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Biomedical subjects

T Takeuchi

Publications and source records attributed to T Takeuchi.

At least 613 records · Page 34Linked to original sources
PubMed1996

Duration of anti-cholecystokinin (CCK) action on the rat exocrine pancreas of new CCK receptor antagonist FK480 administered orally.

We assessed the duration of the anti-cholecystokinin (CCK) action of FK480, a new non-peptide CCK-A receptor antagonist developed in Japan, in an in vivo study in rats, comparing it with CR 1505. Pancreatic exocrine secretion stimulated by intravenous infusion of CCK-8 (0.06 microgram/kg per h) was measured at intervals of 0-24 h after the oral administration of FK480 (1.5 mg/kg) and CR 1505 (30 mg/kg). FK480 significantly inhibited both CCK-stimulated pancreatic juice volume flow and amylase output 0, 4, 8, and 12 h after oral administration, whereas the inhibitory effect of CR 1505 had completely disappeared by 8 h after oral administration. It was concluded that orally administered FK480 has a prolonged anti-CCK action.

Administration, Oral↗
PubMed1996

Detection and characterization of DNA polymerase activity in Entamoeba histolytica.

DNA polymerase activity was detected and characterized in nuclear extracts from trophozoites of Entamoeba histolytica. The activity was high at pH 2 to pH 6, but at pH 8 and 10 the activity was very low. The presence of K+ was inhibitory for the activity and a higher concentration of K+ markedly inhibited the activity. Magnesium ions (Mg2+) were absolutely required for activity and its optimal concentration was 6 to 8 mM. The activity was markedly inhibited by aphidicolin which is an inhibitor of mammalian DNA polymerases alpha, delta, and epsilon and also by N-ethylmaleimide which is an inhibitor of DNA polymerases, alpha, gamma, delta and epsilon. However, inhibition of the activity by 2', 3'-dideoxythymidine-5'-triphosphate which is an inhibitor of DNA polymerases beta and gamma was relatively weak. Thus sensitivity of the E. histolytica enzyme to these inhibitors was similar to that of mammalian DNA polymerases (alpha, delta and epsilon) of the alpha family. Monoclonal antibodies against human DNA polymerase alpha did not bind to DNA polymerase of E. histolytica.

Animals↗
PubMed1996

Cortical potentials preceding voluntary elbow movement in recovered hemiparesis.

Scalp-recorded movement-related cortical potentials (MRCPs) preceding voluntary elbow flexion were studied in two hemiparetic patients 8 months after a stroke. Both cases had unilateral lenticular and internal capsular vascular lesion sparing the cortex. The motor recovery stage of their paretic arm remained in flexion or extension "synergistic" movements of shoulder, elbow, wrist and fingers. The NS' (negative slope) amplitude preceding voluntary unilateral elbow flexion of the intact arm showed a distinct preponderance over the contralateral precentral area, whereas NS' amplitude preceding flexion of the paretic arm was symmetrically maximal at bilateral precentral areas. It is postulated that the unilateral synergistic elbow flexion of the paretic arm is associated with an activation of bilateral brachial areas of the sensorimotor cortex (SI-MIs), whereas the isolated elbow flexion of the intact arm is associated with an activation of mainly the contralateral SI-MI.

Adult↗
PubMed1996

Inhibition of human immunodeficiency virus type 1 infectivity by a new amine bellenamine.

Bellenamine, (R)-3,6-diamino-N-(aminomethyl)hexanamide (molecular weight 174), produced by Streptomyces nashvillensis, which has been reported to have weak antibacterial activity and to slightly enhance the immune response, showed potent activity against human immunodeficiency virus type 1 (HIV-1). Its mode of action was investigated. Bellenamine inhibited de novo infection of human T cells with HIV-1, at a 50% effective concentration (EC50) of 0.62 micrograms/ml (3.6 microM). Its 50% cytotoxic concentration (CC50) was over 2000 micrograms/ml (11.5 mM) and thus its cytotoxicity was quite low. When HIV-1-infected cells were treated with bellenamine or glycosylation inhibitors, they produced virus with reduced infectivity, and thus bellenamine inhibited the secondary spread of HIV-1 in vitro similarly to glycosylation inhibitors. However, bellenamine did not change the apparent molecular weights of env or gag proteins, unlike glycosylation inhibitors. Bellenamine showed no significant activity against virus adsorption, reverse transcriptase, viral protease or the glycosylation process. The antiviral mechanism of bellenamine remains to be examined further.

Antiviral Agents↗
PubMed1996

Molecular and functional properties of cytochrome c from adult Ascaris suum muscle.

Mitochondrial cytochrome c was isolated at high purity from adult Ascaris suum muscle and its molecular properties were investigated. The molecular weight of A. suum cytochrome c was determined to be 13,119 by electrospray ionization mass spectrometry. The oxidation-reduction potential of nematode cytochrome c was measured to be +248 mV; this value is comparable to those for cytochrome c from mammalian sources. The A. suum cytochrome c, like bovine heart cytochrome c, showed biphasic kinetics against bovine heart cytochrome c oxidase. Comparative kinetic studies revealed species-specificity in the reaction between cytochrome c and cytochrome c oxidase from A. suum and bovine sources. The cytochrome c content in mitochondria was highest at the second larval stage, in which the respiratory chain is the most aerobic among various developmental stages of A. suum. These data clearly show that adult A. suum cytochrome c, as isolated, is a bona fide substrate for cytochrome c oxidase in the aerobic respiratory chain of second-stage larvae.

Age Factors↗
PubMed1996

Proinsulin cleaved by furin is processed to chromatographically mature insulin by carboxypeptidases in nonneuroendocrine cells.

Proinsulin is converted to mature insulin by two reactions, cleavage by the prohormone convertases PC2 and PC3, and removal of basic residues by carboxypeptidase H. These reactions are performed in the secretory granules of pancreatic beta cells. When we replaced the processing sites of proinsulin with furin-cleavable sites, the three nonneuroendocrine cell lines Hep G2, CHO, and NIH/3T3 produced insulin with the same size as synthetic human insulin. Although the three cell lines expressed different quantities of carboxypeptidase H mRNA, the cytosol fractions of the cells exhibited similar levels of carboxypeptidase activity, suggesting that additional carboxypeptidases were active. The insulins resulting from the three cell lines were eluted as a single peak on a cation-exchange chromatography column, indicating that proinsulin can be maturated to insulin even in nonneuroendocrine cells.

3T3 Cells↗
PubMed1996

A comparison of the 8-hydroxydeoxyguanosine, chromosome aberrations and micronucleus techniques for the assessment of the genotoxicity of mercury compounds in human blood lymphocytes.

We compared the mechanism of action of micronuclei (MN), unstable chromosome aberrations, and 8-hydroxydeoxyguanosine (8-OHdG) levels to evaluate the genotoxicity of methyl mercuric chloride (CH3HgCl) and mercuric chloride (HgCl2) in human peripheral lymphocytes. The chromosome aberrations in human peripheral lymphocytes exposed to various concentrations of CH3HgCl or HgCl2 increased in a concentration-dependent manner and were significantly higher than the control when the cells were incubated with 1 x 10(-5) M (HgCl2) or 2 x 10(-6) M (CH3HgCl). The increase in the incidence of micronucleated lymphocytes was significant among the exposed groups, being 2 x 10(-5) M (HgCl2) and 5 x 10(-6) M (CH3HgCl) compared with the control. CH3HgCl was about 4-fold more potent than HgCl2. We determined the 8-OHdG levels in human peripheral blood mononuclear cells(PBMC) and found that they were significantly higher in the exposed groups at 1 x 10(-5) M (HgCl2) and 5 x 10(-6) M (CH3HgCl) compared with the control. A detectable (p < 0.05) increase in the level of 8-OHdG was induced by CH3HgCl at a concentration that was about 50% of the amount of HgCl2 required to produce a similar response. The data confirmed the value of the MN and/or chromosome aberration assays for assessing of HgCl2- and/or CH3HgCl-induced genotoxicity, and indicated that they are about the same concentration as the 8-OHdG assay. The presence of genotoxic effects in peripheral blood lymphocytes exposed to the mercuric compounds indicated by the chromosome aberrations and the MN assays could be partly due either to the disturbance of the spindle mechanism, or to the elevated level of 8-OHdG brought by the generation of reactive oxygen species.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1996

Ipsilateral parotid sparing study in head and neck cancer patients who receive radiation therapy: results after 1 year.

OBJECTIVE: To determine if three-dimensional treatment planning and conformational dose delivery could minimize radiation dose and salivary gland dysfunction to contralateral parotid glands in patients with unilateral head and neck cancers. STUDY DESIGN: Fifteen patients with unilateral head and neck cancers were treated with three-dimensional treatment planning. Unstimulated and stimulated bilateral parotid saliva was collected before radiotherapy, weekly during treatment, and 1, 3, 6, and 12 months after the completion of radiotherapy. RESULTS: Treated parotid glands received an average dose of 4949 cGy, whereas spared glands received only 355 cGy. Unstimulated and stimulated parotid flow rates decreased dramatically in treated glands after the initiation of radiotherapy and were significantly lower at 1 year after radiotherapy compared with baseline. Conversely, parotid flow rates in spared glands underwent mild changes during radiotherapy and were similar at 1 year after radiotherapy compared with baseline. CONCLUSION: Parotid gland function can be preserved for at least 1 year in patients with unilateral head and neck cancers with three-dimensional treatment planning.

Adult↗
PubMed1996

Isolation and synthesis of novel farnesyl protein transferase inhibitors, valinoctins A and B, from Streptomyces strain MJ858-NF3.

Two novel farnesyl protein transferase inhibitors, valinoctins A (1) and B (2), were isolated from the fermentation broth of Streptomyces strain MJ858-NF3. The tentative structures of these compounds were elucidated from NMR and mass spectra as dipeptides consisting of valine and a novel amino acyl moiety. Four possible isomers of valinoctin A were synthesized, and the protected derivative of the appropriate compound was crystallized to give the relative stereochemistry of X-ray analysis. Since the valine residue of valinoctin A was determined to be the L-configuration by a chiral HPLC column, absolute configuration of valinoctin A was determined.

Animals↗
PubMed1996

Uncoupling of biliary lipid from bile acid secretion by formyl-methionyl-leucyl-phenylalanine in the rat.

A neutrophil chemotactic factor N-formyl-methionyl-leucyl-phenylalanine (fMLP), produced by Escherichia coli under conditions of intestinal inflammation, is reported to circulate enterohepatically in the presence of experimental colitis, but its effect on bile secretion is unclear. Therefore, we investigated the effect of fMLP on bile secretion in a single-pass isolated perfused rat liver system. Infusion of fMLP at different concentrations (2 micromol/L, 10 micromol/L, and 20 micromol/L) into the portal vein resulted in excretion into bile in the native form, independent of sodium taurocholate (1 micromol/min) infusion. Excretion of fMLP increased dose dependently, and approximately 12% of the infused dose was detected at each concentration. With constant infusion of sodium taurocholate (1 micromol/min), fMLP (20 micromol/L) increased bile flow but decreased phospholipid and cholesterol secretion. Bile acid secretion was not affected. Phospholipid/bile acid molar ratios decreased from 0.069 +/- 0.002 to 0.038 +/- 0.002, and cholesterol/bile acid molar ratios decreased from 0.0074 +/- 0.0009 to 0.0029 +/- 0.0008. Thus, administration of fMLP resulted in the uncoupling of biliary excretion of phospholipid and cholesterol from that of bile acids; this effect proved reversible. The increase in bile flow caused by fMLP infusion appeared to result from osmotic choleresis. When 25 mg of horseradish peroxidase, a conventional marker of transcytotic vesicle transport pathway, was infused for 1 minute as a pulse load into the portal vein after continuous infusion of taurocholate, its late peak excretion was reduced by fMLP (10 micromol/L) from 9.59 +/- 1.09 to 6.05 +/- 0.66 (ng/g liver). Gel-permeation chromatography of bile showed a specific association of fMLP with bile acids. These results suggest an uncoupling of biliary lipids from bile acids by fMLP because of inhibition of transcellular vesicle transport and interaction between fMLP and bile acid micelles in the bile canaliculus.

Animals↗
PubMed1996

Essential fatty acid requirements in carp.

Till date, many workers have demonstrated the nutritive value of dietary lipids and the qualitative and quantitative requirements for essential fatty acid (EFA) in many cultivable fish. From the data accrued, a categorization can be made for the EFA requirement as follows: Type I (require n-6 fatty acids), Type II (require both n-6 and n-3 fatty acids) and Type III (require n-3 fatty acids). Common carp Cyprinus carpio and grass carp Ctenopharyngodon idella are codified as Type II fish based on their EFA needs. The requirement of both fish for dietary n-6 and n-3 fatty acids is found to be 1% and 0.5-1%, respectively. Our recent experiment clearly indicated that grass carp fed diet without EFA show deficiency symptoms like vertebral column curvature (VCC), indicating lordosis. The manifestation is similar to SEKOKE DISEASE which is characterised by apparent muscular dystrophy. However, grass carp fed an EFA-deficient diet did not exhibit the apparent muscular dystrophy. Recently, we have also investigated the interaction between EFA and vitamin E (VE), and the metabolism of linoleic acid (LA) using the isotope technique. These results are to be reviewed.

Animals↗
PubMed1996

Determination of 8-hydroxydeoxyguanosine in human cells under oxygen-free conditions.

To establish an accurate 8-hydroxydeoxyguanosine (8OHdG) determination system, we examined two potential factors causing experimental error in 8OHdG determination. First, we examined the efficiency of the enzymatic digestion of DNA, that could cause misestimation of 8OHdG. Second, since we considered that the oxygen molecules in atmosphere and in reagents were the main factor contributing to the experimental errors, we carried out the 8OHdG determination under oxygen-free conditions and compared the 8OHdG value with that determined by the methods under ambient atmosphere. The calf thymus DNA was sufficiently digested in the condition we used and the yields of dG were constant, even when the DNA was damaged with H2O2 (80 mM) and UV irradiation. By carrying out the DNA extraction manually, instead of using the DNA extractor, we could reduce the additional 8OHdG formation during sample processing. No trend was found in the difference between the 8OHdG values determined under oxygen-free conditions and under ambient atmosphere. However, when the 8OHdG values were compared in samples with asbestos, the value determined under oxygen-free conditions was significantly lower than that determined under ambient atmosphere. These findings suggest that the removal of oxygen molecules was effective in reducing accidental ROS generation by impurities in the sample, which could cause the additional 8OHdG formation, and that the oxygen-free system made the determination of 8OHdG reproducible and more accurate than before. When the oxygen-free system was applied to human leukocytes, the system showed good reproducibility (r = 0.535, P < 0.001), even though the 8OHdG level was low. With the system, we could detect a significant difference between 8OHdG in polymorphonuclear leukocytes (0.241 +/- 0.129) and mononuclear leukocytes (0.188 +/- 0.126, P < 0.01).

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1996

Relationship between the intracellular reactive oxygen species and the induction of oxidative DNA damage in human neutrophil-like cells.

To clarify the mechanisms of intracellular induction of oxidative DNA damage, we have investigated the concentrations of intracellular reactive oxygen species and the amounts of 8-hydroxydeoxyguanosine (8OHdG), a mutagenic oxidative DNA damage, in human neutrophil-like cells, dimethylsulfoxide-differentiated HL60 (DMSO-HL60). We determined intracellular concentrations of hydrogen peroxide and superoxide by flow cytometry with dichlorofluorescein diacetate and hydroethidine, respectively. We determined the 8OHdG amounts with an electrochemical detector connected to HPLC after anaerobic sample processing. DMSO-HL60 releases superoxide upon stimulation with phorbol myristate acetate, and the released superoxide dismutates to hydrogen peroxide. Stimulation of DMSO-HL60 with 100 nM phorbol myristate acetate increased intracellular hydrogen peroxide, superoxide and 8OHdG (control). Addition of 1000 U/ml catalase decreased hydrogen peroxide (31.3% of control) and 8OHdG (20.3%). Addition of 100 U/ml SOD decreased superoxide (18.7%) and 8OHdG (41.6%). Addition of 1 mM deferoxamine decreased 8OHdG (30.4%), but increased hydrogen peroxide (129.6%). Addition of 200 microM 4-acetamido-4'- isothiocyanostilbene-2,2'-disulfonic acid decreased superoxide (59.9%) and 8OHdG (42.0%). Addition of 0.4% ethanol had no effect on superoxide concentration (102.2%), but tended to decrease hydrogen peroxide (83.5%) and 8OHdG (84.3%). Pretreatment of DMSO-HL60 with 0.1 mM FeSO4 increased 8OHdG (117.3%), but decreased hydrogen peroxide (75.8%). These findings indicate that the extracellularly released superoxide and hydrogen peroxide diffuse into the cell, but that such reactive oxygen species are not the direct molecules to induce 8OHdG. Our results suggest that 8OHdG is induced by the hydroxyl radical which is generated from intracellular hydrogen peroxide and superoxide-reduced Fe.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1996

The in-vitro activity of an antifungal antibiotic benanomicin A in comparison with amphotericin B.

Benanomicin A showed a broad antifungal spectrum, inhibiting the growth of all test strains of 41 yeasts, 23 dimorphic fungi, 23 dematiaceous fungi, 16 aspergilli, and 19 dermatophytes, with the exception of 12 zygomycetic strains. The MIC values of benanomicin A were comparable to those of amphotericin B against Cryptococcus. Rhodotorula, Trichosporon, Geotrichum, Sporothrix, and some dermatophytes, but were two to eightfold higher than those of amphotericin B against other fungal pathogens tested. The action of benanomicin A was fungicidal.

Amphotericin B↗
PubMed1996

Phylogenetic analysis of Streptomyces spp. causing potato scab based on 16S rRNA sequences.

The complete 16S rRNA sequences of 12 strains of Streptomyces spp., including potato scab pathogens, were determined. Among the strains of Streptomyces scabies that were isolated from diverse geographical areas and differed in melanoid pigment production, either no difference or one difference in sequence was observed. The sequence of S. scabies was most similar to the sequences of Streptomyces diastatochromogenes, Streptomyces bottropensis, and Streptomyces neyagawaensis, which belong to the Diastatochromogenes group. The levels of similarity of the 16S rRNA sequences of Streptomyces acidiscabies and S. scabies were almost the same as the levels of similarity between S. acidiscabies and other Streptomyces strains. Streptomyces sp. strain 91-Sy-13, which was isolated in Japan from potato scab and belongs to a distinct species on the basis of phenotypic characteristics and DNA relatedness, exhibited lower levels of 16S rRNA sequence similarity with other potato scab pathogens, as well as other Streptomyces species. The phylogenetic tree constructed on the basis of 16S rRNA sequence data showed that the Streptomyces spp. that cause potato scab composed unique branches. The results of our phylogenetic analysis based on complete 16S rRNA sequences confirmed the lack of close relationships among Streptomyces spp. that cause potato scab. Our findings suggest that potato scab is caused by phylogenetically diverse Streptomyces species and that the pathogenicities of these organisms developed independently.

Base Sequence↗