Search PubMed⌕ Search

Biomedical subjects

I Ueda

Publications and source records attributed to I Ueda.

At least 55 records · Page 3Linked to original sources
PubMed1995

[Is there a receptor for volatile anesthetics?].

Because of the presence of inequality of the effect of volatile anesthetics on various neurotransmission systems, a specific receptor is proposed. Nonetheless, the differences are only of the magnitude, and almost all synapses are equally affected. The outstanding features of the action of volatile anesthetics are this wide range of the target, and the steep dose-response curve. The steep dose-response curve indicates that various synapses respond to anesthetics with high cooperativity. When a string of amino acids folds into biologically meaningful structure by enclosing hydrophobic areas inside, some hydrophobic parts are left at the protein-water interface. These hydrophobic patches become the binding site for anesthetics. Because of the wide difference in the structures of anesthetics, it is difficult to assume a specific binding site of lock-and-key type for all anesthetics with all synaptic proteins. Presumably volatile anesthetics bind most hydrophobic patches nonselectively. The affinity to each patch may differ, and the relative specificity to each synapse may ensue. To define these areas as a receptor is a matter of opinion.

Anesthetics, Inhalation↗
PubMed1994

Local anesthetics destabilize lipid membranes by breaking hydration shell: infrared and calorimetry studies.

Differential scanning calorimetry (DSC) showed that local anesthetics decreased the pretransition (L beta'-->P beta') temperature of dipalmitoylphosphatidylcholine (DPPC) vesicle membranes four- to five-fold more than the main transition (P beta'-->L alpha) temperature. Because pretransition is mainly a change in the hydrophilic head property (tilted-rippled), the stronger effect on the pretransition suggests that the primary action site of local anesthetics is the lipid-water interface. The interfacial effect was analyzed by Fourier-transform infrared spectroscopy (FTIR) in water-in-oil (CCl4) reversed micelles. FTIR showed that the local anesthetics released hydrogen-bonded water molecules from the phosphate (P = O bands) and glycerol (sn-2 C = O) moieties. The N-H stretching band of the local anesthetics was deconvoluted into two bands: hydrogen bonded to the phosphate moiety of the lipid and free (unbound to lipid). The formation constants between lipid P = O and anesthetic N-H were estimated in CCl4 from the spectral changes: 110 M-1 for lidocaine and 250 M-1 for dibucaine. This small difference in the formation constants cannot explain the ten-fold stronger effect on the phase-transition temperature of dibucaine over lidocaine. By comparing the local anesthetic adsorption to the air/water interface in the presence and absence of lipid monolayers, we have previously shown (Lin et al. (1980) Biochim. Biophys. Acta 598, 51-65) that lipid-anesthetics interaction involves three forces: lipophilic effect, hydrophobic effect, and anesthetic-anesthetic interaction. The anesthetic potency depends mainly on the hydrophobic effect (the difference in the standard molar free energies of local anesthetics in water and at the interface) and anesthetic-anesthetic interaction energy. The anesthetic-anesthetic interaction means cooperativity of local anesthetics for the interfacial density: local anesthetics condense at the membrane surface when there are enough anesthetic molecules present at the interface to attract more anesthetics. The present data suggest that anesthetic action is directed to the interface between water and macromolecule, whether it is lipid membranes or proteins.

Anesthetics, Local↗
PubMed1994

Malignant hyperthermia and calcium-induced heat production.

The abnormal increase in intracellular Ca++ in malignant hyperthermia (MH) is well documented, but the link between the increased Ca++ concentration and high temperature remains speculative. We investigated the possibility that the Ca(++)-induced change in the state of cell membranes may contribute to the temperature elevation. Calcium ion transforms phospholipid membranes from the fluid to solid state. This is analogous to the freezing of water, and liberates latent heat. Differential titration calorimetry (DTC) measures heat production or absorption during ligand binding to macromolecules. When CaCl2 solution was added to anionic dimyristoylphosphatidic acid (DMPA) and dimyristoylphosphatidylglycerol (DMPG) vesicle membranes in incremental doses, DTC showed that the heat production suddenly increased when the Ca++ concentration exceeded about 120 microM. At this Ca++ concentration range, these lipid membranes underwent phase transition. The latent heat of transition was measured by differential scanning calorimetry (DSC). The values were 7.1 +/- 0.7 (SD, n = 4) kcal.mol-1 of DMPA and 6.8 +/- 0.7 (SD, n = 4) kcal.mol-1 of DMPG. The study shows that Ca++ produces heat when bound to lipid membranes. We are not proposing, however, that this is the sole source of heat. We contend that the lipid phase transition is one of the heat sources and it may trigger a hypermetabolic state by elevating the temperature of cell membranes. Because Ca++ is implicated as the second messenger in signal transduction, multiple systems may be involved. More studies are needed to clarify how Ca++ increases body temperature.

Body Temperature↗
PubMed1994

Ethanol unfolds firefly luciferase while competitive inhibitors antagonize unfolding: DSC and FTIR analyses.

Firefly luciferase has gained popularity as a protein model in elucidating anaesthesia mechanism because the bioluminescence of the purified enzyme system is extremely sensitive to volatile anaesthetics. This study analysed the thermal unfolding of firefly luciferase by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). DSC showed that the transition of firefly luciferase from the folded (N) to unfolded (D) state occurred at 41.7 degrees C with the excess heat flow of 1.6 cal g-1 protein. Ethanol decreased the transition temperature dose dependently. In contrast, luciferin competitors, anilinonaphthalenesulphonate (ANS), toluidinonaphthalenesulphonate (TNS), and myristic acid increased the transition temperature. The competitive inhibitors antagonized unfolding and stabilized the N-state. Ethanol promoted unfolding and stabilized the D-state. Temperature scan by FTIR agreed with the DSC data. The intensities of amide-I' and amide-II' bands started to increase at 20-25 degrees C. This temperature coincides with the temperature where the bioluminescence of firefly luciferase is maximal. The unfolding effect of ethanol was evident even at 5 degrees C. ANS, TNS, and myristic acid completely protected the enzyme from the thermal unfolding. This is the first demonstration that the noncompetitive inhibitors induce the isothermal first-order phase transition in a functional protein, whereas competitive inhibitors protect the enzyme from thermal unfolding. The action mode of competitive inhibitors on firefly luciferase is completely different from that of noncompetitive inhibitors.

Calorimetry, Differential Scanning↗
PubMed1994

Temperature-dependent effects of high pressure on the bioluminescence of firefly luciferase.

This study measured the effect of high pressure on the enzyme kinetics of firefly luciferase. When firefly luciferase is mixed with luciferin and ATP, a transient flash of light is produced, followed by a weak light, lasting hours. The first stage reaction produces an enzyme-luciferin-AMP complex and pyrophosphate. Addition of pyrophosphate to the reaction mixture decelerated the reaction rate, and the initial flash was prolonged to a plateau, showing a quasi-equilibrium state. The effects of temperature and pressure were analyzed at the plateau. The temperature scan showed that the maximum light intensity was observed at about 22.5 degrees C. When pressurized below the temperature optimum, pressure decreased the light intensity, while increasing it above the temperature optimum. According to the theory of absolute reaction rate, the following values were obtained for the bioluminescent reaction: delta V++ = 823.7 - 2.8 T cm3/mol and delta V = -280.47 + 0.94T cm3/mol, where T is the absolute temperature, delta V++ and delta V are, respectively, activation volume and the volume change due to thermal unfolding. The optimal temperature for the maximum light output occurs because the reaction rate increases with the temperature elevation at low temperature range, but the thermal unfolding of the enzyme decelerates the reaction velocity when the temperature exceeds a critical value. The intensity of luminescence is modified by the influence of pressure on both delta V++ and delta V. So long as the volume of the activated complex (V++) exceeds the average volume of the nonactivated complex (VN), pressure will slow down the reaction. At the point where the volumes become equal, there is no change in the rate under pressure. When the volume of the activated complex is less than that of the reactants, pressure will speed up the rate. This study showed that firefly luciferase is not exceptional to other enzymes in responding to high pressure.

Adenosine Triphosphate↗
PubMed1994

Ergostane glycosides from Petunia hybrida.

Six new ergostane glycosides, designated as petunioside A, petunioside B, 24-epipetunioside B, petunioside C, 24-epipetunioside C and petunioside D, were isolated from the methanolic extract of the fresh aerial parts of Petunia hybrida. Their structures were determined by means of spectroscopic analysis and single crystal X-ray analysis.

Carbohydrate Conformation↗
PubMed1994

Structure-selective anesthetic action of steroids: anesthetic potency and effects on lipid and protein.

Alphaxalone was a clinically used steroid anesthetic. Its analog delta 16-alphaxalone is nonanesthetic. The only difference between the two is the presence of a double bond at the hydrophobic end of the delta 16-alphaxalone molecule. This study determined the anesthetic potency of alphaxalone and delta 16-alphaxalone in goldfish and compared it with their effects on dipalmitoylphosphatidylcholine (DPPC) membranes and an alpha-helix polypeptide, poly(L-lysine). The goldfish EC50 values were: alphaxalone 5 mumol/L and delta 16-alphaxalone 80 mumol/L. Because these steroids are insoluble to water, the bulk of the steroid in water is absorbed by the fish. Larger containers hold more steroids than smaller containers at the same steroid concentrations. Then, EC50 values vary according to the size of the container. By assuming that the total amount of steroids in the container is distributed into the fish, the EC50 values expressed by the concentration in the fish body become 1.9 mmol/L for alphaxalone, and 30.5 mmol/L for delta 16-alphaxalone. A monoamino acid peptide, poly(L-lysine), can be formed into random-coil, alpha-helix, or beta-sheet. Addition of 0.07 mmol/L alphaxalone to the alpha-helix poly(L-lysine) partially transformed it to a beta-sheet structure. An equivalent change was observed with 3.0 mmol/L delta 16-alphaxalone. These values translate into 3.5 mmol/L for alphaxalone and 0.15 mol/L for delta 16-alphaxalone, when expressed by the concentration in the peptide. The change from alpha-helix to beta-sheet is accompanied by dehydration of the surface of poly(L-lysine). The steroids decreased the phase-transition temperature of DPPC membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1993

Evidence for a common binding site for omeprazole and N-ethylmaleimide in subunit A of chromaffin granule vacuolar-type H(+)-ATPase.

Vacuolar-type H(+)-ATPase from adrenal chromaffin granules was found to be sensitive to omeprazole, a known gastric H+/K(+)-ATPase inhibitor, the concentration required for 50% inhibition being 80 microM freshly-prepared and 12 microM acid-treated reagent. ATP and ADP protected the enzyme from inhibition by omeprazole. The activity of the inhibited enzyme was restored by the addition of reduced glutathione. Omeprazole protected the enzyme from inhibition by N-ethylmaleimide and its binding to the subunit A. As subunit A has a nucleotide binding site(s) and as a cysteine residue is involved in the inhibition by N-ethylmaleimide, these results suggested that the two sulfhydryl reagents bind to the same cysteine residue near the nucleotide binding domain in the subunit A, resulting in inactivation of vacuolar-type H(+)-ATPase.

Adenosine Diphosphate↗
PubMed1993

Close association between Streptococcus sobrinus in the saliva of young children and smooth-surface caries increment.

Three hundred and thirty-eight children (age range 3-5 years) were examined for the presence of mutans streptococci in their saliva. They were divided into four groups according to the prevalent species that were isolated: (1) Streptococcus mutans and Streptococcus sobrinus group (S. mutans > or = 10(3) CFU/ml and S. sobrinus > or = 10(3) CFU/ml); (2) S. mutans group (S. mutans > or = 10(3) CFU/ml but S. sobrinus < 10(3) CFU/ml); (3) S. sobrinus group (S. sobrinus > or = 10(3) CFU/ml but S. mutans < 10(3) CFU/ml), and (4) children with mutants streptococci absent or barely detectable (mutants streptococci < 10(3) CFU/ml). The previous caries experience was compared among the groups, as was the caries increment during a 6-month period after the bacterial examination. The subjects in the S. sobrinus group had both higher caries and higher decayed teeth and surface increments than the S. mutans group. The mean decayed smooth-surface increment (delta d-surface) for the S. sobrinus group was 2.6 and was significantly higher than 0.8 for the S. mutans group. For the subjects with delta d-surface > or = 4, the mean number of S. sobrinus in the saliva was 4.29 x 10(5) CFU/ml and was significantly higher than 0.32 x 10(5) CFU/ml for the subjects without delta d-surface. There was no significant difference in the mean number of S. mutants in saliva between the subjects with and without delta d-surface. The prevalence of S. sobrinus in saliva was more closely associated with future caries activity, especially with smooth-surface caries increment, than the prevalence of S. mutants.

Analysis of Variance↗
PubMed1993

Antiulcer agents. III. Synthesis and antiulcer activity of N-[3-(3-piperidinomethylphenoxy)propyl]pentacyclo[4.2.0.0(2,5).0(3,8).0 (4,7)]-octane carboxamides and related compounds.

The synthesis and antiulcer activity of highly strained cage compounds such as pentacyclo[4.2.0.0(2,5).0(3,8).0(4,7)]-octane (cubane), pentacyclo[4.3.0.0(2,5).0(3,8).0(4,7)]nonane (homocubane) and pentacyclo[5.3.0.0(2,4).0(3,6).0(5,8)]decane are described. Of the compounds obtained, N-[3-(3-piperidinomethylphenoxy)propyl]-4-piperidinocarbonylpen tacyclo [4.2.0.0(2,5).0(3,8).0(4,7)]octane carboxamide (26a) and N-[3'-(3'-piperidinomethylphenoxy)propyl]-1-bromo-9, 9-ethylenedioxypentacyclo[4.3.0.0(2,5).0(3,8).0(4,7)[nonane]-4- carboxamid e (26q) showed more potent antiulcer activity with very good cytoprotective ability in the HCl.ethanol-treated rat model. Compounds 26a and 26q exhibited H2-receptor antagonist potency (in vitro) comparable to that of ranitidine, but did not inhibit histamine-stimulated acid secretion (in vivo) in the gastric fistula rat model, when orally administered in the dose range at which antiulcer and cytoprotective activities were seen. The structure-activity relationships are discussed.

Animals↗
PubMed1993

An evaluation of an anti-inflammatory-histamine H2 antagonist drug complex on gastric erosions in the rat.

The anti-inflammatory effect, gastrotoxicity and in vivo absorption property of the drug complex esterified flurbiprofen (FP) with histamine H2 antagonist, N-[3-(3-(1-piperidinylmethyl)phenoxy)propyl]-2- (2-hydroxyethylthio)acetamide (PPA), were compared with those of FP and FP methyl ester. The drug complex of FP with PPA (FP-PPA) was partly hydrolyzed in vitro in buffer (pH 1.2-7.4) in the presence or absence of pepsin and trypsin, slowly hydrolyzed in gastric mucosal homogenate and quickly hydrolyzed in 10% rat plasma (T1/2 = 35 sec). The hydrolysis rates of FP-PPA were the same as FP methyl ester in enzymatic and nonenzymatic medium. FP-PPA inhibited carrageenan-induced paw edema to the same extent as did FP alone. The plasma concentrations of FP after oral administration of FP derivatives were similar to FP alone. FP-PPA significantly reduced gastrotoxicity in comparison with an equivalent dose of FP, whereas the coadministration of FP and PPA did not affect the gastrotoxicity of FP. The gastrotoxicity of FP methyl ester was dependent on the drug concentration in gastric mucosa, whereas FP-PPA induced minor gastric erosion even at high mucosal drug complex concentration. These data suggested that FP-PPA, the drug complex of FP with histamine H2 antagonist, causes less gastric damage than ester prodrugs like methyl ester or free drug, FP.

Animals↗
PubMed1992

Alcohols dehydrate lipid membranes: an infrared study on hydrogen bonding.

The effects of alcohols (methanol, ethanol, and n-butanol) on the hydrogen bonding of dipalmitoylphosphatidylcholine (DPPC) were studied by Fourier-transform infrared spectroscopy (FTIR) in water-in-oil (carbon tetrachloride) reversed micelles. The bound O-H stretching mode of water, bonded to DPPC, appeared as a broad band at around 3400 cm-1. The O-H bending mode of this complex appeared as a weak broad band at 1644 cm-1. No free O-H signal was observed. When alcohols were added, a part of DPPC-bound water was replaced by the alcohols. The released 'free' water appeared at 3680 cm-1. This free O-H stretching band represents water-alcohol complex. A new broad band of O-H stretching appeared at 3235 cm-1, which represents the alcohol molecules bound to the phosphate moiety of DPPC. When the alcohol concentration was increased, the intensities of the free O-H stretching and bending bands increased. The P = O- antisymmetric stretching band at 1238 cm-1 became broader and shifted to lower frequencies. This means that alcohols interacted with the phosphate moiety and replaced the bound water. In the deconvoluted spectra of the C = O stretching mode, the ratio between the free sn-2 and the hydrogen-bonded sn-2 bands increased; a part of the bound water at the sn-2 carbon in the glycerol skeleton is also released and the free sn-2 signal increased. From the change in the intensity of the P = O- stretching band, the partition coefficients of alcohols between the phosphate region of DPPC and water were estimated: methanol 7.8, ethanol 16.7 at 22.0 degrees C in mole fraction bases. In molality, these values translates into methanol 0.21 and ethanol 0.45. These results indicate that short-chain alcohols interact with lipid membranes at the phosphate moiety at the hydrophilic head, weaken the membrane-water interaction, and destabilize membranes.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1992

Biphasic effects of alcohols on the phase transition of poly(L-lysine) between alpha-helix and beta-sheet conformations.

Poly(L-lysine) exists as a random-coil at neutral pH, an alpha-helix at alkaline pH, and a beta-sheet when the alpha-helix poly(L-lysine) is heated. The present Fourier-transform infrared (FTIR) study showed that short-chain alcohols (methanol, ethanol, and 2-propanol) partially transformed alpha-helix poly(L-lysine) to beta-sheet when their concentrations were low. At higher concentrations, however, these alcohols reversed the reaction, and the alcohol-induced beta-sheet was transformed back to alpha-helix structure. The reversal occurred at 1.40 M methanol, 0.96 M ethanol, and 0.55 M 2-propanol. The alcohol effects on the secondary structure were further investigated by circular dichroism (CD) on the thermally induced beta-sheet poly(L-lysine). Methanol, ethanol, and 1-propanol, but not 1-butanol, shifted the negative mean-residue ellipticity at 217 nm of the beta-sheet poly(L-lysine) to the positive side at low concentrations of the alcohols and to the negative side at high concentrations. With 1-butanol, only the positive-side shift was observed. The positive-side shift at low concentrations of alcohols indicates enhancement of the hydrophobic interactions among the side chains of the polypeptide in the beta-sheet conformation. The negative-side shift indicates a partial transformation to alpha-helix. The shift from the positive to negative side occurred at 7.1 M methanol, 4.6 M ethanol, and 3.1 M 1-propanol. The alcohol concentrations for the beta-to-alpha transition were higher in the CD study than in the IR study.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Propanol↗
PubMed1992

Lateral conductance parallel to membrane surfaces: effects of anesthetics and electrolytes at pre-transition.

The effects of dilute salts and anesthetics were studied on the impedance dispersion in the dipalmitoylphosphatidylcholine (DPPC) liposomes. Below the pre-transition temperature, the apparent activation energy for conductance in DPPC-H2O without salts was equivalent to pure water, 18.2 kJ mol-1. This suggests that the mobile ions (H3O+ and OH-) interact negligibly with the lipid surface below the pre-transition temperature. At pre-transition temperature, the apparent activation energy of the conductance decreased by the increase in the DPPC concentrations. The effects of various salts (LiCl, NaCl, KCl, KBr, and KI) on the apparent activation energy of the conductance were studied. Changes in anions, but not in cations, affected the activation energy. The order of the effect was Cl- less than Br- less than I-. Cations appear to be highly immobilized by hydrogen bonding to the phosphate moiety of DPPC. The smaller the ionic radius, the more ions are fixed on the surface at the expense of the free-moving species. The apparent activation energy of the transfer of ions at the vesicle surface was estimated from the temperature-dependence of the dielectric constant, and was 61.0 kJ mol-1 in the absence of electrolytes. In the presence of electrolytes, the order of the activation energy was F- greater than Cl- greater than Br- greater than I-. When the ionic radius is smaller, these anions interact with the hydration layer at the vesicle surface and the ionic transfer may become sluggish. In the absence of electrolytes, the apparent activation energy of the dielectric constant decreased by the increase in halothane concentrations. In the presence of electrolytes, however, the addition of halothane increased the apparent activation energy. We propose that the adsorption of halothane on the vesicle surface produces two effects: (1) destruction of the hydration shell, and (2) increase in the binding of electrolytes to the vesicle surface. In the absence of electrolytes, the first effect predominates and the apparent activation energy is decreased. In the presence of electrolytes, the latter effect predominates and the apparent activation energy is increased.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1992

Alcohol interaction with high entropy states of macromolecules: critical temperature hypothesis for anesthesia cutoff.

Nerve excitation generates heat and decreases the entropy (review by Ritchie and Keynes (1985) Q. Rev. Biophys. 18, 451-476). The data suggest the existence of at least two thermodynamically identifiable states: resting and excited, with a thermotropic transition between the two. We envision that nerve excitation is a transition between the two states of the excitation machinery consisting of proteins and lipids, rather than the sodium channel protein alone. Presumably, both proteins and lipids change their conformation at excitation. We proposed (Kaminoh et al. (1991) Ann. N.Y. Acad. Sci. 625, 315-317) that anesthesia occurs when compounds have a higher affinity to the resting state than to the excited state of excitable membranes, and that there is a critical temperature above which the affinity to the excited state becomes greater than to the resting state. When the temperature exceeds this critical level, compounds lose their anesthetic potency. We used thermotropic phase-transition of macromolecules as a model for the excitation process. Anesthetic alcohols decreased the main transition temperature of dipalmitoylphosphatidylcholine (DPPC) membranes and also the temperature of the alpha-helix to beta-sheet transition of poly(L-lysine). The affinity of alcohols to the high- and low-temperature states of the DPPC membranes were separately estimated. The difference in the affinity of n-alcohols to the liquid (high-temperature) and solid (low-temperature) states correlated with their anesthetic potency. It is not the total number of bound anesthetic molecules that determines the anesthesia, rather, the difference in the affinity between the higher and lower entropy states determines the effects. The critical temperatures of the long-chain alcohols were found to be lower than those of the short-chain alcohols. Cutoff occurs when the critical temperature of long-chain alcohols is below the physiological temperature, such that the anesthetic potency is not manifested in the experimental temperature range.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1992

The alpha-helix to beta-sheet transition in poly(L-lysine): effects of anesthetics and high pressure.

Poly(L-lysine) exists in a random-coil formation at a low pH, alpha-helix at a pH above 10.6, and transforms into beta-sheet when the alpha-helix polylysine is heated. Each conformation is clearly distinguishable in the amide-I band of the infrared spectrum. The thermotropic alpha-to-beta transition was studied by using differential scanning calorimetry. At pH 10.6, the transition temperature was 43.5 degrees C and the transition enthalpy was 170 cal/mol residue. At pH 11.85, the measurements were 36.7 degrees C and 910 cal/mol residue, respectively. Volatile anesthetics (chloroform, halothane, isoflurane and enflurane) partially transformed alpha-helix polylysine into beta-sheet. The transformation was reversed by the application of hydrostatic pressure in the range of 100-350 atm. Apparently, the alpha-to-beta transition was induced by anesthetics through partial dehydration of the peptide side-chains (beta-sheet surface is less hydrated than alpha-helix). High pressure reversed this process by re-hydrating the peptide. Because the membrane spanning domains of channel and receptor proteins are predominantly in the alpha-helix conformation, anesthetics may suppress the activity of excitable cells by transforming them into a less than optimal structure for electrogenic ion transport and neurotransmission. Proteins and lipid membranes maintain their structural integrity by interaction with water. That which attenuates the interaction will destabilize the structure. These data suggest that anesthetics alter macromolecular conformations essentially by a solvent effect, thereby destroying the solvation water shell surrounding macromolecules.

Anesthetics↗