292
CHARLES Ε.
WILDE
differentiation. The obvious inference is that there had been an exchange
of cues into the micro-environment and thence to the neighbour cell,
such that in the face of this activity, one of the two cells was able to
undertake differentiative processes. Such comparable systems, differing
only be one cell, responded in totally different ways, the single isolate
surviving, while one of the double isolate differentiated. As the number
of cells isolated increased (up to fifteen), both rate, degree and numbers
of cells differentiating increased. From this test it was concluded that
there was exchange of a metabolic nature between cells and medium and
it could be inferred that the altered medium was thus made more
suitable for support of cellular differentiation in the isolated small
groups of cells. These cells were disaggregated by the calcium free saline
technique. Niu and Twitty (1953), had previously, in a now classical
paper reported that small explants of ectoderm would differentiate
('be induced') when cultivated in media in which archenteron roof
mesoderm cells had previously been cultivated. In both of these
experiments some exchange of a metabolic nature must be inferred.
In view of these findings attention was drawn to the disaggregation
procedure itself. Moscona and Moscona (1952), Curtis (1957) and
Feldman (1955) had previously called attention to material which is
active in fostering the reaggregation of cells and can be taken off and
from in between cells by the Trypsin-Versene or other disaggregation
techniques. Moscona (1959), has recently presented cogent evidence
that this material, E.C.M. (extra-cellular material) is an agent fostering
the maintenance of developing tissue fabrics in explanted reaggregating
chick embryonic cells.
In the calcium-free saline disaggregation procedure (Holtfreter, 1947),
a material visibly pours off the disaggregating cells. Cells can, by mild
decantation procedures be washed free of this material. The material
can be conserved, its calcium balance restored and returned with
nutrient to the washed cells. By comparing the activities in terms of
differentiation of washed cells as against washed cells with the E.C.M.
restored, some idea of the effect of this material on differentiation can
be obtained. When small numbers of cells are used, quantitative
analysis of discrete numbers of differentiating cells can be obtained.
In dealing with small groups of cells (i.e. from one to fifteen) the washed
cells in no instance underwent differentiation, whereas washed cells with
reconstituted E.C.M. showed a finite percentage of normal differentiation. Where larger numbers of cells were used (up to 100) some
differentiation occurred in both classes of experiments. However,
differentiation in the washed cells with reconstituted E.C.M. was one
hundredfold greater. Indeed, in this class, differentiation was perfectly
normal, while in washed cells differentiation was rare, incomplete and
CHARLES Ε.
WILDE
differentiation. The obvious inference is that there had been an exchange
of cues into the micro-environment and thence to the neighbour cell,
such that in the face of this activity, one of the two cells was able to
undertake differentiative processes. Such comparable systems, differing
only be one cell, responded in totally different ways, the single isolate
surviving, while one of the double isolate differentiated. As the number
of cells isolated increased (up to fifteen), both rate, degree and numbers
of cells differentiating increased. From this test it was concluded that
there was exchange of a metabolic nature between cells and medium and
it could be inferred that the altered medium was thus made more
suitable for support of cellular differentiation in the isolated small
groups of cells. These cells were disaggregated by the calcium free saline
technique. Niu and Twitty (1953), had previously, in a now classical
paper reported that small explants of ectoderm would differentiate
('be induced') when cultivated in media in which archenteron roof
mesoderm cells had previously been cultivated. In both of these
experiments some exchange of a metabolic nature must be inferred.
In view of these findings attention was drawn to the disaggregation
procedure itself. Moscona and Moscona (1952), Curtis (1957) and
Feldman (1955) had previously called attention to material which is
active in fostering the reaggregation of cells and can be taken off and
from in between cells by the Trypsin-Versene or other disaggregation
techniques. Moscona (1959), has recently presented cogent evidence
that this material, E.C.M. (extra-cellular material) is an agent fostering
the maintenance of developing tissue fabrics in explanted reaggregating
chick embryonic cells.
In the calcium-free saline disaggregation procedure (Holtfreter, 1947),
a material visibly pours off the disaggregating cells. Cells can, by mild
decantation procedures be washed free of this material. The material
can be conserved, its calcium balance restored and returned with
nutrient to the washed cells. By comparing the activities in terms of
differentiation of washed cells as against washed cells with the E.C.M.
restored, some idea of the effect of this material on differentiation can
be obtained. When small numbers of cells are used, quantitative
analysis of discrete numbers of differentiating cells can be obtained.
In dealing with small groups of cells (i.e. from one to fifteen) the washed
cells in no instance underwent differentiation, whereas washed cells with
reconstituted E.C.M. showed a finite percentage of normal differentiation. Where larger numbers of cells were used (up to 100) some
differentiation occurred in both classes of experiments. However,
differentiation in the washed cells with reconstituted E.C.M. was one
hundredfold greater. Indeed, in this class, differentiation was perfectly
normal, while in washed cells differentiation was rare, incomplete and