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PubMedDate not supplied

Antithrombotic activity of a lumbrokinase immobilized polyurethane surface.

Six fractions of strong and novel fibrinolytic enzymes (lumbrokinase, LK) were extracted from the earthworm Lumbricus rubellus. The enzymes in these fractions appeared to be very stable and showed greater antithrombotic activity than other currently used antithrombotics. The authors immobilized an LK fraction that shows the most potent fibrinolytic activity on a polyurethane (PU) surface to investigate its enzymatic and antithrombotic activity. The methanol extracted PU surface was treated with a 3% (wt/vol) maleic anhydride methylvinyl ether copolymer (MAMEC) solution and finally incubated in an LK solution in PBS (pH 7.4). The immobilized LK activity was estimated by the fibrin plate method and caseinolytic activity assay. The antithrombotic activity was evaluated by in vitro 125I-fibrinogen adsorption in fresh whole blood and 99mTc platelet adhesion tests. In addition, the occlusion time was determined through ex vivo rabbit A-A shunt experiments. The content and unit activity of immobilized LK were found to be 24 micrograms/cm2 and 18 IU/cm2, respectively. The relative activity ratio of immobilized LK to soluble LK was found to be approximately 34%. Immobilized LK was stable within a various pH range and resistant to inhibitors and thermal inactivation. Less fibrinogen was adsorbed and fewer platelets adhered on an LK-immobilized surface than on PU and PU-MAMEC controls. The ex vivo occlusion time of untreated PU and PU-MAMEC surfaces were only 32 and 42 minutes, respectively. But that of LK-immobilized PU was extended to 140 minutes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

[Skeletal muscle antigens bound with a polyurethane glue].

The reaction of anaphylaxia with desensibilization on guinea pigs and the method of double diffusion in agar gel were used to study the antigenic composition of the rat skeletal muscles 3, 7 and 30 days after their cross sections were connected with polyurethane glue and silk. It is shown that in the postoperative period, besides antigens similar to those of the normal muscles, other antigens which may belong to stage-specific ones appears in the fraction of soluble proteins. The antigenic composition of the skeletal muscles is the same with both methods of connection of the tissues defects.

Animals↗
PubMed1993

Very small-diameter polyurethane vascular prostheses with rapid endothelialization for coronary artery bypass grafting.

Two types of spongy polyurethane-polydimethylsiloxane blend (Cardiothane 51, Kontron Instruments, Inc., Everett, Mass.) vascular grafts with an internal diameter of 1.5 mm were fabricated by a spray, phase-inversion technique. Low-porosity grafts with hydraulic permeability of 2.7 +/- 0.4 ml/min per square centimeter and medium-porosity grafts with hydraulic permeability of 39 +/- 8 ml/min per square centimeter displayed good handling properties and suturability. Twelve straight low-porosity grafts, 17 straight medium-porosity grafts (1.5 to 2.0 cm in length), and one loop medium-porosity graft (10 cm in length) were implanted by the same surgeon end to end in the infrarenal aorta of 30 male Sprague-Dawley rats. Three months after implantation, patency was 8% for low-porosity grafts (1/12) and 76% for straight medium-porosity grafts (13/17). The loop medium-porosity graft was also patent. The sole patent low-porosity graft showed neointimal hyperplasia and incomplete endothelialization. All but one of the patent straight medium-porosity grafts showed a glistening and transparent neointima with complete endothelialization and no anastomotic hyperplasia. The loop medium-porosity graft displayed endothelialization from each anastomosis and in many islands in the middle portion of the graft, totalling 47% of the luminal surface by morphometric analysis. Thick mural thrombus, anastomotic hyperplasia, or aneurysm formation were not observed in any patent medium-porosity graft. These data indicate that in the rat aortic replacement model it is possible to achieve patency and a high degree of endothelialization in very small-diameter prostheses of appropriate porosity.

Animals↗
PubMedDate not supplied

The relative safety of gamma-ray, autoclave, and ethylene oxide gas sterilization of thermosetting polyurethane.

Sterilization of polyurethane (PU) produces 4,4'-methylenedianiline (MDA), a known carcinogen, and various other compounds. The relationships of the components of PU to the formation of these compounds by sterilization were studied. Specimens of PU fabricated from different combinations of isocyanates and polyols were obtained from dialyzers. The molecular weight of the particular polyol was found to influence the production of MDA by sterilization. Sterilization also produced many unidentified compounds. MDA production was not always associated with the production of the other compounds. Compared with gamma-ray irradiation and ethylene oxide gas (EOG) sterilization, autoclave sterilization eluted more hydrophilic compounds. This phenomenon was significant for PUs produced from smaller-molecular-weight polyols. The combination of autoclave sterilization and a PU produced from a larger-molecular-weight polyol is recommended to minimize the production of potentially toxic compounds. Of the techniques studied, EOG sterilization produced the least amounts of MDA and the other compounds, but the residue of EOG is itself problematic. The risk posed by the amounts of MDA extracted was not significant, but the biological safety of the other compounds remains to be determined.

Aniline Compounds↗
PubMed1996

Assessment of DNA adducts and the frequency of 6-thioguanine resistant T-lymphocytes in F344 rats fed 2,4-toluenediamine or implanted with a toluenediisocyanate-containing polyester polyurethane foam.

Toluenediamines have been of toxicological concern because of their industrial use as intermediates in polyurethane synthesis and because of the potential of their release from degradation of the Microthane polyesterurethane covering of some breast implants. In this study, we have assessed the extent of DNA damage in rats treated with a carcinogenic toluenediamine isomer, 2,4-toluenediamine (2,4-TDA), under conditions that result in tumor induction, and in rats implanted with Microthane polyesterurethane foam. Time and dose-dependent formation of adducts was observed in DNA from the liver and mammary gland of rats fed 10, 40, 80 and 180 ppm 2,4-TDA for up to 6 weeks. In assays conducted 1 to 32 weeks after the start of treatment, no adducts were detected in the DNA of T-lymphocytes isolated from the spleens of animals fed 40 or 180 ppm 2,4-TDA, nor was there an increase in mutations at the hprt locus in these lymphocytes. In rats fed 40 or 180 ppm, 2,4-TDA for 6 weeks, adducts were detectable in DNA isolated from liver and mammary gland for 26 to 43 weeks after termination of the treatment. No DNA damage, as assessed by both DNA adduct measurement and induction of T-lymphocyte hprt mutations, was observed in rats up to 42 weeks after receiving subcutaneous implants of polyesterurethane foam (67 or 267 mg/kg). Although 2,4-TDA is clearly capable of damaging DNA, the results of this study are consistent with the conclusion that Microthane foam-containing implants present a minimal risk of genotoxicity through release and subsequent metabolic activation of 2,4-TDA. The study also indicates that DNA adduct formation and mutation induction in lymphocytes are inadequate biomonitors for measuring exposure to toluenediamines.

Animals↗
PubMedDate not supplied

Vascular endothelial growth factor enhances vascularization in microporous small caliber polyurethane grafts.

Neoarterial regeneration in an implanted small caliber vascular prosthesis is complexly controlled by many structural and biologic factors, such as cytokines. The authors designed an artificial graft, which was prepared as follows. Segmented polyurethane tubular film (inner diameter, 1.5 mm; wall thickness, 100 microns; length, 20 mm), in which micropores (pore size, 100 microns) were fabricated by an excimer laser ablation technique, were coated with a mixed solution of photoreactive gelatin and heparin with or without cytokines (vascular endothelial growth factor [VEGF]: 5 or 50 micrograms/ml, basic fibroblast growth factor [bFGF]: 1 microgram/ml). These coated grafts were irradiated by ultraviolet light, and were implanted in aortas of rats for 4 weeks; the VEGF (5 micrograms/ml) group, n = 6; the bFGF group, n = 6; the VEGF (5 micrograms/ml)/bFGF group, n = 11; the VEGF (50 micrograms/ml)/bFGF group, n = 5; and the control group, n = 9. Control grafts were treated without cytokines. Endothelial coverage was greater for the cytokine immobilized groups (approximately equal to 50-60%) than for the control group (approximately equal to 30%). At the midportion of the triple VEGF immobilized group, many capillaries were seen in the neoarterial intima, and in the micropores, although such capillaries were rarely observed in the bFGF and control groups. Thus, impregnation of VEGF in the gelatinous layer of grafts enhanced transanastomotic tissue ingrowth and transmural capillary ingrowth.

Animals↗
PubMedDate not supplied

A randomized study comparing IV 3000 (transparent polyurethane dressing) to a dry gauze dressing for peripheral intravenous catheter sites.

Patients with an intravenous catheter on a cardiology unit were prospectively randomized to receive a transparent polyurethane dressing (N = 49) or sterile gauze (N = 31) dressing to compare security of fixation, dressing condition, skin condition, and rates of inflammation. The mean age of patients was 63 years of age (standard deviation, 12.57), and the average length of cannulation was 18 hours. The only significant difference between the two groups was the dressing condition in the transparent group was significantly better (P = 0.006) than that of the gauze group. The results suggest that gauze dressing may be a viable option to cover i.v. exit sites for patients requiring short-term cannulation.

Adult↗
PubMed1998

Community exposure to toluene diisocyanate from a polyurethane foam manufacturing plant--North Carolina, 1997.

In August 1996, residents of a community in Randolph County, North Carolina, contacted the Agency for Toxic Substances and Disease Registry (ATSDR) because of health concerns about possible exposure to chemical emissions from a polyurethane manufacturing plant. ATSDR and the North Carolina Department of Environment, Health, and Natural Resources (NCDEHNR) conducted ambient air monitoring to characterize air contamination near the plant. ATSDR and Randolph County health officials also conducted biologic monitoring to determine whether residents were being exposed to toluene diisocyanate (TDI) emitted from the plant. This report summarizes the results of these investigations, which indicate that residents were being exposed to TDI in ambient air surrounding the plant.

Air Pollutants↗
PubMed1998

Polyurethane foams: effects of specimen size when determining cushioning stiffness.

Polyurethane (PU) foams are used as inexpensive materials for reducing interface pressure in a number of rehabilitative applications, particularly seating and prosthetic limb interfaces. Specimens of three different PU foams were cut to four different sizes and compressed according to ASTM protocols to determine their stiffness capabilities. It was found that the test results varied according to the relationship between the size of the test specimen and the test indenter. It is recommended that investigators create a testing situation that reflects their application when determining the cushioning capabilities of these materials.

Compressive Strength↗
PubMed1976

Carcinogenic activity of a chlorinated polyether polyurethan.

On the basis of the results of an earlier study, a particular polyurethan sample (Y-238) was selected for further evaluation of its carcinogenic potential. This sample was subjected to physical and chemical tests for elucidation of its chemical structure, molecular weight, and molecular weight distribution. Additional biological tests were conducted on male NBR rats by implanting various quantities of the sample i.p., while others received an intrabronchus implant. Tumors, assessed histologically as malignant, were observed following both routes of implantation. The most common neoplasms of the pulmonary site was epidermoid carcinoma, while fibrosarcoma was the most common neoplasm in the peritoneal cavity. Data from the i.p. implantation suggested a dose-related incidence of cancers.

Animals↗
PubMed1982

Accelerated loss of FEV- in polyurethane production workers: a four-year prospective study.

A four-year longitudinal study of ventilatory function in polyurethane-foam production workers exposed to toluene diisocyanate (TDI) revealed a dose-response relationship between average exposure to TDI and change in forced expiratory volume per second (FEV-1). Workers with mean exposure in excess of 0.0035 ppm showed a greater rate of decline of FEV-1 over the four-year period than that expected from aging. Factors other than TDI exposure (sex, smoking history, history of atopy) do not account for the loss. The current threshold limit value (TLV) for exposure to TDI in industry (0.02 ppm) does not protect workers from accelerated impairment of ventilatory capacity.

Cyanates↗
PubMed1998

Hydrophobic Aggregation in Polyurethane Ionomer Solutions.

Model polyurethane ionomers were synthesized with regularly spaced ionic groups along the polymeric backbone. Viscometry and static and dynamic light scattering applied to these ionomer solutions in a polar solvent, N-methylformamide, revealed hydrophobic interactions and aggregated ionomer chains in solution. A new regime in the solution behavior of ionomers characterized by low reduced viscosity at all dilute concentrations has been identified. Spherical particles of radius 30 nm with a polymer core and an outer ionic shell are formed. The solutions have very low viscosity because of the formation of compact structures. The electrostatic interactions in these solutions are effectively screened, resulting in the absence of polyelectrolyte behavior. Polymer-solvent interactions are found to be very important in determining the ionomer solution behavior in polar solvents. Copyright 1998 Academic Press.

Journal Article↗
PubMed1990

Effect of heat treatments on the house-dust mites Dermatophagoides pteronyssinus and D. farinae (Acari: Pyroglyphidae) in a mattress-like polyurethane foam block.

The behaviour and survival of the house-dust mites Dermatophagoides pteronyssinus and D. farinae were studied under laboratory conditions in a mattress-like polyurethane foam block that was heated by an electric blanket. Mites obtained from a laboratory culture were introduced into the foam block which was sliced into seven horizontal layers and covered with an electric blanket. Measurements of temperature and relative humidity were taken between the layers and the number of living mites was established using the heat-escape method.

Animals↗
PubMed2002

Polyurethane foams as solid chromogenic reagents for diffuse reflectance spectroscopy.

The chemical reactions of the functional groups in polyurethane foams (PUF) have been studied by use of diffuse reflectance spectroscopy and infrared spectroscopy. It was found that the functional groups are highly reactive towards diazotization by sodium nitrite, azo coupling with 4-nitrophenyldiazonium tetrafluoroborate, oxidation by active chlorine, and condensation with formaldehyde, resulting in the formation of intensely colored products. Heterogeneous chemical reactions of PUF with these compounds in aqueous solution proceed rapidly at room temperature and at low solute concentrations. PUF do not undergo degradation as a result of chemical interactions. The linear response of the Kubelka-Munk function to analyte concentration makes it possible to recommend PUF as solid chromogenic reagents for the determination of nitrite, nitrate, and 1- and 2-naphthols.

Journal Article↗
PubMed1990

Elution of disinfectant from polyurethane cannula tubing.

Cannula tubing (1.6 mm external, 1 mm internal diameter) was fabricated from medical grade polyurethane containing 2% 2,4,4'-trichloro-2'-hydroxydiphenyl ether ('Irgasan', Ciba-Geigy). When shaken with 10 ml of phosphate-buffered saline an equilibrium was set up with only traces of 'Irgasan' in the aqueous phase. When phosphate-buffered saline flowed through the tubing, 0.26 mg of 'Irgasan' per g of tubing per day was eluted, and this was not detectably increased by buffers of pH 3 or pH 8.5. However, a 20% lipid emulsion eluted 6 mg per g of tubing per day with a flow rate of 250 ml per day and 11 mg with a flow rate of 11 per day. These results scaled up show that a 7.11 g Hickman catheter would lose 78 mg of Irgasan in the first day with Intralipid, compared to 1.8 mg with PBS. If elution by tissue fluids (including blood) does not exceed that by Intralipid then comparison with available toxicological data suggests an adequate margin of safety for adults, but not for premature babies.

Anti-Infective Agents, Local↗
PubMed1990

7 g weighted versus unweighted polyurethane nasoenteral tubes--spontaneous transpyloric passage and clinical performance: a controlled randomised trial.

A proportion of patients requiring enteral nutrition is at increased risk of regurgitation or pulmonary aspiration of enteral diet as a result of gastric atony or paresis. The positioning of the distal end of an enteral feeding tube beyond the pylorus into duodenum or jejunum may reduce this risk. It has been postulated that by suitable lengthening of feeding tubes and by altering the distal end tip profile or by the addition of a weight, spontaneous passage of a tube through the pylorus after pernasal insertion may be achieved. In a recent controlled trial we were unable to demonstrate any advantage to a) modifying the tip profile or b) the addition of a 2.4 g weight. This prospective controlled clinical study examined the difference between an unweighted polyurethane tube which had performed optimally in the previous study and a new 7 g weighted tube similar in all other respects. In both cases less than 50% of tubes had passed spontaneously through the pylorus when assessed at 24 h, with no significant difference in performance (p = 0.38). When comparing overall length of time that each tube remained in situ, there was similarly no significant difference between the 7 g weighted and unweighted tubes (p = 0.277). We conclude that the addition of a 7 g weight to a suitably lengthened enteral feeding tube confers no advantage on either incidence of spontaneous transpyloric passage or in prolonging tube usage. If post-pyloric feeding is indicated for a patient, positioning by either fluoroscopic or endoscopic techniques should be undertaken.

Journal Article↗
PubMed1992

Performance of RBC coupled to a polyurethane foam to biodegrade petroleum refinery wastewater.

Biological treatment of petroleum refinery wastewater was studied in a rotating biological contactor (RBC) coupled to a polyurethane foam (PUF) as a porous biomass support. The PUF was attached on both sides of biodisks. The biodegradation studies were carried out at varying hydraulic and organic loadings. COD removal efficiency of up to 87% was achieved. The results obtained in terms of biodegradation of COD, NH3-N, phenol, hydrocarbons and suspended solids in this study were compared with those in the literature. The RBC-PUF bioreactor was found to have a better performance than a conventional RBC for the biodegradation of the above mentioned parameters. A higher concentration of active biomass (77 g TVS/m2) was observed in the RBC-PUF as compared to other treatment systems. A linear relationship between COD applied and COD removed was observed for the combined four stage system as well as for the individual stages.

Journal Article↗