A common problem observed in large-scale cell cultivation is reduced culture performance compared with small-scale processes due to the existence of concentration gradients caused by poor mixing. Small-scale simulations using microbial cell suspensions have shown that circulation of cells through concentration gradients of oxygen, pH and glucose can result in reduction of cell growth and product formation similar to the effects observed in large-scale bioreactors. This study was aimed at using scale-down studies to investigate poor mixing in large-scale bioreactors used for suspended plant and animal cell culture. Two plant cell suspensions and a hybridoma cell line were used in this work. The range of oxygen transfer coefficients achieved in the hybridoma and plant suspensions were about 50???20 h-1 and 12???6 h-1, respectively. One-vessel simulation was developed to induce fluctuations of dissolved oxygen tension in a 2-L bioreactor using intermittent sparging of air and nitrogen. The effect of dissolved oxygen fluctuations on the cells was examined by comparing the performance of the cultures with those operated at constant dissolved oxygen tension. In the hybridoma suspension culture, only slight effects on cell growth were observed at circulation times above 300 s. No effect on the specific glucose uptake rate or antibody production was observed at the circulation times tested. Analysis of gene expression for selected hypoxia-related genes also suggested that the overall effect was limited. In plant cell suspensions, the specific growth rates and biomass yields on total sugar in the cultures under fluctuating dissolved oxygen tension were essentially the same as those at constant dissolved oxygen tension for both transgenic Nicotiana tabacum and Thalictrum minus. Under fluctuating dissolved oxygen tension, no effect on antibody accumulation was observed in transgenic N. tabacum suspensions, but a decrease in berberine accumulation was observed in T. minus. From the results, it can be concluded that only minimal effects due to the development of concentration gradients would be expected in large-scale bioreactors used for the cultivation of the hybridoma and plant cell suspensions tested in this work.

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A common problem observed in large-scale cell cultivation is reduced culture performance compared with small-scale processes due to the existence of concentration gradients caused by poor mixing. Small-scale simulations using microbial cell suspensions have shown that circulation of cells through concentration gradients of oxygen, pH and glucose can result in reduction of cell growth and product formation similar to the effects observed in large-scale bioreactors. This study was aimed at using scale-down studies to investigate poor mixing in large-scale bioreactors used for suspended plant and animal cell culture. Two plant cell suspensions and a hybridoma cell line were used in this work. The range of oxygen transfer coefficients achieved in the hybridoma and plant suspensions were about 50???20 h-1 and 12???6 h-1, respectively. One-vessel simulation was developed to induce fluctuations of dissolved oxygen tension in a 2-L bioreactor using intermittent sparging of air and nitrogen. The effect of dissolved oxygen fluctuations on the cells was examined by comparing the performance of the cultures with those operated at constant dissolved oxygen tension. In the hybridoma suspension culture, only slight effects on cell growth were observed at circulation times above 300 s. No effect on the specific glucose uptake rate or antibody production was observed at the circulation times tested. Analysis of gene expression for selected hypoxia-related genes also suggested that the overall effect was limited. In plant cell suspensions, the specific growth rates and biomass yields on total sugar in the cultures under fluctuating dissolved oxygen tension were essentially the same as those at constant dissolved oxygen tension for both transgenic Nicotiana tabacum and Thalictrum minus. Under fluctuating dissolved oxygen tension, no effect on antibody accumulation was observed in transgenic N. tabacum suspensions, but a decrease in berberine accumulation was observed in T. minus. From the results, it can be concluded that only minimal effects due to the development of concentration gradients would be expected in large-scale bioreactors used for the cultivation of the hybridoma and plant cell suspensions tested in this work.

A common problem observed in large-scale cell cultivation is reduced culture performance compared with small-scale processes due to the existence of concentration gradients caused by poor mixing. Small-scale simulations using microbial cell suspensions have shown that circulation of cells through concentration gradients of oxygen, pH and glucose can result in reduction of cell growth and product formation similar to the effects observed in large-scale bioreactors. This study was aimed at using scale-down studies to investigate poor mixing in large-scale bioreactors used for suspended plant and animal cell culture. Two plant cell suspensions and a hybridoma cell line were used in this work. The range of oxygen transfer coefficients achieved in the hybridoma and plant suspensions were about 50???20 h-1 and 12???6 h-1, respectively. One-vessel simulation was developed to induce fluctuations of dissolved oxygen tension in a 2-L bioreactor using intermittent sparging of air and nitrogen. The effect of dissolved oxygen fluctuations on the cells was examined by comparing the performance of the cultures with those operated at constant dissolved oxygen tension. In the hybridoma suspension culture, only slight effects on cell growth were observed at circulation times above 300 s. No effect on the specific glucose uptake rate or antibody production was observed at the circulation times tested. Analysis of gene expression for selected hypoxia-related genes also suggested that the overall effect was limited. In plant cell suspensions, the specific growth rates and biomass yields on total sugar in the cultures under fluctuating dissolved oxygen tension were essentially the same as those at constant dissolved oxygen tension for both transgenic Nicotiana tabacum and Thalictrum minus. Under fluctuating dissolved oxygen tension, no effect on antibody accumulation was observed in transgenic N. tabacum suspensions, but a decrease in berberine accumulation was observed in T. minus. From the results, it can be concluded that only minimal effects due to the development of concentration gradients would be expected in large-scale bioreactors used for the cultivation of the hybridoma and plant cell suspensions tested in this work.

A common problem observed in large-scale cell cultivation is reduced culture performance compared with small-scale processes due to the existence of concentration gradients caused by poor mixing. Small-scale simulations using microbial cell suspensions have shown that circulation of cells through concentration gradients of oxygen, pH and glucose can result in reduction of cell growth and product formation similar to the effects observed in large-scale bioreactors. This study was aimed at using scale-down studies to investigate poor mixing in large-scale bioreactors used for suspended plant and animal cell culture. Two plant cell suspensions and a hybridoma cell line were used in this work. The range of oxygen transfer coefficients achieved in the hybridoma and plant suspensions were about 50???20 h-1 and 12???6 h-1, respectively. One-vessel simulation was developed to induce fluctuations of dissolved oxygen tension in a 2-L bioreactor using intermittent sparging of air and nitrogen. The effect of dissolved oxygen fluctuations on the cells was examined by comparing the performance of the cultures with those operated at constant dissolved oxygen tension. In the hybridoma suspension culture, only slight effects on cell growth were observed at circulation times above 300 s. No effect on the specific glucose uptake rate or antibody production was observed at the circulation times tested. Analysis of gene expression for selected hypoxia-related genes also suggested that the overall effect was limited. In plant cell suspensions, the specific growth rates and biomass yields on total sugar in the cultures under fluctuating dissolved oxygen tension were essentially the same as those at constant dissolved oxygen tension for both transgenic Nicotiana tabacum and Thalictrum minus. Under fluctuating dissolved oxygen tension, no effect on antibody accumulation was observed in transgenic N. tabacum suspensions, but a decrease in berberine accumulation was observed in T. minus. From the results, it can be concluded that only minimal effects due to the development of concentration gradients would be expected in large-scale bioreactors used for the cultivation of the hybridoma and plant cell suspensions tested in this work.

A common problem observed in large-scale cell cultivation is reduced culture performance compared with small-scale processes due to the existence of concentration gradients caused by poor mixing. Small-scale simulations using microbial cell suspensions have shown that circulation of cells through concentration gradients of oxygen, pH and glucose can result in reduction of cell growth and product formation similar to the effects observed in large-scale bioreactors. This study was aimed at using scale-down studies to investigate poor mixing in large-scale bioreactors used for suspended plant and animal cell culture. Two plant cell suspensions and a hybridoma cell line were used in this work. The range of oxygen transfer coefficients achieved in the hybridoma and plant suspensions were about 50???20 h-1 and 12???6 h-1, respectively. One-vessel simulation was developed to induce fluctuations of dissolved oxygen tension in a 2-L bioreactor using intermittent sparging of air and nitrogen. The effect of dissolved oxygen fluctuations on the cells was examined by comparing the performance of the cultures with those operated at constant dissolved oxygen tension. In the hybridoma suspension culture, only slight effects on cell growth were observed at circulation times above 300 s. No effect on the specific glucose uptake rate or antibody production was observed at the circulation times tested. Analysis of gene expression for selected hypoxia-related genes also suggested that the overall effect was limited. In plant cell suspensions, the specific growth rates and biomass yields on total sugar in the cultures under fluctuating dissolved oxygen tension were essentially the same as those at constant dissolved oxygen tension for both transgenic Nicotiana tabacum and Thalictrum minus. Under fluctuating dissolved oxygen tension, no effect on antibody accumulation was observed in transgenic N. tabacum suspensions, but a decrease in berberine accumulation was observed in T. minus. From the results, it can be concluded that only minimal effects due to the development of concentration gradients would be expected in large-scale bioreactors used for the cultivation of the hybridoma and plant cell suspensions tested in this work.

A common problem observed in large-scale cell cultivation is reduced culture performance compared with small-scale processes due to the existence of concentration gradients caused by poor mixing. Small-scale simulations using microbial cell suspensions have shown that circulation of cells through concentration gradients of oxygen, pH and glucose can result in reduction of cell growth and product formation similar to the effects observed in large-scale bioreactors. This study was aimed at using scale-down studies to investigate poor mixing in large-scale bioreactors used for suspended plant and animal cell culture. Two plant cell suspensions and a hybridoma cell line were used in this work. The range of oxygen transfer coefficients achieved in the hybridoma and plant suspensions were about 50???20 h-1 and 12???6 h-1, respectively. One-vessel simulation was developed to induce fluctuations of dissolved oxygen tension in a 2-L bioreactor using intermittent sparging of air and nitrogen. The effect of dissolved oxygen fluctuations on the cells was examined by comparing the performance of the cultures with those operated at constant dissolved oxygen tension. In the hybridoma suspension culture, only slight effects on cell growth were observed at circulation times above 300 s. No effect on the specific glucose uptake rate or antibody production was observed at the circulation times tested. Analysis of gene expression for selected hypoxia-related genes also suggested that the overall effect was limited. In plant cell suspensions, the specific growth rates and biomass yields on total sugar in the cultures under fluctuating dissolved oxygen tension were essentially the same as those at constant dissolved oxygen tension for both transgenic Nicotiana tabacum and Thalictrum minus. Under fluctuating dissolved oxygen tension, no effect on antibody accumulation was observed in transgenic N. tabacum suspensions, but a decrease in berberine accumulation was observed in T. minus. From the results, it can be concluded that only minimal effects due to the development of concentration gradients would be expected in large-scale bioreactors used for the cultivation of the hybridoma and plant cell suspensions tested in this work.

A common problem observed in large-scale cell cultivation is reduced culture performance compared with small-scale processes due to the existence of concentration gradients caused by poor mixing. Small-scale simulations using microbial cell suspensions have shown that circulation of cells through concentration gradients of oxygen, pH and glucose can result in reduction of cell growth and product formation similar to the effects observed in large-scale bioreactors. This study was aimed at using scale-down studies to investigate poor mixing in large-scale bioreactors used for suspended plant and animal cell culture. Two plant cell suspensions and a hybridoma cell line were used in this work. The range of oxygen transfer coefficients achieved in the hybridoma and plant suspensions were about 50???20 h-1 and 12???6 h-1, respectively. One-vessel simulation was developed to induce fluctuations of dissolved oxygen tension in a 2-L bioreactor using intermittent sparging of air and nitrogen. The effect of dissolved oxygen fluctuations on the cells was examined by comparing the performance of the cultures with those operated at constant dissolved oxygen tension. In the hybridoma suspension culture, only slight effects on cell growth were observed at circulation times above 300 s. No effect on the specific glucose uptake rate or antibody production was observed at the circulation times tested. Analysis of gene expression for selected hypoxia-related genes also suggested that the overall effect was limited. In plant cell suspensions, the specific growth rates and biomass yields on total sugar in the cultures under fluctuating dissolved oxygen tension were essentially the same as those at constant dissolved oxygen tension for both transgenic Nicotiana tabacum and Thalictrum minus. Under fluctuating dissolved oxygen tension, no effect on antibody accumulation was observed in transgenic N. tabacum suspensions, but a decrease in berberine accumulation was observed in T. minus. From the results, it can be concluded that only minimal effects due to the development of concentration gradients would be expected in large-scale bioreactors used for the cultivation of the hybridoma and plant cell suspensions tested in this work.

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Chemical and Biochemical Engineering." Includes bibliographical references (p. 113-118).

Tumor cells interact with basement membrane collagen at the site of extravasation through distinct cellular receptors, including the α2β1 and α3β1integrins. These receptors are known to be differentially expressed in metastatic tumors, relative to the normal cells, depending on tumor type and stage of progression. The binding sites within type IV collagen for the α2β1 andα3β1 integrins have been identified. Since both of the integinspecific sequences possess at least one glycosylated Hyl residue, we questioned whether glycosylation could modulate integrin binding. Triple-helical peptides with and without Lys substituted by glycosylated Hyl for Lys543 and Lys540 from the human a1(IV)531-543 gene sequence (α3β integrin-specific) and Lys393 from the human a1(IV)382-393 gene sequence (α2β1 integrin-specific) were synthesized and utilized in the present study. / Cellular response to these triple helical ligands was tested with a primary melanoma cell line, WM-115, and three highly metastatic melanoma cell lines , WM-266-4, M14#5, and SK-MEL-2. Cell adhesion and cell spreading assays yielded differing results depending on whether the ligands contained glycosylated Hyl residues or not. In general, a decrease in cellular affinity toward the ligands was observed when glycosylated Hyl was present. Differences in the levels of adhesion and spreading between cell lines representing different stages of melanoma were also observed. Neutral B-galactosidase activity was detected in all four cell lines. Enzymatic activity levels were comparable for the three metastatic cell lines, whereas distinctively higher activity was detected for cells originating from a primary lesion. This acitivity can signal the potential of tumor cells to enhance and recover their invasive abilities. / The ability of each cell line to remove the galactose from the peptide ligands has been investigated, to test whether tumor cells can reestablish binding relationships between the α2β1 and α3β1 integrins and type IV collagen that are reduced by glycosylation. / by Beatrix Aukszi. / Thesis (Ph.D.)--Florida Atlantic University, 2008. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2008. Mode of access: World Wide Web.