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Biomedical subjects

N Kamo

Publications and source records attributed to N Kamo.

At least 91 records · Page 5Linked to original sources
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

Light-dependent delta pH and membrane potential changes in halobacterial vesicles coupled to sodium transport.

Bacteriorhodopsin and Halorhodopsin present in Halobacterium halobium strains have been investigated in relation to Na+/H+ exchange in isolated cell envelope vesicles. Upon illumination, these retinal proteins result in extrusion of sodium ions by either an electrogenic Na+/H+ antiporter and/or a direct sodium pump. Since a molecular characterization of these mechanism(s) of sodium extrusion has not yet been realized, it was of interest to measure directly the light- and sodium-dependent changes in delta pH and membrane potential under nearly identical conditions in S9 and R1mR cell membrane vesicles to gain information on the relation of these retinal proteins to sodium extrusion. These activities were evaluated in terms of their dependence on light intensity, and on the inhibitory effect of chemical modifiers of carboxyl groups (carbodiimides); electroneutral exchanges (monensin and triphenyltin); digitoxin and some analogues; and phloretin. Under most of the conditions and treatments employed, light- and sodium-dependent delta pH led to similar effects in both membrane vesicle types. Hence, it is concluded that the delta pH and delta psi which arise from sodium transport occur by either a single mechanism or by one which shares common features.

Bacteriorhodopsins↗
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↗
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

Significance of surface potential in interaction of 8-anilino-1-naphthalenesulfonate with mitochondria: fluorescence intensity and zeta-potential.

The 8-anilino-1-naphthalenesulfonate (Ans) fluorescence in nonenergized and energized mitochondria was measured at various concentrations of Ans and KCl. Under the same experimental conditions, the zeta potential was determined from measurements of the electrophoretic mobility of mitochondria. The fluorescence intensity under various conditions was represented quantitatively in terms of the Langmuir adsorption isotherm where the electrostatic interaction acting between Ans and mitochondria was properly taken into account. The values of qN (q) proportionally constant related to quantum yield of Ans: N, the maximum number of the adsorption site) and deltaG (nonelectrical part of the free-energy change due to the binding of Ans to mitochondria) were constant irrespective of difference in energy state and in ionic strength in media. It was concluded that changes in the Ans fluorescence in mitochondria are mainly attributed to changes in the surface potential of mitochondria.

Anilino Naphthalenesulfonates↗
PubMed1977

Selective electrode for dibenzyl dimethyl ammonium cation as indicator of the membrane potential in biological systems.

The electrode sensitive to dibenzyl dimethyl ammonium (DDA+), which is considered to be an indicator of the membrane potential, was constructed by using tetraphenyl borone (TPB-) embedded in dichloroethane. Rapid and Nernstian responses were exhibited against DDA+ solutions ranging between 10(-2) and 3 - 10(-6) M in concentration. High selectivity for DDA+ was observed in the presence of various inorganis salts, ADP, ATP, oxidizable substrates and sugars. The electrode developed here was used to measure the DDA+ uptake in Streptococcus faecalis and the results agreed with those reported by Harold, F.M. and Papineau, D. ((1972) J. Membrane Biol. 8, 27-44 and 45-62). While they determined the DDA+ concentration in the medium by measuring the absorbance of the filtrate treated with the ion-exchangers, the electrode can measure directly the DDA+ concentration in the bacterial suspension without any any pretreatment. It was also shown that the electrode can measure the DDA+ uptake in mitochondria during energization.

Animals↗