[Comparison of the nuclear alterations induced by actinomysin D and alpha-amantine in hapatocytes of the rat (author's transl)].

Comparing the morphological effects of actinomycin D and alpha amanitine on the rat liver, it can be seen that the nuclear alterations caused by actinomycin (=segregation of the nucleolus and condensation of all the chromatin) occur simultaneously. After treatment with amanitine, the lesions appear in two steps. First of all one sees condensation of only the extranucleolar chromatin and fragmentation of the nucleolus. These two phenomena are related to each other not only chronogically but also causetively. In our opinion the shrinkage of the extranucleolar parts of chromosones results in the individual nucleolus-organizers being removed into different quarters of the nucleoplasm. The fragments themselves must not be altered structurally and functionally, as Kedinger and Simard (1974) have already shown. We always observed changes of the nucleolar fragments 30-90 min after the fragmentation. These changes consisted of the condensation of the intranucleolar chromatin, and the segregation and degranulation of the nucleolus, in the same manner found directly after the actinomycin-poisoning in the whole nucleolus. The delay of the lesions observed on the dispersed nucleolar fragments indicates that is a consequence of the amanitine-poisoning -- probably the result of the disturbed protein synthesis and the inactivation of a hypothetical extranucleolar regulatorgene, which controls nucleolar function.