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Y Kobatake

Publications and source records attributed to Y Kobatake.

At least 55 records · Page 3Linked to original sources
PubMed1980

Membrane biophysics of chemoreception and taxis in the plasmodium of Physarum polycephalum.

The threshold phenomena observed in chemoreception and taxis of the plasmodium of Physarum polycephalum were analyzed on the basis of physical chemistry. Various physicochemical concepts and rules, e.g. the Schulze-Hardy rule, the lyotropic number and the hydrophobic interactions, were shown to be applicable reasonably well to the physiological functions in Physarum. It was stressed that the structural change of the surface membrane induced by reception of chemical stimuli plays a decisive role in recognition and sensitivity to the external stimuli as well as the appearance of tactic movement in the amoeboid motility of Physarum.

Journal Article↗
PubMed1980

Interpretation by theoretical model of dynamic and steady components in frog gustatory response.

The behavior of dynamic component (slow component) and steady component of the frog glossopharyngeal nerve response to CaCl2, measured in number of impulses firing per second, was examined under various conditions. 1) The magnitude of the dynamic component increased with the flow rate below about 0.3 ml/s, whereas that of the steady component was independent of the flow rate. 2) The magnitude of the dynamic component increased with a rise of temperature between 2.5 and 20 degrees C, whereas that of the steady component was practically independent of temperature. Removal of Ca2+ from the receptor membrane yielded a large dynamic component even at 2.5 degrees C. 3) The treatment of the tongue with procaine led to a large reduction in the magnitude of the dynamic component, whereas the effect of procaine on the steady component was not pronounced. 4) The magnitude of the dynamic component varied with the pH of the stimulating solution, whereas that of steady component was practically independent of a pH between 4.5 and 7.5. The above results were well interpreted by the following reaction scheme: S (stimulus + A (receptor domain) in equilibrium (SA)active in equilibrium (SA) inactive where (SA) active and (SA) inactive are active and inactive complexes.

Action Potentials↗
PubMed1980

Selective suppression of positive chemotaxis in Physarum polycephalum by treatment with rotenone or under anaerobic condition.

The chemotactic motive force of plasmodia of Physarum polycephalum was measured by the double-chamber method. The treatment of plasmodia with 0.1 mM rotenone did not affect the motility of the palsmodia but led to suppression of the chemotaxis toward all the attractants examined (glucose, galactose, c-AMP, KH2PO4). Rotenone treatment did not affect the chemotaxis against repellents (fructose, NaCl). Similar results were obtained when the chemotactic motive force was measured under an anaerobic condition (95% N2-5% CO2).

Anaerobiosis↗
PubMed1980

Contraction rhythm in the plasmodium of Physarum polycephalum: dependence of the period on the amplitude, temperature and chemical environment.

The plasmodium of Physarum polycephalum exhibits a characteristic protoplasmic shuttle streaming and generates periodical tension. We determined the factors which govern the period of the contraction rhythm by measuring isometric tension of the plasmodial strand and the motive force of the protoplasmic streaming under a variety of conditions by changing the size of plasmodia, chemical composition of environment and surrounding temperatures. The results are: (1) The period of contraction rhythm, tau, increased linearly with the amplitude of oscillating tension, F, and was expressed by the following empirical equation when F was lower than a certain critical value, Fc, i.e., tau = aF+tau O. Above Fc, tau stayed at a constant level of tau S. There, a tau O and tau S are numerical constants which are independent of F. A similar relationship is valid for the amplitude of the motive force of the protoplasmic streaming, delta P. (2) Values of tau O were 1.0 min in air and 1.6 min in an aqueous medium and they were independent of temperature. (3) The Arrhenius plots of the parameter "a" exhibited different straight lines in air and in aqueous medium, from which the values of Q10 were determined to be 4.0 and 10, respectively. (4) Lowering of temperature decreased Fc, and eventually diminished it at Tc (= 15 degrees C). (5) The presence of glucose, CaCl2, MgCl2 and NaCl gave the identical tau-F relationship. Applications od D2O and ethanol slowed down the contraction rhythm, while that of KCl accelerated the rhythm. However, all these chemicals did not affect the tau O value. All results described above indicate that the contraction rhythm in the plasmodium is influenced by three components: a limit cycle which is independent of tension generation, a component which is strongly linked to the amplitude of the tension, F, and the part which is independent of the value of F. External factors appear to influence separately these three components of the contraction rhythm.

Cytoplasmic Streaming↗
PubMed1979

Selective modification of positive chemotaxis in the true slime mold Physarum polycephalum by ethylenediaminetetraacetic acid treatment.

The plasmodium of the true slime mold Physarum polycephalum was treated with EDTA or EGTA and the effect of the treatment on the chemotactic response was examined by measuring the chemotactic motive force with the double-chamber method. The results obtained were as follows: (1) The treatment of the plasmodium with 5 mM EDTA (pH 7.0, 20 min) did not give any significant effect on the protoplasmic streaming or motility. (2) The plasmodium treated with EDTA exhibited no chemotactic response to non-electrolyte attractants (D-glucose, D-galactose, D-mannose, and maltose) and negative chemotaxis to electrolyte attractants (cyclic AMP and NaH2PO4). (3) The EDTA treatment gave no effect on the chemotactic response to repellents (D-fructose, NaCl, CaCl2, MgCl2). (4) The EDTA-treated plasmodium exhibited changes in the membrane potential in response to both attractants and repellents as similar to the untreated plasmodium. (5) The treatment of the plasmodium with 5 mM EGTA (pH 7.0, 20 min) gave results similar to those obtained with the EDTA treatment. The results obtained suggested that EDTA (or EGTA) treatment did not affect the receptor sites but modified the transduction mechanism from reception into tactic movement.

Chemotaxis↗
PubMed1979

Electrostatic interaction between merocyanine 540 and liposomal and mitochondrial membranes.

The fluorescence of merocyanine 540 (MC) in liposomal and mitochondrial suspensions was measured under various conditions. Under a given condition, both the amount of dye bound to the membrane and the zeta potential were determined simultaneously. It was found that the fluorescence intensity was proportional to the amount of bound dye and correlated with the zeta potential of particles. The fluorescence intensity was represented quantiatively in terms of the Langmuir adsorption isotherm, when the electrostatic interaction acting between MC and membrane surface was properly taken into account. It was concluded that the changes in MC fluorescence in the liposomal and mitochondrial suspensions are mainly attributed to the changes in the surface potential of the membranes.

Animals↗
PubMed1979

Membrane potential of mitochondria measured with an electrode sensitive to tetraphenyl phosphonium and relationship between proton electrochemical potential and phosphorylation potential in steady state.

The membrane potential of mitochondria was estimated from the accumulation of tetraphenyl phosphonium (TPP+), which was determined with the TPP+-selective electrode developed in the present study. The preparation and some operational parameters of the electrode were described. The kinetics for uptake by mitochondria of TPP+ and DDA+ (dibenzyldimethyl ammonium) were analyzed, and it was found that TPP+ permeated the mitochondrial membrane about 15 times faster than DDA+. The final amounts of accumulation of TPP+ and DDA+ by mitochondria were approximately equal. For the state-4 mitochondria, the membrane potential was about 180 mV (interior negative). Simultaneous measurements of TPP+-uptake and oxygen consumption showed that the transition between states 3 and 4 was detectable by use of the TPP+-electrode. After the TPP+-electrode showed that state-4 was reached, the extra-mitochondrial phosphorylation potential was measured. The difference in pH across the membrane was measured from the distribution of permeant anion, acetate, so as to calculate the proton electrochemical potential. The ratio of extra-mitochondrial phosphorylation potential to proton electro-chemical potential, n was close to 3. This value of n was also found to be 3 when ATP was hydrolyzed under the condition that the respiratory chain was arrested. The implication that n = 3 was discussed.

Adenosine Diphosphate↗
PubMed1979

Gustatory responses of eel palatine receptors to amino acids and carboxylic acids.

The gustatory receptors of the eel palate were found to be extremely sensitive to amino acids and carboxylic acids. The results obtained are as follows: (a) 11 amino acids which are among naturally occurring amino acids elicited responses in the palatine nerve, but 9 amino acids did not elicit a response even at a high concentration. The effect of D-amino acids was always much less than that of their corresponding L-isomers. There was no appreciable difference in the effectiveness of an alpha-amino acid (alpha-alanine) and beta-amino acid (beta-alanine). (b) The threshold concentrations of the most potent amino acids (arginine, glycine) were between 10(-8) and 10(-9) M. A linear relation between the magnitude of the response and log stimulus concentration held for a wide concentration range for all the amino acids examined. (c) The palatine receptors responded sensitively to various carboxylic acid solutions whose pH was adjusted to neutral. The threshold concentrations varied between 10(-4) and 10(-7) M. The magnitude of the response at 10(-2) M increased with an increase of carbon chain length. (d) The extent of cross-adaptation was examined with various combinations of amino acids. A variety of the response patterns showing complete cross-adaptation, no cross-adaptation, or synergetic interaction was observed. The synergetic interaction was also observed when one amino acid below its threshold concentration was added to the other amino acid below its threshold concentration was added to the other amino acid. No cross-adaptation was observed between amino acids and fatty acids. (e) The treatment of the palate with papain led to loss of the responses to arginine, glycine, and histidine without affecting those to proline and acetic acid. The treatment with pronase E eliminated selectively the response to proline. The possibility that the eel gustatory receptors are responsible for sensing food at a distance was discussed.

Adaptation, Physiological↗
PubMed1978

Role of membrane-bound calcium in taste reception of the frog.

1. The frog gustatory responses to various salt stimuli and distilled water were greatly enhanced after the tongue was treated with an alkaline solution containing salts of low concentration. The incubation of the alkali-treated tongue in solution of pH 6.0 containing Ca2+ restored reversibly the behaviour of the gustatory receptor to that before the treatment, while Mg2+ had no ability to do this. 2. The responses to salt stimuli and distilled water were greatly decreased after the tongue was incubated in solutions of pH 5.3 containing Ca2+. 3. On piece of tongue incubated in a solution of pH 5.3 containing 45Ca released a larger amount of 45Ca by the alkali treatment than another piece incubated in pH 7.0. It was concluded that removal of Ca2+ from the gustatory receptor membrane by the alkali treatment led to enhancement of the responses and binding of extra Ca2+ to the membrane by the incubation in acidic CaCl2 solution led to suppression of the responses. We emphasized that a conformational change of the receptor domains plays an important role in the transduction process of the gustatory response.

Action Potentials↗
PubMed1977

Hydrophobicity of biosurfaces as shown by chemoreceptive thresholds in Tetrahymena, Physarum and Nitella.

Responses (chemotaxis and changes in membrane potential) of Tetrahymena, Physarum, and Nitella against aqueous solution of homologous series of n-alcohols, n-aldehydes and n-fatty acids were studied for clarifying the hydrophobic character of chemoreceptive membranes. Results were: (1) All organisms studied responded to homologous compounds examined when the concentration of these chemicals exceeded their respective threshold, Cth, and the response, R, were expressed approximately as R=alpha log (C/Cth) for C greater than Cth. (2) Increase of the length of hydrocarbon chain in homologues decreased Cth. Plots of log Cth against the number of carbon atoms, n, in n-alcohols, n-aldehydes and n-fatty acids showed linear relationships as represented by long Cth=-An+B. A and B are positive constants for respective functional end groups of the chemicals and biological membranes used. The above empirical equation was interpreted in terms of the partition equilibrium of methylene groups between bulk solution and membrane phase. Parameter A was shown to be a measure of hydrophobicity of the membrane, and B represented the sensitivity of chemoreception of the membrane. (3) Thresholds, Cth, for various hydrophobic reagents were compared with those of human olfactory reception, T. Plots of log T against log Cth fell on straight lines for respective organisms with different slopes which were proportional to parameter A.

Alcohols↗