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  • 1
    Electronic Resource
    Electronic Resource
    Polyvinyl Alcohol–Methyl Acrylate Copolymers as a Sustained-Release Oral Delivery System (1989)
    Springer
    Pharmaceutical research 6 (1989), S. 844-847 
    Details
    ISSN: 1573-904X
    Keywords: polyvinyl alcohol–methyl acrylate copolymers ; crystalline ; low crystalline ; phenylpropanolamine ; sustained release ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract 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.HC1) 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%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015900303534
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  • 2
    Electronic Resource
    Electronic Resource
    Hollow Fibers as an Oral Sustained-Release Delivery System (1989)
    Springer
    Pharmaceutical research 6 (1989), S. 49-52 
    Details
    ISSN: 1573-904X
    Keywords: hollow fibers ; segmented polyurethane ; oral delivery system ; sustained release ; phenylpropanolamine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Phenylpropanolamine (PPA) bound to ion-exchange resin was encapsulated in hollow fibers made of segmented polyurethane. This system was examined as an oral sustained-release delivery system. The fibers were spun by the phase inversion process and cut into different aspect ratios (length/diameter). The U.S.P. basket dissolution method was used to evaluate the in vitro drug release kinetics and the effect of the aspect ratio on the release. For in vivo evaluation, selected fibers were orally administered to dogs in gelatin capsules. The fiber delivery system provided a sustained-release profile of plasma PPA and a longer terminal half-life when compared to an oral immediate-release formulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015847618671
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  • 3
    Electronic Resource
    Electronic Resource
    Hollow Fibers as an Oral Sustained-Release Delivery System Using Propranolol Hydrochloride (1989)
    Springer
    Pharmaceutical research 6 (1989), S. 1052-1055 
    Details
    ISSN: 1573-904X
    Keywords: hollow fibers ; downward configuration ; oral delivery system ; sustained release ; propranolol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Fibers were spun by the downward configuration of the wet spinning technique. This configuration is capable of encapsulating nonspherical and/or coarse particles. We examined encapsulation of propranolol hydrochloride and the ability of the fibers to act as a sustained-release delivery system for propranolol hydrochloride as a model drug. The U.S.P. basket dissolution method was used to evaluate the in vitro drug release kinetics and the effect of the aspect ratio (length/diameter) on drug release. For in vivo evaluation, selected fibers were administered to dogs in gelatin capsules. The results of these in vitro and in vivo studies were compared to those obtained with a marketed sustained-release propranolol product (Inderal LA). The fiber delivery system provided a sustained-release profile of plasma propranolol concentrations similar to that observed with Inderal LA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015982521706
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of dissolved oxygen on nitrogen fixation by A. vinelandii. II. Ionically adsorbed cells (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 26 (1984), S. 87-91 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Continuous culture studies of Azotobacter vinelandii cells immobilized by ionic adsorption to Cellex E anion exchange resin were conducted under oxygen-limited conditions for comparison to free-cell cultures. Immobilization had little effect upon the specific respiration and sucrose consumption rates as compared to free cells. However, maxima in specific nitrogen fixation rate and nitrogenase activity as a function of dissolved oxygen occurred at a CO2 value of approximately 0.005 mM as opposed to 0.02 mM for free cells. Further, in contrast to free-cell culture, most of the fixed nitrogen appeared in the medium rather than within intact cells. There were strong indications that reproduction of bound cells often resulted in cell lysis accounting for the fixed nitrogen content in solution.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260260116
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of dissolved oxygen on nitrogen fixation by A. vinelandii. I. Free cell cultures (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 26 (1984), S. 81-86 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: As part of an investigation into the use of biological nitrogen fixation for fertilizer ammonia production, continuous culture studies of respiration and nitrogen fixation in the aerobic bacteria Azotobacter vinelandii under oxygen-limited conditions were conducted. Respiration and growth rates followed Monod forms with respect to dissolved oxygen concentration. However, specific nitrogen fixation rate and nitrogenase activity exhibited maximum values at dissolved oxygen concentrations of ca. 0.02 mM (10% of air saturation). These results suggest careful control of oxygen in the environment is necessary to optimize fixed nitrogen production by this organism.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260260115
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