The nutrition of animal tissues cultivated in vitro. III. Use of a depletion technique for determining specific nutritional requirements

Frontiers in mammalian cell culture

For the past 60 years, fundamental discoveries in eukaryotic biology using mammalian cell cultures have been significant but modest relative to the enormous potential. Combined with advances in technologies of cell and molecular biology, mammalian cell culture technology is becoming a major, if not essential tool, for fundamental discovery in eukaryotic biology. Reconstruction of the milieu for cells has progressed from simple salt solutions supporting brief survival of tissues outside the body to synthesis of the complete set of structurally defined nutrients, hormones and elements of the extracellular matrix needed to reconstruct complex tissues from cells. The isolation of specific cell types in completely defined environments reveals the true complexity of the mammalian cell and its environment as a dynamic interactive physiological unit. Cell cultures provide the tool for detection and dissection of the mechanism of action of cellular regulators and the genes that determine individual aspects of cell behavior. The technology underpins advances in virology, somatic cell genetics, endocrinology, carcinogenesis, toxicology, pharmacology, hematopoiesis and immunology, and is becoming a major tool in developmental biology, complex tissue physiology and production of unique mammalian cell-derived biologicals in industry.

The role of methionine deficiency in poliovirus replication in tissue cultures

The role of methionine in poliovirus infection in HeLa and monkey kidney cells was investigated by using the methionine analogue l-ethionine. In the presence of 2.0 x 10(-3) and 4.0 x 10(-3) moles ethionine, the growth of HeLa and monkey kidney cells was significantly inhibited. Under the same experimental conditions, ethionine had no significant effect on the biosynthesis of two strains of poliovirus (Mahoney and Lansing) in HeLa cells, whereas in primary monkey kidney cells, it markedly inhibited the biosynthesis of the Lansing strain of poliovirus. HeLa cells partly depleted of their intracellular amino acids did not change the rate of viral biosynthesis. The inhibitory effect of ethionine on cell growth and viral biosynthesis was reversed by addition of an excess of l-methionine.

FURTHER STUDIES ON THE DUAL REQUIREMENT FOR PHENYLALANINE AND TYROSINE IN TISSUE CULTURE

Seventeen structurally related compounds were tested for their ability to substitute for phenylalanine or tyrosine in the nutrition of chick embryo heart fragments. DL-Alanyl-DL-phenylalanine replaced phenylalanine. All other compounds had negligible effects, and most were toxic at high concentrations. β-Phenylserine, a phenylalanine antagonist, actually prolonged the survival of chick heart cells but only if both phenylalanine and tyrosine were present. Similarly, optimal reversal of β-phenylserine toxicity was dependent on the presence of both amino acids. Although phenylalanine and tyrosine are not interconvertible in the present system, it has been shown that three phenylalanine antagonists, p-fluorophenylalanine, β-2-thienylalanine, and β-phenylserine, can be identified by their relationship to tyrosine, rather than to phenylalanine.

AMINO ACID METABOLISM OF NORMAL AND MALIGNANT CELL CULTURES

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CARBOHYDRATE UTILIZATION BY CHICK EMBRYONIC HEART CULTURES

Freshly explanted chick embryonic heart fragments were cultivated in completely synthetic media. Survival of such cultures in the complete medium, containing glucose, was established at approximately 35 to 40 days, while in the absence of carbohydrate the cultures died within 3 to 5 days. Survival was considered to be a more physiological measurement than rapid cell multiplication for normal tissues and was adopted as the criterion for all experiments reported. Fifty-two compounds were tested for their ability to replace glucose, as the sole carbohydrate, in this system. Of these, seven (mannose, fructose, galactose, β-glucose, maltose, glucose-1-phosphate, and glucose-6-phosphate) replaced glucose completely. Five others (sorbitol, alpha-methyl-D-glucoside, turanose, dextrin, and fructose-6-phosphate) were partially active. The remainder were negative. Comparison is made of the present results with those obtained by other workers using malignant cells in the presence of serum–enzymes. The present results suggest that the ability to replace glucose decreases progressively as compounds down the Embden–Meyerhof pathway are tested.

CARBOHYDRATE UTILIZATION BY CHICK EMBRYONIC HEART CULTURES

Freshly explanted chick embryonic heart fragments were cultivated in completely synthetic media. Survival of such cultures in the complete medium, containing glucose, was established at approximately 35 to 40 days, while in the absence of carbohydrate the cultures died within 3 to 5 days. Survival was considered to be a more physiological measurement than rapid cell multiplication for normal tissues and was adopted as the criterion for all experiments reported. Fifty-two compounds were tested for their ability to replace glucose, as the sole carbohydrate, in this system. Of these, seven (mannose, fructose, galactose, β-glucose, maltose, glucose-1-phosphate, and glucose-6-phosphate) replaced glucose completely. Five others (sorbitol, alpha-methyl-D-glucoside, turanose, dextrin, and fructose-6-phosphate) were partially active. The remainder were negative. Comparison is made of the present results with those obtained by other workers using malignant cells in the presence of serum–enzymes. The present results suggest that the ability to replace glucose decreases progressively as compounds down the Embden–Meyerhof pathway are tested.

THE METABOLISM OF ANIMAL TISSUES CULTIVATED IN VITRO: III. AMINO ACID METABOLISM OF STRAIN L CELLS IN COMPLETELY SYNTHETIC MEDIA

Strain L cells, of mouse fibroblastic origin, have been cultivated in vitro in completely synthetic medium M 150 and in various modifications of this medium. The amino acid changes in the nutrient medium during cell cultivation have been studied by paper chromatography. A characteristic pattern of amino acid uptake and accumulation in the medium has been found. No change in the alanine concentration was observed but omission of alanine from the culture medium resulted in its accumulation in appreciable amounts. Omission of glutamic acid did not alter the pattern of amino acid changes by the cells. Omission of glutamine increased the uptake of amino acids and prevented amino acid accumulation. Omission of both glutamic acid and glutamine resulted in a virtual cessation of amino acid changes in the culture medium. Strain L cells decreased the adenine content of the medium and produced small amounts of hypoxanthine. These changes were not affected by alterations in the amino acid content of the medium. Omission of glutamic acid and glutamine from the culture medium did not cause an appreciable decrease in cell population or apparent degeneration of the cultures over a 30-day period.

The nutrition of animal tissues cultivated in vitro. IV. Amino acid requirements of chick embryonic heart fibroblasts

1. The amino acid requirements of freshly explanted chick embryonic heart tissues cultivated in completely synthetic media have been determined, employing a nutritional depletion technique. Arginine, histidine, lysine, tyrosine, tryptophan, phenylalanine, cystine, methionine, threonine, leucine, and valine were found to be essential. Serine, isoleucine, glycine, and glutamine were found to be non-essential. Glutamic acid, aspartic acid, alpha-alanine, proline, and hydroxyproline were found to be inhibitory in this test system. 2. A total amino acid level of approximately 100 mg. per cent was found to be optimal and DL-amino acids were found to be non-toxic, unless used in high concentrations. 3. A comparison has been made of the amino acid requirements of various types of tissue cultures, of the chick, and of man and certain differences in these requirements have been discussed.