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Biomedical subjects

F Takeuchi

Publications and source records attributed to F Takeuchi.

At least 73 records · Page 4Linked to original sources
PubMed1993

Protein-tyrosine kinase p72syk is activated by thrombin and is negatively regulated through Ca2+ mobilization in platelets.

Activation of platelets by thrombin results in a dramatic increase in tyrosine phosphorylation on multiple cellular proteins (Ferrell, J. E., and Martin, G. S. (1988) Mol. Cell. Biol. 8, 3603-3610; Golden, A., and Brugge, J. S. (1989) Proc. Natl. Acad. Sci. U. S. A. 86, 901-905; Nakamura, S., and Yamamura, H. (1989) J. Biol. Chem. 264, 7089-7091). However, none of the responsible protein-tyrosine kinase has been reported so far. We report here that p72syk, one of the non-receptor-type protein-tyrosine kinases, is activated following thrombin stimulation in blood platelets. Washed porcine platelets were stimulated by thrombin, and the activation of p72syk was assessed in an immunoprecipitation kinase assay. The activity of p72syk increased within 5 s, reached a maximum at 10 s, and decreased to a basal level within 60 s after 0.5 unit/ml thrombin stimulation. The amount of immunoprecipitated p72syk was not altered throughout the time course. This activation was greatly enhanced in a dose-dependent manner and was completely canceled by the pretreatment of platelet suspension with hirudin, a specific antagonist of thrombin. In the Ca(2+)-depleted condition both extra- and intracellularly, the activation of p72syk was still persistent; in contrast, the deactivation process was completely abrogated even at 120 s after thrombin stimulation. In addition, the replenishment of Ca2+ resulted in a similar deactivation pattern as seen in the Ca(2+)-rich condition. Furthermore, this deactivation was also canceled by the pretreatment of platelets with W7, a calmodulin antagonist, as well as ML9, a myosin-light-chain kinase inhibitor. These results indicate that p72syk can be a responsible enzyme to the protein-tyrosine phosphorylation events following the platelet activation by thrombin and may be negatively regulated by Ca2+ in a calmodulin-dependent manner, inter alia myosin light-chain kinase, in thrombin-stimulated platelets.

Animals↗
PubMed1993

Chromosome abnormalities in peripheral lymphocytes from patients with progressive systemic sclerosis.

Chromosomal abnormalities in cultured peripheral lymphocytes from 14 progressive systemic sclerosis (PSS) patients and 15 normal subjects were examined. No increase was observed in the frequency of chromosome aberrations in PSS patients who had not received any medical treatment. Those who had received medication showed an increased frequency of dicentrics (0.3%) although the frequency was not significantly higher than that for normal subjects. It is not clear, however, whether the increase was due to the hypersensitivity of PSS patients to agents used for therapeutic purposes.

Adult↗
PubMed1993

Identification of central sulcus by using somatosensory evoked magnetic fields and brain surface MR images: three dimensional projection analysis.

We present a novel non-invasive technique for identification of the central sulcus on the brain surface by using three-dimensional magnetic resonance imaging (3D-MRI) in combination with somatosensory evoked magnetic fields (SEFs). The central sulcus was supposed anatomically on the brain surface by using 3D-MRI. On the other hand, the primary somatosensory area is determined by using SEF data with median nerve stimulation. Superimposition of the SEFs of the 25 ms response onto the brain surface MR images clearly demonstrated the dipole source located in the gyral fold just behind the supposed central sulcus in all subjects analyzed. Three-dimensional reconstruction of the brain surface image data facilitated visualizing the precise anatomical localization of the magnetic field activities from any angle and measuring the distance from the source to any point of interest. The potential clinical application of this technique is discussed.

Adult↗
PubMed1993

Functional neurosurgical simulation with brain surface magnetic resonance images and magnetoencephalography.

We present a novel noninvasive technique for functional neurosurgical simulation combining three-dimensional magnetic resonance imaging of the brain surface with somatosensory evoked magnetic fields (SEFs) in a case of subcortical brain tumor. The preoperative analysis using this technique revealed that the central sulcus was located between the SEF source projected onto the brain surface and the tumor. At the time of surgery, the central sulcus was clearly identified by phase reversal of the cortical recordings of somatosensory evoked potentials. The actual cortical anatomy and the maximum somatosensory evoked potential location showed excellent agreement with the preoperative analysis of the brain surface magnetic resonance images and the SEF source. The subcortical tumor, which was barely identifiable without reliable functional cortical anatomy, was easily found in the motor area, just before the somatosensory evoked potential (and SEF) source. The potential clinical application of this technique is discussed.

Brain Mapping↗
PubMed1992

Thrombin-induced human platelet aggregation is inhibited by protein-tyrosine kinase inhibitors, ST638 and genistein.

We have investigated the involvement of protein-tyrosine kinases in thrombin-induced aggregation of human platelets, using ST638 and genistein which are known inhibitors of protein-tyrosine kinase. Preincubation of platelets with 50 microM of ST638 or 25 micrograms/ml of genistein completely blocked the platelet aggregation induced with 0.05 unit/ml of thrombin. The increase of protein-tyrosine phosphorylation bands (135-, 124-, 76-, 64-, and 60-kDa) induced with thrombin was also inhibited by these inhibitors in a dose-dependent manner. These inhibitors also blocked the platelet aggregation and protein-tyrosine phosphorylation induced with thrombin in aspirin-treated platelets. Increase of the intracellular Ca2+ concentration induced by thrombin was also inhibited by higher concentrations of genistein. These results suggest that the protein-tyrosine phosphorylation plays a certain role in platelet activation having some relation to the intracellular Ca2+ concentration.

Amino Acid Sequence↗
PubMed1992

Phosphorylation of histone H2A by protein kinase C and identification of the phosphorylation site.

In regenerating rat liver, nuclear protein histone H2A was shown to be phosphorylated on its amino-terminal serine residue [Sung et al. (1971) J. Biol. Chem. 246, 1358-1364], but the protein kinase which phosphorylates this residue has not been identified. To evaluate the possibility that protein kinase C can phosphorylate this residue, calf thymus histone H2A was 32P-labeled by incubation with [gamma-32P]ATP and highly purified protein kinase C from rat brain in the presence of calcium and phospholipid. About 1 mol of 32P was incorporated per mol of histone H2A and the Km and apparent Vmax of the reaction were calculated to be 2.1 microM and 0.35 mumol/min/mg, respectively. So histone H2A seemed to be a good substrate for protein kinase C. Further, the proteolytic phosphopeptides of 32P-labeled histone H2A were isolated by means of a series of column chromatographies and analyzed for their amino acid compositions. Comparison of the data with the known primary structure of histone H2A revealed their amino acid sequence as 1Ser-Gly-Arg. These data suggest that protein kinase C may be a candidate for the protein kinase which phosphorylates the amino-terminal serine residue of histone H2A during the regeneration of rat liver.

Amino Acid Sequence↗
PubMed1992

Inhibitory effect of mitoxantrone on activity of protein kinase C and growth of HL60 cells.

Mitoxantrone, a new anthraquinone, showed inhibitory an effect on protein kinase C (PKC) activity. Its IC50 value was 4.4 micrograms/ml (8.5 microM), which is much lower than those of the well-known anthracyclines daunorubicin and doxorubicin, the IC50 values of which are more than 100 micrograms/ml (> 170 microM). Kinetic studies demonstrated that mitoxantrone inhibited PKC in a competitive manner with respect to histone H1, and its Ki value was 6.3 microM (Ki values of daunorubicin and doxorubicin were 0.89 and 0.15 mM, respectively), and in a non-competitive manner with respect to phosphatidylserine and ATP. Inhibition of phosphorylation by mitoxantrone was observed with various substrates including S6 peptide, myelin basic protein and its peptide substrate derived from the amino-terminal region. Their IC50 values were 0.49 microgram/ml (0.95 microM), 1.8 micrograms/ml (3.5 microM), and 0.82 microgram/ml (1.6 microM), respectively. Mitoxantrone did not markedly inhibit the activity of cyclic AMP-dependent protein kinase, casein kinase I or casein kinase II, at concentrations of less than 10 micrograms/ml. On the other hand, brief exposure (5 min) of HL60 cells to mitoxantrone caused the inhibition of cell growth with an IC50 value of 52 ng/ml (0.1 microM). In HL60 cells, most of the PKC activity (about 90%) was detected in the cytosolic fraction. When HL60 cells exposed to 10 micrograms/ml mitoxantrone for 5 min were observed with fluorescence microscopy, the fluorescence elicited from mitoxantrone was detected in the extranuclear area. These results indicated that mitoxantrone is a potent inhibitor of PKC, and this inhibition may be one of the mechanisms of antitumor activity of mitoxantrone.

Animals↗
PubMed1992

[An epidemiological study on Bordetella pertussis infection in Fukui Prefecture from 1986 to 1991--especially observation on the patients of culture-confirmed pertussis].

In order to clarify the epidemiological situation of whooping cough in Fukui prefecture, 478 nasopharyngeal swabs from patients with pertussis-like symptoms were submitted to bacterial isolation. Laboratory data of these patients with clinical informations at the departments of pediatrics of 6 hospitals in Fukui city from June 1986 to May 1991 were also examined in relation to the above bacterial isolation. The results observed in culture positive patients were as follows: 1) B. pertussis were isolated from 83 patients (41 men and 42 women). 2) Isolates were classified into 3 serotypes. Most dominant type was 1.3.6 (80 strains, 96.4%), and followed by 1 (2 strains) and 1.4.5 (1 strain). 3) Most of the patients were non-vaccinees less than 3 years of age (69 of 83 (83.1%). This evidence suggested strongly that pertussis vaccine was highly effective to prevent pertussis. 4) The patients under 3 years of age whose leucocyte counts were > or = 15000/mm3 and lymphocyte rate to total leucocyte were > or = 70% in their peripheral blood at the time of nasopharyngeal swabs sampling were only 49.3% (33 of 67). Therefore, diagnosis of pertussis by leucocyte findings alone were considered to be inadequate. 5) The area of the patient's residence covered 7 regions of 8 health center districts in Fukui prefecture. The areal distribution of the number of patients from June 1986 to May 1991 was relatively proportional to the population of each district.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Lobenzarit disodium (CCA) inhibits the proliferation of human endothelial cells and the activity of DNA polymerase alpha.

N-(2)-Carboxyphenyl-4-chloroanthranilic acid disodium [Lobenzarit disodium (CCA)] is widely used for the treatment of patients with RA in Japan; however, the pharmacological mechanism of the compound is still unclear. In this report, the effect of CCA on the proliferation and DNA synthesis of endothelial cells was examined. CCA inhibited DNA synthesis in endothelial cells at a rather lower concentration than that in fibroblasts and HeLa cells. The DNA polymerase alpha activity was inhibited by CCA at a lower concentration than E. coli DNA polymerase I and avian myeloblastosis virus reverse transcriptase. Thus, CCA is a potent inhibitor of DNA polymerase alpha and this inhibitory effect could cause the inhibition of endothelial cell proliferation, which may be related to the therapeutic and pharmacological mechanisms of CCA.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1992

[Anatomical analysis of the sources of somatosensory evoked fields (SEFs) using 3D-MRI].

We have recorded short latency somatosensory evoked magnetic fields (SEFs) to left median nerve stimulation in three healthy subjects. The locations of the deduced dipole sources were projected onto the 3-Dimensional magnetic resonance imaging (3D-MRI) of the individual subjects providing an anatomical localization. We found that the deduced sources were located at the primary sensorimotor hand area on the posterior surface of the central sulcus, at an average depth of 26mm (11mm) from the scalp (brain surface). This technique that combined MEG with 3D-MRI was able to precisely determine source locations and analyze the relationships between dipole sources and brain structures. By using this technique, we can confirm functional anatomy of the brain noninvasively, and obtain much useful information preoperatively and during operation.

Adult↗
PubMed1992

Transient myopia with severe chemosis associated with exacerbation of disease activity in systemic lupus erythematosus.

A 46-year-old woman with systemic lupus erythematosus (SLE) developed bilateral transient myopia and periorbital edema with severe chemosis. Her myopia was ascribed to a refractive abnormality that was caused by curvature change and anterior displacement of the lenses and the ciliary bodies due to anterior ocular edema. The conditions were not associated with systemic edema or abnormality in the fundi and responded well to the systemic administration of corticosteroid. The course of the ocular symptoms paralleled changes of serum CH50 and anti-dsDNA antibody levels. Thus it was concluded that her ocular symptoms were closely related to activity of her SLE and may be considered a feature of SLE.

Antibodies, Antinuclear↗
PubMed1991

On kynureninase activity.

1) In Mg-deficient rats, kynureninase activity is decreased. 2) p-Hydroxyphenylpyruvate inhibits kynureninase activity. 3) -SH groups in the apoenzyme of kynureninase play a very important role in the enzymatic reaction. 4) 3-Hydroxykynurenine may be a very important regulative metabolite in the 3-hydroxykynurenine----xanthurenic acid pathway.

Animals↗
PubMed1991

Studies on protein kinase C tightly-bound to rat liver plasma membrane and its protease-activated form.

1. Rat liver plasma membrane contained two types of protein kinase C which could be extracted by Ca2(+)-chelator and detergent, respectively. The activities of these two enzymes were nearly equivalent. 2. The detergent-extracted protein kinase C, tightly-bound to membrane, was separated into two subtypes by hydroxyapatite column chromatography. Based on the elution profile and the Ca2+/phospholipid requirement, the major and the minor components were identified as type III and type II protein kinase C, respectively. 3. The detergent-extracted protein kinase C was converted to an active fragment with Mr 45,000 by limited proteolysis with trypsin. Incubation under physiological level of ionic strength increased the stability of this active enzyme and protected it from further inactivation by trypsin. 4. Phosphorylation of H1 histone by the protease-activated kinase was stimulated 1.5-2-fold by phosphatidylserine. However, this enzyme phosphorylated multiple proteins in rat liver subcellular fractions in Ca2(+)- and phospholipid-independent manner. 5. These results suggest that the protein kinase C (mainly type III enzyme) tightly-bound to rat liver plasma membrane may have important role through protein phosphorylation by the native or the protease-activated kinase.

Animals↗
PubMed1991

Glutathione levels and related enzyme activities in vitamin B-6-deficient rats fed a high methionine and low cystine diet.

We examined the change in glutathione metabolism in vitamin B-6-deficient rats. Vitamin B-6-deficient rats were fed a vitamin B-6-deficient diet containing 0.56% methionine and 0.075% cystine for 8 wk. Controls were fed an identical diet supplemented with 10 mg pyridoxine hydrochloride/kg diet. Glutathione concentrations in each organ examined were similar in control and vitamin B-6-deficient rats, and the values were comparably lower after intraperitoneal injection of diethylmaleate. However, buthionine sulfoximine caused a significantly greater decrease in glutathione levels in the liver and lungs of vitamin B-6-deficient rats relative to controls. Glutathione peroxidase activity in the liver of vitamin B-6-deficient rats was higher than in control animals; however, glutathione transferase activity in tissues other than liver of vitamin B-6-deficient rats was higher than in the controls. The activities of gamma-glutamyl-transferase in the liver and spleen of vitamin B-6-deficient rats were significantly lower than control values. The holoenzyme activities of cystathionine beta-synthase and cystathionine gamma-lyase in the liver of vitamin B-6-deficient rats were markedly reduced. These findings indicate that although the activities of enzymes that synthesize cysteine from methionine were decreased by vitamin B-6 deficiency, the level of synthesis and supply of cysteine in vitamin B-6-deficient rats were sufficient to maintain the same glutathione level as in controls, and that glutathione utilization in the liver was accelerated by vitamin B-6 deficiency.

Animals↗
PubMed1991

Chromosome aberration in lymphocytes from Behçet's disease.

Peripheral lymphocytes from 14 patients with Behçet's disease (BD) were examined for frequencies of chromosomal aberration. The frequency of gaps and breaks were not high in patients with BD but the frequency of dicentrics was increased in patients treated with colchicine or anticancer medicines. Patients treated with neither colchicine nor anticancer medicines showed no increased frequency of dicentrics. Our data suggested that the effect of treatment with colchicine or anticancer medication was one of the causes of the chromosome aberration observed in some BD lymphocytes. No numerical abnormality was observed in BD lymphocytes.

Adolescent↗
PubMed1990

Kinetic study of a galactosyltransferase in the B cells of patients with rheumatoid arthritis.

The sugar chains of IgG samples purified from sera of patients with rheumatoid arthritis (RA) contain many fewer galactose residues than those from sera of healthy individuals. Enzymatic studies revealed that the low galactose content in the IgGs of RA patients results from the reduced activity in the B cells of a galactosyltransferase (EC 2.4.1.90), which preferentially transfers galactose to asialo-agalacto-IgG. Asialo-agalacto-transferrin and asialo-ovine submaxillary mucin were also galactosylated by detergent-activated human B cell homogenates. However, no difference in the enzymatic activities toward these two acceptors was detected between the B cells from RA patients and from non-RA patients and healthy individuals. Enzyme kinetic studies revealed that an affinity of the galactosyltransferase in the B cells from RA patients was lowered for UDP-Gal but not for asialo-agalacto-IgG, while the affinities for UDP-Gal and asialo-agalacto-transferrin of the galactosyltransferase were not changed between the B cells from RA patients and from non-RA patients and healthy individuals in accordance with their enzyme activities. The results indicated that the reduced galactosyltransferase activity toward asialo-agalacto-IgG in the B cells from RA patients can be ascribed to the lowered affinity for UDP-Gal.

Arthritis, Rheumatoid↗