[Taste sensor].
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Artificial Intelligence↗
Biomedical subjects
K Toko
Publications and source records attributed to K Toko.
Multichannel taste sensor using electric potential changes in lipid membranes.
A taste sensor with a multichannel electrode was developed by using lipid membranes as a transducer of taste substances. The sensor can detect the taste in a similar manner to the human gustatory sensation by response patterns of electric potential to taste substances. The sensitivity, reproducibility and durability were superior to those of humans. The same taste as that elicited by some commercial aqueous drink was reproduced by making aqueous solution mixed from four kinds of basic taste substances, the concentrations of which were determined so that the electric-potential pattern of this mixed solution could agree well with the pattern by the drink. Different brands of beer were easily distinguished by the electric-potential patterns.
Biosensing Techniques↗
Responses of lipid membranes of taste sensor to astringent and pungent substances.
Astringent substances and pungent substances were studied using a multichannel taste sensor with lipid membranes. The electric-potential pattern constructed of eight outputs from the membranes has information of taste quality and intensity. Pungent substances, such as capsaicin, piperine and allyl isothiocyanate, had no effect on the membrane potentials of the lipid membranes. On the other hand, astringent substances such as tannic acid, catechin, gallic acid and chlorogenic acid changed the potentials remarkably. A principal component analysis of the patterns in electric potential changes caused by the taste substances revealed the astringency is located between bitterness and sourness.
Astringents↗
Dependence of the thymidylate synthase inhibition rate on the interval after the last administration of tegafur in sigmoid colon cancer patients.
The thymidylate synthase (TS) inhibition rate was measured after tegafur (FT) administration (1.5 g/day, at least 10 days) in 7 sigmoid colon cancer patients. The TS inhibition rate decreased as the interval between the time of the last administration and the time of the tumor resection increased longer. This study provides basic data for considering methods of drug administration and assessment of modification, for example, by leucovorin.
Adenocarcinoma↗
Electrical characteristics in an excitable element of lipid membrane.
Electrical characteristics in a membrane constructed from a porous filter adsorbed with a lipid analogue, dioleoyl phosphate (DOPH), were investigated in a situation interposed between 100 mM NaCl + 3 mM CaCl2 and 100 mM KCl. Calcium ions affected significantly the membrane characteristics. The membrane potential was negative on the KCl side, which implies the higher permeability to K+ than Na+; this tendency was increased by a tiny amount of Ca2+. While the membrane showed a low electrical resistance of several k omega . cm2 under K+/Na+ gradient, it showed several M omega . cm2 by Ca2+. The surface structure of the membrane exhibited many voids in the low-resistance state, but the surface was covered by oil droplets in the high-resistance state. Oscillations of the membrane potential appeared spontaneously with application of the electrical current from the KCl side to the NaCl + CaCl2 side. The frequency was increased with the electrical current. All these results were explained comprehensively using an electrochemical kinetic model taking account of the Ca2+ binding effect, where DOPH assemblies make a phase transition between oil droplets due to Ca2+ and multi-bilayers with excess K+. The oscillation arises from coupling of the phase transition to accumulation and release of K+ or Ca2+. This membrane can be used as an excitable element regulated by Ca2+ in neuro-computer devices.
Calcium↗
Periodic band pattern as a dissipative structure in ion transport systems with cylindrical shape.
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Biological Transport↗
Electric inhomogeneity in membranes of Characean internode influenced by light/dark transition, O2, N2, CO2-free air and extracellular pH.
The electric membrane potential as functions of position and time of Characean internode has been studied using a modified water-film electrode technique. Between the low-conductance hyperpolarized region (called the H-region or acidic region) and the high-conductance depolarized region (D-region), there is a difference in the direction of responses to light-off and -on stimulations. In darkness the membrane potential becomes hyperpolarized in the D-region, whereas it is depolarized in the H-region at the steady state. The potential difference between D- and H-regions, delta Vm, is increased by exposure to pure O2, N2, or CO2-free air. When the amount of water surrounding the internode is limited, the formation of an electric pattern occurs rapidly. In contrast, the recovery is delayed. The membrane potential of the D-region is sometimes hyperpolarized significantly with lowering of the extracellular pH to 7.5, while the potential of the H-region is slightly depolarized. This seems to be an all-or-none type response. However, the electric profile is always homogenized with the pH of 6.8. Thus, the pH around 7.5 may be a threshold level to open/close putative OH- (or H+) channels of the D-region.
Carbon Dioxide↗
Electric oscillation in an excitable model membrane impregnated with lipid analogues.
A model membrane constructed from a Millipore filter, whose pores were impregnated with dioleyl phosphate, exhibited an electric self-oscillation under nonequilibrium conditions. The membrane interposed between two solutions with the same KCl concentrations showed no temporal change in membrane potential. However, the potential became oscillatory on application of an electric current to the membrane. The frequency was proportional to the magnitude of the electric current. When both KCl solutions were replaced by NaCl solutions, a similar trend was observed, although the oscillation was not as regular as in the case of KCl. A membrane placed between equimolar solutions of KCl and NaCl, on the other hand, gave rise to an oscillation even without current application. When a membrane was placed between 5 mM KCl and 100 mM KCl, it was found that NaCl added to the 5 mM KCl side had a pronounced effect on the membrane with respect to the frequency response of the oscillation. These results indicate that the dioleyl phosphate membrane discriminates Na+ from K+.
Chemical Phenomena↗
Self-sustained oscillations of electric potential in a model membrane.
A model membrane constructed from a Millipore filter, whose pores are filled with dioleyl phosphate molecules, exhibits a self-oscillation of the electric potential with a period of about a few seconds in the presence of a salt-concentration difference, pressure difference and/or electric current across the filter. In this paper, the effects of chemicals such as KCl, CaCl2, pH and sucrose on the self-oscillation are investigated experimentally. These chemical substances are shown to alter the characteristic properties as the frequency of oscillation. Theoretical consideration of electrochemical interaction between these substances and DOPH molecules gives a fairly good explanation of the observed results.
Kinetics↗
Influence of monovalent and divalent cations on the surface area of phosphatidylglycerol monolayers.
A theory is presented on the electrostatic properties of the surface area of phosphatidyl-glycerol monolayers spreading at an air-water interface in the presence of monovalent and divalent cations. In the present theory, the adsorption of monovalent and divalent cations to the membranes is taken into account, besides the dissociation of protons, as possible cause of the change of surface charge density with the variation of pH or ion concentrations. It is also pointed out that, in the presence of structure-making ions such as Li+ and Na+, the nearest-neighbour interactions between proton dissociation sites become important for the monolayers in the gel state to yield a sharp expansion of the surface area with the increase of pH. The present theory shows quantitative agreements with previously-observed data.
Cations, Divalent↗