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Biomedical subjects

T Okada

Publications and source records attributed to T Okada.

At least 523 records · Page 29Linked to original sources
PubMed1995

Effects of a Dan Shen component, magnesium lithospermate B, in nephrectomized rats.

Magnesium lithospermate B, a compound newly isolated from Dan Shen, was given orally to rats for 70 days after excision of five-sixths of their kidney volume. As a result, mesangial proliferation, tubulo-interstitial lesions and glomerular sclerotic lesions, which were conspicuous in rats that were not given magnesium lithospermate B after nephrectomy, were inhibited. Furthermore, a decrease in blood urea nitrogen, improvement of hypoproteinemia, hypoalbuminemia and hypercholesteremia, and inhibition of urinary protein excretion were observed. The levels of creatinine, methylguanidine and guanidino-succinic acid, which accumulate in the blood with the progress of renal failure, were decreased significantly in rats given magnesium lithospermate B. These results indicate that magnesium lithospermate B, a component of an Oriental medicine has potential as a new therapeutic agent for inhibiting the progression of renal dysfunction.

Animals↗
PubMed1995

Regulation of ion transport by endothelins in rat colonic mucosa: effects of an ETA antagonist (FR139317) and an ETB agonist (IRL1620).

Rat colonic mucosa contains ETA and ETB receptors with Kd values for endothelin (ET)-1 of 32 and 11 pM and maximal binding capacities of 277 and 181 fmol/mg protein, respectively. In muscle-stripped rat colon without tonic nerve activity in Ussing chambers, the serosal addition of ET-1, ET-3 and IRL1620 inhibited amiloride-sensitive noncoupled Na+ entry and enhanced diphenylamine-2-carboxylate-sensitive Cl- secretion, producing a sustained decrease and a transient increase in the short-circuit current (Isc) and the transepithelial conductance, respectively. EC50 values of ET-1, ET-3 and IRL1620 and the maximal changes in Isc were 2.0, 10.2 and 10.9 nM and -12.7, -7.0 and -7.1 muA/cm2, respectively for the Na+ entry; these values were 50, 220 and 225 nM and +57.3, +47.3 and +21.3 muA/cm2, respectively, for the Cl- secretion. FR139317 (100 nM) inhibited ET-1-induced Na+ and Cl- movements, shifting the concentration-response curves to the right (EC50 = 25 nM and 1 microM, respectively), and inhibited ET-3 (> 100 nM)-induced Cl- movement, decreasing the maximal response to 35%, but it did not inhibit either ET-3-induced Na+ movement nor IRL1620-induced Na+ and Cl- movements. The removal of serosal Ca++ reduced 100 nM ET-1- and IRL1620-evoked changes in Isc by 50% and 70% for the Na+ entry and by 80% and 100% for the Cl- secretion, respectively. Indomethacin (1 microM) also reduced changes in Isc by 30% and 70% for the Cl- secretion but did not affect the Na+ entry. Our results show that ETA and ETB receptors regulate Na+ and Cl- transport by different mechanisms.

Animals↗
PubMed1995

[Therapeutic results of non-small cell lung cancer in stage III: combined synchronous irradiation with bronchial artery infusion of CDDP].

The present series consisted of 55 patients with non-small cell lung cancer in stage III who underwent radiotherapy from 1986-1989. They were divided into two groups: 35 patients with combined concurrent bronchial artery infusion (BAI) of CDDP (50 mg) and unevenly fractionated radiotherapy (combined group) and 20 with evenly fractionated irradiation (radiation group). The combined therapy was expected to achieve higher local control of disease. The rationale for the combined regime was based on the effects of CDDP, which causes cytostasis following intra-arterial infusion, and increased radiosensitivity from unevenly fractionated irradiation just after BAI. The radiotherapy group was considered a control in this study. The results of the combined group were limited to no CR, PR in 33 patients and NC in two with a period of 30 +/- 13 days for 50% reduction of tumor, superior to the radiation group. There was no difference between the two groups in the rate of local recurrence (combined group: 63%). The combined group showed 28 months of MST in cause-specific survival, a significant difference. Survival rates were 71% at one year, 27% at three years, and 15% at five years, including three survivors without recurrence. Stage III a patients in the combined group showed a better outcome than stage III b patients in the same group, and stage III a patients in the radiation group. Although radiation pneumonitis as a fatal side effect was noted in one patient of the combined group, the combined therapy presented here seemed to improve the prognosis of locally advanced lung cancer if properly indicated.

Aged↗
PubMed1994

Renal vasodilating and diuretic actions of a selective endothelin ETB receptor agonist, IRL1620.

The effects of a selective agonist for endothelin ETB receptors, Suc-[Glu9,Ala11,15]endothelin-1-(8-21), IRL1620, on renal hemodynamics and urine formation were studied in anesthetized dogs. Intrarenal arterial infusion of IRL1620 at a dose of 50 ng/kg/min increased renal blood flow from 3.37 +/- 0.30 (mean +/- S.E.) to a maximal value of 4.43 +/- 0.45 ml/g kidney weight per min (ml/g/min) at 9.1 +/- 1.0 min after the start of infusion, with no change in systemic blood pressure and heart rate. Urine flow rate increased and urine osmolality, osmolar clearance and free water reabsorption decreased significantly whereas glomerular filtration rate remained unchanged. In dogs given ibuprofen (12.5 mg/kg, i.v.) after the start of infusion of the peptide, renal blood flow increased slightly but significantly from 3.78 +/- 0.82 to 4.17 +/- 0.96 ml/g/min (1.0 +/- 0.1 min), followed by a gradual reduction in renal blood flow. In dogs given L-NG-nitroarginine (75 micrograms/kg/min), the renal blood flow decreased following intrarenal administration of IRL1620 (50 ng/kg/min). It is suggested that IRL1620 enhances the release of nitric oxide and prostaglandins in the kidney and promotes renal vasodilation. The IRL1620-induced reduction of urine osmolality and free water reabsorption was affected by neither ibuprofen nor L-NG-nitroarginine, thereby suggesting that the suppression of urine concentration did not seem to be linked to the enhanced production of nitric oxide or prostaglandins in the kidney.

Animals↗
PubMed1994

Mast cells cultured from the peripheral blood of normal donors and patients with mastocytosis originate from a CD34+/Fc epsilon RI- cell population.

Mast cells may be cultured from human peripheral blood in the presence of recombinant human stem cell factor (rhSCF). The characteristics of the cells in peripheral blood that give rise to mast cells are unknown. Because mast cell precursors in human marrow are CD34+, human peripheral blood mononuclear cells from patients with mastocytosis and normal controls were sorted on the basis of CD34 expression and the positive and negative cell populations were cultured in rhSCF, recombinant human interleukin-3 (rhIL-3), or both for 6 weeks. Cell cultures were examined every 2 weeks for total and mast cell number and cell differential using Wright Giemsa and acid toluidine blue stains and antibodies to mast cell tryptase and chymase, cell-associated histamine, and expression of CD34, c-kit, Fc epsilon RI, and Fc gamma RII using flow cytometric analysis. The ultrastructural anatomy of mast cells was examined by electron microscopy. Peripheral blood CD34+ cells cultured in rhSCF with or without rhIL-3 gave rise to cell cultures consisting of greater than 80% mast cells by 6 weeks. CD34+ cells cultured in rhIL-3 alone did not give rise to mast cells, whereas rhIL-3 plus rhSCF increased the final mast cell number eightfold when compared with cells cultured in rhSCF alone. Mast cells increased concomitantly with a decrease in large undifferentiated mononuclear cells. CD34- cells did not give rise to mast cells. Histamine content per cell at 6 weeks was approximately 5 pg. Electron microscopy of 4-week cultures showed immature mast cells containing predominantly tryptase-positive granules that were either homogeneous or contained lattice structures, partial scroll patterns, or central dense cores and mixtures of vesicles, fine granular material, and particles. The CD34+ population at day 0 expressed Kit (65%) and Fc gamma RII (95%), but not Fc epsilon RI, by fluorescence-activated cell sorter analysis. At 6 weeks, CD34+-derived mast cells exhibited Fc epsilon RI in addition to Kit and Fc gamma RII, and were negative for CD34 antigen. Patients with mastocytosis showed a higher number of mast cells per CD34+ cell cultured compared with normal controls. Thus, the mast cell precursor in human peripheral blood is CD34+/Fc epsilon RI- and gives rise to mast cells in the presence of rhSCF with or without rhIL-3, and the number of mast cells arising per CD34+ cell in culture is greater when the CD34+ cells are obtained from patients with mastocytosis compared with normal subjects.

Antigens, CD↗
PubMed1994

Involvement of phosphatidylinositol 3-kinase in Fc gamma receptor signaling.

Wortmannin, a potent and selective inhibitor of phosphatidylinositol (PI) 3-kinase (Okada, T., Sakuma, L., Fukui, Y., Hazeki, O., and Ui, M. (1994) J. Biol. Chem. 269, 3563-3567), prevented Fc receptor for IgG (Fc gamma R)-dependent phagocytosis of the human monocytic cell line U937 or guinea pig neutrophils. Cross-linking of Fc gamma R on the surface of U937 cells increased PI 3-kinase activity that was immunoprecipitated with antibody against phosphotyrosine or antibody against the 85-kDa regulatory subunit of PI 3-kinase. Specific cross-linking of Fc gamma R subclass Fc gamma RI or Fc gamma RII, using monoclonal antibodies against each receptor subclass and the F(ab')2 fragment of goat antibody against mouse IgG, increased anti-phosphotyrosine-precipitable PI 3-kinase activity. Treatment of cells with anti-Fc gamma RIII antibody plus the same F(ab')2 did not affect the activity, reflecting the lack of Fc gamma RIII in U937 cells. Fcy gamma R stimulation triggered prominent tyrosine phosphorylation of several proteins, among which the 115-kDa peptide showed strong association with PI 3-kinase. Thus, Fc gamma R appears to be coupled functionally, via a tyrosine kinase, to PI 3-kinase, which may regulate the phagocytotic activity of the cells.

Androstadienes↗
PubMed1994

Quantitative analysis of mutually competitive binding of human Raf-1 and yeast adenylyl cyclase to Ras proteins.

Ras proteins appear to have two distinct downstream effectors, adenylyl cyclase in Saccharomyces cerevisiae and a product of raf-1 protooncogene in higher organisms. We found that in vitro activation of adenylyl cyclase by yeast Ras2 and human H-Ras proteins is subject to competitive inhibition by its leucine-rich repeats domain and by the N-terminal regulatory domain of human Raf-1 protein. Kinetic analyses of the inhibition patterns enabled us to determine exact dissociation constants (Kd) of the two polypeptides for Ras2 and H-Ras. The leucine-rich repeats domain bound to the posttranslationally modified Ras2 with the Kd of approximately 13 nM, which was close to the value (7 nM) of the whole adenylyl cyclase. The Kd of Raf-1 for the modified H-Ras, 3.5 nM, was significantly lower than that for Ras2, 24 nM, whereas adenylyl cyclase bound preferentially to Ras2. Similar inhibition was also observed in vivo by suppression of RAS2Val-19-dependent heat shock sensitivity and of Ras-dependent cAMP response to glucose upon overexpression of Raf-1 in yeast. These results indicate that the leucine-rich repeats domain contains the Ras protein-binding site and that Raf-1 and adenylyl cyclase, sharing no structural homology with each other, bind to a similar, if not identical, region of Ras with comparable affinities.

Adenylyl Cyclase Inhibitors↗
PubMed1994

Novel theta class glutathione S-transferases Yrs-Yrs' and Yrs'-Yrs' in rat liver cytosol: their potent activity toward 5-sulfoxymethylchrysene, a reactive metabolite of the carcinogen 5-hydroxymethylchrysene.

Two novel theta class glutathione S-transferases (GSTs), designated Yrs-Yrs' and Yrs'-Yrs', were isolated from rat liver cytosol and purified to homogeneity. Polyclonal antibody raised against the previously reported theta class GST Yrs-Yrs (Hiratsuka, A. et al., J. Biol. Chem. 265, 11973 (1990)) cross-reacted with GSTs Yrs-Yrs' and Yrs'-Yrs'. These three theta class GSTs had different pI values and were separated by chromatofocusing. The enzyme subunit Yrs' was separated from Yrs by reverse partition HPLC, but identical to Yrs in the first 37 N-terminal amino acid sequence. Like GST Yrs-Yrs, both GSTs Yrs-Yrs' and Yrs'-Yrs' were not retained on an S-hexyl-GSH affinity column and had little activity toward 1-chloro-2,4-dinitrobenzene. However, they showed potent activities toward the reactive sulfate ester of the carcinogen, 5-hydroxymethylchrysene. GSTs Yrs-Yrs and Yrs'-Yrs' showed much higher GSH peroxidase activities toward arachidonate hydroperoxide than did rat liver alpha class GST Ya-Ya.

Amino Acid Sequence↗
PubMed1994

Novel potassium-channel openers: preparation and pharmacological evaluation of racemic and optically active N-(6-amino-3-pyridyl)-N'-bicycloalkyl-N"-cyanoguanidine derivatives.

The previous paper reported on the synthesis and pharmacological evaluation of N-(6-amino-3-pyridyl)-N'-bicycloalkyl-N"-cyanoguanidine derivatives, from among which three compounds were selected as potent potassium-channel openers. In the present study, selected compounds were tested for antagonism of potassium-induced contraction of rat aorta, hypotensive activity in normotensive rats, and diuretic activity in spontaneously hypertensive rats. This led to further evaluation of compound (+/-)-10 and selection of (+)-N-(6-amino-3-pyridyl)-N'- [(1S,2R,4R)-bicyclo- [2.2.1]hept-2-yl]-N"-cyanoguanidine ((+)-10) (AL0670) for development as an antihypertensive agent. Although AL0670 is regarded as a pinacidil-type K(+)-channel opener, it showed different pharmacological and conformational profiles from pinacidil.

Animals↗
PubMed1994

Sequence analysis of the flgA gene and its adjacent region in Salmonella typhimurium, and identification of another flagellar gene, flgN.

The flagellar genes flgA and flgM are located at the terminus of the region-I flagellar gene cluster on the chromosome of Salmonella typhimurium. The flgA gene is involved in P-ring formation of the flagellar basal body, whereas flgM encodes the anti-sigma factor which acts as a negative regulator of the flagellar regulon. The nucleotide sequence of the DNA fragment containing these flagellar genes and the adjacent region was determined. The flgA gene was found to encode a 219-amino-acid (aa) protein of 23,556 Da. The N-terminal region of FlgA has the characteristics of a typical signal sequence, suggesting that FlgA may function in the periplasmic space where P-ring assembly takes place. The flgM gene was found to constitute an operon together with an ORF which encodes a 140-aa protein of 15,899 Da. A gene disruption mutant was constructed by inserting a cat gene cartridge into the ORF on the chromosome. This mutant showed only weak motility, indicating that the product of the ORF is involved in flagellar formation. Therefore, this ORF was designated as flgN. Electron microscopic observation revealed that most of the flagellar structures produced by the flgN mutant are hook-basal body complexes lacking the filament portions. Based on these results, we concluded that the flgN product is required for the efficient initiation of filament assembly.

Amino Acid Sequence↗
PubMed1994

Circular dichroism of metaiodopsin II and its binding to transducin: a comparative study between meta II intermediates of iodopsin and rhodopsin.

Through low-temperature absorption and circular dichroism (CD) spectroscopies, and G-protein (transducin) binding experiments, we have investigated molecular properties of the meta II intermediate of iodopsin, a cone visual pigment present in chicken red-sensitive cones. The meta II intermediate of iodopsin (metaiodopsin II, lambda max = 390 nm) displayed a positive CD band at about 390 nm and a large negative CD band below 300 nm. It dissociated into all-trans-retinal and the protein moiety. A long-lived intermediate corresponding to the meta III intermediate of rhodopsin was not observed in iodopsin, under our experimental conditions. Decay of metaiodopsin II was significantly suppressed in the presence of transducin, but not in the presence of both transducin and GTP, indicating that metaiodopsin II can interact with transducin and activate it. Both metaiodopsin II and metarhodopsin II displayed a large negative CD band below 300 nm. This fact suggested that during the formation of both meta II intermediates, some aromatic amino acid residues and/or a disulfide bond are rearranged, which may be important for expression of catalytic activity for exchange of GDP to GTP on transducin. On the other hand, metaiodopsin II decayed more than 10 times faster than metarhodopsin II. This fact may be one of the reasons why cones are less photosensitive than rods.

Animals↗
PubMed1994

Subtypes of endothelin ETA and ETB receptors mediating venous smooth muscle contraction.

In rabbit saphenous vein, endothelin (ET)-1 and ET-3 induced sustained contractions whereas the selective agonists of the ETB receptor, sarafotoxin S6c (STXc) and IRL 1620, induced transient contractions. In the presence of an ETA antagonist, BQ-123, contractions induced by ET-1, STXc and IRL 1620 did not change whereas ET-3 induced only transient contraction. The ETB antagonists, RES-701-1 and IRL 1038, only weakly antagonized the effects of these stimulants. In the muscle pretreated with STXc, neither STXc nor IRL 1620 was effective whereas ET-3 induced sustained contraction at higher concentrations than ET-1. In the muscle pretreated with STXc, BQ-123 weakly antagonized the effect of ET-1 and abolished the effect of ET-3. These results suggest that there are two types of ET receptors; less tachyphylactic and isopeptide-selective ETA receptor, and tachyphylactic and isopeptide-nonselective ETB receptor. The ETA receptors may be further classified as a BQ-123-sensitive ETA1 and a BQ-123-insensitive ETA2 subtypes. The ETB receptors may also be subclassified as the ETB1 and ETB2 subtypes based on the sensitivity to the ETB antagonists.

Animals↗
PubMed1994

Spectroscopic observation of the intramolecular electron transfer in the photoactivation processes of nitrile hydratase.

The photoactivation phenomena of the photosensitive enzyme nitrile hydratase (NHase) was studied by various spectroscopic methods. We have already shown that the photoactivation of NHase accompanies oxidation of an iron atom in the NHase [Honda et al. (1992) FEBS Lett. 301, 177-180]. From the results obtained in the present study by absorption, action, and fluorescence spectra, we show that the chromophore responsible for the photoactivation process is the iron complex, and the tryptophan residues in NHase induce the oxidation of the iron atom via an energy-transfer process. The nanosecond flash photolysis experiment revealed that this photoactivation process is completed within 50 ns, which suggests that the changes observable in the absorption spectra originate from an intramolecular electron transfer occurring from an electronically excited state. Also the role of a stabilizing reagent, namely, n-butyric acid (BA), was investigated using the above methods, which revealed that BA, besides its stabilizing effect, contributes to the increase in apparent photoactivation rate.

Butyrates↗
PubMed1994

Blockage of chemotactic peptide-induced stimulation of neutrophils by wortmannin as a result of selective inhibition of phosphatidylinositol 3-kinase.

Wortmannin, a fungal metabolite, inhibited 32P labeling of phosphatidylinositol trisphosphate, a product of phosphatidylinositol 3-kinase (PI 3-kinase), selectively in formyl peptide-stimulated 32P-loaded guinea pig neutrophils. The inhibition was of the same concentration dependence (with the half-maximal inhibition around 50 nM) as was observed for the simultaneous inhibition of formyl peptide-induced superoxide anion production. Wortmannin inhibited all three of the PI 3-kinase activities found in the cytosol fraction of guinea pig neutrophils, with a similar dose dependence (the half-maximal effects at 5 nM). Wortmannin was also effective on an immunologically purified preparation of the enzyme. The inhibition was of a noncompetitive type with regard to ATP and was observed consistently when PI, PI monophosphate, or PI bisphosphate was used as substrate. PI 4-kinase activity was not affected. It is concluded, therefore, that wortmannin abolished the formyl peptide-induced stimulation of neutrophils as a result of the inhibition of PI 3-kinase. An essential role of PI 3-kinase in receptor-mediated signaling in neutrophils thus evidenced with the use of wortmannin will be expanded to other cellular signaling systems.

Androstadienes↗
PubMed1994

Essential role of phosphatidylinositol 3-kinase in insulin-induced glucose transport and antilipolysis in rat adipocytes. Studies with a selective inhibitor wortmannin.

Significant activity of phosphatidylinositol 3-kinase (PI 3-kinase) was detected in the membrane fractions, or in the immunoprecipitates prepared with anti-phosphotyrosine antibodies, from rat adipocytes that had been incubated with insulin for 20 min. The PI 3-kinase activity in these preparations as well as in the whole cell lysates of adipocytes not treated with insulin was inhibited by the addition of wortmannin, a fungal metabolite, to the enzyme assay mixture. The inhibition was dependent on the inhibitor concentration with IC50 being less than 10 nM and perfect inhibition at 100 nM. The effect of insulin to induce membrane PI 3-kinase activity was mostly abolished, but its effects to tyrosine-phosphorylate the beta-subunit of the insulin receptor or other cellular substrate proteins including insulin-receptor-substrate-1 were not at all antagonized, by wortmannin added to the cell incubation medium. Insulin stimulation of cellular 2-deoxyglucose uptake and inhibition of isoproterenol-induced lipolysis observable in adipocytes under the same conditions were also antagonized by wortmannin added in the same concentration range as used for the inhibition of insulin-susceptible PI 3-kinase. It is concluded, therefore, that activation of wortmannin-sensitive PI 3-kinase plays a pivotal role in the intracellular signaling pathways arising from the insulin receptor autophosphorylation and leading to certain metabolic responses.

Adipocytes↗
PubMed1994

Novel potassium channel openers: synthesis and pharmacological evaluation of new N-(substituted-3-pyridyl)-N'-alkylthioureas and related compounds.

This report describes the synthesis and pharmacological evaluation of a series of novel potassium channel openers related to the pinacidil-type compounds. Thioureas, cyanoguanidines, and pyridine N-oxides were systematically evaluated for their effects on both the inhibition of spontaneous mechanical activity in rat portal vein (in vitro) and their antihypertensive activity (in vivo), and the structure-activity relationship for this series of compounds was discussed. Good correlation between in vitro and iv antihypertensive activity was observed for these compounds. Among them, cyanoguanidines bearing a conformationally rigid unit such as a norbornyl group generally possessed potent activity in both in vitro and in vivo studies. Especially, N-(6-amino-3-pyridyl)-N'-cyano-N"-(1-methyl-2-norbornyl)guanidine (23d) was identified as a more potent potassium channel opener in vitro (EC100 = 3 x 10(-8) M) than pinacidil (EC100 = 10(-7) M).

4-Aminopyridine↗