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Query: UMLS:C0276640 (TEM)
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Experiments using monoclonal and polyclonal anti-actin antibodies allowed us to demonstrate the presence of F- or G-actin in original protists, dinoflagellates, either by biochemistry, immunofluorescence and in TEM. SDS-PAGE electrophoresis and immunoblottings made either from total or nuclear protein extracts revealed the presence of a 44-kDa band reacting with monoclonal anti-actin antibody in two species, Prorocentrum micans and Crypthecodinium cohnii, and thus demonstrated the presence of actin in nuclear and cytoplasmic fractions. After squash preparation of P micans cells, actin was identified within the nucleus and in some regions of the cytoplasm by immunofluorescence microscopy. Labelling of both the nucleolus and the centrosome region was evident together with amorphous nucleoplasmic material surrounding the chromosomes. The use of cryosections of intact P micans and C cohnii cells for immunofluorescence along with staining with DAPI to delineate the chromosomes themselves, yielded finer resolution of the intranuclear network labelling pattern and allowed us to complete our observations, in particular on the cytoplasmic labelling. In P micans, in addition to the centrosome region, the cytoplasmic channels passing through the nucleus in dividing cells are labelled. In C cohnii, the cortex, the centrosome region, the cytoplasmic channels, the region surrounding the nucleus, the filaments linking it to the cortex and the cleavage furrow are also labelled. In the nucleus of the two species, there is a prominent "weft' of fine actin filaments in the nucleoplasm forming a matrix of varying density around the persistent chromosomes. This actin matrix, of unknown function, is most conspicuous at the end of the S-phase of the cell cycle. Fluorescent derivatives of phalloidin, used as diagnostic cytochemical probes for polymeric actin (F-actin), gave similar results. Positive TEM immunolabelling of intranuclear actin confirms its presence in the nucleoplasm, in the nucleolus where the preribosomal region is labelled while C cohnii chromosomes are unlabelled and the P micans chromosomes very slightly. In the cytoplasm, lips of the cleavage furrow and kinetosome regions are labelled as well as the centrosome region. The possible functions of this protein located in several compartments of dinoflagellate cells are discussed.
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PMID:Nuclear and cytoplasmic actin in dinoflagellates. 900 84

Luminescent semiconductor quantum dots (QDs) are a new class of fluorescent label with wide-ranging applications for cell imaging. The electron density and elemental composition of these materials permit the extension of their use as probes in conventional electron microscopy (TEM) and energy-filtered TEM (EFTEM). Here we illustrate the feasibility of using streptavidin-conjugated QDs as TEM tags by labeling a nuclear protein on cell sections and obtaining correlative fluorescence and TEM data. We also show that QD probes can be employed in conjunction with immunogold for co-localization of proteins at the ultrastructural level. Furthermore, by obtaining cadmium elemental maps of CdSe/ZnS QDs distributed on a nuclear structure, we demonstrate the potential of QDs for co-localization of multiple proteins when used in combination with EFTEM.
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PMID:Application of quantum dots as probes for correlative fluorescence, conventional, and energy-filtered transmission electron microscopy. 1468 13

Although the formation and maintenance of epithelial tubes are essential for the viability of multicellular organisms, our understanding of the molecular and cellular events coordinating tubulogenesis is relatively limited. Here, we focus on the activities of Ribbon, a novel BTB-domain containing nuclear protein, in the elongation of two epithelial tubes: the Drosophila salivary gland and trachea. We show that Ribbon interacts with Lola Like, another BTB-domain containing protein required for robust nuclear localization of Ribbon, to upregulate crumbs expression and downregulate Moesin activity. Our ultrastructural analysis of ribbon null salivary glands by TEM reveals a diminished pool of subapical vesicles and an increase in microvillar structure, cellular changes consistent with the known role of Crumbs in apical membrane generation and of Moesin in the cross-linking of the apical membrane to the subapical cytoskeleton. Furthermore, the subapical localization of Rab11, a small GTPase associated with apical membrane delivery and rearrangement, is significantly diminished in ribbon mutant salivary glands and tracheae. These findings suggest that Ribbon and Lola Like function as a novel transcriptional cassette coordinating molecular changes at the apical membrane of epithelial cells to facilitate tube elongation.
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PMID:Ribbon modulates apical membrane during tube elongation through Crumbs and Moesin. 1858