IV.
ACTION
OF MORPHOSTATIC
SUBSTANCES
179
IV. The Aspects of Chemically-induced Growth Inhibition
A. Growth as a Synergistic Process
The term 'growth' includes very different biological phenomena. We
speak of growth if the dimensions of an organ increase regularly in
correlation with its increase in dry weight and total nitrogen content.
If the living mass of an organ increases the number of mitosis is augmented too. The content of proteins, nucleotides and lipids is also
increasing at a similar rate. Furthermore there exist mechanisms which,
as soon as an organ has reached a proportional size in relation to the
other organs, inhibit further growth. But in tumours a self-inhibition of
growth by intrinsic or extrinsic factors does not seem to exist, in contrast to normal organs where progressive self-inhibition by chemical
factors seems to occur regularly. Growth mostly involves increase of
cell number, the differentiation of the organisation and also the increase
of biologically important macromolecules. Before growth comes to a
standstill the different conditions for cell growth and cell division have
to be fulfilled as well as those for the synthesis of nucleic acids and
proteins.
G
A.M.
I
tumour tissue very rich in cathepsins. A small third tumour was also
very rich in cathepsins. The hosts of these regressing tumours showed a
normal catheptic activity of kidney and muscle which is in contrast to
hosts where tumours are growing. The catheptic activity of the liver
was slightly increased. It seems that the regressing tumours no longer
behaved like competing protein parasites but that they only left some
excess proteins to the liver. Regressing tumours seem to be very different
from growing tumours in their catheptic activity. If it should be possible
to influence the protein turnover by morphostatic substances which
activate the catheptic activity of a tumour, a 'self-degradation' of the
tumour proteins might appear. This could open a new way to chemotherapy of mammalian tumours. To investigate this question our research
group has planned a series of biochemical and biological experiments.
It follows now from the experiments of Benz and others that
cathepsins in rodents are sensitive and fast reacting enzyme systems.
They are capable of controlling protein degradation in organs and of
influencing thereby the growth and size of an organ. They also seem to
be connected with the keeping up of protein reserves in the blood. The
cathepsins behave differently in growing than in regressing tumours.
All this offers new prospects for the experimental modification of the
cathepsins in mammalian organisms.
ACTION
OF MORPHOSTATIC
SUBSTANCES
179
IV. The Aspects of Chemically-induced Growth Inhibition
A. Growth as a Synergistic Process
The term 'growth' includes very different biological phenomena. We
speak of growth if the dimensions of an organ increase regularly in
correlation with its increase in dry weight and total nitrogen content.
If the living mass of an organ increases the number of mitosis is augmented too. The content of proteins, nucleotides and lipids is also
increasing at a similar rate. Furthermore there exist mechanisms which,
as soon as an organ has reached a proportional size in relation to the
other organs, inhibit further growth. But in tumours a self-inhibition of
growth by intrinsic or extrinsic factors does not seem to exist, in contrast to normal organs where progressive self-inhibition by chemical
factors seems to occur regularly. Growth mostly involves increase of
cell number, the differentiation of the organisation and also the increase
of biologically important macromolecules. Before growth comes to a
standstill the different conditions for cell growth and cell division have
to be fulfilled as well as those for the synthesis of nucleic acids and
proteins.
G
A.M.
I
tumour tissue very rich in cathepsins. A small third tumour was also
very rich in cathepsins. The hosts of these regressing tumours showed a
normal catheptic activity of kidney and muscle which is in contrast to
hosts where tumours are growing. The catheptic activity of the liver
was slightly increased. It seems that the regressing tumours no longer
behaved like competing protein parasites but that they only left some
excess proteins to the liver. Regressing tumours seem to be very different
from growing tumours in their catheptic activity. If it should be possible
to influence the protein turnover by morphostatic substances which
activate the catheptic activity of a tumour, a 'self-degradation' of the
tumour proteins might appear. This could open a new way to chemotherapy of mammalian tumours. To investigate this question our research
group has planned a series of biochemical and biological experiments.
It follows now from the experiments of Benz and others that
cathepsins in rodents are sensitive and fast reacting enzyme systems.
They are capable of controlling protein degradation in organs and of
influencing thereby the growth and size of an organ. They also seem to
be connected with the keeping up of protein reserves in the blood. The
cathepsins behave differently in growing than in regressing tumours.
All this offers new prospects for the experimental modification of the
cathepsins in mammalian organisms.