RESUMEN

The features of structural and functional organization of the main nuclear compartments and distribution of their key molecular components (chromatin-remodeling protein ATRX, RNA polymerase I and II, and the splicing factor SC35) has been studied in the nuclei of mammary gland cells at different functional states. No significant differences between the nuclei of the cells in the lactating and non-lactating mammary glands have been revealed at the ultrastructural level. At the same time, photometric analysis has revealed higher intensity of nucleoplasmic immunofluorescent staining of mammary glands in the lactating animals when antibodies against the proteins ATRX and SC35 were used. Apparently, this observation reflects the changes of the structural and functional status of chromatin as well as the redistribution of splicing factors between the sites of their deposition and transcription.

Asunto(s)

RESUMEN

In the present work we studied the distribution of YB-1 in the nuclei of mouse hepatocytes, early embryos and human skin fibroblasts with the use of light and electron microscopy. To reveal YB-1, we applied rat polyclonal antibody against the C-terminal fragment of YB-1 molecule and rabbit polyclonal antibody against full-length YB-1 molecule. YB-1 distribution patterns varied significantly in different cell types. YB-1 was found to be colocalized with RNA polymerase I in mouse hepatocytes and embryos. Besides, YB-1 was revealed in a population of Cajal bodies in 2-cell mouse embryos but not in other cells studied.

Asunto(s)

Asunto(s)

RESUMEN

An oocyte nucleus contains different extrachromosomal nuclear domains collectively called nuclear bodies (NBs). In the present work we revealed, using immunogold labeling electron microscopy, some marker components of interchromatin granule clusters (IGCs) and Cajal bodies (CBs) in morphologically heterogeneous oocyte NBs studied in three hemipteran species: Notostira elongata, Capsodes gothicus (Miridae) and Velia caprai (Veliidae). Both IGC and CB counterparts were revealed in oocyte nuclei of the studied species but morphological and biochemical criteria were found to be not sufficient to determine carefully the define type of oocyte NBs. We found that the molecular markers of the CBs (coilin and non-phosphorylated RNA polymerase II) and IGCs (SC35 protein) may be localized in the same NB. Anti-SC35 antibody may decorate not only a granular material representing "true" interchromatin granules but also masks some fibrillar parts of complex NBs. Our first observations on the hemipteran oocyte NBs confirm the high complexity and heterogeneity of insect oocyte IGCs and CBs in comparison with those in mammalian somatic cells and amphibian oocytes.

Asunto(s)

RESUMEN

The embryos from many outbred and inbred strains of mice are arrested at the late 2-cell stage when cultured in vitro in simple culture media. This phenomenon is referred to as the "2-cell block in vitro". The ultrastructural morphology of the nuclei of the blocked embryos is not yet well described. In the present paper we documented the results of a comparative study on the nuclei of mouse embryos, both normally developing and arrested at the 2-cell stage. The blocked embryos maintain the morphological integrity of their nuclei. Main nuclear domains (nucleolus precursor bodies, interchromatin granule clusters, perichromatin granules, and perichromatin fibrils), typical for the control embryos, are observed in the blocked ones. A number and morphological characteristics of these nuclear substructures are not changed significantly in the blocked embryos. At the same time, RNA polymerase II and pre-mRNA splicing factors are redistributed in the nucleus of the blocked embryos. Although something goes to show that nuclear organization of the blocked embryos differ from that of the control, we could not reveal in the blocked embryos distinct signs of degeneration which might characterize aged or dying cells. Our data confirm a peculiar functional state of the 2-cell blocked embryos.

Asunto(s)

RESUMEN

In oocyte nuclei of the scorpionfly, Panorpa communis, we have recently defined a population of nuclear bodies (NBs) that contain some components of Cajal bodies (CBs). In the present study, we used several criteria [presence of coilin, U7 snRNA, RNA polymerase II (pol II) and specific ultrastructure] to identify these NBs as CBs. The essential evidence for CB identification came from experiments with microinjection of fluorescein-tagged U7 snRNA. Consistent with the U7 data, we found pol II and pre-mRNA splicing factor, SC35, in Panorpa oocyte CBs. We show here that the dynamics of CBs differs from that in somatic cells and correlates with the level of oocyte chromosome condensation. We also found that the significant increase of CB size is accompanied by condensation of the chromosomes in the karyosphere, which is indicative of a decline in transcription. Using immunogold microscopy we determined that pol II and coilin are shared by CBs and the granular material associated with condensed chromosomes in the Panorpa karyosphere. The colocalization of pol II, U7 snRNA and splicing factors with CBs at the inactive stage of late oogenesis suggests that the latter may serve as storage domains for components that were earlier engaged in RNA transcription and processing.

Asunto(s)