Oxygen cell culture

Aeration and agitation are two important operations in animal cell culture. Oxygen has a low solubility in aqueous media, with a saturation concentration of approximately 7 mg Lr1 at 37°C. This implies that the oxygen must be provided continuously to the cultures, to ensure that the dissolved oxygen levels in the culture medium remain at an adequate level. The mass balance for oxygen in the liquid phase can be written as ... 

Fig. 3. Schematic of a fluidized-bed process for mammalian cell culture where D(02) = dissolved oxygen.

Mounting electrodes in a bioreactor is costly, and there is an additional contamination risk for sensitive cell cultures. Some other sensors of prac ticai importance are those for dissolved oxygen and for dissolved carbon dioxide. The analysis of gas exiting from a bioreactor with an infrared unit that detects carbon dioxide or a paramagnetic unit that detects oxygen (after carbon dioxide removal) has been replaced by mass spec trophotometry. Gas chromatographic procedures coupled with a mass spectrophotometer will detect 1 the volatile components. 

In conclusion, the oxidation of carotenoids by molecular oxygen, so-called autoxidation, is a complex phenomenon that is very probably initiated by an external factor (radical, metal, etc.) and for which different mechanisms have been proposed. The autoxidation of a carotenoid is important to take into account when working with this molecule even for short periods of time, for example, in cell cultures or studying antioxidant activity, since it can lower the apparent antioxidant activity of a carotenoid (Vulcain et al. 2005). 

Kundu K, Knight SF, Willett N, Lee S, Taylor WR, Murthy N (2009) Hydrocyanines a class of fluorescent sensors that can image reactive oxygen species in cell culture, tissue, and in vivo. Angew Chem Int Ed 48 299-303... 

Ketchum, R.E.B., Rithner, C.D., Qiu, D. et al. (2003) Taxus metabolomics methyl jasmonate preferentially induces production of taxoids oxygenated at C-13 in Taxus x media cell cultures. Plant Metabolomics, 62, 901-909. 

The mitochondrial dysfunctionality seen in manganese neurotoxicity might be related to the accumulation of reactive oxygen species (Verity, 1999). Mitochondrial Mn superoxide dismutase (MnSOD) is found to be low or absent in tumour cells and may act as a tumour suppressor. It is induced by inflammatory cytokines like TNF, presumably to protect host cells. In a rat model, iron-rich diets were found to decrease MnSOD activity, although a recent study reported that in rat epithelial cell cultures iron supplementation increased MnSOD protein levels and activity, but did not compromise the ability of inflammatory mediators like TNF to further increase the enzyme activity (Kuratko, 1999). 

Diabetes is hypothesized to cause cardiac protein acetylation and the acetylation alters the protein function (Fig. 3b). Hypoxia-inducible factor-1 (HIFl) is a transcription factor found in mammalian cells cultured under reduced oxygen tension that plays an essential role in cellular and systemic homeostatic responses to hypoxia. Diabetes interferes with cellular response to hypoxia. In hyperglycemic conditions HIFl degradation is increased because of enhanced HIFl acetylation by... 

The cell culture was carried out under the following conditions temperature 30 °C pH 7.0 controlled by the addition of 2 m KOH. The fermenter was aerated at 1 vvm via a submerged sparger and the agitation rate was controlled between 600 and 1000 rpm in order to maintain the dissolved oxygen concentration above 20 % air saturation. Foaming was controlled by addition of antifoam (Mazu DF 204, BASF). 

Flavanone 3 -hydroxylase (F3 H ECl.14.13.21 CYP75B) activity was initially identified in microsomal preparations of golden weed (Haplopappus gracilis) [110]. E3 H from irradiated parsley cell cultures was later biochemically analyzed and characterized as a cytochrome P450 having an absolute requirement for NADPH and molecular oxygen as cofactors [111]. The enzyme has been shown to have activity with flavanones, flavones, dihydroflavonols, and flavonols, but does not appear to have activity with anthocyanidins [111]. The first cDNA clone for E3 H was isolated from Petunia [112]. It has been suggested that E3 H may serve as an anchor for the proposed flavonoid multi-enzyme complex on the cytosolic surface of the endoplasmic reticulum [44]. 

For experiments carried out in hypoxia, incubate plates in a humidified hypoxia workstation (H35 Hypoxystation Don Whitley Scientific, Shipley, UK). This allows oxygen (O ) levels to be maintained at 1% (hypoxia) instead of 20-21% (nor-moxia/atmospheric concentration) which is normally used for cell culture. 

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