GROWTH INDUCED BY DAMAGE
25
skin, no hair growth stimulation would occur because no loss of mass
will have been recorded. We assume that the devices in the skin that
monitor mass are organ-specific, and, although skin has been replaced by
tumor, the loss of skin is detected. Therefore, it is important to know if,
in fact, the mechanisms for monitoring skin mass are organ-specific.
Unfortunately, although the evidence is strong, it is not conclusive. First
of all, in all cases that have been studied in which the loss of mass results
in the initiation of growth, as in compensatory hypertrophy, the growth
is largely limited to the organ concerned (Abercrombie, 1957; Bullough,
1962, 1965; Swann, 1958; Weiss and Kavanau, 1957; Wright, 1958).
In some cases where the loss of mass of one organ leads to an increase in mitotic activity in other organs, it is minimal (Paschkis, 1958).
Therefore we would expect the control of growth of the skin to be also
organ-specific.
In the case of the skin, if the monitoring devices for mass are not
organ-specific we should be able to induce hair growth by cutting out the
tumor after it has replaced the skin. Argyris and Trimble (1964a) have
cut out the Ehrlich ascites tumor in a group of mice in which the tumor
has completely replaced the overlying skin. In no case has this resulted
in the stimulation of growth of the surrounding resting hair follicles.
However, the experiment is limited by the fact that not all the tumor can
be removed without damaging the surrounding skin. But a large gap in
the skin remains for at least 2-3 weeks before the tumor remnants have
significantly regrown (Argyris and Trimble, 1964a).
The argument may also be raised that removing organ mass with the
use of a tumor is different from that initiated by cutting away a portion
of an organ, or one of a pair of bilateral organs, because the loss of mass
produced by tumor invasion is gradual. For the skin to detect the loss of
mass it must be abrupt. That the removal of organ mass by a tumor is
similar to that removed by cutting away a portion of an organ is shown
by the following experiments. Kollar (1963) has implanted the Ehrlich
ascites tumor in the left lateral lobe of the liver of a mouse. This procedure does not result in an increase in mitotic activity around the implanted tumor or in the other lobes of the liver. The tumor grows and
soon invades the remainder of the left lateral lobe. When half of the left
lateral lobe is removed by the tumor, there is an increase in mitotic
activity in the other lobes of the liver. The removal of about half of the
left lateral lobe is precisely the point at which the remainder of the liver
undergoes compensatory hypertrophy, when liver removal is accomplished
by cutting (MacDonald et al, 1962; Bucher and Swaffield, 1964). That
25
skin, no hair growth stimulation would occur because no loss of mass
will have been recorded. We assume that the devices in the skin that
monitor mass are organ-specific, and, although skin has been replaced by
tumor, the loss of skin is detected. Therefore, it is important to know if,
in fact, the mechanisms for monitoring skin mass are organ-specific.
Unfortunately, although the evidence is strong, it is not conclusive. First
of all, in all cases that have been studied in which the loss of mass results
in the initiation of growth, as in compensatory hypertrophy, the growth
is largely limited to the organ concerned (Abercrombie, 1957; Bullough,
1962, 1965; Swann, 1958; Weiss and Kavanau, 1957; Wright, 1958).
In some cases where the loss of mass of one organ leads to an increase in mitotic activity in other organs, it is minimal (Paschkis, 1958).
Therefore we would expect the control of growth of the skin to be also
organ-specific.
In the case of the skin, if the monitoring devices for mass are not
organ-specific we should be able to induce hair growth by cutting out the
tumor after it has replaced the skin. Argyris and Trimble (1964a) have
cut out the Ehrlich ascites tumor in a group of mice in which the tumor
has completely replaced the overlying skin. In no case has this resulted
in the stimulation of growth of the surrounding resting hair follicles.
However, the experiment is limited by the fact that not all the tumor can
be removed without damaging the surrounding skin. But a large gap in
the skin remains for at least 2-3 weeks before the tumor remnants have
significantly regrown (Argyris and Trimble, 1964a).
The argument may also be raised that removing organ mass with the
use of a tumor is different from that initiated by cutting away a portion
of an organ, or one of a pair of bilateral organs, because the loss of mass
produced by tumor invasion is gradual. For the skin to detect the loss of
mass it must be abrupt. That the removal of organ mass by a tumor is
similar to that removed by cutting away a portion of an organ is shown
by the following experiments. Kollar (1963) has implanted the Ehrlich
ascites tumor in the left lateral lobe of the liver of a mouse. This procedure does not result in an increase in mitotic activity around the implanted tumor or in the other lobes of the liver. The tumor grows and
soon invades the remainder of the left lateral lobe. When half of the left
lateral lobe is removed by the tumor, there is an increase in mitotic
activity in the other lobes of the liver. The removal of about half of the
left lateral lobe is precisely the point at which the remainder of the liver
undergoes compensatory hypertrophy, when liver removal is accomplished
by cutting (MacDonald et al, 1962; Bucher and Swaffield, 1964). That