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Biomedical subjects

Y Takada

Publications and source records attributed to Y Takada.

At least 325 records · Page 18Linked to original sources
PubMed1994

Fluid shear stress increases the expression of thrombomodulin by cultured human endothelial cells.

Endothelial cells (ECs) cultured from human umbilical vein were exposed to medium flow in a flow-loading chamber, and changes in thrombomodulin (TM) expression were examined by flow cytometry and enzyme linked immunosorbent assay with monoclonal antibody. The expression of TM antigen was increased time- and shear stress-dependently by flow, and when exposed to a shear stress of 15 dynes/cm2 for 24 hr, it increased to approximately 200% of the stationary control level. Reverse transcriptase-polymerase chain reaction showed that TM mRNA levels in ECs also increased in response to flow. TM mRNA began to increase one hour after the application of shear stress of 15 dynes/cm2 and reached a maximum (approximately 330% of stationary control) after eight hours. These results, demonstrating an up-regulating effect of flow on TM expression in ECs, suggest that shear stress may be an important modulator of intravascular blood coagulation.

Antibodies, Monoclonal↗
PubMed1994

Two naturally occurring mutations in the kinase domain of insulin receptor accelerate degradation of the insulin receptor and impair the kinase activity.

We identified two novel heterozygous missense mutations of the insulin receptor gene: the Asp1179 mutation in one family and the Leu1193 mutation in two unrelated families with extreme insulin resistance. In these patients, the number of insulin receptors on the cell surface was found to be markedly decreased by insulin binding and surface labeling studies in transformed lymphocytes. Insulin binding to the transfected COS 7 cells and Rat-1 cells with both mutant cDNAs was also decreased to 5-31% of normal, and the mutant insulin receptors showed a markedly decreased kinase activity. Although biosynthetic labeling studies revealed that both mutant receptors were synthesized as 190-kDa proreceptors, the degradation of the mutant proreceptors was 2-fold faster than that of the wild type proreceptors. However, the degradation rate of the mutant receptors on the cell surface was comparable to that of wild type insulin receptor. These results suggest that the Asp1179 and Leu1193 mutations in the kinase domain are unique in causing decreased insulin receptor number on the cell surface by accelerated intracellular degradation, and that insulin resistance in these patients is mainly due to the decreased receptor number rather than impaired kinase activity.

Adult↗
PubMed1994

Nerve growth factor treatment induces high-potassium-evoked calcium-dependent acetylcholine release in cultured embryonic rat septal cells.

The effects of dibutyryl cAMP (dbcAMP) and nerve growth factor (NGF) on acetylcholine (ACh) release from primary cultured cells of embryonic rat septum were studied. Both dbcAMP and NGF increased the activity of choline acetyltransferase and contents of intracellular and spontaneously released ACh without affecting the total protein content. High-potassium-evoked ACh release was observed in NGF-treated cells but not in untreated and dbcAMP-treated cells. These results indicate that NGF induces cholinergic maturation from induction of the ACh-synthetic enzyme to the excitation-secretion processes.

Acetylcholine↗
PubMed1994

Characterization and expression of a P-450-like mycinamicin biosynthesis gene using a novel Micromonospora-Escherichia coli shuttle cosmid vector.

A 29 kb shuttle cosmid vector, pTYS507, was constructed from a cryptic Micromonospora griseorubida plasmid and the Escherichia coli cosmid pJB8. Subcloning of mycinamicin II biosynthesis genes in pTYS507 led to the identification of a DNA region that could complement a mutant of M. griseorubida that lacked both hydroxylase and epoxidase activities. Nucleotide sequence and mutational analysis suggested that a single P-450-like protein catalyzes both reactions.

Amino Acid Sequence↗
PubMed1994

N,N,N-trimethylsphingosine modifies aggregatory response and ATP release from platelets in whole blood.

We investigated the influence of N,N,N-trimethylsphingosine (TMS), a potent inhibitor of protein kinase C (PKC), on whole blood aggregation and ATP release from platelets. The preincubation with TMS at 1 microM for 2 min enhanced ATP release during arachidonic acid-induced aggregation. The ristocetin-induced agglutination was inhibited in a TMS concentration-dependent manner, which suggests that TMS may interact with the vWF receptor on platelets. TMS suppressed aggregatory response and ATP release from platelets after the addition of collagen. In contrast, the platelet aggregation induced by ADP and 12-O-tetradecanoylphorbol-13-acetate (TPA) was only slightly inhibited and the ATP release was not influenced after preincubation with TMS. Our results are in contrast to previous reported data, which were obtained using PRP and washed platelets.

Adenosine Diphosphate↗
PubMed1994

Heparin and heparan sulfate enhancement of the inhibitory activity of plasminogen activator inhibitor type 1 toward urokinase type plasminogen activator.

To study effects of glycosaminoglycan on the interaction between two chain urokinase type plasminogen activator (tcu-PA) (EC 3.4.21.31) and plasminogen activator inhibitor type 1 (PAI-1) the second order rate constant (k1) between high molecular weight tcu-PA and active recombinant prokaryotic PAI-1 (rpPAI-1) was determined employing a continuous method using chromogenic substrate S-2444 either in the presence or absence of various kinds of glycosaminoglycans. k1 was (5.9 +/- 1.6).10(6)/mol per s in the absence of effector molecule, and following addition of heparin (1.0 U/ml) k1 was enhanced to (3.22 +/- 0.73).10(7). A significant enhancement of k1 was also obtained by heparan sulfate (1.87 +/- 0.25).10(7). Dermatan sulfate or chondroitin sulfate did not show a significant effect on k1 although a slight decrease was obtained by mono-dextran sulfate (4.2 +/- 1.2).10(6). The intrinsic fluorescence of rpPAI-1 was shown to be slightly increased following addition of heparin (1.49 +/- 0.22%, n = 6), suggesting that heparin may enhance the inhibitory activity of PAI-1 toward tcu-PA both by a template mechanism and by a modification of PAI-1 structure.

Buffers↗
PubMed1994

Direct binding of collagen to the I domain of integrin alpha 2 beta 1 (VLA-2, CD49b/CD29) in a divalent cation-independent manner.

Integrin alpha 2 beta 1 is a major divalent cation-dependent receptor for collagen. Here, we show that the recombinant inserted/interactive domain (I domain) of alpha 2 specifically interacts with collagen, indicating the I domain contains all the components necessary for collagen binding. Evidence was obtained that divalent cations are not required for collagen binding to the I domain fragment, indicating that divalent cations are not involved in the actual binding to collagen but probably in the regulation of the binding. We identified Thr-221 within the previously identified putative ligand binding region as a residue critical for collagen binding to both alpha 2 beta 1 and the I domain fragment. Thr-221 may be involved in the actual collagen binding and recognition.

Animals↗
PubMed1994

Serotonergic measures in cyclosporine A treated rats.

Whole blood and plasma serotonin (5-HT), its major metabolite--5-hydroxyindoleacetic acid (5-HIAA), renal cortical blood flow, serum creatinine and whole blood cyclosporine A (CyA) levels were investigated in rats administered with CyA at a dose of 5 mg/kg b.w. or 10 mg/kg b.w. for 14 consecutive days. Serum creatinine remained unaltered during CyA treatment and no apparent changes in excised kidneys were found. Dose-dependent increases in whole blood and plasma 5-HT as well as whole blood 5-HIAA levels were observed. Renal cortical blood flow declined significantly and correlated inversely with whole blood 5-HT and 5-HIAA as well as with plasma 5-HT. Whole blood 5-HT was positively related to whole blood CyA levels. Taking all these data into account and considering the fact that 5-HT is a potent vasoconstrictor, a possible role of this amine in the pathogenesis of renal ischemia during CyA administration is suggested.

Animals↗
PubMed1994

Characterization of two new human apolipoprotein A-I variants: apolipoprotein A-I Tsushima (Trp-108-->Arg) and A-I Hita (Ala-95-->Asp).

Two unrelated subjects with new variants of apolipoprotein (apo) A-I were found during screening with isoelectric focusing (IEF) gel analysis. In the first case, apo A-I Tsushima, sequencing following amplification by the polymerase chain reaction (PCR) revealed a residue 108 missense mutation (TGG-->CGG, Trp-->Arg) in exon 4. The proband of apo A-I Tsushima was heterozygous for this mutation. The second case, apo A-I Hita, revealed a residue 95 missense mutation (GCC-->GAC, Ala-->Asp) in exon 4. The proband of apo A-I Hita was compound heterozygous with apo A-I (Ala-37-->Thr). These two subjects exhibited normal plasma concentrations of apo A-I and HDL cholesterol. In screening normal high school students (n = 198), we used a PCR-mediated site-directed mutagenesis to rapidly detect the substitution of G to A at codon 37 because the apo A-I (GC-->ACC, Ala-37-->Thr) mutation is unrelated to the charge difference on IEF. The frequency of the A allele was 0.04: the substitution G to A at codon 37 did not affect the plasma concentrations of lipids and lipoproteins.

Aged↗
PubMed1994

Fibrinolysis and serotonin under cyclosporine A treatment in renal transplant recipients.

Cyclosporine A (CyA), a potent immunosuppressive drug, has been used in renal transplant recipients with increasing frequency since 1982. Despite its efficacy, CyA therapy has been associated with an increased incidence of thromboembolic complications. This has been attributed to increased thromboxane production, reduced prostacyclin synthesis and increased platelet aggregability. The coagulation system is also altered in CyA-treated patients and some of these changes would favor thrombosis. Increased fibrinogen and FVII:C levels have also been associated with an enhanced risk of thrombosis. In contrast, CyA therapy was reported to increase the levels of antithrombin III and protein C, two proteins known to protect against venous thromboembolism. However, the possible effect of CyA on the fibrinolytic system has not been thoroughly investigated and rather confusing data have been reported concerning both enhancement and suppression of fibrinolysis. Serotonin (5-hydroxytryptamine, 5-HT) may play a role in hemostasis and platelet/vessel wall interactions. It may facilitate platelet thrombus formation by potentiating the aggregatory response to other agents such as ADP, collagen or epinephrine and by causing vasoconstriction. Taking all these data into consideration we have measured some fibrinolytic parameters, whole blood and plasma serotonin concentration in cyclosporine A- and non-cyclosporine A-treated kidney transplant recipients.

Creatinine↗
PubMed1994

Correlations between platelet aggregation, fibrinolysis, peripheral and central serotonergic measures in subhuman primates.

We have studied the relationships between whole blood and plasma serotonin (5-hydroxytryptamine, 5-HT), its major metabolite 5-hydroxyindoleacetic acid (5-HIAA) and serum lipids, platelet aggregation in the whole blood and in the platelet-rich plasma (PRP), and some fibrinolytic parameters in monkeys. Plasma 5-HT was found to be positively related to 5-HT- and ADP-induced platelet aggregation, tissue plasminogen activator (tPA) activity, serum cholesterol and LDL-cholesterol, whereas 5-HT in cerebrospinal fluid correlated inversely with serum cholesterol. Plasminogen activator inhibitor (PAI) activity was positively related to LDL. Euglobulin clot lysis time was related to both tPA and PAI activities. The significance of these findings and the possible role of 5-HT in atherogenesis and hemostasis are discussed.

Animals↗
PubMed1994

Leu 193 mutation in the cysteine rich region of the insulin receptor inhibits the cleavage of the insulin receptor precursor but not insulin binding.

To characterize the Leu 193 mutant insulin receptor, which was found in a patient with extreme insulin resistance, the mutant insulin receptor was overexpressed in Rat-1 fibroblasts by transfection of mutated insulin receptor cDNA. In the pulse-chase experiment, the cleavage of the proreceptors to the matured receptor subunits was impaired in the cells expressing Leu 193 insulin receptor and therefore, the mutant proreceptors were accumulated in the cell. Insulin bound to the Leu 193 insulin receptor on the cell surface with normal affinity, although the mutation was in the alpha-subunit of the insulin receptor. Therefore, the Leu 193 mutation impaired proreceptor cleavage but not insulin binding.

Animals↗
PubMed1994

Daily variations of platelet aggregation in relation to blood and plasma serotonin in diabetes.

The circadian rhythms of platelet aggregation in the whole blood and platelet rich plasma-PRP and plasma serotonin were studied in healthy volunteers (n = 10) and diabetic patients (type II diabetes mellitus n = 12). Platelet aggregation in the whole blood induced by collagen (2 micrograms/ml), ADP (10 microM), arachidonic acid (0.5 mM) and epinephrine (10 microM), and in PRP induced by collagen (2 micrograms/ml), ADP (5 microM), arachidonic acid (250 microM), epinephrine (10 microM) and serotonin-5-HT (1 microM) was measured at 7:30, 11:30, 17:00, 23:00, 4:00 and 7:00. In healthy subjects collagen- and ADP-induced platelet aggregation in the whole blood was significantly lower at 23:00 and 4:00 when compared to values at 7:30. In PRP normal and diabetic platelet response was the lowest during the night. Diabetic platelets exhibited an enhanced response to 5-HT starting from 17:00 until 4:00 when compared to 7:30. 5-HT-induced platelet aggregation was found to be significantly higher throughout the study in DM patients over controls in parallel to plasma 5-HT. In healthy volunteers plasma 5-HT was higher at 17:00 when compared to baseline values, whereas in DM patients plasma 5-HT was elevated starting from 17:00 until 4:00. An enhanced response of diabetic platelets to 5-HT together with elevated plasma 5-HT levels may contribute, at least partly, to the pathogenesis of diabetic vasculopathy and 5HT2 receptor blockers may be of value in DM patients.

Adenosine Diphosphate↗
PubMed1994

Electric-foot-shock induced the suppression of fibrinolytic activity in rats.

Electric-foot-shock was given to rats to initiate constant mental stress and its effect on fibrinolytic activity was analyzed. After the termination of electric-foot-shock which was given for an hour, euglobulin clot lysis time in the stressed group significantly prolonged than those in the control group. tissue plasminogen activator activity was also significantly lower in the stressed group. These effects lasted at least for an hour and returned to the control values 24 hours after the stress. Whole blood serotonin levels, which mainly show serotonin contents in platelets, were higher in the stressed group. A negative correlation between whole blood serotonin and tPA activity in the stressed group was obtained. These results suggest that prolonged mental stress impairs fibrinolysis by decreasing tPA activity with a concomitant increase of serotonin contents in platelets.

Animals↗