Kenjiro Yoshimura

Learn More
Ciliates and flagellates temporarily swim backwards on collision by generating a mechanoreceptor potential. Although this potential has been shown to be associated with cilia in Paramecium, the molecular entity of the mechanoreceptor has remained unknown. Here we show that Chlamydomonas cells express TRP11, a member of the TRP (transient receptor potential)(More)
Many free-swimming unicellular organisms show negative gravitaxis, i.e. tend to swim upward, although their specific densities are higher than the medium density. To obtain clues to the mechanism of this behavior, we examined how a mutation in motility or behavior affects the gravitaxis in Chlamydomonas. A phototaxis mutant, ptx3, deficient in membrane(More)
Cilia and flagella can alter their beating patterns through changes in membrane excitation mediated by Ca(2+) influx. The ion channel that generates this Ca(2+) influx and its cellular distribution have not been identified. In this study, we analyzed the Chlamydomonas ppr2 mutant, which is deficient in the production of a flagellar Ca(2+) current and(More)
In the mechanism underlying the phototactic behavior of Chlamydomonas, Ca(2+) has been thought to control the dominance between the two flagella so as to steer the cell to correct directions. A newly isolated mutant, lsp1, that displays weak phototaxis was found to be defective in this Ca(2+)-dependent shift in flagellar dominance; in demembranated and(More)
Conventional high-temperature reactions limit the control of coordination polyhedra in transition-metal oxides to those obtainable within the bounds of known coordination geometries for a given transition metal. For example, iron atoms are almost exclusively coordinated by three-dimensional polyhedra such as tetrahedra and octahedra. However, recent works(More)
The heads of demembranated spermatozoa of the sea urchin Tripneustes gratilla, reactivated at different concentrations of ATP, were held by suction in the tip of a micropipette and vibrated laterally with respect to the head axis. This imposed vibration resulted in a stable rhythmic beating of the reactivated flagella that was synchronized to the frequency(More)
Mechanosensitive channels appear ubiquitous but they have not been well characterized in cells directly responding to mechanical stimuli. Here, we identified tension-sensitive channel currents on the cell body of Chlamydomonas, a protist that shows a marked behavioral response to mechanical stimulation. When a negative pressure was applied to the cell body(More)
The unicellular green alga Chlamydomonas displays two distinct kinds of behavioral response to light: phototaxis, in which cells swim toward or away from the light source under constant illumination; and photophobic responses (also called stop responses or photoshock responses), in which cells transiently convert their flagellar waveform and swim backward(More)
Cells actively regulate the macromolecular excluded volume of the cytoplasm to maintain the reciprocal fraction of free aqueous solution that is optimal for intracellular processes. However, the mechanisms whereby cells sense this critical parameter remain unclear. The mechanosensitive channel of small conductance (MscS channel), which is the major(More)
We have studied the phase component of flagellar beating by holding the head of a sea urchin sperm in the tip of a sinusoidally vibrating micropipet and then abruptly displacing the pipet laterally at a speed of 2.5 microns/ms for various durations. This rapid displacement of the pipet delayed the initiation of the next bend for as long as the displacement(More)