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PubMed2001

Leeds-Keio artificial ligament: a new concept for the anterior cruciate ligament reconstruction of the knee.

The features of the Leeds-Keio artificial ligament, which was developed as a collaborative project between the University of Leeds in the UK and Keio University, are introduced. The ligament is made of polyester, and has a mesh structure. The diameter of the polyester fibers is 22 microns. The ligament has a tensile strength sufficient for anterior cruciate ligament (ACL) reconstruction, and fatigue tests have shown satisfactory durability of the ligament. The stiffness of the Leeds-Keio artificial ligament is about 200 N/mm, which is similar to the natural ACL. A combination of a bone plug and stapling is used for the bone fixation, taking into consideration the strength in both the initial mechanical fixation and the long term fixation. From an animal study, it was shown that fibrous tissue was induced around the artificial ligament, and the collagen fibers became aligned in the longitudinal direction of the ligament. For the clinical experience, one-hundred and thirty five cases were reviewed. The Lachaman sign disappeared in 87.4%, and the pivot shift sign disappeared in 88.1%. Side-to-side difference of anterior displacement of the knee, measured with a KT-2000 knee arthrometer at 30 degrees of flexion, was less than 3 mm in 85.9%. More than 90% of the patients experienced full range of motion. Thus, from the clinical results, it can be concluded that reasonable stability was obtained with the operation. If the Leeds-Keio artificial ligament may not be the perfect substitute for the ACL, both experimental and clinical studies indicate that it represents a major forward step in the history of knee ligament surgery.

Animals↗

PubMed1978

The effect of the physiological environment on the mechanical properties of biomaterials in cardiovascular applications.

The long-term biocompatibility and physical performance of polymeric materials in the physiological environment depend both on adsorption and absorption processes. While the former has received significant attention in the literature, the latter has not been sufficiently appreciated. Accelerated testing of prosthetic devices in the wrong media and temperatures yield misleading information as exemplified by pumping bladders of heart assist devices and heart valves. Although glutaraldehyde-treated porcine heterograft heart valves performed better than expected in humans over a period of several years, physical degradations that have been observed may be associated with the breakdown of the cross-links. Appropriately selected smooth-surfaced biomaterials and hydrogels are far better suited for temporary blood contacting prosthetic applications such as left ventricular heart assist devices (LVADs) than polyester flocked fibril surfaces that result in the deposition of a thick layer of fibrin/cellular mesh with clot-like morphology with inherent dangers of loss of polyester fibrils, and the shedding of clots as the result of cyclic flexing of the pump bladders. With the proliferation of various medical devices, the possibility of increased litigations with secondary and tertiary liabilities involving not only physicians, surgeons, and device manufacturers, but also suppliers of materials and components, it is essential to select pertinent rather than complex test procedures.

Absorption↗

PubMed1983

Effect of blood microfilters on complement activity in human plasma.

While many devices that come into direct contact with patients' blood have been shown to be safe with respect to their effects on the cellular components and coagulation system of blood, many have not been examined with respect to their potential to activate the complement system. We present evidence that suggests that a combination of nylon plus polypropylene, and a combination of polyester plus polypropylene, found in blood microfilters used to protect patients from gaseous and particulate embolism during cardiopulmonary bypass, produce significant (p less than 0.01, p less than 0.05, respectively) C3a generation during incubation in heparinized plasma. Filter mesh composed of nylon plus polypropylene produced significantly more (p less than 0.01) C3a than the polyester plus polypropylene combination.

Animals↗

PubMed2004

Swab materials and Bacillus anthracis spore recovery from nonporous surfaces.

Four swab materials were evaluated for their efficiency in recovery of Bacillus anthracis spores from steel coupons. Cotton, macrofoam, polyester, and rayon swabs were used to sample coupons inoculated with a spore suspension of known concentration. Three methods of processing for the removal of spores from the swabs (vortexing, sonication, or minimal agitation) and two swab preparations (premoistened and dry) were evaluated. Results indicated that premoistened swabs were more efficient at recovering spores than dry swabs (14.3% vs. 4.4%). Vortexing swabs for 2 min during processing resulted in superior extraction of spores when compared to sonicating them for 12 min or subjecting them to minimal agitation. Premoistened macrofoam and cotton swabs that were vortexed during processing recovered the greatest proportions of spores with a mean recovery of 43.6% (standard deviation [SD] 11.1%) and 41.7% (SD 14.6%), respectively. Premoistened and vortexed polyester and rayon swabs were less efficient, at 9.9% (SD 3.8%) and 11.5% (SD 7.9%), respectively.

Anthrax↗

PubMed1977

Central nervous defects in two children of mothers exposed to chemicals in the reinforced plastics industry. Chance or a causal relation?

With the use of a specially designed questionnaire, with the emphasis on occupational exposure to chemical agents at work, a case-referent study was started on 1 June 1976. The series comprised mothers of all children with central nervous defects notified to the Finnish Register of Congenital Malformations and their matched-pair referents. Information was gained by personal interview. By 1 March 1977 information had been gathered from 43 cases and their referents. Two case mothers had been employed in the reinforced plastics industry and had been exposed at work to a combination of styrene, polyester resin, organic peroxides, and acetone. When the number of fertile women in this industry is considered (some 250), along with the low rate of anencephaly and hydrochephalus in the general population--diagnoses made of the children of these case mothers (0.5/1,000 live births in Finland)--this occupational group is strongly overrepresented in the material. The paper is a more-detailed report regarding the two cases. Moreover a third case is mentioned in which the pregnant mother, a juvenile diabetic, had been exposed at home to styrene, polyester resin, and organic peroxides.

Abnormalities, Drug-Induced↗

PubMed1998

[NiTi shape-memory alloy cramp used in repair of skull defect].

Fixation of silicon-polyester fiber network on skull defect was usually difficult to handle and the fixation was unstable. In order to solve these problems, NiTi shape-memory alloy cramp was adopted and 101 patients with skull defects were selected for this clinical trial. Among them, there were 79 males and 22 females, and the age ranged from 12-55 years old. The area of skull defect ranged from 3 cm x 4 cm to 10 cm x 16 cm. All of these patients received repairing of the skull defects by silicon-polyester fiber network which was fixed by NiTi memory alloy cramps. After operation, there was no complication. One hundred patients were followed up for 1-8 years, in which 97 cases returned to their normal work, and only 2 cases had a transient dysfunction of frontal muscle for 2 months. In addition, There were no loosening of the cramps, displacement of plastic network and malignant degeneration. The NiTi shape-memory alloy cramps had the following advantages: 1. Simple operative procedure; 2. Rigid fixation; 3. Mild postoperative tissue reaction; 4. Few postoperative complication; 5. Favorable effect of skull repair; 6. No interference with CT and MRI image; 7. No carcinogenicity.

Adolescent↗

PubMed2000

Use of a batch-stirred reactor to rationally tailor biocatalytic polytransesterification.

Despite favorable thermodynamics, high-molecular weight and low-dispersity polyesters are difficult to synthesize biocatalytically in organic solvents. We have reported previously that the elimination of solvent can improve the kinetics and apparent equilibrium significantly (Chaudhary et al., 1997a). We now present the design and use of a batch-stirred enzyme reactor to control the biocatalytic polymerization. Using the reactor, polyester having a molecular weight of 23,400 Da and a polydispersity of 1.69 was synthesized in only 1 h at 60 degrees C. Additional factors like enzyme-deactivation kinetics, enzyme specificity, and initial exothermicity were investigated to develop a better understanding of this complex reaction system.

Bioreactors↗

PubMed1999

Laboratory evaluation of lambda-cyhalothrin a microencapsulated formulation on mosquito nets for control of vector mosquitos.

Two formulations of lambda-cyhalothrin (EC-Emulsion concentrate and MC-Microencapsulated) were impregnated into bednets made of polyethylene and polyester. The nets were treated at a dosage of 15 mg/m2. For bioassay of insecticidal efficacy, female Anopheles maculatus and Aedes aegypti were exposed to the nets for two minutes and mortality was scored 24 hours later. The nets were also tested after repeated washings with water and with soap and water. Microencapsulated (2.5CS) formulation was more effective than emulsion concentrate (2.5EC) formulation on both net materials--polyethylene and polyester. Repeated washing with water and soap reduces the efficacy of all bednet treatment combinations. Microencapsulated formulation on polyethylene gave best results; it could sustain up to five washes with water and two with soap and water.

Aedes↗

PubMed2000

Sutureless intraluminal graft for repair of high abdominal aortic aneurysm.

The aim of our study was experimental and clinical assessment of bifurcated grafts with ring on its main branch made of the same polyester as the prosthesis. This type of prosthesis facilitates quick anastomosis with the aorta through tying the aortic wall on the ring using a polyester tape. Experimental studies carried out on 18 pigs demonstrated good healing up of such a graft. The prosthesis was used for surgery in 8 patients with abdominal aneurysm which required clamping the aorta above renal arteries. The prosthesis was found to facilitate and accelerate making the proximal anastomosis, diminish the amount of blood loss, and reduces the time of the surgery, especially the time necessary for clamping the aorta above renal arteries which prevents renal ischaemia.

Aged↗

PubMed2001

[Progress on the biosynthesis of medium-chain-length polyhydroxyalkanoates by microorganisms].

Polyhydroxylkanoates(PHAs) are a class of polyesters produced as reserve materials by a large number of microorganisms under metabolic stress. The most fascinating feature of PHAs is its degradability, and which is supposed to take place of the traditional plastics made from petroleum in the future. PHAs are divided into two classes: short-chain-length PHAs(scl-PHAs) and medium-chain-length PHAs. mcl-PHAs is more welcome owing to its more wide crystallinity and higher extension to break than scl-PHAs, especially when some kind of new functional groups were incorporated into the side chain of the polyester. Since Psedumonas oleovorans is the most typical microorganism to produce mcl-PHAs, here the author summarized how P. oleovorans synthesize the mcl-PHAs and the production of mcl-PHAs by fermentation and give some of the idea about the future research of this field.

Acyl Coenzyme A↗

PubMed1999

The effects of fabric air permeability and moisture absorption on clothing microclimate and subjective sensation in sedentary women at cyclic changes of ambient temperatures from 27 degrees C to 33 degrees C.

The present paper aimed at learning the effects of two different levels of air permeability and moisture absorption on clothing microclimate and subjective sensation in sedentary women. Three kinds of clothing ensemble were investigated: 1) polyester clothing with low moisture absorption and low air permeability (A clothing); 2) polyester clothing with low moisture absorption and high air permeability (B clothing); and 3) cotton clothing with high moisture absorption and high air permeability (C clothing). After 20 min of dressing time, the room temperature and humidity began to rise from 27 degrees C and 50% rh to 33 degrees C and 70% rh over 20 min, and it was maintained for 30 min (Section I); it then began to fall to 27 degrees C and 50% rh over 20 min, and it was maintained there for 20 min (Section II). The subject sat quietly on a chair for 110 min. The main findings are summarized as follows: 1) The clothing surface temperature was significantly higher in C clothing than in B clothing during section I, but it was significantly higher in B clothing than in C clothing during section II. 2) Although the positive relationship between the microclimate humidity and forearm sweat rate was significantly confirmed in all three kinds of clothing, the microclimate humidity at the chest for the same sweat rate was lower in C clothing than in A and B clothing. These results were discussed in terms of thermal physiology.

Adult↗

PubMed2002

[Development of better tolerated prosthetic materials: applications in gynecological surgery].

UNLABELLED: Meshes have come to be widely used for surgical repair of the dysfunctional pelvic floor. The problem to date has been mesh intolerance. History. The first meshes were made with silver filigrees or stainless steel. Non-metallic and non-absorbable synthetic prostheses include nylon, silastic, polytetrafluoroethylene as well as expansive polyester and polypropylene forms. Most of the absorbable prostheses are made of polyglycolic acid and polyglactine 910. Classification. Four groups of biomaterials can be described according to pore size. Mechanical and biological properties. The mechanical properties of meshes have been tested industrially for resistance, pliability, elasticity and ductile qualities. These properties depend on type of tissue structure (woven or knitted) and the type of fiber used (mono and multi-filaments). The goal is to obtain a "silent" material, i.e. a material which does not trigger a host tissue reaction. Introducing the foreign body induces a "scarring" response. This fibroblastic reaction replaces the inflammatory reaction, leading to progressive colonization of the prosthesis. The major risk is infection caused by a disturbance of the inflammatory phase and bacterial development. Bacteria can be trapped in fibrotic tissue, with the risk of delayed infection. Immunological reactions may have an additive effect. These problems are not encountered with absorbable meshes. An ideal implant material must: not undergo physical modification by tissue fluids, be chemically inert, not trigger inflammatory or foreign body cell response in body tissues, be noncarcinogenic and nonallergenic, be capable of resisting mechanical stress and sterilization, and be able to be manufactured in the necessary shape. Polyester, polypropylene and expansive polytetrafluoroethylene fulfill these criteria. The ideal mesh. Eleven criteria are proposed. Complications for hernia repair. Infection and seroma are the most frequent complications with micro-porous meshes. Macro-porous meshes can cause erosive phenomena and adhesions. Retraction of synthetic tissues is observed in 20 to 30% of cases. Meshes in gynecology. In gynecology surgery, meshes made their first appearance in trans-abdominal sacrocolpopexy and slings. A detailed review of complications found in 32 articles studying slings and 22 studying sacrocolpopexy with approximately 10 types of meshes shows that intolerance of slings has oscillated between 1% with Prolene and 31% with Gore-Tex; for abdominal sacrocolpopexy the rate was between 1.7% with Prolene and 20% with Teflon. Rejection phenomena appear during the first year and are proportional to the surface area of the synthetic tissue and the proximity of the vaginal scar. New materials have been proposed over the last ten years for prolapse surgery, notably for cystocele, which accounts for 70% of all repair procedures. Nearly fifteen studies have reported a level of intolerance reaching 6%, the large majority of the meshes used being Prolene meshes. Our personal experience with 87 repair procedures has led us to the conclusion that Prolene is the most adapted mesh, allowing free tension between the bladder and the anterior vaginal wall. CONCLUSION: Continuous evaluation is needed to study these replacement materials which should in theory, improve the rate of recurrence, which is at present 20% with classic procedures not using a mesh.

Absorbable Implants↗

PubMed1992

[Tutoplast-Dura and Zenoderm-Corium implant--materials for tissue replacement. Experimental studies].

The results of experimental studies with the use of two biostatic materials: solvent-preserved human dura mater (Tutoplast-Dura--Pfrimmer-Vigo) and lyophilized porcine dermis (Zenoderm-Corium implant--Ethicon) as prosthesis of deficient, abdominal wall tissue are submitted. The studies were performed on an animal model and consisted on the evaluation of mechanical and biological qualities of the investigated materials as well as their surgical handiness and tissue tolerability. The application of knitted polyester net as a reinforcing agent for both materials was also estimated. Process of incorporation of the prosthetic material was investigated macroscopical at 3, 6 and 12 weeks after the implantation. The experimental trials revealed the usefulness of Tutoplast-Dura and Zenoderm-Corium implant in reconstructive surgery in account of their good biocompatibility and adequate, mechanical properties. It was stated that Tutoplast-Dura was characterized by remarkably better surgical handiness in comparison to Zenoderm-Corium implant. Additional mechanical reinforcement with polyester net was not necessary.

Abdominal Muscles↗

PubMed2004

Microbial polyhydroxyalkanoates (PHAs): an emerging biomaterial for tissue engineering and therapeutic applications.

Among the various biomaterials available for tissue engineering and therapeutic applications, microbial polyhydroxyalkanoates (PHAs) offer the most diverse range of thermal and mechanical properties. Of particular interest are the PHAs that contain 4-hydroxybutyrate such as poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB) and poly(4-hydroxybutyrate) [P(4HB)]. These polyesters can only be synthesized by a few types of bacteria, among which Comamonas acidovorans has the most efficient metabolic pathways to channel 4HB monomers. The resulting polyesters are bioabsorbable and are being developed as a new biomaterial for medical applications. By controlling the molar ratio of the monomers, it is possible to produce materials that are as tough and elastic as rubber.

3-Hydroxybutyric Acid↗

PubMed2005

[The tape for pulmonary artery banding].

Pulmonary artery banding remains a useful procedure for special conditions. A 3-month-old girl diagnosed as Down syndrome with atrioventricular septal defect underwent pulmonary artery banding. We used polyester tape smeared with Bone Wax for this pulmonary artery banding. After 7 months period, the tape was easily dissected from surrounding tissue and removed at radical operation. Microscopic appearance showed that the tape was intact and no evidence of inflammation or mineralization. We believe Bone Wax smeared polyester tape accomplishes well as silicone impregnated one.

Biocompatible Materials↗

PubMed2005

[In-vitro phantoms for estimating diffusion tensor tractography].

No literature has reported on in-vitro diffusion tensor tractography, although it is a useful method to visualize neuronal fiber projections in the living human brain. We applied this technique to phantoms of asparagus stems and bundled polyester yarn, and obtained tractography with high-quality images. On the asparagus stem phantom, straight tracts along the axis were displayed. On the polyester phantom, these tracts followed the course of the bundle whether it was straight or curved. These phantoms are useful for in-vitro evaluation of diffusion tensor tractography.

Algorithms↗

PubMedDate not supplied

[Modifications in the abdominal wall after prostheses implant in guinea pigs. Experimental preliminary study].

The treatment of giant incisional hernias is often not possible without the use of alloplastic materials (prostheses, meshes). Some of the modern prostheses seem to be quite "biocompatible" from the chemical point of view, but, the manner of using them is associated with certain complications (infection, seroma formation, intestinal obstruction, digestive fistula and failure of the repair). This preliminary experimental study on Guinea pigs had as a purpose the evaluation of the prostheses incorporation in the abdominal wall, the appearance of specific complications and the need of the biomaterial fixation. The macroscopic and microscopic study used 59 Guinea pigs, utilizing polypropylene (Marlex) and polyester (Mersilene and Plastex) prostheses, implanted pre-peritoneal and intraperitoneal, with or without fixation. The lack of incorporation of the prostheses was observed especially with the Plastex mesh (7 cases). Intestinal adhesions have been the rule after intraperitoneal implant of the prostheses; we registered a case of intestinal obstruction and a case of digestive fistula. Concluding, it is recommended the utilization of quality prostheses, especially polypropylene (Marlex) and no longer use of the Romanian polyester mesh (Plastex) which has obvious "biocompatible" problems. The intraperitoneal implant of the prostheses is not indicated. Adequate anchoring af the biomaterials prevents the subsequent migration.

Abdominal Muscles↗

PubMed1991

Metabolism of poly(3-hydroxyalkanoates) (PHAs) by Pseudomonas oleovorans. Identification and sequences of genes and function of the encoded proteins in the synthesis and degradation of PHA.

Pseudomonas oleovorans accumulates poly(3-hydroxyalkanoates) (PHAs) after growth on medium chain length hydrocarbons. Large amounts of this polyester are synthesized when cells are grown under nitrogen-limiting conditions. When nitrogen is resupplied in the medium, the accumulated PHA is degraded. In this paper, we describe mutants which are defective in the synthesis or in the degradation of PHA. These mutants were used to select DNA fragments which encode PHA polymerases and a PHA depolymerase. A 25-kilobase (kb) DNA fragment was isolated from P. oleovorans that complements a Pseudomonas putida mutant unable to accumulate PHA. Subcloning resulted in the assignment of a 6.4-kb EcoRI fragment as the pha locus, containing genetic information for PHA synthesis. Mutants in the PHA degradation pathway were also complemented by this fragment, indicating that genes encoding PHA biosynthetic and degradative enzymes are clustered. Analysis of the DNA sequence of the 6.4-kb fragment revealed the presence of two open reading frames encoding PHA polymerases based on homology to the poly(3-hydroxybutyrate) polymerase from Alcaligenes eutrophus. A third open reading frame complemented the PHA degradation mutation and is likely to encode a PHA depolymerase. The presence of two PHA polymerases is due to a 2098-base pair DNA duplication. The PHA polymerases are 53% identical and show 35-40% identity to the poly(3-hydroxybutyrate) polymerase. No clear difference in specificity was found for the PHA polymerases. However, with the pha locus cloned on a multicopy vector, a polymer was accumulated that contains a significantly higher amount of substrate-derived monomers. An increase in the rate of polyester synthesis versus oxidation of the monomers in the beta-oxidation explains these findings.

Acyltransferases↗