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Biomedical subjects

I Ueda

Publications and source records attributed to I Ueda.

At least 19 recordsLinked to original sources
PubMed2005

Local anesthetics facilitate ion transport across lipid planar bilayer membranes under an electric field: dependence on type of lipid bilayer.

In order to elucidate the role of structural change of lipid membrane bilayer in the mode of action of local anesthetic, we studied the effects of local anesthetics, charged tetracaine and uncharged benzocaine, on ion permeability across various lipid planar bilayers (PC, mixed PC/PS (4/1, mol/mol); mixed PC/PE (1/1, mol/mol); mixed PC/SM (4/1, mol/mol)) under a constant applied voltage. The membrane conductances increased in the order of PC<<PC/PS<or=PC/SM<<PC/PE. When the constant voltage of -100 or -70 mV was applied through the lipid bilayer membranes in the presence of positively charged tetracaine, the fluctuating current pulses with the large amplitude generated, but not appeared in the absence of tetracaine. The addition of uncharged benzocaine generated the fluctuating currents with the small amplitude. Both charged tetracaine and uncharged benzocaine facilitated electrophoretically the transport of small ions such as KCl in the buffer solution through the fluctuating pores in the lipid bilayer membranes formed by interaction with the local anesthetic under the negative applied membrane potential. The current pulses also contained actual transport of charged tetracaine together with the transport of the small ions. The amplitude and the duration time of the electrical current generated by adding the local anesthetics were dependent on the type of the lipid, the applied voltage and its voltage polarity.

Anesthetics, Local↗
PubMed2004

Identification of novel MUNC13-4 mutations in familial haemophagocytic lymphohistiocytosis and functional analysis of MUNC13-4-deficient cytotoxic T lymphocytes.

BACKGROUND: Familial haemophagocytic lymphohistiocytosis (FHL) has an autosomal recessive mode of inheritance and consists of at least three subtypes. FHL2 subtype with perforin (PRF1) mutation accounts for 30% of all FHL cases, while FHL with MUNC13-4 mutation was recently identified and designated as FHL3 subtype. OBJECTIVE: To examine MUNC13-4 mutations and the cytotoxic function of MUNC13-4 deficient T lymphocytes in Japanese FHL patients METHODS: Mutations of MUNC13-4 and the cytotoxicity of MUNC13-4-deficient cytotoxic T lymphocytes (CTL) were analysed in 16 Japanese families with non-FHL2 subtype. RESULTS: Five new mutations of the MUNC13-4 gene were identified in six families. The mutations were in the introns 4, 9, and 18, and exons 8 and 19. Two families had homozygous mutations, while the remaining four had compound heterozygous mutations. Cytotoxicity of MUNC13-4 deficient CTL was low compared with control CTL, but was still present. Clinically, the onset of disease tended to occur late; moreover, natural killer cell activity was not deficient in some FHL3 patients. CONCLUSIONS: MUNC13-4 mutations play a role in the development of FHL3 through a defective cytotoxic pathway.

Age of Onset↗
PubMed2002

Measurements of cosmic-ray low-energy antiproton and proton spectra in a transient period of solar field reversal.

The energy spectra of cosmic-ray low-energy antiprotons ( *p's) and protons ( p's) have been measured by BESS in 1999 and 2000, during a period covering reversal at the solar magnetic field. Based on these measurements, a sudden increase of the *p/p flux ratio following the solar magnetic field reversal was observed, and it generally agrees with a drift model of the solar modulation.

Journal Article↗
PubMed2001

ATP synthase F(1) sector rotation. Defective torque generation in the beta subunit Ser-174 to Phe mutant and its suppression by second mutations.

Subunit gamma of the ATP synthase F(1) sector is located at the center of the alpha(3)beta(3) hexamer and rotates unidirectionally during ATP hydrolysis, generating the rotational torque of approximately 45 pN.nm. A mutant F(1) with the betaSer-174 to Phe substitution (betaS174F) in the beta subunit generated lower torque ( approximately 17 pN.nm), indicating that betaS174F is mechanically defective, the first such mutant reported. The defective rotation of betaS174F was suppressed by a second-site mutation, betaGly-149 to Ala, betaIle-163 to Ala, or betaIle-166 to Ala in the same subunit, but not by betaLeu-238 to Ala. These results suggest that the region between betaGly-149 and betaSer-174 plays an important role in the coupling between ATP hydrolysis and mechanical work.

Actins↗
PubMed2001

Activation of connexin-43 hemichannels can elevate [Ca(2+)]i and [Na(+)]i in rabbit ventricular myocytes during metabolic inhibition.

ATP depletion due to ischemia or metabolic inhibition (MI) causes Na(+) and Ca(2+) accumulation in myocytes, which may be in part due to opening of connexin-43 hemichannels. Halothane (H) has been shown to reduce conductance of connexin-43 hemichannels and to protect the heart against ischemic injury. We therefore investigated the effect of halothane on [Ca(2+)]i and [Na(+)]i in myocytes during MI. Isolated rabbit left ventricular myocytes were loaded with 4 microM fluo-3 AM for 30 min, or with 5 microM sodium green AM for 60 min at 37 degrees C. After washing, the myocytes were exposed to: (1) Normal HEPES solution; (2) MI solution (2 mM NaCN, 20 mM 2-deoxy-D-glucose and 0-glucose); or (3) MI+H (0.95 mM, 4.7 mM) for 60 min. Propidium iodide (PI, 25 microM) was added to all samples before data acquisition. The fluorescence intensity was measured by flow cytometry with 488 nm excitation and 530 nm emission for fluo-3 or sodium green, and 670 nm for PI. The [Ca(2+)]i and [Na(+)]i were then calculated by calibration. In some experiments, the effect of 10 microM tetrodotoxin (TTX) and 20 microM nifedipine (NIF) were studied. Metabolic inhibition for 60 min caused a significant increase in [Ca(2+)]i and [Na(+)]i in myocytes when compared to controls, which was significantly reduced by halothane in a dose-dependent fashion. In the presence of TTX and NIF, halothane also significantly reduced the rise in the [Ca(2+)]i and [Na(+)]i in myocytes subjected to MI. 1-heptanol, another gap junction blocker, had similar effects. Thus, halothane reduced [Ca(2+)]i and [Na(+)]i overload produced by MI in myocytes. This effect is not solely due to block of voltage-gated Na(+) and Ca(2+) channels, and is likely mediated by inhibiting the opening of connexin-43 hemichannels.

Anesthetics, Inhalation↗
PubMed2001

Volumetric study on the protein-anesthetic binding.

Thermodynamic equations describing the volume behavior of protein-ligand mixtures in water were derived. In order to estimate the volume and binding parameters, the equations were combined with a Langmuir-type binding isotherm. Densities of aqueous solutions of mixtures of bovine serum albumin (BSA) and octanol (C8OH) were measured as a function of total BSA molality, m(M)(T), at constant total C8OH molalities, m(X)(T). The data were analyzed by the equations. The partial molar volumes at infinite dilution of BSA and C8OH, V(M)(T,0) and V(X)(T,0), respectively, were estimated. It was seen that V(M)(T,0) decreases by the addition of C8OH to the solution and that V(X)(T,0) decreases gradually with increasing m(M)(T) and approaches asymptotically to a certain value at high m(M)(T). From the concentration dependence of V(M)(T,0) and V(X)(T,0), the values of the association constant K=392 kg mol(-1), the maximum binding number b(max)=1.9, and the volume change DeltaV=-109 cm(3) mol(-1) were obtained for BSA-C8OH interaction in water. The negative value of DeltaV indicates that the hydrophobic interaction reduces the protein volume and elevation of pressure promotes BSA-C8OH binding. These results is inconsistent with the pressure reversal of anesthesia.

Journal Article↗
PubMed2001

Molecular mechanisms of anesthesia.

Anesthesia was a blessing to humankind. It is a miracle that simple molecules such as chloroform (CHCl3), diethyl ether (CH3.CH2.O.CH2.CH3), or nitrous oxide (N2O) induce a state of unconsciousness where patients can tolerate surgery. The diversity of the structures of these molecules indicates that there are no common receptors. The action of anesthetics is nonspecific and physical. After the demonstration by Meyer and Overton that anesthetic potencies correlate to their solubility into olive oil, the nonspecific lipid theories monopolized anesthesia theories for almost a century. The dominance of lipid theories invited repulsions against the nonspecificity idea. Protein theories that stress receptor bindings became the top mode. Nevertheless, the wide varieties of anesthetic molecules and the wide varieties of responding systems are difficult to reconcile with the specific interaction concept. This article discusses the recent progress and controversies on the molecular mechanisms of anesthesia. Anesthetics are unique drugs in pharmacology. They affect all macromolecules. The only comparable drugs are disinfectants. Both are nonspecific drugs. We use alcohols and phenols to wipe off the injection sites. We do not use penicillin or any other antibiotics for this purpose, because they are specific binders. Interestingly, these two nonspecific drugs opened the window for the modern medicine.

Anesthesia↗
PubMed2000

Caenorhabditis elegans senses protons through amphid chemosensory neurons: proton signals elicit avoidance behavior.

Acidic pH is known to cause pain sensation through nociceptive neurons as well as taste transduction in mammals. Caenorhabditis elegans avoids an acidic environment (pH lower than approximately 4.0) formed by organic or inorganic acids. This avoidance behavior was dependent on multiple amphid chemosensory neurons, and inhibited by a mutation of capsaicin receptor homologue, and by the addition of amiloride and ruthenium red (inhibitors of proton-gated Na+ channels and capsaicin receptors, respectively). These results indicate that C. elegans recognizes protons as a nociceptive stimulus, through multiple neurons, which elicits avoidance behavior. It is of special interest that a system similar to that of mammalian signal transduction is responsible for this nematode's acid avoidance.

Amiloride↗
PubMed2000

A biological molecular motor, proton-translocating ATP synthase: multidisciplinary approach for a unique membrane enzyme.

Proton-translocating ATP synthase (F(o)F(1)) synthesizes ATP from ADP and phosphate, coupled with an electrochemical proton gradient across the biological membrane. It has been established that the rotation of a subunit assembly is an essential feature of the enzyme mechanism and that F(o)F(1) can be regarded as a molecular motor. Thus, experimentally, in the reverse direction (ATP hydrolysis), the chemical reaction drives the rotation of a gammaepsilonc(10-14) subunit assembly followed by proton translocation. We discuss our very recent results regarding subunit rotation in Escherichia coli F(o)F(1) with a combined biophysical and mutational approach.

Amino Acid Substitution↗
PubMed2000

Porphyromonas gingivalis fimbriae induce adhesion of monocytic cell line U937 to endothelial cells.

This study used the human monocytic cell line U937 to examine whether or not Porphyromonas gingivalis fimbriae could induce the adhesion of monocytes to endothelial cells. An in vitro adhesion assay was used to investigate the effects of the fimbriae on U937 cell adhesion to human umbilical vein endothelial cells (HUVEC). The fimbriae enhanced U937 cell adhesion to HUVEC in a dose-dependent manner. U937 cells adhered better to HUVEC pretreated with the fimbriae for a minimum of 2 hr than to untreated HUVEC. The enhanced adhesion was inhibited by a monoclonal antibody against P. gingivalis 381 fimbriae. Pretreatment of U937 cells with the fimbriae for 24 hr enhanced U937 cell adhesion to HUVEC approximately 4-fold. This phenomenon was inhibited by an anti-CD11b antibody, suggesting the involvement of CD11b. These results indicate that P. gingivalis fimbriae can induce monocyte adhesion to the endothelial cell surface. They also suggest that the fimbriae may be involved in the initial event for infiltration of monocytes into the periodontal tissues of individuals with adult periodontitis.

Cell Adhesion↗
PubMed2000

Cardiovascular effects of medetomidine, detomidine and xylazine in horses.

The cardiovascular effects of medetomidine, detomidine, and xylazine in horses were studied. Fifteen horses, whose right carotid arteries had previously been surgically raised to a subcutaneous position during general anesthesia were used. Five horses each were given the following 8 treatments: an intravenous injection of 4 doses of medetomidine (3, 5, 7.5, and 10 microg/kg), 3 doses of detomidine (10, 20, and 40 microg/kg), and one dose of xylazine (1 mg/kg). Heart rate decreased, but not statistically significant. Atrio-ventricular block was observed following all treatments and prolonged with detomidine. Cardiac index (CI) and stroke volume (SV) were decreased with all treatments. The CI decreased to about 50% of baseline values for 5 min after 7.5 and 10 microg/kg medetomidine and 1 mg/kg xylazine, for 20 min after 20 microg/kg detomidine, and for 50 min after 40 microg/kg detomidine. All treatments produced an initial hypertension within 2 min of drug administration followed by a significant decrease in arterial blood pressure (ABP) in horses administered 3 to 7.5 microg/kg medetomidine and 1 mg/kg xylazine. Hypertension was significantly prolonged in 20 and 40 microg/kg detomidine. The hypotensive phase was not observed in 10 microg/kg medetomidine or detomidine. The changes in ABP were associated with an increase in peripheral vascular resistance. Respiratory rate was decreased for 40 to 120 min in 5, 7.5, and 10 microg/kg medetomidine and detomidine. The partial pressure of arterial oxygen decreased significantly in 10 microg/kg medetomidine and detomidine, while the partial pressure of arterial carbon dioxide did not change significantly. Medetomidine induced dose-dependent cardiovascular depression similar to detomidine. The cardiovascular effects of medetomidine and xylazine were not as prolonged as that of detomidine.

Adrenergic alpha-Agonists↗
PubMed2000

[Centennial for the Meyer-Overton rule: anesthetics and receptors].

As a backlash to the dominance of lipid theories of anesthesia for almost a century, protein theories are prevalent at present. Lipid theories assume nonspecific interaction with membranes. Protein theories assume specific interaction with specific receptors in specific proteins. The Meyer-Overton rule does not specify the anesthetic action site to lipid membranes. The correlation between the olive oil solubility to the anesthetic potency means that the action sites have similar physical properties to olive oil. It does not discriminate between lipids and proteins. Olive oil is homogeneous (isotropic) liquid whereas membranes and proteins are structured (anisotropic). The physical properties of proteins and membranes are not uniform throughout the structure. The rule shows that the anesthetics bind multiple areas in nonspecific proteins and membranes. The diversity of anesthetic structures is difficult to reconcile with the idea that there is a specific receptor on specific proteins.

Anesthetics↗
PubMed1999

Mechanical rotation of the c subunit oligomer in ATP synthase (F0F1): direct observation.

F0F1, found in mitochondria or bacterial membranes, synthesizes adenosine 5'-triphosphate (ATP) coupling with an electrochemical proton gradient and also reversibly hydrolyzes ATP to form the gradient. An actin filament connected to a c subunit oligomer of F0 was able to rotate by using the energy of ATP hydrolysis. The rotary torque produced by the c subunit oligomer reached about 40 piconewton-nanometers, which is similar to that generated by the gamma subunit in the F1 motor. These results suggest that the gamma and c subunits rotate together during ATP hydrolysis and synthesis. Thus, coupled rotation may be essential for energy coupling between proton transport through F0 and ATP hydrolysis or synthesis in F1.

Actins↗
PubMed1999

Specific and non-specific binding of long-chain fatty acids to firefly luciferase: cutoff at octanoate.

Firefly luciferase emits a burst of light when the substrates luciferin and ATP are mixed in the presence of oxygen. We (I. Ueda, A. Suzuki, Biophys. J. 75 (1998) 1052-1057) reported that long-chain fatty acids are specific inhibitors of firefly luciferase in competition with luciferin in microM ranges. They increased the thermal transition temperature. In contrast, 1-alkanols of the same carbon chain length inhibited the enzyme non-competitively in mM ranges and decreased the transition temperature. The present study showed that the action of fatty acids switched from specific to non-specific when the carbon chain length was reduced below C8 (octanoate). The fatty acids longer than C10 inhibited the enzyme in microM ranges whereas those shorter than C8 required mM ranges to inhibit it. The longer fatty acids increased whereas shorter fatty acids decreased the transition temperature. The Hill coefficients of longer chain bindings were less than one whereas those of shorter chain were more than one. The shorter fatty acids interacted with the enzyme cooperatively at multiple sites. Binding of the longer fatty acids is limited. Fatty acids longer than C10 are high-affinity specific binders and followed Koshland's induced-fit model. Those shorter than C8 are low-affinity non-specific denaturants and followed Eyring's rate process model. These results contradict the general consensus that the size of the receptor cavity discriminates specific binders.

Animals↗
PubMed1999

Does pressure antagonize anesthesia? High-pressure stopped-flow study of firefly luciferase and anatomy of initial flash.

The antagonizing effect of high pressure against anesthesia is well known. With purified firefly luciferase, however,. Biophys. J. 60:1309-1314) reported that high pressure did not affect the initial flash intensity. Firefly luciferase emits a burst of light when the substrates luciferin and ATP are added in the presence of O2. The light intensity decays rapidly and the weak light lasts for hours. The initial flash is a transient event and is not in a steady state. The steady state is represented by the slope of the linear part of the integral of the light output. The present study used a high-pressure stopped-flow system to compare the pressure effects on the initial flash intensity and the steady-state light intensity. The flash intensity did not change by the application of hydrostatic pressure in the presence or absence of chloroform or 1-octanol. In contrast, high pressure increased the steady-state light intensity. The application of 12 MPa pressure increased the steady-state light intensity of firefly luciferase inhibited by 5 mM chloroform or 0.7 mM 1-octanol by 19.7% and 18.8%, respectively. When analyzed by the rapid reaction kinetics of the transition state theory, the initial peak intensity represents the total amount of active enzyme and is unrelated to the reaction rate. Anesthetics inhibited the initial flash by unfolding the protein, thereby decreasing the concentration of the active enzyme. Pressure affected the steady-state light intensity by changing the reaction rates.

Anesthesia↗
PubMed1999

Does pressure antagonize anesthesia? Opposite effects on specific and nonspecific inhibitors of firefly luciferase.

Ueda and Suzuki (1998. Biochim. Biophys. Acta. 1380:313-319; 1998. Biophys. J. 75:1052-1057) reported that myristic acid inhibited firefly luciferase in microM range in competition with luciferin, whereas anesthetics inhibited it in millimeter ranges noncompetitively with luciferin. Myristate increased, whereas anesthetics decreased, the thermal denaturation temperature. The present study showed that high pressure increased the steady-state light intensity of the halothane-doped firefly luciferase but decreased that of the myristate-doped firefly luciferase. The steady-state light intensity showed a maximum at 19.1 degrees C. At 19.1 degrees C, high pressure did not affect the light intensity in the absence of the inhibitors. In the presence of 0.5 mM halothane, however, 25 MPa pressure (maximum effect) increased the light intensity to 106.0% of the control without the inhibitor. In the presence of 2.5 microM myristate, 40 MPa pressure decreased the light intensity to 90.9% of the control. When the temperature was 25 degrees C in the absence of inhibitors, 40 MPa pressure increased the light intensity 119.2% of the ambient value. At 0.5 mM halothane, 40 MPa pressure further increased the light intensity to 106.1% above the control 40 MPa value. At 2.5 microM myristate, 40 MPa pressure decreased the light intensity to 90.1% of the control 40 MPa value. From the pressure dependence of the light intensity, the volume change DeltaV of the enzyme was estimated at 25 degrees C: 0.5 mM halothane increased DeltaV = +3.93 cm3 mol-1, whereas 2.5 microM myristate decreased DeltaV = -7.66 cm3 mol-1. Present results show that there are distinct differences between the specific and nonspecific ligands in their response to high pressure. Myristate, which competes with luciferin, decreased the protein volume and stabilized the conformation against thermal perturbation. Halothane, which does not compete with the substrate, increased the protein volume and destabilized the conformation.

Anesthesia↗