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At least 1,495 records · Page 83Linked to original sources

PubMed1997

Transvenous closure of secundum atrial septal defects: preliminary results with a new self-expanding nitinol prosthesis in a swine model.

BACKGROUND: Our purpose was to evaluate a new prosthesis for percutaneous closure of secundum atrial septal defects (ASDs). METHODS AND RESULTS: Percutaneous closure of surgically created fossa ovalis ASD was attempted in 15 minipigs. The mean balloon-stretched ASD diameter was 12.3+/-2.3 mm (range, 10 to 16 mm). The self-expanding prosthesis was braided from 0.005-in Nitinol wires in the shape of two flat buttons with a short connecting waist with a diameter corresponding to that of the defect to be closed. Polyester filling was added to enhance thrombogenicity. Pulmonary arteriography with levo-phase was obtained before placement; immediately after placement; and at 1-week, 1-month, and 3-month follow-ups. Four animals were killed at 1 week, 1 month, and 3 months for histopathological correlation. Three deaths resulted from ventricular fibrillation (one during anesthesia and two during the placement procedure). Successful placement of the prosthesis was achieved in the remaining 12 animals. Overall immediate ASD closure on angiography occurred in 7 of 12 animals (all polyester-filled prostheses). Absent or trace shunt by angiography was present in 11 of 12 devices at 1 week, with the remaining one demonstrating a small shunt. All septal defects were completely closed at 1 month with the exception of one case in which delayed partial dislodgment of an undersized prosthesis into the right atrium had developed. Closure rate at 3 months was 100%. Neoendothelialization and fibrous incorporation of the prosthesis were completed within 1 to 3 months. CONCLUSIONS: Effective and permanent occlusion of secundum ASDs is feasible with a device that offers the advantages of easy placement, self-centering, and repositionability.

Alloys↗

PubMed2003

Formation of gold nanoparticles within a liquid crystalline polymeric matrix.

We could prepare a novel composite consisting of a liquid crystalline polyester matrix and gold nanoparticles (7-14 nm). The polymer bears methoxy-terminated, hydrophilic, low molecular weight (350) PEG pendants on the rigid, hydrophobic aromatic polyester backbone. The polymers from a layered, sematic-like morphology at room temperature, where the interlayer is occupied by the PEG pendants. An aqueous solution of HAuCl4 was allowed to diffuse into the hydrophilic domains and the gold ions were reduced by hydrazine to gold nanoparticles. Our findings combine the concepts of self-assembly and nanoparticles, which can lead to formation of many interesting new nanocomposites.

Calorimetry, Differential Scanning↗

PubMed2004

Basement membrane-dependent modification of phenotype and gene expression in human retinal pigment epithelial ARPE-19 cells.

PURPOSE: To use porcine lens capsule (PLC) as basement membrane for ARPE-19 cells and to characterize its effects on cell differentiation and gene expression. METHODS: Postconfluent cultures of ARPE-19 cells were established on either porous polyester filters or PLC membranes and characterized by electron microscopy, immunocytochemistry, and transepithelial electrical resistance measurements. Metabolic activity was assessed by measuring phagocytosis of rod outer segments. mRNA populations of ARPE-19 cells grown on polyester and PLC membranes were compared by suppressive subtractive hybridization. Differentially regulated messages were subsequently identified by DNA sequencing and their altered expression confirmed by Northern or virtual Northern blot analysis. RESULTS: Culture of ARPE-19 cells on PLC membrane induced the formation of apical microvilli and the ability to phagocytose rod outer segments. These culture conditions also led to enhanced junctional distribution of ZO-1 and occludin, the formation of polarized membrane domains, and a significant increase in transepithelial resistance. Gene expression was significantly altered by growth on PLC membranes and 29 differentially expressed transcripts were identified. CONCLUSIONS: Culture of ARPE-19 cells on PLC membranes resulted in a more differentiated phenotype and in expression of a specific set of transcripts encoding protein products that may affect epithelial differentiation, polarity and survival.

Animals↗

PubMed1992

Trends in the development of bioresorbable polymers for medical applications.

The gradual shift from biostable prostheses to degradable, temporary implants represents one of the most significant trends in biomaterials research. In view of this trend, medical applications of degradable implant materials were reviewed with special emphasis on orthopedic polymeric implants. Among the polymeric implant materials derived from natural sources, collagen, various polysaccharides such as cellulose, and microbial polyesters have been intensively investigated. Among the synthetic, degradable polymers, aliphatic polyesters such as poly(glycolic acid), poly(lactic acid), poly(caprolactone) and polydioxanone, are most commonly investigated. Only recently, several new classes of polymers such as poly(ortho esters), polyanhydrides, and degradable polycarbonates have been introduced as potential implant materials. A particularly versatile group of new biomaterials with promising engineering properties are the "pseudo"-poly(amino acids), amino acid derived polymers in which conventional peptide bonds have been replaced by various chemical linkages.

Absorption↗

PubMed1995

Market study: biomaterials supply for permanent medical implants.

The withdrawal of DuPont as a supplier of key raw materials created a major dislocation in the medical device industry. We studied the present and future impact caused by the market removal of polyethylene terephthalate (PET) yarn ("Dacron"), polytetrafluorethylene (PTFE) fiber and resin ("Teflon"), and polyacetal resin ("Delrin"). Findings were: 1) Dollar values of the permanent medical implant markets for PET yarn, PTFE fiber and resin, and polyacetal resin are a minute fraction, of their values for their other commercial markets; 2) The implant market value is clearly not commensurate with the liability risk; and 3) The majority of these materials consumed by this market are used in the production of lifesaving, permanent medical implants [e.g., vital blood vessel replacements made from knitted polyester (PET)]. The remainder is used in life-enhancing, permanent implants [e.g., hernia patches made of polyester (PET) fabric].

Acetals↗

PubMed1996

Small caliber vascular grafts. Part II: Polyurethanes revisited.

Polyurethanes are considered to be one of the most bio- and blood-compatible biomaterials known today. By intelligent utilization of principles governing the structure/property relationship of these polymers, one can generate systems which resemble, in principle, the physical-mechanical behavior of living tissue. Thus, it is not surprising that these materials played a major role in development of small caliber vascular grafts targeted for vascular access, peripheral and coronary artery bypass indications. Numerous technologies, often esoteric in nature, were and are utilized to generate porous, potentially multilayered conduits possessing some or many characteristics of natural blood vessels. Properties such as durability, elasticity, compliance, pulsatility, and propensity for healing became attainable via polyurethanes. Furthermore, additional surface and/or bulk modification via attachments of biologically active species such as anticoagulants, cell proliferation suppressants, anti-infective compounds or biorecognizable groups are possible due to reactive groups which are part of the polyurethane structure. These modifications are designed to control or mediate host acceptance and healing of the graft. Finally, a myriad of practical processing technologies are used to fabricate functional grafts. Among those, casting, electrostatic and wet spinning of fibers and monofilaments, extrusion, dip coating or spraying of mandrels with polymer/additive solutions are often coupled with chemical-potential-difference-driven coagulation and phase inversion leading to grafts feeling and often behaving like natural vessels. Historically, the first polyurethanes utilized were hydrolytically unstable polyester polyurethanes containing hydrolysis-prone polyester polyols as soft segments, followed by hydrolytically stable but oxidation sensitive polyether polyols based polyurethanes. Polyether-based polyurethanes and their clones containing silicone and other modifying polymeric intermediates represented significant progress. Many viable technologies were discovered and developed using polyether-based polyurethanes. Chronic in vivo instability observed on prolonged implantation became, however, a major roadblock. The path led finally to the use of hydrolytically and oxidatively stable polycarbonate polyols as the soft segment to generate biodurable materials with resistance to biodegradation adequate for vascular access or perhaps peripheral graft indications. This biodurability needs to be further increased in order to utilize the full potential of polyurethanes in development of patent small caliber graft. Modification of both the soft and hard segments needs to be considered in order to maximize biodurability of both basic building blocks of the polyurethane. This paper reviews the achievements, discusses trends, and offers the view of the future in this exciting area of material/device combination.

Anti-Infective Agents↗

PubMed1997

Polyglycolide bioabsorbable screws in the treatment of ankle fractures.

Twenty-one patients with unstable medial malleolar, bimalleolar, or trimalleolar ankle fractures underwent open reduction and internal fixation of the medial malleolus with 4.5-mm polyglycolide screws. All lateral malleolar fractures were internally fixed with standard metallic implants. Radiographic and clinical follow-up results were available on 16 of 21 patients. All fractures healed at an average of 3.4 months (range, 3-6 months), and there were no medial wound infections. Eight of 16 patients developed an inflammatory reaction to the biodegradable polyester at 3 to 4 months after implantation, including one who developed a sterile draining sinus tract. No surgical or nonsurgical treatment was required in those eight patients. We conclude that whereas polyester screws yield union rates and functional results similar to those of metallic screws in the treatment of medical malleolar fractures, the use of polyglycolide screws is associated with an unacceptable rate of inflammatory reactions.

Adult↗

PubMed1998

Surgical gowns and drapes into the 21st century.

According to the MDD (Medical Devices Directive) 93/42/EEC of 13 June 1993, medical products including gowns and drapes must provide a high level of protection for patients, users and others. The European Commission CEN/TC 205/WG 14, under the leadership of its convenor, Professor Werner, is developing a mandatory European standard on the basic requirements and test methods for disposable and reusable materials for protection of patients, surgical personnel, and operating room facilities i.e. gowns and drapes. This European standard is intended to clarify the situation with respect to products and their properties, defining basic requirements, for users and manufacturers of medical products. Future use of standard cotton textiles and conventional cotton-polyester mixed textiles is uncertain as they may not meet the requirements of the new standard, i.e. resistance to penetration by microbiological microorganisms, liquids and particle release. However, there are innovative reusable barrier surgical drapes and gowns which meet the basic requirements of the standard made from liquid repellent micro-filament materials, material laminates and perhaps some specific cotton polyester materials which have been chemically modified. In the new standard based on CEN/TC 205/WG 14, quality assurance for reprocessing of surgical gowns and drapes is critical. The manufacturer/distributor must use validated processes to prove that the requirements of this European Standard are met. Quality Assurance Systems will be required to give proof of decontamination, disinfection and sterilisation. Specified processes are to be used to maintain the properties of the materials throughout reprocessing. It is the responsibility of the hospital to assure optimal protection of patients and users. In case of a lawsuit, this could lead to the burden of proof being shifted to the hospital, with related risk of liability because it is always assumed that the work is being done according to the 'state of the art'. Difficult situations arise when it must be proved that one has acted equivalent to or better than the standard procedures and that no mistakes are made. Because of this risk of liability alone, the question of what surgical materials are used in the future should be considered very carefully.

Consumer Product Safety↗

PubMed2006

Sequence analysis and structure prediction of type II Pseudomonas sp. USM 4-55 PHA synthase and an insight into its catalytic mechanism.

BACKGROUND: Polyhydroxyalkanoates (PHA), are biodegradable polyesters derived from many microorganisms such as the pseudomonads. These polyesters are in great demand especially in the packaging industries, the medical line as well as the paint industries. The enzyme responsible in catalyzing the formation of PHA is PHA synthase. Due to the limited structural information, its functional properties including catalysis are lacking. Therefore, this study seeks to investigate the structural properties as well as its catalytic mechanism by predicting the three-dimensional (3D) model of the Type II Pseudomonas sp. USM 4-55 PHA synthase 1 (PhaC1P.sp USM 4-55). RESULTS: Sequence analysis demonstrated that PhaC1P.sp USM 4-55 lacked similarity with all known structures in databases. PSI-BLAST and HMM Superfamily analyses demonstrated that this enzyme belongs to the alpha/beta hydrolase fold family. Threading approach revealed that the most suitable template to use was the human gastric lipase (PDB ID: 1HLG). The superimposition of the predicted PhaC1P.sp USM 4-55 model with 1HLG covering 86.2% of the backbone atoms showed an RMSD of 1.15 A. The catalytic residues comprising of Cys296, Asp451 and His479 were found to be conserved and located adjacent to each other. In addition to this, an extension to the catalytic mechanism was also proposed whereby two tetrahedral intermediates were believed to form during the PHA biosynthesis. These transition state intermediates were further postulated to be stabilized by the formation of oxyanion holes. Based on the sequence analysis and the deduced model, Ser297 was postulated to contribute to the formation of the oxyanion hole. CONCLUSION: The 3D model of the core region of PhaC1P.sp USM 4-55 from residue 267 to residue 484 was developed using computational techniques and the locations of the catalytic residues were identified. Results from this study for the first time highlighted Ser297 potentially playing an important role in the enzyme's catalytic mechanism.

Acyltransferases↗

PubMedDate not supplied

VACUTEX: a dressing designed for patients, tailored by nurses.

VACUTEX is a new rapid capillary action dressing comprising three layers: two 100% polyester filament outer layers, and a 65% polyester and 35% cotton woven inner layer. The outer surfaces are fused in such a way as to prevent micro fibres shedding within the wound bed. No two wounds are alike, and wounds are often located in difficult-to-dress areas. This article will describe how VACUTEX, when used with creativity, addresses many of the challenges of wound management.

Aged↗

PubMed2006

Concurrent gastric bypass and repair of anterior abdominal wall hernias.

BACKGROUND: Many patients seeking surgical treatment for morbid obesity present with anterior abdominal wall hernias. Although principles of hernia repair involve a tension-free repair with the use of prosthetic mesh, there is concern about the use of mesh in gastric bypass surgery due to potential contamination with the contents of the gastrointestinal tract and resultant mesh infection. We report our series of patients undergoing Roux-en-Y gastric bypass (RYGBP) and simultaneous anterior abdominal wall hernia repair. METHODS: All patients who underwent simultaneous RYGBP surgery and anterior abdominal wall hernia repair were reviewed. RESULTS: 12 patients underwent concurrent RYGBP and anterior wall hernia repair. There were 5 women and 7 men with average age 54.9 +/- 8.5 years (range 35 to 64) and average body mass index (BMI) 50.4 +/- 10.3 kg/m(2) (range 38 to 70). Two open and 10 laparoscopic RYGBP operations were performed. Nine patients (75%) underwent incisional hernia repairs and 3 patients (25%) underwent umbilical hernia repair concurrent with gastric bypass. Average size of defect was 14.7 +/- 13.4 cm(2). One patient had primary repair and 11 patients had prosthetic mesh repair: polypropylene in 3 patients (25%) and polyester in 8 patients (67%). With a 14.1 +/- 9.3 month follow-up, there have been no mesh infections and 2 recurrences, one in the patient who underwent primary repair and one in a patient repaired with polyester mesh but with two previous failed incisional hernia repairs. CONCLUSION: Concurrent RYGBP and repair of anterior abdominal wall hernias is safe and feasible. In order to optimize success, tension-free principles of hernia repair with the use of prosthetic mesh should be followed since no mesh infections occurred in our series.

Adult↗

PubMed1998

Radiolucent casting tape allows for accurate measurement of forearm bone mineral density using dual-energy X-ray absorptiometry.

The ability to perform dual-energy X-ray absorptiometry (DXA) while a patient is in a cast would give investigators the opportunity to follow early changes in bone mineral density (BMD, g/cm2) during fracture healing or to evaluate bone changes related to immobilization. The objective of this study was to determine if accurate and precise DXA scans could be obtained through polyester-based radiolucent casting tape (Delta-Cast Elite [DCE], Johnson & Johnson, Inc., Raynham, MA) and standard fiberglass casting tape (Delta Lite [DL], Johnson & Johnson, Inc.). DXA scans were performed using a Lunar DPXL densitometer. Standard forearm regions of interest were analyzed. Ten normal volunteers had three consecutive scans of their dominant arm with no cast, with a radiolucent (DCE) cast, and with a fiberglass (DL) cast. Precision was calculated using data from three volunteers (three scans each; no cast, DCE, DL). Results of DCE and DL were compared with results with no cast. In a second series, a spine phantom was placed inside rice-filled forearm casts and repetitively scanned; results with DCE and DL were compared with the mean BMD values for the phantom alone. Analyses of the scans through the DL casts were difficult because the radiodensity of the fiberglass interfered with edge detection. This problem was exacerbated by low BMD (i.e., scans for women). Edge detection was not a problem with the DCE scans. Although the group mean BMD values with in vivo no cast, DCE, or DL scans were similar for all regions of interest, the data obtained for ultradistal regions of interest with DL scans were less precise. BMD values for the fiberglass-encased phantom were significantly lower compared with no cast or DCE scans (p = 0.0002). This study demonstrates that it is possible to perform accurate and precise forearm DXA scans through polyester-based radiolucent DCE casting tape.

Journal Article↗

PubMed1998

Effects of two kinds of underwear on metabolic heat production during 60 min recovery after 30 min severe exercise in the cold.

The purpose of this study is to investigate the thermophysiological significance of hydrophilic and hydrophobic properties of underwear materials under the influences of profuse sweating produced during severe exercise in the cold. Two kinds of underwear were used: two layers of cotton underwear with two-piece long-sleeved shirt and full-trousers (C), and two layers of polypropylene underwear with two-piece long-sleeved shirt and full-trousers (P). In addition, the subject put on a two-piece ski suit of 100% polyester including 100% polyester padding. Eight adult females volunteered as subjects in this study. The test was performed in a climatic chamber at an ambient air temperature of 2 degrees C and an air velocity of 0.26 m.s-1. The subject exercised on a cycle ergometer at an intensity of 65% maximal oxygen uptake for 30 min and followed by 60 min recovery. The major findings are summarized as follows: 1) The fall of rectal temperature tended to be greater in P during the recovery. 2) The absolute humidity of innermost layer and middle layer was significantly higher in C than in P during the recovery, but the absolute humidity of middle layer and outermost layer was significantly higher in P than in C during the exercise. 3) Clothing microclimate temperature of innermost at back was significantly higher in C during the exercise and recovery. 4) Metabolic heat production for last 30 min during recovery was significantly higher in P. 5) The degree of skin wettedness sensation and sweating sensation for whole body was significantly higher in P during the exercise. It was concluded that the slower evaporation behavior by absorbing of underwear material in the clothing system has a beneficial influence on thermophysiological responses during severe exercise and its recovery in the cold, although the differences were very small.

Adult↗

PubMed2006

Preparation and certification of the new reference materials; plastics (disk form, JSAC 0621-0625) for determination of mercury using x-ray fluorescent analysis.

The Japan Society for Analytical Chemistry has developed some new plastic certified reference materials (CRMs) for the analysis of mercury in polyester disks using XRF analysis. These CRMs (named as JSAC 0621-0625) were prepared by casting polyesters including a toluene solution of organometallic compounds as a standard. Concentrations of the five levels of mercury ranged from 0 to 250 mg/kg. Homogeneity tests of prepared disks had shown excellent results. Interlaboratory comparison study for the certification was performed by 15 laboratory participants. The z-scores in robust statistical method was applied for the evaluation of outliers. The certified values were assigned after discarding outliers. The uncertainties of certified values were determined as the confidence levels of 95%.

Journal Article↗

PubMed2005

Efficacy of directed misting application of a peroxygen disinfectant for environmental decontamination of a veterinary hospital.

OBJECTIVE: To evaluate effectiveness of 4% peroxymonosulfate disinfectant applied as a mist to surfaces in a large animal hospital as measured by recovery of Staphylococcus aureus and Salmonella enterica serovar Typhimurium. DESIGN: Field trial. SAMPLE POPULATION: Polyester transparencies inoculated with bacteria. PROCEDURE: Polyester transparencies were inoculated with S aureus or S Typhimurium and placed in various locations in the hospital. After mist application of the peroxygen disinfectant, viable bacterial numbers were quantified and compared with growth from control transparencies to assess reduction in bacterial count. RESULTS: When applied as a mist directed at environmental surfaces contaminated with a geometric mean of 4.03 x 10(7) CFUs of S aureus (95% confidence interval [CI], 3.95 x 10(7) to 4.11 x 10(7)) or 6.17 x 10(6) CFUs of S Typhimurium (95% Cl, 5.55 x 10(6) to 6.86 x 10(6)), 4% peroxymonosulfate reduced the geometric mean number of viable S aureus by 3.04 x 10(7) CFUs (95% Cl, 8.6 x 10(5) to 1.7 x 10(6)) and S Typhimurium by 3.97 x 10(6) CFUs (95% Cl, 8.6 x 10(5) to 3.5 x 10(6)). CONCLUSIONS AND CLINICAL RELEVANCE: Environmental disinfection with directed mist application of a 4% peroxymonosulfate solution was successful in reducing counts of bacterial CFUs by > 99.9999%. Directed mist application with this peroxygen disinfectant as evaluated in this study appeared to be an effective and efficient means of environmental disinfection in a large animal veterinary hospital and would be less disruptive than more traditional approaches to intensive environmental cleaning and disinfection.

Aerosols↗

PubMed1992

Technical note: development of a duodenal cannula for sheep.

A single T-shaped duodenal cannula of silicone rubber with a gutter-type small inner flange was developed for sheep. The barrel of the cannula was 24 mm long with an internal diameter of 12 mm. A polyester surgical mesh (100 mm x 100 mm) was connected to the barrel of the cannula as an anchor. Fibrous tissues grew on the polyester mesh anchor and adhered firmly to the serosa of the intestine, thus leaving no gap and, hence, preventing any leakage of intestinal contents from the side of the fistula. The small (24 mm in diameter) and thin (3 mm in thickness) outer flange of the cannula became buried in the wool and prevented any mechanical disturbance of the cannula by the activity of the animal. The elasticity of the silicone rubber prevented distortion of the duodenum around the barrel of the cannula. No erosion of the tissue between the inner flange of the cannula and the mesh was seen in postmortem observations.

Animals↗

PubMedDate not supplied

Use of myxalin for improving vascular graft healing: evaluation of biocompatibility in rats.

Myxalin is a glycopeptide extracted recently from a gram-negative bacterium. It has blood anticoagulant properties and can enhance endothelial cell growth. With the ultimate objective of using this bioactive molecule to promote vascular graft healing, this study assessed its biocompatibility in vivo by comparing the cellular and immunological responses of gelatin-coated knitted polyester grafts with and without myxalin following implantation in the peritoneal cavity of rats for prescheduled periods of 3 days and 1, 2, and 4 weeks. A nongelatin-coated virgin polyester graft was included as the reference material. The biological response to gelatin alone was characterized by a slower rate of cellular infiltration into the implant, reduced collagen synthesis, and higher levels of acid phosphatase and esterase activity in the surrounding tissue. The addition of myxalin to this coating resulted in a significant reduction of hydrolase secretion in the tissue surrounding the implant and an enhancement of cellular ingrowth.

Acid Phosphatase↗

PubMed2005

Fatty acid profiles associated with microbial colonization of freshly ingested grass and rumen biohydrogenation.

Two in situ studies were conducted to examine the use of odd-chain fatty acid profiles to study microbial colonization of freshly ingested herbage in the rumen as well as fatty acid biohydrogenation. In the first study, fresh perennial ryegrass was subjected to a range of sample preparation methods before incubation in the rumen for 2 or 7 h. In the second study, fresh perennial ryegrass was chopped into 1-cm lengths and incubated in polyester bags in the rumen for 2, 8, and 24 h. After removal of bags from the rumen, 4 different washing methods, ranging from manual squeezing to machine washing, were applied. Fatty acids were extracted from washed residues and determined, as methyl esters, by gas chromatography. The main odd-chain fatty acids (with the exception of anteiso C(15:0)) were not found in fresh grass and were useful markers of the effects of incubation time, sample preparation method, and washing method on microbial colonization/contamination. The concentration of these and other odd-chain fatty acids increased with incubation time in both studies. The results indicate rapid and continued microbial colonization of freshly ingested forages, although patterns of odd-chain fatty acids did not reveal any further information about the types of bacteria-colonizing herbage. Principal component, biplot analysis provided a useful overall description of the processes of microbial colonization and degradation of plant fatty acids on fresh herbage incubated in the rumen. Bolus formation during mastication and ingestion results in extensive damage to herbage; none of the techniques (cutting, crushing, and drying/grinding) investigated in this work was able to replicate the effects of bolus formation in the animal. The study provided further evidence of loss of unfermented feed particles through polyester bag pores, especially when feeds are dried and ground. Biohydrogenation of the polyunsaturated fatty acids of fresh herbage was used principally by solid-associated bacteria to enable them to take up high levels of trans-11 C(18:1) and C(18:0) fatty acids. Although trans-11 C(18:1) was strongly associated with bacterial markers (odd- and branched-chain fatty acids), its precursor (cis-9, trans-11 C(18:2)) was not associated with bacterial variation, suggesting that its production in the rumen under these conditions was mainly extracellular.

Analysis of Variance↗