[Experience with the new Wheat technique for DeBakey type I dissecting aneurysm].
Explore the source record for details and available documents.
Adult↗
Biomedical subjects
S Omi
Publications and source records attributed to S Omi.
[The effect of C1-inactivator (C1-INA) on endotoxin shock].
Explore the source record for details and available documents.
Animals↗
Magnetite (Fe3O4) microcapsules prepared using a glass membrane and solvent removal.
Fine magnetite powders dispersed in polymer solution were encapsulated from an oil-in-water emulsion prepared by an emulsification process employing a porous glass membrane and subsequent evaporation of the solvent. Styrene-based copolymers were dissolved in a magnetic fluid, and then continuously pushed through the pores of glass membrane into the aqueous phase, which had dissolved polyvinyl alcohol (PVA) and sodium dodecyl sulphate (SDS) as a mixed stabilizer. P(styrene-co-acrylic acid) (PS-AA), P(stryrene-co-butyl acrylate) (PS-BA) and styrene-butadiene rubber (SBR) were dissolved in the specially ordered magnetite fluid (25 wt% magnetite dispersed in toluene) separately or as a mixture, and uniform droplets suspending the magnetic particles were obtained. After the evaporation of toluene, PS-AA capsules retained a spherical shape and uniformity, whereas PS-AA/PS-BA capsules revealed a creased surface and broader size distribution. The microcapsules entrapped 30-40 wt% of magnetite, and the encapsulation yield of magnetite was 20-40%. Glass membranes with 9.5, 5.25 and 1.42 microm pore size were employed and 5-40 microm microcapsules were obtained depending on the pore size. When magnetite suspended in chloroform was used, magnetite capsules with broader size distributions were obtained because of the sticking of the droplets to the membrane wall. The advantage of the membrane emulsification which provides uniform sized droplets was lost.
Capsules↗
Uniform titanium dioxide (TiO(2)) microcapsules prepared by glass membrane emulsification with subsequent solvent evaporation.
Anatase-type titanium dioxide (TiO(2)) was encapsulated using an Shirasu porous glass (SPG) membrane emulsification technique and followed by solvent evaporation. The oil phase, consisting of fine#10; powder of anatase TiO(2), Disperbyk-180, the hydrophobic oil phase additive, and polymer wall solution, was pushed through the membrane pores into the aqueous phase of poly(vinyl alcohol) and sodium dodecyl sulfate to form the solid-in-oil-in water, (S/O)/W, emulsion droplets. Three types of styrene-based copolymer poly(styrene-co-acrylic acid) (PS-AA), poly(styrene-co-2-ethyl hexyl acrylate) (PS-2EHA) and poly(styrene-co-dimethyl aminoethylmethacrylate) (PS-DMAEMA) were used as an encapsulating shell. Uniform droplets were successfully obtained by modifying the oil phase using methyl laurate or hexadecanol as the oil phase additive, together with carefully monitoring the emulsification flow rate during the emulsification. The (S/O)/W emulsion was gently stirred in a sealed reactor, and evacuation of solvent started under moderate heating with increasing a vacuum intensity. Those uniform-sized TiO(2) microcapsules revealed fine porous morphologies on their surfaces as a result of a mild phase separation induced from the addition of the oil phase additive. The encapsulation efficiency was influenced by the stability of TiO(2) in the oil phase, the polymer wall employed, and the operational control of the glass membrane emulsification process. The membrane emulsification process could prepare the TiO(2) microcapsules with about approximately 6-8.5 wt% of encapsulation loadings. PS-AA and PS-2EHA copolymers provided better encapsulation efficiency compared to PS-DMAEMA. SPG membranes with 1.42, 2.8, 5.25, 7.0, or 9.5 microm were employed and 2-20 microm microcapsules were subsequently obtained.
Capsules↗
Defects in the precore region of hepatitis B virus DNA in a plasma pool from carriers seropositive for antibody against e antigen and with infectivity in chimpanzees.
A plasma pool from 12 asymptomatic carriers seropositive for antibody against hepatitis B e antigen (anti-HBe) contained hepatitis B virus (HBV) with chimpanzee infectious doses of 1-100/mL, and another pool from 12 carriers positive for hepatitis B e antigen (HBeAg) contained 10(8)/mL doses or more. The HBeAg-positive pool contained 10(6)-fold more HBV DNA than the anti-HBe-positive pool, reflecting the difference in infectivity in chimpanzees. The precore region sequences of HBV DNA in the two plasma pools were amplified by polymerase chain reaction, and separate HBV DNA clones were propagated for determining the nucleotide sequence. Of 114 clones from the anti-HBe-positive pool, 113 displayed a point mutation from guanine to adenine at nucleotide 83 in the precore region, which converted codon 28 for tryptophan (TGG) to a stop codon (TAG), and the remaining clone had a point mutation from adenine to cytosine at the first letter of codon 1 (CTG) to inhibit the translation initiation of the precore region. Precore region defects, in contrast, were observed in only 10 (8%) of 119 clones from the HBeAg-positive pool. These results indicate the infectious capacity of HBV mutants, defective in the precore region and incapable of directing the synthesis and secretion of HBeAg, which prevail in the circulation of hosts after they seroconvert from HBeAg to anti-HBe.
Amino Acid Sequence↗
A fundamental study of the microencapsulation procedure utilizing coacervation in a polystyrene-cyclohexane solution.
Coacervation in polystyrene (PS)-cyclohexane solution induced by the lowering of temperature was utilized to investigate the fundamental problems involved in the microencapsulation procedure. Polydispersity of PS played a vital role in determining variables at the critical state of phase separation, such as the composition of coacervate (dense) and lean phases. This also depended on temperature. Observations revealed that microcapsules of glass beads consist of a wall with a thin film of PS covered with a thick shell of talc. Poor utilization of PS may limit practical applications of this system unless effective measures are taken for the recovery of unutilized PS. Controlled release behaviour from microcapsules was successfully investigated by using encapsulated anhydrous sodium sulphate (ASS) particles, and applying the Higuchi model to the estimation of the effective diffusion coefficient of ASS through the composite wall. The values of diffusion coefficient decreased from an order of 10(-7) to 10(-8) cm/s by lowering the encapsulation temperature.
Cyclohexanes↗
Application of encapsulated enzyme as a continuous packed-bed reactor.
In the previous report, microencapsulation of lipase employing a (w/o)/w multiple phase emulsion technique, with 2:1 polystyrene (PS)-SBR mixture being used as a wall material, was proposed. Catalysis of the encapsulated enzyme was investigated, and the hydrolysis of triacetin (triglyceride of acetic acid) was successfully simulated by the reaction model based upon the Michaelis-Menten mechanism. Other factors affecting the mechanism such as the mass-transfer resistance of the substrate molecules through the wall and the decrease in pH due to the formation of acetic acid were also taken into consideration. In this report, the particular microcapsules were applied to the continuous tubular reactor system, essentially a packed column reactor, and longevity and mechanical strength of the microcapsules were fully demonstrated. The reaction model derived for a well-stirred batch reactor was also applicable to simulate the behaviour in the packed-column reactor as it was proved that there is no mass transfer resistance between the reactant stream and the surface of microcapsules. The observed data agreed quite well with the calculated values. Similarity of the behaviours of catalysis observed between two reactor systems was thoroughly confirmed. No leakage of the enzyme was detected after repeated usage over the duration of a few months, the temperature being maintained in the range between 293 and 323 K, and pH reset after each operation. Commercial feasibility of the microcapsules for the enzyme catalysis with substrates, small enough to permeate through the wall, was established by these fundamental investigations.
Capsules↗
Immobilization of enzyme by microencapsulation and application of the encapsulated enzyme in the catalysis.
Microencapsulation of lipase (Pseudomonas fluorescens) was carried out using (W/O)/W two-phase emulsion technique. Polystyrene (PS) and Styrene-Butadiene Rubber (SBR) were utilized as wall materials either separately or in mixture. A particular composition of 2:1 PS-SBR yielded homogeneous and tough wall structure, resilient to the impact and tight confinement of enzyme macromolecules. Performance of the encapsulated enzyme was evaluated employing the hydrolysis of triacetin (triglyceride of acetic acid) as a model substrate of the enzyme catalysis. A mathematical model was developed to simulate the behaviour of hydrolysis, which was derived under the assumption that the diffusion of small molecules (substrate and products) through the wall of microcapsules plays a dominant role to the reaction rate. Inhibition of the reaction by the decreasing pH due to the release of acetic acid was also taken into account. The calculated values agreed quite well with the observed data.
Drug Compounding↗
Application of encapsulated enzyme dispersed in a continuous stirred tank reactor.
An application of encapsulated lipase to the hydrolysis of triacetin (triglyceride of acetic acid) was carried out with a continuous stirred tank reactor, in which the encapsulated enzyme was dispersed. An automatic control device to control pH of the reaction mixture at a desired level was designed and installed in the reactor system. Conversion of triacetin at the steady state operation with pH controlled became significantly higher than that without pH control. A particular kinetic model proposed by the authors, which regarded the mass-transfer through the wall of microcapsules as a dominant resistance to the overall reaction rate, was also applicable to simulate the behaviour of CSTR system as in the case of packed-bed reactor.
Drug Compounding↗
Microencapsulation of pheromone-analogue and measurement of the sustained release.
A model study was conducted to establish 2 feasible production and application systems for the long-term, sustained release of pheromone into the atmosphere of targeted areas. The desired goal of effective release was set at least half a year. 2-Ethylhexyl acetate (EHA) was selected as a pheromone analogue due to its similar structure and easier access for quantitative analysis. At first EHA was impregnated in wax particles, which were then encapsulated employing the complex coacervation of a gelatin-gum arabic system. The release period of EHA through the gelatin wall, however, turned out to be too short--only a week at most. As a second attempt, a modification of the two-phase emulsion technique was employed to encapsulate multiple numbers of wax particles in hydrated networks of gelatin. Though the initial release rate of EHA was still too high, 60 per cent of encapsulated EHA underwent sustained release over six months after absorbed moisture had completely evaporated. A two-step mechanism of mass transfer was proposed and the related parameters in terms of the capacity coefficient and effective diffusion coefficient were estimated.
Acetates↗
Preparation of uniform titanium dioxide (TiO2) polystyrene-based composite particles using the glass membrane emulsification process with a subsequent suspension polymerization.
Uniform titanium dioxide (TiO(2))-polystyrene-based composite particles were prepared using the glass membrane emulsification process followed by a subsequent suspension polymerization. The oil phase, consisting of anatase TiO(2) fine powder, monomers, methyl laurate as the hydrophobic additive, Disperbyk-180 and the poly(styrene-co-2-ethyl hexylacrylate) were emulsified through the membrane pores into the aqueous phase containing stabilizers to form a (solid-in-oil)-in-water (S/O/W) emulsion of monomer droplets. The suspension polymerization was carried out at 343 K for 24 h under a nitrogen atmosphere. An SPG membrane with a pore size of 5.25 microm was employed and 20-25 microm TiO(2)-polystyrene based composite particles were obtained depending on the composition of polymerizing oil phase. The effects of the co-monomer, 2-ethylhexyl acrylate and the cross-linking agent, divinyl benzene on the dispersion stability of TiO(2) in the oil phase, the surface feature of the particle and the encapsulation loading were investigated in this study. The membrane emulsification process was capable of preparing the composite particles with approximately 5 wt% of TiO(2) encapsulated, which accounts for with at least 85 wt% of TiO(2) in the oil phase.
Drug Compounding↗
Performance of titanium dioxide microcapsules as a photo-oxidation catalyst for decolourization of methylene blue.
The performance of anatase type titanium dioxide (TiO(2)) encapsulated with styrenic copolymers via the solvent evaporation or suspension polymerization process was investigated as a photocatalyst for the decolourization of methylene blue (MB, 3,4-bis(dimethylamino)-phenothiazine-5-thionium chloride) in the aqueous phase. The TiO(2) microcapsules, loaded with 4-8 wt% TiO(2), were dispersed in a MB aqueous solution containing an adequate amount of hydroperoxide as an oxygen source, and the mixture was exposed to 365 nm UV light. The decolourization of MB proceeded according to the first order of the MB concentration. The apparent rate constant, defined based on the unit weight of loaded TiO(2), depended on the initial concentration of MB. The capsule walls, composed of cross-linked and/or uncross-linked poly(styrene-co-2-ethylhexyl acrylate), favoured the adsorption of MB on the capsule surface and promoted the decomposition. The observations of the cross-section of microcapsules by transmission electron microscopy (TEM) showed similar morphology of microcapsules regardless of preparation method; a thin layer of hydrophilic TiO(2) particles being localized near the particle surface. The sustainability of the microcapsules was also proved by doing experiments successively for 7 days. Smaller size microcapsules were favoured for the decomposition of MB, and the rate constant increased with the surface area of microcapsules in unit volume of the reaction mixture. Although large size microcapsules with uncross-linked polymer wall had a disadvantage of breaking under high shear agitation, those prepared with cross-linked polymer wall by suspension polymerization still remained effective after the sustainability test for 7 days.
Capsules↗