[Fibrillar actin in the nuclear apparatus of the ciliate Paramecium caudatum].

Due to their nuclear dualism, ciliates provide a good model for studying the role of actin in spatial organization and transcription activity of the nucleus. The actin in the nuclear apparatus of the ciliate Paramecium caudatum was studied using fluorescently labeled phalloiodin and indirect immunocytochemistry. Fibrillar actin was demonstrated in both of the nuclei.

[The route of a bacterium Holospora in the cell of Paramecium (Ciliophora, Protista) from phagosome to the nucleus].

Problems encountered at the initial stages of stable symbiotic system formation are discussed in the review. The most studied models for interaction between pathogenic bacteria and metazoan cells are compared with a similar system including Paramecium (a ciliatte)--Holospora (a bacterium). Literary and our own data on the infection of P.

[The specificity of silver nitrate staining of nucleolar organizers].

The technique of silver staining of the active nucleolar organizer regions is discussed. The specificity of the technique, the mechanism of the reaction, the nature and possible functions of argyrophilic protein(s) are considered. Special attention is paid to the fact, ascertained elsewhere, that the silver deposits in the nucleolus are related to the structure of "activated" (potentially active) ribosomal chromatin, rather than to the process of transcription itself.

[Correlation of the nucleolar organizer and the fibrillar center of the nucleolus].

The review is dedicated to the question, to what extent it is possible to speak about the correspondence of the fibrillar center (FC) of the nucleolus to the nucleolar organizer region (NOR) of the metaphase chromosome. The analysis of the literature on the problem provides grounds for the affirmation that the chromatin-containing elements of the FC and of the fibrillar component of the nucleolus correspond to the NOR. At the same time, the number of facts evidence in favour of the hypothesis that the FC serves as a kind of "depot" for nucleolar proteins.