The effect of polyvinyl alcohol and polyvinyl pyrrolidone on diffusion artifacts in lactate dehydrogenase histochemistry.
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Animals↗
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Some effects of polyvinyl alcohol and polyvinyl pyrrolidone on the activity of lactate dehydrogenase and its isoenzymes. Histochemical and biochemical studies.
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Animals↗
[Experimental canine hepatic artery embolization with polyvinyl alcohol microspheres].
Polyvinyl alcohol microsphere impregnated with barium sulfate was found to be a good embolizing agent in regard to shape, suspension and distribution in the arteries. Different-phase hepatic artery embolization with microspheres (50 approximately 100 microns, 100 approximately 300 microns) was performed in 20 dogs to evaluate the angiographic and histopathologic changes and hepatic function alterations. Permanent occlusion of the peripheral arterioles was observed on follow-up angiograms one week to six months after embolization. Shrinkage of the embolized segment and focal infarct of the liver were noticed in nearly half of the specimens both grossly and microscopically. The shape and structure of the microspheres were seen unchanged on different-phase specimens, and microspheres as small as 50 microns could reach the corresponding small peripheral arterioles. The liver function alterations were comparable with gelfoam embolization. This study suggested that permanent embolization of small arterioles was possible with such microspheres.
Animals↗
Histopathological follow-up study of 66 cerebral arteriovenous malformations after therapeutic embolization with polyvinyl alcohol.
Embolization with polyvinyl alcohol (PVA) is an accepted method of rendering complex arteriovenous malformations (AVM's) more amenable to surgery, but its effects on human vascular tissues have not been adequately documented. The authors reviewed the histopathology of 66 intracranial AVM's resected 1 to 76 days after embolization with PVA. The mean age of the patients was 36 years, and their AVM's were located in the cerebral hemispheres (92%), the cerebellum (6%), or the corpus callosum (2%). In 79% of cases, at least one vessel contained PVA particles; in most cases, the vessel was filled with sharp, angular PVA particles in a serpiginous pattern. Polyvinyl alcohol particles indented the endothelium in 69% of cases but were rarely found subendothelially. Clotted blood and fibroblasts were present among the particles, and abundant intraluminal mononuclear and polymorphonuclear inflammatory cells were found in all vessels containing PVA particles. Foreign-body giant cells appeared 2 to 14 days after embolization in the majority of cases. Patchy mural angionecrosis and necrotizing vasculitis were found in 39% of the cases. Recanalized lumina were seen in 18% of PVA-embolized vessels. Foreign materials resembling cotton fibers and other particulate substances, which were probably contaminants of the contrast solution or the embolic material, were found in 65% of the cases. These findings suggest a specific chain of events in the interaction between PVA and vessel wall components and may explain some important sequelae of embolization therapy.
Adolescent↗
Effect of addition of alcohols on gelation of polyvinyl alcohol aqueous solution by gamma-ray irradiation.
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Alcohols↗
[Therapeutic embolization with polyvinyl alcohol (Ivalon). Clinical experiences].
Polyvinyl alcohol is rigid foam used in pressed or unpressed form for the purpose of embolisation. It is suitable for both micro-embolisation in the vascular periphery and for central vascular occlusion. Polyvinyl alcohol will result in permanent vascular occlusion. Basing on the experience collected with 71 embolizations, the article reports on the technique applied and on the results obtained with craniofacial, thoracic, abdominal, pelvic and peripheral embolisation.
Adolescent↗
Preparation and thrombogenicity of alkylated polyvinyl alcohol coated tubing.
A polyvinyl alcohol hydrogel (PVA) was reacted with a C18 isocyanate at 80 degrees C in dimethyl formamide (DMF) in order to improve the platelet reactivity of the hydrogel through an influence on albumin adsorption or retention. A C4 isocyanate was used as a control. Surface coverage by XPS appeared to be approximately 100% for both C4 and C18 modified surfaces, although the limited solubility of C18 isocyanate in DMF may have resulted in a nonuniform surface. Relative to PVA or the solvent treated control, octadecylation resulted in increased albumin adsorption (from a single protein solution) and increased retention when the adsorbed albumin was exposed to a fibrinogen solution. However, octadecylation did not obviate the platelet reactivity problem in preliminary studies: systemic platelet counts were reduced by about half over 4 days in a canine AV shunt experiment and the initial rate of platelet destruction for C18-PVA was greater (36%/day) even than for the solvent-treated PVA. Surprisingly in preliminary studies butylation of PVA resulted in little or no thrombocytopenia and did not appear to increase significantly the fractional rate of platelet destruction relative to the shunt only blank. It is presumed that the nonspecific effect of alkylation (independent of chain length) was the dominant contribution to the reduced platelet reactivity. A similar effect of C18-PVA presumably would have been observed had the limited solubility of C18 isocyanate not precluded a uniform surface coverage.
Adsorption↗
A quantitative study of the effects of different grades of polyvinyl alcohol on the activities of certain enzymes in unfixed tissue sections.
Different grades of the colloid stabilizer, polyvinyl alcohol, used for protecting unfixed cryostat sections during cytochemical reactions, may have different effects on enzymatic activity. The influence of three grades of polyvinyl alcohol on the activities of "soluble", membrane-bound and membrane-enclosed enzymes has been investigated in unfixed sections; the activities were measured microdensitometrically. The largest molecular weight polyvinyl alcohol (G18/140, mol. wt. about 90 000) did not retain glucose-6-phosphate dehydrogenase activity in sections of rat liver even when used at the maximum convenient concentration (12%); G04/140 and M05/140 (molecular weights of 15 000 and 25 000 respectively) retained this soluble enzyme if used at concentrations of 30 and 20% respectively. At these concentrations, lactate dehydrogenase activity was apparently decreased when G04/140 and M05/140 were used; this diminished activity has been shown to be due to the need to establish optimal concentrations of reactants for each grade of polyvinyl alcohol and for each reaction. When optimal concentrations of reactants were used, the activities of this enzyme in the presence of each grade of polyvinyl alcohol were identical. The presence of any type of polyvinyl alcohol did not influence the activities of mitochondrial succinate dehydrogenase or of the smooth endoplasmic reticulum enzyme, delta5,3beta-hydroxysteroid dehydrogenase. However, the presence of polyvinyl alcohol improved the state of the section.
3-Hydroxysteroid Dehydrogenases↗
Experimental hybrid islet transplantation: application of polyvinyl alcohol membrane for entrapment of islets.
In this study, we first examined in vitro a polyvinyl alcohol membrane to be used to contain hybrid islet cells, and second we tested a bioartificial pancreas with entrapment of pancreatic islets in polyvinyl alcohol membrane in rats with experimentally induced diabetes. The permeability of the polyvinyl alcohol membrane to different substances was studied in a two-cell chamber system. Glucose, insulin, and nutrients passed through the membrane easily, whereas the passage of immunoglobulin G was completely prevented, indicating that this membrane could be effective in protecting the bioartificial pancreas from immunorejection. Approximately 2,000 islets collected from three Sprague-Dawley rats were enclosed in a mesh-reinforced polyvinyl alcohol tube and transplanted into the peritoneal cavity of six Wistar rats with streptozotocin-induced diabetes. Their nonfasting serum glucose levels were significantly decreased for at least 12 days. Six diabetic rats receiving intraperitoneal transplantation of free islets without the tube showed a slight but significant decrease in nonfasting serum glucose levels for only 3 days. One diabetic rat with transplantation of the bioartificial pancreas had a significant and sustained decrease in nonfasting glucose levels from pretransplanted levels of 440-500 mg/dl to a mean value of 162 +/- 13 mg/dl for over 3 months without immunosuppression. The bioartificial pancreas was then removed, and glucose levels gradually increased to over 500 mg/dl. The results of the present study suggest that a bioartificial pancreas with entrapment of islets in a polyvinyl alcohol membrane could be a promising therapeutic approach to diabetes mellitus.
Animals↗
Platelet consumption by polyvinyl alcohol coated tubing in canines.
Polyvinyl alcohol (PVA)-coated polyethylene tubing, with or without immobilized heparin, caused severe thrombocytopenia and enhanced the production of new platelets when inserted in a chronic arteriovenous shunt in canines. A similar length of uncoated polyethylene tubing neither lead to thrombocytopenia nor significantly enhanced platelet regeneration, relative to the shunt only without a test section. Platelet regeneration was monitored by the malondialdehyde assay, which was assumed to make a distinction between "new" and "old" platelets. This distinction was combined with the platelet count values to enable calculation of the cumulative consumption curve and the initial fractional consumption rate in the presence of a non constant platelet count. The resulting initial fractional consumption rates were: 34%/day for PVA, 20.5%/day for polyethylene, and 18%/day for the shunt only blank.
Animals↗
Vaginal absorption of polyvinyl alcohol in Fischer 344 rats.
Polyvinyl alcohol (PVA) is a polymer with a wide range of molecular weights and uses. Recently, low molecular weight formulations of PVA have been used as components of contraceptive products designed for intravaginal administration in human females. Previous studies in animals have determined that little or no absorption of PVA occurs from the gastrointestinal (GI) tract. However, there is some concern that PVA of lower molecular weights might be absorbed across membranes of the reproductive tract. Consequently, this work has investigated the absorption of low molecular weight PVA across biological membranes of the reproductive and GI tracts of Fischer 344 rats. Oral administration of ten consecutive daily doses of 14C PVA resulted in little apparent absorption of the dose from the GI tract. In contrast, intravaginal administration of 14C PVA resulted in increasing concentrations of PVA-derived radioactivity in major tissues following one, three or ten daily doses of the estimated human dose of 3 mg/kg. PVA-derived radioactivity was concentrated mainly in the liver, reaching a peak greater than 1750 ng equivalents/g tissue 24 hours following ten daily doses. Over 300 ng equivalents/g tissue were still present in the liver 30 days following the last dose.
Absorption↗
[Papain immobilization on a fibrous polymer of polyvinyl alcohol].
The paper discusses papain immobilization on modified polyvinyl alcohol fibers by the ion fixation technique. The effect of the chemical structure of polyvinyl alcohol fibers on the basic properties of the bound enzyme has been examined. The level of activity and tolerance to pH changes of the resultant immobilized enzymes have been shown to depend on the papain arrangement in the polymer molecule.
Enzymes, Immobilized↗
[Immobilization of invertase in polyvinyl alcohol coatings].
A possibility of invertase immobilization in the polyvinyl alcohol coating formed directly on the electrode surface from water solution of polyvinyl alcohol and boric acid was being investigated. Conditions for obtaining the polymeric coating at the constant potential and at the constant current were compared. In order to obtain the polymeric coatings with a marked enzyme activity optimal conditions were found.
Electrochemistry↗
Preoperative embolization of cerebral arteriovenous malformations with polyvinyl alcohol particles: experience in 51 adults.
In order to determine possible risk factors and to assess the value of platinum microcoils added to polyvinyl alcohol particles in preoperative embolization of cerebral arteriovenous malformations in adults, we reviewed our experience with this procedure. Between September 1985 and June 1989, we performed embolizations in 54 patients with cerebral arteriovenous malformations. Of these, procedures in 51 adults involved the use of polyvinyl alcohol particles, either alone (n = 29) or in combination with platinum microcoils (n = 21). A complication during catheterization precluded embolization in another patient. Beginning as flow-directed embolizations via carotid artery catheterizations (n = 12), newer catheters allowed progression to superselective intracerebral catheterizations (n = 38). Embolization has led to shorter surgical procedures, more clearly defined operative margins, and less bloody operative fields. We have not found recanalization to significantly hinder embolization results with polyvinyl alcohol when resection is undertaken within 1-4 weeks of embolization. Its relative safety and ease of manipulation at surgery argue for its use. We found no significant increase in complications based on patient age, venous drainage of the arteriovenous malformation, or the circulation embolized. Embolization results in cerebral arteriovenous malformations were improved with superselective catheterization and most improved with the combined use of polyvinyl alcohol for nidus embolization followed by occlusion of the feeding vessel with microcoils.
Adolescent↗
Histopathologic analysis of intraarterial polyvinyl alcohol microemboli in rat cerebral cortex.
Polyvinyl alcohol (PVA) foam particles have been used with success in both experimental and clinical embolization of vascular lesions. Cellular response to PVA has been well documented outside, but not within, the central nervous system. This study was directed specifically at the cellular response to PVA in rat brain vasculature. By using small numbers of microparticles, an effort was made to define the response to PVA alone, rather than associated occlusions or infarctions. It was determined that PVA elicited no significant inflammatory response in the embolized vessels nor in the surrounding tissue. The isolated fragments did not appear to alter the blood-brain barrier. The PVA microemboli were extremely adherent to vascular endothelium, lodging in vessels of larger diameter and in relatively high-flow locations without actually wedging within the vessel lumen. On the basis of this analysis, it was determined that PVA foam has properties suitable for an intracerebral vascular embolic agent.
Animals↗
Effects of heat treatment on the permeability of polyvinyl alcohol films to a hydrophilic solute.
Polyvinyl alcohol (PVA) films may be useful as release-controlling membrane systems. Untreated, they are readily permeable to water and hydrophilic drugs. Because heating has been used to increase crystallinity and thus reduce the solubility and swelling in water of PVA films, we have studied the effects of heat on the permeability of PVA films to a water-soluble drug marker. Heat treatment was varied in the temperature range 100-200 degrees C for 1 h. The effect of time of heating was studied at 100 degrees C for 0.5-160 h. After pre-equilibration with water (heat-treated membranes remained intact, untreated ones dissolved), membrane permeabilities to methylene blue in aqueous solution (37 degrees C) were determined in a rotating diffusion cell. Permeabilities decreased with increased heating times (0.98-0.039 cm X min-1 for 0.5-160 h at 100 degrees C, respectively). Heating in air or N2 produced similar results. Further dramatic decreases in permeability occurred with increasing pretreatment temperatures; membrane permeability fell by a factor of approximately 500 with increasing temperature in the range 100-200 degrees C. There was no evidence of decomposition at temperatures less than or equal to 190 degrees C for 1 h. Results were consistent with literature reports of heat-induced increases in crystallinity. Membranes were simple to prepare and permeability could be controlled without recourse to chemical manipulation.
Diffusion↗
Ocular evaluation of polyvinyl alcohol vehicle in rabbits.
The flow properties and viscosity of the vehicle into which drugs are incorporated can be determining factors in the bioavailability of topically applied ophthalmic drugs. It is shown, in rabbits, that when polyvinyl alcohol and methylcellulose are compared on a viscosity basis, there is essentially no difference in the two vehicles with regard to their influence on ocular drug bioavailability. Moreover, the rate of drainage loss for polyvinyl alcohol solutions, as determined by the radioactive technetium technique, compares favorably to methylcellulose solutions of similar viscosity. The relationship between viscosity and contact time or drainage loss of a drug is not a direct one, but an optimum viscosity range exists for polyvinyl alcohol solutions. This optimum range of 12-15 cps in rabbits is identical to that found for methylcellulose and differs considerably from the commonly employed viscosity in commercial preparations. Based on the methylcellulose-polyvinyl alcohol comparison, it appears that vehicles exhibiting or approximating Newtonian flow properties show comparable effects as ophthalmic vehicles. Finally, a discussion of non-Newtonian vehicles and their expected behavior in the eye is presented.
Animals↗
Small particle polyvinyl alcohol embolization of cranial lesions with minimal arteriolar-capillary barriers.
Polyvinyl alcohol foam, prepared as small particles measuring 70-150 micron when injected in intracerebral arteries of the rat, adhere to the vascular endothelium, allowing the particles to be captured without necessarily wedging intraluminally. Based on this observation, small particle microembolization was performed in a series of patients who had hypervascular cranial lesions, whose matrices angiographically appeared to have at best minimal arteriolar-capillary barriers. Each case was associated with intracranial dural sinus or cerebral venous drainage. In addition, several lesions had either venous ectasia or venous aneurysms. Symptomatic improvement occurred in all cases without apparent neurologic or pulmonary complications. These examples demonstrate the ability of very small polyvinyl alcohol foam particles to remain within the interstices of vascular lesions that display evidence of only minimal arteriolar-capillary barriers.
Adult↗