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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 422 (1993), S. 325-331 
    ISSN: 1432-2013
    Keywords: Myocyte ; Voltage clamp ; Ionic currents ; Oximes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Exposure of isolated guinea-pig ventricular myocytes to the uncharged oximes 2,3 butanedionemonoxine (BDM) and norPAM (but not by the charged PAM) results in a dose-dependent reduction of the duration of the action potential. The nifedipine-sensitive Ca current is fully inhibited by BDM (IC505.8±0.4 mM) and nor PAM but is little affected by PAM. This inhibition is unaltered by the presence of BAY K 8644 but is antagonized by isoprenaline. The effect of isoprenaline is more pronounced when the solution in the patch pipette contains the non-hydrolysable analogue of adenosine 5′-triphosphate, ATPγS (the IC50 is increased to 44.0±5.2 mM). A hastening of the inactivation of the L-type Ca current persists when either 10 mM 1,2-bis(2-aminophenoxy)-ethane-N, N, N′, N-tetraacetic acid (BAPTA) or 3 mM ATPγS is present in the pipette solution or when BAY K 8644 or isoprenaline are present in the bathing fluid. These results suggest that the inhibition of the Ca current is due to the phosphatase-like activity of the oximes but differs in some respects from previous work where a reduced level of phosphorylation is achieved by the introduction of protein kinase inhibitors or protein phosphatases into the sarcoplasm in guinea-pig myocytes. These differences could be explained if Ca channel availability is regulated by at least two sites of cAMP-dependent phosphorylation with oximes able to rapidly dephosphorylate both sites, while one of these sites is not readily dephosphorylated by the endogenous phosphatases.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2013
    Keywords: Myocyte ; Intracellular ions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A method for the manufacture of ion-sensitive micro-electrodes, which can be readily used with small single cells, is described in detail. A glass pipette with a tip size of 1 μm, essentially similar to those used as suction electrodes in whole-cell recording, when silanized and with its tip filled with a suitable ion-sensitive resin, producesan ion-sensitive electrode with fast electrical and chemical response times. These electrodes can be applied to the cell membrane of isolated myocytes and penetration achieved without cell damage, by the application of suction. For the estimation of intracellular ionic activities they can be used in conjunction with a separate conventional KCl-filled micro-electrode or a suction voltage electrode. The technique is illustrated by the measurement of intracellular Na+, Ca2+ and pH. It is possible that these electrodes can also be used to measure local changes in ionic activity in restricted areas.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 55 (1990), S. 205-212 
    ISSN: 1570-7458
    Keywords: Olfactory sensitivity ; grasshoppers ; electroantennogram ; Larrea ; hostplant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé Les réponses antennaires ont été examinées par électroantennogramme aux odeurs de plantes hôtes et non hôtes d'orthoptères Gomphocerinae de comportements alimentaires différents: Bootettix argentatus, monophage sur une dicotylédone, Larrea; Ligurotettix coquilletti, oligophage de dicotylédones; Cibolacris parviceps, polyphage; Chorthippus curtipennis, graminivore. Les types de réponse des quatre espèces étaient très voisins, mais les réponses aux odeurs de Larrea de B. argentatus et L. coquilletti, spécialistes de cette plante, étaient relativement plus fortes. Ces résultats suggèrent une similarité globale considérable dans la composition des populations de récepteurs olfactifs de ces quatre espèces d'orthoptères mais aussi une certaine spécificité pour les odeurs de la plante hôte au niveau antennaire.
    Notes: Abstract Antennal responses to host and non-host odours were recorded, using the electroantennogram technique, from four gomphocerine grasshoppers with different feeding habits: Bootettix argentatus (monophagous on Larrea, a dicotyledonous plant), Ligurotettix coquilletti (oligophagous on dicotyledonous plants), Cibolacris parviceps (polyphagous) and Chorthippus curtipennis (graminivorous). The patterns of responses across the plant odours were similar for all four grasshopper species, but there was a relatively greater response to the odour of Larrea in B. argentatus and L. coquilletti which specialise on this plant. This suggests that there is considerable overall similarity in the make up of the olfactory receptor populations of these four grasshoppers species, but that some specificity for hostplant odour does exist at the antennal level.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 14 (1988), S. 561-579 
    ISSN: 1573-1561
    Keywords: Creosote bush ; Larrea ; nordihydroguaiaretic acid ; grasshoppers ; monophagy ; Bootettix ; Ligurotettix ; Cibolacris ; Orthoptera ; Acrididae ; host selection ; feeding deterrence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The host-selection behavior of three species of grasshopper feeding on creosote bush,Larrea tridentata, in southern California was investigated. The species wereBootettix argentatus, which is monophagous;Ligurotettix coquilletti, oligophagous; andCibolacris parviceps, polyphagous. The monophagous species is stimulated to bite by nordihydroguaiaretic acid (NDGA), a compound that is characteristic of the host plant and that may comprise up to 10% of the dry weight of the leaf. Host specificity ofB. argentatus is enhanced by deterrent responses to compounds present in the surface waxes of all non-host-plant species. Both the oligophagous and polyphagous species are deterred by NDGA at naturally occurring concentrations. Their association withLarrea is probably based on tolerance of the plant chemicals rather than on dependence on specific chemicals. Factors other than the chemistry of the plant probably also contribute to the specificity ofB. argentatus andL. coquilletti.
    Type of Medium: Electronic Resource
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