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At least 595 records · Page 33Linked to original sources
PubMed2002

[A study on the mechanism of bFGF promoting endothelial cells to adhere to polyurethane material].

bFGF can promote endothelial cell to adhere to artificial polyurethane material. However the mechanism is still unclear. Here the effect of bFGF on endothelial cell expression of integrin beta 1 subunits was determined with Western Blot and image analysis method. The result reveal that the mean gray value of immunostain is 166.1 +/- 9.86 in the experimental group and 175.32 +/- 5.12 in the control group, suggest that bFGF may upregulate the endothelial cell expression of integrin beta 1 subunits. It is concluded that the bFGF may induce the overexpression of endothelial cell integrin beta 1 subunits to increase the cell adhesion onto polyurethane material. It is suggested that bFGF can be taken as an important assistant factor in accomplishment of endothelialization on artificial heart and blood vessel.

Animals↗
PubMed2003

A laboratory observation of some toxic effects of commercially available implant polyurethanes on HL-60 cancer cells.

We studied the interaction of HL-60 cells with films of commercial polyurethanes (PU). The cast films were dried in an oven at 60 degrees C for forty eight hours, washed in doubly distilled water, and soaked in fresh water for another 48 hours to ensure that all of the leachables including the dimethylacetamide used as casting solvent was removed before they were introduced to the cells. The HL-60 cells were cultured in the RPM1-1640, at 37 degrees C, 100% humidity and 5% CO2. Evaluation of the effects between the cells and the films, was done by counting the live cells using a hemacytometer and a light microscope. Preliminary analysis of our data have shown that while some brands of polyurethane can slow down or suppress the growth of the phagocytic type of cells, others can enhance the cell growth. It was concluded that this observation was new but should be investigated further to better understanding the interactions which may lead to the development of in vitro methods for screening the safety and stability of PU intended for implantation.

Biocompatible Materials↗
PubMed1992

Clinical evaluation of percutaneous insertion and long-term usage of a new cuffed polyurethane catheter for central venous access.

A new, long-term venous access catheter was evaluated in clinical practice and the insertion time, complication rate and prospective follow-up recorded. Fifty novel polyurethane catheters (Cuff-Cath) were inserted in 48 patients, for cytotoxic chemotherapy in 36, long-term total parenteral nutrition in five and miscellaneous indications in seven. All catheters were inserted by a percutaneous technique under local anaesthesia. The mean insertion time was 18 min. There were three insertion complications; failure to cannulate, pneumothorax and malposition. Seven catheters required removal (sepsis in five, subclavian vein thrombosis in two) and one catheter fell out. Total catheter days to date has been 6607 (mean 132, range 18-831 days). Eleven catheters are still in use a mean of 154 days (range 38-490 days) after insertion. Furthermore, a new technique has been described which prevents inadvertent displacement. This new catheter combines the mechanical advantages of polyurethane, together with those of a Dacron cuff. Early results suggest that this catheter may be a useful alternative to silicone catheters of the Hickman/Broviac type for long-term central venous access.

Antineoplastic Agents↗
PubMed2004

[Assessment of the emission of volatile organic compounds from polyurethane foams].

The emission of 2,4- and 2,6-diaminotoluene, triethylenediamine, diethanolamine and other volatile organic compounds from polyurethane foams was examined in environmental chamber. Tested materials did not release of amines. The emission of total volatile organic compounds showed differences for polyurethane samples but did not exceed ecological standards.

Air Pollutants↗
PubMed1992

T lymphocyte modification with the UTA microporous polyurethane vascular prosthesis: in vivo studies in rats.

Sequential quantification of blood T cell subsets by immunocytofluorometry was used to investigate the immune response of microporous polyurethane vascular prostheses after intraperitoneal implantation in rats. The experimental prosthesis, as developed by the University of Texas-Arlington group (UTA), and the Mitrathane prosthesis, as developed by Matrix Med., were implanted for 1, 2 and 6 weeks and compared with ePTFE and wounded rats without prostheses (control group). The implants were examined for histopathology by light microscopy. The percentages of CD4-(helper) and CD8-(suppressor) bearing cells of the PTFE group were significantly lower (p less than 0.05) than the control group 1 week post-implantation. The UTA and the Mitrathane grafts exhibited a significant decrease in both T cell subsets at 1 week, and CD4-bearing cells at 2 weeks. At 6 weeks, T cell subsets were similar among all groups. The ratio of CD4/CD8- cells was similar among all groups except for the PTFE group, which was lower than the control group after 1 week. Histological examination of Mitrathane and UTA grafts showed an acute phase of inflammation which lasted at least 2 weeks. Some foreign body giant cells (FBGC) were present 2 weeks post-implantation, and encapsulation was greater than that observed with PTFE grafts. On the other hand, PTFE grafts exhibited a different pattern of inflammation compared to polyurethane grafts. PTFE implants exhibited a moderate chronic inflammatory response for the first week, as shown by the formation of FBGC. At 2 and 6 weeks, the grafts were encapsulated by a thin layer of collagenous tissue and FBGC were still present around the implants, mostly located in contact with the reinforcing mesh.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Development and long-term fate of a cellular lining in fibrous polyurethane vascular prostheses implanted in the dog carotid and femoral artery. A scanning and light microscopical study up to 53 months after implantation.

The development and long-term fate of the inner cellular lining in 72 small caliber (3 mm inner diameter) fibrous polyurethane vascular prostheses explanted from dog carotid and/or femoral arteries at times ranging from 1.5 weeks up to 53 months after implantation were studied by scanning electron and light microscopy. A continuous cellular ingrowth from the vascular stumps into the 3 cm long prostheses was observed, which eventually resulted in a complete cellular lining 6 months after implantation. No other ways of endothelialization were noted. In fully endothelialized prostheses, the cellular ingrowth extended approximately 8 mm into the prostheses and consisted of several layers of fibroblasts and smooth muscle cells, covered by a very thin endothelioid cell layer. The newly developed lining was firmly anchored onto the inner prosthetic surface by means of cellular protrusions extended into the fibrous texture of the prosthetic wall. It was concluded that under experimental conditions in the dog complete endothelialization can be obtained in fibrous polyurethane vascular prostheses and that the lining remained thin and stable throughout the observation period of 53 months after implantation.

Anastomosis, Surgical↗
PubMed2006

[Study on synthesis of physically crosslinked biomedical polyurethane hydrogel].

In this study, using ethylene carbonate and ethanolamine, we synthesized a novel diol chain-extender, bis-hydroxylethyl carbomate (EC-AE), which contains carbomate structure. The polyurethanes, PUA25 and PUB25, with different extenders, EC-AE and BDO, were synthesized by one-step polymerization, respectively. Their structures were characterized by using FT-IR and DSC. The results indicated that the microphase separation degree of PUA25 was less than that of PUB25, in other words, the amount of hydrogen bonding between hard segments and soft segments in PUA25 was superior to that in PUB25. And the formation of physically crosslinked hydrogels prepared by PUA25 and PUB25 were studied in detail. It was found that only PUA25 can form hydrogel in situ from solution state by cooling. And this kind of hydrogels showed the transition cycle of "gel-sol-gel" under "cooling-heating-cooling" thermal cycles, respectively. The results suggested that the physically crosslinked polyurethane hydrogels were easily possessed in high degree of phase mixing.

Biocompatible Materials↗
PubMedDate not supplied

Evaluation of a stented polyurethane mitral valve prosthesis.

In the search for the perfect valve prosthesis, polyurethane has been used for its excellent physical properties, but thrombosis and embolism have been real problems. The authors investigated the performance and durability of a 23 mm vacuum formed polyurethane Tricuspid Semilunar Valve, in the mitral position. The valve was implanted in eight sheep using standard cardiopulmonary bypass and intermittent aortic cross clamping. Two early failures were due to valve tears. After modification of the manufacturing process, six further valves were implanted in six sheep. All were anticoagulated with warfarin. The valves were calcified on echocardiography and had increasing transvalvular gradients beginning 3 months postoperatively. All six survived and were killed 1-2.5 years after implantation. Despite gross calcification of the leaflets, medium-term function was good. Careful serial sections of brain showed no evidence of thromboembolism. Both kidneys contained small calcium emboli, but no evidence of infarction. Despite calcification, with good medium-term function and no cerebral emboli, this valve may find application in temporary cardiac assist devices.

Animals↗
PubMed1991

[Embolus formation using bismuth polyurethane for tubosterilization observation of 259 cases].

A 50% solution of bismuth polyurethane in absolute alcohol, which remains in a liquid state at 70 degrees C and solidifies at body temperature within a few minutes, was used to form embolus in the fallopian tubes for the purpose of tube-sterilization. This compound is non-caustic and proves to be bioadaptable. A modified Foley's catheter was used to introduce the solution into the lumens of the tube by way of the uterine cavity in 259 cases. A 24 month follow-up by life table method was carried out, and 26 were pregnant with a pregnancy rate of 10.0%. The number of successful operation at the first attempt was 234 with 18 cases pregnant (7.7%). The recanalization rate of the tubes within 24 months was 11.4% including those of pregnancy. There was little side reactions postoperatively. A polyethylene 2 way tube with a rubber bulb for instillation of the bismuth polyurethane had been made on October 1990. Ways of improving the successful rate were mentioned. The authors believe that this is a useful procedure of tubo-sterilization, which is easily accepted by the patients and easily carried out by the medical personnel.

Bismuth↗
PubMedDate not supplied

[Phosphatase activity and level of cyclic nucleotides upon implantation of polyurethane with lactose in the main chain].

Activity of hydrolases, acid and alkaline phosphatases (AP and A1P) in connective-tissue capsules as well as the amount of cyclic nucleotides in the rat blood plasma with implantation of polyurethane on the basis of polyoxytetramethylenglycol and 4,4'-diphenylmethane diisocyanate with lactose in the main chain were studied. Data obtained indicate that polyurethane with lactose in the main chain is biocompatible and nontoxic and may be recommended for the purposes of endoprosthesis.

Acid Phosphatase↗
PubMed1990

[Long-term results following implantation of breast prosthesis with a polyurethane coating].

42 of 63 cases of bilateral augmentation mammaplasty using polyurethane-covered prostheses, so-called Ashley "Natural-Y" prostheses were seen 15 to 17 years after the primary operation. Two implants had previously been replaced by Cronin gel type prostheses for various reasons. The 84 breasts which were examined in follow-up compared well with breasts augmented with other devices as far as capsular contracture was concerned. The extreme difficulty of removing these implants because of the deterioration of the polyurethane cover makes any further use of these implants unjustifiable.

Breast↗
PubMedDate not supplied

Development of a polyurethane percutaneous access device for long-term vascular access.

The percutaneous placement of intravascular devices creates a portal for microbial invasion that can result in local infections or septicemia. In nature, resistance to "exist site" infection in percutaneous organs, such as teeth, is prevented by a dense collagen/epithelial barrier. A new percutaneous access device has been developed that incorporates a porous polyurethane "button" at the subdermal level. This device promotes the development of a collagen/epithelial interface, thus inhibiting sinus formation. Twelve percutaneous access devices (PCADS) were implanted in calves; eight devices were utilized for venting of, and hard wire passage to, an implantable left ventricular assist device (LVAD) and served as controls. Four devices were utilized for long-term vascular access. The PCADS remained in situ for 2-127 days (mean 70). Excellent healing was apparent in all cases, and no exit site or catheter related infections occurred. Histologic examination demonstrated fibroblastic in-growth and collagen deposition within the porous polyurethane, which provides a barrier to epithelial migration and firmly anchors the device. These PCADS appear to reduce exit site infections and may improve upon currently available long-term vascular access catheters.

Animals↗
PubMedDate not supplied

Behavior of platelets and leukocytes on the luminal surface of small caliber polyurethane grafts.

With scanning electron microscopy, we examined the behavior of platelets and leukocytes on the luminal surface of small caliber polyurethane grafts implanted into small arteries of dogs. Thirty-five grafts were implanted to the carotid and/or femoral arteries. The animals were treated with aspirin and/or DN9693, an inhibitor of phosphodiesterase. In the group treated with aspirin (40 mg/kg i.v.), the deposition of platelets on the luminal surface of the implanted polyurethane grafts was suppressed and the luminal surface was covered with adherent leukocytes. Fibrin nets were formed on the adherent leukocytes. In addition, the adhesion of leukocytes on the grafts was considerably suppressed in the group treated with DN9693 (50 micrograms/kg/min i.v.), and the formation of fibrin nets was markedly reduced. In contrast, in the control group the luminal surface was covered with numerous platelets and some leukocytes, which formed thrombi. These findings suggest that leukocytes adhere primarily to the prosthetic graft and play an important role in the initiation of fibrin formation.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1989

Prevention of platelet aggregation by dietary polyunsaturated fatty acids in the biodegradable polyurethane vascular prosthesis: an experimental model in pigs.

A 6-7 cm long degradable polyurethane vascular prosthesis was implanted in the infrarenal aorta of 25 young growing pigs, sacrificed from day 30 to 365 to study the processes of degradation and tissue growth, the characteristics of prosthetic substitutes and the incidence of thrombosis. Ten animals were used as controls and 15 were fed with cod liver oil (25 ml twice daily). Aortography performed at day 30, 60 and 90 showed 100% thrombosed implants in the controls, while in the lipid diet fed animals there was 100% patency. At graft retrieval, there were 7 patent grafts out of 9 in the cod liver oil fed animals. Laboratory tests indicated that the lipid diet rich in n-3 polyunsaturated fatty acids induces significant modifications of lipid metabolism preventing platelet aggregation. These data correlate well with findings of the morphological studies showing that all patent prostheses are lined with tissues similar to the endothelium of the native aorta with a mid layer made of circular and longitudinal smooth muscle cells well differentiated at day 180. These data show that the essential polyunsaturated fatty acid rich diet is able to prevent thrombosis of the biodegradable polyurethane vascular prosthesis. The combination of a synthetic material and the lipid diet experimental model, makes it possible to assess the long-term tissue-synthetic material interaction and the process of tissue growth.

Animals↗
PubMed1989

Tests of two new polyurethane foam wheelchair tires.

The performance characteristics of four 24-inch wheelchair tires are considered; one pneumatic and three airless. Specifically, two new airless polyurethane foam tires (circular and tapered cross-section) were compared to both a molded polyisoprene tire and a rubber pneumatic tire. Rolling resistance, coefficient of static friction, spring rate, tire roll-off, impact absorption, wear resistance, and resistance to compression set were the characteristics considered for the basis of comparison. Although the pneumatic tire is preferred by many wheelchair users, the two new polyurethane foam tires were found to offer a performance similar to the high-pressure pneumatic tire. In addition, the foam tires are less expensive and lighter in weight than the other tires tested.

Equipment Design↗
PubMedDate not supplied

Endothelialization of polyurethane vascular prostheses implanted in the dog carotid and femoral artery.

A new type of vascular prosthesis made of polyurethane with a fibrous structure of the wall was implanted in the carotid and/or femoral artery of dogs. The healing process and neo-intima formation after implantation of this type of prosthesis was followed with light- and scanning electron microscopy. A total of 18 prostheses, which had been implanted for 1, 3, 6, 9 or 20 weeks were studied. Endothelial like cells invaded the prosthesis over the anastomoses, starting the first week after implantation. The growth zones advanced steadily, and prostheses measuring 3 cm in length were completely endothelialized by 20 weeks after implantation, a mean growth rate of the endothelial like cells of 0.09 mm/day. Subsequently, fibroblasts and smooth muscle cells grew between the neoendothelial layer and the prosthetic inner surface, forming a new multi-layered neo-intima. Cellular elements of the neo-intima were firmly anchored onto the inner wall of the prosthesis by cells with extending cytoplasmic protrusions between the fibers of the prosthetic wall. Since in this type of fibrous polyurethane prosthesis, endothelial like cells continually grew until a new lining was formed, apparently facilitated by the fibrous structure of the wall, further investigations are indicated for progression toward clinical implantation of this type of prosthesis.

Animals↗
PubMedDate not supplied

Electron capture detection-gas chromatographic determination of diaminotoluenes in polyurethane foam as heptafluorobutyryl derivatives.

A simple gas chromatographic (GC) method has been developed to determine 2,4- and 2,6-diaminotoluenes in polyurethane foam. Diaminotoluenes were reacted with heptafluorobutyric anhydride in toluene, and the products, bis-heptafluorobutyrates, were determined by GC, using a 3% silicone OV-330 column. The 2,4- and 2,6-diaminotoluenes can be detected as heptafluorobutyryl derivatives by using an electron capture detector at levels of 5 and 2 pg, respectively. Finally, 2.7-3.0 micrograms/g of 2,4- and 1.3-1.9 micrograms/g of 2,6-diaminotoluene were detected in 3 commercial polyurethane foams.

Chromatography, Gas↗