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Y Kobatake

Publications and source records attributed to Y Kobatake.

At least 37 records · Page 2Linked to original sources
PubMed1984

Effect of salt on photocycle and ion-pumping of halorhodopsin and third rhodopsinlike pigment of Halobacterium halobium.

The cytoplasmic membranes of Halobacterium halobium contain at least three retinal pigments: bacteriorhodopsin (bR), halorhodopsin (hR), and a third rhodopsinlike pigment (tR). The amplitudes of the phototransient in the photolysis of hR and tR were measured in various salt solutions. Halogen ion (except fluoride) was required to retain the photocycle of hR. Parallels between the amplitude of the phototransient of hR and the magnitude of the photo-induced tetraphenylphosphonium (TPP+) uptake suggests that hR is a light-driven halogen pump, which supports the hypothesis by Schobert and Lanyi (J. Biol. Chem., 1982, 257:10306-10313). The order of effectiveness of halogen was Br- greater than Cl- greater than I-. On the other hand, no specific ion was required to retain the photocycle of tR, and tR was concluded to be nonelectrogenic.

Anions↗
PubMed1984

Differential effects of dietary eicosapentaenoic and docosahexaenoic fatty acids on lowering of triglyceride and cholesterol levels in the serum of rats on hypercholesterolemic diet.

This investigation was attempted in order to further clarify the effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on lipid metabolism in rats. Ninety-three percent ethyleicosapentaenoate (EPAconc) and 91% ethyl-docosahexaenoate (DHAconc) were used and supplied at the 3% level to a hypercholesterolemic basal diet which contained 5% lard. Four experimental diets were prepared from (1) 5% olive oil, (2) 2% olive oil +3% ethyl-linoleate, (3) 2% olive oil +3% EPAconc, and (4) 2% olive oil +3% DHAconc plus hypercholesterolemic basal diet. Young male rats were fed on these diets for respective periods of 10 and 20 days. Concentrations of serum lipids in rats fed on the diets (2), (3) and (4) were compared to those of the control group (diet (1]. Serum total cholesterol level was significantly lower only in the animals fed on DHAconc, whereas serum triglyceride concentration was significantly lower only in the animals fed on EPAconc. Serum phospholipid level was significantly lowered both in the animals fed on either EPAconc or DHAconc. Serum lipid peroxide concentration was elevated in these two groups of animals, while serum alpha-tocopherol concentration was lower in both groups of animals fed on EPAconc and DHAconc, respectively, although these findings were less marked in the rats on the EPAconc diet. From these findings, it is postulated that EPA and DHA have different effects on lipid metabolism in rats with hypercholesterolemia experimentally induced.

Animals↗
PubMed1983

Light-induced delta pH of envelope vesicles containing halorhodopsin measured by use of a spin probe.

The spin-labeled amine, 4-amino-2,2,6,6-tetramethyl-piperidino-N-oxyl was used to measure the photoinduced delta pH in the envelope vesicles derived from mutant cells of Halobacterium halobium. The cells contain halorhodopsin (hR) and are spectroscopically free from bacteriorhodopsin (bR). The EPR signals from the extravesicular populations of the probe was quenched by ferricyanide. The membrane bound population of the probe was less than 1% of the amount of the probe entrapped within the vesicle. Hence, we can monitor continuously the concentration of the intravesicular populations of the probe and delta pH can be calculated from the line height of the signal. The kinetic analysis indicated that the time course of the change in the EPR signal represents faithfully delta pH of the vesicle. At pH 7.5, the photoinduced delta pH showed a maximum. The kinetic constant of pH change also displayed a peak at this pH. Addition of uncoupler did not increase either the rate nor magnitude of delta pH at this pH, but at other pH, especially at lower pH, uncoupler showed its effect. A theoretical equation was derived which correlated the photocycle of hR with delta pH. According to the analysis by use of this equation, the time constant of the photocycle was suggested to be constant in pH ranging from 5.5 to 8.25. The maximum in photoinduced delta pH observed at pH 7.5 was concluded to be due to the permeability dependence of ions, especially of H+ on pH. The temperature dependence of delta pH was measured. As the temperature decreased, delta pH was, surprisingly, found to be increased. The rate constant of the photocycle analyzed by the equation, however, decreased with decrease of temperature.

Bacterial Proteins↗
PubMed1983

Quantitative analysis of changes in cell shape of Amoeba proteus during locomotion and upon responses to salt stimuli.

A new parameter expressing the complexity of cell shape defined as (periphery)2/(area) in 2D projection was found useful for a quantitative analysis of changes in the cell shape of Amoeba proteus and potentially of any amoeboid cells. During locomotion the complexity and the motive force of the protoplasmic streaming in amoeba varied periodically, and the Fourier analysis of the two showed a similar pattern in the power spectrum, giving a rather broad peak at about 2.5 X 10(-3) Hz. The complexity increased mainly due to elongation of the cell as external Ca2+ increased. This effect was blocked by La3+, half the inhibition being attained at 1/200 amount of the coexisting Ca2+. On the other hand, the complexity decreased due to rounding up of the cell as the concentration of other cations, such as Sr2+, Mg2+, Co2+, Ni2+, Na+, K+ etc., increased. Irrespective of the opposite effects of Ca2+ and other cations on the cell shape, the ATP concentration in amoeba decreased in both cases with increase of all these cations. The irregularity in amoeboid motility is discussed in terms of a dynamic system theory.

Adenosine Triphosphate↗
PubMed1983

Photochemistry of two rhodopsinlike pigments in bacteriorhodopsin-free mutant of Halobacterium halobium.

Two photocycles due to two different pigments were found in membrane vesicles of a bacteriorhodopsin-free mutant of Halobacterium halobium. A pigment absorbing approximately 590 nm halorhodopsin (HR) underwent a faster photocycle with a phototransient at approximately 490 nm (half-time of decay, tau 1/2 = 10 ms). Another third rhodopsinlike pigment (TR) absorbing approximately 580 nm underwent a slower photocycle accompanying a phototransient absorbing below 410 nm (tau 1/2 = 0.8s). The photocycles were measured under various conditions of temperature, NaCl concentration, pH, and in the presence of cholate. All results obtained support the notion that the two photocycles are independent of each other, and the fast or the slow cycle can be abolished after these treatments. At alkaline pH, the wavelength of maximum absorbance of both pigments shifted to blue, but the magnitude of the shift of the pigment undergoing the slow photocycle was much greater than the other. The ratio of the content of the two pigments varies among bacteriorhodopsin-free mutants.

Bacteriorhodopsins↗
PubMed1983

Dietary effect of omega-3 type polyunsaturated fatty acids on serum and liver lipid levels in rats.

The dietary effect of omega-3 type highly polyunsaturated fatty acid concentrate (PUFA mix) was investigated on cholesterol and triglyceride levels in the serum and liver, and high density lipoprotein cholesterol (HDL-cholesterol) levels in the serum. The PUFA mix prepared from squid liver oil contained about 75% of total omega-3 type fatty acids. In rats fed the normal diet to which 3% PUFA mix was added, the levels of triglyceride, total cholesterol and phospholipid in the serum markedly decreased as compared to rats fed a 3% methyl-oleate diet. However, lipid peroxide values in the liver and serum increased in rats fed PUFA mix-diets. In the hypercholesterolemic rats, a 5% PUFA mix-diet caused growth retardation and a corresponding reduction in food intake. Lipid peroxide in the liver and serum were more elevated in rats fed diets containing 1, 3 and 5% PUFA mix than in rats fed diets containing 5% oleate or 5% linoleate. In all the rats on PUFA mix-diets, there were depression of serum total cholesterol and elevation of serum HDL-cholesterol. The ratio of HDL-cholesterol to total cholesterol increased in proportion to the amounts of dietary PUFA mix. Total cholesterol level in the liver was depressed after PUFA mix feeding.

Animals↗
PubMed1982

Measurement of membrane potential in polymorphonuclear leukocytes and its changes during surface stimulation.

The membrane potential of guinea pig polymorphonuclear leukocytes has been assessed with two indirect probes, tetraphenylphosphonium (TPP+) and 3,3'-dipropylthiadicarbocyanine (disS-C3-(5)). The change in TPP+ concentration in the medium was measured with a TPP+-selective electrode. By monitoring differences in accumulation of TPP+ in media containing low and high potassium concentrations, a resting potential of -58.3 mV was calculated. This potential is composed of a diffusion potential due to the gradient of potassium, established by the Na+, K+ pump, and an electrogenic potential. The chemotactic peptide fMet-Leu-Phe elicits a rapid efflux of accumulated TPP+ (indicative of depolarization) followed by its reaccumulation (indicative of repolarization). In contrast, stimulation with concanavalin A results in a rapid and sustained depolarization without a subsequent repolarization. The results obtained with TPP+ and diS-C3-(5) were comparable. Such changes in membrane potential were observed in the absence of extracellular sodium, indicating that an inward movement of sodium is not responsible for the depolarization. Increasing potassium levels, which lead to membrane depolarization, had no effect on the oxidative metabolism in nonstimulated or in fMet-Leu-Phe-stimulated cells. Therefore, it seems unlikely that membrane depolarization per se is the immediate stimulus for the respiratory burst.

Animals↗
PubMed1982

Effect of Ca2+, cyclic GMP, and cyclic AMP added to artificial solution perfusing lingual artery on frog gustatory nerve responses.

The lingual artery of the bullfrog was perfused with artificial solution and the effects of Ca2+, Ca-channel blockers (MnCl2 and verapamil), cGMP, and cAMP added to the perfusing solution of the gustatory nerve responses were examined. The responses to chemical stimuli of group 1 (CaCl2, NaCl, distilled water, D-galactose, and L-threonine) applied to the tongue surface were greatly decreased by a decrease in Ca2+ concentration in the perfusing solution, suppressed by the Ca-channel blockers, enhanced by cGMP, and suppressed by cAMP. The responses to chemical stimuli of group 2 (quinine hydrochloride, theophylline, ethanol, and HCl) were practically not affected by a decrease in Ca2+ concentration, the Ca-channel blockers, cGMP, and cAMP. The responses to the stimuli of group 1 seem to be induced by Ca influx into a taste cell that is triggered by depolarization and modulated by the cyclic nucleotides in a taste cell. The responses to group 2 seem to be induced without accompanying Ca influx.

Animals↗
PubMed1982

Changes in intracellular pH accompanying chemoreception in the plasmodia of Physarum polycephalum.

A new method for measuring intracellular pH, employing the intrinsic fluorescent pigments of the plasmodia of the myxomycete Physarum polycephalum, was used to study the role of pH in chemotactic transduction in the plasmodia. The cell became acidified following stimulation with the attractants alanine, glucose, galactose and maltose when their concentrations exceeded the respective thresholds of chemoreception and taxis. The degree of cell acidification paralleled the relaxing tendency in tension generation. A non-metabolizable attractant, 2-deoxyglucose, also acidified the cell. However, the repellent salts NaCl, KCl and CaCl2 did not change the intracellular pH. Our results suggest that the effects of attractants are mediated by intracellular pH, while the effects of repellents are transduced by ATP as reported previously.

Adenosine Triphosphate↗
PubMed1982

High sensitivity of Xenopus gustatory receptors to amino acids and bitter substances.

The gustatory nerve responses of the aquatic toad Xenopus laevis to salts, acids, amino acids, and bitter substances were recorded. 1) The gustatory receptors were sensitive to amino acids and bitter substances. The thresholds were 10(-7) M for Arg, 3 X 10(-9) M for strychnine, and 3 X 10(-8) M for quinine, 200-20,000 times lower than the thresholds for the respective stimuli in the bullfrog. 2) The basic and the neutral amino acids were effective whereas the acidic ones were not. Relations between the responses and log stimulus concentrations for the basic amino acids were linear in a wide concentration range whereas those for the neutral ones were of S shape. Cross-adaptation did not occur among pairs of a basic amino acid and a neutral one. 3) Responses to the basic amino acids and the basic bitter substances were suppressed by the addition of salts to the stimulating solutions, while those to the neutral and the acidic substances were not suppressed.

Amino Acids↗
PubMed1981

Selective enhancement and suppression of frog gustatory responses to amino acids.

Properties of the receptor sites for L-amino acids in taste cells of the bullfrog (Rana catesbeiana) were examined by measuring the neural activities of the glossopharyngeal nerve under various conditions. (a) The frogs responded to 12 amino acids, but the responses to the amino acids varied with individual frogs under natural conditions. The frog tongues, however, exhibited similar responses after an alkaline treatment that removes Ca2+ from the tissue. The variation in the responses under natural conditions was apparently due to the variation in the amount of Ca2+ bound to the receptor membrane. (b) The responses to hydrophilic L-amino acids (glycine, L-alanine, L-serine, L-threonine, L-cysteine, and L-proline) were of a tonic type, but those to hydrophobic L-amino acids (L-valine, L-leucine, L-isoleucine, L-methionine, L-phenylalanine, and L-tyrptophan) were usually composed of both phasic and tonic components. (c) The properties of the tonic component were quite different from those of the phasic component: the tonic component was largely enhanced by the alkaline treatment and suppressed by the acidic treatment that increases binding of Ca2+ to the tissue. Also, the tonic component was suppressed by the presence of low concentrations of salts, or the action of pronase E, whereas the phasic component was unchanged under these conditions. These properties of the phasic component were quite similar to those of the response to hydrophobic substances such as quinine. These results suggest that the hydrophilic L-amino acids stimulate receptor protein(s) and that the hydrophobic L-amino acids stimulate both the receptor protein and a receptor site similar to that for quinine. (d) On the basis of the suppression of the responses to amino acids by salts, the mechanism of generation of the receptor potential is discussed.

Amino Acids↗
PubMed1981

Taste transduction mechanism: similar effects of various modifications of gustatory receptors on neural responses to chemical and electrical stimulation in the frog.

Responses in the frog glossopharyngeal nerve induced by electrical stimulation of the tongue were compared with those induced by chemical stimuli under various conditions. (a) Anodal stimulation induced much larger responses than cathodal stimulation, and anodal stimulation of the tongue adapted to 5 mM MgCl2 produced much larger responses than stimulation with the tongue adapted to 10 mM NaCl at equal current intensities, as chemical stimulation with MgCl2 produced much larger responses than stimulation with NaCl at equal concentration. (b) The enhansive and suppressive effects of 8-anilino-1-naphthalenesulfonate, NiCl2, and uranyl acetate on the responses to anodal current were similar to those on the responses to chemical stimulation. (c) Anodal stimulation of the tongue adapted to 50 mM CaCl2 resulted in a large response, whereas application of 1 M CaCl2 to the tongue adapted to 50 mM CaCl2 produced only a small response. This, together with theoretical considerations, suggested that the accumulation of salts on the tongue surface is not the cause of the generation of the response to anodal current. (d) Cathodal current suppressed the responses induced by 1 mM CaCl2, 0.3 M ethanol, and distilled water. (e) The addition of EGTA or Ca-channel blockers (CdCl2 and verapamil) to the perfusing solution of the lingual artery reversibly suppressed both the responses to chemical stimulus (NaCl) and to anodal current with 10 mM NaCl. (f) We assume from the results obtained that electrical current from the microvillus membrane of a taste cell to the synaptic area supplied by anodal stimulation or induced by chemical stimulation activates the voltage-dependent Ca channel at the synaptic area.

Anilino Naphthalenesulfonates↗
PubMed1981

The effect of longitudinal tension on the amplitude of the contraction rhythm of plasmodial strands of Physarum polycephalum.

Plasmodial strands of Physarum polycephalum exhibit a characteristic contraction rhythm. The amplitude of the isotonic tension increased linearly with the cube root of relative stress. The period of the isometric tension increased linearly with the amplitude of the oscillation, but stayed constant above a critical value. The above empirical formulae were found applicable for all temperatures employed, 9 to 28 degrees C, but different temperature coefficients were observed below and above 15 to 16 degrees C.

Cytoplasm↗
PubMed1980

Conversion of positive to negative chemotaxis by Ca2+ ionophore treatment in plasmodium of Physarum polycephalum.

The plasmodium of Physarum polycephalum was treated with Ca2+ ionophores A23187 or X-537A, and the effects on the chemotactic and contractile activities were studied by applying a double-chamber method and an optical method. (1) At low Ca2+ concentration, attractants (glucose, L-alanine) KH2PO4) remained as attractants and induced a relaxation in the plasmodial strand. Increase in the external Ca2+ level caused a contraction of plasmodium with the same stimuli, and hence converted the attractants to repellents. (2) This phenomenon was specific to Ca2+; Mg2+, Sr2+ or Ba2+ showed no appreciable effects. (3) Repellents (sucrose, KCl, Quinine) induced a contraction, which was not altered by the Ca2+ ionophore treatment. (4) Efflux of Ca2+, which was measured by chemiluminescence of aequorin, increased on glucose reception in the presence of ionophore.

Anti-Bacterial Agents↗
PubMed1980

Changes in membrane potential and membrane fluidity in Tetrahymena pyriformis in association with chemoreception of hydrophobic stimuli: fluorescence studies.

The fluorescence intensity of rhodamine 6G (Rh6G) and 1,6-diphenyl-1,3,5-hexatriene (DPH) in the presence of Tetrahymena pyriformis was measured to monitor changes in the membrane potential and in the gross structure of the surface membrane in response to chemical stimuli. So-called "odorants" for higher vertebrates, which are usually uncharged and hydrophobic compounds, were chosen as chemical stimuli for a model study of the olfactory response. The fluorescence intensity of Rh6G started to increase at the chemotactic thresholds of the stimuli, indicating that negative chemotaxis of T. pyriformis to the hydrophobic stimuli is induced by depolarization of the cell. The fluorescence intensity of DPH increased in close association with chemoreception of the hydrophobic stimuli. The increase in the fluorescence intensity was ascribed mainly to uptake of DPH, suggesting that gross structural changes of the surface membrane occur with the reception of hydrophobic stimuli. The membrane fluidity determined by fluorescence polarization of DPH increased in close association with the chemoreception of the hydrophobic stimuli. Inorganic salts such as NcCl, KCl, and CaCl2 did not change the DPH fluorescence intensity or the fluorescence polarization, although these stimuli induced depolarization and negative chemotaxis in T. pyriformis.

Animals↗