convincingly prove the role of nucleus for determination of characteristic
features of the cell or definite individual.
The investigations of Hämmerling are of great importance for
elucidating the nuclear-cytoplasmic interrelations. Acetabularia is a huge
unicellular plant, 3—5 cm in length. It possesses only one nucleus located
in the base of the pedicel, called rhisoid. The two Acetabularia species —
A. mediterranea and A. crenulata — differ morphologically in the umbels
formed on the top. The nucleus can separate from the cell by cutting off the
rhisoid, where it is located, and then can be implanted to another cell
cytoplasm. And always the nucleus of donor cell determines the shape of
umbel (Fig. 3–6).
Experiments with taking away and implanting of nuclei are carried out
with the filamentous green alga Spyrogyra, sea urchin eggs (Arbacia),
infusoria (Stentor), mollusca (Triton), etc. Some time enucleated cells have
continued to develop. That is the reason Harris (1973) to state that
“matrices for synthesis of specific proteins are kept in the protoplasm long
time after separating the nucleus, and the mechanisms controlling this
synthesis continue to function in it”.
The removal of the nucleus from the cell leads to serious disturbances
of its life processes and functions followed by its death. What is the exact
character of the alterations occurring in it as a result of enucliation is still
unclear. Undoubtedly they have a complex character. Most probably at
their root is the interrupted synthesis of RNA, ribosomes and proteins.
Naturally, enucleation does not influence equally on the synthetic
processes in different cells. In this respect a certain role is played by the
cytoplasm, closely connected with the nucleus in a united nuclear-
cytoplasmic complex. For that reason, in different cells these processes
fade away with different duration. In some cases that can occur only for
hours, while amoebae continue to live up to 2—3 weeks, and enucleated
fragments of Acetabularia — up to 2—3 months.