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Biomedical subjects

I Ueda

Publications and source records attributed to I Ueda.

At least 19 recordsLinked to original sources
PubMed1979

Antagonism between high pressure and anesthetics in the thermal phase-transition of dipalmitoyl phosphatidylcholine bilayer.

The antagonizing action of hydrostatic pressure against anesthesia is well known. The present study was undertaken to quantitate the effects of hydrostatic pressure and anesthetics upon the phase-transition temperature of dipalmitoyl phosphatidylcholine vesicles. The drugs used to anesthetize the phospholipid vesicles included an inhalation anesthetic, halothane, a dissociable local anesthetic, lidocaine and an undissociable local anesthetic, benzyl alcohol. All anesthetics decreased the phase-transition temperature dose-dependently. In the case of lidocaine, the depression was pH dependent and only uncharged molecules were effective. The application of hydrostatic pressure increased the phase-transition temperature both in the presence and the absence of anesthetics. The temperature-pressure relationship was linear over the entire pressure range studied up to 340 bars. Through the use of Clapeyron-Clausius equation, the volume change accompanying the phase-transition of the membrane was calculated to be 27.0 cm3/mol. Although the anesthetics decreased the phase-transition temperature, the molar volume change accompanying the phase-transition was not altered. The anesthetics displaced the temperature-pressure lines parallel to each other. The mole fraction of the anesthetics in the liquid crystalline membrane, calculated from the van't Hoff equation, was independent of pressure. This implies that pressure does not displace the anesthetics from the liquid membrane, and the partition of these agents remains constant. The volume change of the anesthetized phospholipid membranes is entirely dependent upon the phase-transition and not on the space occupied by the anesthetics.

Anesthetics↗
PubMed1979

Hydrophilic region of lecithin membranes studied by bromothymol blue and effects of an inhalation anesthetic, enflurane.

A pH-indicator dye, bromothymol blue, was used to probe the hydrophilic surface of dimyristoyl-, dipalmitoyl-, and distearoylphosphatidylcholine bilayer vesicles. The apparent pK of the surface-adsorbed dye was larger than the bulk pK value. The contribution of the choline positive charge on the dissociation constant of the dye adsorbed on the vesicle surface was estimated by screening the charge interaction with 2 M KCl. The effective surface potentials interacting with the dye were thus estimated to be 33.2, 45.6, and 46.8 mV, respectively, for the dimyristoyl-, dipalmitoyl-, and distearoylphosphatidylcholine vesicles. From the differences between the obtained effective potentials and the calculated surface potentials of the charge-determining plane of the choline head, the distances between the prototropic part of the dye and the choline charge-determining plane were estimated to be 10.5, 8.0, and 7.8 A, respectively. These values were obtained at 25 degrees C; the dimyristoylphosphatidylcholine membrane was in the liquid-crystalline phase and the other two were in the solid gel phase. Addition of an inhalation anesthetic, enflurane, decreased the distance in the dimyristoylphosphatidylcholine vesicles and increased the distance in the dipalmitoyl- and distearoylphosphatidylcholine vesicles. The increase of precessional motion of choline head by the inhalation anesthetic is apparently responsible for the changes.

Bromthymol Blue↗
PubMed1979

Relationship between surface activity and toxicity to Chang liver cultures of tricyclic antidepressants.

Chang liver cell cultures were exposed to the tricyclic antidepressants, chlorimipramine (CIM), nortriptyline (NT), amitriptyline (AT), imipramine (IM), and dosepin (DOX). Loss of enzymes into surrounding media and cytopathic changes were used to quantitate cytotoxicity. Time- and concentration-related cytotoxic effects were evident for all drugs. The order of cytotoxic potency was CIM greater than NT greater than AT greater than IM greater than DOX. All tricyclic antidepressants tested lowered the surface tension of the salt solution contained in the tissue culture media and the order of their surface activity was identical to that of their cytotoxicity. It is postulated that the cellular toxicity induced by tricyclic antidepressants in vitro is related to a function of their surface activity.

Amitriptyline↗
PubMed1978

Tyrosine aminotransferase from chick liver. Heat activation and cold inactivation of the enzyme.

The reversible heat activation and cold inactivation of tyrosine aminotransferase (L-tyrosine:2-oxoglutarate aminotransferase, EC 2.6.1.5) of chick liver were investigated. When the enzyme obtained by gel filtration was preincubated at 37 degrees C for 10 min with 50 micrometer pyridoxal 5'-phosphate (pyridoxal-5'-P), a 7-fold increase in enzyme activity was detected. When the preincubated enzyme was cooled to 0 degrees C, it lost its activity. Furthermore, the dramatic cyclical changes in enzyme activity occurred by sequential heating at 37 degrees C and cooling to 0 degrees C of the enzyme, in the presence of pyridoxal-5'-P, over shorter periods of time without loss of enzyme activity. However, when alpha-ketoglutarate was added to the enzyme during cold exposure, no further decrease in activity was observed. This protective effect was seen at a concentration of 5 muM.

Animals↗
PubMed1978

Rat liver cysteine dioxygenase (cysteine oxidase). Further purification, characterization, and analysis of the activation and inactivation.

Rat liver cysteine dioxygenase has been purified to homogeneity. It is a single subunit protein having a molecular weight of 22,500 +/- 1,000, with a pI of 5.5. The enzyme purified was catalytically inactive and activated by anaerobic incubation with either L-cysteine or its analogues such as carboxymethyl-L-cysteine, carboxyethyl-L-cysteine, S-methyl-L-cysteine, D-cysteine, cysteamine, N-acetyl-L-cysteine, and DL-homocysteine. The enzyme thus activated with L-cysteine was rapidly inactivated under aerobic condition. This rapid inactivation was observed at 0 degrees C where no formation of either the reaction product cysteine sulfinate or the autoxidation product of cysteine, cystine, was detected. Further analysis shows that the inactivation of the activated enzyme was due to oxygen but unrelated to either the presence of substrate, enzyme turnover or accumulation of inhibitor produced during assay. A distinct rat liver cytoplasmic protein, called protein-A, could completely prevented the enzyme from the aerobic inactivation. The loss of activity during assay in the absence of protein-A was shown to be a first order decay process. From the plots of log(deltaproduct/min) versus time, the initial velocity (VO) and the velocity at 7 min (V7) were obtained. The apparent Km value for L-cysteine in the absence of protein-A was calculated from the initial velocity as 4.5 X 10(-4)M. Protein-A did not alter the apparent Km value for L-cysteine. The chelating agents such as o-phenanthroline, alpha,alpha'-dipyridyl, bathophenanthroline, 8-hydroxyquinoline, EGTA, and EDTA strongly inhibited the enzyme activity when these chelating agents were added before preactivation. The purified cystein dioxygenase contains 1 atom of iron per mol of enzyme protein. By the activation procedure, the enzyme became less susceptible to the heat denaturation, the inhibitory effects of chelating agents and the tryptic digestion.

Animals↗
PubMed1978

Ca2+/protein modulator-dependent and -independent cyclic GMP phosphodiesterase from hog heart.

Ca2+/protein modulator-dependent and -independent guanosine 3':5'-monophosphate (cGMP) phosphodiesterases were separated from hog heart. The protein modulator-free Ca2+/protein modulator-dependent enzyme was partially purified by repeated DEAE-cellulose column chromatography and heat treatment. The final preparation of this enzyme showed no significant basal activity under the standard assay conditions. Lineweaver-Burk plots of the Ca2+/protein modulator-dependent enzyme activity indicated the presence of only a single kinetic form of the enzyme with Km=2.0 X 10(-6) M for for cGMP, whereas the plots for the independent enzyme were anomalous, showing both high and low K m values for cGMP. The Ca2+/protein modulator-dependent enzyme proved relatively stable at 48 degrees C for 1 h, but the independent form lost its activity under the same conditions. Furthermore, 50% inhibition of the dependent enzyme activity, but only 10% inhibition of the independent enzyme activity, was observed with 0.1 mM adenosine 3':5'-monophosphate (cAMP) when 1 muM cGMP was employed as a substrate.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1978

Decrease of rat liver cysteine dioxygenase (cysteine oxidase) activity mediated by glucagon.

The hepatic cysteine dioxygenase activity of rats was markedly decreased by the intraperitoneal administration of glucagon. The enzyme activity was also decreased by either dibutyryl cyclic AMP or theophylline. The prior administration of actinomycin D completely blocked the glucagon-mediated decrease of enzyme activity, while administrations of this inhibitor of protein synthesis after glucagon injection did not block the decrease of enzyme activity. A single administration of actinomycin D resulted in a slight increase of cysteine dioxygenase activity in the rat liver. On the other hand, the injection of cycloheximide resulted in a rapid decrease of the hepatic cysteine dioxygenase with a half-life of 2.5 h. The half-life of the enzyme in rat liver after glucagon administration was one hour. The administration of hydrocortisone or insulin had no effect on the glucagon-mediated decrease of cysteine dioxygenase of rat liver. The enzyme activity of alloxan diabetic rat liver was almost the same as that of the intact rat liver. The evidence obtained here suggests that enhancement of degradation or inactivation of cysteine dioxygenase is responsible for the glucagon-mediated decrease of the enzyme activity in rat liver.

Adrenal Glands↗
PubMed1978

Possible participation of glucocorticoid in elevation of 3',5'-cyclic AMP levels through inhibition of cyclic AMP phosphodiesterase.

Administration of prednisolone and cholate to rats elevated levels of cAMP (adenosine 3',5'-cyclic monophosphate) by 1.5- to 2.0-fold. Compounds such as prednisolone, hydrocortisone, cholate, and deoxycholate were found to be potent inhibitors of partially purified cAMP phosphodiesterase prepared from rat liver. Kinetic analysis showed that the prednisolone inhibition was noncompetitive with a Ki of 8.9 x 10(-4) M. These results suggest that in addition to increasing DNA-dependent RNA polymerase activity in vivo, a large application of glucocorticoid may incur elevation of intracellular cAMP levels.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1977

Reversible and irreversible inhibition by anesthetics of the calcium-induced luminescence of aequorin.

The actions of various kinds of so-called membrane-stabilizing drugs on Ca2+-induced flash intensity of purified aequorin, a photoprotein obtained from Aequorea aequorea, were examined. All drugs used in this experiment, including inhalational anesthetics, tetracaine, chlorpromazine, and morphine, depressed flash intensity, and the inhibition increased with time. The inhibition followed a mixture of reversible and irreversible kinetics. A method of analyzing irreversible kinetics is presented. The dissociation constants for reversible inhibition and the rate constants for irreversible inhibition are presented for each agent.

Aequorin↗
PubMed1977

Depression of phase-transition temperature in a model cell membrane by local anesthetics.

Disordering, fluidizing and dilating effects of anesthetics upon cell membranes are well recognized. The fluidization can be precisely measured with phospholipid membranes. When phospholipids are dispersed in water, they form globules of bilayer structure. These model membranes undergo transition between crystalline (ordered and less fluid) and liquid crystalline (less ordered and fluid) phases according to the temperature, the degree of packing of each molecule, and the chemical environment. The phase transition occurs in a cooperative fashion and the turbidity of the dispersion changes abruptly, clear in liquid crystalline phase and turbid in crystalline phase. The present study was undertaken to quantitate the fluidizing effects of local anesthetics on dipalmitoyl lecithin (DPL) bilayer dispersion by measuring the turbidity change. Tetracaine, bupivacaine, lidocaine, and procaine were studied. They all depressed the phase-transition temperature. The binding of the drugs to the model membrane followed unsaturable kinetics, and the pH titration curve showed that only uncharged molecules were active. The freezing point depression was analyzed according to the Van't Hoff model. From this model, the partition coefficients of the uncharged molecules between DPL and water were estimated: lidocaine 76, procaine 159, bupivacaine 812, and tetracaine 1,405. The concentration of local anesthetics in the DPL phase needed to decrease the phase-transition temperature 1 degree C showed a constant value of 0.132 M. The concentration of local anesthetics in the DPL phase is a function of pH, partition coefficient, and volume ratio between the DPL and aqueous phases. The normalized values of the fluidizing action of these drugs at physiologic conditions correlated well with their nerve-blocking potencies. The present results indicate that the uncharged molecules fluidize the lecithin membrane by unsaturable nonspecific binding. The possible effect of the charged molecules upon the fluidity of natural membranes remains to be established.

Anesthetics, Local↗
PubMed1977

[Simplification of gamma-ray spectral data by using Fourier transform].

A method is proposed to represent gamma-ray response spectra by Fourier series for the purpose of compressing spectral data. The usefulness of the method was confirmed by applying it to a spectral library of a NaI detector. In the method, a response spectrum as a wave is described by superposition of sine (cosine) waves with low frequencies, whose coefficient parameters can be obtained by a Fast Fourier Transform program. The relation between the number of parameters and the fitting error is discussed, and as the result, it is shown that the number of parameters can be reduced to about a half. The merits and features are presented in practical application of the method to the analysis of gamma-ray spectra.

Fourier Analysis↗
PubMed1977

[Analysis of gamma-ray spectra by using fast Fourier transform (author's transl)].

In order to simplify the mass data processing in a response matrix method for gamma-ray spectral analysis, a method using a Fast Fourier Transform devised. The validity of the method was confirmed by a computer simulation for spectra of a NaI detector. The method uses the fact that spectral data can be represented by Fourier series with reduced number of terms. The estimation of intensities of gamma-ray components is performed by a matrix operation using the compressed data of an observation spectrum and standard spectra in Fourier coefficients. The identification of gamma-ray energies is also easy. Several features in the method and a general problem to be solved in a response matrix method are described.

Fourier Analysis↗