58
G.
REVERBERI
Amphibians (Karasaki, 1959). In the interior of the yolk granules some
structure can be seen.
By the use of cytochemical reactions one can get a more exact idea of
these constituents.
The Unna-Brachet reaction (methyl green-pyronine), controlled with
ribonuclease, colours intensively only the two hyaline layers, the
centripetal and the centrifugal ones; this is to be expected if one recalls
that, with the electron microscope, granules all around the ergastoplasmic vesicles were seen, at least in the centripetal layer. Since
previous treatment with ribonuclease makes the reaction negative, one
can assume that the granules around the ergastoplasmic vesicles really
contain ribonucleic acid (RNA). This leads to the conclusion that in the
Ciona egg there are two kinds of RNA granules: those which after
centrifugation collect at the centripetal pole, and those which collect at
the centrifugal one. The latter are coarser than those of the centripetal
zone, and are osmiophilic.
The specific cytochemical reaction for glycogen also stains the hyaline
layers a brilliant red (La Spina, in press): previous treatment with
salivary amylase inhibits the reaction. The glycogen has a granular
aspect, and the granules in the centrifugal zone are coarser than those
of the centripetal one. Granules of glycogen can also be found at the
periphery of the egg, under the cortex; they participate, together with
the mitochondria, in the modifications of the cortex at fertilization and
segmentation.
The Nadi-reaction (La Spina, 1958) colours in brilliant blue only the
mitochondrial layer; the reaction is negative if the egg has been pretreated with sodium azide, which is a specific inhibitor for cytochrome
oxidase. Janus green also colours only the mitochondrial layer.
One can summarize the facts about the constituents of the Ciona egg
by saying that this egg is very poor in oils but, ón the contrary, is
rich in RNA and glycogen and its RNA granules are of two different
sorts.
B. The Constituents of the Normal (not Centrifuged) Egg
The studies on the constituents of the centrifuged egg establish only
that certain substances are present in a certain relative quantity, but
they give no idea of the topographical relations which normally exist
between them. Development is certainly due to the interactions of the
egg constituents, and thus research on their location with respect to
each other in the normal egg is absolutely necessary. The disposition of
the various constituents can be radically different in the unfertilized
and in the fertilized egg, so that it is necessary to study both.
G.
REVERBERI
Amphibians (Karasaki, 1959). In the interior of the yolk granules some
structure can be seen.
By the use of cytochemical reactions one can get a more exact idea of
these constituents.
The Unna-Brachet reaction (methyl green-pyronine), controlled with
ribonuclease, colours intensively only the two hyaline layers, the
centripetal and the centrifugal ones; this is to be expected if one recalls
that, with the electron microscope, granules all around the ergastoplasmic vesicles were seen, at least in the centripetal layer. Since
previous treatment with ribonuclease makes the reaction negative, one
can assume that the granules around the ergastoplasmic vesicles really
contain ribonucleic acid (RNA). This leads to the conclusion that in the
Ciona egg there are two kinds of RNA granules: those which after
centrifugation collect at the centripetal pole, and those which collect at
the centrifugal one. The latter are coarser than those of the centripetal
zone, and are osmiophilic.
The specific cytochemical reaction for glycogen also stains the hyaline
layers a brilliant red (La Spina, in press): previous treatment with
salivary amylase inhibits the reaction. The glycogen has a granular
aspect, and the granules in the centrifugal zone are coarser than those
of the centripetal one. Granules of glycogen can also be found at the
periphery of the egg, under the cortex; they participate, together with
the mitochondria, in the modifications of the cortex at fertilization and
segmentation.
The Nadi-reaction (La Spina, 1958) colours in brilliant blue only the
mitochondrial layer; the reaction is negative if the egg has been pretreated with sodium azide, which is a specific inhibitor for cytochrome
oxidase. Janus green also colours only the mitochondrial layer.
One can summarize the facts about the constituents of the Ciona egg
by saying that this egg is very poor in oils but, ón the contrary, is
rich in RNA and glycogen and its RNA granules are of two different
sorts.
B. The Constituents of the Normal (not Centrifuged) Egg
The studies on the constituents of the centrifuged egg establish only
that certain substances are present in a certain relative quantity, but
they give no idea of the topographical relations which normally exist
between them. Development is certainly due to the interactions of the
egg constituents, and thus research on their location with respect to
each other in the normal egg is absolutely necessary. The disposition of
the various constituents can be radically different in the unfertilized
and in the fertilized egg, so that it is necessary to study both.