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At least 487 records · Page 27Linked to original sources

PubMedDate not supplied

Removing UV-A and UV-C radiation from UV-B fluorescent lamp emissions. Differences in the inhibition of photosynthesis in the marine alga Dunaliella tertiolecta using chromate versus cellulose acetate-polyester filters.

Ultraviolet-B (UV-B; 280-320 nm)-emitting lamps unavoidably emit ultraviolet-A (UV-A; 320-400 nm) and ultraviolet-C (UV-C; <280 nm) radiation. Short-wavelength-blocking filters are generally used to limit the wave bands of UV under investigation. The widespread use of such filters means that all exposures to UV-B radiation will have a significant UV-A component. Therefore, the physiological effects unique to UV-B exposure are difficult to clearly isolate. This study presents a method to remove the UV-A and UV-C "contamination" using a liquid potassium chromate (K(2)CrO(4)) filter, thus allowing more direct assessment of the effects of UV-B exposure. Cultures of the green marine alga Dunaliella tertiolecta were grown in the absence of UV radiation. Sunlamps supplied the UV radiation for a 24 h exposure (solar radiation was not used in this study). The UV radiation was filtered either by the standard method (i.e. cellulose acetate (CA) with polyester = Mylar controls) or by a liquid filter of potassium chromate. Photosynthetic responses were compared. Major decreases in the ratio of variable to maximal fluorescence in dark-adapted cells and photosynthetic capacity were observed in CA-filtered cultures, whereas no change was observed in cells exposed to the same UV-B flux with the UV-A removed by K(2)CrO(4). The use of a CA filter with a Mylar control does not link results unequivocally to UV-B radiation. Such results should be interpreted with caution.

Cellulose↗

PubMed1999

Immunization by subcutaneous implants of polyester-polyurethane sponges coupled with antigen.

A new protocol is described for immunization of outbred Swiss mice. The procedure is based on subcutaneous implantation of antigen-coupled polyester-polyurethane sponges cut into disks of 10 mm in diameter vs 2 mm in thickness. Antigen coupling was performed by overnight incubation of the sponge with a solution of ovalbumin (Ova) (2 mg/ml) diluted in sodium carbonate buffer, pH 9.6. The amount of ovalbumin that was taken up by the sponge was between 71.4 to 82.5 micrograms. This was estimated by comparing the Ova absorbance at 280 nm in coating buffer solutions before and after incubation. To compare the efficiency of the proposed method, experimental groups immunized with the antigen in the presence of adjuvants (10 micrograms in Al(OH)3 or 100 micrograms in complete Freund's adjuvant (CFA)) were run in parallel. The data obtained after the 3rd week of immunization indicate that both cellular and humoral immune responses were achieved. These were assayed by antigen-induced footpad swelling and ELISA (specific antibodies), respectively. The levels of both immune responses elicited were similar to the responses observed in mice immunized with ovalbumin in the presence of Al(OH)3. The method might represent an advantage when immunizing with pathogenic antigens. Preliminary experiments have suggested that the antigen remains immobilized or bound to the sponge for a long period of time, since there is an increment on the cell population inside the sponges after boosting the animals. If so, the undesirable effects of immunization would be reduced.

Animals↗

PubMed1999

Comparison of mathematical models to describe disappearance curves obtained using the polyester bag technique for incubating feeds in the rumen.

Different nonlinear models were evaluated as candidates to describe ruminal degradation kinetics of forages from data obtained by the incubation of the feeds in the rumen using polyester bags. Nine models were used: segmented model with three straight lines (Mod0); simple Mitscherlich or exponential (Mod1); inverse polynomial (Mod2); compartmental model with two exponential terms (Mod3); generalized Mitscherlich (Mod4); generalized Michaelis-Menten (Mod5); logistic (Mod6); Gompertz (Mod7); and generalized Von Bertalanffy (Mod8). All these models can be represented in the general form D = W + S0 x phi(t), where D is in situ disappearance at incubation time t, W and S0 are positive scalars, and phi is a positive monotonically increasing function unique to each of the models studied. Based on first principles, a general formula for calculating the extent of degradation of feeds in the rumen has been derived that is applicable to all the models. The disappearance curves of different feed components (DM, N, and NDF) of 87 Mediterranean forages (i.e., a total of 261 curves) were fitted to all the models. A comparative study was carried out based on the mathematical, statistical, and biological characteristics of the models. Flexible models that can accommodate both diminishing returns and sigmoidal behavior were more appropriate in describing the curves. A discrete-lag parameter was introduced into Mod0, Mod1, and Mod2 to describe the initial stage of the disappearance curve, and this parameter considerably improved the fit of experimental data. Based on statistical criteria, models Mod1, Mod4, Mod5, and Mod8 were better than the others for most statistical tests and disappearance curves, but differences among these four models were not consistent. The estimates of degradation parameters to quantify the rate (half-life, fractional degradation rate), and extent (undegradable fraction, effective degradability) of ruminal degradation of feeds were also used as a means to discriminate between models, although in most cases all of the models gave similar values of the degradation parameters. In particular, when the extent of degradation was calculated for each forage and feed component, differences between the estimates obtained with the different models were of little nutritional significance for the animal.

Animal Feed↗

PubMed1998

Entrapment efficiency and initial release of phenylbutazone from nanocapsules prepared from different polyesters.

Several formulations of poly(epsilon-caprolactone) (PCL), poly(lactic acid) (PLA), and poly(lactic-co-glycolic acid) (PLGA) nanocapsules containing phenylbutazone were prepared according to the interfacial deposition technique. These formulations differed in the type of polymer used to form the shell of the nanocapsules. Analysis of particle size distribution and encapsulation efficiency of the nanocapsules revealed that the type and molecular weight of polyester used were the main factors influencing these properties. PLA had the highest encapsulation efficiency with the best reproducibility. From in vitro release studies, a small amount of drug release was observed at pH 7.4. However, in the gastric medium, an important burst effect occurred and was highest with the PLGAs and lowest with PCL, suggesting that drug release from these systems is affected by the type of polymer and the environmental conditions. The two formulations of phenylbutazone-loaded nanocapsules should be evaluated based on PCL and PLA in vivo in order to determine to what extent they are able to reduce the local side effects of this drug.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1995

Stability of polypeptide immunoreactants and polyvinyl alcohol as a blocking agent on polyester cloth during dry storage.

During dry storage at 32 degrees C for 70 days, polypeptide immunoreactants (rabbit IgG and rabbit antiperoxidase antibody) adsorbed onto polyester cloth demonstrated no loss of immunoreactivity. Polyvinyl alcohol of molecular weight 30,000-70,000 provided a stable blocking capacity on the immunoreactant-adsorbed cloth without affecting immunoreactivity. Cloth-based enzyme immunoassay systems are suitable for field testing and transportation in the absence of refrigeration.

Adsorption↗

PubMedDate not supplied

Application of antibody adsorbed polyester cloth for the rapid screening of elution conditions for antigen immunopurification.

Antibody adsorbed onto polyester cloth did not desorb during a 20 hour agitated incubation in commonly used antigen-antibody dissociating agents. Antibody activity on the cloth was also unaffected by five 20 min cycles of agitation in these agents. Use of cloth segments coated with a model antibody, goat anti-rabbit IgG antibody, permitted rapid screening of elution conditions for the immunoaffinity purification of a model antigen, rabbit IgG. Thus, this simple test is useful for designing an optimal immunoaffinity chromatographic procedure.

Animals↗

PubMed1996

Immunological detection of lipopolysaccharide antigens of thermophilic campylobacters captured on polymyxin-coated polyester cloth.

Cholate-extracted lipopolysaccharide (LPS) antigens from thermophilic campylobacters were captured on polymyxin-coated polyester cloth. The captured antigens were detected by sequential reactions with rabbit anti-Campylobacter antibody, anti-rabbit IgG peroxidase conjugate and chromogenic peroxidase substrate. A polyclonal rabbit antibody elicited against a single Campylobacter-jejuni strain detected the reference strains of the twenty most frequently isolated thermophilic campylobacters in the Lior serotyping scheme. Moreover, LPS antigens of six C. Jejuni Penner serotypes fractionated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and examined by immunoblotting were recognized by four antisera prepared against homologous and heterologous Penner serotypes. The results suggest the potential application of polymyxin-cloth enzyme immunoassay for rapid detection of thermophilic campylobacters where monoclonal antibodies can be raised to possible common LPS epitopes.

Animals↗

PubMedDate not supplied

Longitudinal forces acting on a knitted polyester arterial prosthesis when implanted as a thoracic aorta substitute in the dog.

The longitudinal forces under which arterial prostheses are held in situ are of great importance. The tension caused by the longitudinal force may be one of the factors involved in the formation of anastomotic false aneurysms. In order to measure the changes in the longitudinal force at both proximal and distal end-to-end anastomoses over different periods of implantation, we devised an experimental study in which the changes in length of a warp-knitted polyester VP1200K (Vascutek Ltd., Inchinnan, Scotland) arterial prosthesis, used as a thoracic aorta substitute in the dog, were recorded photographically at implantation and removal. The longitudinal forces acting at the two sites were then calculated using a linear relationship between the longitudinal force and the changes in length of a virgin prosthesis, which was found experimentally in vitro using a computerized laser calibration system. One-tailed Student's t-test showed no significant difference between the length indicator values at the two anastomotic sites at different periods of implantation except during the 1-month period. Textile analysis of the explanted prostheses and histopathologic observations confirmed this similar behavior at the two anastomotic sites. These observations were contrary to the theoretic prediction regarding the effect of forces applied by drag and tissue ingrowth. Nevertheless, analysis of variance confirmed that there was no difference evident at the two sites between different implantation periods. These observations may explain why the formation of anastomotic false aneurysms is less common at end-to-end anastomoses.

Animals↗

PubMedDate not supplied

Longitudinal forces acting at side-to-end and end-to-side anastomoses when a knitted polyester arterial prosthesis is implanted in the dog.

In a previous study, which investigated the tensions at the proximal and distal end-to-end anastomoses of a vascular prosthesis, no significant differences were found in the longitudinal forces between the two anastomotic sites after different periods of implantation. The present follow-up study was devised to study the longitudinal forces at a proximal side-to-end and a distal end-to-side anastomosis using a warp knitted polyester prosthesis implanted as a canine thorocoabdominal bypass. The external surface of the prosthesis contained a specially printed "tension indicator" design, which enabled changes in length to be assessed photographically at the two anastomoses at the time of implantation and at sacrifice. The longitudinal force at each site was then calculated using a relationship obtained experimentally between the total longitudinal force and the changes in length of the virgin graft in vitro. The in vitro measurements on the prosthesis were performed using a computer-controlled laser calibration system. Although the results showed a tendency toward a gradual loss in longitudinal force at both anastomoses over 7 months in situ, statistical analysis showed no significant difference in the longitudinal force at the two anastomotic sites after any period of implantation. Histopathological and textile analysis also showed that the characteristics of the prostheses were similar at both anastomotic sites. This does not mean, however, that the intramural stress concentrations experienced by the two sites were the same. While comparing the level of the longitudinal forces measured in this study with those observed in the previous thoracic aorta study using end-to-end anastomoses, no significant differences were observed due to the different types of anastomoses. It would appear that the longitudinal force is not one of the main etiological factors that cause the formation and localization of anastomotic failure.

Anastomosis, Surgical↗

PubMed1986

Mortality experience in a polyamide-polyester factory.

Chemical workers have become increasingly concerned about the presence of carcinogens in their occupational environment. As a result, a number of studies of excess cancer mortality have been undertaken in groups of workers with well-characterized exposures. This paper reports the results of one such study carried out in a polyamide-polyester factory in France. A retrospective cohort design was chosen to evaluate the effect of exposure to phthalates, nickel catalyzers, and other chemicals in the work environment. Only a slight excess of cancers, marginally related to exposure category yet not significantly related to length of exposure, was found. The cohort, however, was young but stable, and a continued follow-up is therefore both feasible and justifiable, since it is likely to yield important information about the potential hazards associated with the tergal polymer industry.

Chemical Industry↗

PubMed1983

Increased frequency of lymphocyte micronuclei in workers producing reinforced polyester resin with low exposure to styrene.

A new micronucleus method based on the analysis of lymphocytes with preserved cytoplasm revealed an increased frequency of micronuclei in 38 workers employed in a plant producing styrene-modified polyester resin as compared to the frequency in 20 referents (5.9 vs 3.6%). The time-weighted average of the styrene concentration in the workroom air varied between 1 and 36 ppm (mean 13 ppm) during the last year and correlated well to low urinary levels of mandelic acid, which ranged from 9 to 316 mg/g of creatinine (mean 65 mg/g of creatinine).

Adult↗

PubMed1999

Anchorage-dependent and suspended baby-hamster kidney cells on three-dimensional non-woven polyester fabric discs: comparison of growth characteristics.

Two types of baby-hamster kidney (BHK) cell line, anchorage-dependent BHK-An(32) and suspended BHK-An(48) cells, were cultivated on non-woven polyester fabrics (NWPF) that were prepared from non-woven polyethylene teraphthalate sheets with different void fractions in three-dimensional configuration. The attachment and growth characteristics of both cell lines were investigated in stationary and submerged cultures, containing Dulbecco's modified Eagle's medium supplemented with fetal-calf serum. All cultures displayed rapid attachment (<120 min) of inoculated cells to the discs. The growth of BHK cells on NWPF discs in stationary cultures was similar to that observed in tissue-culture dishes; however, the denser discs showed better results in terms of final cell density, especially in the case of BHK-An(48) cells. Spinner-flask cultures indicated that higher cell yields were obtained than in stationary conditions. Microscopic observation showed that anchorage-dependent BHK-An(32) cells spread through the interfibre spaces of NPWF discs to form three-dimensional structures whereas BHK-An(48) cells proliferated on fibres.

Animals↗

PubMed1999

Bone adaptation to a polyester fiber anterior cruciate ligament replacement.

A series of polyester fiber ACL implants was studied in ovine stifle joints up to 2 years postimplantation. The implants were linked to the bone-tunnel wall by oriented fibrous tissue. Cross-sections of the tunnels showed bone ingrowth among the implant fibers at 2 years. A human trial of the Apex implant yielded a series of retrievals, some associated with gross bone-tunnel enlargement. There was no evidence of bone ingrowth in the human implants. It was hypothesized that-tunnel enlargement resulted from fretting at the implant-tissue interface in response to cyclic loads in use.

Adaptation, Physiological↗

PubMed2000

Biomimetic polyesters and their role in ion transport across cell membranes.

Syntheses of biomimetic low-molecular weight poly-(R)-3-hydroxybutanoate mediated by three types of supramolecular catalysts are presented. The utility of these synthetic polyesters for preparation of artificial channels in phospholipid bilayers capable of sodium and calcium ion transport across cell membranes, is discussed. Further studies on possible applications of these bio-polymers for manufacturing drugs of prolonged activity are under way.

Cell Membrane↗

PubMed2000

[Testing the usefulness of a provisional polyester prosthesis for augmentation in reconstructive operations of knee joint ligaments].

Prosthesis from polyester fibres 5 mm wide with loose knitting finished on both ends with teflon handles for fixing bones with a wholly aphid screw made by Tricomed company in Lódź according to its own idea was the subject of the test. The tests were made on 7 piglets. The prosthesis together with an autogenic graft taken from the middle third of a patella ligaments was implanted into the place of the excised front sacral ligament. The implanted prosthesis was characterised with a high biocompatibility, satisfying mechanical resistance and easiness of fixing of the tested graft. We noticed clinically and pertaining to autopsy the possibility of removing the allogenic graft after achieving the full healing of the autogenic graft without the possibility of hurting that last one.

Animals↗

PubMed2001

[New diterpene polyesters isolated from Hungarian Euphorbia species].

Sixteen new diterpene polyesters were isolated and identified from Hungarian Euphorbiaceae species. Two of them (21, 23) are based on formerly unknown diterpene core. The structures of three jatrophane type diterpene heptaester were elucidated (1, 3, 6), which are diterpenoids with the highest degree of esterification identified from this plant family. Some of the isolated compounds have pharmacological effects, others are under testing now.

Diterpenes↗

PubMed2003

Evaluation of novel biodegradable cyclic carbonate polyester copolymers for cytocompatibility using MRC-5 cells.

The objective of this work was to synthesize and characterize a novel series of biodegradable cyclic carbonate polyester copolymers based on lactide and 5-methyl-5-benzyloxy-carbonyl-1,3-dioxan-2-one (MBC). Two compositions were selected for characterization. One copolymer was based on a racemic mixture of 1-lactide with 15.4 mole % MBC and the other was based on 1-lactide with 8.2 mole % MBC. These polymers contain carboxylic acid moieties along the backbone that may be used for tethering bioactive agents, forming ionic crosslinks or be reacted with vinyl containing monomers to allow free radical crosslinking. The initial materials evaluated have the carboxylic acid functionalities blocked with benzene. These polymers and the de-blocked versions may have potential applications for hard and soft tissue scaffolds, control drug delivery matrixes or a variety of other applications in medicine. The copolymer samples were pressed into 7.0-mm diameter disk using a KBr press. The disks were then sterilized using U.V radiation under a laminar flow hood. After sterilization, the copolymer disks were submerged in 2 ml of media and placed in a CO2 regulated incubator at 37 degrees C. A total of six groups per phase (n = 7 test tubes per group) were used in this study. Test tubes in groups I and III were plated with MRC-5 and subsequently treated with media alone (controls). Test tubes in groups II and IV were plated with MRC-5 and subsequently treated with media before being introduced to copolymer samples. Cell number, as well as, biochemical markers such as protein and malondialdehyde (MDA) were determined at the end of the 24, 48 and 72-hour time periods. Representative test tubes were subjected to an H&E staining procedure for microscopic morphological evaluation. The results of this evaluation suggest that the exposure of both copolymers produced a non-cytotoxic environment with the MRC-5 cell line. Although both copolymers are non-cytotoxic, the sample having the higher MBC content is the preferred composition based upon MDA levels and morphological evaluations.

Absorbable Implants↗

PubMed2003

[Use of polyester urethane (Neuro-Patch) as a dural substitute. Prospective study of 70 cases].

Between October 1995 and March 1998, 70 patients were treated with a microporous polyester urethane dura substitute (Neuro-Patch), after brain or spinal surgery. These patients were assessed clinically and radiologicaly 10 days, 6 weeks and 1 year after surgery. Radiological evaluation used CT scan or MRI. All dura substitutes were fixed by continuous suture to the surrounding dura-mater. We studied the handling properties, the incidence of infection and of CSF leakage. Eleven patients underwent craniotomy again. This gave us the opportunity to examine the adhesion to the brain tissue and the integration of the dura substitute. Six sheets underwent histological examination. Our results show good handling properties of the material; 3 infections; 6 out of 9 radiological CSF leakage occurred from infratentorial surgery. During reoperation, no adhesion to the brain tissue or injury to the brain while detaching the dura substitute was noticed. An excellent histological integration was observed: pores of the Neuro-Patch were colonized by fibroblasts synthesizing collagen, and there was no immune or inflammatory reaction, with an actual 4 to 6 years follow-up. A Neuro-Patch can therefore be recommended as a dura substitute to repair spinal or cranial dural defects.

Adolescent↗