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  • 1
    Electronic Resource
    Electronic Resource
    Relation between protoplast division, cell-cycle stage and nuclear chromatin structure (1988)
    Springer
    Protoplasma 142 (1988), S. 127-136 
    Details
    ISSN: 1615-6102
    Keywords: Cell cycle ; Protoplast division ; Chromatin structure ; Flow-cytometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Using different sources of protoplasts and two complementary techniques, flow cytometry and image analysis, to study the cell-cycle phases, we sought to define the particular protoplast state associated with the disposition to divide. Both inPetunia and inNicotiana plumbaginifolia, tissues with a higher G2 frequency (from different aged plants) yielded protoplasts capable of increased cell division. InSorghum, the age of the plant does not modify the proportion of G2 nuclei in leaf protoplasts, and we used root protoplasts to increase G2 frequencies. InHelianthus annuus, leaf protoplasts did not divide; however, hypocotyl protoplast preparations with relatively high 4C DNA frequencies do divide. Moreover, image analysis of chromatin structure indicated that leaf nuclei were in the G0 phase, unlike those from hypocotyls which were in G1. A high frequency of protoplasts with G2 nuclei appears to be correlated with the ability of a given preparation to undergo division; conversely, the differentiated G0 state is not conducive to division.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01290869
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  • 2
    Electronic Resource
    Electronic Resource
    Localization of target cells and improvement ofAgrobacterium-mediated transformation efficiency by direct acetosyringone pretreatment of carrot root discs (1993)
    Springer
    Protoplasma 174 (1993), S. 10-18 
    Details
    ISSN: 1615-6102
    Keywords: Acetosyringone ; Agrobacterium ; Carrot ; Cell cycle ; GUS assay ; Indole acetic acid levels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Localization of target cells forAgrobacterium-mediated transformation in the carrot root disc model has been achieved after inoculation with a disarmedA. tumefaciens strain harbouring a GUS-intron construct. The first GUS positive cells could be detected on both sides of the discs 48 h after inoculation. The transformed cells were always more numerous on the apical side, mainly localized in the intrafascicular cambium and in the immature phloem strands. The kinetics of free endogenous IAA levels on both sides after wounding have been determined, indicating that rapid IAA accumulation on the apical side was not simply due to polar migration from the basal side. Attempts to optimize transformation efficiency were made by pretreating the discs with various concentrations of acetosyringone (AS) and/or naphthalene acetic acid (NAA). Surprisingly, while 25 μM AS applied to bacteria prior to the inoculations was ineffective, the same AS concentration applied as a pretreatment to the discs strongly increased the number of transformed cells in the target tissues and decreased the lag time for the appearance of the first GUS positive cells. NAA pretreatment on the basal side enhanced the AS effect. AS pretreatment was found both to advance the reentry of competent cells with a potential for cell division into the S phase of the cell cycle and to stimulate bacterial attachment to the cell walls. The relationship between transformation efficiency and DNA synthesis in the host cells is discussed. AS treatment of plant tissues prior to inoculation is proposed as a means of increasing the transformation rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01404037
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  • 3
    Electronic Resource
    Electronic Resource
    Artificial antisense RNA regulation of YBR1012 (YBR136w ), an essential gene from Saccharomyces cerevisiae which is important for progression through G1/S (1995)
    Springer
    Molecular genetics and genomics 249 (1995), S. 51-57 
    Details
    ISSN: 1617-4623
    Keywords: Antisense RNA ; YBR1012/YBR136w/MEC1/ESR1 ; Saccharomyces cerevisiae ; Flow cytometry ; Cell cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract YBR1012 (YBR136w) is an essential gene from Saccharomyces cerevisiae identified during the systematic sequencing of part of the right arm of chromosome II. We previously constructed a conditional allele of YBR1012 based on antisense RNA, by inserting a small fragment of this gene downstream from the inducible UASGAL10-CYC1 promoter. Several other antisense RNA constructions have since been made and their activity tested. The response of the system appears to be very delicate, as the presence or absence of 13 nucleotides of polylinker in the 300 nucleotide antisense transcript can dramatically modify its effectiveness. The most effective antisense RNA construction was used in flow cytometry studies to investigate the role of ybr1012p. The results show that during the antisense RNA block some 80% of the cells are arrested with their DNA unreplicated, suggesting that Ybr1012p is needed for progression through G1 or early S phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00290235
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