scholarly journals Ultrastructure of mitosis in the cowpea rust fungus Uromyces phaseoli var. Vignae.

1976 ◽  
Vol 70 (3) ◽  
pp. 592-607 ◽  
Author(s):  
I B Heath ◽  
M C Heath
Keyword(s):  
Nuclear Envelope ◽  
Interphase Nucleus ◽  
Rust Fungus ◽  
Metaphase Plate ◽  
Metaphase Chromosomes ◽  
Central Bundle ◽  
Late Telophase ◽  
Uromyces Phaseoli ◽  
Cytoplasmic Microtubules

Aspects of the ultrastructure of mitotic nuclei of the fungus Uromyces phaseoli var. vignae are described from both intercellular hyphae in the cowpea host and infection structures induced to differentiate in vitro. The interphase nucleus-associated organelle (NAO) consists of two trilamellar acircular disks connceted by an osmiophilic bar. The intranuclear spindle develops between these disks when they separate. The spindle contains pole to pole, interdigitating, chromosomal, and fragmentary microtubules arranged to form a central bundle along the surface of which lie the metaphase chromosomes. No metaphase plate is found. There are up to three microtubules per kinetochore and approximately 14 chromosomes on the haploid spindle. Telophase elongation appears to involve extension of pole to pole microtubules with no evidence for the remaining presence of interdigitating microtubules. Concomitantly, numerous cytoplasmic microtubules develop from each NAO disk where few or none are present in other phases. Reformation of the interphase NAO involves the formation of a sausage-shaped intermediate at late telophase. The nuclear envelope remains intact and the nucleolus persists throughtout division. Various aspects of the spindle and NAOs appear to be evolutionary intermediates between Ascomycetes and higher Basidiomycetes, thus supporting the theory of Basidiomycete evolution from the former group and demonstrating an encouraging correlation between mitotic characteristics and other phylogenetic markers.

scholarly journals PROPHASING OF INTERPHASE NUCLEI AND INDUCTION OF NUCLEAR ENVELOPES AROUND METAPHASE CHROMOSOMES IN HELA AND CHINESE HAMSTER HOMO- AND HETEROKARYONS

1974 ◽  
Vol 62 (1) ◽  
pp. 104-113 ◽  
Author(s):  
Yoshitaka Obara ◽  
Lee S. Chai ◽  
Herbert Weinfeld ◽  
Avery A. Sandberg
Keyword(s):  
Nuclear Envelope ◽  
Hela Cells ◽  
Interphase Nucleus ◽  
Chinese Hamster ◽  
Binucleate Cell ◽  
Metaphase Chromosomes ◽  
Interphase Nuclei ◽  
Multinucleate Cells ◽  
Interphase Cells ◽  
Nuclear Envelope Formation

Fusing human HeLa metaphase cells with HeLa interphase cells resulted within 30 min in either of two phenomena in the resultant binucleate cell: either prophasing of the interphase nucleus or formation of a normal-appearing nuclear envelope around the metaphase chromosomes. The frequency of either occurrence was strongly dependent on environmental pH. At pH's of 6.6–8.0, prophasing predominated; at pH 8.5 nuclear envelope formation predominated. Additionally, the frequencies of the two events in multinucleate cells depended on the metaphase/interphase ratio. When the ratio was 0.33 nuclear envelope formation predominated; when it was 2.0 prophasing predominated. In their general features, the results with fused HeLa cells resembled those reported earlier with fused Chinese hamster Don cells. However, the results provided an indication that between pH 6.6 and 8.0 the HeLa metaphase cells possessed a much greater capacity than the Don metaphase cells to induce prophasing. Fusion of Don metaphase cells with HeLa interphase cells or of Don interphase cells with HeLa metaphase cells at pH 8.0 resulted in nuclear envelope formation or prophasing in each kind of heterokaryon. As in the homokaryons, the frequencies of the two events in the heterokaryons depended on the metaphase/interphase ratio. The statistics of prophasing and nuclear envelope formation in the homo- and heterokaryon populations were consistent with the notion that disruption or formation of the nuclear envelope depends on the balance attained between disruptive and formative processes.

Some Structural Features of Metaphase Chromosomes of Mice and Men

1967 ◽  
Vol 25 ◽  
pp. 190-191
Author(s):  
Godfrey C. Hoskins ◽  
Betty B. Hoskins
Keyword(s):  
Electron Microscopy ◽  
Electron Micrographs ◽  
Structural Features ◽  
Metaphase Chromosomes ◽  
The Future ◽  
Of Mice And Men ◽  
Mouse Cells ◽  
Human And Mouse

Metaphase chromosomes from human and mouse cells in vitro are isolated by micrurgy, fixed, and placed on grids for electron microscopy. Interpretations of electron micrographs by current methods indicate the following structural features.Chromosomal spindle fibrils about 200Å thick form fascicles about 600Å thick, wrapped by dense spiraling fibrils (DSF) less than 100Å thick as they near the kinomere. Such a fascicle joins the future daughter kinomere of each metaphase chromatid with those of adjacent non-homologous chromatids to either side. Thus, four fascicles (SF, 1-4) attach to each metaphase kinomere (K). It is thought that fascicles extend from the kinomere poleward, fray out to let chromosomal fibrils act as traction fibrils against polar fibrils, then regroup to join the adjacent kinomere.

Contributions to the mechanisms of mitosis and roles of cytoplasmic microtubules from ultrastructural analyses of fungi

1978 ◽  
Vol 36 (2) ◽  
pp. 266-267
Author(s):  
I. Brent Heath
Keyword(s):  
Nuclear Envelope ◽  
Direct Application ◽  
Ultrastructural Analysis ◽  
General Interest ◽  
Research Results ◽  
Organelle Motility ◽  
Cytoplasmic Microtubules

Detailed ultrastructural analysis of fungal mitotic systems and cytoplasmic microtubules might be expected to contribute to a number of areas of general interest in addition to the direct application to the organisms of study. These areas include possibly fundamental general mechanisms of mitosis; evolution of mitosis; phylogeny of organisms; mechanisms of organelle motility and positioning; characterization of cellular aspects of microtubule properties and polymerization control features. This communication is intended to outline our current research results relating to selected parts of the above questions.Mitosis in the oomycetes Saprolegnia and Thraustotheca has been described previously. These papers described simple kinetochores and showed that the kineto- chores could probably be used as markers for the poorly defined chromosomes. Kineto- chore counts from serially sectioned prophase mitotic nuclei show that kinetochore replication precedes centriole replication to yield a single hemispherical array containing approximately the 4 n number of kinetochore microtubules diverging from the centriole associated "pocket" region of the nuclear envelope (Fig. 1).

scholarly journals The centrin-based cytoskeleton of Chlamydomonas reinhardtii: distribution in interphase and mitotic cells.

1988 ◽  
Vol 107 (2) ◽  
pp. 635-641 ◽  
Author(s):  
J L Salisbury ◽  
A T Baron ◽  
M A Sanders
Keyword(s):  
Nuclear Envelope ◽  
Polyclonal Antibodies ◽  
Flagellar Apparatus ◽  
Immunogold Labeling ◽  
Basal Bodies ◽  
Flagellar Roots ◽  
Cell Biol ◽  
Immunofluorescence Studies ◽  
Descending Fibers

Monoclonal and polyclonal antibodies raised against algal centrin, a protein of algal striated flagellar roots, were used to characterize the occurrence and distribution of this protein in interphase and mitotic Chlamydomonas cells. Chlamydomonas centrin, as identified by Western immunoblot procedures, is a low molecular (20,000-Mr) acidic protein. Immunofluorescence and immunogold labeling demonstrates that centrin is a component of the distal fiber. In addition, centrin-based flagellar roots link the flagellar apparatus to the nucleus. Two major descending fibers extend from the basal bodies toward the nucleus; each descending fiber branches several times giving rise to 8-16 fimbria which surround and embrace the nucleus. Immunogold labeling indicates that these fimbria are juxtaposed to the outer nuclear envelope. Earlier studies have demonstrated that the centrin-based linkage between the flagellar apparatus and the nucleus is contractile, both in vitro and in living Chlamydomonas cells (Wright, R. L., J. Salisbury, and J. Jarvik. 1985. J. Cell Biol. 101:1903-1912; Salisbury, J. L., M. A. Sanders, and L. Harpst. 1987. J. Cell Biol. 105:1799-1805). Immunofluorescence studies show dramatic changes in distribution of the centrin-based system during mitosis that include a transient contraction at preprophase; division, separation, and re-extension during prophase; and a second transient contraction at the metaphase/anaphase boundary. These observations suggest a fundamental role for centrin in motile events during mitosis.

Identification of a 102 kDa protein (cytocentrin) immunologically related to keratin 19, which is a cytoplasmically derived component of the mitotic spindle pole

1993 ◽  
Vol 106 (3) ◽  
pp. 967-981 ◽  
Author(s):  
E.C. Paul ◽  
A. Quaroni
Keyword(s):  
Cellular Localization ◽  
Spindle Pole ◽  
Early Prophase ◽  
Mitotic Apparatus ◽  
Nuclear Envelope Breakdown ◽  
Keratin 19 ◽  
Pericentriolar Material ◽  
Late Telophase ◽  
Cytoplasmic Microtubules ◽  
Cycle Dependent

The mAb RK7, previously shown to recognize keratin 19, was also found to cross-react with a biologically unrelated 102 kDa protein, which becomes associated with the poles of the mitotic apparatus. This newly identified protein, called cytocentrin, is a stable cellular component, may be at least in part phosphorylated, and displays a cell cycle-dependent cellular localization. In interphase cells, it is diffusely distributed in the cytosol and shows no affinity for cytoplasmic microtubules. It becomes localized to the centrosome in early prophase, prior to nuclear envelope breakdown, separation of replicated centrosomes, and nucleation of mitotic apparatus microtubules. During metaphase, cytocentrin is located predominately at the mitotic poles, often appearing as an aggregate of small globular sub-components; it also associates with some polar microtubules. In late anaphase/early telophase cytocentrin dissociates entirely from the mitotic apparatus and becomes temporarily localized with microtubules in the midbody, from which it disappears by late telophase. In taxol-treated cells cytocentrin was associated with the center of the miniasters but also showed affinity for some cytoplasmic microtubules. Studies employing G2-synchronized cells and nocodazole demonstrated that cytocentrin can become associated with mitotic centrosomes independently of tubulin polymerization and that microtubules regrow from antigen-containing foci. We interpret these results to suggest that cytocentrin is a cytoplasmic protein that becomes specifically activated or modified at the onset of mitosis so that it can affiliate with the mitotic poles where it may provide a link between the pericentriolar material and other components of the mitotic apparatus.

BAF is required for emerin assembly into the reforming nuclear envelope

2001 ◽  
Vol 114 (24) ◽  
pp. 4575-4585 ◽  
Author(s):  
Tokuko Haraguchi ◽  
Takako Koujin ◽  
Miriam Segura-Totten ◽  
Kenneth K. Lee ◽  
Yosuke Matsuoka ◽  
...  
Keyword(s):  
Nuclear Envelope ◽  
Hela Cells ◽  
Core Region ◽  
Lamin B ◽  
The Core ◽  
Double Stranded Dna ◽  
Recessive Form ◽  
Nuclear Envelope Assembly

Mutations in emerin cause the X-linked recessive form of Emery-Dreifuss muscular dystrophy (EDMD). Emerin localizes at the inner membrane of the nuclear envelope (NE) during interphase, and diffuses into the ER when the NE disassembles during mitosis. We analyzed the recruitment of wildtype and mutant GFP-tagged emerin proteins during nuclear envelope assembly in living HeLa cells. During telophase, emerin accumulates briefly at the ‘core’ region of telophase chromosomes, and later distributes over the entire nuclear rim. Barrier-to-autointegration factor (BAF), a protein that binds nonspecifically to double-stranded DNA in vitro, co-localized with emerin at the ‘core’ region of chromosomes during telophase. An emerin mutant defective for binding to BAF in vitro failed to localize at the ‘core’ in vivo, and subsequently failed to localize at the reformed NE. In HeLa cells that expressed BAF mutant G25E, which did not show ‘core’ localization, the endogenous emerin proteins failed to localize at the ‘core’ region during telophase, and did not assemble into the NE during the subsequent interphase. BAF mutant G25E also dominantly dislocalized LAP2β and lamin A from the NE, but had no effect on the localization of lamin B. We conclude that BAF is required for the assembly of emerin and A-type lamins at the reforming NE during telophase, and may mediate their stability in the subsequent interphase.

Parthenogenesis and cytoskeletal organization in ageing mouse eggs

Development ◽  
1986 ◽  
Vol 95 (1) ◽  
pp. 131-145
Author(s):  
Michelle Webb ◽  
Sarah K. Howlett ◽  
Bernard Maro
Keyword(s):  
Critical Concentration ◽  
Metaphase Plate ◽  
Meiotic Spindle ◽  
Cytoskeletal Organization ◽  
Spindle Poles ◽  
Different Types ◽  
Mouse Egg ◽  
Parthenogenetic Embryos

The cytoskeletal organization of the mouse egg changes during ageing in vivo and in vitro. The earliest change observed is the disappearance of the microfilament-rich area overlying the meiotic spindle. This is followed by the migration of the spindle towards the centre of the egg. Finally the spindle breaks down and the chromosomes are no longer organized on a metaphase plate. This spindle disruption may result from changes in the microtubule nucleating material found at the spindle poles and from an increase in the critical concentration for tubulin polymerization. It is possible to correlate the changes in the cytoskeletal organization of the egg occurring during ageing with the different types of parthenogenetic embryos obtained after ethanol activation. These observations strengthen the hypothesis that the actin-rich cortical area that overlies the meiotic spindle forms a domain to which the meiotic cleavage furrow is restricted and provides some insights into the mechanisms by which different types of parthenogenetic embryos are generated.

scholarly journals Supramolecular Structures of the Dictyostelium Lamin NE81

Cells ◽  
2019 ◽  
Vol 8 (2) ◽  
pp. 162
Author(s):  
Marianne Grafe ◽  
Petros Batsios ◽  
Irene Meyer ◽  
Daria Lisin ◽  
Otto Baumann ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Nuclear Envelope ◽  
Model Organism ◽  
Super Resolution ◽  
Nuclear Lamina ◽  
Stimulated Emission ◽  
Structural Level ◽  
Animal Cells ◽  
Nuclear Lamins

Nuclear lamins are nucleus-specific intermediate filaments (IF) found at the inner nuclear membrane (INM) of the nuclear envelope (NE). Together with nuclear envelope transmembrane proteins, they form the nuclear lamina and are crucial for gene regulation and mechanical robustness of the nucleus and the whole cell. Recently, we characterized Dictyostelium NE81 as an evolutionarily conserved lamin-like protein, both on the sequence and functional level. Here, we show on the structural level that the Dictyostelium NE81 is also capable of assembling into filaments, just as metazoan lamin filament assemblies. Using field-emission scanning electron microscopy, we show that NE81 expressed in Xenopous oocytes forms filamentous structures with an overall appearance highly reminiscent of Xenopus lamin B2. The in vitro assembly properties of recombinant His-tagged NE81 purified from Dictyostelium extracts are very similar to those of metazoan lamins. Super-resolution stimulated emission depletion (STED) and expansion microscopy (ExM), as well as transmission electron microscopy of negatively stained purified NE81, demonstrated its capability of forming filamentous structures under low-ionic-strength conditions. These results recommend Dictyostelium as a non-mammalian model organism with a well-characterized nuclear envelope involving all relevant protein components known in animal cells.

Nuclear envelope removal/maintenance determines the structural and functional remodelling of embryonic red blood cell nuclei in activated mouse oocytes

Zygote ◽  
1998 ◽  
Vol 6 (1) ◽  
pp. 65-73 ◽  
Author(s):  
Daniel Szöllösi ◽  
Renata Czołowska ◽  
Ewa Borsuk ◽  
Maria S. Szöllösi ◽  
Pascale Debey
Keyword(s):  
Nuclear Envelope ◽  
Transcriptional Activity ◽  
Chromatin Condensation ◽  
Oocyte Activation ◽  
Cell Nuclei ◽  
Nuclear Envelope Breakdown ◽  
Mouse Oocytes ◽  
Female Pronucleus ◽  
Mouse Fetuses

SummaryNuclei of embryonic red blood cells (e-RBC) from 12-day mouse fetuses are arrested in Go phase of the cell cycle and have low transcriptional activity. These nuclei were transferred with help of polyethylene glycol (PEG)-mediated fusion to parthenogenetically activated mouse oocytes and heterokaryons were analysed for nuclear structure and transcriptional activity. If fusion proceeded 25–45 min after oocyte activation, e-RBC nuclei were induced to nuclear envelope breakdown and partial chromatin condensation, followed by formation of nuclei structurally identical with pronuclei. These ‘pronuclei’, similar to egg (female) pronuclei, remained transcriptionally silent over several hours of in vitro culture. If fusion was performed 1 h or later (up to 7 h) after activation, the nuclear envelope of e-RBC nuclei remained intact and nuclear remodelling was less spectacular (slight chromatin decondensation, formation of nucleolus precursor bodies). These nuclei, however, reinforced polymerase-II-dependent transcription within a few hours of in vitro culture. Our present experiments, together with our previous work, demonstrate that nuclear envelope breakdown/maintenance are critical events for nuclear remodelling in activated mouse oocytes and that somatic dormant nuclei can be stimulated to renew transcription at a time when the female pronucleus remains transcriptionally silent.

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