PubMed Health⌕ Search

Biomedical subjects

Paul Lane

Publications and source records attributed to Paul Lane.

5 recordsLinked to original sources
PubMed2002

Determination of dissolved CO(2) concentration and CO(2) production rate of mammalian cell suspension culture based on off-gas measurement.

The determination of dissolved CO(2) and HCO(3)(-) concentrations as well as the carbon dioxide production rate in mammalian cell suspension culture is attracting more and more attention since the effects on major cell properties, such as cell growth rate, product quality/production rate, intracellular pH and apoptosis, have been revealed. But the determination of these parameters by gas analysis is complicated by the solution/dissolution of carbon dioxide in the culture medium. This means that the carbon dioxide transfer rate (CTR; which can easily be calculated from off-gas measurement) is not necessarily equal to carbon dioxide production rate (CPR). In this paper, a mathematical method to utilize off-gas measurement and culture pH for cell suspension culture is presented. The method takes pH changes, buffer and medium characteristics that effect CO(2) mass transfer into account. These calculations, based on a profound set of equations, allow the determination of the respiratory activity of the cells, as well as the determination of dissolved CO(2), HCO(3)(-) and total dissolved carbonate. The method is illustrated by application to experimental data. The calculated dissolved CO(2) concentrations are compared with measurements from an electrochemical CO(2) probe.

Animals↗
PubMed2002

Disabling a C-terminal autoinhibitory control element in endothelial nitric-oxide synthase by phosphorylation provides a molecular explanation for activation of vascular NO synthesis by diverse physiological stimuli.

Calmodulin-dependent activation of endothelial nitric-oxide synthase is generally considered to follow a transient increase in intracellular calcium levels. However, a number of physiological stimuli (e.g. endothelial shear-stress, insulin) are known to activate endothelial nitric oxide (eNOS) via a non-classical, "calcium-independent" pathway. Recent findings demonstrate that such stimuli elicit the phosphorylation of a C-terminal residue in eNOS (Ser(1179) in the bovine isoform), rendering eNOS active at resting levels of intracellular calcium. However, the mechanistic basis for this mode of eNOS activation remains unknown. Protein modeling led us to consider that the C terminus of eNOS may fulfill an autoinhibitory function that can be disrupted by phosphorylation of serine 1179. To test this possibility we contrasted the phenotype of wild type bovine eNOS with that of a mutant lacking C-terminal residues 1179-1205 (CDelta27 eNOS). Despite no observed difference in calmodulin affinity, CDelta27 eNOS exhibited a 5-fold reduction in EC(50) for calcium and a 2-4-fold increase in maximal catalytic activities. In these phenotypic properties, CDelta27 accurately mimics phospho-Ser(1179) wild type eNOS. We conclude that the C terminus imposes a significant barrier to the activation of eNOS by calmodulin binding and that this barrier can be functionally disabled by Ser(1179) phosphorylation-elicited enzyme activation.

Amino Acid Sequence↗
PubMedDate not supplied

Adaptive, model-based control by the Open-Loop-Feedback-Optimal (OLFO) controller for the effective fed-batch cultivation of hybridoma cells.

Although fed-batch suspension culture of animal cells continues to be of industrial importance for the large scale production of pharmaceutical products, existing control concepts are still insufficient. Changes in cell metabolism during cultivation and between similar cultivations, the complexity of the cell metabolism, and the lack of on-line state variables restrict the transfer of available control strategies established in bioprocess engineering. A process control strategy designed to achieve optimized process control must account for all these difficulties and fit sophisticated requirements toward adaptability and flexibility. The combination of a fed-batch process and an Open-Loop-Feedback-Optimal (OLFO) control provides a new approach for cell culture process control that couples an efficient cultivation concept to a capable process control strategy. The application of an adaptive, model-based OLFO controller to a hybridoma cultivation and experimental results are presented.

Algorithms↗