TISSUE CULTURE NUTRITION

Serum fractionation and the effects of bovine serum fractions on human cells grown in a chemically defined medium

Serum has been fractionated by curtain electrophoresis using carboxymethyl cellulose dissolved in sodium bicarbonate electrolyte. Various fractions were produced from bovine serum and added to replicate cultures of Chang's endoepithelial cells and HeLa cells grown in a chemically defined medium. The effects of each of the various fractions on the appearance of the cultures and on cell multiplication were studied. Three different fractions were obtained and two were subjected to further purification. One fraction associated with albumin promoted survival, attachment, and flattening as well as cell multiplication. A second fraction associated with the alpha globulins promoted survival and multiplication of some cells. A third fraction caused cells to aggregate and form free floating clumps. An adequate chemically defined medium for continuous growth of human cells was used throughout the study. The response of cells to alterations in their environment which simulated some of the effects produced by serum fractions is described.

Metabolism of animal cells infected with mycoplasma

Powelson, Dorothy M. (Stanford Research Institute, Menlo Park, Calif.). Metabolism of animal cells infected with mycoplasma. J. Bacteriol. 82:288-297. 1961.-The effect of pleuropneumonia-like organisms (PPLO) upon the metabolism of tissue cultures was tested by comparing the assimilation and accumulation of the amino acids in the medium during growth and maintenance of monolayers of mouse fibroblasts (L strain) and human bone marrow cells (Mox). This preliminary study indicates that PPLO do alter the amino acid metabolism of animal cells. The observed changes in metabolic patterns shown by the infected fibroblast cultures did not mirror the metabolic patterns of the PPLO in the medium alone. Different strains of animal cells showed different responses to one PPLO strain, and different strains of PPLO caused different responses in one strain of animal cells. The PPLO did not grow in the tissue culture medium (no. 199 plus 2% horse serum and 20 to 40 units of penicillin/ml) nor in spent culture fluids and rapidly died off at 37 C but survived for months at 4 C. The altered metabolism of the infected tissue cultures appeared to reflect a true host-parasite interaction.

Development of improved media and culture conditions for clonal growth of normal diploid cells

Multiplication of normal diploid cells in culture is controlled by a complex set of interacting extracellular variables. The amount of serum protein needed for colony formation by such cells is affected directly by many of the other variables, including the nature of the culture surface, the type of trypsinization procedure used, and the qualitative and quantitative composition of the culture medium. By a sequential process of adjusting all of these variables to optimum values for cellular multiplication with minimal amounts of serum protein, we have been able to obtain clonal growth of normal human and chicken cells with less than 500 microgram per ml dialyzed serum protein. Precise quantitative adjustment of nutrient concentrations is particularly important. The multiplication-promoting functions of serum can be classified operationally as "replaceable" (those that can be replaced by modifying the medium or the culture conditions) and "nonreplaceable" (those that we have not yet been able to replace). Elimination of the requirement for replaceable functions of serum has improved greatly the specificity and sensitivity of the bioassay for the nonreplaceable functions. The nonreplaceable multiplication-promoting activity from fetal bovine serum for human diploid fibroblasts has been separated from fetuin and serum albumin and purified approximately 15-fold.

The differential sensitivity of cultured chick mesodermal cells to actinomycin D

Cells were isolated from the somite mesoderm and from the unsegmented (presomite) mesoderm of early chick embryos and exposed to actinomycin D in single cell culture. Actinomycin D inhibited proliferation in cell cultures derived from the unsegmented mesoderm, although the same concentrations of this antibiotic did not inhibit cultures derived from the somite mesoderm. This differential sensitivity parallels the regionally specific necrosis and degeneration observed in the unsegmented mesoderm of intact chick embryos exposed to actinomycin D. In culture, both cell types exhibited approximately the same permeability to labeled actinomycin D and showed comparable inhibition of RNA, DNA, and protein syntheses in the presence of the antibiotic. However, freshly isolated mesodermal cells from the somite region had a higher content of RNA than did cells from the unsegmented region, and the somite cells maintained a higher rate of macromolecular synthesis in untreated cultures.