Orientation of paramecium swimming in a static magnetic field: Dependence on membrane lipid fluidity.

We studied the swimming orientation of the ciliated protozoan Paramecium aurelia in a static magnetic field (0.78 T). P.

Thermo-sensitive response based on the membrane fluidity adaptation in Paramecium multimicronucleatum.

Relationships between the thermo-sensitive response and membrane lipid fluidity were studied using a ciliated protozoan, Paramecium multimicronucleatum. Paramecium elicits a transient membrane depolarization in response to a cooling stimulus (temperature drop). The depolarization amplitude was largest when the cooling stimulus was started from the culture temperature, whilst when cooling started at a temperature more than 5 degrees C higher or lower than the culture temperature, only a small depolarization was induced.

Spontaneous fluctuation of the resting membrane potential in Paramecium: amplification caused by intracellular Ca2+.

The ciliated protozoan Paramecium spontaneously changes its swimming direction in the absence of external stimuli. Such behavior is based on resting potential fluctuations, the amplitudes of which reach a few mV. When the resting potential fluctuation is positive and large, a spike-like depolarization is frequently elicited that reverses the beating of the cilia associated with directional changes during swimming.

Calcium regulates independently ciliary beat and cell contraction in Paramecium cells.

Intracellular Ca(2+) concentration is a well-known signal regulator for various physiological activities. In many cases, Ca(2+) simultaneously regulates individual functions in single cells. How can Ca(2+) regulate these functions independently? In Paramecium cells, the contractile cytoskeletal network and cilia are located close to each other near the cell surface.

Correlation between thermotolerance and membrane properties in Paramecium aurelia.

The relationship between thermotolerance and membrane properties was studied by using a ciliated protozoan, Paramecium aurelia. P. aurelia is a complex of sibling species termed ;syngens' whose cell morphology appear similar on microscopic examination.

Photosensitive signal transduction induces membrane hyperpolarization in Paramecium bursaria.

The protozoan ciliate Paramecium bursaria exhibits membrane hyperpolarization in response to photostimulation, accompanied with an increased swimming speed. The external addition of cyclic nucleotide phosphodiesterase (PDE) inhibitors, either theophylline (1,3-dimethylxanthine) or 3-isobutyl-1-methylxanthin (IBMX), increased in both amplitudes of the membrane hyperpolarization and the increase in swimming speed. Moreover, the addition of membrane permeable cyclic nucleotide analogs, either 8-bromo-adenosine 3',5'-cyclic monophosphate (Br-cAMP) or 8-Br-guanosine 3',5'-cyclic monophosphate (Br-cGMP), increased these amplitudes.

Halteria grandinella: a rapid swimming ciliate with a high frequency of ciliary beating.

A ciliated protozoan, Halteria grandinella, swam backward rapidly with a migration distance per second attaining 100 times the cell size. This high swimming velocity was accompanied by a high frequency of ciliary beating. Recordings with a high-speed digital video (10(3) frames/s) revealed that the frequency during forward and backward swimming was, respectively, 105 +/- 10 Hz and 260 +/- 30 Hz.

Paramecium decaurelia and Paramecium dodecaurelia from the P. aurelia spp. complex in Japan.

The presence of Paramecium decaurelia (three strains) and Paramecium dodecaurelia (two strains) were recorded in Japan, for the first time in this country and outside the USA.

Cell division induced by mechanical stimulation in starved Tetrahymena thermophila: cell cycle without synthesis of macronuclear DNA.

Starved Tetrahymena thermophila cells underwent synchronous cell division 2 h after a mechanical stimulation. The macronucleus showed no obvious increase in DNA content before the cell division in the starvation medium, and the DNA content was decreased after the cell division. On the other hand, when the starved cells were given nutrient-supplied medium immediately after the mechanical stimulation, cell division was delayed for 3 h.

Analysis of anisotropic diamagnetic susceptibility of a bull sperm.

Bull sperm and paramecium cilium were exposed to uniform static magnetic fields to observe their magnetic orientations and measure their anisotropic diamagnetic susceptibility (deltachi) for each. The prepared samples were whole bull sperm, bull sperm flat heads, and paramecium cilia, because bull sperm tails in a perfect condition could not be prepared. The whole bull sperm and the bull sperm heads became oriented perpendicular to the magnetic fields (1.

External GTP binding and induction of cell division in starved Tetrahymena thermophila.

The extracellular nucleotide, guanosine 5'-triphosphate (GTP) is known to be a chemorepellent for ciliated protozoa such as Paramecium and Tetrahymena. Here, we studied the surface localization of GTP binding sites and also its effects on the cell division of Tetrahymena thermophila. When a ribose-modified and fluorescent analog of GTP, 2'-(or -3')-O-trinitrophenyl (TNP)-GTP was added to the cells starved in non-nutrient buffer, a remarkable fluorescence was observed at the compound cilia of the oral area, while it was weak at other cilia and the somatic membrane.

Orientation of paramecium swimming in a DC magnetic field.

We found that a ciliated protozoan, Paramecium, swam perpendicular to a static (DC) magnetic field (0.68 T). The swimming orientation was similar even when the ionic current through the cell membrane disappeared after saponin treatment.