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PubMedDate not supplied

Characterisation of a polyester material for biomedical applications.

The characterisation of a polyester material for cardiovascular applications can be carried out to various levels of sophistication. This paper focuses on certain methods which could give information about important aspects of material characterisation such as chemical identity, molecular parameters, surface studies, extraction studies, removal of oligomers, mechanical properties and thermal properties. Significance of the results obtained from such analyses are also discussed.

Biocompatible Materials↗

PubMed1980

Study of some hepatic effects (induction and toxicity) caused by occupational exposure to styrene in the polyester industry.

This study describes an occupational health survey carried out in the polyester industry in order to investigate the hepatic effects caused by exposure to styrene. Fifty-seven workers underwent a medical examination. They were submitted to blood and urine sampling for the determination of the degree of exposure, by the analysis of urinary mandelic and phenylglyoxylic acids (styrene metabolites), and the intensity of induction and/or hepatic effects, by the analysis of urinary glucaric acid and plasma enzyme activities (gamma glutamyl transferase, ornithine carbamoyl transferase, alanine aminotransferase, and aspartate aminotransferase). The results showed that styrene does not give rise to measurable autoinduction. With regard to the hepatic tests, exposure to styrene caused an increase in the plasma enzyme activities, a phenomenon illustrating a possible damaging effect on liver cells. This effect appears with exposure below 100 ppm (time-weighted average).

Adult↗

PubMed1975

[Polyester tendon for atraumatic cervical suture during pregnancy].

There are presented the attempts of operative treatment of so called habitual abortions resulting from uterine cervix insufficiency. Two groups of operations were distinguished, based on the methods of Shirodkar and McDonald. Advantages and disadvantages of these operations, and their modifications used in obstetrical clinical practice are discussed. The importance of the selection of suitable material for the suture was pointed out. The authors developed an atraumatic needle provided with a polyester tendon. There are shown advantageous clinical resutls in 56 patients, out of whom 48 have given birth to viable children. Abortions occurred in 3 cases, premature deliveries in 3 and immature deliveries in 2.

Female↗

PubMed1975

[Comparative study of 4 types of polyester arterial prostheses].

The authors report a comparative study of 4 types of arterial prosthesis made of polyester. After implantation in the dog, the superiority of unfolded Rhodergon velvet prostheses was shown. They have excellent qualities for tissue reconstruction owing to presence of histological structures characteristic of large caliber arteries and absence of histological changes and hemorrhagic suffusion after the 12 th month following insertion.

Animals↗

PubMed2001

[IR studies on hydrogen bonding in hard segment domains of segmented polyester polyurethaneurea].

Hydrogen bonding in hard segment domains of segmented polyester polyurethaneurea (PUU) based on 4,4'-diphenylmethane diisocyanate (MDI), ethylene diamine (ED) and polybutylene adipate (PBA) (M.W.1,975 and M.W.1,228) was studied by means of IR spectroscopy. It was found that the double peak absorption of urea C=O groups occurred in the studied PUU with the increase of hard segment content. Two hydrogen bonding models of urea C=O groups in different hard segment sequence lengths of PUU were proposed. Three dimensional hydrogen bonding in hard segment domains can be formed by further bonding of the above planar hydrogen bondings.

Hydrogen Bonding↗

PubMed1976

Ethibond--a new polybutylate coated polyester suture.

This paper describes a new plastic polymer coating, polybutylate (polytetramethylene adipate), which, when applied to braided polyester fibre produces a new suture material--Ethibond. The advantages of this new suture material are improved handling properties, reduced tissue drag and minimal tissue reactivity. The paper details the physical and biological properties of the material.

Animals↗

PubMed2006

[FTIR research on the modification of plant oil pitch binders by polyester waste].

Various plant oil pitchs (cottonseed pitch, bean oil pitch, and mixed plant oil pitch) were used to prepare the plant oil pitch binders for casting. They were treated by polyester waste and processed by several technics such as esterifying. In the mean time, FTIR and TG were adopted to learn the structure, property, and sclerous mechanism of the binders. From the comparison with synthetic fat binder, the authors can see that the treated binders have similar components. They also have many excellent properties such as higher dry tensile strength and slower deflation velocity, which equal to or even exceed the properties of synthetic fat binder. Therefore, the treated binders, which were cheaper, can be used to make class I mold and core binders.

English Abstract↗

PubMed1990

Inadequacy of a polyester (Mersilene) suture for the reduction of astigmatism after penetrating keratoplasty.

Through two prospective studies, we evaluated the use of polyester (Mersilene) sutures in penetrating keratoplasty. Study 1 was a randomized comparison of combined running and interrupted Mersilene and nylon sutures (n = 45). Study 2 was a case series of single running Mersilene with postoperative adjustment of suture tension to manage astigmatism (n = 23). Study 1 demonstrated that Mersilene interrupted sutures were 5.5 times more likely to have handling-related complications compared to nylon (P = 0.01); in addition, they were 3 times as likely to have tissue-related complications as nylon interrupted sutures (P = 0.16). Study 2 demonstrated a complication rate of 69% when Mersilene was used as a single adjustable running suture. At 6 months postoperatively, the median refractive astigmatism for the adjustable cases was 3.37 D (mean, 4.03 +/- 2.37 D). Eyes in Study 2 with significant suture-related complications were 2.85 times more likely to have greater than 4 D of refractive astigmatism than were eyes without suture-related complications. We concluded that Mersilene is an undesirable suture for use in penetrating keratoplasty.

Adult↗

PubMed1987

Detection and measurement of a cellular immune-reactivity towards polyester and polytetrafluoroethylene grafts. Leukocyte adherence inhibition test.

Several studies were performed on polyester (Dacron) and polytetrafluoroethylene (PTFE) vascular substitute thrombogenicity. However, to date, the host-graft interactions have yet to be studied from an immunological point of view. For this reason, 4 classes of 10 patients each (Class 1: Dacron-+PTFE-grafted patients, Class 2: Dacron-, Class 3: PTFE-, and Class 4: controls) were submitted to a cellular immune-reactivity test: leukocyte adherence inhibition (LAI), in which leukocytes fail to adhere to glass on contact with a sensitizing antigen. The following blood cell populations were used: total leukocytes (PBL), mononuclear cells (MNC), T and B lymphocytes. This research demonstrated that a T cellular immune-reactivity towards Dacron and PTFE respectively occurs in Dacron- and PTFE-grafted patients, and that this reactivity is greater in the case of Dacron. More studies are required to determine the immuno-competent system role in fabric prosthesis patency.

Adult↗

PubMed1987

Per-operative uncontrollable bleeding at polyester (Dacron) arterial prosthesis implantation.

An aortobifemoral knitted polyester graft was placed in a 58-year-old woman with aorto-iliac occlusive disease. Although the prosthesis was preclotted in the usual manner, it never became impervious to blood under normal intra-arterial pressure. Examination of the graft showed lipid infiltration not ordinarily seen. We recommend that when a knitted prosthesis fails to preclot a woven graft should be used instead.

Blood Coagulation↗

PubMed1988

Fate of polyester arterial prostheses implanted as thoraco-abdominal by-passes in dogs: haematology, pathology, and biochemistry.

This study was designed to evaluate the haematological, pathological and biochemical characteristics of the flow surface in polyester arterial prostheses. Their implantations as thoraco-abdominal by-passes in dogs were scheduled to remain in place for periods ranging from four hours to six months. The haematologic parameters of the hosts were evaluated before implanting the prostheses and before harvesting the graft. To quantify the thrombogenicity of the flow surface, the platelet deposition and fibrinogen uptake were measured by means of an isotopic technique involving Indium-III labelled platelets and iodine-125 labelled fibrinogen. Synthesis of prostacyclin (PGI2) and thromboxane (TXA2) by the internal capsulae was determined by radioimmunoassay. The pathology was assessed according to previously described protocols. The haematologic parameters of the hosts did not alter substantially in the presence of the prostheses. The observed changes, though slight, were not pathologically significant 48 hours after implantation. Platelet and fibrin deposition was highest on the luminal surface of the prostheses 24 hours post-implantation. These decreased and became negligible after one month when the flow surface became smooth and glistening. The PGI2/TXA2 ratio of the luminal surface was much lower than that observed in native aortic tissue. These results show that the large calibre Dacron vascular prosthesis has a flow surface with a low degree of blood compatibility. The concentration of PGI2 on the newly-formed luminal surface remained low. This characteristic and the incomplete endothelialization of the luminal surface might be among the main factors that determine the high failure rate of synthetic prostheses when used as small diameter blood conduits.

6-Ketoprostaglandin F1 alpha↗

PubMedDate not supplied

[Comparative studies of the response of normolipemic and dyslipemic aged subjects to 2 forms of delayed-action nicotinic acid polyesters. Pentaerythrotol tetranicotinate and inositol hexanicotinate. Results of a controlled cross-over trial].

A cross-over trial was run to compare the effects of two delayed-action nicotinic acid polyesters (pentaerythritol-tetranticotinate, PETN, and inositol-hexanicotinate, MIEN) in 59 aged normo- and dyslipaemic subjects. PETN tended to normalise the lipid picture in much the same way as nicotin acid, without a drastic effect on circulating lipids and lipoproteins. MIEN, on the other hand, had only a slight effect on total blood lipids, and appeared to be ineffective or negative with respect to the other lipid parameters. PETN proved capable of releasing active concentrations of nicotinic acid in vivo for a period of time that was sufficient to correct hyperlipaemia in age subjects. The side-effects were slight, infrequent and quickly reversible.

Age Factors↗

PubMed1985

Does the non-absorbable fat, (sucrose polyester), interfere with the intestinal absorption of vitamin A?

Sucrose polyester (SPE) is a synthetic non-absorbable lipid. The effect of SPE on vitamin A absorption was determined by monitoring the disappearance rate of radio-labeled vitamin A from the jejunal perfusate of the rat. The relative distribution of radio-labeled vitamin A between the micellar phase and the perfusate containing SPE was determined. With SPE concentrations of 5, 10 and 20 g/l, vitamin A was concentrated in the SPE phase over the micellar phase by a factor of 4.4, 9.4, 19.8 respectively. Thus, vitamin A favored the SPE phase over the micellar phase in the distribution analysis. In vivo absorption experiments with SPE and non-SPE perfusates showed decreased net vitamin A absorption rates in the presence of SPE by 8.7% Thus, dietary ingestion of SPE results in some impairment of intestinal absorption of vitamin A, and may require vitamin A supplementation.

Animals↗

PubMed1973

Nonstainable polyester film, Cronar, for electrophoresis of plasma lipoproteins.

The Photo Products Department of E. I. du Pont de Nemours has recently made available a new type of polyester film, Cronar, for use in the electrophoretic separation of plasma lipoproteins. This film does not take up lipid dyes. There is no background color. The film remains clear and transparent after staining for lipoproteins.

Electrophoresis↗

PubMed1984

Studies with sucrose polyester.

Sucrose polyester (SPE) is a lipid synthesized from sucrose and fatty acid methyl esters. SPE has physical and organoleptic properties that closely resemble triglycerides, but it is not hydrolysed in the intestine and therefore not absorbed. By providing a persistent lipophilic phase in the intestine, SPE reduces the absorption of lipophilic substances such as cholesterol. SPE leaves the stomach more rapidly than triglyceride oils, presumably because of the absence of an effect on duodenal receptors. In studies with obese subjects, dietary SPE reduced total and LDL cholesterol by reducing the absorption of cholesterol from the intestine. In a study, in which SPE was covertly substituted for dietary fat, ten obese subjects in a weight-loss regimen did not increase dietary intake to compensate for the energy removed from the diet by SPE substitution. In a similar study with five naive, obese subjects, the investigators concluded that the mean energy intake decrease during SPE treatment [184 (769 kJ) kcal/d] was not significant. SPE continues to be studied as a means of reducing energy intake.

Cholesterol↗

PubMed1981

Biodegradable drug delivery systems based on aliphatic polyesters: application to contraceptives and narcotic antagonists.

The classes of polymer which form the basis of different types of drug delivery systems are discussed, and the relationships between the chemical structure of the polymer and its permeability, morphology, biodegradability, and mechanical properties are considered, using polyesters as specific examples. Studies of the permeability and biodegradability of poly epsilon-caprolactone), poly(DL-lactic acid), and various copolymers are described and used to illustrate how these properties may be varied by the choice of polymer structure. An induction period prior to bioerosion of these polymers, coupled with high permeability, permits their use as reservoir devices (capsules) which exhibit constant, diffusion-controlled drug release rates and which erode after the drug is exhausted. The applications of this approach to the long term delivery (1 year) of levonorgestrel, a contraceptive agent, and the short term delivery (1-2 months) of naltrexone, a narcotic antagonist, are described.

Animals↗

PubMed1978

Monitoring of styrene exposure in the polyester industry.

Obtaining reliable results of exposure to styrene in field studies requires an appropriate methodology not only for analytical methods but also for the main strategy of conducting the surveys. This paper briefly describes how and why analytical methods for styrene in air, for its main metabolites in urine (mandelic and phenylglyoxylic acids) and for critical biological function tests were either chosen from the literature or adapted or developed to fit our criteria of convenience and reliability. In a second step of the preparation of field studies, experimental exposures to styrene were carried out on volunteers so that the best indicators of exposure could be determined and data could be obtained on the elimination kinetics of the urinary metabolites and the quantitative relationships between exposure and the urinary concentrations of mandelic and phenylglyoxylic acids. Finally field investigations, including air and biological monitoring, complete industrial hygiene surveys and medical examinations, have been organized and are being carried out in the Swiss polyester industry. Preliminary results concerning biological monitoring are given.

Air Pollutants↗

PubMed1995

A non-linear compartmental model to describe forage degradation kinetics during incubation in polyester bags in the rumen.

A new model for describing forage degradation kinetics during incubation in the rumen using polyester bags is presented. Attention is given to dealing with the problem of deviations from exponential behaviour in the early stages of degradation by devising a function capable of representing exponential or sigmoidal trends. This is achieved by allowing part of the fractional degradation rate to vary with time of incubation, thus enabling responses other than those expected under simple first-order kinetics to be described. Seven sets of data consisting of 620 curves were analysed to study the performance of the new model compared with a commonly used exponential model. The proportion of significantly better fits varied from set to set. The new model deals successfully with sigmoidal behaviour and, thus, provides a means of analysing the degradation profiles of low-quality forage feeds.

Animal Feed↗