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At least 1,153 records · Page 64Linked to original sources

PubMed2000

Patch incorporation in diaphragmatic hernia.

BACKGROUND/PURPOSE: Biomaterial insertion often is required for closure of congenital diaphragmatic hernia (CDH). The optimal biomaterial remains uncertain. This study was designed to compare a commonly used patch (polytetrafluoroethylene) with a recently available fabric, fluorinated polyester. The aim of this study was to determine the clinical performance, histological tissue-polymer interaction, bacterial adhesion, and shrinkage rates of biomaterial inserted endoscopically into a CDH lamb model. METHODS: Polytetrafluoro-ethylene (PTFE) and fluorinated polyester (FP) were randomised for laparoscopic patch insertion into 12 lambs. All lambs (age <4 weeks) underwent 3-port laparoscopy, surgical creation of diaphragmatic hernia, and sutured patch placement. Two PTFE and 2 FP lambs were killed at 1-, 3-, and 6-month intervals postoperatively. Postmortem examination histopathology, electron microscopy, and specific bacterial broth immersion (Escherichia coil, Staphylococcus aurens, and epidermidis) were performed. RESULTS: All 12 lambs completed the study with intact patches that were fully peritonised. One abdominal adhesion was noted in a FP lamb at 6 months. FP was comparatively easier to insert, manipulate, and suture endoscopically. Histopathology findings showed that PTFE patches created a strong peripheral foreign body reaction with dystrophic calcification, whereas FP was well incorporated with intrapatch fibroblastic activity and neovascularsation. No significant difference in resistance to bacterial adhesion of relevant organisms was noted between the materials. Graft shrinkage for FP was 7% in one direction only, evident by 3 months. CONCLUSIONS: Fluorinated polyester has advantages in this laparoscopic lamb model. It shows rapid and sustained incorporation with intrapatch neovascularisation when compared with polytetrafluoro-ethylene's significant foreign body reaction. It was preferred for its endoscopic handling and suturing properties. The laparoscopic techniques used may contribute to the general lack of adhesions, and insufficient data are available to comment on the comparative effect of the materials on adhesion formation. No difference was demonstrated in resistance to bacterial adherence in the harvested materials.

Animals↗

PubMed1998

Penetration of household insecticides through different types of textile fabrics.

Six different types of fabrics were compared for their ability to protect against human exposure to three different commercial household aerosol insecticides. Fabrics used in this investigation were, 100% cotton, cotton-polyester thermal underwear, cotton-polyester blend (twill), 100% acrylic, 100% wool and artificial silk (rayon). The household insecticides were, Black Flag (Ant and Roach Killer), Raid (Ant and Roach Killer) and Hot Shot (Wasp and Hornet Killer) containing propoxur, permethrin/pyrethrins and chlorpyrifos/allethrins as their active ingredients respectively. A fluorescent tracer, 4-methyl-7-diethyl amino coumarin was mixed with the aerosol (or equivalent aliquot) and sprayed onto cloth squares fitted on Whatman paper patches. The percentage of penetration through the cloth was quantified by the intensity of the fluorescence spectrum of each patch extract and the amount of the tracer recovered was calculated. The extract was concentrated to 1/10th of the volume to measure the content of each of the insecticides by supercritical fluid chromatography (SFC) using electron capture (ECD) and diode array detectors. Scanning electron microscope (SEM) images of the fabrics showed the geometry of the yarn. The results obtained from the fluorescence spectra, SFC and SEM showed that cotton-polyester (twill), cotton, wool and cotton thermal underwear were the least penetrable materials for the aerosols. On the other hand, acrylic and artificial silk (rayon) were the most penetrable cloth types.

Aerosols↗

PubMed1998

Biodegradable products by lipase biocatalysis.

The interest in the applications of biocatalysis in organic syntheses has rapidly increased. In this context, lipases have recently become one of the most studied groups of enzymes. We have demonstrated that lipases can be used as biocatalyst in the production of useful biodegradable compounds. A number of examples are given. 1-Butyl oleate was produced by direct esterification of butanol and oleic acid to decrease the viscosity of biodiesel in winter use. Enzymic alcoholysis of vegetable oils without additional organic solvent has been little investigated. We have shown that a mixture of 2-ethyl-1-hexyl esters can be obtained in a good yield by enzymic transesterification from rapeseed oil fatty acids for use as a solvent. Trimethylolpropane esters were also similarly synthesized as lubricants. Finally, the discovery that lipases can also catalyze ester syntheses and transesterification reactions in organic solvent systems has opened up the possibility of enzyme catalyzed production of biodegradable polyesters. In direct polyesterification of 1,4-butanediol and sebacic acid, polyesters with a mass average molar mass of the order of 56,000 g mol-1 or higher, and a maximum molar mass of about 130,000 g mol-1 were also obtained by using lipase as biocatalyst. Finally, we have demonstrated that also aromatic polyesters can be synthesized by lipase biocatalysis, a higher than 50,000 g mol-1 mass average molar mass of poly(1,6-hexanediyl isophthalate) as an example.

Biodegradation, Environmental↗

PubMedDate not supplied

Toxicity of smoke during chair smoldering tests and small scale tests using the same materials.

Toxicological evaluation of smoke produced during smoldering chair tests was undertaken by exposing mice to smoke emitted prior to, as well as following, flaming ignition of the chairs. By exposing several groups of mice, using undiluted smoke from the room containing the chairs, as well as various dilutions of the smoke, different levels of acute lethality were obtained. From these experiments, chairs constructed with polyurethane foam were found to create higher toxic atmospheres than chairs constructed with polyester or cotton fiber cushions. The same materials (polyurethane foam, polyester and cotton fibers) were also thermally decomposed in a small scale system and mice were exposed to the smoke to evaluate acute toxicity. Again polyurethane foam was found to produce smoke more toxic than smoke produced by polyester and cotton fibers. Sensory irritation monitored in mice during the smoldering tests indicated that an intense level of irritation was present long before large amounts of smoke were generated and long before flaming ignition occurred. The phenomenon of eye, nose and throat irritation would therefore be the first effect impeding escape attempts of individuals in a fire situation. Sensory irritation was followed by asphyxiation as evolution of carbon monoxide or hydrogen cyanide, or both, occurred. The same pattern of responses was observed with smoke generated with the small scale decomposition system.

Animals↗

PubMed2001

Biocompatibility and performance of the Wallstent and several covered stents in a sheep iliac artery model.

PURPOSE: To compare the biocompatibility and performance of various stent-grafts to those of a bare stent in an ovine model with a subchronic (3 months) endpoint. MATERIALS AND METHODS: Three different types of stent-grafts (ePTFE/nitinol, n = 8; polyester/nitinol, n = 8; and polycarbonate urethane/cobalt-alloy, n = 8) and a bare stent as a control (Ni-Co-Ti-steel-alloy, n = 8) were implanted in the iliac arteries in eight female sheep. One type of each stent-graft was implanted per animal, two implants at each side. The implantation sites for each type varied from animal to animal. Angiographic control and intravascular ultrasound (IVUS) imaging were performed before and after implantation, after 2 months, and before explantation at 3 months and were used to characterize patency and to assess intimal hyperplasia. After 3 months, the implants were retrieved and subjected to histologic evaluation (after methacrylate embedding, cutting, and histologic staining) to characterize the biologic response. RESULTS: Implantation was technically successful in all procedures. At 2 and 3 months after implantation, all segments in which stents had been implanted were patent. Marked neointima formation was found in the polyester-covered stent-graft that showed significant luminal narrowing of 50%, compared to the ePTFE-covered (24%) and polycarbonate urethane-covered endoprostheses (22%), as well as the bare stent (Wallstent; 9%; P < .001). A minimal inflammatory vessel wall reaction was demonstrated for the polyester-covered and ePTFE-covered endoprostheses; the polycarbonate urethane-covered stent-graft's response was demonstrable but not significantly different from that of the Wallstent. At 3 months, the ePTFE-covered stent-graft showed incomplete (>90%) endothelial coverage; in the other endoprostheses, complete but partially immature endothelialization was found. CONCLUSION: All stent-grafts induced an inflammatory vessel wall reaction with neointimal hyperplasia. The polyester-covered endoprosthesis caused a marked reaction with 50% luminal stenosis. Endothelialization was retarded with the ePTFE-covered stent-graft. The bare stent performed best in regard to neointimal formation and caused the least inflammatory response.

Alloys↗

PubMed2001

Analysis of adsorption function of polyhydroxybutyrate depolymerase from Alcaligenes faecalis T1 by using a quartz crystal microbalance.

Enzymatic adsorption and degradation of three types of aliphatic polyester films and two types of polyolefin films by the extracellular PHB depolymerase from Alcaligenes faecalis T1 have been studied by using a quartz crystal microbalance (QCM) technique. Hydrolysis of poly[(R)-3-hydroxybutyrate] was quantitatively followed by the QCM technique. Adsorption of the enzymes to films was also quantitatively detected by the QCM. Kinetic study on enzymatic adsorption suggests that the PHB depolymerase binds to the substrates not only by hydrophobic interaction but also by specific interaction between the ester bonds of polyesters and the binding domain of the enzyme. The results show that the QCM technique is a sensitive tool to study enzymatic degradation kinetics of biodegradable polyesters.

Adsorption↗

PubMed1999

In vitro comparison study of CD63 and CD62P expression after contacting leukocyte filters.

CD63 and CD62P have been recognized as platelet activation markers. This study investigated the secretion of these antigens to compare the platelet activation between a newly developed stainless steel leukocyte filter (SSLF) and 7 polyester or polyurethane commercially available leukocyte filters. Flow cytometry demonstrated that the SSLF initiated significantly smaller effects in terms of mean fluorescence intensity of CD63 (p<0.03) and of the amount of CD62P expressing platelets (p<0.002) compared to the polyurethane filters. However, there was no statistical difference between the SSLF and polyester filters. The result of this study suggests that the SSLF caused less platelet activation than the polyurethane filters and has biocompatible characteristics comparable to the currently available polyester filters. Stainless steel was selected because of its physicochemical conductivity. With these results, further evaluation of the SSLF will be continued in an attempt to develop an active immunomodulator using this unique characteristic.

Adult↗

PubMed2004

Migration from can coatings: part 2. Identification and quantification of migrating cyclic oligoesters below 1000 Da.

Metal cans for food use can be coated with lacquers based on polyester resins. Recent research has focussed on the identification and quantification of migrants released by coatings that are potentially absorbable (below 1000 Da). The presented method describes a procedure that was optimized to hydrolyse the polyester migrants into their monomers, polyvalent acids and polyols. The polyols were identified by gas chromatography with flame ionization detection GC-FID and the acids by high-performance liquid chromatography (HPLC) coupled with an ultraviolet and an electrospray ionization-mass selective detector (HPLC-ESI-MSD/UVD), respectively. With the knowledge of the polyester monomers, it was possible--at least tentatively--to identify the main components in the migrate as cyclic oligoesters by HPLC-ESI-MSD/UVD. A cyclic oligomer, CYCLO [3IPA (isophthalic acid) 3EG (ethylene glycol)] was synthesized and characterized by infrared, nuclear magnetic resonance and mass spectrometry as well as by elementary analysis for further confirmation. To determine the amount of migrating cyclic oligoesters, the response of the migrating substances was compared using different detectors, UVD, MSD and evaporative light scattering detector (ELSD). The response of the ELSD was dependent on the molecular weight of the analytes that reduced the accuracy of this detection type. The wavelength with the same absorption coefficient for IPA and terephthalic acid (TPA) was obtained at 232 nm. The UV(232nm) response of an oligoester is proportional to the number of its IPA/TPA moieties, which was verified for several TPA/IPA esters. The amount of the migrating oligoesters was determined using an UV(232nm) calibration of a commercially available TPA ester and the number of IPA/TPA moieties molecules gained from the ESI-MSD spectra. According to this method, the amount of migrating oligoesters below 1000 Da in the 95% ethanol migrate varied from 0.1 to 0.6 mg dm(-2) (0.6-3.6 mg kg(-1) food) in the examined coatings. The determined amounts account for about 50% of the total migrate below 1000 Da.

Chromatography, Gas↗

PubMedDate not supplied

Headspace analysis of benzene in food contact materials and its migration into foods from plastics cookware.

Concentrations of benzene of 29 and 64 mg/kg were found in two samples of thermoset polyester compounded for the manufacture of plastic cookware. In collaboration with the suppliers of the materials, it was established that the benzene originated from the use of t-butyl perbenzoate used as an initiator in the manufacture of the polymer. Samples of thermoset polyester made to the original formulations and thus contaminated with benzene showed migration levels of 1.9 and 5.6 mg/kg in olive oil after extraction for 1 hour at 175 degrees C. Migration levels into olive oil at 175 degrees C for samples produced with non-aromatic initiator were less than 0.1 mg/kg. Concentrations of benzene in thermoset polyester cookware purchased from retail outlets were 0.3 to 84.7 mg/kg. Low amounts of benzene (less than 0.01 to 0.09 mg/kg) were detected in foods when the articles were used for cooking in microwave or conventional ovens. Other plastics used for retail food packaging, such as polystyrene and PVC, which might utilise t-butyl perbenzoate catalyst, were also analysed for benzene. Levels were mostly below 0.1 mg/kg, with the highest amounts detected being from 0.2 to 1.7 mg/kg, predominantly in articles of expanded polystyrene.

Benzene↗

PubMed1995

Lipid-based fat substitutes.

Fats and oils account for 38% of the total calories in the diet of Western populations, especially in the U.S. They provide the most concentrated source of energy, 9 kcal/g of a triacylglycerol molecule compared with 4 kcal/g provided by carbohydrate and protein. In response to consumer demands for low-calorie or calorie-free fats and their reluctance to give up the taste of fat, current research efforts have been directed toward the development of lipid-like fat substitutes. These fat substitutes contain the fatty acids found in conventional fats and oils, with all the physical and organoleptic properties of fats, but provide few or no calories in the diet. Some of the fat substitutes are modified triacylglycerols (glycerol backbone) with reduced digestion and absorption; others are digestible and nondigestible carbohydrate fatty acid esters and polyesters, respectively. Sucrose polyester (Olestra), a sucrose molecule esterified with six to either fatty acids, is the most studied of the lipid-based fat substitutes containing a carbohydrate backbone. If approved by the FDA, sucrose polyester will find application in almost all fat-containing foods. Specialty fats or fat substitutes targeted to certain individuals with special needs are being developed. Among these are the medium-chain triacylglycerols and structured lipids (glycerol backbone), or ¿nutraceuticals¿ with reduced absorption and medical applications. Enzyme biotechnology is another tool available to lipid chemists to selectively modify, esterify, transform, transesterify, and interesterify fats and oils or synthesize new lipids such as structured lipids of food, nutritional, and medical importance. These designer fats may be the trend in the future to produce medical lipids that do not occur normally in nature. The different types of lipid-based fat substitutes are reviewed with respect to their synthesis, analysis, metabolism, potential applications/uses, and the future of fat substitutes.

Dietary Fats, Unsaturated↗

PubMed1994

Some biomechanical considerations in microsutures.

The purpose of this study was to measure the biomechanical performance for commercially available microsutures, nylon polypropylene, polyester, and polyglactin 910. The biomechanical performance was determined by reproducible, biomechanical parameters that included stiffness, elasticity, resistance to creep, secure knot construction, and knot breaking strength. On the basis of these comprehensive studies, the handling characteristics of the nylon microsutures were judged to be superior over the other microsutures. Knot security was achieved with a three-throw square (1 = 1 = 1) knot that allowed a preview of the ultimate apposition of the divided tissue. In addition, nylon microsutures were more supple than the other microsutures. The breaking strength of the knotted nylon microsutures was comparable with those of the knotted polyglactin 910 and polyester microsutures, and significantly greater than that of the knotted polypropylene sutures. Its resistance to creep was significantly greater than that of the polypropylene microsutures but less than those of polyglactin 910 and polyester microsutures.

Biomechanical Phenomena↗

PubMed1977

Pyroglyphid mites, xerophilic fungi and allergenic activity in dust from hospital mattresses.

Dust from mattresses of different composition and age was analysed for mites, xerophilic fungi and allergenic activity. The mites of the genus Demodex were the most abundant (58.2 per cent). Also pyroglyphid mites occurred commonly (36.6 per cent). Pyroglyphid mites were present in small numbers (mean: 1 specimen/0.2 g of dust) in 12 out of the 17 older polyester-foam mattresses. The 11 cotton-horsechair mattresses and the newly used polyester-foam mattresses (three tested) were without them. The dust from the cotton-horsehair mattresses had a significantly higher allergenic activity than from those of polyester-foam. Xerophilic fungi were isolated in three out of 31 mattresses. The species isolated belonged to the genus Aspergillus and Eurotium. E. repens occurred most frequently. Disinfection of mattresses was suggested to have a negative influence on the occurrence of mites and fungi.

Allergens↗

PubMed1993

Biocompatibility of leukocyte removal filters during leukocyte filtration of cardiopulmonary bypass perfusate.

To evaluate the biocompatibility and the efficacy of leukocyte removal filters, we performed a prospective study by using the cardiopulmonary bypass perfusate taken from the heart-lung machine for 20 patients who underwent cardiac surgery and were randomly divided into four groups according to the filters used. A leukocyte removal filter was installed in the transfusion line while the perfusate was transfused to the patients. No increases of C3a, C5a, elastase, and thromboxane were found during leukocyte filtration by polyester filters (Optima, Sepacell R500, and Pall RC100). Activation of the complement cascade was observed during filtration by the cellulose acetate filter (Cellselect) although the efficacy of the Cellselect filter was evidently higher than that of the polyester filter. These results imply that polyester leukocyte filters are superior to cellulose acetate filters in terms of biocompatibility but have a reduced efficacy. An optimal leukocyte filter providing both high efficacy and biocompatibility has yet to be developed.

Biocompatible Materials↗

PubMed1997

Myristoyl gelatin as a sealant for Dacron vascular prostheses.

Myristoyl gelatin (MG) retains its gel structure at temperatures above body temperature without any crosslinking. As a coating material, MG adheres well to polyester fibers, and the outermost layers of the sealant that are in contact with blood or surrounding tissue become hydrophilic. We produced MG-impregnated knitted Dacron vascular prostheses (MG graft [MGG]) and investigated the usefulness of MG as a sealant by replacing the thoracic aorta of dogs. MGGs (5 cm long with an inner diameter of 10 mm) were implanted in 5 mongrel dogs (10-20 kg), and the grafts were retrieved at intervals of 4 h and 2, 4, 8, and 15 weeks after grafting. There was no thrombus formation on the flow surface of the MGGs, indicating adequate antithrombogenic properties. No resorption of MG occurred until after 2 weeks, and neither immune reaction nor excessive foreign body reaction was noted. Fragmentation of the sealant induced by cell infiltration began to occur at 4 weeks, yet the sealing effect persisted. The organization of MGG was almost complete at 8 weeks. Because of its pliability and effective adhesion to polyester fibers, its antithrombogenicity, and the persistent sealing effect due to delayed biodegradation and resorption, we conclude that MG is an extremely useful sealant for polyester vascular prostheses.

Animals↗

PubMed2006

Evaluation of a wipe surface sample method for collection of Bacillus spores from nonporous surfaces.

Polyester-rayon blend wipes were evaluated for efficiency of extraction and recovery of powdered Bacillus atrophaeus spores from stainless steel and painted wallboard surfaces. Method limits of detection were also estimated for both surfaces. The observed mean efficiency of polyester-rayon blend wipe recovery from stainless steel was 0.35 with a standard deviation of +/-0.12, and for painted wallboard it was 0.29 with a standard deviation of +/-0.15. Evaluation of a sonication extraction method for the polyester-rayon blend wipes produced a mean extraction efficiency of 0.93 with a standard deviation of +/-0.09. Wipe recovery quantitative limits of detection were estimated at 90 CFU per unit of stainless steel sample area and 105 CFU per unit of painted wallboard sample area. The method recovery efficiency and limits of detection established in this work provide useful guidance for the planning of incident response environmental sampling following the release of a biological agent such as Bacillus anthracis.

Anthrax↗

PubMed1995

Substrate specificities of bacterial polyhydroxyalkanoate depolymerases and lipases: bacterial lipases hydrolyze poly(omega-hydroxyalkanoates).

The substrate specificities of extracellular lipases purified from Bacillus subtilis, Pseudomonas aeruginosa, Pseudomonas alcaligenes, Pseudomonas fluorescens, and Burkholderia cepacia (former Pseudomonas cepacia) and of extracellular polyhydroxyalkanoate (PHA) depolymerases purified from Comamonas sp., Pseudomonas lemoignei, and P. fluorescens GK13, as well as that of an esterase purified from P. fluorescens GK 13, to various polyesters and to lipase substrates were analyzed. All lipases and the esterase of P. fluorescens GK13 but none of the PHA depolymerases tested hydrolyzed triolein, thereby confirming a functional difference between lipases and PHA depolymerases. However, most lipases were able to hydrolyze polyesters consisting of an omega-hydroxyalkanoic acid such as poly(6-hydroxyhedxanoate) or poly(4-hydroxybutyrate). The dimeric ester of hydroxyhexanoate was the main product of enzymatic hydrolysis of polycaprolactone by P. aeruginosa lipase. Polyesters containing side chains in the polymer backbone such as poly (3-hydroxybutyrate) and other poly(3-hydroxyalkanoates) were not or were only slightly hydrolyzed by the lipases tested.

Amino Acid Sequence↗

PubMed1997

Plastination in the neurosciences. Keynote lecture.

Plastination is a unique technique of tissue preservation developed by Dr. Gunther von Hagens in Heidelberg, Germany, in 1978. In this process, water and lipids in biological tissues are replaced by curable polymers which are subsequently hardened, resulting in dry, odorless and durable specimens. In neuroanatomy silicone and polyester resins are used. Silicone rubber is used for whole brains and brain dissections resulting in natural looking specimens. Polyester resin is used for brain slices resulting in an excellent distinction between gray and white matter. The silicone S 10 standard technique and the polyester P 35 technique are described in detail. The advantages of plastinated specimens in neuroanatomy teaching and research are discussed.

Brain↗

PubMed2004

Biocompatibility studies of the Anaconda stent-graft and observations of nitinol corrosion resistance.

PURPOSE: To validate the deployment, in vivo performance, biostability, and healing capacity of the Anaconda self-expanding endoprosthesis in a canine aortic aneurysm model. METHODS: Aneurysms were surgically created in 12 dogs by sewing a woven polyester patch onto the anterior side of the thoracic or abdominal aorta. Anaconda prostheses were implanted transfemorally for prescheduled periods (1 or 3 months). Aneurysm exclusion and stent-graft patency were monitored angiographically. Healing was assessed with histological analysis and scanning electron microscopy (SEM). Textile analysis determined the physical and chemical stability of the woven polyester material, while the biostability of the nitinol wires was evaluated with SEM and spectroscopy. RESULTS: All prostheses were intact at explantation. After 1 month, endothelial-like cells were migrating in a discontinuous manner both proximally and distally over the internal collagenous pannus at the device-host boundary. After 3 months, endothelialization had reached the midsections of the devices, with a thicker collagenous internal capsule. Patches of endothelial-like cells were sharing the luminal surface with thrombotic deposits. However, the wall of the device at the level of the aneurysm was generally poorly healed, with multiple thrombi scattered irregularly over the luminal surface. The polyester fabric was intact except for some filaments that were ruptured adjacent to the sutures and some abrasion caused by the nitinol wires. No evidence of corrosion was found on the nitinol stents. CONCLUSIONS: This Anaconda stent-graft has demonstrated its ability to exclude arterial aneurysms. The device used in this study was an experimental prototype, and the manufacturer has incorporated new immobilization features into the model for clinical use. The constituent materials appear to be suitable in terms of biocompatibility, biofunctionality, and short-term durability.

Alloys↗