182
F. Ε.
LEHMANN
be true in our experiments on rats and for the tumour-host relations.
The concept of the 'dynamic state of proteins' does not seem to hold
only for growing systems. Even the organs of adult rats show this
dynamic state of proteins according to Borsook and Keighley (1935) and
Schoenheimer (1942) and his collaborators (c/. Campbell, 1958, p. 107).
It was implied by these authors that in the adult organism there is,
in addition to new protein synthesis which is necessary for secretion
and cell division, a constant breakdown and resynthesis of all protein
molecules at varying rates. Whether the concept of the role of a morphogenetic potential of metabolism holds also for tumours is not decided
yet. But our experiment with a pair of morphostatic substances gave
results which favour our concept.
The total inhibitory effects observed in regenerating tadpoles of Xenopus indicate the possibility of a total depression of the morphogenetic
potential (see result of v. Hahn and Lehmann, 1958; v. Hahn, 1959a).
The continuation of experimental studies on the biochemical action
of morphostatic substances upon the morphogenetic potential seems to
be justified by our preceding work.
3. Protein Metabolism and Purine Metabolism
There are several arguments in favour of the central role played
by protein turnover in the maintenance of morphogenetic potential.
The quinoxaline 3576 employed in our experiments probably does not
interfere primarily with the protein metabolism although this compound
is by itself a strong inhibitor of regeneration and a powerful synergist of
several morphostatic substances. Quinoxaline however can be antagonized by adenine, folic acid and aminopterine. This indicates that
quinoxaline interferes with purine metabolism, and possibly with the
citrovorum folic acid system. There is a certain structural relationship
between pterines and quinoxalines and this might explain to a certain
extent the antagonism to the folic acid system if one accepts the
validity of analogy principles. Structural analogue antagonists have been
known for some time especially for the folic acid group (aminopterin,
A-methopterine) and also for the group of purine analogs. Different
ring systems have been synthesized as efficient antagonists (triazolopyrimidine and pyrazolo-pyrimidine). As for quinoxaline, the modifying
action of this substance upon the activation of cathepsin seems to be
less persistent than with the aminoketones. Also the high synergistic
effect of 3576 and E 9 may serve as an argument for the interpretation
that 3576 modifies primarily other biochemical systems than E 9 . But
in the final effect quinoxaline 3576 seems to modify the protein turnover by interfering primarily with purine metabolism. Also the morphogenetic potential seems to be changed by this. Therefore purine
F. Ε.
LEHMANN
be true in our experiments on rats and for the tumour-host relations.
The concept of the 'dynamic state of proteins' does not seem to hold
only for growing systems. Even the organs of adult rats show this
dynamic state of proteins according to Borsook and Keighley (1935) and
Schoenheimer (1942) and his collaborators (c/. Campbell, 1958, p. 107).
It was implied by these authors that in the adult organism there is,
in addition to new protein synthesis which is necessary for secretion
and cell division, a constant breakdown and resynthesis of all protein
molecules at varying rates. Whether the concept of the role of a morphogenetic potential of metabolism holds also for tumours is not decided
yet. But our experiment with a pair of morphostatic substances gave
results which favour our concept.
The total inhibitory effects observed in regenerating tadpoles of Xenopus indicate the possibility of a total depression of the morphogenetic
potential (see result of v. Hahn and Lehmann, 1958; v. Hahn, 1959a).
The continuation of experimental studies on the biochemical action
of morphostatic substances upon the morphogenetic potential seems to
be justified by our preceding work.
3. Protein Metabolism and Purine Metabolism
There are several arguments in favour of the central role played
by protein turnover in the maintenance of morphogenetic potential.
The quinoxaline 3576 employed in our experiments probably does not
interfere primarily with the protein metabolism although this compound
is by itself a strong inhibitor of regeneration and a powerful synergist of
several morphostatic substances. Quinoxaline however can be antagonized by adenine, folic acid and aminopterine. This indicates that
quinoxaline interferes with purine metabolism, and possibly with the
citrovorum folic acid system. There is a certain structural relationship
between pterines and quinoxalines and this might explain to a certain
extent the antagonism to the folic acid system if one accepts the
validity of analogy principles. Structural analogue antagonists have been
known for some time especially for the folic acid group (aminopterin,
A-methopterine) and also for the group of purine analogs. Different
ring systems have been synthesized as efficient antagonists (triazolopyrimidine and pyrazolo-pyrimidine). As for quinoxaline, the modifying
action of this substance upon the activation of cathepsin seems to be
less persistent than with the aminoketones. Also the high synergistic
effect of 3576 and E 9 may serve as an argument for the interpretation
that 3576 modifies primarily other biochemical systems than E 9 . But
in the final effect quinoxaline 3576 seems to modify the protein turnover by interfering primarily with purine metabolism. Also the morphogenetic potential seems to be changed by this. Therefore purine