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    Visualization of the Nucleolus in Living Cells with Cell-Penetrating Fluorescent Peptides
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    Compartmentalization (fire protection)
    Immunofluorescence
    Compartment (ship)
    Organelle
    We analyzed the connection of changes in nucleus ploidy with changes in nucleolar apparatus of NIH 3T3 cells. The quantity of nucleoli does not depend on the quantity of nucleolar DNA, but instead depends on euploidy: the majority of euploid cells have 1-3 nucleoli. The quantity of DNA in the nucleolus is correlated with the quantity of nucleolar DNA, and does not depend on ploidy changes. The nucleolar area has a tendency to increase in line with an increase in their numbers in the nucleus. The relationship of the quantity of DNA in the nucleolus with that of the nucleus is stable. During the process of increase in the number of nucleoli in a nucleus, there is a corresponding decrease in the quantity of DNA in each nucleolus, and there is likewise no increase in the sum of nucleolar DNA. The ratio of sums of the nucleolar perimeters to nuclear perimeter is a significant factor, which increases linearly along with an increase in the number of nucleoli in a nucleus.
    Nuclear DNA
    Abstract As organisms develop, their tissues can become separated into distinct cell populations through the establishment of compartment boundaries. Compartment boundaries have been discovered in a wide variety of tissues, but in many cases the molecular mechanisms that separate cells remain poorly understood. In the Drosophila wing, a stripe of Notch activation maintains the dorsal‐ventral compartment boundary, through a process that depends on the actin cytoskeleton. Here, we show that the dorsal‐ventral boundary exhibits a distinct accumulation of Myosin II, and that this accumulation is regulated downstream of Notch signaling. Conversely, the dorsal‐ventral boundary is depleted for the Par‐3 homologue Bazooka. We further show that mutations in the Myosin heavy chain subunit encoded by zipper can impair dorsal‐ventral compartmentalization without affecting anterior‐posterior compartmentalization. These observations identify a distinct accumulation and requirement for Myosin activity in dorsal‐ventral compartmentalization, and suggest a novel mechanism in which contractile tension along an F‐actin cable at the compartment boundary contributes to compartmentalization. Developmental Dynamics 235:3051–3058, 2006. © 2006 Wiley‐Liss, Inc.
    Compartment (ship)
    Compartmentalization (fire protection)
    Citations (130)
    The appendages of Drosophila develop from the imaginal discs. During the extensive growth of these discs cell lineages are for the most part unfixed, suggesting a strong role for cell-cell interactions in controlling the final pattern of differentiation. However, during early and middle stages of development, discs are subdivided by strict lineage restrictions into a small number of spatially distinct compartments. These compartments appear to be maintained by stably inheriting states of gene expression; the compartment-specific expression of two such 'selector'-like genes, engrailed and apterous, are critical for anterior-posterior and dorso-ventral compartmentalization, respectively. Recent work suggests that one purpose of compartmentalization is to establish regions of specialized cells near compartment boundaries via intercompartmental induction, using molecules like the hedgehog protein. Thus, compartments can act as organizing centers for patterning within compartments. Evidence for non-compartmental patterning mechanisms will also be discussed.
    Compartmentalization (fire protection)
    Compartment (ship)
    Appendage
    engrailed
    Cell lineage
    Lineage (genetic)
    Cellular compartment
    Cell fate determination
    Citations (176)
    Abstract The number of the nucleoli in a CaCo‐2 cell nucleus does not generally depend on the quantity of DNA in the nucleus, but nucleolar DNA content is directly proportional to total nuclear DNA. However, in multinucleolar cells (three or more nucleoli), the nucleolar DNA content increases after 96 h incubation in culture without concomitant quantitative changes in nuclear DNA. The percentage of multinucleolar cells and the average number of nucleoli per nucleus increase with increasing incubation time. After 72 and 96 h in culture, multinucleolar cells show distinctive morphologies. The ratio of the sum of nucleolar perimeters to the nuclear perimeter increases linearly when the number of nucleoli in a nucleus increases, but there is no concomitant increase in total nucleolar area or DNA content, except in the 72 and 96 h populations. When the number of nucleoli in CaCo‐2 cells increases after 48 and 60 h in culture, the amount of DNA per nucleolus decreases.
    Nuclear DNA