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  • Biochemistry and Biotechnology  (6)
  • Endocardial  (1)
  • 1
    ISSN: 1432-2013
    Keywords: Key words Sodium ; Action potential ; Endocardial ; Epicardial
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  In this study we report measurements of the intracellular sodium concentration ([Na+]i) in cardiac myocytes isolated from sub-endocardial and sub-epicardial regions of the rabbit left ventricle. These measurements show that [Na+]i is significantly higher in sub-epicardial than in sub-endocardial myocytes both at rest and during steady-state stimulation at 0.5 Hz. During a 10-min rest the rate of fall of [Na+]i was identical in cells from the two regions but during post-rest recovery [Na+]i rose significantly faster in sub-endocardial cells. The effect that this difference in sodium regulation may have on the rate of recovery of the calcium transient post-rest is discussed. The steady-state differences in [Na+]i do not appear to have the effect on contraction we would expect i.e. steady-state contraction is larger in sub-endocardial cells where [Na+]i is lower. Changes in [Na+]i brought about by altering the frequency of stimulation are associated with the expected changes of contraction. Action potentials were found to be significantly longer in sub-endocardial cells and following rest action potential duration was shortened although regional differences were maintained. No regional differences in this effect of rest or in recovery of the action potential post-rest were found.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 13 (1971), S. 337-352 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The catalytic activity of amyloglucosidase covalently attached to DEAE-cellulose was studied in a packed bed reactor and a continuous feed stirred tank reactor (CSTR) for the reaction maltose → glucose. At low flow rates mass-transfer limitations in the bed reactor lead to lower conversions for this reactor compared to the CSTR. Simple theoretical expressions for these reactors were compared with the experimental results. There are significant differences between the kinetic parameters and pH profile of the immobilized and free enzyme. The immobilized enzyme also showed greater stability at 50°C than did free amyloglucosidase. The temperature dependence of the reaction rate was the same for immobilized and free enzyme.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 14 (1972), S. 473-491 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The limitation of thermal inactivation on catalytic activity in continuous enzymatic reactions is considered. Where an enzyme is retained in a reaction environment which is open to mass transfer of reaction components, the effect of enzyme inactivation on reactant conversion depends on the order of the chemical reaction and the pattern of fluid flow through the reaction volume. Equations expressing conversion as a function of time for first-order inactivation are presented for Michaelis-Menten kinetics and the limiting fluid flow conditions of plug flow and complete back-mixing. Substrate protection or destruction of an enzyme is also considered and it is shown theoretically that the catalytic life of an enzyme may be optimized by the proper choice of fluid flow pattern.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 14 (1972), S. 201-205 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: It is shown theoretically that in continuous reactions the rate of catalase inactivation by hydrogen peroxide depends on the type of reactor and the order of the chemical reaction.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 14 (1972), S. 675-678 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 13 (1971), S. 319-322 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 13 (1971), S. 493-502 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Substrate inhibited enzyme reactions occurring in systems open to mass transfer may display multiple steady-state behavior. For a simple one-substrate case it is shown theoretically that the unstable steady-state region always lies within the conversion range of 50-100%. A criterion for the stability of a steady-state point is given. Numerical solutions of the appropriate transient equation show how the system approaches stable steady state in instances where there are three possible steady-state points. The consequences of the existence of an unstable region on the systems response to changes in its parameters is discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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