120
C H A R I T Y W A Y M O U T H
filters may decrease its electrical resistance by a factor of 10 (Waymouth,
unpublished) and that the ions so picked up may contribute significantly
to "chemically defined" media prepared from it. Alterations in
complete media upon storage must be taken into account, especially
when using synthetic media of unknown shelf-life from commercial
sources. Much has been made of the instability of glutamine solutions,
which, it is usually recommended, should be stored frozen, or made
up immediately before use. Glutamine certainly does decompose,
though the deterioration in complete media may be less than has been
generally supposed (Tritsch and Moore, 1962), and other components
(e.g. ascorbic acid, vitamin B 1 2 ) may be liable to decay at comparable
rates. Swim and Parker (1958a) attempted to overcome the problem of
instability by compounding all the ingredients (except cystine) of
medium S 103 in dry form, to be dissolved just before use.
There is, as has been pointed out before (Waymouth, 1954a), some
convenience in classifying media according to their ability to permit
(1) survival and a reasonable degree of metabolic integrity; (2) proliferation; or (3) differentiation and function. These designations, arrived
at a posteriori, should not be too rigidly used, and should only be applied
to any medium in the context of particular cells, tissues or organs. The
early synthetic media were, for the most part, "survival" or "maintenance" media, mainly because they were not qualitatively complete or
quantitatively well enough balanced to permit more than a deferment
of cell death. The time factor is important here. Even the simplest
physiological salt solutions can be regarded as "survival" media for
short periods of time; it is for this purpose that they were devised.
Prolonged survival, with some turnover of cells, requires a nutritionally
more complete medium, but the point at which the distinction is made
is arbitrary and empirical, though time certainly enters into its determination. The best "survival" media may permit the cells to live for
months or even years, though a generally acceptable definition might
place the lower limit at a few days. For organ culture, survival for days
rather than hours constitutes a satisfactory criterion of success.
T o convert a "survival" medium, however defined, into one capable
of supporting unlimited proliferation may be a matter of correcting
complete or partial deficiencies of certain components, or of reducing
some ingredients from inhibitory levels. It is in any case largely a
matter of trial and error, and of informed or inspired guesswork based
upon the whole and ever-growing corpus of our general knowledge of
biochemistry. In a similar way, survival or growth media may be made
suitable for differentiation or function by reducing their growth potential, or by supplying compounds (e.g. hormones) known or believed to
act in vivo upon the target organ in question.
C H A R I T Y W A Y M O U T H
filters may decrease its electrical resistance by a factor of 10 (Waymouth,
unpublished) and that the ions so picked up may contribute significantly
to "chemically defined" media prepared from it. Alterations in
complete media upon storage must be taken into account, especially
when using synthetic media of unknown shelf-life from commercial
sources. Much has been made of the instability of glutamine solutions,
which, it is usually recommended, should be stored frozen, or made
up immediately before use. Glutamine certainly does decompose,
though the deterioration in complete media may be less than has been
generally supposed (Tritsch and Moore, 1962), and other components
(e.g. ascorbic acid, vitamin B 1 2 ) may be liable to decay at comparable
rates. Swim and Parker (1958a) attempted to overcome the problem of
instability by compounding all the ingredients (except cystine) of
medium S 103 in dry form, to be dissolved just before use.
There is, as has been pointed out before (Waymouth, 1954a), some
convenience in classifying media according to their ability to permit
(1) survival and a reasonable degree of metabolic integrity; (2) proliferation; or (3) differentiation and function. These designations, arrived
at a posteriori, should not be too rigidly used, and should only be applied
to any medium in the context of particular cells, tissues or organs. The
early synthetic media were, for the most part, "survival" or "maintenance" media, mainly because they were not qualitatively complete or
quantitatively well enough balanced to permit more than a deferment
of cell death. The time factor is important here. Even the simplest
physiological salt solutions can be regarded as "survival" media for
short periods of time; it is for this purpose that they were devised.
Prolonged survival, with some turnover of cells, requires a nutritionally
more complete medium, but the point at which the distinction is made
is arbitrary and empirical, though time certainly enters into its determination. The best "survival" media may permit the cells to live for
months or even years, though a generally acceptable definition might
place the lower limit at a few days. For organ culture, survival for days
rather than hours constitutes a satisfactory criterion of success.
T o convert a "survival" medium, however defined, into one capable
of supporting unlimited proliferation may be a matter of correcting
complete or partial deficiencies of certain components, or of reducing
some ingredients from inhibitory levels. It is in any case largely a
matter of trial and error, and of informed or inspired guesswork based
upon the whole and ever-growing corpus of our general knowledge of
biochemistry. In a similar way, survival or growth media may be made
suitable for differentiation or function by reducing their growth potential, or by supplying compounds (e.g. hormones) known or believed to
act in vivo upon the target organ in question.