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PubMed2003

Reduced adhesion of blood cells to biodegradable polymers by introducing phosphorylcholine moieties.

Aliphatic polyesters are believed to be good biocompatible polymers for tissue engineering because of their biodegradability and nontoxicity of the degradated products. However, it is necessary to reduce the nonspecific protein adsorption for the application of biodegradable polymers to drug delivery systems or antiadhesive membranes. We hypothesized that novel biodegradable polymers could be synthesized by introducing phosphorylcholine moieties into aliphatic polyesters. The L-lactide was polymerized in the presence of L-alpha-glycelophosphorylcholine (LGPC) using stannous octate as the catalyst. The molecular weight and crystallinity of poly(L-lactide) (PLLA)-based phospholipid polymers (PLLA-PC) decreased with an increase in the composition of the LGPC unit in the PLLA-PC. The hydrolysis of the PLLA-PC was evaluated by soaking the polymer membranes in a phosphate buffer solution. The rate of weight loss was increased with increasing the LGPC units in PLLA-PC. The surface analysis of the membranes using an X-ray photoelectron microscope showed the composition of phosphorylcoline groups on the surface. The amount of adsorbed protein and adherent blood cell on the polymer surface was decreased with introducing LGPC unit. PLLA-PC is a promising biodegradable polymer having blood compatibility and antiadhesive property.

Adsorption↗

PubMed2005

Enzymatic transformation of bacterial polyhydroxyalkanoates into repolymerizable oligomers directed towards chemical recycling.

The enzymatic transformation into an oligomer was carried out with the objective of developing the chemical recycling of bacterial polyesters. Poly(R-3-hydroxyalkanoate)s (PHAs), such as poly[(R-3-hydroxybutyrate)-co-12%(R-3-hydroxyhexanoate)] and poly[(R-3-hydroxybutyrate)-co-12%(R-3-hydroxyvalerate)], were degraded by granulated Candida antarctica lipase B immobilized on hydrophilic silica (lipase GCA) in a diluted organic solvent at 70 degrees C. The degradation products were cyclic oligomers having a molecular weight of a few hundreds. The obtained cyclic oligomer was readily repolymerized by the same lipase (lipase GCA) to produce the corresponding polyester in a concentrated solution. The cyclic oligomer was copolymerized with epsilon-caprolactone using lipase to produce the corresponding terpolymers having an Mw of 21,000. This is the first example of the enzymatic chemical recycling of bacterial PHAs using lipase. Poly(R-3-hydroxybutyrate) [P(3HB)] was also degraded into the linear-type R-3HB monomer to trimer by P(3HB)-depolymerase (PHBDP) in phosphate buffer at 37 degrees C. The degradation using PHBDP required a longer reaction time compared with the lipase-catalyzed degradation in organic solvent. The monomer composition of the oligomer depended on the origin of the PHBDP. The R-3HB monomer was predominately produced by PHBDP from Pseudomonas stutzeri, while the R-3HB dimer was produced by PHBDP from Alcaligenes faecalis T1. Repolymerization of these oligomers by lipase in concentrated organic solvent produced a relatively low-molecular-weight P(3HB) (e.g., Mw=2,000). Degradation of P(3HB) by lipase in organic solvent into repolymerizable cyclic oligomer and degradation of P(3HB) by PHBDP in buffer into hydroxy acid type R-3HB dimer.

Alcaligenes faecalis↗

PubMed1995

Effects of moisture absorption by clothing on thermal responses during intermittent exercise at 24 degrees C.

The effects of two kinds of clothing with different properties with respect to moisture absorption on thermophysiological responses and pulse rate were studied during intermittent exercise at an ambient temperature (Ta) of 24 degrees C. The two kinds of clothing ensemble tested were cotton T-shirt with short sleeves and cotton long-sleeved working dress with full-length trousers (C), and polyester T-shirt with short sleeves and polyester long-sleeved working dress with full-length trousers (P), the thermal resistances of which were nearly equal. Five women aged 21-32 years, served as subjects. The environmental conditions were 24 degrees C Ta, 50% relative humidity and 0.14 m.s-1 air velocity. The subjects, wearing either C or P, exercised for 10-min on a cycle ergometer at an intensity of 30% maximal oxygen uptake and then 10-min rest. This sequence was repeated four times. Rectal and skin temperatures at several sites, local sweating rate, pulse rate and clothing microclimates were continuously compared between C and P throughout the experiment. The major findings were firstly, rectal temperature rose significantly higher in P; secondly, pulse rate was higher in P both during exercise and rest; thirdly, clothing surface temperature on the back rose highly significantly during the fourth exercise period and then fell significantly during the fourth rest period in C; and fourthly, four out of five subjects felt wetter in P during the latter half of the experiment. These results are discussed from the viewpoint that the reduced thermal insulation due to the absorption of moisture in C accelerated dry heat loss, resulting in an inhibition of the increases in core temperature and pulse rate.

Absorption↗

PubMed1993

Macrolide antibiotics as antiinflammatory agents: roxithromycin in an unexpected role.

The antiinflammatory activity of a new 14-membered macrolide antibiotic, roxithromycin, was evaluated in various rat models including carrageenan- and poly-L-arginine-induced hind-paw oedema, croton oil inflamed ear assay and polyester sponge granuloma. When administered orally to animals, roxithromycin displayed an atypical profile in the assays utilized, including: (1) marked antioedema activity similar to that of indomethacin in poly-L-arginine assay, (2) significant inhibition of lambda-carrageenan hind-paw oedema and croton-oil-induced inflammation in the ear, although indomethacin was more effective, and (3) failure to reduce the development of granuloma induced by implanted polyester sponges, while indomethacin significantly reduced the chronic inflammatory reaction. Based on these results, it is concluded that roxithromycin is active in reducing the acute inflammatory reaction in rat models through mechanisms different from conventional nonsteroidal antiinflammatory agents such as indomethacin. Therefore, roxithromycin may have a favorable impact on skin inflammatory reactions accompanying microbial infections.

Analysis of Variance↗

PubMed2001

[Problem of recurrent incisional hernia after mesh repair of the abdominal wall].

INTRODUCTION: Depending on the surgical technique, mesh material and follow-up, the figures for recurrences of incisional hernia vary from 0 to 31%. What are the reasons for recurrences, and which options exist for more successful therapy? METHODS: Fourteen operations for recurrences after mesh repair of incisional hernias were analyzed retrospectively and correlated with a literature review of the years 1990-2000. RESULTS: An inadequate surgical technique is the main reason for recurrences after the use of polypropylene or polyester, but with PTFE, it is instead the properties of the material. In our patients we found central mesh recurrences. The first results with laparoscopic technique are very promising. CONCLUSIONS: Open incisional hernia mesh repair should be performed with the sublay technique, preferably with polypropylene; the use of polyester can be recommended only with reservations and the use of PTFE ought to be limited to very few indications. The entire incision should always be prepared with safe fixation of the mesh and wide overlap of the hernia. Recurrences after polypropylene implantation can be treated with additional mesh; concerning PTFE, a different material is recommended. A final evaluation of laparoscopic mesh repair cannot be assessed yet.

Adult↗

PubMed1999

Microbial production of 1,3-propanediol.

1,3-Propanediol (1,3-PD) production by fermentation of glycerol was described in 1881 but little attention was paid to this microbial route for over a century. Glycerol conversion to 1,3-PD can be carried out by Clostridia as well as Enterobacteriaceae. The main intermediate of the oxidative pathway is pyruvate, the further utilization of which produces CO2, H2, acetate, butyrate, ethanol, butanol and 2,3-butanediol. In addition, lactate and succinate are generated. The yield of 1,3-PD per glycerol is determined by the availability of NADH2, which is mainly affected by the product distribution (of the oxidative pathway) and depends first of all on the microorganism used but also on the process conditions (type of fermentation, substrate excess, various inhibitions). In the past decade, research to produce 1,3-PD microbially was considerably expanded as the diol can be used for various polycondensates. In particular, polyesters with useful properties can be manufactured. A prerequisite for making a "green" polyester is a most cost-effective production of 1,3-PD, which, in practical terms, can only be achieved by using an alternative substrate, such as glucose instead of glycerol. Therefore, great efforts are now being made to combine the pathway from glucose to glycerol successfully with the bacterial route from glycerol to 1,3-PD. Thus, 1,3-PD may become the first bulk chemical produced by a genetically engineered microorganism.

Adenosine Triphosphate↗

PubMed1999

Estimation of the percutaneous absorption of styrene in an industrial situation.

OBJECTIVE: This field study was designed to compare the level of styrene absorbed percutaneously with that absorbed by inhalation in a real situation in the fiberglass-reinforced polyester industry. METHODS: The study protocol consisted of comparisons of the patterns of urinary excretion of styrene metabolites by four groups of workers, all of whom performed the same task at the same time in the same workshop but wore the following different protective equipment: total protection with an insulating suit and mask, respiratory equipment only, percutaneous protection only, and no protection. RESULTS: The urinary excretion level of the group with total protection did not significantly differ from that of the group with respiratory protection only. CONCLUSIONS: Precutaneous absorption is not a particularly important pathway for styrene absorption during stratification work in the polyester industry. Completely insulating personal protective equipment provides no greater level of protection than does a respirator at positive pressure alone.

Analysis of Variance↗

PubMed2006

New microsurgical technique for intraparenchymal lesions of the brain: transcylinder approach.

BACKGROUND: Although various minimally invasive approaches, including endoscopic, stereotaxic, and ultrasound-guided surgery, have been introduced to minimize damage to healthy brain tissue, the microsurgical technique has retained a significant role in contemporary neurosurgery. A new microsurgical approach to intraparenchymal brain lesions, namely, the transcylinder approach, was developed to realize both minimal surgical access and sufficient microsurgical technique. METHOD: A 0.1-mm transparent polyester film was used to create a cylindrical surgical route. The film was rolled into a thin stick and used to penetrate the brain, and a computer-aided navigation system was used from inside the stick to access the lesion accurately. After the stick gained access to the lesion, it was dilated to 2 cm, and this diameter was maintained during surgery. FINDINGS: The transcylinder approach was used in 11 cases, including intraparenchymal tumours and haematomas, and the usual microsurgical procedure was performed without difficulty. The film avoided unnecessary enlargement of the surgical field and minimized injury to the brain. Intra-operative ultrasonography also can be used to identify the lesion through the cylinder because the polyester film does not reflect the ultrasound beam. The surgical route was observed to recover to almost the same size as the initial cortical incision after removal of the cylinder. CONCLUSIONS: The transcylinder approach could be advantageous for removing tumours or haematomas in the intraventricular or intraparenchymal regions. By avoiding unnecessary retraction, it significantly reduces the risk of injury to surrounding brain tissue while facilitating precise microsurgical technique. The accuracy of this minimally invasive technique can be enhanced when used in conjunction with frameless stereotaxy and intra-operative ultrasound guidance.

Adolescent↗

PubMed2006

Biomechanical differences resulting from the combination of suture materials and repair techniques.

BACKGROUND: Many suture materials and repair techniques have been applied in clinical tendon surgery. However, no recommendation is available concerning the choice of suture materials and repair techniques except in a few experimental studies. The purpose of the current study is to show the biomechanical difference resulting from the combination of suture materials and repair techniques. METHODS: The gastrocnemius tendons of 24-week-old cattle (diameter 14-16x9-11 mm) were repaired with application of a single locking, multiple locking, single grasping, or multiple grasping technique using a USP2 suture thread of either braided polyblend polyethylene, polyester, polydioxanone, or nylon. Therefore, a total of 16 combinations were made, with eight specimens for each combination. The specimen was set in an Instron tensiometer to measure the gap length after repetitive tensile loading 500 times (10-100 N). RESULTS: The single locking technique using braided polyblend polyethylene provided the smallest gap (4.5+/-0.5 mm). Other techniques using the same material resulted in a large gap (10.0-11.8 mm). The polyester provided a relatively smaller gap length, irrespective of the repair technique (7.4-8.8 mm). Polydioxanone and nylon tended to result in a large gap (9.3-12.3 mm and 8.4-10.6 mm, respectively). CONCLUSIONS: Mechanical properties of each tendon suture depended on the particular combination of suture materials and repair techniques. The combination of braided polyblend polyethylene and single locking technique provided the highest antigap strength.

Animals↗

PubMed2002

The use of three different mesh materials in the treatment of abdominal wall defects.

Various prosthetic materials have been proposed for the repair of abdominal wall defects. These materials offer tension-free repair and significantly lower recurrence rate. Their respective properties are related to such complications as seroma, infection, fistula formation, intestinal adhesions and removal. We compared the final outcome in treating abdominal wall defects in 56 patients with three different prosthetic materials: conventional polypropylene in a preperitoneal location, expanded polytetrafluoroethylene mesh, and hydrophilic membrane coated polyester mesh in an intraperitoneal location. The hydrophilic coated polyester group exhibited the lowest complication rate and the polypropylene group the highest.

Abdominal Muscles↗

PubMed2006

Production of fungal antibiotics using polymeric solid supports in solid-state and liquid fermentation.

The use of inert absorbent polymeric supports for cellular attachment in solid-state fungal fermentation influenced growth, morphology, and production of bioactive secondary metabolites. Two filamentous fungi exemplified the utility of this approach to facilitate the discovery of new antimicrobial compounds. Cylindrocarpon sp. LL-Cyan426 produced pyrrocidines A and B and Acremonium sp. LL-Cyan416 produced acremonidins A-E when grown on agar bearing moist polyester-cellulose paper and generated distinctly different metabolite profiles than the conventional shaken or stationary liquid fermentations. Differences were also apparent when tenfold concentrated methanol extracts from these fermentations were tested against antibiotic-susceptible and antibiotic-resistant Gram-positive bacteria, and zones of inhibition were compared. Shaken broth cultures of Acremonium sp. or Cylindrocarpon sp. showed complex HPLC patterns, lower levels of target compounds, and high levels of unwanted compounds and medium components, while agar/solid support cultures showed significantly increased yields of pyrrocidines A and B and acremonidins A-E, respectively. This method, mixed-phase fermentation (fermentation with an inert solid support bearing liquid medium), exploited the increase in surface area available for fungal growth on the supports and the tendency of some microorganisms to adhere to solid surfaces, possibly mimicking their natural growth habits. The production of dimeric anthraquinones by Penicillium sp. LL-WF159 was investigated in liquid fermentation using various inert polymeric immobilization supports composed of polypropylene, polypropylene cellulose, polyester-cellulose, or polyurethane. This culture produced rugulosin, skyrin, flavomannin, and a new bisanthracene, WF159-A, after fermentation in the presence and absence of polymeric supports for mycelial attachment. The physical nature of the different support systems influenced culture morphology and relative metabolite yields, as determined by HPLC analysis and measurement of antimicrobial activity. The application of such immobilized-cell fermentation methods under solid and liquid conditions facilitated the discovery of new antibiotic compounds, and offers new approaches to fungal fermentation for natural product discovery.

Acremonium↗

PubMed2006

A novel PHB depolymerase from a thermophilic Streptomyces sp.

A novel PHB depolymerase from a thermophilic Streptomyces sp. MG was purified to homogeneity by hydrophobic interaction chromatography and gel filtration. The molecular mass of the purified enzyme was 43 kDa as determined by size exclusion chromatography and 41 kDa by SDS-PAGE. The optimum pH and temperature were 8.5 and 60 degrees C respectively. The enzyme was stable at 50 degrees C and from pH 6.5-8.5. The enzyme hydrolyzed not only bacterial polyesters, i.e. poly(3-hydroxybutyric acid and poly(3-hydroxybutyrate-co-3-hydroxyvalerate), but also synthetic, aliphatic polyesters such as polypropiolactone, poly(ethylene adipate) and poly(ethylene succinate).

Acyltransferases↗

PubMed1989

An evaluation of microdisks for dental identification.

Twenty polyester dental identification microdisks were bonded to the surface of 20 extracted human mandibular molars and placed in 0.9% saline solution for 26 weeks, after which the teeth with bonded microdisks were embedded in bovine muscle tissue and incinerated for 11 minutes. Under the conditions of this study, 2 of the 20 polyester microdisks did not demonstrate deterioration and remained legible after storage in saline. The teeth and bonded microdisks did not appear to be affected by 11 minutes of incineration. A list of ideal characteristics for identification microdisks did proposed.

Chemical Phenomena↗

PubMed1990

Chiral poly(beta-hydroxyalkanoates): an adaptable helix influenced by the alkane side-chain.

Bacterial copolyesters of poly(beta-hydroxyalkanoates) (PHA) with average side-chain lengths between C5 and C7 crystallize as a 21 helix in an orthorhombic lattice with two molecules per unit cell. The fibre repeat, or c dimension, is 4.55 A on average, compared with 5.96 and 5.56 A for poly(beta-hydroxybutyrate) (PHB) and poly(beta-hydroxyvalerate) (PHV), respectively. This collapse of the c dimension while maintaining the 21 helical symmetry may be thought of as crystallization driven by side-chain packing influences. This class of PHA with homologous hydrocarbon side-chains must form ordered sheets with the extended alkane branches in polyethylene-like domains. The melting point, glass transition temperature and fibre repeat change regularly as a function of average number of side-chain carbons for the whole family of PHA. X-ray diffraction of a melt-crystallized PHA indicated a maximum crystallinity of about 25%, achieved only after several hours at room temperature. Compared with P(HB-co-HV) polyesters, the stress-strain curves of PHA polyesters studied are typical of elastomers. 13C-n.m.r. spectra and relaxation times of the bulk phase amorphous regions of these polymers demonstrate the high degree of motional freedom of the side-chains and the significantly slower motion for the backbone carbons. 13C n.m.r. was also used to estimate the percentage crystallinity which is in agreement with the X-ray diffraction results. Modelling and conformational analysis of single chains using the virtual bond approach lead to two possible models for the crystalline helix: 'herringbone' versus 'comb-like'.

Alkanes↗

PubMed1991

Accumulation of a poly(hydroxyalkanoate) copolymer containing primarily 3-hydroxyvalerate from simple carbohydrate substrates by Rhodococcus sp. NCIMB 40126.

A number of taxonomically-related bacteria have been identified which accumulate poly(hydroxyalkanoate) (PHA) copolymers containing primarily 3-hydroxyvalerate (3HV) monomer units from a range of unrelated single carbon sources. One of these, Rhodococcus sp. NCIMB 40126, was further investigated and shown to produce a copolymer containing 75 mol% 3HV and 25 mol% 3-hydroxybutyrate (3HB) from glucose as sole carbon source. Polyesters containing both 3HV and 3HB monomer units, together with 4-hydroxybutyrate (4HB), 5-hydroxyvalerate (5HV) or 3-hydroxyhexanoate (3HHx), were also produced by this organism from certain accumulation substrates. With valeric acid as substrate, almost pure (99 mol% 3HV) poly(3-hydroxyvalerate) was produced. N.m.r. analysis confirmed the composition of these polyesters. The thermal properties and molecular weight of the copolymer produced from glucose were comparable to those of PHB produced by Alcaligenes eutrophus.

Glucose↗

PubMed1990

XPS and SSIMS analysis of the surface chemical structure of poly(caprolactone) and poly(beta-hydroxybutyrate-beta-hydroxyvalerate) copolymers.

The surface chemical structures of poly(beta-hydroxybutyrate), poly(caprolactone) and poly(beta-hydroxybutyrate-co-beta-hydroxyvalerate) have been analysed using static secondary ion mass spectrometry and X-ray photoelectron spectroscopy. The X-ray photoelectron spectroscopy data confirm the purity of the polyester surfaces and there is close agreement between the stoichiometric and experimentally determined ratios of the peaks and different carbon environments within the C1s envelopes. The static secondary ion mass spectrometry analysis reveals general fragmentation pathways which permit the ready distinction between the different polyesters examined. The differentiation of the different monomer repeat units in the copolymer together with the detection of some ions representative of the random copolymer sequence are also possible in the static secondary ion mass spectrometry analysis.

Biocompatible Materials↗

PubMed1992

In vivo degradation of massive poly(alpha-hydroxy acids): validation of in vitro findings.

The degradation of various high-molecular-weight aliphatic polyesters derived from glycolic acid and/or lactic acid enantiomers was previously investigated in vitro. It was demonstrated that the bulk degradation mechanism proposed in the literature actually proceeds heterogeneously and proceeds faster in the centre than at the surface of large specimens. In order to compare them, similar compression-moulded specimens were implanted intramuscularly in the backs of rabbits, namely PLA50 (poly(DL-lactic acid)), PLA37.5GA25 (75% DL-lactide and 25% glycolide in the feed) and PLA75GA25 (75% L-lactide and 25% glycolide). These three intrinsically amorphous compounds exhibited faster central degradation. Furthermore, preferential degradation of glycolic acid units and induced crystallization of L-lactic acid enriched fragments were observed in the case of PLA75GA25. These findings are comparable to phenomena observed in vitro and are conclusively supported by the re-examination of some old in vivo results. Accordingly, data reported in this paper validate both the in vitro modelling and new understanding of the degradation of lactic acid/glycolic acid-based aliphatic polyesters reported previously.

Animals↗

PubMed1993

Histopathological and immunological investigations of synthetic fibres and structures used in three prosthetic anterior cruciate ligaments: in vivo study in the rat.

Three types of prosthetic anterior cruciate ligaments were investigated by enzymatic and histological analysis of the tissue surrounding each implant and immunologically by a cytofluorometric analysis of T-cell populations in the peripheral blood of rats. Two of the prostheses had a braided construction, one made from polyester and the other from high performance polyethylene fibres. The third type also contained high performance polyethylene fibres, but had been manufactured in a knitted construction (Raschel high performance polyethylene). Five specimens from each prosthesis were implanted intraperitoneally in rats by a trocar for different periods of time up to 4 wk. A control group of rats underwent the surgery, but not the implant. No modification in peripheral T-cell populations was induced by the presence of any implant. Whilst the levels of acid phosphatase and esterase activity appeared to have increased slightly following implantation of any of the prostheses, such increases were not highly significant. Histologically, all three materials induced an intense acute inflammatory reaction at 3 d which gave way to a typical chronic response after 4 wk. The only major difference between the prostheses was that after 4 wk the polyester fibres exhibited less inflammation, and the surrounding tissue was more mature, more vascularized and more densely infiltrated with collagen than with the two high performance polyethylene implants. In conclusion, all three devices provided satisfactory biocompatibility in terms of cellular and healing response.

Acid Phosphatase↗