AMPHIBIAN AND INVERTEBRATE DEVELOPMENT 77
tent in the non-feeding larva, it can be concluded that there is a close
similarity in the changes of RNA content and proteolytic enzyme
activity. Our findings are in agreement with the observations of other
authors on a number of amphibians (Brächet, 1947, 1949, 1952; Kutsky,
1950;KrugeliseiaZ., 1952; Steinert, 1952).
Analysis of the embryos at the tail bud stage indicates that RNA,
like AG dipeptidase, occurs in higher concentrations in the cephalic
and caudal parts than in the intermediate zone (Fig. 4). These data, of
course, tell us nothing about the relation between proteolytic enzymes
and pentose nucleic acids, and only hypotheses can be formulated on
this subject (Brächet, 1960a, b).
The RNA content also increases during early metamorphosis. This
is suggestive of a correlation with the constructive phenomena occurring
in the new organism. This interpretation, however, conflicts with the
evidence given by Zacchei (1954) of an increase in the percentage of
RNA even in the regressive tail. Interesting relationships have been
observed between RNA content and ribonuclease activity (De Cesaris
Coromaldi, 1958) during embryonic development and metamorphosis of
Bufo vulgaris. In a critical survey of the problems, we suggested correlations between acid and alkaline ribonucleases and phosphatase
activity. It might be well to recall, at this point, some opinions on phosphatase activity during amphibian embryonic stages. These enzymes
appear to play an important role in several synthesizing processes, acting as catalysts in phosphorus transfer. It is well known that the yolk
contains phosphoproteins in high concentration. Barth and Jaeger
(1950) believe that they act as a protein source during development and
also as a supply of inorganic phosphate.
Harris (1946) detected a phosphoprotein phosphatase in the frog egg,
and Mezger-Freed (1953), who studied changes in its activity in the
development of Rana pipiens, observed that activity increased from the
neurula stage onwards. These findings integrate well with the data submitted by L0vtrup (1953a, b), who very convincingly demonstrated that
phosphoprotein P starts decreasing after the neurula stage. Lovtrup, in
agreement with Brächet (1947), suggested that the P released through
enzymatic activity is incorporated in the molecule of the nucleic acids
which are synthesized during development. These hypotheses are in
good agreement with the results obtained by Barth and Barth (1954),
who believe that the following four-stage system comes into action
during amphibian development: I—yolk phosphoprotein, II—phosphoprotein phosphatase, III—transphosphorylase, IV—phosphor-acceptor
protein. The last stage might be the precursor of nucleoproteins.
Our co-worker Szakacs (1951) found in the larva of Bufo vulgaris the
same amount of inorganic P that Barth and Jaeger (1947, 1950) re-
tent in the non-feeding larva, it can be concluded that there is a close
similarity in the changes of RNA content and proteolytic enzyme
activity. Our findings are in agreement with the observations of other
authors on a number of amphibians (Brächet, 1947, 1949, 1952; Kutsky,
1950;KrugeliseiaZ., 1952; Steinert, 1952).
Analysis of the embryos at the tail bud stage indicates that RNA,
like AG dipeptidase, occurs in higher concentrations in the cephalic
and caudal parts than in the intermediate zone (Fig. 4). These data, of
course, tell us nothing about the relation between proteolytic enzymes
and pentose nucleic acids, and only hypotheses can be formulated on
this subject (Brächet, 1960a, b).
The RNA content also increases during early metamorphosis. This
is suggestive of a correlation with the constructive phenomena occurring
in the new organism. This interpretation, however, conflicts with the
evidence given by Zacchei (1954) of an increase in the percentage of
RNA even in the regressive tail. Interesting relationships have been
observed between RNA content and ribonuclease activity (De Cesaris
Coromaldi, 1958) during embryonic development and metamorphosis of
Bufo vulgaris. In a critical survey of the problems, we suggested correlations between acid and alkaline ribonucleases and phosphatase
activity. It might be well to recall, at this point, some opinions on phosphatase activity during amphibian embryonic stages. These enzymes
appear to play an important role in several synthesizing processes, acting as catalysts in phosphorus transfer. It is well known that the yolk
contains phosphoproteins in high concentration. Barth and Jaeger
(1950) believe that they act as a protein source during development and
also as a supply of inorganic phosphate.
Harris (1946) detected a phosphoprotein phosphatase in the frog egg,
and Mezger-Freed (1953), who studied changes in its activity in the
development of Rana pipiens, observed that activity increased from the
neurula stage onwards. These findings integrate well with the data submitted by L0vtrup (1953a, b), who very convincingly demonstrated that
phosphoprotein P starts decreasing after the neurula stage. Lovtrup, in
agreement with Brächet (1947), suggested that the P released through
enzymatic activity is incorporated in the molecule of the nucleic acids
which are synthesized during development. These hypotheses are in
good agreement with the results obtained by Barth and Barth (1954),
who believe that the following four-stage system comes into action
during amphibian development: I—yolk phosphoprotein, II—phosphoprotein phosphatase, III—transphosphorylase, IV—phosphor-acceptor
protein. The last stage might be the precursor of nucleoproteins.
Our co-worker Szakacs (1951) found in the larva of Bufo vulgaris the
same amount of inorganic P that Barth and Jaeger (1947, 1950) re-