298
J. A . L U C Y
interest is the metabolism of normal cells in vivo, a technique of culture
that does not employ cell strains may be preferable in view of the possibility that changes in metabolism occur before cells are able to
multiply rapidly in culture. Increased attention may be paid in the
future to short-term organ and explant cultures as a result of the
accumulating observations on the metabolic abnormalities of long-term
strains. For example, it has been reported that cell cultures from the
bovine mammary gland, even though they proliferated well and retained structural organization for several months, began to lose the
specialized enzyme activities characteristic of normal secretory mammary tissue at differing rates from 24 h to 10 days after being placed
in culture (Ebner, Hageman and Larson, 1961).
The application and suitability of the various methods of Tissue
Culture have previously been considered in relation to amino-acid and
protein metabolism (Lucy, 1960). In this article, some examples ofthe
kinds of investigations that have been made by Tissue Culture methods
other than the cultivation of serially propagated cells, are discussed
in order to illustrate the potentialities of these methods in the study of
amino acid and protein metabolism in vitro.
I I . N U T R I T I O N A L S T U D I E S
A. E X P E R I M E N T A L P R O C E D U R E S
Investigations to determine the nutritional requirements of tissue
explants or organ cultures meet with the difficulty that the relatively
large bulk of the tissue, as compared with that of cultures of isolated
cells, may contain a considerable store of nutrients which must be
exhausted before deficiency symptoms become apparent. This may
necessitate cultivation over a long period during which deleterious
changes, such as regional autolysis, might also occur. In an attempt
to overcome this difficulty, Morton, Pasieka and Morgan (1956)
developed a "nutritional depletion" technique for explants of chick
heart in which fresh tissue was cultured in Hanks's saline solution for
3-4 days before transfer to a chemically defined medium for nutritional
tests. It is clear that the success of such a procedure depends upon the
saline treatment having no deleterious effect on the tissue; Morton
et al. reported that, provided the depletion was not prolonged beyond
4 days, the cultures subsequently revived and survived for a normal
period in synthetic medium M l 5 0 .
In certain instances, it may be possible to determine nutritional
requirements without undue interference from intracellular stores,
J. A . L U C Y
interest is the metabolism of normal cells in vivo, a technique of culture
that does not employ cell strains may be preferable in view of the possibility that changes in metabolism occur before cells are able to
multiply rapidly in culture. Increased attention may be paid in the
future to short-term organ and explant cultures as a result of the
accumulating observations on the metabolic abnormalities of long-term
strains. For example, it has been reported that cell cultures from the
bovine mammary gland, even though they proliferated well and retained structural organization for several months, began to lose the
specialized enzyme activities characteristic of normal secretory mammary tissue at differing rates from 24 h to 10 days after being placed
in culture (Ebner, Hageman and Larson, 1961).
The application and suitability of the various methods of Tissue
Culture have previously been considered in relation to amino-acid and
protein metabolism (Lucy, 1960). In this article, some examples ofthe
kinds of investigations that have been made by Tissue Culture methods
other than the cultivation of serially propagated cells, are discussed
in order to illustrate the potentialities of these methods in the study of
amino acid and protein metabolism in vitro.
I I . N U T R I T I O N A L S T U D I E S
A. E X P E R I M E N T A L P R O C E D U R E S
Investigations to determine the nutritional requirements of tissue
explants or organ cultures meet with the difficulty that the relatively
large bulk of the tissue, as compared with that of cultures of isolated
cells, may contain a considerable store of nutrients which must be
exhausted before deficiency symptoms become apparent. This may
necessitate cultivation over a long period during which deleterious
changes, such as regional autolysis, might also occur. In an attempt
to overcome this difficulty, Morton, Pasieka and Morgan (1956)
developed a "nutritional depletion" technique for explants of chick
heart in which fresh tissue was cultured in Hanks's saline solution for
3-4 days before transfer to a chemically defined medium for nutritional
tests. It is clear that the success of such a procedure depends upon the
saline treatment having no deleterious effect on the tissue; Morton
et al. reported that, provided the depletion was not prolonged beyond
4 days, the cultures subsequently revived and survived for a normal
period in synthetic medium M l 5 0 .
In certain instances, it may be possible to determine nutritional
requirements without undue interference from intracellular stores,