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Biomedical subjects

A Takai

Publications and source records attributed to A Takai.

At least 19 recordsLinked to original sources
PubMed2006

Agonist and antagonist sensitivity of non-selective cation channel currents evoked by muscarinic receptor stimulation in bovine ciliary muscle cells.

1 In the bovine ciliary muscle, stimulation of muscarinic receptors with carbachol (CCh) opens two types of non-selective cation channels (NSCCS and NSCCL) with widely different unitary conductances (100 fS and 35 pS). Here we examined the dependence of the activity of NSCCS on the agonist (CCh) concentration by whole-cell voltage clamp in freshly isolated bovine ciliary muscle cells. We also examined the sensitivity of CCh-evoked NSCCS currents to several muscarinic receptor antagonists. 2 The voltage clamp experiments were carried out using Ba2+ as the charge carrier, as this divalent cation is the most permeant for NSCCS of the alkali and alkaline earth metal ions hitherto examined, whereas it is relatively impermeant to NSCCL. For the dose-activation relationship obtained, the apparent dissociation constant K was estimated to be 0.5 +/- 0.2 microm (n = 31), a value of an order of magnitude smaller than the one reported for CCh-evoked NSCCL currents in our previous experiments. 3 In the dose-inhibition experiments we observed that the CCh-evoked NSCCS currents were inhibited by the muscarinic antagonists with the following potency sequence: atropine approximately 4-DAMP >> pirenzepine > AF-DX116, indicating that the activation of NSCCS by CCh is mediated by an M3 muscarinic receptor. 4 We have previously shown by reverse transcriptase-polymerase chain reaction that the bovine ciliary muscle contains mRNAs for several transient receptor potential channel homologues (TRPC1, TRPC3, TRPC4 and TRPC6) which are attracting attention as molecular candidates for receptor-operated NSCCs. In the present experiments, we succeeded in visually identifying these TRPCs in the plasma membrane of cultured bovine ciliary muscle cells by immunofluorescence microscopy.

Animals↗
PubMed2002

Regulation of cardiac CFTR Cl(-) channel activity by a Mg(2+)-dependent protein phosphatase.

Dephosphorylation of the CFTR Cl(-) channel is known to be induced by both okadaic-acid- (OA-) sensitive and -insensitive protein phosphatases (PPs). In the present study, the effects of cytosolic free Mg(2+) on the cardiac CFTR Cl(-) current were examined in relation to the latter PP activity in guinea pig ventricular myocytes. Even when maintaining intracellular Mg-ATP at millimolar concentrations under whole-cell patch-clamp mode, cAMP-activated Cl(-) conductance was reversibly suppressed by cytosolic free Mg(2+), with an IC(50) of around 2.5 mmol/l. In contrast, changes in the cytosolic concentration of free Mg(2+) ([Mg(2+)](i)) had no effect on genistein-activated CFTR Cl(-) currents. The Mg(2+) effect on cAMP-activated CFTR Cl(-) conductance was completely reversed by application of anthracene-9-carboxylic acid (9-AC), which was previously shown to inhibit an OA-insensitive PP in cardiac myocytes. A 9-AC-sensitive fraction of endogenous PP activity in the extract of guinea pig ventricle was found to be activated by free Mg(2+) at millimolar concentrations but to be inactive at micromolar concentrations. The intracellular application of OA failed to activate basal Cl(-) conductance at millimolar [Mg(2+)](i). In the presence of OA, however, basal Cl(-) conductance became activated either by reducing [Mg(2+)](i) to micromolar concentrations or by applying 9-AC. Thus, we conclude that a Mg(2+)-dependent PP sensitive to 9-AC plays a key role in the cAMP-mediated regulation of cardiac CFTR Cl(-) channel at physiological [Mg(2+)](i)under both basal and cAMP-activated conditions. Also, it appears that the genistein-activated conformation of the cardiac CFTR channel is not sensitive to the Mg(2+)-dependent PP.

Adenosine Triphosphate↗
PubMed2001

Reliability and validity of Kasahara's scale of melancholic type of personality (Typus melancholicus) in a German sample population.

We explored the reliability and validity of Kasahara's scale of melancholic type of personality (KMT) in a German sample population. Subjects comprised 66 patients diagnosed with an affective disorder (F3, ICD-10) and 94 controls. Concerning reliability, KMT scores showed internal consistency with Cronbach's alpha coefficients of 0.65 for patients and 0.67 for controls. The KMT items, except for number 13 in controls, showed significant item-total correlations. In a test-retest procedure, the KMT total score and individual item scores were statistically similar and correlated. These results indicate reliability of the KMT. Concerning validity, KMT scores were significantly higher in patients than in controls. By controlling the effects of age and sex, partial correlation coefficients in a comparison of KMT and Zerssen's F-List (F-List) scores were 0.40 in patients and 0.53 in controls. These results show both the constructive and concurrent validity of the KMT. Sufficient reliability and validity of the KMT were shown in this German sample population to encourage cross-cultural investigation of Typus melancholicus.

Adult↗
PubMed2000

Effects of modification of the hydrophobic C-1-C-16 segment of tautomycin on its affinity to type-1 and type-2A protein phosphatases.

Among the naturally occurring toxins that are known to have specific inhibitory effects on type-1 and type-2A protein phosphatases (PP1 and PP2A), tautomycin (TM) is unique in that it exhibits significantly higher affinity to PP1 than to PP2A. The ratio of the dissociation constant for the PP1-TM interaction to that for the PP2A-TM interaction (the PP1/PP2A ratio) is 0.01-0.03. The aim of the present study was to evaluate the possible contributions of the C-1-C-16 segment of TM to the affinity characteristics of the toxin. The relatively hydrophobic segment contains a spiroketal motif whose enantiomeric form is present in okadaic acid (OA), which exhibits exceedingly higher affinity to PP2A than to PP1. We therefore synthesized two TM analogues: TM1 in which the side chains of the spiroketal motif of TM were removed but its absolute configuration was retained, and TM2 in which the spiroketal motif of TM1 was replaced with its enantiomeric form. The effects of TM, TM1 and TM2 on the activities of the native catalytic subunits of PP1 (PP1C) and PP2A and a recombinant gamma isoform of PP1 (PP1gamma) were examined. The PP1/PP2A ratio determined thereby was 0.2-0.5 for TM1 and 5-10 for TM2. Both the presence of the side chains and the stereochemistry of the spiroketal moieties may be major determining factors for the affinity characteristics of TM. We also show that a monoclonal antibody raised against OA binds to TM2 albeit with much lower affinity than to OA, whereas it exhibits no measurable affinities to TM and TM1.

Antifungal Agents↗
PubMed2000

Chromosome evolution involving Robertsonian rearrangements in Xyrichthys fish (Labridae, Perciformes).

Three Xyrichthys fish (Labridae, Perciformes), X. pavo, X. dea, and X. twistii, were cytogenetically studied. X. pavo and X. dea had 2n = 44 chromosomes, which were all acrocentric. X. twistii had 2n = 22 chromosomes consisting of eighteen meta- and submetacentric and four acrocentric chromosomes. The cellular DNA contents of X. pavo and X. twistii measured using flow cytometry were nearly equal. These results suggest that the karyotype of X. twistii evolved by decreasing the number of chromosomes by fusion events, probably Robertsonian fusion. Cytogenetic relationships among the three species were surmized on the basis of features on the karyotypes and the NOR locations. A large gap in the chromosome number between 2n = 44 and 2n = 22 is an interesting feature related to the process of chromosome evolution.

Animals↗
PubMed1999

Mental health problems after stroke.

We investigated the mental health of 47 subjects (30 men, mean age 63.8+/-7.7; 17 women, mean age 68.9+/-8.7) with the 60-item General Health Questionnaire (GHQ). All the subjects lived at home in a Japanese rural community and were examined from 2 to 3 years after suffering a stroke. Among the subjects, 18 (38.3%) had GHQ scores of 17 or more, which indicated a mental health problem (MHP). The following variables were included in multiple logistic regression analysis: age, sex (men/women), grade of motor paralysis (no/slight/moderate/severe), side of motor paralysis (no/left side/right side/both sides: in analysis, we used dummy variables), paresthesia (no/yes), rehabilitation (need no rehabilitation or participate in rehabilitation/fail to participate in rehabilitation), social support (not needed or sufficient/insufficient) and overall physical recovery (1/2/3: 1 = 67-100, 2 = 34-66, and 3 = 0-33 on a visual analog scale 100 mm long, 100 meaning full recovery). In univariate analysis all variables except age and sex showed statistically significant associations with MHP. In multivariate analysis, only one variable, overall physical recovery', had a statistically independent association with the status of MHP (Odds ratio 4.39, 95% confidence interval 1.46-13.19). The results of logistic regression analysis indicate that the presence of an MHP is more strongly dependent upon subjective assessment about overall physical recovery after stroke than upon physical impairments and the other psychosocial variables. Therefore, in the community setting, the visual analog scale of overall physical recovery is considered to be a simple, valid method for assessing MHP following stroke.

Aged↗
PubMed1999

Effects of iodoacetate on spontaneous electrical activity, slow wave, in the circular muscle of the guinea-pig gastric antrum.

In the circular muscle of the guinea-pig gastric antrum, the contribution of glycolysis to spontaneous electrical activity, slow wave, was studied. The slow wave could be maintained without a marked change in glucose-free solution for more than 1 h even when treated with iodoacetic acid (IAA, 0.1-0.5 mM). However, reapplication of glucose following the IAA treatment produced clear inhibitory effects on the slow wave. Lactate release from the tissue was reduced to about 10% of the control by IAA (0.1 mM) in the absence of glucose and there was very slow recovery on glucose reapplication. This suggests that IAA did not block glycolysis completely and that the inhibition of slow wave was mainly due to the accumulation of some metabolites. Small electrical activity often remained during the inhibition by IAA and glucose. When the excitability of the smooth muscle was increased by Co(2+) application or Na(+) removal, slow wave-like activity could be generated under the condition in which the slow wave was strongly inhibited by IAA and glucose. These results may be explained by assuming that the accumulation of glycolytic metabolites decreases the excitability of smooth muscle cells and also reduces the driving potential generated in the interstitial cells of Cajal to a subthreshold level for the slow wave in the smooth muscle cells.

Animals↗
PubMed1999

Effects of specific modifications of several hydroxyls of tetrodotoxin on its affinity to rat brain membrane.

The widely used sodium channel blocker tetrodotoxin (TTX) is a compound that has six hydroxyl residues at the C-4, C-6, C-8, C-9, C-10, and C-11 positions in addition to a guanidinium group, which is positively charged in biological pH range. Thirteen analogs of this toxin with structural modifications involving one or more of these hydroxyls were examined on their affinity to a rat brain membrane preparation, which is known to contain sodium channels abundantly. The equilibrium dissociation constants associated with the binding of TTX and its analogs to the sodium channels were estimated, from their ability to inhibit the binding of [3H]saxitoxin, as follows (in nM): TTX, 1.8; chiriquitoxin, 1.0; 11-oxoTTX, 1.5; 11-norTTX-6,6-diol, 1.6; 11-norTTX-6(S)-ol, 23; 11-norTTX-6(R)-ol, 31; 11-deoxyTTX, 37; 6-epiTTX, 39; 4-epiTTX, 68; 4,9-anhydroTTX, 180; TTX-8-O-hemisuccinate, >380; TTX-11-carboxylic acid, >2300; tetrodonic acid, >3600; 5,6,11-trideoxyTTX, >5000. The reduction of the affinity observed with the analogs involving reduction or translocation of the hydroxyls at C-6 and C-11 is indicative of the contribution of these residues to the binding to sodium channels as hydrogen bond donors. The especially large value of the dissociation constant for TTX-11-carboxylic acid is consistent with the idea that the C-11-hydroxyl forms a hydrogen bond with a carboxylic acid residue of the channel protein. The markedly low affinity of TTX-8-O-hemisuccinate may possibly be ascribable to intramolecular salt-bridge formation, which neutralizes the positive charge of the guanidinium group.

Animals↗
PubMed1998

Development of genotoxicity assay systems that use aquatic organisms.

Our aim is to develop and evaluate monitoring systems that use aquatic organisms to assess the genotoxicity of water in the field and in the laboratory. In a field study, we have shown that the micronucleus assay is applicable to freshwater and marine fishes and that gill cells are more sensitive than hematopoietic cells to micronucleus-inducing agents. Gill cells from Carassius sp. (Funa) and Zacco platypus (Oikawa) collected upstream on the Tomio River (Nara, Japan), tended to have lower micronucleus frequencies than gill cells from fish collected at the midstream of the river. Leiognathus nuchalis (Hiiragi) and Ditrema temmincki (Umitanago), small marine fishes collected periodically at Mochimune Harbor (Shizuoka, Japan), showed seasonal differences in the frequencies of micronucleated gill cells and erythrocytes; they were highest in summer. For laboratory studies, we developed a method for analyzing chromosomal aberrations and micronuclei using Rhodeus ocellatus ocellatus (rose bitterling) embryos. One day after artificial insemination (gastrula stage), we observed structural chromosomal aberrations and micronuclei in the cells of embryos grown in water containing trichloroethylene. Although more work is needed to fully assess their sensitivity, these assays show promise as a means of detecting environmental genotoxins.

Animals↗
PubMed1998

Life-time prevalence and risk factors of tobacco/nicotine dependence in male ever-smokers in Japan.

UNLABELLED: To estimate the life-time prevalence rate of tobacco/nicotine dependence and demographic variables and smoking habits associated with the disorder in male ever-smokers in Japan. DESIGN: A cross-sectional community-based interview study. SETTING: Takayama city, Gifu Prefecture, Japan. PARTICIPANTS: A total of 170 male ever-smokers aged 35 years or older selected randomly from a community in Japan were interviewed. The response rate was 85%. MEASUREMENTS: The WHO Composite International Diagnostic Interview (CIDI) was used to make diagnoses of tobacco/nicotine dependence according t ICD-10, DSM-III-R and DSM-IV. The Fagerstrom Tolerance Questionnaire (FTQ) was also administered and those who had a FTQ score of 7 or above were identified. FINDINGS: The life-time prevalence rates of tobacco/nicotine dependence in male ever-smokers were 42%, 26% and 32% according to ICD-10, DSM-III-R and DSM-IV criteria, respectively; 19% had a FTQ score of 7 or above. The ICD-10 diagnosis was significantly and negatively associated with quitting smoking (p < 0.05). Multiple logistic regression analyses indicated that number of cigarettes per day when they smoked the most was significantly associated with higher life-time risks of the disorder according to DSM-III-R, DSM-IV and Fagerstrom's classification (p < 0.05). The length of cigarette smoked was associated with higher life-time risks of ICD-10 and DSM-IV diagnoses, and years of smoking were associated with higher life-time risks of ICD-10, DSM-III-R and DSM-IV diagnoses (p < 0.05). Younger birth cohorts had higher cumulative rates of the disorder according to DSM-IV (p for trend < 0.05). CONCLUSIONS: Life-time prevalence rates of tobacco/nicotine dependence according to ICD-10, DSM-III-R and DSM-IV in male ever-smokers in Japan were within the range of rates reported in previous US studies; rates of FTQ score of 7 or above were lower. Fagerstrom scores and diagnostic criteria appear to reflect different aspects of dependence.

Adult↗
PubMed1998

Correlation between history of contact with people living with HIV/AIDS (PWAs) and tolerant attitudes toward HIV/AIDS and PWAs in rural Thailand.

This study examines the hypothesis that people who have more contact with PWAs (people living with AIDS) are more tolerant than those who have no contact with them. Four provinces with different incidence of AIDS in 4 different regions of Thailand were selected. Structured questionnaire interviews were conducted with village people, asking about their history of contact with PWAs, and knowledge and attitudes toward HIV/AIDS and PWAs (n = 434). An 'Attitude Score', which indicates an accepting attitude (or tolerance) toward HIV/AIDS and PWAs, was developed using the results of the questionnaire on attitudes. Six factors: sex, education, age, province, knowledge, and history of contact with PWAs were positively correlated with the Attitude Score. After a multiple regression analysis, contact with PWAs was significantly associated with Attitude Score. This study is one of the first analytical studies conducted in a non-Western country to show that people's tolerant attitudes towards HIV/AIDS and PWAs are positively related to their history of contact with HIV/AIDS and PWAs. This findings should have important implications for future educational programmes and preventative intervention.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Phosphorylated retinoblastoma protein stimulates DNA polymerase alpha.

Human retinoblastoma (Rb) protein, immunopurified from an extract of recombinant baculovirus infected cells, stimulated 10-100-fold the activity of DNA polymerase alpha from calf thymus or human HeLa cells. Purified Rb protein is composed of two electrophoretically distinguishable forms, i.e., partially phosphorylated and under-phosphorylated forms. Dephosphorylation of Rb protein by protein phosphatase 2A largely diminished its stimulatory effect. On the other hand, a hyperphosphorylated Rb protein, obtained from insect cells overexpressing Rb protein, cyclin E and cyclin-dependent kinase 2 simultaneously, stimulated DNA polymerase alpha more strongly than the singly-expressed Rb protein. These results indicate that the phosphorylation is crucial for the stimulation. Rb protein isolated from human Burkitt lymphoma Raji cells also stimulated DNA polymerase alpha. In contrast, Rb protein did not affect eukaryotic DNA primase or Klenow fragment of Escherichia coli DNA polymerase I. By immunoprecipitation using anti-DNA polymerase alpha antibody, Rb protein in nuclear extract of Raji cells was co-precipitated with DNA polymerase alpha. This result indicates that DNA polymerase alpha exists as a complex containing phosphorylated Rb protein in cells. DNA polymerase alpha specifically bound to a purified Rb protein-immobilized Sepharose column. Rb protein also bound to DNA polymerase alpha trapped to anti-DNA polymerase alpha antibody-Sepharose column, suggesting the direct association of these two proteins. These observations suggest a new function of phosphorylated Rb protein in the regulation of DNA replication.

Burkitt Lymphoma↗
PubMed1997

Activation of non-selective cation conductance by carbachol in freshly isolated bovine ciliary muscle cells.

In smooth muscle cells freshly isolated from the bovine ciliary body, effects of carbachol (CCh) on the membrane potential and current were examined by the whole-cell clamp method. The resting membrane potential of the muscle cells used was -60 +/- 1 mV (n = 111). Extracellular application of CCh (2 microM) depolarized the cells to -15 +/- 5 mV (n = 50) with an apparent increase in membrane conductance. Under voltage-clamp conditions, CCh (2 microM) evoked an inward current which exhibited inward-going rectification and reversed the polarity at about 0 mV. Removal of Na+ from the external solution caused a reduction of the amplitude of the current and a shift of the reversal potential to the negative direction. CCh was able to elicit an inward current even under a condition where Ca2+ was the only cation producing an inwardly directed electrochemical gradient. The current was not affected by verapamil or by tetrodotoxin. The CCh-induced current was inhibited by antimuscarinic agents with the affinity sequence: atropine approximately 4-DAMP > > pirenzepine > AF-DX116, indicating that the response is mediated by a muscarinic cholinoceptor that belongs to the M3-subtype. Unlike the non-selective cation channel current in intestinal smooth muscles, which is activated by elevation of the intracellular Ca2+ concentration ([Ca2+]i), the current of the ciliary muscle was inactivated when the [Ca2+]i was increased. The conductance, which admits Ca2+, may serve as a pathway for Ca2+ entry required for contraction.

Animals↗
PubMed1997

Phosphatase-mediated enhancement of cardiac cAMP-activated Cl-conductance by a Cl- channel blocker, anthracene-9-carboxylate.

An aromatic carboxylate, anthracene-9-carboxylic acid (9-AC), is known as a Cl- channel blocker. However, variable 9-AC effects have hitherto been reported on the cardiac cAMP-activated Cl- conductance, when applied extracellularly. We have reexamined the 9-AC effect on the Cl-conductance activated by isoproterenol or forskolin in guinea pig ventricular myocytes under whole-cell patch-clamp conditions. The inward current was blocked by 9-AC at > or = 0.5 mmol/L, but in contrast, the outward current was enhanced at much lower concentrations (ED50, approximately 13 mumol/L). 9-AC applied by the intracellular perfusion technique increased both the inward and outward currents. In the presence of intracellular 9-AC, deactivation of the conductance after washout of isoproterenol or forskolin was largely prevented. 9-AC produced an enhancing effect, even after inhibiting the deactivation process by okadaic acid (OA), whereas it failed to produce additional-effects in the presence of orthovanadate. Intracellular application of 9-AC together with OA virtually abolished the current deactivation. The 9-AC effects on the Cl-conductance were not dependent on intracellular Ca2+ or pH. Putative inhibitors of alkaline (bromotetramisole) and acid phosphatases (tartrate) were without effect. 9-AC failed to inhibit the activities of purified protein phosphatase (PP)-1, -2A, and -2C. In the extract of guinea pig ventricle, 9-AC (> or = 10 mumol/L for full action) significantly inhibited a fraction of endogenous phosphatase activity that was sensitive to orthovanadate but not to OA, bromotetramisole, and tartrate. It is concluded that 9-AC blocks cardiac cAMP-activated (cystic fibrosis transmembrane conductance regulator) Cl- conductance from the extracellular side but enhances the conductance from the intracellular side by inhibiting an orthovanadate-sensitive phosphatase distinct from PP-1, -2A, -2B, or -2C and alkaline or acid phosphatase.

Adenosine Monophosphate↗
PubMed1996

Positive association between a DNA sequence variant in the serotonin 2A receptor gene and schizophrenia.

Sixty-two patients with schizophrenia and 96 normal controls were investigated for genetic association with restriction fragment length polymorphisms (RFLPs) in the serotonin receptor genes. A positive association between the serotonin 2A receptor gene (HTR2A) and schizophrenia was found, but not between schizophrenia and the serotonin 1A receptor gene. The positive association we report here would suggest that the DNA region with susceptibility to schizophrenia lies in the HTR2A on the long arm of chromosomes 13.

Adult↗
PubMed1995

Inhibition of specific binding of okadaic acid to protein phosphatase 2A by microcystin-LR, calyculin-A and tautomycin: method of analysis of interactions of tight-binding ligands with target protein.

Several groups have reported that okadaic acid (OA) and some other tight-binding protein phosphatase inhibitors including microcystin-LR (MCLR), calyculin-A and tautomycin prevent each other from binding to protein phosphatase 2A (PP2A). In this paper, we have introduced an improved procedure for examining to what extent the affinity of an enzyme for a labelled tight-binding ligand is reduced by binding of an unlabelled tight-binding, ligand to the enzyme. Using this procedure, we have analysed the dose-dependent reduction of PP2A binding of [24-3H]OA by addition of OA, MCLR, calyculin-A and tautomycin. The results indicate that the binding of the unlabelled inhibitors to the PP2A molecule causes a dramatic (10(6)-10(8)-fold) increase in the dissociation constant associated with the interaction of [24-3H]OA and PP2A. This suggests that OA and the other inhibitors bind to PP2A in a mutually exclusive manner. The protein phosphatase inhibitors may share the same binding site on the PP2A molecule. We have also measured values of the dissociation constant (Ki) for the interaction of these toxins with protein phosphatase 1 (PP1). For MCLR and calyculin-A, the ratio of the Ki value obtained for PP1 to that for PP2A was in the range 4-9, whereas it was 0.01-0.02 for tautomycin. The value of tautomycin is considerably smaller than that (0.4) calculated from previously reported Ki values.

Antifungal Agents↗
PubMed1995

Influence of occlusal force and mandibular position on tooth contacts in lateral excursive movements.

The diagnosis and treatment of occlusal disharmonies requires an understanding of the variables that affect occluding tooth contacts. Quantitative recordings of tooth contacts and near tooth contacts are necessary for detailed analysis of occlusion. In this study, different thicknesses of registration strips were used to assess the influence of occlusal force and mandibular position on tooth contacts and clearance. This assessment was made for nonworking side molars and working side premolars. There was a significant decrease in clearance with increased occlusal force on both the nonworking and the working sides. A significant increase of clearance was noted as the mandible moved to the most lateral position on the nonworking side. These results indicate that the variables of occlusal force and mandibular position represent potential sources of disparity in the recording of tooth contacts. These variables should be considered when occlusal examination procedures are conducted.

Adult↗