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A . M O S C O N A , O. A . T R O W E L L A N D E . N . W I L L M E R
but perhaps what is more important is that the number of cells inoculated has to be sufficient to "adapt" the medium, For example, 600
cells from the L-strain of mouse fibroblasts failed to survive in 2 ml of a
medium composed of chick-embryo extract, horse serum and a balanced
salt solution; somewhat over half of the cultures in the same medium
inoculated with 10,000 cells showed growth; while all cultures seeded
with 100,000 cells showed further proliferation (Earle, Bryant and
Schilling, 1954). The composition of the medium is, of course, of
great importance in this sort of investigation, not only for the obvious
reasons of food supply and the like, but also because it determines the
extent to which cells lose necessary constituents to the medium (see
pp.34, 254, 259,278, 285).
This general procedure for the preparation of cultures from cell
suspensions is certainly applicable to many tissues and is adequate for
obtaining cells in the large numbers required for the propagation and
investigation of viruses. For most physiological, biochemical and cytological purposes, however, such cultures must be looked upon with
some suspicion. As has already been pointed out, different types of cells
in the body have distinct surface properties and their own methods of
maintaining position and equilibrium with their environment. Tryptic
digestion may separate cells, but it probably does not liberate all types
of cells equally, so it is not certain which cells have been freed or which
cells finally succeed in growing. Moreover, there is generally some
uncertainty as to how the survivors have been affected by the treatment.
Only in a few instances is it possible to be certain on these points. With
embryonic limb-buds, and pituitary glands Moscona and Moscona
(1952) early showed that the cells were so little damaged that they
could reaggregate and recover sufficiently to re-differentiate very
normally into recognizable limb-rudiments or pituitary gland tissue.
Similarly it is known that certain cells from kidney tissue, liver tissue,
heart and cartilage tissue can all survive the treatment relatively
undamaged, but, except, for example, in the case of cardiac muscle
cells, which may show rhythmic contractions, it is often by no means
certain at an early stage which particular cells of the original organ are
being cultivated. Some other tissues are far less amenable to dissociative
procedures and to isolation, and many types of cell are known to be
altered, if not positively damaged. However, attempts to overcome the
difficulties encountered in separating cells from already differentiated
tissues are likely to give very valuable information both on the nature
of the cell contacts and on the properties of the intercellular substances
characteristic of the different sorts of tissues (see Chapter 14).
In general, it is manifestly desirable to subject the cells of any tissue
under investigation by these methods to the least drastic procedure
A . M O S C O N A , O. A . T R O W E L L A N D E . N . W I L L M E R
but perhaps what is more important is that the number of cells inoculated has to be sufficient to "adapt" the medium, For example, 600
cells from the L-strain of mouse fibroblasts failed to survive in 2 ml of a
medium composed of chick-embryo extract, horse serum and a balanced
salt solution; somewhat over half of the cultures in the same medium
inoculated with 10,000 cells showed growth; while all cultures seeded
with 100,000 cells showed further proliferation (Earle, Bryant and
Schilling, 1954). The composition of the medium is, of course, of
great importance in this sort of investigation, not only for the obvious
reasons of food supply and the like, but also because it determines the
extent to which cells lose necessary constituents to the medium (see
pp.34, 254, 259,278, 285).
This general procedure for the preparation of cultures from cell
suspensions is certainly applicable to many tissues and is adequate for
obtaining cells in the large numbers required for the propagation and
investigation of viruses. For most physiological, biochemical and cytological purposes, however, such cultures must be looked upon with
some suspicion. As has already been pointed out, different types of cells
in the body have distinct surface properties and their own methods of
maintaining position and equilibrium with their environment. Tryptic
digestion may separate cells, but it probably does not liberate all types
of cells equally, so it is not certain which cells have been freed or which
cells finally succeed in growing. Moreover, there is generally some
uncertainty as to how the survivors have been affected by the treatment.
Only in a few instances is it possible to be certain on these points. With
embryonic limb-buds, and pituitary glands Moscona and Moscona
(1952) early showed that the cells were so little damaged that they
could reaggregate and recover sufficiently to re-differentiate very
normally into recognizable limb-rudiments or pituitary gland tissue.
Similarly it is known that certain cells from kidney tissue, liver tissue,
heart and cartilage tissue can all survive the treatment relatively
undamaged, but, except, for example, in the case of cardiac muscle
cells, which may show rhythmic contractions, it is often by no means
certain at an early stage which particular cells of the original organ are
being cultivated. Some other tissues are far less amenable to dissociative
procedures and to isolation, and many types of cell are known to be
altered, if not positively damaged. However, attempts to overcome the
difficulties encountered in separating cells from already differentiated
tissues are likely to give very valuable information both on the nature
of the cell contacts and on the properties of the intercellular substances
characteristic of the different sorts of tissues (see Chapter 14).
In general, it is manifestly desirable to subject the cells of any tissue
under investigation by these methods to the least drastic procedure