Biomedical subjects

Y Takata

Publications and source records attributed to Y Takata.

At least 109 records · Page 6Linked to original sources

PubMed1996

Effect of glimepiride (HOE 490) on insulin receptors of skeletal muscles from genetically diabetic KK-Ay mouse.

A new sulfonylurea, glimepiride (HOE 490), has been developed for the glycemic control in non-insulin-dependent diabetes mellitus. We examined the effect of glimepiride on glucose and insulin levels in KK-Ay mice, an animal model of non-insulin-dependent diabetes mellitus, which is characterized by hyperglycemia and hyperinsulinemia. Administration of glimepiride (0.5 mg/kg/day) for 8 weeks to KK-Ay mice resulted in decrease in glucose (297 +/- 36 to 250 +/- 51 mg/dl) and insulin (76 +/- 14 to 41 +/- 14 microU/ml) levels. To clarify the mechanism of the agent, we examined the effect of this new drug on insulin receptors in the skeletal muscles. There was no difference in insulin binding to the receptors from both glimepiride-treated and -untreated KK-Ay mice muscles. The insulin-stimulated autophosphorylation of insulin receptors from KK-Ay mice was decreased compared to that from normal mice (5 +/- 1 vs. 39 +/- 13% over basal). Glimepiride did not ameliorate impaired insulin-stimulated insulin receptor autophosphorylation. To determine the effect of glimepiride on post-insulin receptor signaling pathway, we measured 2-[3H]glycerol incorporation into diacylglycerol in the cultured rat fibroblast cell line overexpressing human insulin receptors. Glimepiride (100 microM) as well as insulin (10 nM) significantly stimulated diacylglycerol production. These results suggest that glimepiride has a potent extrapancreatic effect on glucose metabolism and may directly stimulate glucose transport activity through phospholipid signaling pathway, but not through insulin receptor kinase signaling pathway.

Animals↗

PubMed1996

Probing the S-adenosylmethionine-binding site of rat guanidinoacetate methyltransferase. Effect of site-directed mutagenesis of residues that are conserved across mammalian non-nucleic acid methyltransferases.

Most mammalian non-nucleic acid methyltransferases share three sequence motifs. To gain insight into the S-adenosyl-methionine (AdoMet)-binding site of guanidinoacetate methyltransferase, we mutated several conserved residues that are found in or near motifs I and II. Conversion of either of two glycine residues of motif I (Gly67 and Gly69) to an alanine resulted in an inactive enzyme. These enzymes, although having UV absorption, fluorescence and far-UV CD spectra virtually identical with those of the wild-type enzyme, seem to be conformationally different from the wild-type enzyme as judged by near-UV CD spectra and the extent of urea denaturation, and are apparently not capable of binding AdoMet. Mutation of Tyr136 of motif II to a valine resulted in a decrease in Kcat/Km values for substrates. Changing this residue to a phenylalanine caused only a minor change in Kcat/Km for AdoMet. This suggests that the aromatic side chain stabilizes the binding of AdoMet. Mutagenic changes of Glu89, which is the residue corresponding to the conserved acidic residue on the C-terminal side of motif I, indicated its contribution to AdoMet binding. These results are consistent with the idea that both motifs I and II are crucial in forming the AdoMet binding site of guanidinoacetate methyltransferase.

Amino Acid Sequence↗

PubMed1996

Pioglitazone attenuates the inhibitory effect of phorbol ester on epidermal growth factor receptor autophosphorylation and tyrosine kinase activity.

A new anti-diabetic drug, pioglitazone, was tested as to whether it could ameliorate the decreased kinase activity of epidermal growth factor (EGF) receptor induced by phorbol ester (PMA) in A431 cells. The treatment of A431 cells with PMA decreased the tyrosine kinase activity of EGF receptors to 37% of normal in autophosphorylation and to 24% in tyrosine kinase activity toward Glu/Tyre synthetic polymers. Co-incubation of the cells with pioglitazone and PMA improved the receptor tyrosine kinase activity to 81% of control. Pioglitazone treatment alone did not change the kinase activity of EGF receptors. Pioglitazone did not decrease the PMA-activated protein kinase C activity and did not affect the protein tyrosine phosphatases activity in A431 cells. These results suggest that pioglitazone may act as a specific antagonist to the inhibitory effect by protein kinase C on the EGF receptor tyrosine kinase.

Carcinoma, Squamous Cell↗

PubMed1996

Hsp70 family molecular chaperones and mutant insulin receptor: differential binding specificities of BiP and Hsp70/Hsc70 determines accumulation or degradation of insulin receptor.

We have examined the binding specificities of Hsp70 family molecular chaperones, BiP and Hsp70/Hsc70, to wild-type or mutant insulin receptors. BiP bound to proreceptor of wild-type insulin receptor, but not to mature receptor. A mutant insulin receptor, which lacked 47 amino acid residues (delta Ex13 IR) corresponding to exon 13 of insulin receptor gene, accumulated in the endoplasmic reticulum as uncleaved proreceptor with immature oligosaccharide chains. This deletion mutant bound to BiP more tightly than wild type. Introduction of two types of mutations, Asp1179 or Leu1193, into delta Ex13 IR led to accelerated degradation, and these double mutants bound weakly to BiP. In contrast, Ser735 insulin receptor was normally transported to the plasma membrane and normally bound to BiP. Furthermore, Asp1179, Leu1193 insulin receptors and delta Ex13 IR combination mutant with either Asp1179 or Leu1193 bound more tightly to Hsp70/Hsc70 compared with wild-type, Ser735, and delta Ex13 IR. These results suggest that the binding specificity of mutant insulin receptors to two molecular chaperones, i.e., BiP and Hsp70/Hsc70, plays an important role for their posttranslational processing that may lead to the accumulation in the endoplasmic reticulum or the degradation of insulin receptors.

Animals↗

PubMed1996

Acinic cell Carcinoma of the parotid gland: CT and MRI.

We report CT and MRI bindings in two cases of acinic cell carcinoma of the parotid glands which behaved differently on T2-weighted images. Differences in signal intensities were considered to reflect the histology of the lesion, although a histological diagnosis could not be made on imaging grounds alone.

Adult↗

PubMed1996

The beneficial effects of atrial natriuretic peptide on arrhythmias and myocardial high-energy phosphates after reperfusion.

OBJECTIVES: The aim of this investigation was to test whether the administration of atrial natriuretic peptide (ANP) has cardioprotective effects against ischaemic and reperfusion injury. METHODS: Thoracotomized dogs underwent a 30 min left circumflex coronary artery occlusion and 60 min of reperfusion (control group; n = 16). The ANP group (n = 9) received a 20 micrograms bolus injection of synthetic alpha human ANP (SUN 4936) followed by infusion at a dose of 0.1 microgram/kg/min from the beginning of coronary occlusion to the end of the procedure. RESULTS: Administration of exogenous ANP increased plasma ANP immediately and maintained levels at 3000 pg/ml, resulting in an 8-fold increase in plasma cyclic guanosine monophosphate (cGMP) levels. Plasma ANP and plasma cGMP levels did not change at all in controls. There were no significant differences in haemodynamic parameters during ischaemia and reperfusion between the groups. In the ANP group, the prevalence and frequency of ventricular extrasystoles within 10 min after reperfusion decreased markedly [ANP 22% vs. control 100%, P < 0.01, and ANP 1 (1) vs. control 92 (50), P < 0.05, respectively]. No dog in the ANP group had ventricular fibrillation (VF), but the incidence of VF was not statistically significant between the groups [ANP 0% vs. control 25%]. ATP content in the inner layers of the ischaemic myocardium in the ANP group was higher than in controls (P < 0.05) [1.92 (0.28) vs. 1.18 (0.13) mumol/g wet weight]. There was no significant difference in the content of myocardial tissue angiotensin II between the groups. CONCLUSIONS: These data show that the infusion of ANP has cardioprotective effects on myocardial ischaemia and reperfusion in this model. These beneficial effects are probably due to direct effects through cGMP rather than haemodynamic changes.

Angiotensin II↗

PubMed1996

Adrenoceptors in SHR: alterations in binding characteristics and intracellular signal transduction pathways.

There is much data on altered adrenoceptor function in the heart, blood vessel and kidney from spontaneously hypertensive rats (SHR). The enhancement of vascular and renal alpha-adrenoceptor function, i.e. vasoconstriction and retention of water and sodium, may contribute to the development and maintenance of the hypertension, whereas cardiac alpha1-adrenoceptor may be of minor physiological significance. Alpha1-adrenoceptor-mediated signal transduction as a whole is increased in SHR vascular tissues, but the intracellular signaling per receptor in the kidney seems to be decreased despite increased alpha1-adrenoceptor density. On the other hand, cardiac and vascular beta-adrenoceptor responsiveness is attenuated in SHR. Reduced vasorelaxation mediated by beta-adrenoceptors may also contribute to high blood pressure. The impaired cardiovascular beta-adrenoceptor function in SHR does not appear to be necessarily explained by alterations observed at receptor levels. Alterations in signal transduction should be also considered. Limited data on renal beta-adrenoceptor density and its signaling suggest decreased or unaltered cyclic AMP formation per receptor in SHR. We will review alterations in both binding characteristics and each component of intracellular signal transduction pathways in cardiovascular and renal adrenoceptors of SHR.

Animals↗

PubMed1996

The dominant negative effect of a kinase-defective insulin receptor on insulin-like growth factor-I-stimulated signaling in Rat-1 fibroblasts.

To study the interaction between insulin receptor (IR) and insulin-like growth factor-I (IGF-I) receptor (IGF-IR) tyrosine kinases, we examined IGF-I action in Rat-1 cells expressing a naturally occurring tyrosine kinase-deficient mutant IR (Asp 1048 IR). IGF-I normally stimulated receptor autophosphorylation, IRS-I phosphorylation, and glycogen synthesis in cells expressing Asp 1048 IR. However, the Asp 1048 IR inhibited IGF-I-stimulated thymidine uptake by 45% to 52% and amino acid uptake (aminoisobutyric acid [AIB]) by 58% in Asp 1048 IR cells. Furthermore, IGF-I-stimulated tyrosine kinase activity toward synthetic polymers, Shc phosphorylation, and mitogen-activated protein (MAP) kinase activity was inhibited. The inhibition of mitogenesis and AIB uptake was restored with the amelioration of the impaired tyrosine kinase activity and Shc phosphorylation by the introduction of abundant wild-type IGF-IR in Asp 1048 IR cells. These results suggest that the Asp 1048 IR causes a dominant negative effect on IGF-IR in transmitting signals to Shc and MAP kinase activation, which leads to decreased IGF-I-stimulated DNA synthesis, and that the kinase-defective insulin receptor does not affect IGF-I-stimulated IRS-I phosphorylation, which leads to the normal IGF-I-stimulated glycogen synthesis.

Animals↗

PubMed1996

Quantitative evaluation of the tonic vibration reflex (TVR) in the masseter muscle.

PURPOSE: This study evaluated the efficacy of the tonic vibration reflex (TVR) elicited by high-frequency vibration in evaluating masticatory muscle excitability. SUBJECTS AND METHODS: The experiment was performed on 16 male adult volunteers, 20 to 45 years of age, without spontaneous pain or tenderness in the masticatory muscles. The subjects were seated in a chair in a fixed head position with the mouth kept open with a bite block. TVR was elicited by vibratory stimulation applied to the mandible (approximately 15 m/s2, 160 Hz). An electromyogram (EMG) was recorded bilaterally from the masseter muscles and analyzed quantitatively using an arbitrary index (TVR index) calculated from the response. Bite force was measured during clenching using a pressure-sensitive foil. RESULTS: Wide variations in the TVR index (maximum, 22.7%; minimum, 0.9%, average, 7.7%) were observed among individuals. The mean index for five subjects with a clenching habit was significantly higher than that for 11 subjects without a history of clenching. Tolperisone HCl (100 mg taken orally), a gamma-drive depressant, was found to reduce the response for 2 hours. There was a negative correlation (r = -.504, P < .05) between bite force and TVR index when the values on both sides were compared. CONCLUSIONS: The TVR may be of use in evaluating masseter muscle excitability.

Adult↗

PubMed1996

Comparison of the insulin and insulin-like growth factor 1 mitogenic intracellular signaling pathways.

We compared the intracellular insulin-like growth factor-1 (IGF-1) and insulin signaling pathways in Rat1 fibroblasts expressing the equivalent number of insulin receptors and endogenous IGF-1 receptors. Insulin and IGF-1 stimulated tyrosine phosphorylation of IRS-1 and Shc in a similar dose- and time-dependent manner. The time course of Shc phosphorylation by both IGF-1 and insulin was slower than that of IRS-1. Both phosphorylated IRS-1 and Shc associated with Grb2.Sos complexes, leading to p21ras activation. To compare the functional importance of p21ras for IGF-1-and insulin-induced DNA synthesis, single cell microinjection studies were performed. BrdU incorporation into newly synthesized DNA was measured by immunofluorescence microscopy to assess the functional importance of p21ras. Both IGF-1 and insulin stimulated BrdU incorporation, but the effect of IGF-1 was greater. Microinjection of anti-p21ras antibody completely inhibited both IGF-1-and insulin-induced DNA synthesis, indicating the central role of p21ras in signaling by both hormones. Signal transduction from these receptors to Grb2.Sos complexes can occur through IRS-1 and/or Shc. To assess these two possible pathways, we performed Western blots for Grb2 in anti-Shc and anti-IRS-1 immunoprecipitates and found that 5-fold more Grb2 was associated with Shc than with IRS-1 after either IGF-1 or insulin stimulation. Microinjection of anti-Shc antibody inhibited IGF-1 and insulin stimulation of DNA synthesis by 78% and 74%, respectively. By microinjecting Shc subdomains of GST fusion proteins, we found that Shc N-terminus, but not the Shc SH2, was the functionally important domain through which Shc interacts with IGF-1 and insulin receptors. Insulin stimulation caused hyperphosphorylation and decreased electrophoretic mobility of Sos, and a similar effect was seen with IGF-1, although the time course was delayed compared with insulin. Finally, IGF-1 activated mitogen-activated proten kinase activity more effectively than insulin. These data indicate that Shc, rather than IRS-1, appears to be the predominant functional link to Grb2.Sos complexes from the IGF-1 receptor, as it is from the insulin receptor. Although IGF-1 and insulin stimulate cell cycle progression with similar coupling mechanisms from the receptor to Shc, to Grb2.Sos, to p21ras, the delayed IGF-1 induced mobility shift of Sos could lead to, at least in part, more efficient coupling to mitogen-activated protein kinase. These findings might explain the greater mitogenic activity of IGF-1 compared with insulin.

Adaptor Proteins, Signal Transducing↗

PubMed1996

Syntheses and anti-inflammatory activities of O-acyloximes. II.

Novel O-acyloximes having an acetyl group or N-protected amino acid as an O-acyl group were synthesized by reaction with acetyl chloride or by a mixed anhydride method. 4'-Morpholinoacetophenone oxime (oxime-2) was determined to be the (E) isomer by X-ray crystal structure analysis. The anti-inflammatory activities of the test compounds were assessed in terms of the inhibitory effect on increased vascular permeability induced by histamine, and several compounds were assessed together by means of the carrageenan-induced paw edema assay. In general, acetyl oximes and tert-butyloxycarbonylphenylalanyl oximes showed inhibitory action on increased vascular permeability. Particularly important for the appearance of anti-inflammatory activity was direct attachment of the acetyl group to the oxime. Of the two isoforms of cyclooxygenase (COX-1 and COX-2), COX-1 activity was inhibited by oxime-2 and 4'-piperidinoacetophenone oxime (oxime-3) with IC50 values of 50 and 130 microM, respectively, while COX-2 activity was not inhibited. The in vitro inhibitory effect of oxime-2 and oxime-3 on COX-1 activity decreased with O-acylation of the oximes.

Animals↗

PubMed1996

Blood pressure response during dental surgery.

To investigate blood pressure and pulse rate responses to dental surgery, 21 patients 18 to 73 years of age (mean age, 42 +/- 4 years) who visited our hospital for tooth extraction were studied. Before dental treatment, the patients underwent a mental arithmetic stress test, electrocardiography, and an anxiety evaluation with the State-Trait Anxiety Inventory. Baseline blood pressure and pulse rate were 118 +/- 4/70 +/- 3 mmHg and 69 +/- 2 beats/min, respectively. Blood pressure rose by 24 +/- 3/17 +/- 2 mmHg during the mental stress test, and the magnitude of the rise in systolic blood pressure was significantly correlated with age (r = 0.81, p < 0.001) and baseline blood pressure (r = 0.56, p < 0.01). After the topical injection of local anesthetic containing 1: 80,000 epinephrine, a transient increase in systolic blood pressure was observed. The maximum blood pressure and pulse rate increases during dental surgery were 24 +/- 4/13 +/- 2 mmHg and 17 +/- 3 beats/min, respectively. Similarly, the rate pressure product increased from 8,196 +/- 486 to 11,802 +/- 682. The magnitude of the blood pressure increase during dental surgery was not correlated with age, sex, family history of hypertension, baseline blood pressure, anxiety score, or response to mental stress. On the other hand, when the subjects were divided into two subgroups according to the blood pressure response during dental surgery, the larger response group (increase in mean blood pressure greater than 15 mmHg, n = 9) required a significantly larger dose of local anesthetic than did the smaller response group. The number of cases of pericoronitis of the third molar tended to be greater in the larger response group. These results indicate that an increase in blood pressure during dental surgery cannot be predicted on the basis of baseline blood pressure or the response to mental stress, but is related to the cause of tooth extraction and the volume of local anesthetics required to control the pain.

Adolescent↗

PubMed1996

Insulin and cardiovascular diseases in Japanese work-site population with borderline to mild hypertension.

To clarify whether significant interrelations between hyperinsulinemia and cardiovascular diseases exist in Japanese, we analyzed serum insulin levels, fasting and after oral glucose load, in relation to blood pressure (BP), serum lipids, and incidence of acute myocardial infarction (MI) and stroke in 584 male employees of a railroad company with borderline to mild hypertension (age: 49 +/- 7 years, BP: 139 +/-13/90 +/- 8 mmHg, body mass index: BMI 24.0 +/- 2.8, mean +/- SD). Those who were taking antihypertensive drugs and/or hypoglycemic agents were excluded. The subjects were classified into five groups of comparable size according to sigma IRI (area composed by insulin levels at 0, 1, 2 hours post glucose load). Although averaged age, levels of fasting glucose and HbA1c were not significantly different among quintiles, the hyperinsulinemic groups had higher levels of fasting IRI and sigma glucose. Multiple regression analysis revealed that sigma IRI was associated positively with BMI, sigma glucose, systolic BP, total cholesterol, and negatively with HDL-cholesterol. During 7-year follow-up 7 cases with MI and 15 cases with stroke were registered. The subjects with MI, but not with stroke were involved in higher deciles of insulin levels. These results indicate that the insulin resistance syndrome exists in Japanese middle-aged men with borderline to mild hypertension. The association with cardiovascular morbid events appeared to be evident in coronary heart disease but not in cerebrovascular disease.

Adult↗

PubMed1995

Detection of beta-1,2-mannosyltransferase in Candida albicans cells.

A particulate insoluble fraction from Candida albicans J-1012 (serotype A) strain cells was obtained as the residue after extracting a 105,000 x g pellet of cell homogenate with 1% Triton X-100. Incubation of this fraction with a mannopentaose, Man beta 1-->2Man alpha 1-->(2Man alpha 1-->)(2)2Man (alpha beta Man5), in the presence of GDP-mannose followed by high performance liquid chromatography showed the formation of a mannohexaose. Analysis of the product by 1H NMR indicates that alpha beta Man5 was changed to Man beta 1-->2Man beta 1-->2Man alpha 1-->(2Man alpha 1-->)2 2Man (alpha beta Man6). This beta-1,2-mannosyltransferase (ManTase) II activity was completely inhibited by Zn2+ and was not restored by the addition of EDTA. The corresponding enzyme fraction from C. albicans NIH B-792 (serotype B) strain cells, the mannan of which does not possess both the alpha beta Man5 and alpha beta Man6 side chains, also exhibited the same beta-1,2-ManTase II activity.

Candida albicans↗

PubMed1995

Gene structure of rat cholecystokinin type-A receptor.

Little is known about the gene structure and mRNA expression of cholecystokinin type-A(CCKA) receptor in animals or in human. By screening an EMBL phage library containing partially digested Long-Evans rat DNA, we isolated 7 genomic clones covering a continuous 27 kb region over which a rat CCKA receptor gene spanned. The gene is approximately 10 kb in length containing the entire coding region of the rat CCKA receptor cDNA and consists of five exons interrupted by four introns. The expected sizes of the transcripts from the initiation sites were consistent with the results of northern blot analyses.

Amino Acid Sequence↗

PubMed1995

An animal model of congenital defect of gene expression of cholecystokinin (CCK)-A receptor.

Expressions of the CCK-A and B receptor genes in fetal and adult pancreas of OLETF rats were examined by the reverse transcriptase polymerase chain reaction followed by Southern blot hybridization. The pancreatic responses to various stimulants were examined in vitro and results were compared with those of control (LETO) rats. CCK-A receptor mRNA was not expressed in the fetal pancreas of either strain or in the adult pancreas of OLETF rats, but was expressed in the adult pancreas of LETO rats. CCK-B receptor mRNA was expressed in fetal and adult pancreas in both strains. Southern blot hybridization indicated a difference in gene structure in the two strains. The maximal effective concentrations of neuromedin C, carbachol, and secretin for amylase secretion and intracellular Ca2+ movement stimulated by carbachol and neuromedin C were similar in the two strains. CCK-8 and the non-sulfated form stimulated amylase secretion only in LETO rats. These results suggest that OLETF rats are a new model of a congenital defect of the CCK-A receptor gene and should be useful for determining CCK receptor function.

Amylases↗

PubMed1995

An extracellular domain of the beta subunit is essential for processing, transport and kinase activity of insulin receptor.

The extracellular portion of the insulin receptor (IR) beta-subunit has four cysteine and four asparagine residues which are potentially involved in disulphide bond formation between the alpha- and beta-subunits and N-linked glycosylation respectively. However, the function of this portion is not fully understood. In order to investigate the role of the extracellular domain of beta-subunit, we created a deletion mutant of IR cDNA which lacked 47 amino acid residues encoded by 141 bp corresponding to exon 13 of the IR gene. Insulin binding and surface labelling of COS 7 cells transiently expressing the mutant insulin receptors (IR delta Ex13) showed that the mutated receptors were not expressed on the cell surface. However, immunoblot analysis showed that uncleaved form (190 kDa) of the mutant receptors were intracellularly expressed. Deglycosylation with endoglycosidase H showed that the mutant receptors had mainly high-mannose oligosaccharide chains. The mutant IRs bound with high affinity to lentil lectin but with low affinity to wheat germ agglutinin. Therefore, it is suggested that misfolding of the mutant receptors inhibits transport to the Golgi apparatus where processing of oligosaccharide chains, as well as proteolytic cleavage into subunits, takes place. The binding affinity of the mutant receptors for insulin was 50% of normal. Furthermore, insulin-stimulated autophosphorylation of IR delta Ex13 was markedly impaired. These data provide the evidence for a critical role of the extracellular domain of IR beta-subunit for processing and transport as well as the intramolecular signal transduction to activate IR tyrosine kinase.

Base Sequence↗

PubMed1995

Long-term denopamine therapy for hemodialysis patients with chronic heart failure.

Denopamine was orally administered for more than 12 months to patients with chronic heart failure on maintenance hemodialysis. The plasma level in subjects treated with denopamine at 30 mg/day tended to be higher than that in subjects on 15 mg/day. There was no gradual increase in plasma level as the duration of therapy prolonged. Left ventricular end-diastolic and end-systolic diameters as well as ejection fraction on echocardiography showed a tendency to be improved by denopamine. Similarly, the cardiothoracic ratio was improved temporarily. No adverse effects were detected by electrocardiography and laboratory tests. These observations suggest that denopamine is safe and effective for hemodialysis patients with chronic heart failure.

Administration, Oral↗