title: Gravity effects on Paramecium cells: An analysis of a possible sensory function of trichocysts and of simulated weightlessness on trichocyst exocytosis.
abstract: The structures and mechanisms involved in gravity perception and reaction are generally not known in animal cells, even in protozoa capable of gravitactic behaviour. To study the possible role of trichocysts in graviperception of Paramecium we analysed strains with a different set-up of trichocysts (absence, free floating or attached to the cell membrane) for their gravitactic behaviour. However, all strains investigated showed negative gravitaxis which was demonstrated a) by their capability to perform bioconvection and b) by the analysis of their swimming paths examined by computer analysis in a horizontal microscope. Furthermore, quantitative evaluation of cells (capable of exocytosis but without adding a chemical stimulus for exocytosis) by electron microscopy gave the same organisation with regard to trichocyst contents, regardless whether cells were exposed to 0 g or 1 g. Therefore, any role of trichocysts in graviperception can be denied and other possible gravireceptors might be discussed. Finally we show that simulated weightlessness (0 g) has no effect on exocytosis performance which is one of the basal capabilities of cells. This has been shown with a fast-rotating clinostat microscope using a new set-up for exposing cells under 0 g-conditions to a chemical trigger agent.
authors.affiliation: Institute for Botany and Pharmaceutic Biology, University of Erlangen, Erlangen, FRG.
authors.forename: R
authors.initials: R
authors.lastname: Hemmersbach-Krause
authors.forename: W
authors.initials: W
authors.lastname: Briegleb
authors.forename: D P
authors.initials: DP
authors.lastname: Häder
authors.forename: H
authors.initials: H
authors.lastname: Plattner