10
TUNEO
YAMADA
the pH range lower than 3, and disappearance of stainability after all
the treatments listed above. Further, under the ultraviolet microscope
the absorption at 260 ηΐμ, was absent in the superficial layer of the
intact yolk platelets. Thus the presence of an appreciable amount of
RNA in the superficial layer of the yolk platelets seems to be ruled out.
A further series of investigations on metachromasia, PAS reaction,
Hale's reaction, and the effect of hyalouronidase suggested the presence
of acid polysaccharide in the superficial layer (K. Takata and Ono,
unpublished data). This finding, if confirmed, may link the superficial
layer of the yolk platelets with the secretory activity of the organizer
cells, which was discovered in 1906 by the Italian embryologist, Ruffini.
According to the data published in his monumental book (Ruffini, 1925)
secretion granules observable by the method of Altmann-Galeotti are
present in the stalk of the bottle-shaped organizer cells, during the early
phase of invagination of the blastopore lip in Triturus embryos. The
cavity of the archenteron is filled with a secretion product which he
assumes to be mucin. A similar secretion is observable also in neural
tube formation where again the characteristic bottle-shaped cells
appear leading to invagination of the neural epithelium. Motomura
noticed the secretory phenomena of amphibian organizers without
knowing of Ruffini's writings. Later he confirmed the essential points
made by Ruffini, using the PAS reaction which is positive in the
secretory products (oral communication at the 29th Annual Meeting of
Japan Zoological Society, 1958). It is not improbable that disappearance
of the superficial layer of yolk platelets in the invaginating organizer
cells is directly related to secretion of these cells, the 100 Á particles
playing a role as precursor of the secretion.
E. Pigment Granules
A definite structural difference is observed between pigment granules
of urodeles (Eakin and Lehmann, 1957; Karasaki, 1959a) and those of
anura (Eakin and Lehmann, 1957; Karasaki, unpublished work). In the
urodeles the granule measuring 0-4-0-6 μ is composed of a number of
subunits measuring ca. 500 Ä which appear extremely dark in osmiumfixed electron micrographs. In the anura the granule is a single spherical
body of about 0-3-0-5 μ and possesses an external layer with a higher
density than the internal core, in which some small dark dots may be
recognized. In both types of pigment granules a fine investing membrane
is present. The granules are abundantly present in the ectodermal cells
preferentially distributed in the cortical layer and perinuclear zone of
the cell. In the neural cell-line the granules diminish in number during
development, while no clear decrease is observed in the epidermal
cell-line.
TUNEO
YAMADA
the pH range lower than 3, and disappearance of stainability after all
the treatments listed above. Further, under the ultraviolet microscope
the absorption at 260 ηΐμ, was absent in the superficial layer of the
intact yolk platelets. Thus the presence of an appreciable amount of
RNA in the superficial layer of the yolk platelets seems to be ruled out.
A further series of investigations on metachromasia, PAS reaction,
Hale's reaction, and the effect of hyalouronidase suggested the presence
of acid polysaccharide in the superficial layer (K. Takata and Ono,
unpublished data). This finding, if confirmed, may link the superficial
layer of the yolk platelets with the secretory activity of the organizer
cells, which was discovered in 1906 by the Italian embryologist, Ruffini.
According to the data published in his monumental book (Ruffini, 1925)
secretion granules observable by the method of Altmann-Galeotti are
present in the stalk of the bottle-shaped organizer cells, during the early
phase of invagination of the blastopore lip in Triturus embryos. The
cavity of the archenteron is filled with a secretion product which he
assumes to be mucin. A similar secretion is observable also in neural
tube formation where again the characteristic bottle-shaped cells
appear leading to invagination of the neural epithelium. Motomura
noticed the secretory phenomena of amphibian organizers without
knowing of Ruffini's writings. Later he confirmed the essential points
made by Ruffini, using the PAS reaction which is positive in the
secretory products (oral communication at the 29th Annual Meeting of
Japan Zoological Society, 1958). It is not improbable that disappearance
of the superficial layer of yolk platelets in the invaginating organizer
cells is directly related to secretion of these cells, the 100 Á particles
playing a role as precursor of the secretion.
E. Pigment Granules
A definite structural difference is observed between pigment granules
of urodeles (Eakin and Lehmann, 1957; Karasaki, 1959a) and those of
anura (Eakin and Lehmann, 1957; Karasaki, unpublished work). In the
urodeles the granule measuring 0-4-0-6 μ is composed of a number of
subunits measuring ca. 500 Ä which appear extremely dark in osmiumfixed electron micrographs. In the anura the granule is a single spherical
body of about 0-3-0-5 μ and possesses an external layer with a higher
density than the internal core, in which some small dark dots may be
recognized. In both types of pigment granules a fine investing membrane
is present. The granules are abundantly present in the ectodermal cells
preferentially distributed in the cortical layer and perinuclear zone of
the cell. In the neural cell-line the granules diminish in number during
development, while no clear decrease is observed in the epidermal
cell-line.