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At least 1,171 records · Page 65Linked to original sources

PubMed2000

Enzyme-catalyzed synthesis of sugar-containing monomers and linear polymers.

Commercially available proteases and lipases were screened for their ability to acylate regioselectively sucrose and trehalose with divinyladipic acid ester. Opticlean M375 (subtilisin from Bacillus licheniformis) was observed to form sucrose 1'-O-adipate and trehalose 6-O-adipate in anhydrous pyridine. Novozym-435 (lipase B from Candida antarctica) catalyzed the synthesis of sucrose 6, 6'-O-divinyladipate and trehalose 6, 6'-O-divinyladipate in acetone. These diesters were then employed as monomers in polycondensation reactions with various diols (aliphatic and aromatic) catalyzed by Novozym-435 in organic solvents to yield linear polyesters with M(w)'s up to 22,000 Da. Spectroscopic analysis confirmed that only the vinyl end groups of sugar esters reacted in the enzymatic polymerization with the diol, and not the internal sugar-adipate linkages. The two-step enzymatic strategy to yield sugar-based polyesters, which is the first report of its kind, results in higher molecular weights and faster reaction times than one-step enzymatic polyester synthesis.

Animals↗

PubMed2001

[Late complications after alloplastic vascular replacement].

The follow-up of 273 AAA patients operated 1981-1985 showed a mean dilation of polyester grafts of 17.4% in 12 days and 34.8% in 3 years. This early dilation is due to mesh expansion of the warp knitted grafts. It has no clinical relevance. In contrary the late dilation after approximately 10 years is due to degradation. The evaluation of 436 explanted grafts attained from 75 hospitals showed graft rupture to be the cause of the explanation for 42/255 (16%) polyester grafts and 2/42 (5%) PTFE grafts. The most ruptures were observed in the surrounding of the inguinal ligament after 10 to 20 years of duration. In comparison to modern endovascular grafts the conventional polyester and PTFE grafts still are the gold standard of durability.

Aortic Aneurysm, Abdominal↗

PubMed2002

Tissue reaction following the implantation of a DALLON H vascular prosthesis in the thoracic aorta defect. Experimental tests.

Vascular prostheses made of polyester or polytetrafluoroethylene fibres are most frequently used nowadays. Woven polyester prostheses are sealed following the suturing in the circulatory system, but they cause a tissue reaction. Knitted polyesters grafts cause a lesser tissue reaction, but demand intraoperative sealing. Thus numerous tests to improve them are conducted. TRICOMED S.A. (Poland) has modified the company's own double velour knitted vascular prosthesis. The graft's physical and chemical features have been changed and hydrophilia has been used, due to which dripping the graft takes little blood and its tightness is achieved in a dozen or so seconds. The evaluation of surgical qualities as well as the healing-in process of the modified knitted hydrophilic prosthesis DALLON H has been conducted at the Department of Experimental Surgery and Biomaterials of Wrocław Medical University. DALLON H prosthesis was compared to DALLON, a standard double velour knitted prosthesis. The tests were performed on 16 Polish breed piglets with 25-35 kg of weight and 2.5 months of age. Two follow-up periods of 3 and 6 months were established following the surgeries. In each group six piglets had a 6-cm-long segment of DALLON H prosthesis sutured in the thoracic aorta defect, whereas two piglets received a 6-cm-long segment of DALLON prosthesis. The evaluation of surgical qualities of both kinds of grafts was performed intraoperatively. The main emphasis was put on the conditions in which the grafts became tight and the way they were handled during the aortal anastomosis. After 3 and 6 months the animals were autopsied. A macroscopic analysis of the incurred preparations was performed. Roent-genograms of the thoracic aorta sections replaced by the grafts were made in order to establish the shape of their lumen and present calcium salt deposits in their region. Light microscopic tests were performed by dying the preparations with hematoxiline and eosine to differentiate tissues and basic morphotic elements; using the van Giesen method, in order to reveal collagenous fibres; using the Weigert method to reveal elastic fibres, and using the Koess method to reveal calcium salt deposits. An ultrastructural evaluation of the internal surface of the grafted vascular sections was performed by a scanning electron microscope. In view of the experimental tests performed it has been established that DALLON H prosthesis used in vascular surgical procedures is not difficult and the prosthesis can be handled in the same way as some other knitted vascular prostheses. DALLON H does not need preclotting and when the blood flow has been restored through the grafted section the prosthesis immediately becomes completely tight. In view of the tests performed no differences in the healing-in process between the modified DALLON H and DALLON prostheses were observed.

Anastomosis, Surgical↗

PubMedDate not supplied

Clinical evaluation of proximal contacts of Class II esthetic direct restorations.

OBJECTIVE: This study evaluated the effectiveness of proximal contacts in Class II restorations using two types of matrix bands (steel and polyester) with two different restoration techniques (incremental and with prepolymerized particles). METHOD AND MATERIALS: Eighty-eight Class II adjacent restorations using Prodigy resin composite were performed: 44 with the incremental technique (22 with steel matrix bands, 22 with polyester matrix bands) and 44 utilizing prepolymerized resin particles (22 steel matrix, 22 polyester matrix). The restorations were clinically evaluated at baseline and at 6, 12, and 18 months. Proximal contacts obtained immediately after restoration procedure in all restorations were satisfactory. RESULTS: No statistically significant alterations were found in 18 months of evaluation. CONCLUSION: Regardless of the utilized resin composite, there were no differences in the amount of proximal contact variations with respect to tested techniques and matrices.

Acid Etching, Dental↗

PubMed1992

A modified procedure for replica plating of mammalian cells allowing selection of clones based on gene expression.

The polyester cloth replica-plating technique for selection of mammalian cell clones was modified by growing cells in colonies on a flexible polytetrafluoroethylene membrane and then transferring them completely to polyester cloth (27-microns mesh), from which a replica was made by allowing cells to transfer to a cloth of smaller pore size (17-microns mesh). Using this technique, two phenotype selection methods are demonstrated here: in situ hybridization for detection of a specific mRNA and a photographic film assay for detection of luciferase expression. Cells were transfected with pSV2AL-A delta 5' in which firefly luciferase cDNA is under the control of the simian virus 40 promoter. The luciferase assay was adapted for colonies on polyester cloth; cells were permeabilized with digitonin to allow access of ATP and luciferin to the cell without disruption of colonies. Clones selected for expression or nonexpression of luciferase by the photographic film assay were positive or negative for expression after isolation from the cloth replica and subsequent growth under conventional culture conditions. The replica-plating procedure described here should be generally applicable to most mammalian cell types. The ability to produce replicas of colonies, combined with in situ hybridization or assays that can be adapted to in situ detection, provides phenotype selection for clones based on gene expression independent of growth characteristics.

Animals↗

PubMed2006

In vivo and in vitro evaluation of Class II composite resin restorations with different matrix systems.

PURPOSE: To investigate in vivo and in vitro Class II composite restorations performed with two matrix and wedge systems. MATERIALS AND METHODS: One hundred nine Class II restorations were performed in 23 patients, 59 with metallic matrices and wooden wedges (group 1) and 50 with polyester matrices and reflective wedges (group 2). All cavities were restored using Single Bond and P-60 (3M ESPE). In the metal matrix group, polymerization was performed from the occlusal, and in the polyester group through the reflective wedge. To assess microleakage, 40 proximal standard slot cavities were prepared in 20 noncarious human third molars. In the mesial cavity, the gingival margin was located at the enamel level, and in the distal cavity at the cementum/dentin. Specimens were randomly divided into two groups (n = 20) and restored with Single Bond, Z-250 (3M ESPE), and the same techniques used in the in vivo study: metal matrix/wooden wedge (group 1) and polyester matrix/reflective wedge (group 2). Specimens were thermocycled (500 times, 5 degrees C to 55 degrees C), then isolated with nail varnish and immersed in fuchsin for 8 h. Specimens were sectioned longitudinally and microleakage was assessed under magnification (40X) using a standard scoring system. RESULTS: Data were subjected to the chi-square test, Mann-Whitney U-test, and Kruskal-Wallis H-test. Matrix systems presented similar results in the clinical evaluation and the in vitro microleakage test of Class II composite restorations. Dye leakage was minimal at enamel margins, and statistically lower (p < 0.05) than at cementum/dentin margins. CONCLUSION: The different matrix systems had no influence on clinical performance or in vitro sealing ability of Class II composite restorations.

Adolescent↗

PubMedDate not supplied

Improved textured surfaces for implantable prostheses.

Textured surfaces have been shown to reduce scar tissue formation around implanted prostheses compared with identical smooth surface controls in applications such as compliance chambers for artificial heart systems. The authors have developed and evaluated alternative textured surfaces to the polyester velour surface that has been used on those devices. These new textured surfaces are fabricated with materials known to provoke a diminished tissue response compared with polyester fibers. Two new textured surfaces have been examined: a surface composed of extruded 25 micron diameter polyurethane fibrils (PF) woven into a fabric, and an integrally textured silicone rubber surface (TS) with nonfibril geometry applicable to silicone rubber implants such as mammary prostheses. In both cases, tissue fixation to the textured surface depends primarily on mechanical interdigitation with the complicated surface morphology of the implant rather than on chemical bonding. Two types of control were employed: polyester velour fabric (PV) as a textured surface, and smooth silicone rubber (SS). Each surface was first characterized with scanning electron microscopy (SEM), and test specimens consisting of 1 cm diameter by 1 mm thickness disks were then prepared and implanted subcutaneously in a series of 16 adult New Zealand white rabbits. After 8 weeks the samples were explanted and histologic sections prepared for analysis. In all cases a thin, organized tissue capsule surrounded the implant. While the tissue capsule on average was thinner surrounding the textured surface implants, variations in the individual host response were more significant. Tissue attachment was minimal with SS, present with PF, and greatest with TS and PV.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1985

[Tissue reaction to the intraneural introduction of absorbable and non-absorbable microsurgical sutures].

Significance of suture material in microchirurgical operations of nerves was the base of comparative experimental research on sutures and the reaction of tissues around the suture in early and late period. Commonly employed monophilous polyester and polyamid sutures of 9/0, 10/0 were used, as well as prototype multifilament polyester threads covered with polyurethane, and polyglicol acid threads Dexon. In the group where Dexon threads were used, 7 days after the operation the microscopic picture was the same as in the group where polyester and polyamid threads Ethilon were used. 30 days after operation the Dexon sutures changed in coloration and underwent fragmentation, after 180 days they could not be found in histological preparations. Basing on the studies it can be maintained that the use of Dexon microsurgical sutures may be a further advancement in perfecting microsurgical methods in nerve and vascular sutures.

Absorption↗

PubMed1983

Influence of capillary multifilament sutures on the antibacterial action of inflammatory cells in infected wounds.

Implants of two capillary multifilament suture materials, braided polyester and twisted polyamide with cover, in tissue infected with Staphylococcus aureus were studied with light microscopy and transmission electron microscopy. In the tissue around both suture materials there was a pronounced inflammatory cell reaction. Staphylococci were found between the filaments of both materials. Some ingrowth of granulation tissue with inflammatory cells close to the exterior thread surface was seen in braided polyester suture. No such infiltration was seen in the suture consisting of twisted polyamide with cover. Bacteriologic studies showed faster elimination of staphylococci from the braided polyester than from the twisted polyamide implants. The capacity of leukocytes to penetrate into a capillary multifilament material presumably is dependent on the structure of the suture thread. Bacteria which are enclosed in the interstices of multifilament suture material, and protected from the phagocytic activity of leukocytes, can sustain and prolong an infection.

Animals↗

PubMed1983

Peripheral nerve repair with bioresorbable prosthesis.

Using the transected sciatic nerve model in adult mice, regeneration of a large bundle of axons organized into the form of a nerve with myelinated and unmyelinated axons, Schwann cells, fibroblasts, collagen, blood vessels, and connective tissue sheaths has been achieved with bioresorbable microtubular guidance channels over gaps of 5 mm in nonimmobilized animals. After 4-6 wks postoperatively, the regenerated nerve cable contains on the order of 40% as many myelinated axons as were measured in the proximal nerve stumps. With the channels used so far in this model, regenerating axons pass into the distal stump in about 3-6 wks postoperatively. The guidance channels used consist of synthetic polyesters and/or polyester composites including glycolic and lactic acid polymers, and polyesters derived from Krebs Cycle dicarboxylic acids. Inflammatory response to these materials has been minimal. Biodegradation/resorption rates can be controlled so as to be compatible with axon growth rates.

Animals↗

PubMed1997

[Drug or plant substances which antagonize venoms or potentiate antivenins].

Dendroaspis jamesoni (Elapidae) and Echis oceliatus (Viperidae) are responsible for most of severe evenomation in Cameroon. Toxicity of venoms of these two species has been measured using mice according to the method of Spearman & Kàrber. The effect on experimental envenomation of various drugs (atropine, promethazine, neostigmine, hydrocortisone, pentosane sulfuric polyester, heparin, tranexamic acid and aminocaproic acid) and plant extracts (Schumanniophyton magnificum, Bidens pilosa, Securidaca longepedunculata and Garcinia lucida) has been observed associated or not with the antivenom lpser Afrique (SAV). The venom of D. jamesoni contains neurotoxins agonizing and antagonising acetylcholine. The toxicity of the venom did not depend on the route of injection. Atropine, promethazine, neostigmine and hydrocortisone protected animals against a venom dose up to 2 LD50. Moreover, atropine and promethazine potentiated the SAV. Similar results have been obtained with extracts from S. magnificum and B. pilosa. The venom of E. ocellatus induces haemorrhage and necrosis. The toxicity increased by 3-fold when the venom was injected through intravenous or intraperitoneal route, compared to intramuscular route. Pentosane sulfuric polyester and tranexamic acid protected mice against doses up to 3 LD50. Pentosane sulfuric polyester, hydrocortisone, heparin and aminocaproic acid increased the SAV protective titre by 50%. However, tried plant extracts weakly antagonised the venom and did not potentiate the SAV.

Aminocaproates↗

PubMed2000

The effect of knot location, suture material, and suture size on the gliding resistance of flexor tendons.

The effect of knot location, suture material, and suture size on gliding resistance between the pulley and flexor tendon was investigated in a canine model. Different suture materials [monofilament nylon (Ethilon), braided polyester suture coated with silicone (Ticron) and uncoated braided polyester suture (Mersilene)] and suture sizes (4-0, 5-0) were tested. A knot was made on either the volar surface, on one lateral side, or on both lateral sides of canine hind-paw tendons, and gliding resistance was measured. In addition, the frictional coefficient between three suture materials (4-0 nylon, 4-0 Ticron, 4-0 Mersilene) and a nylon rod were measured. The gliding resistance of the tendon with knots on both sides was highest, while tendons with one lateral knot had the lowest resistance (p < 0.01). The gliding resistance of 4-0 suture size was higher than that of 5-0 size (p < 0.0001). The coefficient of friction of nylon was lower than that of braided polyester suture (Ticron or Mersilene) (p < 0.001). The placement of knots and choice of suture material affect gliding resistance after tendon repair, and may, therefore, have an effect on the result of tendon repair.

Animals↗

PubMed1985

Automated analysis and survival selection of anchorage-dependent cells under normal growth conditions.

An instrument is described that can automatically analyze and select for a subpopulation of anchorage-dependent cells in tissue culture. Cells that label with fluorescently tagged antibodies or demonstrate structural variations are saved from exposure to a destructive high-intensity argon laser beam. The surviving population may then be cloned. The cell selection may occur in a tissue culture plate or in a microflow incubator which is designed to maintain a constant flow of media at 37 degrees C across cells growing on a glass coverslip. This incubator sits on an inverted microscope which focuses the laser beam to a diameter as small as 1 micron. A high-speed computer-controlled two-dimensional stage moves the cells past the beam for analysis, the results of which determine the fate of each cell: whether it is to be destroyed by radiant energy or selected for survival and subsequent proliferation. Another selection strategy performed by the instrument involves growing the cells on a thin, blackened polyester film which can be cut by the argon laser beam. Cells selected for cloning are then circumscribed. The heat of cutting welds the circumscribed film to a plastic coverslip surface or tissue culture chamber bottom. Nonselected cells may be removed by pulling the unattached polyester sheet from the attachment surface. The selected cells remain on polyester film disks welded to the plastic. Selections may be done automatically under computer control or manually by operator direction of stage movements. This instrument extends the art of automated cell selection and analysis to normal cell lines that must maintain cell-substratum contact (anchorage dependence) for differentiated cell function, e.g., neurons, fibroblasts, or kidney cells.

Cell Adhesion↗

PubMed1995

Disposition of ingested olestra in the Fischer 344 rat.

Four studies were conducted in the Fischer 344 rat to determine the disposition of orally gavaged olestra. Twenty-four rats were used for each study. Three olestra samples, differing in the degree of saturation of the fatty acid chains, were tested; one sample was heated to simulate olestra's intended use in preparing fried foods. In addition, a sucrose polyester (SPE) sample containing 28% short-chain penta- and lower polyesters was tested. All test samples were uniformly labeled with 14C in the sucrose moiety. Urine, feces, and CO2 were continuously collected and counted. Urine also was analyzed for [14C]sucrose by HPLC. If olestra were absorbed and systemically metabolized, [14C]sucrose would be excreted in the urine. Rats were killed 1, 3, 7, and 21 days after dosing, and tissues were collected and counted. Tissue lipids were extracted and analyzed for intact olestra or SPE by HPLC. Less than 0.15% of the dose of 14C was absorbed from the olestra samples, and about 1.3% from the SPE sample. The disposition of the absorbed radiolabel suggested that its source was glucose and fructose resulting from the intestinal hydrolysis of short-chain penta- and lower sucrose polyesters. For rats dosed with olestra, < 8 x 10(-4)% of the dose of radiolabel was recovered in the olestra-containing fraction of lipids extracted from liver, the target organ for absorbed olestra, and no [14C]sucrose was found in urine, indications that olestra essentially was not absorbed. Heating olestra did not change this result.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Mechanical features and in vivo imaging of a polymer stent.

A polyethylene-terephthalate (PETP, polyester), self-expanding, braided mesh stent has been developed for percutaneous (coronary) arterial implantation. In vitro measurements showed that the radial pressure delivered by this device was similar to a self-expanding, stainless steel stent. Due to hysteresis-like behaviour, it proved necessary to mount the polymer stent on the delivery system immediately before the placement procedure, and to select a diameter in the unconstrained condition, which was 60% larger than the diameter of the target vessel. Eight polyester stents were implanted in peripheral arteries of four pigs. Except for heparin during the implantation procedure, antithrombotic or antiplatelet drugs were not administered. After four weeks repeat angiography revealed that one of the stents was subtotally occluded. At autopsy, two other stents proved to be located in the aortic bifurcation, probably due to failure of the delivery system. Quantitative angiographic assessment showed that the mean luminal diameters at the site of stent placement were 3.3 +/- 0.2 mm before, 3.2 +/- 0.2 mm immediately after, and 2.7 +/- 0.5 mm at four weeks after implantation. Intravascular ultrasound (IVUS) examination after 4 weeks could identify the individual struts of the stents, as well as their length. In addition, a description of the extent of neointimal hyperplasia was feasible. The IVUS assessment was validated by histological examination. In conclusion, polyester stents can be constructed with mechanical properties similar to stainless steel stents. After implantation in porcine peripheral arteries, five of six correctly placed stents were patent at four weeks. Imaging of stents by angiography and IVUS provided complementary information.

Angiography↗

PubMed2004

Comparative study of knot performance and ease of manipulation of monofilament and braided sutures for arthroscopic applications.

Our aim was to identify alternative suture materials that might provide superior knot performance and equivalent ease of manipulation by means of an in vitro experimental study. Although used widely for arthroscopic shoulder stabilisation, absorbable poly( p-dioxanone) (PDS) monofilament sutures can lead to dehiscence and clinical failure due to knot slippage and/or loop elongation at low applied loads. With the objective of identifying alternative suture materials that might provide superior knot performance and equivalent ease of manipulation, an in vitro experiment was undertaken in which both Duncan and Snyder knotted loops were tied from four different suture materials using an arthroscopic knot pusher (Surgeon's 6th Finger) and a wooden practice box (Arthrex). Three monofilament sutures, made from polypropylene (PROLENE), poly(glycolidetrimethylenecarbonate-co-dioxanone) (Biosyn) and PDS, and one braided polyester suture (SURGIDAC) were tested. Ease of manipulation was evaluated by measuring the time required to tie the knots, and the knot performance was assessed in terms of loop elongation and loop holding capacity by performing cyclic fatigue testing of the loops while they were immersed in saline on an INSTRON mechanical tester. The PROLENE and SURGIDAC sutures showed improvements in loop elongation and loop holding capacity over PDS, with the Snyder knots being consistently superior to Duncan knots. BIOSYN gave no improvement over PDS. Difficulties were encountered in advancing half-hitch throws of the braided SURGIDAC suture down the cannula, which resulted in longer knotting times. In conclusion, both the polypropylene and polyester sutures gave superior knot performance to PDS, but only the polypropylene gave equivalent ease of manipulation. As a result there may be clinical advantages in replacing PDS with monofilament polypropylene or braided polyester sutures for certain arthroscopic procedures.

Arthroscopy↗

PubMed1983

Controlled release of water-soluble macromolecules from bioerodible hydrogels.

A bioerodible hydrogel based on water-soluble unsaturated polyesters crosslinked through the double bonds and capable of immobilizing water-soluble macromolecules has been developed. As the ester linkages cleave, the entrapped macromolecule is gradually released to the surrounding aqueous environment. In vitro rate of hydrolysis and concommitant macromolecule release can be controlled by constructing unsaturated polyesters containing varying proportions of esters activated by electron-withdrawing substituents vicinal to the ester function and/or by varying crosslink density. Polyesters containing unsaturation either in the polymer backbone or pendant have been prepared. Macromolecule-containing hydrogels have been fabricated as dessicated microspheres that can be resuspended in water and passed through a 22-gauge hypodermic needle.

Biodegradation, Environmental↗

PubMed1984

In vivo evaluation of a new polyurethane-coated catgut suture.

Plain catgut sutures were coated with different polyester-based polyurethanes. The sutures were implanted subcutaneously in rats and tested for tensile strength loss and tissue reactions. A polyurethane coating based on an oxalic acid polyester was hydrolysed too fast to protect the catgut against proteolysis. However, a 2-0 plain catgut having a 50 micron polyurethane coating based on glutaric acid polyester maintained its original tensile strength for 8 days. The tensile strength then decreased as for plain catgut. Histological examination of the surrounding tissues showed that the strong inflammatory reaction observed in the first three days with non-coated catguts is decreased, but occurs again later, although to a lesser extent.

Animals↗