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Quarterly Journal of Microscopical Science, Vol s3-94, 461-480, Copyright © 1953 by Company of Biologists

Nuclear Transplantation in Amoebae. II

The immediate results of transfer of nuclei between Amoeba Proteus and Amoeba Discoides

I. J. LORCH 1 and J.F DANIELLI 1

1 Zoology Department, King's College, London, W.

1. A description is given of a method for replacing the original nucleus of an amoeba by a nucleus from another amoeba. This method has been used to study transfers of nuclei within a species (homotransfers) and between species (heterotransfers). The species used were A. proteus and A. discoides.

2. Removal of the nucleus from an amoeba inactivates the animal, so that movement is sporadic and unco-ordinated, digestion ineffective, and death results after 10-20 days.

3. Renucleation results in reactivation with both homo- and heterotransfers. Reactivated homotransfers normally are able to divide and form mass cultures. Heterotransfers are less often able to divide and very seldom form mass cultures.

4. Amoebae taken at random from a mass culture divide after an interval which appears to be composed of a lag tl in which the processes leading to division are inactive, followed by an interdivision period td during which preparation for division is active. Experiments are given showing the effect of nuclear transfer on tl and td.

5. After heterotransfer nuclei of either species may grow and divide in foreign cytoplasm. Before the first division after heterotransfer a cytoplasmic effect on nuclear size is observable, and after the first division the cytoplasm has a dominant effect in determining nuclear diameter.

6. When curves are plotted of the frequency of occurrence of nuclei of various diameters in pure cultures, maxima are found in the curves characteristic of the species. After nuclear transfer the cytoplasm and nucleus both have a strong influence in determining the position of the maxima.

7. Studies of the form assumed by heterotransfers show that, although there is a measurable influence of the nucleus on the form soon after transfer, this influence disappears almost entirely in 6-12 days, after which the determination of form is almost entirely cytoplasmic.

8. The results given under points 4, 5, 6, and 7 are based on the study of animals immediately after transfer and for the subsequent two divisions only. Longer-term effects will be discussed in another paper.






© The Company of Biologists Ltd 1953