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  • Biochemistry and Biotechnology  (10)
  • 1990-1994  (10)
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  • 1991  (10)
  • 1970
  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 6 (1991), S. 193-201 
    ISSN: 0884-3996
    Keywords: Bioluminescence ; firefly luciferase ; antibiotics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: ATP production, measured by the luciferin-luciferase assay, is an indicator of bacterial metabolic activity. This enzymatic assay yields rapid results (〈 5 minutes), permitting multiple measurements and establishment of ATP growth curves in order to study the kinetics of antibiotics in bacterial populations. The measurement of free or extracellular ATP, total ATP (extra and intracellular) and the ratio of free to total ATP are additional means of studying the bacteriostatic or bactericidal activity of antibiotics. An increase in free ATP is an indicator of extracellular movement due to alteration of the cell wall. The ratio free ATP/total ATP × 100 ≥ 50%, indicates bacteriallysis. These assays were used to study the effects of 14 antibiotics on two reference strains of Escherichia coli ATCC 25922 and Staphylococcus aureus 25923.
    Additional Material: 4 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 834-842 
    ISSN: 0006-3592
    Keywords: microalgae ; bioreactor ; CO2 ; absorption ; KLa ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: For the characterization of CO2 absorption in aerated microalgal culture systems, a different approach based on KLa(O2) determination and transformation was studied. To confirm the validity of this method, the influence of reactions between CO2 and compounds (OH-, H2O, and NH3) present in the culture medium upon the absorption mechanism was evaluated under different physical and chemical culture conditions. Under these conditions, knowledge of the relative magnitudes of the diffusion and reaction kinetics permitted the evaluation of their relative importance. For the determination of the parameters required for the calculation of the CO2 absorption constant, empirical correlations for KL0 and a were used that had been previously verified with experimental data for O2 absorption. Since, for the conditions studied, the absorption rate was shown to be independent of the chemical reactions taking place in the liquid phase, the KLa for CO2 could be directly related to the KLa for O2 by a simple factor that took into account the difference in aqueous diffusivity of the two gases. Thus, using methods developed for determining O2 absorption in gas-liquid contactors, it is possible to adequately characterize CO2 absorption for laboratory and pilot scale algal production systems.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 65-74 
    ISSN: 0006-3592
    Keywords: Succinoglucan ; Agrobacterium radiobacter ; Structured model ; ATP ; cofactors balances ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Wild-type Agrobacterium radiobacter NCIB 9042 has been cultivated in batch cultures on a synthetic medium which was adapted for growth and succinoglucan production. Experiments were carried out in a 4-L stirred-tank aerated reactor. Glucose, biomass, polysaccharide, protein, and inorganic- and organic-nitrogen concentrations were measured, and oxygen consumption and CO2 production rates were obtained by a gas-balance technique. Nitrogen balance shows that inorganic nitrogen is entirely recovered into proteins. The carbon balance is satisfied with in ±5%. Stoichiometric equations for biomass growth and succinoglucan synthesis were established. The biosyntheticpolymer pathways including ATP and cofactor consumption were investigated. From previous studies, a (P/O) value of 1.66 is selected for oxygen sufficient cultures. The actual ATP requirements of 25.4 mmol ATP/g succinoglucan (38.5 mol ATP/mol succinoglucan), determined by a metabolic analysis, is 2.39 times the stoichiometric value. Experimental results were modeled by a system of differential equations. The exponential growth phase was described by a nitrogen-limited Monod equation. Subsequent succinoglucan synthesis followed a slightly modified Luedeking-Piret relation partitioning internal and external polysaccharide. Experimentally determined coefficients are compared with published results for continuous culture of A. radiobacter NCIB 11883.
    Additional Material: 6 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 781-787 
    ISSN: 0006-3592
    Keywords: hybridoma culture ; monoclonal antibody production ; perfusion culture ; continuous culture ; cell cycle ; tangential filtration ; cell separation ; nuclepore membranes ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In order to elucidate the hybridoma life cycle and the limiting factors in perfusion systems, we performed cultures in a stirred tank bioreactor, coupled to an external tangential flow filtration unit. Cell density and antibody production in perfusion were consistent with previous studies. The average life span of the cells (2.1-2.2 days), antibody, productivity per cell produced (30-38 mg/109 cells) and cell size diameter evolution appeared similar to values observed in batch cultures. These observations highly suggest a similar “grow or die” life cycle. Cell and antibody production, strictly related to the medium perfusion rate, seem to be under the control of the nutrient availability. A hypothesis to explain such a life cycle of hybridoma cells in perfusion systems and a model for viable and dead cell density is proposed.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 224-231 
    ISSN: 0006-3592
    Keywords: modeling ; immobilized ; growth ; Nitrobacter ; sensitivity analysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The modeling of the growth of Nitrobacter agilis cell immobilized in κ-carrageenan is presented. A detailed description is given of the modeling of internal diffusion and growth of cells in the support matrix in addition to external mass transfer resistance. The model predicts the substrate and biomass profiles in the support as well as the macroscopic oxygen consumption rate of the immobilized biocatalyst in time. The model is tested by experiments with continuously operated airlift loop reactors containing cells immobilized in κ-carrageenan. The model describes experimental data very well. It is clearly shown that external mass transfer may not be neglected. Furthermore, a sensitivity analysis of the parameters at their values during the experiments revealed that apart from the radius of the spheres and the substrate bulk concentration, the external mass transfer resistance coefficient is the most sensitive parameter for our case.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 232-240 
    ISSN: 0006-3592
    Keywords: immobilized cell growth ; Nitrobacter ; biomass profile ; model evaluation ; nitrification ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A dynamic model that predicts substrate and biomass concentration profiles across gel beads and from that the overall substrate consumption rate by the gel beads containing growing cells was evaluated with immobilized Nitrobacter agilis cells in an airlift loop reactor with oxygen as the limiting substrate. The model predictions agreed well with the observed oxygen consumption rates at three different liquid phase oxygen concentrations. Image analysis showed that 90% of the immobilized cells after 42 days of cultivation was situated in the outer shells in a film of 140 μm, while the bead radius was about 1 mm. The maximum biomass concentration in the outmost film of 56 μm was 11 kg · m-3 gel.
    Additional Material: 8 Ill.
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  • 7
    ISSN: 0263-6484
    Keywords: Hypertonic stress ; EUE cells ; SDS-PAGE ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A cell line derived from human embryonic epithelium (EUE cells) shows an enhanced expression of a 33 kDa protein when adapted to grow in a hypertonic medium containing 0·246 M NaCl (1·8 × the isotonic concentration). The maximum amount of this protein, followed by SDS-PAGE electrophoresis, was found after 4 days of adaptation; thereafter, the protein band remained fairly constant up to 30 days. When the cells were transferred back to a medium containing 0·137 M NaCl (isotonic medium), the protein pattern reverted to that of control cells. This protein is mainly localized in the cytosol, although a small part is associated with the 150 000 g pellet and needs detergents to be extracted. The molecular weight and the cellular location suggest a possible analogy with the so-called amphitropic proteins, that are known to interact with both the epidermal growth factor receptor and hydrophobic structures, such as the membrane phospholipids and the cytoskeletal components.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Cell Biochemistry and Function 9 (1991), S. 95-98 
    ISSN: 0263-6484
    Keywords: Mitoxantrone ; ferricyanide reductase ; Ehrlich cells ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This study focused on the potent cytotoxic effect that mitoxantrone produces on Ehrlich ascites tumour cells. Host mice treated with mitoxantrone showed a life span three times higher than control non-treated host mice. Mitoxantrone also showed a potent cytotoxic effect on Ehrlich cells incubated in vitro for only a few hours. Studies on the effect of mitoxantrone on a plasma membrane redox system showed that mitoxantrone inhibits this activity, which is apparently related to cell proliferation.
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  • 9
    ISSN: 0173-0835
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: We have previously described an in vitro model for studying human immunodeficiency virus, type 1 (HIV-1) infection in CD4+ T cells [1]. This model employs the WE17/10 cell line, which loses expression of its T cell receptor/CD3 (TCR/CD3) after several months of productive infection. We have used this model to analyze the synthesis and posttranslational modification of viral and cellular proteins after HIV-1 infection and to determine the relationship of these changes to TCR/CD3 expression. Mainly we observe positive changes in protein expression after infection. A phosphoprotein, referred to as WH:1, appears in infected cells that still express their TCR/CD3 complex, and its persistence is linked to the presence of the complex. We examined whether loss of the TCR/CD3 complex could be associated with alterations in the T cell activation pathway as a result of infection. We used T cell activators and inhibitors to determine whether there were common elements between the two events. Quantitative enhancement in one spot, Cs:1, occurred after both Cyclosporin A treatment of uninfected cells and HIV-1 infection of untreated cells. Taken altogether, these data suggest that a correlation exists between negative regulation of late events in the T cell activation pathway and down regulation of the TCR/CD3 complex after HIV-1 infection.
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  • 10
    ISSN: 0173-0835
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: A technique was developed for the detection of antifungal activity of proteins after discontinuous polyacrylamide gel electrophoresis under native conditions. The antifungal activity is detected as growth inhibition zones in a homogeneous fungal lawn, grown in an agar layer spread on top of the polyacrylamide gel. The position of proteins with antifungal activity can be determined on a diffusion blot prepared from the same gel. The technique is illustrated for three antifungal plant proteins, i.e. α-purothionin, Urtica dioica agglutinin, and tobacco chitinase.
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