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 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Sevoflurane, a new inhalational anesthetic agent has been shown to produce degradation products upon interaction with CO2 absorbants. Quantification of these sevoflurane degradation products during low-flow or closed circuit anesthesia in patients has not been well evaluated. The production of sevoflurane degradation products was evaluated using a low-flow anesthetic technique in patients receiving sevoflurane anesthesia in excess of 3 h. Sevoflurane anesthesia was administered to 16 patients using a circle absorption system with O2 flow of 500 ml/min and average N2O flow of 273 ml/min. Preoperative and postoperative hepatic and renal function studies were performed. Gas samples were obtained from the inhalation and exhalation limbs of the anesthetic circuit for degradation product analysis and analyzed by gas chromatography/mass spectrometry for four degradation products. The first eight patients received sevoflurane anesthesia using soda lime, and the following eight patients received anesthesia using baralyme as the CO2 absorbant. CO2 absorbant temperatures were measured during anesthesia. Of the degradation products analyzed, only one compound [fluoromethyl-2, 2-difluoro-1-(trifluoromethyl) vinyl ether], designated compound A, was detectable. Concentrations of compound A increased during the first 4 h of anesthesia with soda lime and baralyme and declined between 4 and 5 h when baralyme was used. Mean maximum inhalation concentration of compound A using baralyme was 20.28 +/- 8.6 ppm (mean +/- SEM) compared to 8.16 +/- 2.67 ppm obtained with soda lime, a difference that did not reach statistical significance. A single patient achieved a maximal concentration of 60.78 ppm during low-flow anesthesia with baralyme. Exhalation concentrations of compound A were less than inhalation concentrations, suggesting patient uptake.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Quantification of the degradation products of sevoflurane in two CO2 absorbants during low-flow anesthesia in surgical patients. 130 89

Oxygen is known to inhibit vinyl polymerization in resins used for restorative dentistry. This research examined the effects of unfilled resin being blown into a thin layer on etched bovine enamel in atmospheres of room air, argon, or a combination of the two. Onto this thin, cured resin surface, filled resin was added and cured under atmospheric conditions similar to those of the initial polymerization of the unfilled resin. Comparison of the effects of the different testing atmospheres was made by measurement of the shear bond strength of the resin/composite disc to the etched bovine enamel. Monomer conversion values of the unfilled resin were calculated from the infrared spectra of the simulated tooth/disc assembly. Blowing unfilled resin with compressed room air prior to curing caused poor monomer conversion values and resulted in low shear bond strength to etched enamel. Both high monomer conversion and shear strength values resulted when specimens were cured under all-argon conditions. A clinically practical method of maintenance of the tooth under a continuous stream of argon while being cured in room air was shown to provide greater monomer conversion than curing under room-air conditions alone. SEM evaluation showed that the inhibited layer present in room-air curing was both physically displaced by and absorbed into the overlying filled composite. Specimens cured in argon showed an intact, uniformly thick layer of bonding resin next to the etched enamel, with no displacement by or absorption into the composite addition. Unfilled resin cured in room air had a significantly greater thickness of polymerization-inhibited material than did resin cured in an argon atmosphere.
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PMID:The effect of oxygen inhibition on an unfilled/filled composite system. 221 9

The polyanionic immunomodulatory polymer, maleic vinyl ether anhydride (MVE-2), enhances antitumor macrophage activity and causes heavy proteinuria. The effects of this compound on renal function and renal morphology were investigated in a rat model. Rats were given daily intravenous infusions of MVE-2, 100 mg/kg, over 2-4 hr on each of three consecutive days. Renal function and morphology in MVE-2-infused rats were examined by standard techniques and compared to control rats given saline. On the average, MVE-2 rats had a significant reduction in inulin clearance to 62% of control values. MVE-2 rats developed heavy proteinuria 1-3 days after the first infusion (mean +/- 1 SEM, 387 +/- 91 mg/24 hr). By light microscopy, the only finding was intratubular protein casts; glomeruli were normal. Immunofluorescence showed no deposition of antibody, complement, or fibrin. Electron microscopy revealed foot process effacement, epithelial cell vacuolization, and subepithelial ring-shaped structures; no immune-complex deposits were present. MVE-2 rats had no increase in the number of glomerular Ia(+) cells. To examine further the mechanism of MVE-2 nephropathy, the ability of MVE-2 to induce proteinuria in animals pretreated with radiation (750 rad), methylprednisolone (MP) or cyclosporine (CyA) was determined. Animals pretreated with radiation or MP had significantly less proteinuria after MVE-2 treatment compared to animals receiving no immunosuppressive therapy, while CyA pretreated rats developed heavy proteinuria. These results are compatible with the hypothesis that MVE-2 induces proteinuria via an effect on steroid- and radiation-sensitive cells, perhaps related to production of circulating factors which alter glomerular permeability.
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PMID:Maleic vinyl ether anhydride nephropathy: altered glomerular permeability due to an immunomodulating agent. 284 98

The effects of the modification of polystyrene (PS), polyethylene (PE), poly(vinyl chloride) (PVC), silicone rubber (SR), and fluorinated ethylene propylene (FEP) copolymer by radio frequency glow discharge in a helium environment were presented in part I. The hydrated polymer surfaces were characterized by XPS, SEM, visual microscopy, and by contact angle measurements. In general, exposure of the polymers to RFGD produced an oxidized hydrophilic surface, yet the roughness of the surface was unaltered by the relatively mild plasma conditions used. In this article, the frictional behavior of oxidized and unoxidized SR, PE, and FEP in distilled water, isotonic saline, and blood plasma environments is examined experimentally. The results are discussed in relation to the properties generally believed to affect frictional phenomena and to the surface properties as determined in part I. Results indicate that RFGD-treated SR generates less friction than untreated SR when dragged across all untreated and treated polymer surfaces, whether the medium is distilled water or an isotonic saline solution. Friction is consistently lower in a blood plasma medium between all surfaces investigated, most probably because of the presence of adsorbed proteins at the polymer interfaces.
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PMID:Surface modification and characterization of some commonly used catheter materials. II. Friction characterization. 682 71

Effects of wet (saline in a vinyl chamber), moist (hydrocolloid dressing), and dry (sterile gauze dressing) environments on wound repair were studied in a porcine partial-thickness wound model. Chambers were exchanged and refilled daily with normal saline containing penicillin G (100 U/ml) and streptomycin (100 micrograms/ml). Hydrocolloid and gauze dressings were kept in place until biopsy of the wound site. Wounds in wet, moist, and dry environments were completely epithelialized on days 6, 7, and 8, respectively. Thickness of the epidermis in wet, moist, and dry wounds was 204 +/- 23, 141 +/- 12, and 129 +/- 18 (mean +/- SEM), respectively. Moist wounds had more subepidermal inflammatory cells than wet wounds. In comparison to dry wounds, the moist or the wet healing environment resulted in less necrosis and faster and better quality of healing in the formation of the newly regenerated epidermis.
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PMID:Dry, moist, and wet skin wound repair. 763 86

The aim was to study the effect of the type of polymer solvent on characteristics of microspheres produced by spray drying. The water-soluble model protein, bovine serum albumin (BSA) was microencapsulated into biodegradable poly(D,L-lactic acid) using the following 10 different polymer solvents: acetaldehyde dimethyl acetal, acetone, dichloromethane, dioxane, ethyl acetate, ethyl vinyl ether, nitromethane, tetrahydrofuran, 1,1,1-trichloroethane, and 1,1,2-trichloroethylene. These solvents having similar toxicity levels differ greatly in their physico-chemical characteristics such as boiling point, vapour pressure, miscibility and interfacial tension with an aqueous phase, and solubility parameter. The effect of these solvents on microsphere morphology was studied by SEM-micrographs. Regular particle morphology was obtained when dichloromethane, ethyl acetate, or nitromethane was used as the polymer solvent, whereas the trichlorinated solvents, tetrahydrofuran, and dioxane produced a substantial number of coalesced particles. The results are interpreted in terms of boiling point, vapour pressure, and polymer-solvent affinity. Further, BSA-loading and -integrity in the microspheres, and burst release were analysed. The theoretical loading of 2.9% was attained with dichloromethane, ethyl acetate and nitromethane, in agreement with observations of particle morphology. HPLC- and SDS-PAGE analysis of the microencapsulated BSA did not show any protein degradation or dimerization, whereas solid-phase ELISA clearly revealed that the in vitro protein antigenicity was substantially reduced (50%), particularly by water miscible solvents. Dichloromethane and ethyl acetate did not show any detrimental effect on protein antigenicity. Finally, burst release could be related again to particle morphology, with dichloromethane and nitromethane giving a burst release of only 5%. In conclusion, dichloromethane, ethyl acetate and nitromethane proved to be the most suitable solvents for the polymer-protein system studied.
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PMID:Quality improvement of spray-dried, protein-loaded D,L-PLA microspheres by appropriate polymer solvent selection. 773 Sep 60

A cationic, high-water-content hydrogel membrane composed of poly(vinyl alcohol) (PVA) and poly(ally-biguanido-co-allylamine) hydrochloride (PAB) with positively charged biguanido groups that resemble arginine residues was developed. The PAB was prepared by reacting poly(allylamine) hydrochloride (PAA) with guanyl-O-methyl isourea. PAB/PVA hydrogel membranes were prepared by repeated freezing and thawing. For comparison, hydrogel membranes composed of PAA and PVA were also prepared. The interaction between these hydrogel membranes and mouse fibroblast (L929) was studied by a cell culture method. The PAB hydrogel blend had a relatively low percentage of initial cell attachment. The cell growth on the PAB hydrogel membranes showed a maximum at 5 mol % PAB content that was as high as commercially available plastic films. However, cells on hydrogel membranes with 50 mol % PAB content and 0 mol % PAB content (only PVA) did not seem to grow; neither did the 5/95 PAA/PVA membranes. Water contact angles of hydrogel membranes did not vary with the PAB content. Morphology of the cell attachment was observed by SEM. On the PAB blend hydrogel surfaces, cells were not spindle-shaped and monolayers, but rather cells aggregated in spherical clusters.
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PMID:Cell growth on poly(vinyl alcohol) hydrogel membranes containing biguanido groups. 800 50

In an attempt to develop blood-contacting tubes that can be applied for short-term uses with a reduced heparin concentration or, ideally, without heparinization, we evaluated the blood compatibility of polymeric materials with a rabbit ex vivo shunt model. The shunt tubes employed were made of silicone, plasticized poly(vinyl chloride) (PVC), and segmented poly(ether urethane) (PU). In addition, two kinds of surface-modified tube were used: poly(vinyl alcohol) (PVA)-coated PVC and poly(dimethylacrylamide) (PDMAA)-grafted PU. The ex vivo shunt results correlated well with protein adsorption and platelet adhesion in vitro. The following order for the extent of platelet deposition was given, irrespective of the blood-contacting duration: PDMAA-grafted PU < PVA-coated PVC < PU < silicone, PVC. It is likely that many platelet aggregates detached from the PVA-coated PVC surface. For PDMAA-grafted PU, no trace of detachment of aggregates could be detected on any of the SEM photographs. The number and morphology of blood cells adhered onto the tube surfaces during ex vivo shunting were dependent on the kind of polymer surfaces, the blood exposure time, and the flow rate of blood.
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PMID:Platelet deposition onto polymeric surfaces during shunting. 836 Feb 3

Oligosaccharides of heparin with high affinity for antithrombin III (ATIII) have been immobilized onto surface-modified NHLBI Primary Reference low density polyethylene (PE). PE was modified by radiofrequency plasma polymerized (< 150 nm thick) films derived from N-vinyl-2-pyrrolidone (PPNVP) or allyl alcohol (PPAA), and coupled by chemical derivatization to either 3-aminopropyltriethoxysilane or amino-terminated poly(ethylene oxide). High affinity heparin oligosaccharides (HA-heparin, anti-factor Xa activity of 592 +/- 120 IU/mg) prepared by partial deaminative cleavage of commercial crude heparin and fractionated by agarose-ATIII affinity chromatography, were immobilized to surface-modified PE by reductive amination. The anticoagulant activity, as determined by a chromogenic assay for the inhibition of factor Xa, was estimated to be 30-70 mIU/cm2, with binding estimated to be 56-119 ng/cm2. The highest activity was obtained for the HA-heparin immobilized to PE modified by PPNVP with a PEO spacer. Visual confirmation of ATIII binding to immobilized HA-heparin was demonstrated by a gold-labeled double antibody method with imaging by SEM.
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PMID:Immobilization of high-affinity heparin oligosaccharides to radiofrequency plasma-modified polyethylene. 840 11

Polymer encapsulation of small silica particles, using dispersion polymerization of styrene in aqueous ethanol medium with poly(N-vinyl pyrrolidone) (PVP) as stabilizer, is described. Silica particles, directly synthesized by the Stober process in an aqueous ethanol medium, are either unreacted (hydrophilic character) or coated with 3-(trimethoxysilyl)propyl methacrylate (MPS) (hydrophobic character), which is grafted at the silica particle surface. When the bare silica particles are used as the seed, there is a strong tendency of the silica beads to cover the surface of the polystyrene particles and obviously encapsulation does not occur. On the contrary, when the silica surface is made hydrophobic by coating, the inorganic particles are entirely contained in the polystyrene particles as evidenced by microscopy techniques (TEM, SEM, AFM). It is shown that some polystyrene chains are then chemically bonded to the silica particles, through the coupling agent MPS, and that only a small amount of bonded polystyrene, compared to the total polystyrene synthesized, is sufficient to obtain encapsulation of the silica particles with the entire amount of polystyrene synthesized during the polymerization. Under our experimental conditions, each polystyrene latex particle contains, on average, 4 to 23 silica beads depending, in particular, on the size of the silica. We believe that it is possible to control the composite particle size and morphology by a convenient choice of the composition of the system. Moreover, this new polymer-encapsulation process could be used to synthesize other organic-inorganic composite particles, using, for example, other monomers or minerals. Copyright 1998 Academic Press. Copyright 1998Academic Press
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PMID:Encapsulation of Inorganic Particles by Dispersion Polymerization in Polar Media 946 71


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