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The estimation of the intracellular fluxes of mammalian cells using only the mass balances of the relevant metabolites is not possible because the set of linear equations defined by these mass balances is underdetermined. Either additional experimental flux data or additional theoretical constraints are required to find one unique flux distribution out of(More)
Protein production of mammalian-cell culture is limited due to accumulation of waste products such as lactate, CO(2), and ammonia. In this study, the intracellular fluxes of hybridoma cells are measured to determine the amount by which various metabolic pathways contribute to the secretion of waste products derived from glucose. Continuously cultured(More)
Hybridoma cells were grown at steady state under both reductiveand oxidative stress and the intracellular fluxes weredetermined by mass-balancing techniques. By decreasing the dissolved oxygen pressure (pO(2)) in the bioreactor, the reduced formof nicotinamide adenine nucleotide (NADH) was enhanced relativeto the oxidized form (NAD(+)). Oxidative stress, as(More)
The effect of added ammonia on the intracellular fluxes in hybridoma cells was investigated by metabolic-flux balancing techniques. It was found that, in ammonia-stressed hybridoma cells, the glutamate-dehydrogenase flux is in the reverse direction compared to control cells. This demonstrates that hybridoma cells are able to prevent the accumulation of(More)
The estimation of intracellular fluxes of mammalian cells using only mass balances of the relevant metabolites is not possible because the set of linear equations defined by these mass balances is underdetermined. In order to quantify fluxes in cyclic pathways the mass balance equations can be complemented with several constraints: (1) the mass balances of(More)
The adaptive immune system recognizes billions of unique antigens using highly variable T-cell receptors. The alphabeta T-cell receptor repertoire includes an estimated 10(6) different rearranged beta chains per individual. This paper describes a novel micro-array based method that monitors the beta chain repertoire with a resolution of a single T-cell(More)
The determination of the respiration quotient (RQ = CER/OUR) has not been used so far as a tool for understanding animal cell metabolism. This is due to problems in measuring the carbon dioxide evolution rate (CER) rather than the oxygen uptake rate (OUR). The determination of the CER is complicated by the use of bicarbonate in the medium. Using liquid and(More)
A perfused cell-culture process was developed to investigate the stability of IRF-1-mediated proliferation control in BHK cells and to evaluate the efficacy of a novel promoter in these cells. The cell density of proliferation-controlled producer cells was effectively regulated for over 7 weeks in a microcarrier-based continuously perfused bioreactor. An(More)
The analysis of metabolic fluxes of large stoichiometric systems is sensitive to measurement errors in metabolic uptake and production rates. It is therefore desirable to independently test the consistency of measurement data, which is possible if at least two elemental balances can be closed. For mammalian-cell culture, closing the C balance has been(More)
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