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  • 1
    Electronic Resource
    Electronic Resource
    Caffeine inhibition of cytokinesis: Dynamics of cell plate formation-deformationin vivo (1985)
    Springer
    Protoplasma 129 (1985), S. 28-35 
    Details
    ISSN: 1615-6102
    Keywords: Caffeine ; Cell Plate Formation ; Cytokinesis ; Tradescantia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effect of caffeine on cell plate formation inTradescantia stamen hair cells has been studiedin vivo using Nomarski differential interference contrast microscopy. It is well known that caffeine is a potent inhibitor of cell plate formation. Direct examination of drug-treated cells reveals that the cell plate always arises and grows centrifugally until almost complete. Up to this point drug-treated cells are indistinguishable from controls. However in the presence of caffeine the plate never reaches completion but rather appears to melt away until no refractile structure remains. Even after cells have been cultured for 24 hours in caffeine a cell plate always arises only to subsequently break down. Studies on the time of caffeine action show that within minutes before the onset of cell plate formation, the drug efficiently reaches the target site. This effect is partially reversible by washing out the caffeine with HEPES/KCl buffer, however the time required for the cell plate to reach completion is prolonged and in some instances the plate appears to be fragmented. Adenosine is also partially effective in reversing the caffeine inhibition of cell plate formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01282302
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  • 2
    Electronic Resource
    Electronic Resource
    Caffeine inhibition of cytokinesis: Ultrastructure of cell plate formation/degradation (1990)
    Springer
    Protoplasma 157 (1990), S. 182-192 
    Details
    ISSN: 1615-6102
    Keywords: Caffeine ; Cell plate ; Phragmoplast ; Endoplasmic reticulum ; Golgi vesicles ; Microtubules ; Calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Caffeine is a potent inhibitor of cell plate formation in dividing plant cells. Previous studies living cells reveal that the drug always permits the cell plate to arise and grow normally until about 80% complete, but then causes it to break down. In the present investigation we examine this formation/degradation cycle at the ultrastructure level. Our results show that during the formation phase the caffeine treated plate is indistinguishable from untreated controls. Phragmoplast microtubules arise and align in the interzone, Golgi vesicles are produced and aggregate in a line that defines the young cell plate, and considerable fusion of these vesicles occurs to form islands of plate material. However, under the influence of caffeine these islands do not fuse to form the enlarged lamellar expanses characteristic of maturing cell plates. Instead, the partially fused material reverts to small vesicles which appear to become resorbed by the cellular membrane systems. The resorption process continues leaving no evidence of the previously developing plate, although occasionally we observe a stub of fused vesicles attached to the parent wall. Following cell plate disintegration the reformed nuclei move close together and occupy the central region of the cell. These observations focus attention on the consolidation phase of cell plate formation as the one being maximally affected by caffeine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01322651
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Sporangial structure inPhytophthora is disrupted after high pressure freezing (1991)
    Springer
    Protoplasma 165 (1991), S. 203-208 
    Details
    ISSN: 1615-6102
    Keywords: High pressure freezing ; Plunge freezing ; Freeze substitution ; Phytophthora ; Sporangia ; Immunogold labelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effects of high pressure on the ultrastructure of sporangia ofPhytophthora cinnamomi andP. palmivora have been examined by comparing sporangia frozen in a Balzers hyperbaric freezer or pressurized in a French pressure cell with sporangia plunge frozen at ambient pressure. Both freeze fixation methods provided excellent preservation of most cell structures, but one organelle type seen in plunge frozen material, the large peripheral vesicle (LPV), was not observed in high pressure frozen sporangia. Instead, these sporangia contained large irregularly shaped structures which exhibit the patterns of spatial distribution and, forP. cinnamomi, the monoclonal antibody binding characteristic of LPVs. These findings suggest that some factor of the hyperbaric freezing process causes LPVs to be degraded. Sporangia ofP. cinnamomi that had been pressurized in a French pressure cell also exhibited large structures with the spatial distribution and monoclonal antibody binding characteristic of LPVs. The apparent expansion of LPVs that follows from both pressurizing treatments causes considerable passive disruption of sporangial structure. This is the first report of a major disturbance of cell structure from use of the Balzers hyperbaric freezer, and reflects the lability, noted in previous work, of LPVs inPhytophthora.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01322290
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  • 4
    Electronic Resource
    Electronic Resource
    Actin-endoplasmic reticulum complexes inDrosera (1990)
    Springer
    Protoplasma 155 (1990), S. 116-126 
    Details
    ISSN: 1615-6102
    Keywords: Actin ; Cytoplasmic streaming ; Drosera ; Endoplasmic reticulum ; Freeze fixation ; Freeze substitution ; Hyperbaric freezing ; High pressure freezing ; Immunogold localization ; Microfilaments ; Plasmalemma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In epidermal cells ofDrosera tentacles that have been preserved for ultrastructural analysis through high pressure freeze fixation and freeze substitution we describe the frequent occurrence of microfilament (MF)-endoplasmic reticulum (ER) complexes. These are found throughout the cytoplasm where they are observed in close association with the plasmalemma (PL), the tonoplast, nuclei, mitochondria, chloroplasts, and microbodies. The MF component of the complexes is identified as actin based on immunogold labelling with actin antibodies. The actin-ER complexes are prominent in the cortical cytoplasm. In this region a network of predominantly tubular ER occupies an intermediary position in which it associates closely with both the PL and the actin MFs. We suggest that the ER, especially those elements adjacent to the PL in the cortical cytoplasm, stabilizes the actin MFs and provides the necessary anchor against which the forces for cytoplasmic streaming are generated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01322621
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  • 5
    Electronic Resource
    Electronic Resource
    Caffeine inhibition of cytokinesis: effect on the phragmoplast cytoskeleton in livingTradescantia stamen hair cells (1997)
    Springer
    Protoplasma 196 (1997), S. 155-166 
    Details
    ISSN: 1615-6102
    Keywords: Caffeine ; Cytokinesis ; Cytoskeleton ; Microinjection ; Phragmoplast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The distribution of microtubules and actin microfilaments during caffeine-induced inhibition of cell plate formation has been studied in livingTradescantia stamen hair cells. Previous studies have shown that caffeine allows cell plate initiation but prevents its completion, resulting in binucleate cells. In the present study, confocal microscopy of cells microinjected with fluorescent brain tubulin or phalloidin, and cultured in the presence 5 mM caffeine, revealed that the initiation and early lateral expansion phase of the phragmoplast occur normally. However, caffeine completely inhibits the formation of the cytoskeletal torus which occurs in untreated cells during the late stages of cell plate and phragmoplast expansion. Caffeine further causes the disintegration of the incomplete cell plate. The results allow us to distinguish two phases in cell plate and phragmoplast growth: the initiation and early expansion phase, which is not affected by caffeine, and the late lateral expansion phase, which is completely inhibited in the presence of caffeine. Also in this study, the use of a high phalloidin concentration has revealed structural detail about the actin microfilaments involved in cell plate formation: microfilaments are observed that link the expanding edge of the phragmoplast with the cortical division site. In addition, cortical actin patches are observed within the actin depleted zone that might play a role in guidance of phragmoplast and cell plate expansion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01279564
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  • 6
    Electronic Resource
    Electronic Resource
    Growth inhibition and recovery in freeze-substitutedLilium longiflorum pollen tubes: structural effects of caffeine (1997)
    Springer
    Protoplasma 196 (1997), S. 21-33 
    Details
    ISSN: 1615-6102
    Keywords: Caffeine ; Freeze substitution ; Lilium ; Pollen tubes ; Rapid freeze fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In an attempt to correlate structural effects with the known dissipation of the tip-focused Ca2+ gradient caused by caffeine, we have examined the ultrastructure of caffeine-treated lily pollen tubes prepared by rapid freeze fixation and freeze substitution. We show that treatment with caffeine results in a rapid rearrangement of secretory vesicles at the pollen tube tip; the normal cone-shaped array of vesicles is rapidly dispersed. In addition, microfilament bundles appear in the tip region, where they had previously been excluded. Delocalized vesicle fusion continues in the presence of caffeine but tube extension ceases. Removal of caffeine from the growth medium initially causes tip swelling, delocalized vesicle fusion and presence of microfilaments well into the tip before normal structure and growth resume, concurrent with the previously reported return to a normal Ca2+ gradient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01281055
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