I. PROBLEM
OF THE
ORGANIZER
19
and spino-caudal factors are chemically distinct, the former being
granules containing RNA and the latter a protein. Many of her results
(1953, 1957a, b) will be discussed later.
Meanwhile Tiedemann and Tiedemann (1956a) succeeded in separating
from the chick embryo, various protein fractions which showed clear
regional specificity when inserted into amphibian embryos. The samples
were prepared by extracting with phenol, pyridine, and ethanol,
precipitating with trichloroacetic acid and ammonium sulphate, and
fractionating in a high-speed centrifuge, and were then tested after
ethanol treatment.
In the experiments cited above the insertion method was used to test
the inductive effects of the fractions. It should be pointed out, however,
that the method does not completely exclude the participation of the
host mesoderm in the formation of induced structures. Further, the
regionality of the structures obtained may depend not entirely upon the
intrinsic tendency of the inductor, but also upon the location of the
inductor within the host embryo, which is difficult to control (Chuang,
1939; Vahs, 1956). Other possibilities, such as enzymatic action on the
implanted inductor from adjoining parts of the host embryo, are also
not excluded in the insertion experiments. A better method for testing
the regional effect of the sample is the sandwich technique, in which the
solid sample is put between two pieces of the presumptive ectoderm of
early gastrulae. This technique, introduced by Holtfreter (1933a), was
used in the following experiments conducted in our laboratory (c/.
Yamada, 1958a, b, c).
In our efforts to identify the agent responsible for spino-caudal and
deuterencephalic induction by guinea-pig kidney, it was noticed that
the 'small microsome fraction' and the acid-precipitable fraction of
014M NaCl extract of the tissue, both of which contain considerable
amount of ribonucleoprotein, have strong spino-caudal effects (Yamada
and K. Takata, 1955). With the use of streptomycin sulphate a ribonucleoprotein sample was prepared, which revealed a strong effect of spinocaudal and deuterencephalic types in sandwich experiments (Yamada
and Takata, 1956). Hayashi (1956) showed simultaneously that the
sample of ribonucleoprotein prepared in a similar way from guinea-pig
liver possesses a strong inducing ability of archencephalic type. In
electrophoresis the sample of kidney ribonucleoprotein indicated one
boundary whose ascending and descending mobilities were estimated to
be - 6·1~ - 6-3 and - 5·3~ - 5-4 respectively (K. Takata, 1959). Closely
similar values were obtained for the liver ribonucleoprotein sample. In
the sedimentation diagram of the kidney ribonucleoprotein sample a
single component of 6-7 S was observed, while in that of the liver
ribonucleoprotein sample beside the main component of 6-7 S a smaller
Β
A.M. I
OF THE
ORGANIZER
19
and spino-caudal factors are chemically distinct, the former being
granules containing RNA and the latter a protein. Many of her results
(1953, 1957a, b) will be discussed later.
Meanwhile Tiedemann and Tiedemann (1956a) succeeded in separating
from the chick embryo, various protein fractions which showed clear
regional specificity when inserted into amphibian embryos. The samples
were prepared by extracting with phenol, pyridine, and ethanol,
precipitating with trichloroacetic acid and ammonium sulphate, and
fractionating in a high-speed centrifuge, and were then tested after
ethanol treatment.
In the experiments cited above the insertion method was used to test
the inductive effects of the fractions. It should be pointed out, however,
that the method does not completely exclude the participation of the
host mesoderm in the formation of induced structures. Further, the
regionality of the structures obtained may depend not entirely upon the
intrinsic tendency of the inductor, but also upon the location of the
inductor within the host embryo, which is difficult to control (Chuang,
1939; Vahs, 1956). Other possibilities, such as enzymatic action on the
implanted inductor from adjoining parts of the host embryo, are also
not excluded in the insertion experiments. A better method for testing
the regional effect of the sample is the sandwich technique, in which the
solid sample is put between two pieces of the presumptive ectoderm of
early gastrulae. This technique, introduced by Holtfreter (1933a), was
used in the following experiments conducted in our laboratory (c/.
Yamada, 1958a, b, c).
In our efforts to identify the agent responsible for spino-caudal and
deuterencephalic induction by guinea-pig kidney, it was noticed that
the 'small microsome fraction' and the acid-precipitable fraction of
014M NaCl extract of the tissue, both of which contain considerable
amount of ribonucleoprotein, have strong spino-caudal effects (Yamada
and K. Takata, 1955). With the use of streptomycin sulphate a ribonucleoprotein sample was prepared, which revealed a strong effect of spinocaudal and deuterencephalic types in sandwich experiments (Yamada
and Takata, 1956). Hayashi (1956) showed simultaneously that the
sample of ribonucleoprotein prepared in a similar way from guinea-pig
liver possesses a strong inducing ability of archencephalic type. In
electrophoresis the sample of kidney ribonucleoprotein indicated one
boundary whose ascending and descending mobilities were estimated to
be - 6·1~ - 6-3 and - 5·3~ - 5-4 respectively (K. Takata, 1959). Closely
similar values were obtained for the liver ribonucleoprotein sample. In
the sedimentation diagram of the kidney ribonucleoprotein sample a
single component of 6-7 S was observed, while in that of the liver
ribonucleoprotein sample beside the main component of 6-7 S a smaller
Β
A.M. I