TRANSPLANTATION OF CELL NUCLEI
41
substances of this kind have been demonstrated by nuclear transplantation in Acetabularia, and what could be a messenger-RNA has
been revealed by the transplantation of Amoeba nuclei. These experiments have shown that the stability of these substances can differ from
one kind of cell to another. Nuclear transfer experiments in Amphibia
and Amoeba have yielded no conclusive evidence for replicating cytoplasmic components which promote cell differentiation. At present it
seems simplest to assume that substances of nuclear origin can persist
but not replicate in the cytoplasm.
It is appropriate to enquire to what problems in cell differentiation
and morphogenesis the technique of nuclear transplantation can still be
usefully applied. The experiments discussed in Section II suggest that
the scope of the technique may soon be broadened to include a greater
range of adult cell types. It is not yet possible to transplant the nuclei
from such cells. This is partly because most differentiated cells divide
only very rarely, but this difficulty can perhaps be overcome by taking
nuclei from regenerating tissue. It is also because no artificial medium
has been found which is not lethal to animal nuclei. Nuclear transplantation is being used to try and develop a medium which is less lethal
to living nuclei, and this would enormously facilitate the transplantation
of nuclei from adult cells and cells in culture, as well as work on isolated
nuclei in general. Together with other experimental approaches, the
transplantation of living cell nuclei can be expected to continue its
contribution to our understanding of the control of gene activity.
Acknowledgements
The author is most grateful to Dr. E. J. DuPraw for permission to
quote some of his unpublished work, and to Dr. J. F. Wilson for showing
him the manuscript of a paper before its publication. Mr. C. F. Graham
has very kindly allowed some of his unpublished work to be included in
this paper and has provided helpful comments on it. The author gratefully acknowledges that some of his work reported in this paper was
supported by a research grant from the Medical Research Council.
References
Allfrey, V. G., Littau, V.C. and Mirsky, A. E. (1963). Proc. nat. Acad. Set., Wash.
49, 414.
Astaurov, B. L. and Ostriakova-Varshaver, V. P. (1957). J. Embryol. exp. Morph.
5, 449.
Beale, G. H. (1954). 'The Genetics of Paramecium aurelia\ Cambridge Monographs
in Experimental Biology, Vol. 2. Cambridge,
Becker, H. J. (1959). Chromoeoma 10, 654.
41
substances of this kind have been demonstrated by nuclear transplantation in Acetabularia, and what could be a messenger-RNA has
been revealed by the transplantation of Amoeba nuclei. These experiments have shown that the stability of these substances can differ from
one kind of cell to another. Nuclear transfer experiments in Amphibia
and Amoeba have yielded no conclusive evidence for replicating cytoplasmic components which promote cell differentiation. At present it
seems simplest to assume that substances of nuclear origin can persist
but not replicate in the cytoplasm.
It is appropriate to enquire to what problems in cell differentiation
and morphogenesis the technique of nuclear transplantation can still be
usefully applied. The experiments discussed in Section II suggest that
the scope of the technique may soon be broadened to include a greater
range of adult cell types. It is not yet possible to transplant the nuclei
from such cells. This is partly because most differentiated cells divide
only very rarely, but this difficulty can perhaps be overcome by taking
nuclei from regenerating tissue. It is also because no artificial medium
has been found which is not lethal to animal nuclei. Nuclear transplantation is being used to try and develop a medium which is less lethal
to living nuclei, and this would enormously facilitate the transplantation
of nuclei from adult cells and cells in culture, as well as work on isolated
nuclei in general. Together with other experimental approaches, the
transplantation of living cell nuclei can be expected to continue its
contribution to our understanding of the control of gene activity.
Acknowledgements
The author is most grateful to Dr. E. J. DuPraw for permission to
quote some of his unpublished work, and to Dr. J. F. Wilson for showing
him the manuscript of a paper before its publication. Mr. C. F. Graham
has very kindly allowed some of his unpublished work to be included in
this paper and has provided helpful comments on it. The author gratefully acknowledges that some of his work reported in this paper was
supported by a research grant from the Medical Research Council.
References
Allfrey, V. G., Littau, V.C. and Mirsky, A. E. (1963). Proc. nat. Acad. Set., Wash.
49, 414.
Astaurov, B. L. and Ostriakova-Varshaver, V. P. (1957). J. Embryol. exp. Morph.
5, 449.
Beale, G. H. (1954). 'The Genetics of Paramecium aurelia\ Cambridge Monographs
in Experimental Biology, Vol. 2. Cambridge,
Becker, H. J. (1959). Chromoeoma 10, 654.