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  • 1
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Dynamic cell cycle analysis is based on the incorporation of labelled precursors into DNA. Although antibodies to BrdU are very useful for analysing in flow cells which synthesize DNA, this approach has two main limitations. First, the detection of low incorporating cells is often difficult; second, four parameter flow cytometry is not able to correlate cell cycle to any other cellular marker. We have developed a methodology that, employing an IgGH+L as a second antibody and side scatter instead of propidium iodide fluorescence, allows a better discrimination of BudR+ cells. This approach allows the collection of an extra-fluorescent signal, and the analysis of specific cellular markers within the cell cycle.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The nuclear matrix was prepared in situ from Swiss 3T3 cells, which were synchronized by contact inhibition and serum starvation and pulse-labelled for very short periods of time with 5-bromodeoxyuridine (5-BrdU). For the first time 5-BrdU has been employed to demonstrate the association of newly synthesized DNA with a nucleoskeleton. Immunofluorescence analysis using a monoclonal antibody to 5-BrdU revealed five different intranuclear staining patterns at different stages of the S phase. These patterns were observed also in intact cells and did not change during the matrix preparation steps which involve extraction with 2M NaCl and DNase I digestion. Such an observation was also confirmed by spatial confocal microscopy studies. The intensity of lfuorescence, which was evaluated by cytofluorometry, increased to reach a maximum during mid-S phase and then decreased. Because no significant difference was found in the time to label residual DNA of different 5-BrdU staining patterns, this strongly suggests that a different number of replicons is activated at different stages of the S phase. These results strengthen the hypothesis that eukaryotic DNA replication occurs in close association with an insoluble protein nuclear skeleton, which determines the three-dimensional spatial organization of chromosome duplication.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Using both conventional fluorescence and confocal laser scanning microscopy we have investigated wheter or not stabilization of isolated human erythroleukemic nuclei with sodium tetrathionate can maintain in the nuclear matrix the same spatial distribution of three polypeptides (Mr 160 kDa and 125 kDa, previously shown to be components of the internal nuclear matrix plus the 180-kDa nucleolar isoform of DNA topoisomerase II) as seen in permeabilized cells. The incubation of isolated nuclei in the presence of 2 mM sodium tetrathionate was performed at 0° C or 37° C. The matrix fraction retained 20–40% of nuclear protein, depending on the temperature at which the chemical stabilization was executed. Western blot analysis revealed that the proteins studied were completely retained in the high-salt resistant matrix. Indirect immunofluorescence experiments showed that the distribution of the three antigens in the final matrix closely resembled that detected in permeabilized cells, particularly when the stabilization was performed at 37° C. This conclusion was also strengthened by analysis of cells, isolated nuclei and the nuclear matrix by means of confocal laser scanning microscopy. We conclude that sodium tetrathionate stabilization of isolated nuclei does not alter the spatial distribution of some nuclear matrix proteins.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The complex pathway which links the agonist-cell membrane receptor binding to the response at the genome level involves, among other elements, protein kinase C (PKC). Agonists acting at the cell membrane can affect an autonomous nuclear polyphosphoinositide signaling system inducing an activation of nuclear phosphoinositidase activity and a subsequent translocation of PKC to the nuclear region. The fine localization of PKC has been investigated by means of electron microscopy quantitative immunogold labeling in 3T3 mouse fibroblasts, mitogenically stimulated by IGF-I. The enzyme, which in untreated cells is present in the cytoplasm, except for the organelles, and in the nucleoplasm, after IGF-I treatment is reduced in the cytoplasm and almost doubled in the nucleus. The PKC isoform translocated to the nucleus is the α isozyme, which is found not only associated with the nuclear envelope but mainly with the interchromatin domains. By using in situ matrix preparations, PKC appears to be retained at the nuclear matrix level, both at the nuclear lamina and at the inner nuclear matrix, suggesting a direct involvement in the phosphorylation of nuclear proteins which are responsible for the regulation of DNA replication.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0263-6484
    Keywords: Inositol lipids ; differentiation ; nucleus ; Friend erythroleukemia cells ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The incorporation of 32Pi into phospholipids was studied in Friend erythroleukemia cells either induced or not to erythroid differentiation with 4 mM hexamethylenebisacetamide (HMBA). The effect of the differentiating agent on the recovery of radiolabelled phospholipids was compared in whole cells, isolated nuclei and nuclear matrix after in vivo labelling for 1 hr. The procedure employed for the isolation of nuclei was demonstrated to allow only negligible lipid redistribution caused by cell manipulations. Among the lipids extractable from nuclei, acidic phospholipids, and particularly polyphosphoinositides, were more represented than in whole cells, while small differences were found in the other phospholipid classes examined. The comparison between the uninduced and induced condition showed that the relative amounts of nuclear inositol lipids were modified by HMBA treatment of the cells, with a decreased recovery of phosphatidylinositol 4,5 bisphosphate.These results indicate that phosphatidylinositol and its phosphorylation products synthesized in vivo show a different metabolism in nuclei and whole cells. They appear to be tightly bound nuclear components, also present in membrane-deprived nuclei and nuclear matrix, and are probably related to the nuclear events involved in erythroid differentiation.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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