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  • 11
    Electronic Resource
    Electronic Resource
    Actin filament array during side branch initiation in protonema cells of the mossFunaria hygrometrica: an actin organizing center at the plasma membrane (1989)
    Springer
    Protoplasma 151 (1989), S. 167-170 
    Details
    ISSN: 1615-6102
    Keywords: Funaria ; Actin filaments ; Side branch formation ; Moss protonema
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary With an improved method to visualize the actin filament system it is possible to detect a small, peculiar accumulation of actin filaments under the prospective area of side branch formation inFunaria protonema cells. It consists of a ring-like configuration of actin filaments from which filaments radiate, preferentially along the plasma membrane. During the transition to tip growth the arrangement becomes loosened and eventually disappears whereas the filaments are concentrated in inner regions of the cytoplasm with a maximum in the apical dome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01403455
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  • 12
    Electronic Resource
    Electronic Resource
    Formation and disintegration of cisternae of the endoplasmic reticulum visualized in live cells by conventional fluorescence and confocal laser scanning microscopy: Evidence for the involvement of calcium and the cytoskeleton (1990)
    Springer
    Protoplasma 155 (1990), S. 166-175 
    Details
    ISSN: 1615-6102
    Keywords: Endoplasmic reticulum ; Calcium ; Actin filaments ; DiOC6 ; Onion epidermis cells ; Confocal laser scanning microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The influence of substances interfering with the cellular calcium distribution on the organization of the endoplasmic reticulum has been investigated in live epidermal cells of onion bulb scales. The endoplasmic reticulum was visualized by vital staining with the fluorochrome DiOC6(3). It constitutes in these cells an anastomosing membrane system which is composed of three forms: cisternae, short tubules forming a peripheral network, and long tubular strands deeper in the cytoplasm. In the presence of all tested calcium interfering substances, e.g. the ionophore calcimycin (5 μM), the cryptate 221 (0.5 mM), the calmodulin antagonist calmidazolium (10 μM), the tubular ER elements disappear and huge cisternae form instead. The potassium-selective cryptate 222 (1 mM) chemically very similar to the effective cryptate 221 does not cause this change in ER pattern. Actin filaments which are indispensable for ER distribution in the epidermis cells appear to fragment in the presence of the drugs indicating some similarity with the action of cytochalasin D (Quader et al. 1989). Removal of the drugs initiates a characteristic sequence of recovery. The cisternae disintegrate at their edges into tubular loops which are pulled away from this cellular site as long tubular strands. In the presence of cytochalasin D (2 μM) the disintegration of the cisternae is inhibited indicating that kinetic forces are necessary to generate and maintain the spatial distribution of at least parts of the tubular ER meshwork. For the first time the decay of cisternae is described in live cells. The effect of the calcium agents is also compared with changes in ER organization caused by other chemical or natural means.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01322626
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  • 13
    Electronic Resource
    Electronic Resource
    Endoplasmic reticulum and cytoplasmic streaming: Fluorescence microscopical observations in adaxial epidermis cells of onion bulb scales (1986)
    Springer
    Protoplasma 131 (1986), S. 250-252 
    Details
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01282989
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  • 14
    Electronic Resource
    Electronic Resource
    Influence of cytosolic pH changes on the organisation of the endoplasmic reticulum in epidermal cells of onion bulb scales: Acidification by loading with weak organic acids (1990)
    Springer
    Protoplasma 157 (1990), S. 216-224 
    Details
    ISSN: 1615-6102
    Keywords: Endoplasmic reticulum ; DiOC6 (3) ; Weak organic acids (cytosolic pH) ; Actin filaments ; Organelle movement ; Onion epidermal cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The anastomosing ER system of epidermal cells of onion bulb scales is composed of three modifications: lamellar and tubular elements, located in the cell periphery, and long tubular stands located deeper in the cytoplasm. Cytoplasmic acidification of epidermal cells by loading with weak organic acids like acetic or propionic acid causes the decay of the lamellar elements and the disappearance of long tubular strands. Organelle movement is also inhibited. The effects depend on the pH of the incubation medium and on the administered acid concentration, and are characterized by a distinct lag phase of about 7 min. The induced ER changes are transient with adaptation starting after about 50min. Buffer components alone have little influence on the cellular ER organization within a pH-range of 4.0–8.0. However, the pH of the medium strongly affects the time course of the effects as well as recovery after omitting the administered acid. Both modulation and recovery occur more rapidly at neutral or slightly alkaline pH. Actin filaments, which play a major role in ER organization and organelle movement, are not affected by cytosolic acidification.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01322654
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  • 15
    Electronic Resource
    Electronic Resource
    Influence of the herbicide oryzalin on cytoskeleton and growth ofFunaria hygrometrica protonemata (1988)
    Springer
    Protoplasma 142 (1988), S. 55-67 
    Details
    ISSN: 1615-6102
    Keywords: Funaria protonema ; Indirect immunofluorescence ; Microtubules ; Oryzalin ; Polar growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Protonemata ofFunaria hygrometrica were exposed to the herbicidal MT inhibitor oryzalin. A reduction of the growth rate together with a disturbance of oriented polar growth is observed. Both effects are reversible. Visualization of MT by IFT reveals differential sensitivities of MT. At lower concentrations (⩽10−6 M) only the cytoplasmic MT are depolymerized causing impairment of the migration of the nucleus and the transport of the plastids. Close association of MT with the surface of the plastids is demonstrated. At higher concentrations of oryzalin spindle and phragmoplast MT are affected as well. They are found in unusual orientations and display a variety of aberrant forms like multipolar spindles or the occurrence of several “mini-spindles” within one cell. The mode of action of oryzalin is discussed and the necessity of a continuous network of cytoplasmic MT between nucleus and growing tip for the maintenance of polar growth is emphasized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01273226
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  • 16
    Electronic Resource
    Electronic Resource
    Presence and absence of the preprophase band of microtubules in moss protonemata: a clue to understanding its function? (1991)
    Springer
    Protoplasma 163 (1991), S. 156-161 
    Details
    ISSN: 1615-6102
    Keywords: Preprophase band of microtubules ; Protonema ; Funaria hygrometrica ; Cell wall formation ; Cell division
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary InFunaria protonemata, preprophase bands (PPBs) of microtubules do not develop when the tip cell divides, when side branches are initiated or in intercalary regeneration divisions. We report here that PPBs do, however, develop when a tmema cell is formed. In the former cases, cell division is not coupled with an expansion of the mother cell wall at the site where the cell plate will attach. In the latter case, the mother cell wall ruptures at that site and the tmema cell elongates. This observation and the findings on presence and absence of the PPB in other cell types indicate a connection between PPB occurrence and mother cell wall expansion. They support the idea that the PPB might be involved in the local secretion of cell wall material. We extend this notion, suggesting that the microtubules of the PPB control the oriented deposition of a thin layer of cellulose microfibrils at the mother cell wall which supports the firm attachment of the cell plate when the mother cell wall expands.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01323339
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  • 17
    Electronic Resource
    Electronic Resource
    Cytoskeletal elements in cotton seed hair developmentin vitro: Their possible regulatory role in cell wall organization (1987)
    Springer
    Protoplasma 137 (1987), S. 56-62 
    Details
    ISSN: 1615-6102
    Keywords: Cytoskeleton ; Cellulose fibrils ; Cotton fibres ; Coated pits
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The localization and orientation of cytoskeletal elements in developing cotton fibres were studied by the indirect immunofluorescence and the dry cleaving technique. Microtubules are transversely arranged to the cell axis, most probably in a flat helix, in the cortex of expanding fibres. Since the innermost deposited cellulose microfibrils always show primarily the same orientation it is postulated that the microtubules control the transverse deposition of the cellulose fibrils. Little further cell expansion takes place during secondary wall formation and the microfibril pattern corresponds to that of the cortical microtubules,e.g., in the steepness of their helicoidal turns. Microtubules with a length of 7–20 μm were observed, probably they are longer. The importance of microtubule length on microfibril deposition is discussed. The density of microtubule packing is in the range of 8–14 μm-1 as in other comparable cell types. In contrast to the microtubules, actin filaments are most likely longitudinally oriented during different phases of fibre development. The dry cleaving technique reveals numerous coated pits in the plasma membrane which are not crossed by microtubules. They seem to be linked to the latter by filamentous structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01281176
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  • 18
    Electronic Resource
    Electronic Resource
    A cytokinin-sensitive mutant of the moss,Physcomitrella patens, defective in chloroplast division (1989)
    Springer
    Protoplasma 152 (1989), S. 1-13 
    Details
    ISSN: 1615-6102
    Keywords: Physcomitrella protonemata ; Chloroplast division ; Cytoskeleton ; Cell division abnormalities ; Microinjection ; Moss mutant ; Protoplasts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary An X-ray induced mutant (PC22) of the moss,Physcomitrella patens was analysed with respect to its morphology, physiology and suitability for microculture techniques. The mutant protonemata are defective in bud formation and in chloroplast division. As a consequence of the latter, giant chloroplasts are formed which disturb the development of the phragmoplast, the formation of regular cross walls, and cell division. Abnormal cross walls are rich in callose. The actin cytoskeleton was found to be less regularly developed in the mutant than in the wild type. Three-dimensional analysis of the microtubular arrangement with confocal laser scan microscopy demonstrates a close association between spindle- or phragmoplast- and “interphase”-microtubules. The deficiencies in chloroplast division and in bud formation can partly be compensated for by exogeneously applied cytokinin. The suitability of this particular developmental mutant for further studies was shown by regeneration of protoplasts in microculture and microinjection of the fluorochrome Lucifer yellow into the chloroplast.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01354234
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  • 19
    Electronic Resource
    Electronic Resource
    Das Experiment: Geißelregeneration bei Chlamydomonas reinhardii (1984)
    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 14 (1984), S. 125-127 
    Details
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/biuz.19840140406
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