188
M. A B E R C R O M B I E
(Abercrombie, 1961b) perhaps more strongly than fibroblasts (Abercrombie, Heaysman and Karthauser, 1957), neurites and Schwann cells
(Weiss, 1934), and kidney epithelium (Weiss and Taylor, 1956) all
show the reaction.
(b) Cells as contact stimuli. The other structures that a cell comes into
contact with are the surfaces of surrounding cells, and these contacts
influence the direction of movement. One instance of this is contact
inhibition, so named by Abercrombie and Heaysman (1954) who
investigated its occurrence in fibroblasts. The phenomenon in fibroblasts will be discussed because more is perhaps known about their
contact inhibition than about that of other cells. The first tissue
culturist to suggest this particular behaviour reaction was, however, Leo
Loeb (1921) who used it to explain the dispersion of Limulus amoebocytes
from a dense focus, though he does not seem to have put the explanation
to experimental test. The hypothesis had still earlier precursors amongst
workers on the healing of wounds in epithelia (see Abercrombie and
Ambrose, 1962).
The behaviour in question can be summed up by saying that, when
contact inhibition is operative, a cell will not use another cell as substrate for its locomotion; and the change in locomotion necessary to
ensure this when cells are moving on a collision course happens only
when contact is made between the cells. When therefore a cell, moving
on a non-cellular substrate, runs into another cell, it will cease to move
in the direction that brought about the collision, except that if both
cells are going the same way a diminution of speed will suffice. A cell
stopped by contact as a rule moves away in a new direction, provided
there is cell-free space available.
The evidence for contact inhibition initially presented was statistical.
It was inferred from the interactions of populations moving on a glass
surface that a reaction of this sort must be occurring. The reaction
between individual cells was described by Abercrombie and Ambrose
(1958). When the ruffled membrane on the leading edge of a moving
fibroblast makes contact with another fibroblast: (1) it ceases its
ruffling movements, and the associated pinocytosis; (2) it forms an
adhesion to the other fibroblast so close that no line of demarcation
between the two can be seen with the light microscope; the closeness of
the adhesions between fibroblasts was noted in Kredel's early microdissection studies (1927), and is evident from the distortion, followed by
springing apart, that happens when the cells separate by contrary
motion (Abercrombie and Heaysman, 1953); (3) if the ruffled membrane was expanding in size at the time of contact, the expansion
ceases; there may often be some contraction, momentarily drawing the
cells together (Abercrombie and Heaysman, 1953); (4) the locomotory
M. A B E R C R O M B I E
(Abercrombie, 1961b) perhaps more strongly than fibroblasts (Abercrombie, Heaysman and Karthauser, 1957), neurites and Schwann cells
(Weiss, 1934), and kidney epithelium (Weiss and Taylor, 1956) all
show the reaction.
(b) Cells as contact stimuli. The other structures that a cell comes into
contact with are the surfaces of surrounding cells, and these contacts
influence the direction of movement. One instance of this is contact
inhibition, so named by Abercrombie and Heaysman (1954) who
investigated its occurrence in fibroblasts. The phenomenon in fibroblasts will be discussed because more is perhaps known about their
contact inhibition than about that of other cells. The first tissue
culturist to suggest this particular behaviour reaction was, however, Leo
Loeb (1921) who used it to explain the dispersion of Limulus amoebocytes
from a dense focus, though he does not seem to have put the explanation
to experimental test. The hypothesis had still earlier precursors amongst
workers on the healing of wounds in epithelia (see Abercrombie and
Ambrose, 1962).
The behaviour in question can be summed up by saying that, when
contact inhibition is operative, a cell will not use another cell as substrate for its locomotion; and the change in locomotion necessary to
ensure this when cells are moving on a collision course happens only
when contact is made between the cells. When therefore a cell, moving
on a non-cellular substrate, runs into another cell, it will cease to move
in the direction that brought about the collision, except that if both
cells are going the same way a diminution of speed will suffice. A cell
stopped by contact as a rule moves away in a new direction, provided
there is cell-free space available.
The evidence for contact inhibition initially presented was statistical.
It was inferred from the interactions of populations moving on a glass
surface that a reaction of this sort must be occurring. The reaction
between individual cells was described by Abercrombie and Ambrose
(1958). When the ruffled membrane on the leading edge of a moving
fibroblast makes contact with another fibroblast: (1) it ceases its
ruffling movements, and the associated pinocytosis; (2) it forms an
adhesion to the other fibroblast so close that no line of demarcation
between the two can be seen with the light microscope; the closeness of
the adhesions between fibroblasts was noted in Kredel's early microdissection studies (1927), and is evident from the distortion, followed by
springing apart, that happens when the cells separate by contrary
motion (Abercrombie and Heaysman, 1953); (3) if the ruffled membrane was expanding in size at the time of contact, the expansion
ceases; there may often be some contraction, momentarily drawing the
cells together (Abercrombie and Heaysman, 1953); (4) the locomotory