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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1252-1262 
    ISSN: 0006-3592
    Keywords: biomedical reactor ; extracorporeal circuit ; hypercholesteremia New Zealand white rabbits ; immobilized phospholipase A2 ; plasma separator reactor (PSR) ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The purpose of this study was to design a biomedical reactor that reduces plasma cholesterol when incorporated in an in vivo extracorporeal system. Phospholipase A2, immobilized onto Agarose beads and housed inside the bioreactor, modifies plasma low density lipoprotein (LDL) into a form that is rapidly removed from circulation. In a packed bed reactor, the enzymatic conversion of LDL to the modified form (with plasma taken from hypercholesterolemic New Zealand white rabbits) was relatively low, 25% ± 6 for a single pass of plasma through the reactor. An extended bed reactor, a hybrid of fluidized and packed bed reactors, was then developed to increase the conversion. This reactor displays a single pass conversion of 60% ± 5 under optimal flow conditions. An evaluation of the flow rate through the reactor indicates that the system is limited by external mass transfer when employed under in vivo conditions. In addition, this system requires blood separation before the enzyme modification, which complicates the circuit control. Therefore, a new system was designed for in vivo use with rabbits. The resulting design, called the plasma separator reactor (PSR), combines plasma separation and enzymatic conversion in a single chamber. The PSR has three advantages over other studied systems: improved external mass transfer conditions, easy controlability, and simple set-up procedures. Single pass conversion reached 52% ± 12 in suboptimal flow under simulated in vivo conditions. This reactor was also tested in vivo with hypercholesterolemic New Zealand white rabbits. A continuous conversion of up to 80% ± 6 of rabbit plasma phospholipids was observed during 90 min of blood circulation (5 mL/min). The decrease in total plasma cholesterol reached a level of 60% of the initial value and was observed to be a function of the bioreactor enzyme activity. © 1993 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
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  • 2
    ISSN: 0006-3592
    Keywords: hollow fiber ; bioreactor ; immobilized enzymes ; porosity ; phospholipase A2 ; low densitylipoprotein ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Previous studies have shown that the modification of low density lipoprotein (LDL) by the enzyme phospholipase A2(PLA2)results in a reduction of cholesterol levels in the plasma of hypercholesterolemic rabbits, due to accelerated clearance of the modified LDL. In the current study, we established techniques and optimized the ratio of enzyme to support for the immobilization of PLA2 on a polymeric support. Hollow fiber bioreactors made from polytetrafluoroethylene (PTFE) polymers were used to encapsulate immobilized PLA2. This design was adopted to eliminate hemolysis of red blood cells by the enzyme. Characterization of the resulting immobilized enzyme in terms of its activity, Michaelis-Menten kinetic constants, and the variation of its activity with incubation time is presented. The enzyme activity was not significantly altered upon incubation at 37°C in lipoprotein-deficient serum (LPDS), over the course of 2 months. The Michaelis-Menten kinetics constants are KM = 8.9 mM, Vmax = 6434.2 for the free enzyme and KappM = 16.7 mM, Vappmax = 619.7 for the immobilized enzyme. These data suggest that a system based on immobilized PLA2 in conjunction with hollow fiber bioreactors (HFBs) may be a good candidate for lowering LDL levels in plasma. © 1995 John Wiley & Sons, Inc.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 5 (1961), S. 534-538 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A spectrophotofluorometer, suitably modified for use with plastics films, was used to study a series of cellulosic polymer films. The chemical structure of the films was found to be related to the wavelength and intensity of the fluorescence emission spectra. Saturated aliphatic esters and ethers were found to possess strong fluorescence maxima at about 350 mμ. Cellulose nitrate exhibits very weak fluorescence at 310 mμ, and a moderate fluorescence maximum appears at 440 mμ for cellulose derivatives containing double bonds or carboxyl groups. A series of experiments is described in which the modification of chemical structure was followed by measuring changes in fluorescence spectra.
    Additional Material: 6 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 15 (1990), S. 260-270 
    ISSN: 0886-1544
    Keywords: Fc-receptors ; antibodies ; “frustrated” phagocytosis ; leucocytes ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: When phagocytes spread on surfaces coated with ligands such as IgG, they form a tight seal with the substrate. This seal excludes soluble macromolecules in the medium from the interface between the cell and substrate. In contrast, when cells spread on control surfaces that are not coated with ligands, the underside of the cell remains freely accessible to soluble proteins (Wright and Silverstein: Nature 309:359, 1984). We employed reflection-interference microscopy (RIM) to determine where the seal forms during interaction with ligand (IgG) -coated surfaces. Human monocyte-derived macrophages (MO) were plated at 37°C on dinitrophenylated (DNP)-glass coverslips (control substrate), IgM anti-DNP-DNP-coated glass (control substrate), or on IgG anti-DNP-DNP-coated glass (phagocytosis-promoting substrate). Live or fixed cells were examined by RIM. Spreading on control surfaces at 37°C was complete in 25 minutes, whereas spreading on IgG-coated surfaces was maximal within 15 minutes and resulted in cell-substrate contact area 1.6 × that of control cells. Within 1 h at 37°C, 90% of MO that spread on IgG-coated substrates, but not on control substrates, excluded macromolecules from their underside. A minor population of cells (19%) exhibited a uniform iron gray RIM appearance indicating an even, close approach to the substrate. These cells may represent early stages of frustrated phagocytosis. In contrast to cells on control substrates, 70% of cells on IgG-coated substrates developed continuous peripheral dark rings in RIM indicative of close association with the substrate. Essentially all cells with peripheral dark rings in RIM excluded macromolecules from their underside. Enclosed within this ring was an area of greater separation between the cell membrane and the substrate, as indicated by the lighter grey of this region in RIM and by the accessibility of substrate to anti-substrate antibody when breaks in the dark ring occur. Thus, MO can create a closed compartment between plasma membrane and substrate that excludes proteins in the surrounding medium, thereby protecting substances secreted into this space from potentially inhibitory substances in the medium.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 7 (1993), S. 195-212 
    ISSN: 0886-9383
    Keywords: Calibration ; Non-linearity ; Principal components ; Stein estimate ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new regression method for non-linear near-infrared spectroscopic data is proposed. The technique is based on a model which is linear in the principal components and simple functions (squares and products) of them. Added variable plots are used to determine which squares and products to incorporate into the model. The regression coefficients are estimated by a Stein estimate which shrinks towards the estimate determined by the first several principal components and the selected non-linear terms. The technique is not computationally intensive and is appropriate for routine predictions of chemical concentrations. The method is tested on three data sets and in all cases gives more accurate predictions than does linear principal components regression.
    Additional Material: 8 Ill.
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  • 6
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectra of trimethylsilyl (TMS) ethers/methyl esters of phenolic acids containing o-dihydroxybenzene groups have base peaks at [M-119]+ instead of the usual [M-15]+ and [M-31]+ that are characteristic of TMS/methyl esters of monohydroxyphenolic acids. These ions, formed by the loss of 31+88 u from the parent ion, possess a cyclic moiety as proven by substitution of deuterium atoms for hydrogen atoms in the TMS groups of the methyl esters of 3,4,5-trihydroxybenzoic (gallic), 3,4-dihydroxybenzoic (protocatechuic) and β-(3,4-dihydroxyphenyl)propenoic (caffeic) acids. Although these cyclic ions are the base peaks in TMS-derivatized o-dihydroxyphenolic acid esters, similar ions represent intense peaks but not necessarily the base peak in other derivatized compounds such as 1,2-dihydroxybenzene, 1,2-dihydroxy-3-methyl- and 1,2-dihydroxy-4-methyl-benzenes and flavan-3-ols that possess o-dihydroxybenzene groups. Compounds possession m- or p-dihydroxybenzene groups do not form these cyclic ions; therefore, this procedure for derivatization and interpretation of mass spectra is valuable for the identification of compounds containing o-dihydroxybenzene groups in complex mixtures of isomeric compounds.
    Additional Material: 3 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 2809-2819 
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New fluorinated poly(ether sulfone)s were prepared from bisphenols and α,ωbis(4-fluorophenylsulfonyl)perfluoroalkanes. The fluorinated sulfone monomers were synthesized by reaction of 4-fluorobenzenethiol salts with perfluoroalkylene diiodides, followed by oxidation. Sodium carbonate mediated polymerization gave high molecular weight polymers in excellent yield. The polymers are generally soluble in chlorinated hydrocarbons and some dipolar solvents, are amorphous with Tg's in the range of 120-160°C and are stable to 400°C. They form clear, colorless films by solution casting. Cast films have dielectric constants and dissipation factors somewhat below those of typical poly(ether sulfone)s, and show good permeability and selectivity for O2/N2 gas separations.
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  • 8
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have substituted choline chloride, tetramethylammonium chloride, sucrose, or glucose for culture medium sodium chloride. When culture medium sodium is reduced below physiological levels (143 mM) by replacement of graded concentrations of sodium chloride with equivalent concentrations of choline chloride, normal fibroblasts approach proliferative inactivity in the presence of 90 mM Na, while their Rous sarcoma virus (RSV)-infected counterparts proliferate actively; both normal and neoplastic cells die with further sodium reduction. When culture medium NaCl is replaced with tetramethylammonium chloride, however, both normal and RSV-infected fibroblasts alike approach proliferative inactivity in the presence of 110 mM Na and both die off in the presence of 90 mM Na. When culture medium NaCl is replaced with sucrose or glucose yet another set of resuls is obtained: both normal and RSV-infected fibroblasts proliferate at reduced, although significant, rates in the presence of 42 mM Na. It is clear from our experimental results that the effects of reduction of culture medium sodium on cell proliferation differ markedly with the use of different sodium chloride substitutes. Caution must be exercised, therefore, in drawing inferences concerning the role of sodium in mitogenesis from experimental studies based on the tactic of reduction of external sodium.
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  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 42 (1998), S. 617-625 
    ISSN: 0021-9304
    Keywords: liver tumor treatment ; glass microspheres ; Re-186 ; Re-188 ; rhenium radioisotopes ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Rhenium glass microspheres composed of metallic rhenium particles dispersed within a magnesium alumino borate glass matrix were produced by sintering ReO2 powder and glass frit at 1050°C. The in vitro chemical durability of radioactive and nonradioactive microspheres was determined from chemical corrosion tests on microspheres immersed in phosphate-buffered saline (PBS) solution at 37°C. The dosimetric properties of these microspheres also were calculated. The rhenium glass microspheres are chemically durable in body fluids and release 〈 1.2% of radioactive rhenium after being immersed in PBS solution for 32 days at 37°C. Therapeutic radioactive rhenium activities can be obtained in 〈 10 h by neutron activation of these microspheres in a thermal neutron flux of 8 × 1013 cm-2s-1. A 50 mg injection of radioactive rhenium glass microspheres containing 3.7 GBq of 186Re and 8.5 GBq of 188Re could deliver a 100 Gy dose to a cancerous liver while limiting the total body dose from rhenium dissolution in vivo to approximately 1 mGy. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 617-625, 1998.
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