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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    The journal of membrane biology 96 (1987), S. 263-276 
    ISSN: 1432-1424
    Keywords: Ca2+ channel ; I-V relation ; membrane excitation ; Nitellopsis obtusa ; tonoplast-free cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The presence of a Ca2+ channel in the plasmalemma of tonoplast-freeNitellopsis obtusa cells was demonstrated and its characteristics were studied using current- and voltage-clamp techniques. A long-lasting inward membrane current (I m ), recorded using a step voltage clamp, consisted of a single component without time-dependent inactivation. Increasing either [Ca2+] o or [Cl−] o 1) enhanced the maximum amplitude of inwardI m ((I m ) p ) and 2) shifted the peak voltage ((V m ) p ) at(I m ) p to more positive values under ramp-shaped voltage clamping and 3) depolarized the peak value of action potentials. This behavior is consistent with predictions based on the Nernst equation for Ca2+ but not for Cl−. DIDS (4,4′-diisothiocyano-2,2′-disulfonic acid stilbene) did not suppress(I m ) p in tonoplast-free cells, in contrast with its effect on normal cells. La3+ and nifedipine blocked(I m ) p irreversibly. On the other hand, Ca2+ channel agonist, BAY K 8644 irreversibly enhanced(I m ) p . Both Sr2+ influx and K+ efflux increased upon excitation. The charge carried by Sr2+ influx was compensated for by K+ efflux. It is concluded that only the Ca2+ channel is activated during plasmalemma excitation in tonoplast-free cells. In terms of the magnitude of(I m ) p , Sr2+ could replace Ca2+, but Mn2+, Mg2+ and Ba2+ could not. External pH affected(I m ) p and the membrane conductance (g m ) at(I m ) p ((g m ) p ). Increasing the external ionic strength caused increases in both(I m ) p and(g m ) p , and shifted(V m ) p to positive values. At the same time, Sr2+ influx increased. Thus Ca2+ channel activation seems to be enhanced by increasing external ionic strength. The possible involvement of surface potential is discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1424
    Keywords: Ca2+ channel ; Characeae ; membrane excitation ; Nitellopsis ; phosphoprotein phosphatase ; protein phosphorylation ; tonoplast-free cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The regulation of voltage-dependent Ca2+ channels by protein phosphorylation and dephosphorylation was studied using tonoplast-free cells ofNitellopsis. Since the Ca2+-channel activation has a dominant role in the membrane excitation of tonoplast-free cells (T. Shiina and M. Tazawa,J. Membrane Biol. 96:263–276, 1987), it seems to be reasonable to assume that any change of the membrane excitability reflects a modulation of the Ca2+ channel. When agents that enhance phosphoprotein dephosphorylation (protein kinase, inhibitor, phosphoprotein phosphatase-1, -2A) were introduced to the intracellular surface of the plasmalemma (twice-perfused tonoplast-free cells), the membrane potential depolarized and the membrane resistance decreased under current-clamp experiments. By contrast, when cells were challenged with agents that enhance protein phosphorylation (phosphoprotein phosphatase inhibitor-1, α-naphthylphosphate), the membrane potential hyperpolarized, and the membrane resistance increased. When phosphoprotein phosphatase-1 or -2A was perfused, the current-voltage (I–V) curve which was obtained under ramp voltage-clamp condition exhibited the so-called N-shaped characteristic, indicating an acceleration of the Ca2+-channel activation. This effect was suppressed by the addition of phosphoprotein phosphatase inhibitors. ATP-γ-S, which is assumed to stimulate protein phosphorylation, decreased the inward current in theI–V curve. The dependence of the Ca2+-channel activation on intracellular ATP was different between the once-perfused and twice-perfused cells. In once-perfused cells, the membrane excitability was reduced by low intracellular ATP concentration. By contrast, in twice-perfused cells, excitability was enhanced by ATP.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    The journal of membrane biology 99 (1987), S. 137-146 
    ISSN: 1432-1424
    Keywords: Ca2+-activated Cl− channel ; Ca2+ channel ; Characeae ; Cl− efflux ; membrane excitation ; Nitellopsis obtusa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The mechanisms of Cl−-channel activation in the plasmalemma ofNitellopsis obtusa was studied by measuring both the transient inward current under voltage clamp and Cl− efflux during the action potential. 9-anthracenecarboxylic acid (A-9-C) at 1.0mm inhibited both the transient inward current and the Cl− efflux, but did not uncouple the sudden cessation of the cytoplasmic streaming. Since this excitation-cessation coupling is caused by a transient increase in the cytoplasmic Ca2+ concentration, these results suggest that A-9-C inhibited not the Ca2+ channel but specifically the Cl− channel. The following results were found between the Ca2+-channel activation and the Cl−-channel activation: (1) The Ca2+-channel blocker La3+ uncoupled the excitation-cessation coupling and inhibited both the transient inward current and the Cl− efflux, although the Cl−-channel blocker A-9-C did not affect the excitation-cessation coupling. (2) The Cl− efflux was greatly reduced by depletion of Ca2+ from the external solution and restored by an increase in the external Ca2+ concentration. (3) An increase in the external ionic, strength which increases Ca2+ entry (T. Shiina & M. Tazawa,J. Membrane Biol. 96:263–276, 1987) enhanced the Cl− efflux. (4) Mg2+, which cannot pass through the Ca2+ channel, reduced both the transient inward current and the Cl− efflux. (5) Although Sr2+ can pass through the plasmalemma Ca2+ channel, Cl−-channel activation by Sr2+ was only partial. These findings support the hypothesis that voltage-dependent Ca2+-channel activation, which increases the free Ca2+ concentration in the cytoplasm, is necessary for the subsequent Cl−-channel activation.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1211
    Keywords: Key words B3GALT4 ; Mapping ; MHC ; ¶Sequencing ; T/t complex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 66 (2001), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Electrical conductivity was investigated in relation to percent pared fruit or damage indexes prepared by manually paring strawberries and stimulating bruising with a 3-dimensional vibrator. The conductivity was associated with the percent pared fruit (0 to 40%) or damage indexes (1 to 5) of strawberries, with correlation coefficients of 0.938 and 0.917 at P 〈 0.05, respectively. Furthermore, the bruising caused by the 3-dimensional vibrator resulted in increases in electrical conductivity in response to vibrating time and vibrating force. The decrease in electrical conductivity of strawberries treated with the vibrator during 2 d of storage at 25 °C and 80% relative humidity may be due to wound healing of the fruit. Electrical conductivity exhibited potential for quantitatively evaluating damage of strawberries during transportation and marketing.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0375-9474
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Bioenergetics 1142 (1993), S. 36-42 
    ISSN: 0005-2728
    Keywords: FTIR ; Photosystem II ; Plastoquinone-9 ; Primary quinone acceptor ; Q"A ; Reconstitution
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0014-5793
    Keywords: L protein ; Photosystem II ; Plastoquinone-9 ; Q"A ; psbL
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 134 (1986), S. 60-61 
    ISSN: 1615-6102
    Keywords: Membrane excitation ; Nitellopsis obtusa ; Protein phosphorylation ; Tonoplast-free cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 229 (1991), S. 334-340 
    ISSN: 1617-4623
    Keywords: Principal sigma factor ; rpoD genes ; Sequence homology ; Streptomyces coelicolor ; Open reading frame
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The complete nucleotide sequences were determined of hrdA, hrdC, and hrdD from Streptomyces coelicolor A3(2). They indicate the presence of a single open reading frame in each gene coding for polypeptides of 396 (43747 daltons), 339 (38173 daltons), and 332 amino acid residues (37190 daltons), respectively. These amino acid sequences revealed extensive similarities with the principal sigma factors of Bacillus subtilis, Escherichia coli, Mxyococcus xanthus, Pseudomonas aeruginosa, and also the katF gene product of E. coli. Besides the highly conserved amino acid residues in the ”rpoD box” region, alignment of hrd gene products and the known principal sigma factors and sigma-related factors allowed us to postulate a common basic structure for the principal sigma type factors as distinct from the alternative sigma factors.
    Type of Medium: Electronic Resource
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