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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
    Propranolol apparently separates the physical and compositional characteristics of muscle growth induced by clenbuterol (1987)
    Springer
    Bioscience reports 7 (1987), S. 51-57 
    Details
    ISSN: 1573-4935
    Schlagwort(e): muscle ; growth ; adrenergic agents ; clenbuterol ; propranolol
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract The effect of propranolol on clenbuterol-induced changes in muscle fibre size and protein content were studied. Propranolol did not inhibit the ability of clenbuterol to stimulate protein accretion but reduced the increase in muscle fibre size. The compositional and physical characteristics of clenbuterol-induced muscle growth thus appeared to be separated by propranolol.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01122727
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  • 4
    Digitale Medien
    Digitale Medien
    Clenbuterol, a beta agonist, induces growth in innervated and denervated rat soleus muscle via apparently different mechanisms (1987)
    Springer
    Bioscience reports 7 (1987), S. 525-532 
    Details
    ISSN: 1573-4935
    Schlagwort(e): rat soleus muscle ; protein turnover ; clenbuterol ; beta agonist
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Dietary administration of the anabolic agent, clenbuterol, has already been shown to inhibit or reverse denervation-induced atrophy in rat soleus muscles. We now show that the ameliorative effects of clenbuterol in denervated rat muscles are due principally to a large increase in protein synthesis. This results from both an increase in protein synthetic capacity and a normalised translational efficiency. The responses of innervated and denervated muscles are therefore fundamentally different, the changes in denervated muscles being reminiscent of the classical pleiotypic response of cells to growth factors.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01116510
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  • 5
    Digitale Medien
    Digitale Medien
    The effect of the anabolic agent, clenbuterol, on overloaded rat skeletal muscle (1987)
    Springer
    Bioscience reports 7 (1987), S. 143-149 
    Details
    ISSN: 1573-4935
    Schlagwort(e): compensatory hypertrophy ; muscle ; clenbuterol
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract The dietary administration of clenbuterol to young male rats has been shown to produce a muscle specific hypertrophic growth response. This paper demonstrates that the combined effect of drug treatment and hypertrophic stimulus induced by tenotomy produced an additive effect on muscle growth. This effect was demonstrated in terms of both muscle composition (protein and RNA) and fibre size.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01121878
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  • 6
    Digitale Medien
    Digitale Medien
    Inhibition and reversal of denervation-induced atrophy by theβ-agonist growth promoter, clenbuterol (1986)
    Springer
    Bioscience reports 6 (1986), S. 811-818 
    Details
    ISSN: 1573-4935
    Schlagwort(e): muscle ; protein degradation ; clenbuterol ; denervation-induced atrophy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Dietary administration of the growth promoter, clenbuterol, ameliorated denervation-induced atrophy in rat soleus muscles. In acutely denervated muscles the drug inhibited the appearance of atrophy, and in chronically denervated muscles the atrophy was almost fully reversed. Responses in slow twitch oxidative fibres were particularly marked.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01117104
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