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  • 1
    ISSN: 1615-6102
    Keywords: Fluorescent brighteners ; Inhibitors ; Cell wall ; Cellulose microfibrils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Calcofluor White ST is a fluorescent brightener that has previously been shown to alter cellulose ribbon assembly in the bacteriumAcetobacter xylinum. In this report, we demonstrate that Calcofluor also disrupts cell wall assembly in the eukaryotic algaOocystis apiculata. When observed with polarization microscopy, walls altered by Calcofluor show reduced birefringence relative to controls. Electron microscopy has shown that these altered walls contain regions which consist primarily of amorphous material and which generally lack organized microfibrils. We propose that wall alteration occurs because Calcofluor binds with the glucan chains polymerized by the cellulose synthesizing enzymes as they are produced. As a consequence, the glucan chains are prevented from co-crystallizing to form microfibrils. Synthesis of normal walls resumes when Calcofluor is removed, which is consistent with our proposal that Calcofluor acts by direct physical interaction with newly synthesized wall components. Several types of fluorescent patterns at the cell wall/plasmalemma interface have also been observed following Calcofluor treatment. Fluorescent spots, striations; helical bands, and lens-shaped thickenings have been documented. Each of these patterns may be the result of the interaction of Calcofluor with cellulose at different spatial or temporal levels or from varying concentrations of the brightener itself. Helical bands and lens-shaped thickenings also have been examined with the electron microscope. Like other regions of wall alteration, they are found to contain primarily amorphous material. Finally, we note that cells with severely disrupted walls are unable to complete their normal life cycle.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1615-6102
    Keywords: Amiprophos-methyl ; Microtubule organizing center
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A one hour exposure to 3 μM amiprophos-methyl (APM) depolymerizes all MT arrays in cells from higher plant suspension cultures. On removal of APM, MT repolymerization sites are detected using immunofluorescent staining. During interphase, Mt arrays return uniformly dispersed across the cell cortex with transverse arrays in elongated cells and random arrays in isodiametric cells. During cell division, MT arrays return as follows: Prophase-MT arrays return in association with the nuclear envelope. Metaphase-MTs return associated with chromosomes. Teleophase-MTs return in apparent association with the reforming nuclear envelope and as aberrant phragmoplasts. MTOCs in higher plant cells may be membrane associated at many stages in the cell cycle. Isolated, condensed chromosomes are capable of nucleating MTs, which can attain small, spindle-like configurations.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 133 (1986), S. 140-148 
    ISSN: 1615-6102
    Keywords: Amiprophos-methyl (APM) ; Cell suspension cultures ; Differentiation ; Microtubules ; Tracheary elements ; Xylogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary InZinnia suspension cultures, two general categories of tracheary element (TE) secondary wall patterns can be distinguished: bands and webs. Band patterns are found in elongated cells or regions of cells, web patterns in isodiametric cells or regions of cells. Interphase cortical microtubule arrays, organized before overt differentiation occurs, determine both the shape of the cell and whether band or web patterns will be deposited at the time of TE formation. By altering cell shape and consequently also altering the interphase microtubule array, it is possible to control the type of wall pattern which is deposited. These results provide support for the hypothesis which states that the organization of interphase cortical microtubule arrays (i.e., random or parallel), which laterally associate during tracheary element differentiation, determines the pattern in which secondary walls will be deposited.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 136 (1987), S. 118-124 
    ISSN: 1615-6102
    Keywords: Amiprophos-methyl (APM) ; Microtubule inhibitor ; Plant cell cultures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In plant cell suspension cultures sensitive to the herbicide amiprophos-methyl (APM), 1 to 3 μM APM completely depolymerized both cortical and mitotic microtubule (MT) arrays in 1 hour. In comparison, a 2 hour application of 3 mM colchicine had no effect on MT arrays. Recovery from APM treatment occurred as early as 5 minutes after removal of APM. Short, cortical MTs were visible in 3 hours and complete MT arrays were found within 22 hours after drug removal. Sensitivity to APM-induced MT depolymerization varied according to species but was increased or decreased by varying the mitotic rate in cultures. The results indicated APM sensitivity was related to lowered stability of MT arrays in rapidly cycling cells. APM treatment may help distinguish “stabilized” cortical MTs in elongating cells and “nonstabilized” cortical MTs in rapidly dividing cells.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 103 (1980), S. 205-229 
    ISSN: 1615-6102
    Keywords: Cell wall ; Cytochalasin B ; Microfibril orientation ; Microtubules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cortical microtubule arrays in the radish root hair were analyzed from reconstructions of serial ultra-thin sections in order to test extant hypotheses concerning the role of microtubules in the deposition of oriented microfibrils of cellulose. Passing away from the tip, root hairs exhibit a transition from random to oriented deposition of microfibrils at approximately 25 μm. Along the root hair, passing back from the tip, the microtubules: a) increase in number to a plateau at 25 μm; b) change their length profiles from approximately 60% less than 1 μm long in the hair tip to approximately 40% less than 1 μm long at 60 μm; c) maintain a constant pattern of angular deviation from the long axis, which is similar to the deviation pattern of the oriented wall fibrils; d) maintain a constant (approximately 70% of tubules) close (within 50 nm) proximity to the plasma membrane (PM); e) maintain a low (approximately 20%) degree of inter-microtubule proximity (i.e., within 50 nm of one another); f) show evidence for some variable long range (〉50 nm) association. Fixation with glutaraldehyde in a complete microtubule polymerization medium (MTPM), or pretreatment with cytochalasin B cause an approximate twofold increase in 1. the proportion of long microtubules in the tip region and 2. microtubules within 50 nm of one another. Fixation in incomplete MTPM (without GTP) produces results similar to phosphate buffer controls. Alternative explanations for these results are examined. A new hypothesis accounting for microtubule involvement in oriented microfibril deposition is described.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1615-6102
    Keywords: Cell suspension cultures ; Differentiation ; Microtubules ; Taxol ; Xylogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary InZinnia elegans tissue cultures, cortical microtubules reorient from longitudinal to transverse arrays as the culture age increases and before differentiation of tracheary elements is visible. The orientation of microtubules, in the period just before visible differentiation, determines the direction of the secondary wall bands in forming tracheary elements. Taxol, applied early in culture, stabilizes the microtubules of most cells in the longitudinal direction. Tracheary elements differentiating in these taxol treated cultures show secondary wall bands parallel to the long axis of the cell while those differentiating in control cultures always have wall bands transverse to the long axis of the cell. It is proposed that, in untreatedZinnia cultures, microtubules are reoriented by a gradual shift from longitudinal to transverse and this reorientation normally occurs before differentiation becomes visible. Once initiated, tracheary element differentiation involves lateral association of microtubules to form the discrete bands typical of secondary wall patterns.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 144 (1988), S. 10-16 
    ISSN: 1615-6102
    Keywords: Differentiation ; Microtubule ; Tracheary element ; Xylogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary DifferentiatingZinnia cultures have two bursts of tracheary element (TE) formation which resemble the production of proto- and metaxylem in higher plants. TEs in the first burst have annular, spiral or reticulate secondary wall patterns while those in the second burst have reticulate, scalariform or pitted walls. Continuing wall deposition in TEs results in the transformation of annular or spiral patterns into scalariform or pitted. Indirect immunofluorescent observation of TE microtubules (MTs) during continuing wall deposition indicates an annular/spiral pattern is deposited first followed by the introduction of new arrays of MTs which guide later, in-filling wall deposition.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1615-6102
    Keywords: Cell suspension cultures ; Differentiation ; Microfibril deposition ; Microtubules ; Xylogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Xylogenesis has been studied in primary suspension cultures ofZinnia elegans L.: The wall patterns produced in culture closely resemble those described for intact tissues (annular, spiral, reticulate, scalariform, pitted). Using fluorescence microscopy and immuno-cytochemical techniques we have followed both the changes in wall deposition and microtubule organization during xylogenesis. Calcofluor white has been used to detect secondary wall deposition before it can be observed using either phase contrast or polarization optics. The development of tracheary elements can be divided into three stages: 1. microtubules grouped into bands without secondary wall deposition evident; 2. groups of microtubules subtending wall material only visible using Calcofluor white; 3. a complex microtubule pattern reflected by well developed wall thickenings detected using Calcofluor, phase contrast and polarization optics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 103 (1980), S. 231-240 
    ISSN: 1615-6102
    Keywords: Cytochalasin B ; Cytoplasmic streaming ; Microfilaments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Two distinguishable populations of microfilaments (mfs) can be identified in the radish root hair. Bundles of mfs are found throughout the cytoplasm, excluding the tip region of the hair. Single mfs occur only as a cortical array, specifically associated with the microtubules. Both mf populations are oriented parallel to the direction of streaming. Hairs grown in 5 μg/ml cytochalasin B (CB) exhibit site-specific differential responses to the drug in both their streaming pattern and sensitivity of their mfs. Cytochalasin B elicits the following responses: 1. cytoplasmic streaming is reduced in all regions of the hair; 2. small particles (〈1 μm in diameter) still stream, whereas large particles (〉1 μm in diameter) no longer stream but exhibit an oscillatory or rotational motion; 3. filament bundles show increasing sensitivity to CB along the length of the hair; 4. single mfs show decreasing sensitivity to CB along the hair length. The effects of CB on cytoplasmic streaming can be related to its effects on both mf populations, thus suggesting that although mf bundles are probably involved in streaming in the sub apical and basal regions of the hair, single mfs are most likely involved in generating the slower, more irregular streaming patterns exhibited in the hair tip and CB-treated hair base.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1615-6102
    Keywords: Microtubules ; Microfilaments ; Wall microfibrils ; Cotton fiber ; Cytoskeletal disruption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effects of various cytoskeletal disrupting agents (cholchicine, oryzalin, trifluralin, taxol, cytochalasins B and D) on microtubules, microfilaments and wall microfibril deposition were monitored in developing cotton fibers, using immunocytochemical and fluorescence techniques. Treatment with 10−4 M colchicine, 10−6 M trifluralin or 10−6 M oryzalin resulted in a reduction in the number of microtubules, however, the “drug-stable” microtubules still appear to influence wall deposition. Treatment with 10−5 M taxol increased the numbers of microtubules present within 15 minutes of application. New microtubules were aligned parallel to the existing ones, however, some evidence of random arrays was observed. Microtubules stabilized with taxol appeared to function in wall organization but do not undergo normal re-orientations during development. Microtubule disrupting agent had no detectable affect on the microfilament population. Exposure to either 4×10−5 M cytochalasin B or 2×10−6M cytochalasin D resulted in a disruption of microfilaments and a re-organization of microtubule arrays. Treatment with either cytochalasin caused a premature shift in the orientation of microtubules in young fibers, whereas in older fibers the microtubule arrays became randomly organized. These observations indicate that microtubule populations during interphase are heterogeneous, differing at least in their susceptibility to disruption by depolymerizing agents. Changes in microtubule orientation (induced by cytochalasin) indicate that microfilaments may be involved in regulating microtubule orientation during development.
    Type of Medium: Electronic Resource
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