166
F. Ε.
LEHMANN
jected experiments of Sträuli. In this respect there is at present a large
research programme realizable especially for the different types of
morphostatic substances and their synergistic combinations.
It cannot be decided at present whether such biological investigations
on tumours can be of use to clinical research on human beings. Apparently
the basis of tumour biology in man is less exactly known than that of
other mammals. There remains much to be done by a clinician who has
some experience in tumour biology and who is interested in doing
clinical experiments.
The progress of tumour biology depends not only on restricted and
traditional research on a purely biological level. For the biology of
growing organs and of growing tumours offers many stimulating
biochemical aspects. The new results of our research group seem to
indicate that increase or decrease of proteins in growing organs or
regenerates is governed to a high degree by tissue proteases (cathepsins).
Some cathepsins are strongly active in growing regenerates. We think
that experimentally activated cathepsins in a regenerate may bring
about a regression of the blastema instead of blastema increase.
Cathepsins are still more activated by certain experimental treatments
and the regenerates show under these conditions signs of strong inhibition. We suppose in these cases that an experimental shifting of
the equilibrium between synthesizing and degrading enzymes such as
cathepsins leads to an excess of protein breakdown and at the same time
to an inhibition of tissue growth. An analogous situation seems to exist
in starving or in metamorphosing tadpoles. Here again tissue breakdown
is greater than tissue growth and also in these cases there is a strong
rise of cathepsin activity (Benz, 1957; Weber, 1957a, b). In view of this
special morphogenetic function of cathepsins in tissue regression, it
seemed interesting to investigate in more detail the properties and
functions of cathepsins in amphibians and mammals. From this we may
obtain more information concerning the modifiability of the cathepsins.
The principle of experimental control of tissue cathepsins may indicate
a new way to influence tissue growth by experimentally modifying the
cathepsins.
III. Proteases of Growing Tissues and
the Regulation of Growth Processes
Normally growing tissues seem to possess a dynamic equilibrium of
enzyme systems in which there is always an excess of products of
synthesis. This excess appears regularly as an increase of newly formed
protein structures. This dynamic equilibrium is labile and can be easily
modified by experimental conditions (Jensen et al., 1956; Deuchar et. al.,
F. Ε.
LEHMANN
jected experiments of Sträuli. In this respect there is at present a large
research programme realizable especially for the different types of
morphostatic substances and their synergistic combinations.
It cannot be decided at present whether such biological investigations
on tumours can be of use to clinical research on human beings. Apparently
the basis of tumour biology in man is less exactly known than that of
other mammals. There remains much to be done by a clinician who has
some experience in tumour biology and who is interested in doing
clinical experiments.
The progress of tumour biology depends not only on restricted and
traditional research on a purely biological level. For the biology of
growing organs and of growing tumours offers many stimulating
biochemical aspects. The new results of our research group seem to
indicate that increase or decrease of proteins in growing organs or
regenerates is governed to a high degree by tissue proteases (cathepsins).
Some cathepsins are strongly active in growing regenerates. We think
that experimentally activated cathepsins in a regenerate may bring
about a regression of the blastema instead of blastema increase.
Cathepsins are still more activated by certain experimental treatments
and the regenerates show under these conditions signs of strong inhibition. We suppose in these cases that an experimental shifting of
the equilibrium between synthesizing and degrading enzymes such as
cathepsins leads to an excess of protein breakdown and at the same time
to an inhibition of tissue growth. An analogous situation seems to exist
in starving or in metamorphosing tadpoles. Here again tissue breakdown
is greater than tissue growth and also in these cases there is a strong
rise of cathepsin activity (Benz, 1957; Weber, 1957a, b). In view of this
special morphogenetic function of cathepsins in tissue regression, it
seemed interesting to investigate in more detail the properties and
functions of cathepsins in amphibians and mammals. From this we may
obtain more information concerning the modifiability of the cathepsins.
The principle of experimental control of tissue cathepsins may indicate
a new way to influence tissue growth by experimentally modifying the
cathepsins.
III. Proteases of Growing Tissues and
the Regulation of Growth Processes
Normally growing tissues seem to possess a dynamic equilibrium of
enzyme systems in which there is always an excess of products of
synthesis. This excess appears regularly as an increase of newly formed
protein structures. This dynamic equilibrium is labile and can be easily
modified by experimental conditions (Jensen et al., 1956; Deuchar et. al.,