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  • 1
    Digitale Medien
    Digitale Medien
    Proton/chloride cotransport in Chara: mechanism of enhanced influx after rapid external acidification (1985)
    Springer
    Planta 163 (1985), S. 411-418 
    Details
    ISSN: 1432-2048
    Schlagwort(e): Chara ; Choride influx ; Cotransport ; pH jump ; Proton motive force
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Rapid lowering of the external pH (“pH jump”) enhances Cl− influx in Chara. Experiments were conducted to distinguish between two factors which have previously been proposed to mediate in the response: raised cytoplasmic pH and lowered cytoplasmic Cl− concentration. It is concluded that the latter alternative is more likely because: i) Cl− influx is reduced at high external pH; ii) influx following the pH jump is never greater than that following pretreatment in Cl−-free solution, which reduces cytoplasmic Cl− concentration (“Cl− starvation”); iii) the joint application of pH jump and Cl− starvation does not result in a greater Cl− influx than does Cl− starvation alone; and iv) addition of NH 4 + , which increases cytoplasmic pH, does generate an additional stimulation of Cl− influx following a pH jump. It is suggested that the increased cytoplasmic pH at the end of pretreatment at high external pH decays rapidly during the pH jump, and thus any effect on Cl− influx is so transient as to be undetectable by the methods used. The results are discussed in terms of a reaction kinetic model for 2H+/Cl− cotransport (Sanders, D. and Hansen, U.-P, 1981, J. Member. Biol. 58, 139–153) which describes quantitatively; i) the effects of NH 4 + on Cl− influx in terms involving only a change in cytoplasmic pH; and ii) the combined effects of Cl− starvation and NH 4 + in terms involving only changes in Cl− concentration and cytoplasmic pH. Conversely, the combined effects of Cl− starvation and pH jump cannot be described by the model if the effect of the pH jump is the consequence of increased cytoplasmic pH. The simple interpretation of experiments on whole cells involving manipulation of $$\Delta \bar \mu _{{\text{H}}^ + } $$ (the electrochemical potential difference for protons across the plasma membrane) is questioned in the light of these and previous findings that secondary factors can determine the response of Cl− transport in Chara.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00395151
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  • 2
    Digitale Medien
    Digitale Medien
    The uptake and metabolism of urea by Chara australis: IV. Symport with sodium—A slip model for the high and low affinity systems (1993)
    Springer
    The journal of membrane biology 136 (1993), S. 263-271 
    Details
    ISSN: 1432-1424
    Schlagwort(e): Sodium ; Urea ; Symport ; Cotransport ; Charophytes ; Slip model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract We have previously investigated the electrogenic influx of urea in Chara, and the urea- and sodium-dependent membrane current. We have shown that there is a sodium-stimulated component of urea influx and a urea-stimulated component of sodium influx, and that these are of the same size. We conclude that the electrogenic inward transport of urea, and of its analogues acetamide and acrylamide, is by sodium symport, with a stoichiometric ratio of 1∶1. The kinetics of the fluxes and currents show two different K M values for sodium in different cells and two different kinds of kinetics for the effect of urea on membrane current, one of which fits the Michaelis-Menten equation, while the other shows a maximum and fits the difference of two Michaelis-Menten terms, suggesting a phenomenon like cis-inhibition. Similarities in kinetic characteristics between the inhibitory site and the electrically silent uptake site (System II) lead us to suggest that the same protein may be responsible for both the low-K M, electrogenic influx of urea (System I) and the high-K M, electrically silent influx by System II. We suggest a “slip” model for urea uptake in Chara.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00233665
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  • 3
    Digitale Medien
    Digitale Medien
    Inheritance of foreign genes in transgenic bean (Phaseolus vulgaris L.) co-transformed via particle bombardment (1996)
    Springer
    Theoretical and applied genetics 93 (1996), S. 142-150 
    Details
    ISSN: 1432-2242
    Schlagwort(e): Key words Transgenic bean ; Phaseolus vulgaris ; Co-transformation ; Biolistic ; Inheritance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Exploiting the biolistic process we have generated stable transgenic bean (Phaseolus vulgaris L.) plants with unlinked and linked foreign genes. Co-transformation was conducted using plasmid constructions containing a fusion of the gus and neo genes, which were co-introduced with the methionine-rich 2S albumin gene isolated from the Brazil nut and the antisense sequence of AC1, AC2, AC3 and BC1 genes from the bean golden mosaic geminivirus. The results revealed a co-transformation frequency ranging from 40% to 50% when using unlinked genes and 100% for linked genes. The introduced foreign genes were inherited in a Mendelian fashion in most of the transgenic bean lines. PCR and Southern blot hybridization confirmed the integration of the foreign genes in the plant genome.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s001220050259
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  • 4
    Digitale Medien
    Digitale Medien
    Inheritance of foreign genes in transgenic bean (Phaseolus vulgaris L.) co-transformed via particle bombardment (1996)
    Springer
    Theoretical and applied genetics 93 (1996), S. 142-150 
    Details
    ISSN: 1432-2242
    Schlagwort(e): Transgenic bean ; Phaseolus vulgaris ; Co-transformation ; Biolistic ; Inheritance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Exploiting the biolistic process we have generated stable transgenic bean (Phaseolus vulgaris L.) plants with unlinked and linked foreign genes. Co-transformation was conducted using plasmid constructions containing a fusion of the gus and neo genes, which were co-introduced with the methionine-rich 2S albumin gene isolated from the Brazil nut and the antisense sequence of AC1, AC2, AC3 and BC1 genes from the bean golden mosaic geminivirus. The results revealed a co-transformation frequency ranging from 40% to 50% when using unlinked genes and 100% for linked genes. The introduced foreign genes were inherited in a Mendelian fashion in most of the transgenic bean lines. PCR and Southern blot hybridization confirmed the integration of the foreign genes in the plant genome.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00225739
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