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T Nakai

Publications and source records attributed to T Nakai.

At least 19 recordsLinked to original sources
PubMed1997

Effect of a protein phosphatase inhibitor, okadaic acid, on thrombomodulin expression in cultured human umbilical vein endothelial cells.

We examined the effects of okadaic acid, a potent specific inhibitor of protein phosphatases 1 and 2A, on the expression of thrombomodulin (TM), a cell surface anti-thrombotic glycoprotein, on cultured human umbilical endothelial cells. Okadaic acid (2.5-10 nM) significantly increased TM antigen levels in parallel with its cofactor activity for thrombin-dependent protein C activation. Incubation of cells with 10 nM okadaic acid for 18 h induced an approximately 240% up-regulation of TM antigen levels that was accompanied by an increase in TM mRNA levels. Co-incubation of cells with okadaic acid and dibutyryl cyclic AMP further increased TM antigen levels. Furthermore, the effect of cAMP on TM expression was augmented by the pretreatment of cells with 10 nM okadaic acid for 18 h. These results provide evidence for the involvement of protein phosphatase in the cellular regulatory mechanisms for TM expression, which is distinct from that by cAMP.

Blotting, Northern↗
PubMed1997

The effect of Cu2+ on rat pulmonary arterial rings.

In the current study, Cu2+ was tested for its ability to relax vessels and to accumulate cyclic GMP (cGMP) in rat pulmonary artery employing rat extrapulmonary arterial rings. Cu(2+)-induced relaxation was endothelium and concentration (in the range from 10(-7) to 10(-4) M) dependent. The content of cGMP in the rings was increased 1.7-fold with 10(-4) M Cu2+. NG-Monomethyl-L-arginine abolished both the copper-induced relaxation and the increase in cGMP of rings. Cu2+ and zaprinast, which inhibits phosphodiesterase activity, caused a synergistic increase in cGMP level in the rings, suggesting that Cu2+ enhanced cGMP level through a mechanism different from that of zaprinast, probably as a consequence of elevated accumulation of nitric oxide (NO). The magnitude of vasorelaxation observed due to simultaneous addition of Cu2+ and acetylcholine was additive, not synergistic. Cu2+ did not augment relaxation induced by exogenously added NO donor. These results suggest that Cu2+ elevates NO level in the rings not by prolonging the half-life of NO, but by activation of endothelial nitric oxide synthase and subsequently potentiating the action of NO on vascular tone.

Acetylcholine↗
PubMed1996

Effect of glucose, insulin, and insulin-like growth factor-I on glucose transport activity in cultured rat vascular smooth muscle cells.

Glucose transport activity in cultured rat vascular smooth muscle cells (VSMCs) was examined under various concentrations of D-glucose, insulin, and insulin-like growth factor-I (IGF-I). Confluent cultures of VSMCs were incubated with serum-free medium containing 0-25 mmol/l of D-glucose for 24-49 h. The basal rate of 2-deoxyglucose uptake was reduced in association with increasing concentrations of D-glucose. Uptake of 2-deoxyglucose into the cells was linear between 0 and 15 min of incubation regardless of the glucose concentration. The uptake was inhibited by the addition of 10 mumol/l cytochalasin B or 100 mmol/l D-glucose indicating that the effects were mediated by specific integral glucose carriers. The effect of D-glucose was time-dependent and reversible. Insulin increased the uptake of 2-deoxyglucose in a dose-dependent manner, and its effect was dependent on the preincubation dose of D-glucose. Insulin-stimulated uptake was lower in the cells pre-exposed to 25 mmol/l D-glucose than in the cells pre-exposed to concentrations of D-glucose below 5.5 mmol/l. After a long-term incubation with insulin, the insulin-stimulated glucose transport was inhibited. Recovery of glucose transport activity was assessed by incubating cells with D-glucose for 24-48 h to induce desensitization. After a 24 h glucose conditioning, the uptake of 2-deoxyglucose was lower in the cells preincubated with 25 mmol/l glucose than in the cells preincubated with 5.5 mmol/l glucose. The effect of the glucose conditioning was reversible and dependent on the preincubation dose of D-glucose. IGF-I was a more potent stimulator of glucose transport than insulin. Wortmannin, an inhibitor of phosphatidylinositol 3-kinase (PI3-kinase), inhibited the uptake of glucose stimulated by insulin or IGF-I in a dose-dependent manner. Our results suggest that D-glucose regulates its own uptake independently of insulin and modulates the ability of insulin to induce insulin resistance in the cultured rat VSMCs. Glucose attenuated the effect of insulin, and led to a progressive decrease in the activity of the glucose transport effector system. Activation of wortmannin-sensitive PI3-kinase may be involved in the signaling pathways of the insulin- and IGF-I-stimulated glucose uptake in VSMCs. This mechanism of insulin resistance may be relevant to the formation of cellular defects in the vascular wall in patients with diabetes mellitus.

Androstadienes↗
PubMed1996

Very low density lipoprotein receptor binds apolipoprotein E2/2 as well as apolipoprotein E3/3.

The VLDL receptor, a newly identified lipoprotein receptor, recognizes apoE containing lipoproteins. The human VLDL receptor was overexpressed in 1d1A-7, a mutant Chinese hamster ovary cells lacking LDL receptors. Each VLDL obtained from a normolipidemic subject with two epsilon3 or epsilon2 alleles similarly competed for the binding of radiolabeled rabbit beta-VLDL to the VLDL receptors. The anti-apoE monoclonal antibody 1D7, which inhibited binding of apoE3 to the LDL receptors, failed to compete for the binding of VLDL (apoE3 or apoE2) to the VLDL receptors. Results indicate that the binding site of apoE on the VLDL receptor may differ from its binding site on the LDL receptor.

Animals↗
PubMed1996

Improved liver function following infusion of fructose-1, 6-bisphosphate in posthepatectomy patients.

The clinical effect of fructose-1,6-bisphosphate (FBP) administered to posthepatectomy patients was examined. FBP at 0.25 mmol/kg was administered continuously into the hepatic artery for 60 minutes on the 1st postoperative day in 11 cases. Hepatic arterial infusion of 0.25 mmol/kg glucose was performed in 7 cases. Furthermore, in 10 cases in which a catheter was not inserted in to the hepatic artery, 0.25 mmol/kg FBP was administered intravenously over a 60-minute period. Arterial ketone body ratio (AKBR) and serum levels of cyclic adenosine monophosphate, immunoreactive insulin, inorganic phosphorus, glucose, fructose, pyruvate, lactate and pyruvate kinase (PK) in the arterial blood were measured before and after administration. AKBR hardly changed after hepatic arterial infusion of glucose. It rose until 3 hours after intravenous or intrahepatic arterial administration of FBP. Especially, after hepatic arterial infusion of FBP, the AKBR was significantly higher up to 2 hours after administration than that before administration (P < 0.01). With hepatic arterial infusion of FBP, serum pyruvate transiently increased immediately after infusion (P < 0.01). PK activity was significantly elevated after administration of FBP (P < 0.05). Serum lactate levels decreased significantly after hepatic arterial infusion of FBP (P < 0.05). There was no difference in the recovery of protein synthetic ability and the postoperative changes in serum liver function test values among the three groups. Hepatic arterial infusion of FBP was suggested to promote adenosine triphosphate production by acceleration of the glycolytic pathway and lactate uptake in the hepatic cell.

Blood Glucose↗
PubMed1996

Usefulness of ultrasound-guided, fine-needle aspiration biopsy for palpable breast tumors.

OBJECTIVE: To investigate whether ultrasound (US) guidance improves the sensitivity of fine-needle aspiration biopsy (FNAB) in patients with palpable breast tumors. DESIGN: A retrospective study. SETTING: A university hospital. PATIENTS: A total of 107 patients with breast tumors (114 lesions) underwent US-guided FNAB and 138 patients (143 lesions) underwent FNAB guided by palpation (standard FNAB). MAIN OUTCOME MEASURES: The diagnoses obtained by FNAB were compared with the surgical findings and the diagnostic value of US-guided FNAB was evaluated. RESULTS: The sensitivity of US-guided FNAB was 89.3%, the specificity was 82.9%, and the accuracy was 86.9%. In contrast, the sensitivity of standard FNAB was 61.1%, the specificity was 73.3%, and the accuracy was 65.0%. For breast tumors 2.0 cm or less in diameter, the sensitivity and accuracy of US-guided FNAB were significantly higher than those of standard FNAB. CONCLUSION: Ultrasound-guided FNAB can improve the preoperative diagnosis of breast cancer, especially in patients with tumors that are 2 cm or less in diameter.

Biopsy, Needle↗
PubMed1996

Role of nitric oxide and superoxide anion in leukotoxin-, 9,10-epoxy-12-octadecenoate-induced mitochondrial dysfunction.

The present study was carried out to explore the involvement of nitric oxide (NO) and superoxide anion (O2.-) in Leukotoxin (Lx)-induced suppression of mitochondrial respiration. Glutamate- and succinate-dependent oxygen consumption and cytochrome c oxidase activity were assayed. Lx-induced mitochondrial damage was significantly attenuated by the pretreatment of lung with 4 x 10(-4) M NG-monomethyl-L-arginine (L-NMMA) or 500 units/ml superoxide dismutase (SOD) in ex vivo. However, L-NMMA plus SOD pretreatment showed no additive effect on the recovery of mitochondrial functions. The same assay was performed after the exposure of intact mitochondria to NO containing solution (1.25 x 10(-5) M) or 0.1 mM KO2/18-Crown-6 solution, which generated O2.-(6.4 x 10(-5) M). NO, but not O2.-, significantly inhibited the respiration of isolated mitochondria in vitro. Thus, there were great discrepancies in the involvement of NO and O2.- between ex vivo and in vitro system. Together with the previous reports, these facts suggested that the mechanisms by which NO and O2.- probably from vascular constituent cells inhibit mitochondrial respiration function of isolated perfused rat lung may not be simply due to their direct reactions with mitochondrial electron transport chain components, but may rely on the formation of peroxynitrite, and/or peroxynitrite-derived oxidants.

Animals↗
PubMed1996

Pituitary adenylate cyclase-activating polypeptide induces gene expression of the catecholamine synthesizing enzymes, tyrosine hydroxylase and dopamine beta hydroxylase, through 3',5'-cyclic adenosine monophosphate- and protein kinase C-dependent mechanisms in cultured porcine adrenal medullary chromaffin cells.

Pituitary adenylate cyclase-activating polypeptide (PACAP)i a potent stimulant of catecholamine secretion, increased catecholamine production in cultured porcine adrenal medullary chromaffin cells. PACAP induced dose-and time-dependent increases in mRNAs for the catecholamine synthesizing enzymes, tyrosine hydroxylase (TH) and dopamine beta-hydroxylase (DBH), with maximal 6- and 4-fold increases occurring at 8-16 h, respectively. The half-maximally and maximally effective PACAP concentrations for stimulation of TH and DBH gene expression were 0.5 and 3 nM, respectively. The TH protein level also showed an increase over the unstimulated basal level at 16-24 h in PACAP-stimulate cells. We previously demonstrated that PACAP activates both phospholipase C and adenylate cyclase in adrenal medullary cells. Addition of forskolin alone induced increases in mRNA expression of both TH and DBH. The phosphodiesterase inhibitor 3- isobutyl-1-methylxanthine potentiated the induction of TH and DBH mRNAs by PACAP. Addition of the protein kinase C activator phorbol 12-myristate 13-acetate (PMA) also caused increases in TH and DBH mRNA levels. In protein kinase C-downregulated cells pretreated with PMA for 24 h, the stimulatory effect of PACAP on TH and DBH gene expression was diminished. These results suggest that cAMP and protein kinase C mediate the PACAP-induced TH and DBH gene expression. Removal of extracellular Ca2+ with EGTA enhanced the PACAP-induced increases in both cellular cAMP and mRNA levels of TH and DBH, suggesting that Ca2+ has an inhibitory effect on the induction of TH and DBH mRNAs. In conclusion, the present study indicates that PACAP coordinately upregulates the gene expression of both TH and DBH by activating the cAMP and protein kinase C signaling pathways, leading to simulation of cate-cholamine synthesis, while Ca2+ negatively regulates TH and DBH gene expression in porcine adrenal medullary cells.

Adrenal Medulla↗
PubMed1996

1H-magnetic resonance spectroscopic observation of cultured malignant cells pharmacologically induced to different phenotypes.

RATIONALE AND OBJECTIVES: We evaluated the 1H nuclear magnetic resonance spectra of malignant cells after the administration of drugs that cause morphologic changes. METHODS: 1H spectra of a human lung adenocarcinoma cell line cultured with interferon gamma, dexamethasone, or sodium butyrate were obtained. The peaks were assigned by two-dimensional homonuclear Hartmann-Hahn spectroscopy spectra of the cells and their perchloric acid extracts. Differential spectra were used to evaluate relative changes in the peaks. RESULTS: In the control culture, choline/phosphocholine peaks were increased in the cell-growth phase, and the 1.26-ppm peak was increased in the confluent state. Treatment by interferon gamma and dexamethasone induced reproducible changes in the peaks of differential spectra corresponding to 1.26 ppm, choline/phosphocholine, and glutamate/glutamine. Dexamethasone treatment broadened lipid peaks. Changes after treatment with sodium butyrate were obscure. Microscopically, cells were induced to morphologically different phenotypes by each drug. CONCLUSION: Cells induced to exhibit morphologically different phenotypes present different 1H spectra.

Adenocarcinoma↗
PubMed1996

Effect of probucol, an oral hypocholesterolaemic agent, on acute tobacco smoke inhalation in rats.

1. We hypothesized that probucol, an oral hypocholesterolaemic agent, can suppress the oxidant stress induced by acute tobacco smoke inhalation in rats. We determined lung tissue glutathione (reduced and oxidized), lipid peroxide, tocopherol and plasma elastase inhibitory capacity, ferroxidase activity and lipid peroxide in rats after inhalation of tobacco smoke. 2. Rats treated with the probucol diet for 3 days or 4 weeks equally showed no suppression of plasma elastase inhibitory capacity and ferroxidase activity compared with control rats after acute tobacco smoke inhalation, although both animals treated with probucol for 3 days or 4 weeks had pharmacologically effective concentrations of probucol to lower plasma cholesterol but plasma cholesterol in rats treated with probucol for 3 days was still in the normal range. 3. Probucol treatment for 4 weeks lessened tobacco smoke-induced suppression of lung tissue glutathione, attenuated tobacco smoke-induced increases in lung tissue lipid peroxide and did not alter lung tissue tocopherol compared with control (lungs). 4. These findings demonstrate that probucol, via its antioxidant ability, confers a protective effect on lung exposed to acute tobacco smoke inhalation.

Animals↗
PubMed1996

Long-term alcohol intake enhances ADP-ribosylation of the multifunctional enzyme, phosphoglucomutase, in rat liver.

Adenosine diphosphate (ADP)-ribosylation is a posttranslational protein modification that, in turn, alters several regulatory proteins in mammalian cells. We demonstrated that long-term alcohol intake enhanced the ADP-ribosylation of a 58-kd protein in rat liver plasma membranes. To assess the biological significance of this phenomenon, we partially purified the 58-kd acceptor protein from solubilized rat liver homogenates by two sequential preparative high-pressure liquid chromatographies. Microsequencing revealed that it was phosphoglucomutase (PGM) (EC 5,4,2,2). This enzyme underwent negligible auto ADP-ribosylation, but the ADP-ribosylation was remarkably increased by adding rat liver plasma membranes. The extent of the increase was greater in alcohol-fed rats than in pair-fed controls, suggesting enhanced enzyme activities toward ADP-ribosylation of PGM after chronic alcohol consumption. Several important enzymes are ADP-ribosylated, after which their activities are modified. The results of this study showed that PGM is a novel substrate for ADP-ribosylation in the liver and that the ADP-ribosylation is increased after chronic alcohol consumption. In view of the variety of roles of PGM in the liver (carbohydrate metabolism and Ca2+ homeostasis), specific roles of this modification in terms of the effects of alcohol on hepatocytes may deserve further investigation.

Adenosine Diphosphate Ribose↗
PubMed1996

Effects of adenine nucleotide analogues on myocardial dysfunction during reperfusion after ischemia in dogs.

We examined effects of adenine nucleotide on ischemic myocardial stunning in dogs. Pentobarbitalanesthetized open-chest dogs were subjected to 20-min ligation of the left anterior descending coronary artery (LAD), followed by reperfusion for 30 min. Either saline, 5 mM 8-bromo-5'-AMP (tributyryl-AMP), or 30 mM N6, 2', 3'-tributyryl-5'-AMP (tributyryl-AMP), 5 mM 5-amino-4-imidazole carboxamide riboside (AICAr) as a positive reference, was infused at 0.1 ml/kg/min in the left femoral vein throughout the experiment. The myocardial contractile function was measured by ultrasonometry. The tissue levels of high-energy phosphates in the reperfused heart were determined. Myocardial contractile function assessed by % segment shortening (%SS) in the saline-infused group decreased during ischemia and returned toward the preischemic level during reperfusion but incompletely. A significant improvement in the %SS during reperfusion was observed in the 8-bromo-AMP- and AICAr-infused groups but not in the tributyryl-AMP-infused group. The magnitude of the protective effect of the drugs on myocardial contractility during reperfusion was 8-bromo-AMP > AICAr > tributyryl-AMP = saline. Only in the 8-bromo-AMP-infused group were the levels of ATP, ADP, and total adenine nucleotides in the reperfused heart significantly higher than those in the saline-infused group. The present result indicates that 8-bromo-AMP improves the ability of the heart to recover from ischemia and reperfusion associated with a significant restoration of ATP.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1996

Effects of BIBR-277, an angiotensin II type 1 receptor antagonist, on stunned myocardium in dogs.

BACKGROUND: Angiotensin converting enzyme inhibitors can protect the myocardium from ischaemic damage. We examined the effect of BIBR-277, an angiotensin II receptor type 1 antagonist, on myocardial stunning in dogs. METHODS: Pentobarbital-anaesthetized open-chest dogs were subjected to 20 min ligation of the left anterior descending coronary artery, followed by reperfusion for 60 min. Saline or 0.3, 1 or 3 mg/kg body weight BIBR-277 was injected intravenously 10 min before coronary ligation. The myocardial contractile function was measured by ultrasonometry. The tissue levels of energy metabolites in the 60 min reperfused heart were determined. RESULTS: Myocardial contractile function assessed in terms of percentage segment-shortening in the saline-treated group decreased during ischaemia and returned towards the pre-ischaemic level during reperfusion but incompletely (myocardial stunning). A significant and dose-dependent improvement in the percentage segment-shortening during reperfusion was observed in the BIBR-277-treated groups. The levels of ATP, ADP and AMP in the reperfused heart were not modified by BIBR-277 treatment compared with those in the saline-treated group. CONCLUSION: BIBR-277 ameliorates the myocardial contractile dysfunction during reperfusion after ischaemia, although it did not bring about any improvement in the high-energy phosphate levels in the reperfused heart.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1996

Effects of long-term alcohol intake on ADP ribosylation in rat liver plasma membranes.

Mono-ADP-ribosylation, In which the ADP-ribosyl moiety is transferred from NAD to an acceptor protein, is one of the important posttranslational modifications of cellular proteins. Because mounting evidence suggests significant biological roles of this reaction in transmembrane signal transduction and other cell metabolic reactions, we assessed how long-term alcohol intake alters toxin catalyzed- and endogenous mono-ADP-ribosylation in the liver of a rat model. We first found that thiol-preactivated cholera toxin-catalyzed ADP-ribosylation of the alpha-subunit of the stimulatory GTP-binding protein was enhanced after long-term alcohol intake. Unexpectedly, but interestingly, this enhancement was not accompanied by a concomitant increase of cholera toxin-catalyzed stimulation of the adenylate cyclase activity. We also found that long-term alcohol intake remarkably enhanced endogenous mono-ADP-ribosylation of a 58 kDa protein in plasma membranes. Thus, long-term alcohol intake stimulated endogenous, as well as, toxin-catalyzed mono-ADP-ribosylations. Characterization of the 58 kDa protein may uncover pathophysiological roles of this interesting phenomenon in alcohol-induced liver damage.

ADP Ribose Transferases↗
PubMed1996

Adenine nucleotides via activation of ATP-sensitive K+ channels modulate hypoxic response in rat pulmonary artery.

We examined the role of ATP-sensitive K+ channels in hypoxic pulmonary vasoconstriction, using isolated rat pulmonary arterial rings. Isolated rat pulmonary arterial rings displayed a rapid contraction followed by relaxation under hypoxic conditions. The ATP-sensitive K+ channel blocker glibenclamide (concentration > 1 microM) or a hyperglycemic buffer (15 mM glucose) attenuated the hypoxic relaxation in a dose-dependent manner but did not affect the hypoxia-induced contraction. To examine the relationship between hypoxia, energy, and redox state, intracellular levels of adenine nucleotides and pyridine coenzymes were determined by high-performance liquid chromatography in freeze-dried isolated rat pulmonary arteries at three time points (0, 4, and 10 min) before and during hypoxia. Hypoxia time dependently decreased the ATP content and the ATP-to-ADP ratio and increased the ADP and the AMP content in association with a rapid increase in the NADH and the NADH-to-NAD+ ratio. Hyperglycemic buffer (15 mM glucose) suppressed the hypoxia-induced changes of the adenine nucleotides (the decrease of the ATP content and the ATP-to-ADP ratio) but did not affect the hypoxia-induced changes of the NADH and the NADH-to-NAD+ ratio. Hypoxia did not affect the NADP+ or the NADPH content of pulmonary arteries. These findings indicate that an ATP-sensitive K+ channel regulates the tone of rat pulmonary arteries. Furthermore, an imbalance of the energy state may be involved in ATP-sensitive K+ channel activation during hypoxic vasorelaxation.

Adenine Nucleotides↗
PubMed1996

Protective effects of BQ-123, an ETA receptor antagonist, against leukotoxin-induced injury in rat lungs.

We tested the hypothesis that BQ-123, a novel endothelin type A (ETA) receptor antagonist, protects the lung against leukotoxin 9,10-epoxy-12-octadecenoate (Lx), which causes acute lung injury in animals. In isolated rat lungs perfused with Earle's balanced salt solution, BQ-123 suppressed the Lx-induced increase in wet lung weight, wet lung weight/dry lung weight, the effluent perfusate lactic dehydrogenase activity, and effluent perfusate and lung tissue ET-1 levels. BQ-123 also significantly attenuated the Lx-induced increase of the pulmonary capillary filtration coefficient. Thus our experimental results indicate that the ETA receptor antagonist, BQ-123, protects against Lx-induced experimental lung vascular injury.

Animals↗
PubMed1996

Pneumonitis during interferon and/or herbal drug therapy in patients with chronic active hepatitis.

We report four cases of acute pneumonitis due either to interferon, or a herbal drug, "Sho-saiko-to", or both in combination, in patients with chronic active hepatitis, focusing on its pathogenesis and response to prednisolone therapy. These cases shared common clinical features: fever, dry cough, dyspnoea, hypoxaemia, diffuse infiltrates both on chest radiography and chest computed tomography, restrictive pulmonary functional impairment, and alveolitis on examination of transbronchial lung biopsy, all of which suggest acute interstitial pneumonia. Furthermore, lymphocytosis was observed in association with the dominant CD8+ T-cell subset in bronchoalveolar lavage fluid. A lymphocyte stimulation test using peripheral blood was positive to interferon in one case and to Sho-saiko-to in another. All patients responded to oral prednisolone therapy. Peripheral soluble interleukin-2 receptor levels decreased in parallel with improvement in the clinical course. All patients were free of symptoms with a follow-up of 1-3 yrs. We conclude that interferon- and/or Sho-saiko-to-induced acute pneumonitis may be due to allergic-immunological mechanisms rather than toxicity, and that peripheral levels of soluble interleukin-2 receptor appear to be good markers of disease activity.

Adult↗