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  • 1
    ISSN: 1573-0778
    Keywords: apoptosis ; Bcl-2 ; fixed-bed ; hollow fibre ; hybridoma ; perfusion ; protein-free medium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Apoptosis is an active, genetically determined death mechanism which can be induced by a wide range of physiological factors and by mild stress. It is the predominant form of cell death during the production of antibodies from murine hybridoma cell lines. A number of studies have now demonstrated that the suppression of this death pathway, by means of over-expression of survival genes such as bcl-2, results in improved cellular robustness and antibody productivity during batch culture. In the present study, the influence of bcl-2 expression on hybridoma productivity in two high density perfusion bioreactor systems was investigated. In the first system, a fixed-bed reactor, the DNA content in the spent medium was 25% higher in the control (TB/C3-pEF) culture than that found in the bcl-2 transfected (TB/C3-bcl2) cultures at all perfusion rates. This is indicative of a higher level of cell death in the control cell line. The average antibody concentration for the TB/C3-pEF cell line was 14.9 mg L-1 at perfusion rates of 2.6 and 5.2 d-1. However, for the TB/C3-bcl2 cell line it was 33 mg L-1 at dilution rates of 2 and 4 d-1. A substantial increase in antibody concentration was also found in the Integra Tecnomouse hollow fibre reactor. The antibody titre in the TB/C3-bcl2 cassette was nearly 100% higher than that in the TB/C3-pEF cassette during the cultivation period which lasted 6 weeks. Clearly, these results demonstrate the positive impact of bcl-2 over-expression on production of antibody in hybridoma perfusion cultures.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 20 (1999), S. 815-823 
    ISSN: 1572-9567
    Keywords: alkanes ; alkanols ; alkenes ; aromatics ; corresponding states ; cycloalkanes ; esters ; liquids ; viscosity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract It is of considerable importance to be able to predict accurately the viscosity of liquids over a wide range of conditions. In the present work, the ability of the three-parameter generalized corresponding states principle (GCSP) for the prediction of the viscosity of pure liquids is demonstrated. The viscosity of six different classes of pure liquids, viz., alkanes (19 compounds; 207 data points), cycloalkanes (6 compounds; 74 data points), alkenes (9 compounds; 146 data points), aromatics (4 compounds; 123 data points), alkanols (8 compounds; 89 data points), and esters (4 compounds; 28 data points) have been predicted over a wide range of temperatures using the three-parameter (T c, P c, θ) GCSP. Five options for the third parameter (θ) were studied, viz., Pitzer's acentric factor ω, molar mass M, characteristic viscosity η*, critical compressibility factor Z c, and modified acentric factor Ω, in addition to groups ωZ c and ΩZ c being treated as composite third parameters. Pressure effects were neglected. Good agreement between experimental and predicted values of viscosity was obtained, especially with either ω or η* being used as the third parameter. Furthermore, the viscosities of alkanes predicted by the TRAPP method and an empirical, generalized one-parameter model for liquid hydrocarbons provide comparisons with the more accurate GCSP method. The GCSP provides a simple and yet a powerful technique for the correlation and prediction of viscosities of a variety of pure liquids over a wide range of temperatures.
    Type of Medium: Electronic Resource
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