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  • Drosophila melanogaster  (3)
  • membrane currents  (2)
  • 1985-1989  (5)
  • 1975-1979
  • 1935-1939
  • 1890-1899
  • 1
    Electronic Resource
    Electronic Resource
    Effects of fatty acids on membrane currents in the squid giant axon (1987)
    Springer
    The journal of membrane biology 95 (1987), S. 113-120 
    Details
    ISSN: 1432-1424
    Keywords: fatty acids ; membrane currents ; membrane excitation ; 2-decenoic acid ; lateral motion ; squid axon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The effects of fatty acids on the ionic currents of the voltage-clamped squid giant axon were investigated using intracellular and extracellular application of the test substances. Fatty acids mainly suppress the Na current but have little effect on the K current. These effects are completely reversed after washing with control solution. The concentrations required to suppress the peak inward current by 50% and Hill number were determined for each fatty acid. ED50 decreased about 1/3 for each increase of one carbon atom. The standard free energy was −3.05 kJ mole−1 for CH2. The Hill number was 1.58 for 2-decenoic acid. The suppression effect of the fatty acids depends on the number of carbon atoms in the compounds and their chemical structure. Suppression of the Na current was clearly observed when the number of carbon atoms exceeded eight. When fatty acids of the same chain length were compared, 2-decenoic acid had strong inhibitory activity, but sebacic acid had no effect at all on the Na channel. The currents were fitted to equations similar to those proposed by Hodgkin and Huxley (J. Physiol. (London) 117:500–544, 1952) and the changes in the parameters of these equations in the presence of fatty acids were calculated. The curve of the steady-state activation parameter (m ∞) for the Na current against membrane potential and the time constant of activation ({ie113-1}) were shifted 20 mV in a depolarizing direction by the application of fatty acids. The time constant for inactivation ({ie113-2}) was almost no change by application of the fatty acids. The time constant for activation ({ie113-3}) of K current was shifted 20 mV in a depolarizing direction by the application of the fatty acids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01869156
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  • 2
    Electronic Resource
    Electronic Resource
    Positive regulation of theDrosophila melanogaster G6PD gene by an insertion sequence (1989)
    Springer
    Biochemical genetics 27 (1989), S. 379-393 
    Details
    ISSN: 1573-4927
    Keywords: Drosophila melanogaster ; glucose-6-phosphate dehydrogenase (G6PD) ; transposable genetic element ; positive regulation ; chromatin structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract In a previous study, we have shown that the three high-G6PD activity mutants are characterized by insertion of the Ins1 sequence consisting of a core sequence flanked by two defective P elements (KP and KP'; the 32nd base of the KP was replaced by guanine in the KP') in front of exonI of the G6PD gene and that the sequence responsible for positive regulation of the G6PD gene expression might be the core sequence but not the flanking KP and KP' elements. The core sequence is composed of either one or two identical units in each mutant. In this report we present evidence (1) that insertion of the Ins1 sequence gives rise to overproduction of G6PD mRNA, (2) that the length and the 5′ end of G6PD mRNA do not differ in wild-type and three mutants, (3) that the insertion site of the Ins1 sequence is the same in the mutants, and (4) that each unit of the core sequence has a pair of DNase I-hypersensitive sites. The possibility exists that the binding of some regulatory proteins to the DNase I-hypersensitive sites might accelerate the transcription rate of the G6PD gene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00553905
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  • 3
    Electronic Resource
    Electronic Resource
    Positive regulation of theDrosophila melanogaster G6PD gene by an insertion sequence (1989)
    Springer
    Biochemical genetics 27 (1989), S. 379-393 
    Details
    ISSN: 1573-4927
    Keywords: Drosophila melanogaster ; glucose-6-phosphate dehydrogenase (G6PD) ; transposable genetic element ; positive regulation ; chromatin structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract In a previous study, we have shown that the three high-G6PD activity mutants are characterized by insertion of the Ins1 sequence consisting of a core sequence flanked by two defective P elements (KP and KP'; the 32nd base of the KP was replaced by guanine in the KP') in front of exonI of the G6PD gene and that the sequence responsible for positive regulation of the G6PD gene expression might be the core sequence but not the flanking KP and KP' elements. The core sequence is composed of either one or two identical units in each mutant. In this report we present evidence (1) that insertion of the Ins1 sequence gives rise to overproduction of G6PD mRNA, (2) that the length and the 5′ end of G6PD mRNA do not differ in wild-type and three mutants, (3) that the insertion site of the Ins1 sequence is the same in the mutants, and (4) that each unit of the core sequence has a pair of DNase I-hypersensitive sites. The possibility exists that the binding of some regulatory proteins to the DNase I-hypersensitive sites might accelerate the transcription rate of the G6PD gene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02399667
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  • 4
    Electronic Resource
    Electronic Resource
    X-linked mutations that give rise to overproduction of glucose-6-phosphate dehydrogenase in Drosophila melanogaster (1986)
    Springer
    Biochemical genetics 24 (1986), S. 319-327 
    Details
    ISSN: 1573-4927
    Keywords: Drosophila melanogaster ; glucose-6-phosphate dehydrogenase ; X-linked mutation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Two X-linked mutations that give rise to overproduction of glucose-6-phosphate dehydrogenase (G6PD) were found among the progenies of isogenic strains which had been subjected to selection for high G6PD activity. Mapping of the high-activity factor in these mutants was carried out using car Zw B sw males of low G6PD activity. As a result, the factor mapped 0.02–0.04 unit to the left of the Zw locus. The amount of the G6PD gene was also quantitated utilizing a cloned G6PD gene as a probe, but no significant difference was found between the mutants and low-G6PD activity flies which shared the same X, second, and third chromosomes with the mutants. These findings are consistent with our notion that the mutations might be regulatory mutations, possibly resulting from the insertion of a novel class of transposable genetic elements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00502798
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of arachidonic acid and the other long-chain fatty acids on the membrane currents in the squid giant axon (1988)
    Springer
    The journal of membrane biology 106 (1988), S. 141-147 
    Details
    ISSN: 1432-1424
    Keywords: arachidonic acid ; long-chain fatty acids ; membrane currents ; Na channel ; squid axon ; membrane excitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The effects of arachidonic acid and some other long-chain fatty acids on the ionic currents of the voltage-clamped squid giant axon were investigated using intracellular application of the test substances. The effects of these acids, which are usually insoluble in solution, were examined by using α-cyclodextrin as a solvent. α-cyclodextrin itself had no effect on the excitable membrane. Arachidonic acid mainly suppresses the Na current but has little effect on the K current. These effects are completely reversed after washing with control solution. The concentration required to suppress the peak inward current by 50% (ED50) was 0.18mm, which was 10 times larger than that of medium-chain fatty acids like 2-decenoic acid. The Hill number was 1.5 for arachidonic acid, which is almost the same value as for medium-chain fatty acids. This means that the mechanisms of the inhibition are similar in both long- and medium-chain fatty acids. When the long-chain fatty acids were compared, the efficacy of suppression of Na current was about the same value for arachidonic acid, docosatetraenoic acid and docosahexaenoic acid. The suppression effects of linoleic acid and linolenic acid on Na currents were one-third of that of arachidonic acid. Oleic acid had a small suppression effect and stearic acid had almost no effect on the Na current. The currents were fitted to equations similar to those proposed by Hodgkin and Huxley (Hodgkin, A.L., Huxley, A.F. (1952)J. Physiol (London) 117:500–544) and the change in the parameters of these equations in the presence of fatty acids were calculated. The curve of the steady-state activation parameter (m ∞) for the Na current against membrane potential and the time constant of activation (τ m ) were shifted 10 mV in a depolarizing direction by the application of fatty acids. The time constant for inactivation (τ h ) has almost unaffected by application of these fatty acids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01871396
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