20
TUNEO
YAMADA
component of 23-5 S was revealed (Κ. Takata, 1959). After removal of
the latter component by ultracentrifugation, the liver ribonucleoprotein
sample showed a very high inducing ability of archencephalic and deuterencephalic types (Hayashi and K. Takata, 1958). Further, K. Takata
(1959) demonstrated that kidney ribonucleoprotein can be distinguished
from liver ribonucleoprotein by a higher content of SH groups and
higher specific viscosity. The fact that ribonuclease does not suppress
the inducing ability of liver ribonucleoprotein, in spite of extensive
removal of RNA (Hayashi, 1959) agrees well with the observation that
trypsin and pepsin progressively suppress the inducing ability of the
same sample (Hayashi, 1958), and suggests that the protein moiety of
ribonucleoprotein carries the inducing ability.
In continuation of the work cited above Tiedemann and Tiedemann
(1959) succeeded in separating, from the chick embryo, a protein
fraction which gives a predominantly mesoderm-inducing effect in
insertion experiments. In electrophoresis the sample revealed a main
component accompanied by one or two very small components. Although
they hesitate to conclude that the main component is responsible for the
mesoderm induction, they calculated its molecular weight using data of
viscosity and sedimentation, and found it to be ca. 50,000. According
to the same paper, samples of ribonucleoprotein prepared from the chick
embryo by precipitation with streptomycin sulphate or protamine
sulphate gave deuterencephalic effects, while the supernate after the
precipitation revealed spino-caudal and trunk-mesodermal effects
(Tiedemann and Tiedemann, 1959). According to an oral communication,
similar results were obtained by Sasaki, Kawakami, and Ieri in an
experiment which coincides with that of Tiedemann and Tiedemann,
except for the use of the sandwich technique as the test method (29th
Annual Meeting of Japan Zoological Society, 1958).
We owe to Toivonen (1953, 1954) the discovery that the bone marrow
of the guinea-pig induces the isolated ectoderm to differentiate trunk
mesodermal structures. Later, it was found that not only mesodermal
structures, but also endodermal structures may be induced by the same
tissue (Yamada, 1958c). Recently Miss C. Takata succeeded in culturing
some of the sandwich explants containing the presumptive ectoderm of
the early gastrula of Triturus pyrrhogaster and ethanol-treated bone
marrow for 30-59 days at 18° C in Holtfreter solution buffered with
Tris to pH 7-4. The histological study of the explants as summarized in
Table II indicates that beside almost all mesodermal tissues which are
identifiable in this type of explant, a number of endodermal tissues are
recognized. Kuusi's observation (1957b) that the bone marrow extract
enhanced the differentiation of the host endoderm may have a bearing
on the endodermal induction observed in our laboratory.
TUNEO
YAMADA
component of 23-5 S was revealed (Κ. Takata, 1959). After removal of
the latter component by ultracentrifugation, the liver ribonucleoprotein
sample showed a very high inducing ability of archencephalic and deuterencephalic types (Hayashi and K. Takata, 1958). Further, K. Takata
(1959) demonstrated that kidney ribonucleoprotein can be distinguished
from liver ribonucleoprotein by a higher content of SH groups and
higher specific viscosity. The fact that ribonuclease does not suppress
the inducing ability of liver ribonucleoprotein, in spite of extensive
removal of RNA (Hayashi, 1959) agrees well with the observation that
trypsin and pepsin progressively suppress the inducing ability of the
same sample (Hayashi, 1958), and suggests that the protein moiety of
ribonucleoprotein carries the inducing ability.
In continuation of the work cited above Tiedemann and Tiedemann
(1959) succeeded in separating, from the chick embryo, a protein
fraction which gives a predominantly mesoderm-inducing effect in
insertion experiments. In electrophoresis the sample revealed a main
component accompanied by one or two very small components. Although
they hesitate to conclude that the main component is responsible for the
mesoderm induction, they calculated its molecular weight using data of
viscosity and sedimentation, and found it to be ca. 50,000. According
to the same paper, samples of ribonucleoprotein prepared from the chick
embryo by precipitation with streptomycin sulphate or protamine
sulphate gave deuterencephalic effects, while the supernate after the
precipitation revealed spino-caudal and trunk-mesodermal effects
(Tiedemann and Tiedemann, 1959). According to an oral communication,
similar results were obtained by Sasaki, Kawakami, and Ieri in an
experiment which coincides with that of Tiedemann and Tiedemann,
except for the use of the sandwich technique as the test method (29th
Annual Meeting of Japan Zoological Society, 1958).
We owe to Toivonen (1953, 1954) the discovery that the bone marrow
of the guinea-pig induces the isolated ectoderm to differentiate trunk
mesodermal structures. Later, it was found that not only mesodermal
structures, but also endodermal structures may be induced by the same
tissue (Yamada, 1958c). Recently Miss C. Takata succeeded in culturing
some of the sandwich explants containing the presumptive ectoderm of
the early gastrula of Triturus pyrrhogaster and ethanol-treated bone
marrow for 30-59 days at 18° C in Holtfreter solution buffered with
Tris to pH 7-4. The histological study of the explants as summarized in
Table II indicates that beside almost all mesodermal tissues which are
identifiable in this type of explant, a number of endodermal tissues are
recognized. Kuusi's observation (1957b) that the bone marrow extract
enhanced the differentiation of the host endoderm may have a bearing
on the endodermal induction observed in our laboratory.