Koji Taneda

PHOTORECEPTOR PIGMENT IN Blepharisma: H+ RELEASE FROM RED PIGMENT

In faded cells of Blepharisma kept in a standard saline solution containing bacteria which had been cultured on agar plates containing glucose and polypepton, threshold light intensity for step‐up photophobic response elevated. This result suggests that red pigment (blepharismin) contained in Blepharisma cells is involved in the step‐up photophobic response. The pH of the aqueous solution of the red pigment was found to decrease when light was applied, indicating that the pigment releases H+ in response to light stimulation. However, faded pigment preparation by light irradiation did not show pH decrease. In the living cells faded by light irradiation, threshold light intensity for the step‐up photophobic response was raised. Results suggest that H+ release from the red pigment induced by light irradiation might be responsible for the step‐up photophobic response of the cells.

Seasonal changes in alary dimorphism of a water strider, Gerris paludum insularis (Motschulsky)

Abstract The water strider, Gerris paludum insularis (Motschulsky) shows trivoltinism in Kochi, Japan. The first generation of offspring growing in May and June show a higher proportion of brachypterous adults than the other generations. In the second generation of offspring growing in August and Deptember more macropterous adults appear than in the other generations. A long-day photoperiod (14.5 h light-9.5 h dark) during the whole nymphal stage causes more adults to be brachypterous than a short-day photoperiod of 12 or 9.5 h light each day. Only under a short-day photoperiod (12 h light), is a significant effect of temperature observed: a high temperature (30 ± 2°C) induces a higher proportion of macropterous adults than a low temperature (20 ± 2°C).

Studies on the mechanism of cell elongation in Blepharisma japonicum I. A physiological mechanism how light stimulation evokes cell elongation.

In a heterotrichous ciliate, Blepharisma japonicum, longitudinal elongation of the cell body is induced by light stimulation (1000 to 3000 lux). This light-induced response was inhibited under the existence of cyclic mononucleotide phosphodiesterase (PDE) antagonists such as papaverine (10(-4)M), theophylline (10(-3) M), dibutyril-cAMP (10(-4)M), 3-isobutyl-1-methyl-xanthine (10(-4) M) and dibutyril-cGMP (10(-4) M). Microinjection of cyclic mononucleotides, especially cGMP, inhibited cell elongation. These observations suggest that the cell elongation was mediated by intracellular cyclic mononucleotide. K(+) specific ionophore valinomycin (10(-8)-10(-7) M) enhanced light-induced cell elongation. This effect of valinomycin became more remarkable when valinomycin coexisted with PDE antagonists, while it was diminished under high K+ conditions. Moreover, the K(+) channel blockers tetraethylammonium (TEA) and CsCl inhibited cell elongation. These observations suggest that the cell elongation is also mediated by K(+) hyperpolarization, and that this electrical change is probably elicited after the intracellular concentration of cyclic mononucleotide decreased.

Cell models of Blepharisma : Ca2+-dependent modification of ciliary movement and cell elongation

Ionic mechanisms were examined with reference to modification of swimming velocity and cell elongation in Triton-extracted cell models of Blepharisma. The extracted cells swam forward at Ca(2+) concentrations below 10(-6) M. The forward swimming velocity of the cell models increased with a decreased Ca(2+) concentration in the surrounding medium. At Ca(2+) concentrations above 10(-6) M, the models swam backward or rotated. The elongation of the models occurred at Ca(2+) concentrations below 10(-7) M. Results suggest that swimming velocity, cell elongation and contraction of intact cells may be regulated by intracellular Ca(2+) concentration.

Analysis of motile tracks of Paramecium under gravity field

Abstract Two-dimensional swimming tracks of paramecia on the vertical plane were photographed by 4-sec exposure under a dark field. The orientation rate (meaning the degree of upward curvature of the swimming path) was measured under various experimental conditions. The rate decreased in a K-rich medium as well as in a viscous methylcellulose solution. The decreasing tendency of the orientation rate was closely coupled with that of swimming velocity. The rate was also decreased in a solution with a high specific gravity which was made up by heavy water. The specimen did not show geotactic orientation either during or just after the application of an electric current. The motile behavior of the individual specimen under gravity, which was recorded on videotape, showed that a larger angular change in the cell axis was always coupled with an upswing phase of the gyration. The theoretical equations of motion for physical models were set up, and the most probable mechanism was discussed on the basis of the present findings.

Studies on the mechanism of cell elongation in Blepharisma japonicum: 3. Cytoplasmic calcium ions may correlate to cell elongation in calmodulin-dependent manner

Among many heterotrichous ciliates, Blepharisma japonicum especially demonstrates negative phototaxis in response to light stimulation, which is attributed to be caused by swimming acceleration accompanied by cell elongation and ciliary reversal. When Blepharisma cells were treated with 0.1 mM EGTA, cell elongation gradually decreased in its degree as the adaptation time lapsed. Calmodulin inhibitors such as W-7 (10(-5) M) and chlorpromazine (10(-5) M) inhibited cell elongation. These results suggest that a rise in cytoplasmic free Ca(2+) concentration might cause cell elongation through the Ca-calmodulin system. On the other hand, Ca(2+)-channel blockers (La(3+), Co(2+), Cd(2+), Zn(2+), Mn(2+) and verapamil) did not inhibit cell elongation. Ca2+ localization examined by calcium pyroantimonate cytochemistry suggests that Ca(2+) ions required for cell elongation might be supplied from the vacuoles located in the cortical region of the cell instead of Ca(2+) influx from the surrounding medium.

Certain components of lettuce juice modify the thermoresponse of the ciliated protozoan Blepharisma japonicum

When the cells of Blepharisma cultured in lettuce juice were transferred to media containing lettuce juice with temperature gradient of 20–30°C, they accumulated in a region corresponding to about 25°C. The cells washed in a saline solution, however, accumulated in the region above 30°C. The results indicate that certain components contained in lettuce juice change the thermosensitivity of the cells. When the temperature was suddenly changed, a transient decrease or increase in the frequency of ciliary reversal was observed. The response of the cells incubated in a saline solution without lettuce juice was different from those in the saline solution containing lettuce juice above 25°C. Above 25°C, the cells incubated in a saline solution without lettuce juice responded by increased frequency of ciliary reversal only to step-down in temperature and by repression of ciliary reversal to a step-up in temperature, while the cells incubated in the same saline solution containing lettuce juice responded by increased frequency of ciliary reversal to a step-up in temperature and by repression of ciliary reversal to a step-down in temperature. The thermal response was examined in bisected fragments of the cells. The difference in response between the saline solution without lettuce juice and the solution containing lettuce juice was detected only in posterior fragments above 25°C. Above 25°C, the posterior fragments incubated in the solution without lettuce juice did not respond to sudden temperature changes, whereas the fragments kept in the medium containing lettuce juice responded (step-up thermophobic response and step-down repression of ciliary reversal) in the presence of lettuce juice.