-solubilized peptides with type I + III collagens under very precise conditions. We have obtained an irreversible covalent bonding on Dacron. These biological conditions and the addition of connective proteins and glycosaminoglycans conferred on the resulting material a composition and a three-dimensional structure equivalent to the subendothelium, providing bioactive properties suitable for the development of a vascular prosthesis.

Biocompatible Materials↗

PubMed2001

Brush-like branched biodegradable polyesters, part III. Protein release from microspheres of poly(vinyl alcohol)-graft-poly(D,L-lactic-co-glycolic acid).

Brush-like branched polyesters, obtained by grafting poly(lactic-co-glycolic acid), PLGA, onto water-soluble poly(vinyl alcohol) (PVAL) backbones, were investigated regarding their utility for the microencapsulation of proteins. Poly(vinyl alcohol)-graft-poly(lactic-co-glycolic acid), PVAL-g-PLGA, offers additional degrees of freedom to manipulate properties such as e.g. molecular weight, glass transition temperature and hydrophilicity. PLGA chain length was varied at a constant molecular weight (M(w)) of the PVAL backbone and secondly M(w) of the PVAL backbone was varied keeping the PLGA chain lengths constant. The most striking feature of these polymers is their high M(w). Microencapsulation of hydrophilic macromolecules, such as bovine serum albumin, ovalbumin, cytochrome c and FITC-dextran using a w/o/w double emulsion technique was investigated. Surface morphology, particle size, encapsulation efficiencies and protein release profiles were characterized as well. Microencapsulation of model compounds was feasible at temperatures of 0-4 degrees C with yields typically in the range of 60-85% and encapsulation efficiencies of 70-90%. Both, encapsulation efficiency and initial protein release (drug burst) were strongly affected by the glass transition temperature, T(g), of the polymer in contact with water, whereas the in vitro protein release profile depended on the PVAL-g-PLGA structure and composition. In contrast to PLGA, protein release patterns were mostly continuous with lower initial drug bursts. Shorter PLGA chains increased drug release in the erosion phase, whereas initial pore diffusion was affected by the M(w) of PVAL backbone. Release profiles from 2 to 12 weeks could be attained by modification of composition and molecular weight of PVAL-g-PLGA and merit further investigations under in vivo conditions. The in vitro cytotoxicity of PVAL-g-PLGA is comparable to PLGA and therefore, this new class of biodegradable polyesters has considerable potential for parenteral drug delivery systems.

Animals↗

PubMed2002

ABA-triblock copolymers from biodegradable polyester A-blocks and hydrophilic poly(ethylene oxide) B-blocks as a candidate for in situ forming hydrogel delivery systems for proteins.

Hydrogels are very attractive delivery systems for hydrophilic macromolecules such as proteins and DNA because they provide a protective environment and allow control of diffusion by adjusting cross-link densities. Physically cross-linked hydrogels generated by rapid swelling upon exposure to an aqueous environment can be obtained from ABA triblock copolymers containing hydrophobic polyester A-blocks and hydrophilic polyether B-blocks. They provide an attractive alternative to chemically cross-linked systems since they allow incorporation of macromolecular drug substances under mild process conditions. Moreover, they show controlled degradation behavior and excellent biocompatibility. In this review the synthesis and characterization of ABA triblock copolymers from polyester hard segments and poly(ethylene oxide) [PEO] soft segments as well as their biological and degradation properties will be discussed. Their use as biodegradable drug delivery devices in the form of implants, micro- and nanospheres has attracted considerable interest especially for proteins and may provide an alternative to poly(lactide-co-glycolide).

Animals↗

PubMed2000

Assessment of a polyester-covered nitinol stent in an atherosclerotic swine model.

PURPOSE: To evaluate the short-term patency and healing characteristics of the Cragg EndoPro covered stent in an atherosclerotic model as one of the Food and Drug Administration requirements before possible approval of the device for human use in the United States. MATERIALS AND METHODS: Seventeen self-expanding stent-grafts were placed in the aorta and right and left iliac arteries of six Yucatan microswine exposed to a regimen of accelerated atherosclerosis. The stent-grafts were constructed from nitinol wire formed into a tubular zigzag configuration. The stent frame was covered by a thin woven polyester fabric tube, with medium permeability, available in multiple diameters and lengths. The animals were killed at 24 hours, 3 months, and 6 months. Assessment was done by angiography and histology. RESULTS: All stents were patent immediately after deployment. Two stents were occluded at follow-up, indicating an 88% patency rate. Minor lumen narrowing was found at the follow-up intervals. Histologic examination revealed a mixture of mature and immature endothelial cells lining both the native and stented regions in all vessels examined. The new endoluminal surface was composed primarily of fibrocollagen and elastic fibers and smooth muscle cells. Intimal thickness was inversely correlated to medial thickness. Medial compression with atrophy was observed routinely with rare necrosis. Complete tissue ingrowth was seen by 3 months. The degree of vascular inflammation increased over time, as well as the foreign body giant cell reaction to the polyester fabric. CONCLUSION: The patency rate does not appear to be better than that with angioplasty or noncovered stent placement in the studied time frame. The progressive vascular inflammatory changes noted should be further investigated in longer-term animal trials to ensure its safety in humans because this device is meant to be permanent.

Alloys↗

PubMed1988

Experimental colonization of a polyester vascular graft with Staphylococcus aureus: a quantitative and morphologic study.

Colonization of a polyester (Dacron) vascular graft by Staphylococcus aureus 209P-R was studied. Twenty-five dogs had thoracoabdominal aortic bypass. After intervals of 2 hours (three dogs), 8 days (five dogs), 1 month (six dogs), 2 months (six dogs), or 6 months (five dogs), a bacteremic challenge was produced by intravenous injection of 6 x 10(8) colony-forming units of S. aureus. Two hours later grafts were removed and cut into 10 fragments, each submitted to bacterial counts and scanning electron microscopic studies. Results of bacterial counts were expressed in colony-forming units (CFU) per square centimeter of graft segment (median [lower to upper quartiles]). Normal canine aortas (n = 2) used as controls trapped no bacteria. Colonization of Dacron grafts varied according to the duration of graft function (p less than 0.01): after 2 hours, 4416.5 CFU (1158 to 9073 CFU); after 8 days, 1515 CFU (963 to 2893 CFU); after 1 month, 199 CFU (86 to 538 CFU); after 2 months, 615 CFU (243 to 1407 CFU); and after 6 months, 1 CFU (1 to 5 CFU). Heavily colonized fragments were observed for duration of graft function of 2 months or less, whereas at 6 months all the fragments trapped fewer than 50 CFU/cm2 of graft segment. Scanning electron microscopy showed that colonization was closely associated with healing. Staphylococcal entrapment was related to the amount of fibrin deposits, which were especially abundant where the thrombotic matrix was unorganized and on bare polyester filaments. Graft colonization is especially to be feared in the first weeks after graft implantation, an observation which may help to define guidelines for preventing hematogenous vascular graft infection.

Animals↗

PubMed1975

A comparison in vivo dacron wool (Swank) and polyester mesh (Pall) micropore blood transfusion filters in the prevention of pulmonary microembolism associated with massive transfusion.

Experiments were performed to compare the effectiveness in vivo of the two most widely used micropore blood transfusion filters in preventing detrimental physiologic changes associated with transfusion of microaggregate-containing blood. Exchange transfusion with stored blood having an elevated screen filtration pressure (SFP) through polyester mesh (Pall) filters (Group PM) was followed by decreases in arterial blood pH and O2 consumption, increases in arterial blood pyruvate and lactate concentrations, and a decrease in pulmonary DO2. The lungs of 5 of 6 animals revealed emboli far out in the pulmonary microcirculation. These changes did not occur in animals transfused through dacron wool (Swank) filters (Group DW). Even though an increase after transfusion in pulmonary Qs/Qt in Group PM did not achieve statistical significance when compared to pretransfusion Qs/Qt, it was significantly higher than that in animals in Group DW. Both filters removed considerable quantities of microaggregates; however, the polyester mesh (Pall) filters permitted passage of small microaggregates and development of ditrimental physiologic changes. Dacron wool (Swank) filters completely removed measurable microaggregates and detrimental changes did not occur.

Animals↗

PubMedDate not supplied

Effects of initial graft tension on clinical outcome after anterior cruciate ligament reconstruction. Autogenous doubled hamstring tendons connected in series with polyester tapes.

We conducted a prospective, randomized, short-term study to clarify the effects of initial graft tension on clinical outcome after arthroscopically assisted anterior cruciate ligament reconstruction with autogenous doubled semitendinosus and gracilis tendons connected in series with polyester tapes. Seventy Japanese patients with chronic, "isolated" anterior cruciate ligament tears were entered in the study. The patients were randomly divided into three groups based on initial graft tension: Group 1 (20 N), Group 2 (40 N), or Group 3 (80 N). No statistical differences were noted among the three groups with regard to their background factors. The patients were observed for 2 years or more after surgery. Postoperatively, the average side-to-side difference in anterior laxity was 2.2 +/- 2.4 mm in Group 1, 1.4 +/- 1.8 mm in Group 2, and 0.6 +/- 1.7 mm in Group 3. Analysis of variance testing showed that the postoperative laxity in Group 3 was significantly less than that in Group 1. Spearman's rank-order correlation analysis also demonstrated significant correlation between the magnitude of initial graft tension and the magnitude of the postoperative laxity. This study demonstrates that relatively high initial tension (up to 80 N) reduces the postoperative anterior laxity of the knee joint after anterior cruciate ligament reconstruction using the doubled autogenous hamstring tendons connected in series with polyester tapes.

Adult↗

PubMed1984

Comparison of the structure of neotendons induced by implantation of carbon or polyester fibres.

Carbon-fibre and polyester-fibre implants of comparable dimensions were used to replace the calcaneal tendon in 30 sheep. The neotendon produced in proximity to the polyester fibres was denser, more collagenous and more closely adherent than that in the carbon-based neotendon. Fragmentation of the carbon caused continuing cellular reaction which was associated with a poor collagen response.

Animals↗

PubMed1984

Polyester wax embedding and sectioning technique for immunohistochemistry.

We have developed a method useful for immunohistochemical studies by combining tissue fixation with buffered neutral formalin and polyester wax embedding. Buffered neutral formalin fixation preserves cell and tissue fine structure, and also the antigenicity of unstable enzymes. Polyester wax embedding makes possible thin serial sections of various tissues and preserves antigenicities for at least 6 months. We have demonstrated using this technique the localization of alpha-amylase in mouse salivary gland, parietal-cell specific antigen in mouse glandular stomach, and DNA polymerase alpha and beta in chick tissue.

Animals↗

PubMed1986

Permanent preservation of whole alizarin red S skeletons by clearing and embedding in polyester resins.

A one-step clearing and embedding procedure for alizarin red S stained skeletons is described. Embryos are fixed in formalin, skinned and eviscerated. After staining in a 10 mg/liter solution of alizarin red S in 5% aqueous KOH, specimens are dehydrated in a graded series of acetone-polyester monomer solutions. Finally, the specimens are embedded at room temperature in the polyester resin. A special reusable metallic mold is described for embedment of large fetuses. Specimens previously cleared in glycerol can be processed with this method.

Anthraquinones↗