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  • 1
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Erythromycin inhibits the growth of wild type Paramecia and eventually kills the cells. 24 erythromycin resistant mutants (22 U.V. induced, 2 spontaneous) have been isolated. They fall into att least three phenotypic classes on the basis of their level of resistance and of thermosensitivity. Genetic analysis of three mutants shows that the resistance character is cytoplasmically inherited, as evidenced by its clonal inheritance, its transfer through cytoplasmic bridges and its non-segregation at meiosis. The results suggest that these mutants may be mitochondrial mutants analogous to those described in yeast.
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  • 2
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The genetic and physiological properties of two nuclear mutants of Parameccium tetraurelia affecting mitochondrial properties, and first screened as resistant to tetrazolium (TTC) are described. The mutant TTC 64-1 R is strongly deficient in cytochrome c and the mutant TTC 66p R is partially deficient in cytochrome aa3; both mutants display cyanide insensitive respiration in exponential growth phase. In the double mutant TTC 64-1 R -TTC 66p R /TTC 64-1 R -TTC 66p R the deficiency in cytochrome aa3 due to the TTC 64-1 R mutation is suppressed. The mutation TTC 64-1 R does not suppress cytochrome aa3 deficiencies due to mitochondrial mutations, but does interact with another nuclear mutation, cl 1, (compatible only with mitochondria deficient in cytochrome oxidase) in such a way that the double mutant TTC 64-1 R -cl 1/TTC 64-1 R -cl 1 displays a normal amount of cytochrome aa3. The possible mechanisms and physiological significance of these suppressive effects are discussed.
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  • 3
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In this study, we report cloning, by functional complementation of the KIN241 gene involved in Paramecium cell morphogenesis, cortical organization and nuclear reorganization. This gene is predicted to encode a protein of a novel type, comprising a cyclophilin-type, peptidyl-prolyl isomerase domain, an RNA recognition motif, followed by a region rich in glutamate and lysine (EK domain) and a C-terminal string of serines. As homologues of this protein are present in the genomes of Schizosaccharomyces pombe, Caenorhabditis elegans, Drosophila melanogaster, Arabidopsis thaliana and Homo sapiens, the Kin241p predicted sequence defines a new family of proteins that we propose to call ‘CRIP’, for cyclophilin–RNA interacting protein. We demonstrate that, in Paramecium, Kin241p is localized in the nucleus and that deletion of some nuclear localization signals (NLSs) decreases transport of the protein into the nucleus. No Kin241-1 protein is present in mutant cells, suggesting that the C-terminal serine-rich region is responsible for protein stability.
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  • 4
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The duplication of entire genomes has long been recognized as having great potential for evolutionary novelties, but the mechanisms underlying their resolution through gene loss are poorly understood. Here we show that in the unicellular eukaryote Paramecium tetraurelia, a ciliate, most of the ...
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  • 5
    ISSN: 0886-1544
    Keywords: monoclonal antibody ; phosphoproteins ; basal bodies ; morphogenesis ; Paramecium ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The presence of phosphorylated proteins associated with microtubule organizing centers in tissue culture cells during mitosis has been demonstrated by the use of monoclonal antibodies raised against mitotic HeLa cells [Vandre et al., Proc. Natl. Acad. Sci. U.S.A. 81:4439-4443, 1984]. We report here that in Paramecium two of the mitosis specific antibodies, MPM-1 and MPM-2, decorate throughtout the cell cycle all the microtubule organizing centers (MTOCs) located in the cortex and in the oral apparatus (gullet). Immuno-electron microscopy showed that these antibodies labeled the electron-dense material surrounding basal bodies from which several microtubule networks as well as kinetodesmal fibers originate. During mitosis, these antibodies also stained other cortical cytoskeletal structures, the kinetodesmal fibers (MPM-1 and MPM-2) and the epiplasm (MPM-1). Among the different polypeptides recognized by the antibodies on immunoblots, three major ones of 60, 63, and 116 kDa were found to be common to the cortex (where several thousand ciliary basal bodies are anchored) and the oral apparatus (which comprises several hundred basal bodies around which various arrays of cytoplasmic microtubules are organized). Alkaline phosphatase treatment abolished the immunoreactivity of the polypeptides and the labeling observed by immunofluorescence. These results demonstrate that phosphorylated proteins are associated with all the known active microtubule organizing centers present in the cortex throughout the cell cycle of Paramecium. Furthermore they indicate that in Paramecium phosphorylation of proteins could also be involved in the cell cycle dependent dynamics of cortical cytoskeletal structures other than microtubules.
    Additional Material: 10 Ill.
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  • 6
    ISSN: 0886-1544
    Keywords: actin ; microfilaments ; HMM ; phagocytosis ; cytochalasin ; Paramecium ; fluorescence microscopy ; electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Using heavy meromyosin (HMM) or the fragment S1 of myosin as probes for actin microfilaments, we studied their organization in Paramecium both by fluorescence and electron microscopy.In interphasic cells, HMM decorates (a) most prominently the periphery of nascent and young food vacuoles and their route during the early phase of their intracellular transit; (b) a thin meshwork radiating from the gullet throughout the cytoplasm; (c) a small area beneath the pore of contractile vacuoles and beneath the cytoproct when open to release food residues. Most of these HMM-decorated structures are in close contact with microtubular arrays. All HMM decoration disappears in dividing cells and in cytochalasin-treated cells. In vivo, the drug immediately blocks food vacuole formation but does not affect cytokinesis, cyclosis, contractile vacuole pulsation, defecation, or nuclear movements.The data show that, as in the cells of other organisms, actin microfilaments form defined arrays that undergo physiologically controlled cycles of assembly/disassembly. These arrays contribute (at least in the phagocytotic process) to diverse types of movement: constriction, membrane fusion, and migration of food vacuoles. However, aside from their massive concentration along the phagocytotic tractus, actin microfilaments are neither major structural components of Paramecium cytoplasm nor the only cytoskeletal components ensuring motility or contractility processes.
    Additional Material: 15 Ill.
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  • 7
    ISSN: 0886-1544
    Keywords: cytoskeleton ; cell morphogenesis ; immunofluorescence ; antimyosin monoclonal antibody ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A monoclonal antibody, CC212, raised against ciliated cortices of quail oviduct cells and characterized as an antimyosin of smooth muscle and nonmuscle cells, was shown to specifically label a regular cortical network in Paramecium and to recognize two Triton X-100-insoluble polypeptides at 130 and 50 kDa. However, no evidence was obtained that these polypeptides are related to myosin.An immunofluorescence study and ultrastructural immunogold localization allowed us to identify the CC212-decorated material as a component of the outer lattice, a submembrane cytoskeletal network which runs along the top of the ridges visible by scanning electron microscopy and delineates the periphery of each cortical unit. The dynamics of the outer lattice during the cell cycle was studied by immunofluorescence and it was found that the outer lattice growth is achieved without disruption of the preexisting meshes by longitudinal elongation and additon of new transverse partitions. A striking disorganization of the outer lattice was observed in a thermosensitive mutant primarily altered in basal body duplication. These observations suggest possible functions of the outer lattice and demonstrate the interdependence of basal body duplication, surface growth, and outer lattice remodelling.
    Additional Material: 7 Ill.
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  • 8
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A method for whole cell in situ hybridization in Paramecium was developed, which allowed us to visualize both the cytoplasmic mRNA and the transcripts in the macronucleus, and to estimate their respective variation throughout the cell cycle. Nonisotopic DNA probes, labeled with digoxigenin (DIG), were prepared by PCR from a central part of two genes of P. tetraurelia, respectively coding for a β-tubulin and the 51A surface antigen (51A-sAg). The probes were detected with an FITC-conjugated anti-DIG antibody. While no fluorescence is observed in the micronuclei, mRNA are detected in the macronucleus, as discrete spots which disappear after RNase H treatment, in the cytoplasm where they are uniformly distributed, and in the post-autogamous fragments of the old macronucleus. The intensity of the cytoplasmic labeling observed with the two probes shows a clear and different cell cycle-dependent modulation. For the β-tubulin mRNA, a peak is observed at the beginning of mitosis, while for the 51A-sAg, the peak occurs later, during cytokinesis. The macronuclear labeling, which likely reflects the transcription rate, seems roughly constant for the 51A-sAg. In contrast, for the β-tubulin genes, the intensity of the macronuclear signal shows a peak that just precedes the cytoplasmic peak.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effect of the microtubule inhibitor nocodazole was studied on Paramecium and shown to arrest cell multiplication, depolymerize the internal microtubule network, and block the development of macro- and micronuclear spindles and of the cytospindle (a cortical microtubule array assembled during division). After ultraviolet mutagenesis, three mutants resistant to nocodazole, that is capable of continued growth in the presence of the drug, were isolated and shown to correspond to three nonallelic single-gene nuclear mutations. One (nocr-1) is semidominant while the other two (nocr-2 and nocr-3) are recessive. Cytological and physiological studies of nocodazole's effects on the mutants demonstrate that their resistance is due neither to a lack of drug penetration nor to its degradation since, in each mutant in the presence of the drug, some microtubule networks are normal or subnormal while others remain affected as in wild-type cells. These are the first mutants resistant to microtubule depolymerizing drugs obtained in ciliates that provide a new tool for studying the assembly and dynamics of the diverse microtubule arrays in this type of organism.
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
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