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  • 1
    ISSN: 1615-6102
    Keywords: Calmodulin ; Cell plate ; Centrin ; Confocal microscopy ; Immunochemistry ; Mitosis ; Plants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Centrin and calmodulin are members of the EF-hand calcium-binding superfamily of proteins. In this study we compared localisation and immunoblotting of centrin with calmodulin in several monocot (onion and wheat) and dicot (mung bean andArabidopsis) plants. We confirmed that an anti-calmodulin antibody recognised a 17 kDa protein in all species tested and localises to the cytoplasm, mitotic matrix and with microtubules of the preprophase band and phragmoplast. In contrast, immunoblotting using anti-centrin antibodies shows that plant centrins vary from 17 to 20 kDa. Immunofluorescence microscopy with anti-centrin antibodies revealed only weak centrin immunoreactivity in the cytoplasm, nucleus, nuclear envelope, phragmoplast and mitotic matrix in meristematic cells. There was a slightly more intense perinuclear labelling in large differentiating onion cells and between separating anaphase chromosomes. While centrin is known to localise to the mitotic spindle poles in animal and algal cells, there was no appreciable immunoreactivity at the spindle poles in higher plants. In contrast, there was an intense immunofluorescence signal with anti-centrin antibodies in the developing cell plate. Further characterisation of the cell plate labelling by immunogold electron microscopy shows centrin immunoreactivity was closely associated with vesicles in the cell plate. Our observations suggest that centrin may play a role in cell plate formation.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1615-6102
    Keywords: Flagellar apparatus ; Green algae ; Rhizoplast ; Rootlets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ultrastructure of the flagellar apparatus of the marine quadriflagellate green algaTetraselmis subcordiformis is described in detail. Special consideration is given to the functional significance of the contractile rhizoplast and also to a complex structure which anchors the flagellar apparatus to the cell membrane and theca. The flagellar apparatus lies at the base of a deep apical depression. Four basal bodies lie in a zigzag row with their long axes nearly parallel. Outer adjacent pairs of basal bodies are structurally linked by a Z-shaped, ribbon-like structure. A striated fiber (transfiber) connects each outer basal body with the inner basal body of the opposite, mirror image pair. A complex system of four laminated oval discs (rhizanchora), microtubule rootlets and fibrous material anchor the flagellar apparatus and rhizoplasts to the plasma membrane and theca. A 4-2-4-2 arrangement of microtubule rootlets is present. Rhizoplasts, which are contractile organelles, branch into five distinct arms and associate with the near outer basal body and each of the four rhizanchora. Rhizoplast contraction is thought to be linked to flagellar activity and may act to alter the direction of motion of the cell.
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  • 3
    ISSN: 1615-6102
    Keywords: Basal body connector ; Centrin ; Flagellar roots ; Immunoblotting ; Immunolocalisation ; Phytophthora cinnamomi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Antibodies raised against the calcium-binding protein centrin, were used to identify and localise centrin containing structures in the flagellar apparatus of zoospores and cysts of the oomycetePhytophthora cinnamomi. Immunoblotting of extracts from zoospores indicates that theP. cinnamomi centrin homologue is a 20 kDa protein. Immunofluorescence microscopy with anti-centrin antibodies reveals labelling in the flagella, the basal body connector and co-localisation along the microtubular R1 root (formerly called AR3) that runs from the right side of the basal body of the anterior flagellum into the anterior of the zoospore close to the ventral surface. The centrin (R1cen) and tubulin components of the R1 root split into four loops on the right hand side of the ventral groove and rejoin along the left hand side of the groove. The R1 root continues down the left hand side of the zoospore past the basal bodies and parallel to the R4 root. We propose that at least inP. cinnamomi there is no R2 root. Immunogold labelling confirms that centrin is a component of the basal body connector complex. When the zoospores become spherical during encystment, the R1cen pivots by approximately 90 ° with respect to the nucleus.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 294 (1981), S. 163-166 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Calmodulin has been implicated in the mediation of various cellular activities thought to involve transient fluxes of Ca2* as signals4'5. In particular, CaM-Ca2+ has been shown to regulate myosin light chain kinase of smooth muscle and non-muscle cells6'10 and may be an important intermediate ...
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  • 6
    ISSN: 0886-1544
    Keywords: centrosome-associated proteins ; calcium-binding proteins ; flagellar apparatus ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Affinity-purified antibodies that recognize the 20,000-dalton molecular weight (20 kd) striated flagellar root protein of Tetraselmis striata have been used to identify antigenic homologs in other eucaryotic organisms of diverse evolutionary origins. Among the green algae, Tetraselmis and Chlamydomonas, and their colorless relative, Polytomella, the 20-kd homologs appear associated with basal bodies. This occurs most prominnently in the form of flagellar roots of both striated and microtubule subtended types. Among cultured mammalian cells (PtK2 and primary mouse macrophage cell lines), flagellar root protein homologs appear as basal feet, pericentriolar fibrils, and pericentriolar satellites. Mammalian sperm cells also show flagellar root protein homologs associated with their basal bodies. We envisage a functional role for these fibrous calcium-sensitive contractile proteins in altering the orientation of centrioles or basal bodies with their associated MTOCs by responding to topological calcium fluxes.
    Additional Material: 3 Ill.
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  • 7
    ISSN: 0886-1544
    Keywords: cell surface ; cytoskeleton ; receptor-mediated endocytosis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cell-surface IgM (antigen receptor) sediments with the membrane fraction following osmotic lysis and homogenization of cells of the human lymphoblastoid cell line WiL2. In nonreducing buffers, SDS PAGE analysis of membrane pellets demonstrates that “native” membrane IgM exists as a dimer. In contrast to osmotic lysis, lysis of cells with the nonionic detergent Triton X-100 releases approximately 90% of the membrane-bound IgM into the supernatant; approximately 10% of the IgM pellets with the cytoskeletal fraction on centrifugation. Ligand challenge with either m̈-chain-specific antibodies or concanavalin A induces a change in the state of membrane IgM making it refractory to detergent extraction, such that 43% of the IgM pellets during centrifugation. This ligand-induced retention of IgM is significantly diminished by the microfilament-disrupting agent cytochalasin D, whereas pretreatment of cells with sodium azide or colchicine results in no significant change in the percentage of membrane IgM retained by Triton X-100 residues. These results indicate that retention of IgM involves an association with the cortical actin-based cytoskeleton. Investigation of the structural basis for ligand-induced Triton X-100 retention of membrane IgM by using ferritin-conjugated antibodies, myosin subfragment S1, and stereo-imaging electron microscopy has revealed linkages between ligand-receptor (antigen-IgM) complexes and elements of the cortical actin-based cytoskeleton.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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