排序方式: 共有39条查询结果,搜索用时 171 毫秒
11.
Electron Tomography of Metaphase Nucleolar Organizer Regions:
Evidence for a Twisted-Loop Organization 总被引:10,自引:1,他引:9 下载免费PDF全文
Laurent Heliot Herv Kaplan Laurent Lucas Christophe Klein Adrien Beorchia Martine Doco-Fenzy Monique Menager Marc Thiry Marie-Franoise ODonohue Dominique Ploton 《Molecular biology of the cell》1997,8(11):2199-2216
Metaphase nucleolar organizer regions (NORs), one of four types of chromosome bands, are located on human acrocentric chromosomes. They contain r-chromatin, i.e., ribosomal genes complexed with proteins such as upstream binding factor and RNA polymerase I, which are argyrophilic NOR proteins. Immunocytochemical and cytochemical labelings of these proteins were used to reveal r-chromatin in situ and to investigate its spatial organization within NORs by confocal microscopy and by electron tomography. For each labeling, confocal microscopy revealed small and large double-spotted NORs and crescent-shaped NORs. Their internal three-dimensional (3D) organization was studied by using electron tomography on specifically silver-stained NORs. The 3D reconstructions allow us to conclude that the argyrophilic NOR proteins are grouped as a fiber of 60–80 nm in diameter that constitutes either one part of a turn or two or three turns of a helix within small and large double-spotted NORs, respectively. Within crescent-shaped NORs, virtual slices reveal that the fiber constitutes several longitudinally twisted loops, grouped as two helical 250- to 300-nm coils, each centered on a nonargyrophilic axis of condensed chromatin. We propose a model of the 3D organization of r-chromatin within elongated NORs, in which loops are twisted and bent to constitute one basic chromatid coil. 相似文献
12.
Marc Thiry Thierry Cheutin Françoise Lamaye Nicolas Thelen U. Thomas Meier Marie-Françoise O’Donohue Dominique Ploton 《Histochemistry and cell biology》2009,132(2):129-140
We investigated distribution of the nucleolar phosphoprotein Nopp140 within mammalian cells, using immunofluorescence confocal
microscopy and immunoelectron microscopy. During interphase, three-dimensional image reconstructions of confocal sections
revealed that nucleolar labelling appeared as several tiny spheres organized in necklaces. Moreover, after an immunogold labelling
procedure, gold particles were detected not only over the dense fibrillar component but also over the fibrillar centres of
nucleoli in untreated and actinomycin D-treated cells. Labelling was also consistently present in Cajal bodies. After pulse-chase
experiments with BrUTP, colocalization was more prominent after a 10- to 15-min chase than after a 5-min chase. During mitosis,
confocal analysis indicated that Nopp140 organization was lost. The protein dispersed between and around the chromosomes in
prophase. From prometaphase to telophase, it was also detected in numerous cytoplasmic nucleolus-derived foci. During telophase,
it reappeared in the reforming nucleoli of daughter nuclei. This strongly suggests that Nopp140 could be a component implicated
in the early steps of pre-rRNA processing. 相似文献
13.
Tchelidze P Sauvage C Bonnet N Kilian L Beorchia A O'Donohue MF Ploton D Kaplan H 《Journal of structural biology》2006,156(3):421-431
Electron tomography of immunolabelled proteins identified with amplified nanogold particles imaged by Scanning and Transmission Electron Microscopy within thick sections is a powerful method to investigate the three-dimensional organization of complex cellular machineries. In order to increase the overall quality of the reconstructed cube, we have developed two methods that improve the tomographic reconstruction process. We first performed a very precise alignment of the projections before reconstruction with a technique using sinograms. After reconstruction, we propose to compute image restoration by calculating the Point Spread Function of the projection/back-projection system and to use it to deblur the reconstructed cubes. Improvement in the quality of the reconstructed cubes is demonstrated on images of nucleolar proteins tagged with EGFP and immunolabelled with nanogold particles. 相似文献
14.
Nuclear transport as an ultimate step of multidrug resistance 总被引:2,自引:0,他引:2
Adriamycin (ADM) incorporation into nuclei of whole multidrug resistant (MDR) CEM cells is lower than into sensitive ones (S), that is mostly thought to be the consequence of a decrease of drug related to the activity of the multidrug resistance plasma membrane protein P 170. Isolated nuclei of the lymphoblastic tumor cell line CEM, which structures were controlled by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and confocal microscopy, where incubated with 10(-6) mole/l of ADM. Incorporation into DNA was quantified by spectrofluorimetry. It was lower and slower into MDR nuclei than into S ones. Different modulators of active transport influence drug transfer into S nuclei and had no effect in MDR nuclei. The nuclear transfer into S nuclei appeared divided into two components: one was decreased by WGA, increased by cytosolic factors and an other part was purely passive in an identical intensity to MDR nuclei. Resistance of MDR nuclei seemed indebt to a defect, in these cells, of factors that mediate and/or activate nuclear transport of drug. 相似文献
15.
16.
E Puchelle A Beorchia M Ménager J M Zahm D Ploton 《Biology of the cell / under the auspices of the European Cell Biology Organization》1991,72(1-2):159-166
Using the frog palate as a representative model of human mucociliary epithelium, we analyzed, after quick freezing fixation, the three-dimensional (3-D) respiratory mucus secretory release with high voltage (200-300 kV) transmission electron microscopy (TEM). The 3-D vision of the mucus release from the secretory cells was obtained as stereo-pairs and "bas-relief" images after analysis of stereo-pairs using an image analyzer. After standard glutaraldehyde fixation, the secretory cells showed a typical goblet shape with secretory granules heterogeneous in size and electron-density which often fuse together. On the other hand, quick-frozen secretory cells exhibited a columnar shape and their membrane-bound secretory granules contained a homogeneously dark matrix. The expanded gel mucus layer was preserved and its depth never exceeded 2 microns. When the epithelium was immersed in culture medium in presence of cholinergic agonist, a marked discharge of mucus was observed and the granules swelled at the apex of the secretory cell before being discharged in the lumen. In native cryofixed epithelium, the secretory granules exhibited a marked deformability during the process of their extrusion from the secretory cell. Clusters of secretory granules surrounded by cytoplasmic material were observed in the extracellular lumen, suggesting an apocrine-type secretion. These observations indicate that rapid cryofixation and 3-D stereoscopic imaging enable a unique opportunity to analyze, without artifact, the mucous secretory process. We speculate that, apart from the classical merocrine-type secretion mechanism, the respiratory mucus may be released, at least partly by an apocrine-type secretion. 相似文献
17.
Nucleolar cycle in Physarum polycephalum was studied using EDTA preferential stain for RNP. We have been able to establish the following.
- 1. 1. The nucleolar remnants that are observed during mitosis correspond to the fibrillar zones of the interphase nucleolus.
- 2. 2. In prometaphase and metaphase the nucleolar remnants lie peripherically around the chromosomal mass with which they are only superficially associated.
- 3. 3. Preribosomal granules appear 10–15 min after metaphase in the prenucleolar bodies.
18.
Rusciani A Duca L Sartelet H Chatron-Colliet A Bobichon H Ploton D Le Naour R Blaise S Martiny L Debelle L 《PloS one》2010,5(11):e14010
The sialidase activity of neuraminidase-1 (Neu-1) is responsible for ERK 1/2 pathway activation following binding of elastin peptide on the elastin receptor complex. In this work, we demonstrate that the receptor and lipid rafts colocalize at the plasma membrane. We also show that the disruption of these microdomains as well as their depletion in glycolipids blocks the receptor signaling. Following elastin peptide treatment, the cellular GM(3) level decreases while lactosylceramide (LacCer) content increases consistently with a GM(3)/LacCer conversion. The use of lactose or Neu-1 siRNA blocks this process suggesting that the elastin receptor complex is responsible for this lipid conversion. Flow cytometry analysis confirms this elastin peptide-driven LacCer generation. Further, the use of a monoclonal anti-GM(3) blocking antibody shows that GM(3) is required for signaling. In conclusion, our data strongly suggest that Neu-1-dependent GM(3)/LacCer conversion is the key event leading to signaling by the elastin receptor complex. As a consequence, we propose that LacCer is an early messenger for this receptor. 相似文献
19.
Although rRNA synthesis, maturation, and assembly into preribosomal particles occur within the nucleolus, the route taken by pre-rRNAs from their synthetic sites toward the cytoplasm remains largely unexplored. Here, we employed a nondestructive method for the incorporation of BrUTP into the RNA of living cells. By using pulse-chase experiments, three-dimensional image reconstructions of confocal optical sections, and electron microscopy analysis of ultrathin sections, we were able to describe topological and spatial dynamics of rRNAs within the nucleolus. We identified the precise location and the volumic organization of four typical subdomains, in which rRNAs are successively moving towards the nucleolar periphery during their synthesis and processing steps. The incorporation of BrUTP takes place simultaneously within several tiny spheres, centered on the fibrillar centers. Then, the structures containing the newly synthesized RNAs enlarge and appear as compact ringlets disposed around the fibrillar centers. Later, they form hollow spheres surrounding the latter components and begin to fuse together. Finally, these structures widen and form large rings reaching the limits of the nucleoli. These results clearly show that the transport of pre-rRNAs within the nucleolus does not occur randomly, but appears as a radial flow starting from the fibrillar centers that form concentric rings, which finally fuse together as they progress toward the nucleolar periphery. 相似文献
20.
Elodie Blanchard Philippe Birnbaum Thomas Ibanez Thomas Boutreux Cécile Antin Pierre Ploton Grégoire Vincent Robin Pouteau Hervé Vandrot Vanessa Hequet Nicolas Barbier Vincent Droissart Bonaventure Sonké Nicolas Texier Narcisse Guy Kamdem Donatien Zebaze Moses Libalah Pierre Couteron 《Trees - Structure and Function》2016,30(6):1953-1968