Importance of circadian rhythms in animal cell cultures

Circadian rhythms are a characteristic feature of many cell and organ cultures. Such rhythms may be important in the interpretation of data from cells in culture. More examples of circadian rhythms in tissue culture are badly needed to understand this phenomena. However, they will only be expressed under optimum and well-understood conditions.     

Mini-scale bioprocessing systems for highly parallel animal cell cultures

Animal cells have been used extensively in therapeutic protein production. The growth of animal cells and the expression of therapeutic proteins are highly dependent on the culturing environments. A large number of experimental permutations need to be explored to identify the optimal culturing conditions. Miniaturized bioreactors are well suited for such tasks as they offer high-throughput parallel operation and reduce cost of reagents. They can also be automated and be coupled to downstream analytical units for online measurements of culture products. This review summarizes the current status of miniaturized bioreactors for animal cell cultivation based on the design categories: microtiter plates, flasks, stirred tank reactors, novel designs with active mixing, and microfluidic cell culture devices. We compare cell density and product titer, for batch or fed-batch modes for each system. Monitoring/controlling devices for engineering parameters such as pH, dissolved oxygen, and dissolved carbon dioxide, which could be applied to such systems, are summarized. Finally, mini-scale tools for process performance evaluation for animal cell cultures are discussed: total cell density, cell viability, product titer and quality, substrates, and metabolites profiles.     

High-throughput analysis of animal cell cultures using two-dimensional fluorometry

We report a new method which combines fluorescence spectroscopy at microtiter plate scale with multivariate statistical analysis for rapid and high-throughput analysis of secreted recombinant protein and viable cell growth in animal cell cultures. The potential of the method is demonstrated by application to cultures of three Chinese Hamster Ovary (CHO) cell clones with distinct IgG₄ antibody yields. Supernatant samples collected throughout culture time were analysed by two-dimensional fluorometry; significant changes were observed in the regions of tryptophan, metabolic cofactors and vitamins. Partial least squares regression was then used to correlate the entire fluorescence map with measured concentrations of antibody and viable cells. For both target variables, a model was calibrated with representative data from the two less productive clones and validated with data from the best producer clone; this allowed viable cell density to be predicted for the validation clone with an average error of 10%; even better, the secreted antibody could be predicted with an average error of 7%, proving the predictive capacity of the model beyond the calibration region. All the main spectral regions were required to establish the best correlations for both targeted variables. In conclusion, this method effectively analyzes cellular productivity in 96-well plate format, shortening the time spent in early phases of bioprocess development.     

Phosphate compounds as iron chelators in animal cell cultures

Summary We have studied the capacity of a number of phosphate compounds to act in the double role as a phosphate source and a detoxifier of ferric chloride hydroxo compounds, i.e. as Fe(III) chelators. The tested compounds were: orthophosphate, trimetaphosphate, α-glycerophosphate, β-glycerophosphate, phytic acid, and phosphorylcholine; the test organism the ciliate protozoonTetrahymena thermophila, an animal cell; and the nutrient medium was synthetic, consisting solely of low-molecular-weight compounds. We assessed growth rates of cells in two experimental series. First, phosphate-starved cells were exposed to the tested phosphate compound as the only phosphate source and the ferric chloride concentrations were varied stepwise from 0 to 1000μM. Second, we offered the cells orthophosphate as a phosphate source and selected phosphate compounds as chelators. The cell growth results allow the following conclusions: orthophosphate, trimetaphosphate, α-glycerophosphate, and β-glycerophosphate are excellent phosphate sources; trimetaphosphate, α-glycerophosphate, β-glycerophosphate, and phytic acid are excellent Fe(III) chelators; of the tested compounds trimetaphosphate, α-glycerophosphate, and β-glycerophosphate are excellent in the double role as a phosphate source and a ferric chloride hydroxo detoxifier, i.e. as a Fe(III) chelator.     

Hydrodynamic effects on animal cells grown in microcarrier cultures

Hydrodynamic phenomena in microcarrier cultures are investigated with regard to the development of improved reactor designs for large-scale operations. New concepts and theoretical models that describe new data as well as previously published data are presented.     

The Icelandic genome debate

Three of the central issues in contemporary debates about the commodification of the human body are those of property, ownership, and access. This article uses the case of the central medical database on Icelanders to discuss contesting claims about the ownership of the human genome, with respect to the rapid development of biotechnology, human genome projects and DNA collections. We emphasize the contrast between commercial and communitarian perspectives and to illustrate our argument we explore debates about the Icelandic database. These debates have been intense, focusing on a range of issues, including ethics, academic freedom, public health and, last but not least, the control and ownership of medical records, genetic information and genealogical data. This article should be seen primarily as an anthropological commentary on ongoing developments.     

Elimination of mycoplasma contaminants from cell cultures with animal serum

Repeated treatment with guinea pig or rabbit serum, but not with human serum, was found to eliminate mycoplasma contaminants from mammalian cell cultures as judged by staining with the fluorescent dye Hoechst 33258. Following treatment with rabbit serum and several passages, M. hyorhinis could not be detected by staining, isolation on agar, or specific immunofluorescence in a human prostate carcinoma cell line heavily contaminated with this organism. There was no evidence for the involvement of antimycoplasma antibodies in the bactericidal activity of rabbit serum. Mycoplasmacidal activity of rabbit serum was associated with a heat-labile component(s) which could be inactivated by incubation of the serum with goat antirabbit complement component C3.