Abstract
We present a simple device to mechanically immobilize motile cells such as ciliates. It can be used in particular for intracellular electrophysiology and microinjection. A transparent filter with holes smaller than the specimen is stretched over an outlet. A flow is induced by either a peristaltic pump or a depressurized tank, mechanically entraining cells to the bottom, where they are immobilized against the filter. The cells start swimming again as soon as the flow is stopped. We demonstrate the device by recording action potentials in Paramecium and injecting a fluorescent dye into the cytosol.
Highlights
Paramecium is a well-studied ciliate that swims in freshwater and feeds on smaller microorganisms (Görtz, 1988; Wichterman, 1986)
Its motility is electrically controlled by calcium-based action potentials: various types of sensory stimulation can depolarize the cell and trigger an action potential, and the entry of calcium leads to the reversal of ciliary beating, making the cell swim backwards (Eckert, 1972)
Intracellular electrophysiology in ciliates such as Paramecium and Tetrahymena was performed with the hanging droplet method (Hennessey and Kuruvilla, 1999; Naitoh and Eckert, 1972)
Summary
Paramecium is a well-studied ciliate that swims in freshwater and feeds on smaller microorganisms (Görtz, 1988; Wichterman, 1986). Its motility is electrically controlled by calcium-based action potentials: various types of sensory stimulation (mechanical, thermal, chemical) can depolarize the cell and trigger an action potential, and the entry of calcium leads to the reversal of ciliary beating, making the cell swim backwards (Eckert, 1972). Sensory stimuli may hyperpolarize the cell, which leads to an increase in swimming speed. This makes Paramecium an interesting model organism for the study of sensorimotor mechanisms (Kung and Saimi, 1982; Hinrichsen and Schultz, 1988; Machemer, 2001) – some authors called it a ‘swimming neuron’ (Kung and Saimi, 1985).
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