3. C O N S T R U C T I O N A N D USE OF S Y N T H E T I C M E D I A
123
1959), with no apparent need for a period of adjustment. The mouse
cell may be intermediate in this characteristic. McQuilkin et al. (1957)
found that sublines of N C T C 929 from a full 20 : 40 : 40, embryoextract : serum : BSS medium required a fairly prolonged period of
radical adjustment to a completely synthetic medium. In our hands,
other sublines of N C T C 929, after growth in 10% serum + a defined
medium for a period, could be transferred without incident to a synthetic medium supplemented with peptone. Sublines maintained for
months or years in the peptone medium could be grown in defined
media without passing through a crisis.
Success in carrying primary cultures in synthetic media over into
serial passage has usually been even lower than in biological media.
Just what takes place during this "adaptation" of cells to media is still
a subject for speculation, usually in terms of production of adaptive
enzyme-systems or other mechanisms made familiar by their extensive
study in cultures of micro-organisms. Micro-organisms are, however,
in a general sense, characteristically much more "adaptable" to changes
in the environment than somatic cells, whose normal milieu is subject
to a high degree of homeostatic control. In thinking about what is
taking place when cells from multicellular organisms are exposed to
environments artificially contrived by an investigator, it is permissible
to speculate that at least part of the poorer performance until now
achieved with synthetic media may be due to nutritional or other defects
in the suitability of the environment. The present synthetic media are
not yet perfected enough for all the purposes to which we try to apply
them. There may, however, be some degree of "adaptation", or selection, of cells to growth in vitro, or to growth in defined media, in the
sense of a change in some properties of the cells themselves after
explantation, making them capable of growing in the conditions
which we provide. Those experienced in working with cell lines in
synthetic media are much aware of the parallel adaptation of medium
to cells and cells to medium that takes place in any laboratory where
synthetic media are being developed, and it is commonly recommended
that those who wish to start working with a particular defined medium,
developed for a particular cell line, should acquire from the originator
both the medium and the cells with which it was developed. That
changes in the nutritional requirements of cells in vitro certainly can
occur, is demonstrated by the existence of clones and sublines differing
in their requirements for individual components, e.g. nutritional
variants requiring or dispensing with asparagine (Neuman and McCoy,
1956; McCoy et al., 1959a; McCoy, Maxwell, Irvine and Sartorelli,
1959c); serine (HafF and Swim, 1957a; Eagle, 1960; Eagle and Piez,
1962) or inositol (Chang, 1958; Eagle and Piez, 1962), and clones with
123
1959), with no apparent need for a period of adjustment. The mouse
cell may be intermediate in this characteristic. McQuilkin et al. (1957)
found that sublines of N C T C 929 from a full 20 : 40 : 40, embryoextract : serum : BSS medium required a fairly prolonged period of
radical adjustment to a completely synthetic medium. In our hands,
other sublines of N C T C 929, after growth in 10% serum + a defined
medium for a period, could be transferred without incident to a synthetic medium supplemented with peptone. Sublines maintained for
months or years in the peptone medium could be grown in defined
media without passing through a crisis.
Success in carrying primary cultures in synthetic media over into
serial passage has usually been even lower than in biological media.
Just what takes place during this "adaptation" of cells to media is still
a subject for speculation, usually in terms of production of adaptive
enzyme-systems or other mechanisms made familiar by their extensive
study in cultures of micro-organisms. Micro-organisms are, however,
in a general sense, characteristically much more "adaptable" to changes
in the environment than somatic cells, whose normal milieu is subject
to a high degree of homeostatic control. In thinking about what is
taking place when cells from multicellular organisms are exposed to
environments artificially contrived by an investigator, it is permissible
to speculate that at least part of the poorer performance until now
achieved with synthetic media may be due to nutritional or other defects
in the suitability of the environment. The present synthetic media are
not yet perfected enough for all the purposes to which we try to apply
them. There may, however, be some degree of "adaptation", or selection, of cells to growth in vitro, or to growth in defined media, in the
sense of a change in some properties of the cells themselves after
explantation, making them capable of growing in the conditions
which we provide. Those experienced in working with cell lines in
synthetic media are much aware of the parallel adaptation of medium
to cells and cells to medium that takes place in any laboratory where
synthetic media are being developed, and it is commonly recommended
that those who wish to start working with a particular defined medium,
developed for a particular cell line, should acquire from the originator
both the medium and the cells with which it was developed. That
changes in the nutritional requirements of cells in vitro certainly can
occur, is demonstrated by the existence of clones and sublines differing
in their requirements for individual components, e.g. nutritional
variants requiring or dispensing with asparagine (Neuman and McCoy,
1956; McCoy et al., 1959a; McCoy, Maxwell, Irvine and Sartorelli,
1959c); serine (HafF and Swim, 1957a; Eagle, 1960; Eagle and Piez,
1962) or inositol (Chang, 1958; Eagle and Piez, 1962), and clones with