78
ENRICO URBANI
ported for Bana pipiens, but he observed a higher percentage of easily
hydrolysable P (chiefly ATP). This biochemical difference among zoological species seems to conform with the observation of Spirito (1936,
1940) that Bufo vulgaris shows a high degree of resistance to anaerobic
conditions.
The marked decrease in phosphoprotein P during embryogenesis is
probably due to the activity of both alkaline and acid phosphatase.
We do not mean just two enzymes, but a whole group of enzymes, some
of which act on the substrate in an alkaline medium and some which
act on the same substrate in an acid medium.
Several authors have conducted chemical studies on the change in
phosphatase activity in the embryonic development of Anura (Krugelis,
1950; Krugelis et al., 1952; Lovtrup, 1955): generally they were able to
demonstrate an increase in enzymatic activity during morphogenesis
and growth of the embryo.
The work of De Cesaris Coromaldi (1955) on Bufo vulgaris showed that
four different phosphatases were present during the development of the
toad: on the basis of differences in activity, each of them can be assumed
to play a different role in the embryonic stages. A substantial increaso
in both acid and alkaline phenylphosphatase (pH 4-6 and 9-6 respectively) also occurred from the gastrula-tail bud stage up to the end of
embryonic development. Alkaline glycerophosphatase increased in activity a little later than the corresponding phenylphosphatase; the increase
in acid glycerophosphatase activity was markedly lower in the same
developmental period.
In his study on Bana platyrrhinus, Lovtrup (1958) also came to the
conclusion that at least two, and probably more, phosphatases come
into play gradually during embryonic development.
The determinations made on isolated portions of the embryo at the
tail bud stage (Fig. 4) show that phosphatase is more active in the
caudal and cephalic regions of the embryo than in the intermediate zone.
During metamorphosis, the activity of acid phenylphosphatase increases gradually and appreciably from the second to the fifth stage,
while alkaline phenylphosphatase activity increases but slightly (Bellini,
1958).
There is thus some analogy in the degree of activity of phosphatases
and ribonucleases (De Cesaris Coromaldi, 1958); this relationship also
holds in the case of the liver (Frieden and Mathews, 1958) during the
metamorphosis of Bana grylio.
In the regressing tail, the activity of acid phenylphosphatase increases gradually from the first to the fourth stage, while that of alkaline
phenylphosphatase increases only slightly at the beginning of metamorphosis, attaining a maximum towards its end. The difference in
ENRICO URBANI
ported for Bana pipiens, but he observed a higher percentage of easily
hydrolysable P (chiefly ATP). This biochemical difference among zoological species seems to conform with the observation of Spirito (1936,
1940) that Bufo vulgaris shows a high degree of resistance to anaerobic
conditions.
The marked decrease in phosphoprotein P during embryogenesis is
probably due to the activity of both alkaline and acid phosphatase.
We do not mean just two enzymes, but a whole group of enzymes, some
of which act on the substrate in an alkaline medium and some which
act on the same substrate in an acid medium.
Several authors have conducted chemical studies on the change in
phosphatase activity in the embryonic development of Anura (Krugelis,
1950; Krugelis et al., 1952; Lovtrup, 1955): generally they were able to
demonstrate an increase in enzymatic activity during morphogenesis
and growth of the embryo.
The work of De Cesaris Coromaldi (1955) on Bufo vulgaris showed that
four different phosphatases were present during the development of the
toad: on the basis of differences in activity, each of them can be assumed
to play a different role in the embryonic stages. A substantial increaso
in both acid and alkaline phenylphosphatase (pH 4-6 and 9-6 respectively) also occurred from the gastrula-tail bud stage up to the end of
embryonic development. Alkaline glycerophosphatase increased in activity a little later than the corresponding phenylphosphatase; the increase
in acid glycerophosphatase activity was markedly lower in the same
developmental period.
In his study on Bana platyrrhinus, Lovtrup (1958) also came to the
conclusion that at least two, and probably more, phosphatases come
into play gradually during embryonic development.
The determinations made on isolated portions of the embryo at the
tail bud stage (Fig. 4) show that phosphatase is more active in the
caudal and cephalic regions of the embryo than in the intermediate zone.
During metamorphosis, the activity of acid phenylphosphatase increases gradually and appreciably from the second to the fifth stage,
while alkaline phenylphosphatase activity increases but slightly (Bellini,
1958).
There is thus some analogy in the degree of activity of phosphatases
and ribonucleases (De Cesaris Coromaldi, 1958); this relationship also
holds in the case of the liver (Frieden and Mathews, 1958) during the
metamorphosis of Bana grylio.
In the regressing tail, the activity of acid phenylphosphatase increases gradually from the first to the fourth stage, while that of alkaline
phenylphosphatase increases only slightly at the beginning of metamorphosis, attaining a maximum towards its end. The difference in