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At least 325 records · Page 18Linked to original sources
PubMed2000

Performance of para-Pak Ultra ECOFIX compared with Para-Pak Ultra formalin/mercuric chloride-based polyvinyl alcohol for concentration and permanent stained smears of stool parasites.

ECOFIX is a mercury and formalin-free fecal preservative that can be used for concentration of stool specimens and preparation of permanently-stained slides. In this study, the standard two-vial ParaPak Ultra system was compared with ECOFIX Ultra for the detection of intestinal parasites. A total of 261 specimens in 92 sets (77 with 3 specimens, 15 with 2 specimens) were collected in ECOFIX, formalin, and low viscosity polyvinyl alcohol (LV-PVA). Concentrations were performed from ECOFIX using Hemo-De and saline and from formalin using ethyl acetate and formalin. To prepare permanently-stained smears, ECOSTAIN (a modification of Wheatley's trichrome stain) was used on ECOFIX material and Wheatley's trichrome stain was used on specimens preserved in PVA. A total of 157 protozoa and helminths were detected; 132 (84.1%) were recovered in formalin/PVA and 129 (82.2%) in ECOFIX. In permanently-stained smears, 139 protozoa were observed, 116 (83.5%) in PVA-preserved material and 117 (84.2%) in ECOFIX. Fecal concentration yielded 111 parasites (103 protozoa and 8 helminths), of which 98 (88.3%) were detected in formalin-fixed stool and 48 (43.2%) in ECOFIX. Significantly fewer ECOFIX-preserved concentrates were positive for Blastocystis hominis (35 versus 15, p-value <0.001) and Endolimax nana (19 versus 2, p-value <0.001). In conclusion, use of the ECOFIX Ultra collection device in combination with ECOSTAIN resulted in largely comparable recovery of enteric parasites to the conventional two-vial ParaPak Ultra system when both sedimentation-concentration and permanently stained smears were performed, and 2-3 specimens per patient were evaluated.

Feces↗
PubMed1994

Shear bond strength of orthodontic brackets cemented with a zinc oxide-polyvinyl cement.

The purpose of this study was to compare the shear bond strengths and enamel surface structure after debonding a conventional metal bracket and a polycrystalline ceramic bracket bonded with a bipolar zinc oxide-polyvinyl cement (F-21) or a light-cured resin cement (Transbond). Forty extracted human premolars were used. The buccal enamel surfaces were used, and the teeth randomly divided into four groups of 10 teeth each: group 1: conventional metal bracket (Unitek) bonded with Transbond; group 2: metal bracket bonded with F-21; group 3: ceramic bracket (Transcend 2000) bonded with Transbond; and group 4: ceramic bracket bonded with F-21. The brackets were bonded to the etched enamel surfaces according to manufacturer's instructions. All specimens were stored in distilled water for 24 hours and then thermocycled for 300 cycles between 5 degrees C and 55 degrees C. The specimens were mounted in dental stone and placed in the Instron at a crosshead speed of 0.5 mm/min with a knife-edged blade. Immediately after debonding, the enamel surface and bracket-enamel interface were evaluated visually and with a stereomicroscope. Representative samples were then examined with the scanning electron microscope. The analysis of variance and Student-Newman-Keuls tests were performed. The results in megapascals were Group 1: 19,6 (+/- 9,6); group 2: 14,3 (+/- 4,6); group 3: 28,8 (+/- 12,6); and group 4: 18,5 (+/- 7,5). Group 3 was statistically significantly different (P < 0.008) from all other groups. Groups 1, 2, and 4 were not significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)

Bicuspid↗
PubMed1999

Prolonged circulation time of doxorubicin-loaded liposomes coated with a modified polyvinyl alcohol after intravenous injection in rats.

The purpose of this study was to evaluate the functions of a modified polyvinyl alcohol (PVA-R), which has a hydrophobic moiety, as a coating material for liposomes to be loaded with the anticancer drug, doxorubicin. The size controlled liposomes (egg phosphatidylcholine: cholesterol=1:1 molar ratio) were prepared by the hydration method followed by extrusion. Drug encapsulation and surface modification with polymers (PVA and PVA-R) were carried out simultaneously using a modified pH gradient method. The existence of a thick polymer layer on the surface of the liposomes was confirmed by an increase in particle size and the amount of polymer on the liposomal surface, especially for the PVA-R-coated liposomes. The effects of polymer coating on the behavior of the liposomes in vivo were evaluated by measuring the circulation time and biodistribution of the drug after i.v. administration of the liposomal drug in rats. The PVA-R-coated liposomes showed a more prolonged circulating time for the drug with less uptake by the reticuloendothelial system after i.v. administration in rats, compared with non-coated liposomes. These results confirm that polymer possessing a hydrophobic anchor at its end, like PVA-R, is a suitable material for modifying the surface of doxorubicin-loaded liposomes to improve their stability in the circulating blood.

Animals↗
PubMed2003

Development of an artificial meniscus using polyvinyl alcohol-hydrogel for early return to, and continuance of, athletic life in sportspersons with severe meniscus injury. I: mechanical evaluation.

The importance of knee meniscus function is now recognized, and the treatment of meniscus injury has been changing from resection to repair. However, depending on the type of injury, meniscectomy sometimes cannot be avoided. The young athlete might undergo meniscectomy in order to return to sports life as early as possible. However, in such a knee, it is important to anticipate the future problem of degenerative change or osteoarthrosis. In consideration of the prognosis and circumstances in such patients, we have developed an artificial meniscus using polyvinyl alcohol-hydrogel (PVA-H) and performed mechanical tests for compression and stress-relaxation. We found that the human meniscus has unique viscoelastic properties and a high water content. PVA-H showed viscoelastic behaviour similar to that of human meniscus in mechanical tests. These results suggest that an artificial meniscus using PVA-H with a high water content can compensate for meniscal function and might be clinically applicable.

Athletic Injuries↗
PubMed2003

Development of an artificial meniscus using polyvinyl alcohol-hydrogel for early return to, and continuance of, athletic life in sportspersons with severe meniscus injury. II: animal experiments.

Due to the prognosis and sporting needs of young athletes who have severe meniscus injury, we have developed an artificial meniscus using polyvinyl alcohol-hydrogel (PVA-H). Biomechanical studies have shown that the human meniscus has various mechanical functions; in our mechanical tests, specimens of human meniscus (part I of this study) demonstrated unique viscoelastic properties. Those tests also showed that a high water-content PVA-H has very similar mechanical properties to those of human meniscus and potential as a substitutive meniscus implant. To assess further the use of PVA-H as an artificial meniscus, we have now performed animal experiments using a PVA-H with 90% water content. In rabbits, the lateral meniscus was replaced with an artificial meniscus in one knee of each animal and lateral meniscectomy was performed on the other side as a control. In the knees of meniscectomy group, degenerative changes in articular cartilage progressed with time and osteoarthritis was observed after 1 year. In the knees of the artificial meniscus group, regressive changes were initially observed, but did not progress, and knee joint function was good even after 1 year. Neither wear nor breakage were observed in artificial menisci. These results suggest that an artificial meniscus using a high water-content PVA-H might be clinically applicable.

Animals↗
PubMed1992

Polyvinyl formal surface promotes continuous growth of Vero cells in protein-free medium.

The effect of polyvinyl formal (PVF) culture surface on the growth of 10 mammalian continuous cell lines, including Swiss 3T6, NCTC clone 929 L, BHK-21 clone 13, CHO-K1, PK 15, A 431, HeLa, MDCK, LLC-MK2 and Vero in protein-free 1:1 mixture of Dulbecco's modified Eagle's medium and Ham's F12 supplemented with trace elements and L-ascorbic acid 2-phosphate, was investigated. Most of the cell lines showed only some initial proliferation on PVF similar to the polystyrene (PS) surface of commercially available culture flasks. In contrast, proliferation of monkey kidney cell line Vero was by far greater on PVF than on PS or poly-D-lysine treated culture surface. In addition, Vero cells on PVF could be subcultured in the protein-free medium without any significant decrease of growth rate in successive passages. These results showed that PVF provides a culture surface which selectively promotes continuous growth of Vero cells in protein-free, chemically defined medium.

Animals↗
PubMed2001

Portal vein embolization with use of polyvinyl alcohol particles.

Preoperative portal vein embolization has been used as method of inducing compensatory hypertrophy in the future remnant liver since it was first described in the late 1980s. Many different vascular embolic agents have been successfully used for this procedure, and there is no general consensus regarding which is the best agent. Polyvinyl alcohol (PVA) particles commonly used for arterial embolization come in many sizes, are readily available, and are easy to administer via conventional catheters. We describe an easy, safe, and effective method of the use of PVA particles for portal vein embolization.

Embolization, Therapeutic↗
PubMedDate not supplied

Histopathologic appearance of arterial occlusions with hydrogel and polyvinyl alcohol embolic material in domestic swine.

PURPOSE: This study observes the histologic changes resulting from a hydrogel embolic agent (polyacrylonitrile [PAN]) compared with polyvinyl alcohol particles (PVA) of similar size. MATERIALS AND METHODS: Hepatic and renal embolizations were performed in 13 domestic swine by selecting small (1-mm) branches utilizing a coaxial 3-F microcatheter. The hydrogel embolic agent (tantalum-loaded and plain) and PVA were delivered through microcatheters. The longest follow-up period was 8 weeks. Postmortem examination of the embolized tissues included gross examination and histologic analysis. RESULTS: Tantalum-loaded PAN particles were radiopaque and seen in groups fluoroscopically and individually with specimen radiography. Histologic studies showed similar luminal and cellular response to PVA and the hydrogel embolic agents. The arterial lesion induced by the hydrogel embolic agents led to an absence of the arterial wall locally in the area of deployment. Hydrogel embolic particles became surrounded in fibrous connective tissue with no arterial wall. PVA and porous hydrogel capsules produced an inflammatory response, resulting in less wall reorganization, and surrounding fibrous connective tissue at 8 weeks than the solid PAN particles. CONCLUSION: These hydrogel embolic create a permanent arterial occlusion by transmural arterial damage. Mechanical effects and, to a lesser degree, inflammatory changes are responsible.

Acrylic Resins↗
PubMedDate not supplied

Attempted induction of chronic portal venous hypertension with polyvinyl alcohol particles in swine.

PURPOSE: Creation of presinusoidal chronic portal venous hypertension by means of repeated portal vein (PV) embolization was explored in an attempt to improve a porcine model of transjugular intrahepatic portosystemic shunt (TIPS) patency. MATERIALS AND METHODS: Six microswine underwent weekly PV embolization for 5 weeks with a total of 10.4-12.6 g of polyvinyl alcohol (PVA) particles (0.149-0.250 mm in size). Portography, liver function tests, pressure measurement in the PV and inferior vena cava (IVC) before and after PV embolization, and histopathologic evaluation of the livers were performed. RESULTS: Transhepatic portal venography performed after each embolization demonstrated diffuse PV branch occlusion in all cases. At weekly follow-up, reconstitution of flow was demonstrated in these branches; permanent occlusion of PV branches was not achieved. The mean PV pressure elevated acutely from 17.3 mm Hg +/- 0.9 to 24.5 mm Hg +/- 4.2 (P < .01) after each embolization. However, the pressure always returned to baseline on the follow-up studies 1 week later. Liver function tests were normal. Histopathologic evaluation of the liver showed, in multiple PV branches, central plugs of PVA with peripheral recanalization. The liver parenchyma was otherwise normal. CONCLUSION: Massive embolizations of PV with PVA at weekly intervals failed to create permanent portal hypertension or induce hepatic fibrosis.

Animals↗
PubMedDate not supplied

Polyvinyl alcohol foam particle sizes and concentrations injectable through microcatheters.

PURPOSE: Injection of different size ranges and concentrations of polyvinyl alcohol (PVA) foam particles was performed to determine the optimal and maximum size ranges and concentrations that may be injected reliably through microcatheters used for vascular embolization. MATERIALS AND METHODS: Eight different microcatheters were tested. Six different size ranges of PVA foam particles (three each from two manufacturers) at three different concentrations were tested with each catheter. All PVA foam particles were suspended in dilute low-osmolarity contrast material. For each size range and concentration of PVA foam particles, sixty 1-mL injections were made into each catheter tested. Continuous pressure monitoring was employed during all injections. RESULTS: For each catheter, the authors determined recommended maximum size ranges of PVA foam particles that may be injected with reasonable pressure and minimal risk of inadvertent catheter occlusion. Among the four catheters used with 0.014-0.016-inch guide wires, the authors found that PVA foam particles as large as 1,000-1,500 microm could be injected without catheter occlusion. PVA foam particles as large as 710-1,000 microm could be injected through one catheter used with 0.010-0.013-inch guide wires. Particles as small as 300-500 microm occluded the other catheter used with the same size guide wires. Both of the flow-directed microcatheters tested would allow injection of PVA foam particles as large as 355-500 microm. CONCLUSION: Given the recent proliferation of microcatheters, improved understanding of maximum PVA foam particle size ranges and concentrations that can be injected through them will help prevent inadvertent catheter occlusion during embolization. Because the authors' results are based on a simulated high-flow vascular lesion, they may not be applicable in all circumstances. Embolization of low-flow lesions, however, should not require use of the maximum possible size and concentration of PVA foam particles.

Catheterization↗
PubMed1999

Chemoembolization of hepatocellular carcinoma with cisplatin, doxorubicin, mitomycin-C, ethiodol, and polyvinyl alcohol: prospective evaluation of response and survival in a U.S. population.

PURPOSE: To evaluate response and survival after hepatic chemoembolization with cisplatin, doxorubicin, mitomycin-C, Ethiodol, and polyvinyl alcohol in a U.S. population of patients with hepatocellular carcinoma. MATERIALS AND METHODS: Thirty-eight consecutive patients were treated: 35% stage I, 62% stage II, 3% stage III. Fifty-one percent had cirrhosis. Chemoembolization was performed at approximately monthly intervals for one to seven sessions (mean, 2.2). Pretreatment and posttreatment cross-sectional imaging and alpha-fetoprotein (AFP) levels were obtained prospectively 1 month after treatment and then every 3 months. Thirty-day response was calculated by means of the the World Health Organization/Eastern Cooperative Oncology Group criteria. RESULTS: One patient was lost to follow-up. In seven patients, lesions became resectable after chemoembolization. Among 13 evaluable patients with initially elevated AFP level, 70% had a partial biologic response (>50% decrease in AFP), 15% had a minor response (25-50% decrease), and the remaining 15% remained stable. Among 25 patients evaluable for morphologic response, 36% had a partial response, 32% had a minor response, and 32% remained stable. No patients had progression of disease while receiving therapy. The cumulative survival was 60% at 1 year, 41% at 2 years, and 16% at 3 years. Two patients developed progressive hepatic failure. Thirty-day mortality was 3% (one patient). CONCLUSION: These results compare favorably to published response and survival data for chemoembolization of advanced hepatocellular carcinoma from Asia and Europe.

Antibiotics, Antineoplastic↗
PubMed1988

Fractures in polyvinyl chloride tracheostomy tubes.

Fracture in polyvinyl chloride tracheostomy tubes in infants and children has not previously been described. On the basis of two events in the same infant a theory for the pathogenesis is outlined, and measures to prevent future cases are described.

Equipment Failure↗
PubMedDate not supplied

Preparation and evaluation of polyvinyl alcohol-co-oleylvinyl ether derivatives as tumor-specific cytotoxic systems.

A series of poly(vinyl alcohol) amphiphilic derivatives have been prepared to obtain polymeric aggregates in aqueous phase holding thermodynamic instability. The aim was to evaluate their ability to interact with tumor cells eliciting selective cytotoxicity. The poly(vinyl alcohol) derivatives were prepared by partial substitution of poly(vinyl alcohol) (MW 10 kDa) with both oleyl chains and poly(ethylene glycol) monoethyl ethers (PEGMEE) of different molecular weights. The substitution degree was 1.5% for the oleyl chains and 1% for the PEGMEE chains (moles of substituent per 100 mol of hydroxyvinyl monomer). The polyvinyl derivatives obtained easily dissolved in water. Dynamic and static light scattering measurements on the polymer aqueous solutions indicated the formation of polymeric aggregates characterized by low polydispersity (0.232-0.299) and mean size (218-382 nm) in the range suitable for intravenous administration. Moreover, they were characterized by different packing densities and thermodynamic instabilities driving the polymers to interact with hydrophobic membranes. Among the analyzed polymers, the poly(vinyl alcohol)-co-oleylvinyl ether substituted with triethylene glycol monoethyl ether (P10(4)) provided in solution the highest affinity for hydrophobic membranes. P10(4), moreover, was the most cytotoxic toward the tumor cell lines analyzed (neuroblastoma: SH-SY5Y, IMR-32, HTLA-230. melanoma: MZ2-MEL, RPMI7932.), while it did not appreciably alter the viability of the normal resting lymphocytes. The peculiar behavior of the P10(4) aggregates has been correlated to their high thermodynamic instability in solution due to the high packing density that triggers the polymeric aggregates to interact with hydrophobic membranes such as the tumor cell membranes, thus eliciting cytotoxicity.

Antineoplastic Agents↗
PubMed2005

Uptake of polychlorinated biphenyls (PCBs) from an aqueous medium by polyethylene, polyvinyl chloride, and polystyrene films.

The sorption of selected polychlorinated biphenyl (PCB) congeners (from tri to deca chlorinated) by three food-packaging plastic films [polyethylene, polyvinyl chloride (PVC), and polystyrene] from an aqueous solution was investigated. From the data generated, PCB uptake, partition, and diffusion coefficients were calculated for the various films. Polyethylene exhibited the highest PCB uptake, diffusion, and partition coefficients when compared to the other materials. Although PVC indicated larger sorption diffusion and partition coefficients for the lower chlorinated congeners than polystyrene, a reversal of this trend was observed for the higher congeners. For polyethylene and PVC, the PCB uptake decreased as the chlorine numbers in the congeners increased, confirming the correlation between increasing chlorination and increasing cohesive density within the PCB molecules. For polystyrene, the uptake decreased from tri to penta congeners, but showed an increase for the hexa, and then a decreased uptake until the deca chlorination. A comparison of the molecular sizes of the PCB congeners showed that the partition (Ke) and sorption diffusion (Ds) coefficients generally decreased with their increasing molar volumes. The resulting Ke values were used to determine the extent of sorption because these values indicate the affinity of PCBs for the plastic films. Results from this study can be of practical importance for cases of product quality related to the transfer of contaminants from the product to the packaging materials.

Food Packaging↗
PubMed2004

Ultrasensitive potentiometric immunosensor based on SA and OCA techniques for immobilization of HBsAb with colloidal Au and polyvinyl butyral as matrixes.

A novel potentiometric immunosensor for detection of hepatitis B surface antigen (HBsAg) has been developed by means of self-assembly (SA) and opposite-charged adsorption (OCA) techniques to immobilize hepatitis B surface antibody (HBsAb) on a platinum electrode. A cleaned platinum electrode was first pretreated in the presence of 10% HNO3 and 2.5% K2CrO4 solution and held at -1.5 V (vs SCE) for 1 min to make it negatively charged and then immersed in a mixing solution containing hepatitis B surface antibody, colloidal gold (Au), and polyvinyl butyral (PVB). Finally, HBsAb was successfully immobilized onto the surface of the negatively charged platinum electrode modified nanosized gold and PVB sol-gel matrixes. The modified procedure was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The immobilized hepatitis B surface antibody exhibited direct electrochemical behavior toward hepatitis B surface antigen (HBsAg). The performance and factors influencing the performance of the resulting immunosensor were studied in detail. More than 95.7% of the results of the human serum samples obtained by this method were in agreement with those obtained by enzyme-linked immunosorbent assays (ELISAs). The resulting immunosensor exhibited fast potentiometric response (<3 min) to HBsAg. The detection limit of the immunosensor was 2.3 ng.mL(-1), and the linear range was from 8 to 1280 ng.mL(-1). Moreover, the studied immunosensor exhibited high sensitivity, good reproducibility, and long-term stability (>6 months).

Adsorption↗
PubMed1989

Polyvinyl alcohol-methyl acrylate copolymers as a sustained-release oral delivery system.

Low crystalline and crystalline polyvinyl alcohol-methyl acrylate (PVA-MA) copolymers were examined, because of their excellent flow and compressibility properties, as matrices for sustained-release tablets using phenylpropanolamine hydrochloride (PPA.HCl) as a model drug. Crystallinity of the copolymer affected the release characteristics from the tablet. Tablets made with low-crystalline PVA-MA provided sustained release of PPA, both in vitro and in vivo in dogs. PPA absorption from the low-crystalline PVA-MA tablet formulation was biphasic. An initial rapid phase was followed by a second, slower absorption phase which continued over 16 hr. Plasma PPA concentrations then declined with a half-life roughly parallel to the oral immediate-release half-lives. Oral bioavailability from the low-crystalline PVA-MA tablet formulation was 78.8 +/- 3.9%.

Acrylates↗
PubMed1989

Evaluation of polyvinyl alcohol hydrogel as a sustained-release vehicle for rectal administration of indomethacin.

In order to evaluate an indomethacin polyvinyl alcohol (PVA) hydrogel for rectal administration, the in vitro release characteristics of indomethacin from the hydrogel and indomethacin plasma concentrations after rectal administration were examined. The PVA hydrogel containing indomethacin was prepared by a low-temperature crystallization method. The release of indomethacin from the PVA hydrogel agreed with the Fickian diffusion model for 10 hr. Rectal administration of indomethacin hydrogels to rats yielded high indomethacin plasma concentrations, without producing a sharp peak, and a sustained-release effect. In dogs, the indomethacin hydrogel produced a similar sustained-release effect; however, the indomethacin plasma concentration was relatively low compared with that of an indomethacin suppository.

Administration, Rectal↗
PubMed2003

Immobilization of Pseudomonas delafieldii with magnetic polyvinyl alcohol beads and its application in biodesulfurization.

Pseudomonas delafieldii was immobilized in magnetic polyvinyl alcohol (PVA) beads using a hydrophilic magnetic fluid, which was prepared by a co-precipitation method. The beads had distinct super-paramagnetic properties and were compared with immobilized cells in non-magnetic PVA beads. Their desulfurizing activity was increased slightly from 8.7 to 9 mmol sulfur kg(-1) (dry cell) h(-1). The main advantages was that the magnetic immobilized cells maintain a high desulfurization activity and remain in good shape after 7 times of repeated use, while the non-magnetic immobilized cells could only be used for 5 times. Furthermore, the magnetic immobilized cells could be easily collected or separated magnetically from the biodesulfurization reactor.

Bacterial Adhesion↗