These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Electrically induced Ca2+ transport across the membrane of Paramecium caudatum measured by means of flow-through technique.
    Author: Martinac B, Hildebrand E.
    Journal: Biochim Biophys Acta; 1981 Dec 07; 649(2):244-52. PubMed ID: 7317396.
    Abstract:
    Transmembrane calcium fluxes related to excitation were studied in Paramecium caudatum. Radioactive (45Ca2+) or inactive solution was flowed through a dense suspension of unlabelled or labelled cells, and radioactivity was monitored in the solution. The organisms were electrically stimulated by means of extracellular electrodes. As a result of stimulation Ca2+ uptake and release was measured. The uptake response dropped with increasing number of successive stimulation periods and increased with growing stimulus amplitude and duration. Maximum uptake was obtained at 20 V/cm and at least 60 s duration and for temperatures between 10 and 15 degrees C. A Ca2+ influx of 700 pmol/1000 cells upon 1 min stimulation was measured at 15 degrees C. This corresponds to an increment of the intraciliary [Ca2+] of about 5 x 10(-4) M. Ca2+ release was dependent on the stimulus amplitude in a similar manner as was Ca2+ uptake. Photographic recordings of the swimming behaviour of the organisms were used to interpret the flux data. At temperatures up to 15 degrees C the cells swam backward perpendicular to the applied electric field of 10 to 20 V/cm. At 25 degrees C they showed forward spiralling movement. For the first time evidence was brought for stimulated Ca2+ influx in Paramecium at physiological temperatures. It is concluded from the results that a strong active Ca2+ extrusion from the intraciliary space counteracts the influx. The Ca2+ pump rate must be at least 8 x 10(12) calcium ions per s per cm2 ciliary surface.
    [Abstract] [Full Text] [Related] [New Search]