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Caffeine-induced Ca2+ transients and exocytosis in paramecium cells : a correlated Ca2+ imaging and quenched-flow/freeze-fracture analysis

Caffeine-induced Ca2+ transients and exocytosis in paramecium cells : a correlated Ca2+ imaging and quenched-flow/freeze-fracture analysis

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KLAUKE, Norbert, Helmut PLATTNER, 1998. Caffeine-induced Ca2+ transients and exocytosis in paramecium cells : a correlated Ca2+ imaging and quenched-flow/freeze-fracture analysis. In: Journal of Membrane Biology. 161(1), pp. 65-81. ISSN 0022-2631. eISSN 1432-1424. Available under: doi: 10.1007/s002329900315

@article{Klauke1998Caffe-7785, title={Caffeine-induced Ca2+ transients and exocytosis in paramecium cells : a correlated Ca2+ imaging and quenched-flow/freeze-fracture analysis}, year={1998}, doi={10.1007/s002329900315}, number={1}, volume={161}, issn={0022-2631}, journal={Journal of Membrane Biology}, pages={65--81}, author={Klauke, Norbert and Plattner, Helmut} }

<rdf:RDF xmlns:dcterms="http://purl.org/dc/terms/" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:bibo="http://purl.org/ontology/bibo/" xmlns:dspace="http://digital-repositories.org/ontologies/dspace/0.1.0#" xmlns:foaf="http://xmlns.com/foaf/0.1/" xmlns:void="http://rdfs.org/ns/void#" xmlns:xsd="http://www.w3.org/2001/XMLSchema#" > <rdf:Description rdf:about="https://kops.uni-konstanz.de/rdf/resource/123456789/7785"> <dcterms:issued>1998</dcterms:issued> <dcterms:hasPart rdf:resource="https://kops.uni-konstanz.de/bitstream/123456789/7785/1/Caffeine_induced_Ca2.pdf"/> <dc:contributor>Plattner, Helmut</dc:contributor> <dc:rights>deposit-license</dc:rights> <dc:creator>Plattner, Helmut</dc:creator> <dcterms:abstract xml:lang="deu">Caffeine causes a [Ca2+]i increase in the cortex of Paramecium cells, followed by spillover with considerable attenuation, into central cell regions. From [Ca2+]resti 50 to 80 nm, [Ca2+]acti rises within ≤3 sec to 500 (trichocyst-free strain tl) or 220 nm (nondischarge strain nd9 28°C) in the cortex. Rapid confocal analysis of wildtype cells (7S) showed only a 2-fold cortical increase within 2 sec, accompanied by trichocyst exocytosis and a central Ca2+ spread during the subsequent ≥2 sec. Chelation of Ca2+o considerably attenuated [Ca2+]i increase. Therefore, caffeine may primarily mobilize cortical Ca2+ pools, superimposed by Ca2+ influx and spillover (particularly in tl cells with empty trichocyst docking sites). In nd cells, caffeine caused trichocyst contents to decondense internally (Ca2+-dependent stretching, normally occurring only after membrane fusion). With 7S cells this usually occurred only to a small extent, but with increasing frequency as [Ca2+]i signals were reduced by [Ca2+]ochelation. In this case, quenched-flow and ultrathin section or freeze-fracture analysis revealed dispersal of membrane components (without fusion) subsequent to internal contents decondensation, opposite to normal membrane fusion when a full [Ca2+]i signal was generated by caffeine stimulation (with Ca2+i and Ca2+o available). We conclude the following. (i) Caffeine can mobilize Ca2+ from cortical stores independent of the presence of Ca2+o. (ii) To yield adequate signals for normal exocytosis, Ca2+ release and Ca2+ influx both have to occur during caffeine stimulation. (iii) Insufficient [Ca2+]i increase entails caffeine-mediated access of Ca2+ to the secretory contents, thus causing their decondensation before membrane fusion can occur. (iv) Trichocyst decondensation in turn gives a signal for an unusual dissociation of docking/fusion components at the cell membrane. These observations imply different threshold [Ca2+]i-values for membrane fusion and contents discharge.</dcterms:abstract> <dcterms:bibliographicCitation>First publ. in: Journal of Membrane Biology 161 (1998), 1, pp. 65-81</dcterms:bibliographicCitation> <dc:language>deu</dc:language> <dcterms:isPartOf rdf:resource="https://kops.uni-konstanz.de/rdf/resource/123456789/28"/> <dcterms:available rdf:datatype="http://www.w3.org/2001/XMLSchema#dateTime">2011-03-24T17:37:31Z</dcterms:available> <dcterms:rights rdf:resource="https://creativecommons.org/licenses/by-nc-nd/2.0/legalcode"/> <dc:format>application/pdf</dc:format> <void:sparqlEndpoint rdf:resource="http://localhost/fuseki/dspace/sparql"/> <dspace:isPartOfCollection rdf:resource="https://kops.uni-konstanz.de/rdf/resource/123456789/28"/> <dcterms:title>Caffeine-induced Ca2+ transients and exocytosis in paramecium cells : a correlated Ca2+ imaging and quenched-flow/freeze-fracture analysis</dcterms:title> <dc:contributor>Klauke, Norbert</dc:contributor> <dspace:hasBitstream rdf:resource="https://kops.uni-konstanz.de/bitstream/123456789/7785/1/Caffeine_induced_Ca2.pdf"/> <dc:date rdf:datatype="http://www.w3.org/2001/XMLSchema#dateTime">2011-03-24T17:37:31Z</dc:date> <bibo:uri rdf:resource="http://kops.uni-konstanz.de/handle/123456789/7785"/> <foaf:homepage rdf:resource="http://localhost:8080/jspui"/> <dc:creator>Klauke, Norbert</dc:creator> </rdf:Description> </rdf:RDF>

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