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Biomedical subjects

K Lambert

Publications and source records attributed to K Lambert.

At least 55 records · Page 3Linked to original sources
PubMed1979

Growth of human diploid cells (strain MRC-5) in defined medium; replacement of serum by a fraction of serum ultrafiltrate.

A calf serum ultrafiltrate fraction permitted growth for at least 3.5 generations, including one subculture, of MRC-5 cells in defined medium in the absence of whole serum. The active material has a molecular weight of 10 000 Daltons or less. This suggests that there may be no requirement for a large macromolecular component of serum. The ultrafiltrate was assayed by maximum cell yield from a serum-limited inoculum in a defined medium containing non-limiting amounts of vitamins, amino acids, glucose, a 68-component supplement, iron and methylcellulose. The levels of vitamins, amino acids and glucose were based on quantitative measurements of uptake and the levels of the other components by minimum amount required for maximum yield in defined medium without ultrafiltrate or serum. With excess ultrafiltrate maximum cell yield was limited by the defined part of the medium, probably the supplement. The cell doubling time in defined medium with ultrafiltrate fractions was 70 h compared with 27 h in the medium with serum. Excess ultrafiltrate did not inhibit growth. The lowered growth rate is attributed to a nutritional deficiency in the supplement.

Blood↗
PubMed1975

The quantitative requirements of human diploid cells (strain MRC-5) for amino acids, vitamins and serum.

The uptakes of all essential amino acids, vitamins (except riboflavin), glucose and serum during growth of human diploid cells (MRC-5) were determined. The amino acid uptakes varied considerably with the conditions of culture. The glucose requirement is several times greater than that for mouse LS or human HeLa cells. These analytical results were used to modify the medium so as to ensure that an excess of all defined medium constituents was present and pH was not limiting during study of the serum requirements. It was then found that maximum cell populations were directly proportional to the serum concentration. Hence the growth was limited by the supply of an unknown growth factor in serum. The serum growth factor was not replaced by a mixture of over 60 vitamins, co-enzymes, hormones and other organic and inorganic compounds considered to be possible growth factors, although this mixture did not lower the growth rate and somewhat (22%) increased the yield from the serum growth factor. The unit of serum growth factor is precisely defined in terms of the amount in a standard batch of calf serum. This standard contains 10 units/ml whereas the other batch of serum used contained only 5 units/ml.

Amino Acids↗
PubMedDate not supplied

The nutrient requirements of MRC-5 human diploid cells.

Nutrients were assayed by their effect on maximum cell yield (maximum cell population less inoculum) of MRC-5 cells previously maintained in Eagle's basal medium with 10% (v/v) serum, trypsinised, centrifuged and washed. When nonlimiting amounts of iron, methylcellulose and a 68-component supplement were included in our defined medium, cell yields obtained were equivalent to those obtained with 2 to 3% whole serum. Growth then became limited by serum growth factors which, when serum was fractionated by the low temperature ethanol procedure, appeared to precipitate with the alpha-globulins, although the distribution of activity varied from batch to batch of serum. Column chromatography (DEAE and concanavalin A-Sepharose) of serum resulted in much (20 to 45%) loss of growth factor activity during exhaustive dialysis or Sephadex G-25 desalting suggesting that the growth factor may be a diffusible molecule bound in serum to a large protein carrier.

Cells, Cultured↗