496
A .
A .
M O S C O N A
a population response in terms of differential cell properties, and of
conditions and forces applied. Thus, under an optimal set of conditions,
a population of predominantly highly cohesive cells aggregates into a
single mass including practically all the cells; under the same conditions,
a population consisting largely of non-cohesive cells produces numerous
small aggregates, most of the non- or less-adhesive cells remaining free.
As the dispersed cells aggregate, there is (a) a progressive overall decrease in number of particles (cells and aggregates) per culture accompanied by increase in average size of particles; (b) assortment of cells in
the emerging aggregates which may affect their capacity for cell recruitment and merger (for instance, aggregates that acquire a surface of
non-cohesive cells neither incorporate additional cells nor fuse).
The main cellular parameters in aggregation by rotation are: tissue
origin of the cells (Fig. 2 a-d), their functional and developmental
state, and their preparation; composition of the cell population in
testing, i.e. cell number and relative proportions of different cell types.
The environmental factors are: size and shape of flasks (we use 25 ml or
125 ml Erlenmeyer flasks); quantity and composition of culture medium
or of additives to the medium; speed and diameter of rotation (we use
70-120 rev/min and f inch diameter of rotation, available on most
commercial gyratory shakers); temperature. All these factors can be
readily and adequately controlled, therefore under standard conditions
the results are uniformly reproducible. Characteristic and diagnostically
distinct aggregation patterns are obtained; these are definable in terms
of number, size distribution, shape, and internal structure of aggregates
formed in a given time and set of conditions. Aggregation patterns are
highly responsive to changes in experimental parameters, both cellular
and environmental; precision in standardizing the tests is therefore
essential. The sensitivity of aggregation patterns to experimental modifications is extremely useful in bioassay studies, in which standard
patterns provide the base-lines against which the effects of selected
variables on reattachment and aggregation of cells can be compared
(Moscona, 1961a, b, c ; Garber, 1962). Results of such tests can be
determined with considerable precision from counts of aggregates and
cells and from sizes of aggregates. Such data are obtained from photographic records of cultures or by means of electronic particle countersizer (Coulter Counter). It is frequently useful to correlate cell counts at
the beginning and end of an experiment with the size and number of
aggregates that are produced and to employ the values, or indices, so
obtained to compare the results of different experiments. Although the
quantitative analysis of cell aggregation in rotating cultures is still in its
beginning, the expectation seems justified that the system lends itself
well to exact work on various aspects of cell contact.
A .
A .
M O S C O N A
a population response in terms of differential cell properties, and of
conditions and forces applied. Thus, under an optimal set of conditions,
a population of predominantly highly cohesive cells aggregates into a
single mass including practically all the cells; under the same conditions,
a population consisting largely of non-cohesive cells produces numerous
small aggregates, most of the non- or less-adhesive cells remaining free.
As the dispersed cells aggregate, there is (a) a progressive overall decrease in number of particles (cells and aggregates) per culture accompanied by increase in average size of particles; (b) assortment of cells in
the emerging aggregates which may affect their capacity for cell recruitment and merger (for instance, aggregates that acquire a surface of
non-cohesive cells neither incorporate additional cells nor fuse).
The main cellular parameters in aggregation by rotation are: tissue
origin of the cells (Fig. 2 a-d), their functional and developmental
state, and their preparation; composition of the cell population in
testing, i.e. cell number and relative proportions of different cell types.
The environmental factors are: size and shape of flasks (we use 25 ml or
125 ml Erlenmeyer flasks); quantity and composition of culture medium
or of additives to the medium; speed and diameter of rotation (we use
70-120 rev/min and f inch diameter of rotation, available on most
commercial gyratory shakers); temperature. All these factors can be
readily and adequately controlled, therefore under standard conditions
the results are uniformly reproducible. Characteristic and diagnostically
distinct aggregation patterns are obtained; these are definable in terms
of number, size distribution, shape, and internal structure of aggregates
formed in a given time and set of conditions. Aggregation patterns are
highly responsive to changes in experimental parameters, both cellular
and environmental; precision in standardizing the tests is therefore
essential. The sensitivity of aggregation patterns to experimental modifications is extremely useful in bioassay studies, in which standard
patterns provide the base-lines against which the effects of selected
variables on reattachment and aggregation of cells can be compared
(Moscona, 1961a, b, c ; Garber, 1962). Results of such tests can be
determined with considerable precision from counts of aggregates and
cells and from sizes of aggregates. Such data are obtained from photographic records of cultures or by means of electronic particle countersizer (Coulter Counter). It is frequently useful to correlate cell counts at
the beginning and end of an experiment with the size and number of
aggregates that are produced and to employ the values, or indices, so
obtained to compare the results of different experiments. Although the
quantitative analysis of cell aggregation in rotating cultures is still in its
beginning, the expectation seems justified that the system lends itself
well to exact work on various aspects of cell contact.