140
ALBERTO MONROY AND RACHELE MAGGIO
The study of the nature of the metabolic block of the unfertilized egg, of
its building up in the course of maturation and of its release as a result of
fertilization appears, therefore, to be one of the most promising avenues
for further research to contribute to the understanding of early sea
urchin development.
A crucial point in the respiratory curve is the plateau which extends
from the early blastula—when the first differentiation of the embryo,
i.e., ciliation, becomes visible—to the mesenchyme blastula, which is
considered to be the stage at which actual embryonic differentiation
starts. Some important changes in the metabolism of the embryo have
been observed at the onset of, or during, the plateau (see Section III, A)
but their significance in morphogenesis is not yet clearly understood. A
comparative analysis carried out on eggs offering as large a variety as
possible of morphological, physiological and ecological conditions would
probably help to solve this challenging question.
Another promising line of investigation appears to be the study of the
various RNA fractions and their metabolism. Indeed the sea urchin egg
seems suitable material for finding out whether or not the recent results
derived from the study of bacterial systems are entirely applicable to
multicellular organisms and, more important, their role in differentiation.
In spite of numerous attempts, the evidence concerning the appearance
of new proteins is meagre and mainly rests on the results of serological
experiments. However, some enzymes, such as alkaline phosphatase
whose activity is low at the onset of development and then undergoes
sudden increase, may be particularly helpful in investigating whether
the burst of activity is due to an activation of a pre-existing enzyme
protein or to an actual synthesis. The study of enzymes known to be
inducible in other systems may be of particular importance. In fact this
would have a bearing on the problem as to whether or not enzyme
induction plays a significant role in morphogenesis and differentiation.
The work by the Authors has been supported by grants from the
Consiglio Nazionale delle Ricerche, the Rockefeller Foundation and the
National Institutes of Health, U.S. Public Health Service (GR-06211).
The authors wish to express their indebtedness to Drs. J. Collier,
J. C. Dan, G. Giudice, E. Nakano and E. Scarano for helpful discussions
and suggestions and to Drs. A. Ficq, Y. Ishida and E. Scarano for
permission to quote unpublished results of their work.
References
Abrams, R. (1951). Exp. Cell Res. 2, 235.
Afzelius, B. A. (1956). Exp. Cell Res. 10, 257.
Afzelius, B. A. (1957). Z. Zellforsch. 45, 660.
ALBERTO MONROY AND RACHELE MAGGIO
The study of the nature of the metabolic block of the unfertilized egg, of
its building up in the course of maturation and of its release as a result of
fertilization appears, therefore, to be one of the most promising avenues
for further research to contribute to the understanding of early sea
urchin development.
A crucial point in the respiratory curve is the plateau which extends
from the early blastula—when the first differentiation of the embryo,
i.e., ciliation, becomes visible—to the mesenchyme blastula, which is
considered to be the stage at which actual embryonic differentiation
starts. Some important changes in the metabolism of the embryo have
been observed at the onset of, or during, the plateau (see Section III, A)
but their significance in morphogenesis is not yet clearly understood. A
comparative analysis carried out on eggs offering as large a variety as
possible of morphological, physiological and ecological conditions would
probably help to solve this challenging question.
Another promising line of investigation appears to be the study of the
various RNA fractions and their metabolism. Indeed the sea urchin egg
seems suitable material for finding out whether or not the recent results
derived from the study of bacterial systems are entirely applicable to
multicellular organisms and, more important, their role in differentiation.
In spite of numerous attempts, the evidence concerning the appearance
of new proteins is meagre and mainly rests on the results of serological
experiments. However, some enzymes, such as alkaline phosphatase
whose activity is low at the onset of development and then undergoes
sudden increase, may be particularly helpful in investigating whether
the burst of activity is due to an activation of a pre-existing enzyme
protein or to an actual synthesis. The study of enzymes known to be
inducible in other systems may be of particular importance. In fact this
would have a bearing on the problem as to whether or not enzyme
induction plays a significant role in morphogenesis and differentiation.
The work by the Authors has been supported by grants from the
Consiglio Nazionale delle Ricerche, the Rockefeller Foundation and the
National Institutes of Health, U.S. Public Health Service (GR-06211).
The authors wish to express their indebtedness to Drs. J. Collier,
J. C. Dan, G. Giudice, E. Nakano and E. Scarano for helpful discussions
and suggestions and to Drs. A. Ficq, Y. Ishida and E. Scarano for
permission to quote unpublished results of their work.
References
Abrams, R. (1951). Exp. Cell Res. 2, 235.
Afzelius, B. A. (1956). Exp. Cell Res. 10, 257.
Afzelius, B. A. (1957). Z. Zellforsch. 45, 660.