TRANSPLANTATION OF CELL NUCLEI
11
it should be surrounded by cytoplasm and never exposed to an artificial
medium. For example Comandon and de Fonbrune (1939) report that
an Amoeba nucleus exposed to a saline solution is rejected by the recipient Amoeba like a foreign body. There are three main reasons why
it is very desirable to develop a medium which is much less harmful to
living nuclei than are the saline media currently used for nuclear transplantation. First, the cytoplasm injected with the nucleus might contain replicating nucleus-dependent components which could prevent
the nucleus coming into contact with the new cytoplasmic environment.
Second, such a medium would facilitate the transplantation of nuclei
from adult cells which have a relatively small volume of cytoplasm
round the nucleus. Lastly, it is desirable to improve the media used for
nuclei in cell-free systems, since it is not certain that these keep the
nuclei in a living condition, and therefore that they provide information
on the activity of normal living nuclei. Nuclear transplantation provides a direct and very sensitive test for the development of a nuclear
medium.
Briggs and King (1953) have carried out a series of nuclear transfers
in Banapipiens to test different media. They tried four modifications of
frog Ringer's solution designed either for the culture of whole cells or
for observation of lampbrush chromosomes. They also tried saline
solutions mixed with body cavity fluid, with glucose and proteins, or
with centrifuged embryo or egg homogenate and phosphate buffer.
They found that embryo or egg homogenates were very harmful so that
no cleavage at all was obtained from thirty-five transfers. The best
results were obtained with Niu and Twitty's saline medium whether or
not it was mixed with body cavity fluid. An interesting outcome of
these experiments was that the media affected nuclei in different ways.
Some media prevented nuclei and associated cytoplasm from promoting
normal cleavage, which might be due to damage to the nuclear membrane so as to interfere with division. Other media prevented nuclei
from supporting normal gastrulation or neurulation, suggesting chromosomal damage.
A systematic testing of nuclear media by nuclear transplantation
has been made by Burnstock and Philpot (1959) (Fig. 3, A-C). After
placing an amoeba in a drop of the solution to be tested, they pushed
the nucleus out into the solution and then back into the amoeba again
after about 30 sec. The effect of the medium upon the free nucleus was
judged by the percentage of re-nucleated amoebae which survived and
divided. They tested mainly various concentrations of sucrose, NaCl,
and phosphate buffer. Glycerol, MgCl 2 , and distilled water gave no
survival. Sucrose (between 0-005M and 0-2M), or NaCl (between
0-025M and 0-1M), or combinations of these with or without phosphate
11
it should be surrounded by cytoplasm and never exposed to an artificial
medium. For example Comandon and de Fonbrune (1939) report that
an Amoeba nucleus exposed to a saline solution is rejected by the recipient Amoeba like a foreign body. There are three main reasons why
it is very desirable to develop a medium which is much less harmful to
living nuclei than are the saline media currently used for nuclear transplantation. First, the cytoplasm injected with the nucleus might contain replicating nucleus-dependent components which could prevent
the nucleus coming into contact with the new cytoplasmic environment.
Second, such a medium would facilitate the transplantation of nuclei
from adult cells which have a relatively small volume of cytoplasm
round the nucleus. Lastly, it is desirable to improve the media used for
nuclei in cell-free systems, since it is not certain that these keep the
nuclei in a living condition, and therefore that they provide information
on the activity of normal living nuclei. Nuclear transplantation provides a direct and very sensitive test for the development of a nuclear
medium.
Briggs and King (1953) have carried out a series of nuclear transfers
in Banapipiens to test different media. They tried four modifications of
frog Ringer's solution designed either for the culture of whole cells or
for observation of lampbrush chromosomes. They also tried saline
solutions mixed with body cavity fluid, with glucose and proteins, or
with centrifuged embryo or egg homogenate and phosphate buffer.
They found that embryo or egg homogenates were very harmful so that
no cleavage at all was obtained from thirty-five transfers. The best
results were obtained with Niu and Twitty's saline medium whether or
not it was mixed with body cavity fluid. An interesting outcome of
these experiments was that the media affected nuclei in different ways.
Some media prevented nuclei and associated cytoplasm from promoting
normal cleavage, which might be due to damage to the nuclear membrane so as to interfere with division. Other media prevented nuclei
from supporting normal gastrulation or neurulation, suggesting chromosomal damage.
A systematic testing of nuclear media by nuclear transplantation
has been made by Burnstock and Philpot (1959) (Fig. 3, A-C). After
placing an amoeba in a drop of the solution to be tested, they pushed
the nucleus out into the solution and then back into the amoeba again
after about 30 sec. The effect of the medium upon the free nucleus was
judged by the percentage of re-nucleated amoebae which survived and
divided. They tested mainly various concentrations of sucrose, NaCl,
and phosphate buffer. Glycerol, MgCl 2 , and distilled water gave no
survival. Sucrose (between 0-005M and 0-2M), or NaCl (between
0-025M and 0-1M), or combinations of these with or without phosphate