Biomedical subjects

I Yamaguchi

Publications and source records attributed to I Yamaguchi.

At least 109 records · Page 6Linked to original sources

PubMed1998

Decreased GA1 content caused by the overexpression of OSH1 is accompanied by suppression of GA 20-oxidase gene expression.

We previously reported that overexpression of the rice homeobox gene OSH1 led to altered morphology and hormone levels in transgenic tobacco (Nicotiana tabacum L.) plants. Among the hormones whose levels were changed, GA1 was dramatically reduced. Here we report the results of our analysis on the regulatory mechanism(s) of OSH1 on GA metabolism. GA53 and GA20, precursors of GA1, were applied separately to transgenic tobacco plants exhibiting severely changed morphology due to overexpression of OSH1. Only treatment with the end product of GA 20-oxidase, GA20, resulted in a striking promotion of stem elongation in transgenic tobacco plants. The internal GA1 and GA20 contents in OSH1-transformed tobacco were dramatically reduced compared with those of wild-type plants, whereas the level of GA19, a mid-product of GA 20-oxidase, was 25% of the wild-type level. We have isolated a cDNA encoding a putative tobacco GA 20-oxidase, which is mainly expressed in vegetative stem tissue. RNA-blot analysis revealed that GA 20-oxidase gene expression was suppressed in stem tissue of OSH1-transformed tobacco plants. Based on these results, we conclude that overexpression of OSH1 causes a reduction of the level of GA1 by suppressing GA 20-oxidase expression.

Amino Acid Sequence↗

PubMed1998

Inactivation of blasticidin S by Bacillus cereus. VI. Structure and comparison of the bsr gene from a blasticidin S-resistant Bacillus cereus.

Two types of recombinant plasmids containing 600 bp Nde I fragments that coded the bsr gene in opposite directions were obtained. Nucleotide sequencing shows that the bsr encodes a 140 amino acid protein with a putative molecular weight of 15560, the same as that of purified blasticidin S (BS)-deaminase (BSR), on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) (15500). Upstream of the open reading frame, a Shine-Dalgarno (SD) sequence, frequent inverted repeats, and the sigmaA and sigmaB promoter sequences are observed. The transcriptional start point was determined to be the A located 7 bases downstream from the putative sigmaA promoter (91TTGATC and 113TAAAAT) by the primer extension method and site directed mutagenesis at the -10 or -35 promoter region. A comparison of the amino acid sequence of BSR with that of BS-deaminase from Aspergillus terreus (BSD) showed 27.2% homology. Low degrees of homology were also observed with cytidine deaminase and deoxy cytidine monophosphate (CMP) deaminase. Four conserved amino acid motifs were observed, VGAx6G, C(orH)AEx6A, SPCGxCR, and Gx8ELIP (x(n) indicates a nonspecific residue and its position). It is possible that the three Cys residues and the Glu in the conserved motifs comprise the active center. Site-directed mutagenesis of the Cys residues supports this possibility.

Amino Acid Sequence↗

PubMed1998

Effect of relatively low dose amiodarone therapy on left ventricular function in patients with ventricular tachyarrhythmias.

The effect of oral amiodarone (AMD) therapy on left ventricular (LV) function was evaluated retrospectively in Japanese patients with ventricular tachyarrhythmias and congestive heart failure. Seventeen patients were treated with oral AMD (maintenance dose 191+/-52mg/day) for more than 12 months. Fractional shortening (FS) on echocardiography revealed a trend towards an increase in the short-term (3 months) (p=0.06), but was not significant in the long-term follow-up period (more than 12 months) after AMD therapy. In 8 patients with 1 episode of myocardial infarction, FS revealed a trend towards an increase (p=0.09). In all of the 4 patients with dilated cardiomyopathy whose LV end-diastolic diameter was increased, FS was decreased in the long-term follow-up. Neither hospitalization frequency nor New York Heart Association classification were reduced by AMD therapy. In conclusion,oral AMD therapy did not cause LV function to recover significantly and could not improve the clinical course in patients with ventricular tachyarrhythmias. However, if the underlying disease is not progressive, AMD therapy may improve LV function.

Administration, Oral↗

PubMed1998

Inhaled nitric oxide in patients with pulmonary hypertension due to valvular heart disease and chronic lung disease.

The objective of this study was to investigate the effects of inhaled nitric oxide (NO) on chronic pulmonary hypertension (PH). Thirty patients with valvular heart diseases (n=8, group A), chronic lung diseases (n=16, group B), primary PH or PH due to collagen disease (n=6, group C) were studied. NO was delivered for 20 min at concentration of 5, 10, and 20 ppm in spontaneous respiration. After inhalation, percentages of systolic pulmonary artery pressure (%SPAP) levels in group A were significantly decreased compared with those for pre-inhalation by 12%, 14%, and 14% at 5, 10 and 20 ppm, respectively (p<0.05). In group B, %SPAP also significantly decreased by 7, 10, and 14% at 5, 10, and 20 ppm, respectively (p<0.05). However, inhaled NO did not significantly affect %SPAP in group C (p=0.4). There was no significant difference in gas exchange in any of the groups. However, 4 out of 8 patients in group A and 10 out of 16 patients in group B showed decreased partial pressure of arterial oxygen in response to inhaled NO. This study demonstrated that inhaled NO is a selective pulmonary vasodilator in decreasing pulmonary artery pressure (PAP); however, the reaction was different in line with the background disease cause of PH. NO inhalation was most effective on patients with moderate PAP. Furthermore, higher concentrations of NO would be risky in some patients with chronic PH.

Administration, Inhalation↗

PubMed1998

Impaired peripheral vasoconstriction in response to alpha-adrenergic stimulation in patients with idiopathic hypertrophic cardiomyopathy.

Exercise hypotension has been documented in patients with hypertrophic cardiomyopathy (HCM). Some investigators reported that this is due to an inadequate increase of systemic vascular resistance during or after exercise. The aim of this study was to investigate the pathogenesis of limb vascular response abnormalities in patients with idiopathic HCM. Thirteen patients with HCM and 9 healthy controls were administered an endothelium-dependent dilator (acetylcholine), a direct smooth muscle dilator (nitroglycerin), an alpha-adrenergic stimulator (phenylephrine), and a beta-adrenergic stimulator (isoproterenol) by intra-arterial infusion. Peripheral vascular resistance was assessed by forearm plethysmography at rest and during each infusion to obtain the percentage change in vascular resistance. Isoproterenol, acetylcholine and nitroglycerin produced dose-related vasodilatation with no significant differences between HCM patients and healthy controls. The percentage increase in vascular resistance was significantly less in HCM patients than in healthy controls after phenylephrine infusions of 0.5 microg/min (155+/-38% vs 195+/-47%, mean+/-SD, p<0.05) and 1.0 microg/min (174+/-49% vs 238+/-65%, p<0.05). Vasoconstriction mediated by alpha-adrenergic receptors appeared to be impaired in the peripheral vasculature of patients with HCM.

Adrenergic alpha-Agonists↗

PubMed1998

Features of Tri101, the trichothecene 3-O-acetyltransferase gene, related to the self-defense mechanism in Fusarium graminearum.

A structural gene of Tri101, which encodes trichothecene 3-O-acetyltransferase, was isolated as a 3-kb XhoI-XbaI fragment from the trichothecene producer Fusarium graminearum strain F15. The gene contained no introns, and the coding region was 0.7-kb downstream of a putative UTP-ammonia ligase gene which obviously is not related to the biosynthesis of trichothecenes. Tri101 was expressed when T-2 toxin was added, but this induction was not dependent on the expression level of Tri6, a transcription activator gene in the trichothecene biosynthetic and regulatory gene cluster.

Acetyltransferases↗

PubMed1998

cDNA cloning, expression, and mutagenesis of scytalone dehydratase needed for pathogenicity of the rice blast fungus, Pyricularia oryzae.

We purified scytalone dehydratase from the rice blast fungus, Pyricularia oryzae, and cloned its cDNA on the basis of its amino acid sequence. The deduced amino acid sequence was 62% identical to the scytalone dehydratase from Colletotrichum lagenarium. The expression of this gene was induced transcriptionally in the stationary phase when melanin synthesis occurs. We constructed a heterologous expression system for the enzyme in Escherichia coli, did deletion analysis with this system, and found that a C-terminal region is essential for the enzyme function.

Amino Acid Sequence↗

PubMed1998

REMI mutagenesis and identification of pathogenic mutants in blast fungus (Magnaporthe grisea).

Blast fungus' mutant, which is very difficult to obtain, is the key substance in the study of the relation between pathogen and plant. Rice-Aichi-ashahi was used as the host and plasmid pBF101 or pCSN43 as foreign DNA fragment, and REMI mutagenesis was applied to tag the pathogenic sequence in rice blast fungus M.grisea. Three mutants (R2H65, R2H69 and R2B1565) related to pathogenicity were recovered from several hundreds of transformants. R2H69 and R2H65 produced merely strange conidia which could not form appressorium or yield abnormals, and pathogenicity test further confirmed that they were unable to cause disease. R2B1565 possesses the same phenotypes as those of the wild type except that the ability of causing disease was much reduced.

DNA Restriction Enzymes↗

PubMed1998

Characterization of stress-induced sudden death in cardiomyopathic hamsters.

Stress is known clinically and experimentally to contribute to the development or exacerbation of cardiovascular dysfunction. In an attempt to construct an animal model of stress-induced cardiovascular dysfunction and to understand its mechanisms, the effects of cold-immobilization stress and its cardiovascular consequences were investigated in cardiomyopathic Syrian hamsters (BIO 14.6) and age-matched healthy control hamsters. Repeated exposure (5 days) to cold-immobilization in the supine position induced no detectable ill effects in the healthy control hamsters but had a lethal effect in the cardiomyopathic hamsters: more than half of the animals died suddenly during or after the stress sessions. Autopsy study of these animals showed significant increases in the weights of the heart, adrenal, liver and kidney and in the serum levels of alkaline phosphatase, urea nitrogen, creatinine and glucose in the cardiomyopathic hamsters subjected to the stress. Propranolol (0.1-10 mg/kg i.p.) administered just before each cold-immobilization for 5 consecutive days dose-dependently and significantly prevented the lethal effects of the stress. Furthermore, it was demonstrated that the drug significantly reduced the increase in the weights of the heart, adrenal, liver and kidney observed in the stressed cardiomyopathic hamsters, whereas phentolamine (0.1-10 mg/kg) and atropine (0.1-10 mg/kg) did not prevent the stress-induced sudden death. The series of acute experiments using single exposure of this stress revealed that the stress evoked severe arrhythmia in some of the cardiomyopathic hamsters and increased the levels of circulating catecholamines in both healthy and cardiomyopathic hamsters. These results taken together suggest that stress accelerates the cardiovascular dysfunction in cardiomyopathic hamsters and provide the first evidence that excitation of the sympathetic nerves, in which beta-adrenoceptors appear to be involved, but not the parasympathetic nerves, has an important role in the etiology of stress-induced cardiac sudden death of cardiomyopathic hamsters.

Animals↗

PubMed1998

[New predictive formulas of pulmonary function in Japanese children].

Socioeconomic conditions, including nutrition, have improved dramatically over the past four decades in Japan. Those improvements have elicited significant changes in the developmental growth and average size of Japanese children. These trends suggest that predictive formulas of pulmonary function need to be revised. Our study enrolled 446 children (222 boys and 224 girls ranging in age from 5 to 16 years) who had no history of respiratory disease. The subjects were examined by spirometry. We formulated regression equations for several measures of ventilatory function by age, weight, and height, including vital capacity (VC), forced vital capacity (FVC), and forced expiratory volume in one second (FEV1.0), using data randomly selected from 70% of the children. Optimum parameters for the equations were selected by calculating Akaike information criteria (AIC) and Mallow's index C (p). The optimum regression equations were tested for their predictive value as acceptable predictive formulas by evaluating data randomly selected from 30% of the children. These new formulas are considered to be better suited for modern-day evaluations of pulmonary function in Japanese children.

Adolescent↗

PubMed1997

Partial purification and characterization of a gibberellin-binding protein from seedlings of Azukia angularis.

Little is known about mechanisms for the perception of gibberellin (GA), a phytohormone, by plants. A GA-binding protein (GBP) with receptor-like characteristics was partially purified from azuki bean (Azukia angularis) seedlings. Gibberellins that caused much elongation of azuki epicotyl sections showed strong binding affinity for the GBP, and their biosynthetic precursors and inactive metabolites had weak affinity for it. The apparent Kd value for GA4 was calculated to be 7 x 10(-10) M from Scatchard plots. The molecular weight of the GBP in the native state was estimated to be 25,000 by high-performance liquid chromatography with a gel-permeation column. The GBP may be one of the receptor candidates for GAs.

Carrier Proteins↗

PubMed1997

The rat D4 dopamine receptor couples to cone transducin (Galphat2) to inhibit forskolin-stimulated cAMP accumulation.

Based on its expression pattern and pharmacology, the D4 dopamine receptor may play a role in schizophrenia. Thus it is of interest to know what signaling pathways are utilized by this receptor. Previously, we showed that activation of D4 receptors in a mouse mesencephalic neuronal cell line (MN9D) inhibited forskolin-stimulated cAMP accumulation in a pertussis toxin-sensitive (Ptx-sensitive) fashion. Of the known Ptx-sensitive G-protein alpha subunits, MN9D-expressed Galphai2, GalphaoA, and GalphaoB; however, none of these coupled to the D4 receptor. Using a low stringency polymerase chain reaction cloning method, we found an additional Ptx-sensitive G-protein cone transducin (Galphat2) expressed in the MN9D cells. We also found that Galphat2 mRNA is highly expressed in rat mesencephalic tissue. To test the hypothesis that the D4 receptor couples to Galphat2, we cotransfected MN9D cells with the D4 receptor and a mutagenized Ptx-resistant Galphat2 subunit (mGalphat2). Application of the dopaminergic agonist quinpirole to cotransfected cells inhibited forskolin-stimulated cAMP accumulation in the presence or absence of Ptx. To our knowledge, this is the first report demonstrating that the D4 dopamine receptor functionally couples to a specific G-protein and that a non-opsin-like receptor can couple with a transducin subunit.

Animals↗

PubMed1997

Dopamine D1A receptors and renin release in rat juxtaglomerular cells.

Two dopamine D1-like receptors have been cloned from mammals, the D1 and D5 receptors, also known as D1A and D1B receptors, respectively, in rodents. Although D1-like receptors are known to stimulate renin release, the receptor subtype mediating this action has not been determined. We investigated D1 receptor subtype expression in rat juxtaglomerular cells obtained after enzymatic dispersion of kidney cortex and differential centrifugation. Juxtaglomerular cells in primary culture were immunocytochemically 85% to 95% renin positive. These cells expressed the D1A but not the D1B receptor (mRNA and protein). D1-like receptor function was demonstrated by a concentration-dependent stimulation of cAMP production by dopamine (n = 5-9 per group). Fenoldopam, a D1-like receptor agonist, also caused a concentration-dependent increase in cAMP production and renin secretion that was blocked by the selective D1-like receptor antagonist SCH23390 (n = 4-13 per group). Although the D1 ligands do not distinguish between the cloned D1-like receptors, the actions of fenoldopam were due to occupancy of the D1A receptor: (1) the D1B receptor, the only other mammalian D1-like receptor, is not expressed in juxtaglomerular cells; (2) antisense but not sense D1A oligonucleotides completely blocked the stimulatory effect of fenoldopam on cAMP production and renin secretion. We conclude that there is selective dopamine receptor gene expression in juxtaglomerular cells; the dopamine receptor subtype linked to the stimulation of cAMP and renin secretion in juxtaglomerular cells is the D1A subtype.

Animals↗

PubMed1997

Stress increases plasma enzyme activity in rats: differential effects of adrenergic and cholinergic blockades.

Plasma creatine phosphokinase, lactic dehydrogenase, glutamic-oxaloacetic transaminase and glutamic-pyruvic transaminase activities significantly increased in rats immersed in 23 degrees C water for 6 hr after restraint (water immersion stress). The stress-induced rises in the four enzymes were significantly prevented by the intraperitoneal injection of 6-hydroxydopamine (80 mg/kg), propranolol (1 and 10 mg/kg) or timolol (1 and 10 mg/kg) but not by phentolamine (0.1-10 mg/kg) and atropine (0.1-10 mg/kg). The stress also significantly increased plasma urea nitrogen and glucose levels; however, neither propranolol (0.1-10 mg/kg) nor timolol (0.1-10 mg/kg) did affect these levels. On the other hand, 6-hydroxydopamine (80 mg/kg) and phentolamine (10 mg/kg) slightly but significantly prevented the increase in plasma urea nitrogen level, and the stress-induced hyperglycemia was significantly prevented by either phentolamine (10 mg/kg) or atropine (1 and 10 mg/kg). Plasma norepinephrine and epinephrine levels were also increased significantly by the stress, and the norepinephrine response was suppressed significantly by 6-hydroxydopamine. In conclusion, excessive peripheral sympathetic activity possibly plays an important role in the water immersion stress-induced increases in the plasma enzymes activity primarily via beta-adrenoceptors, whereas alpha-adrenoceptors and the cholinergic nerves might be involved in the stress-induced increases in plasma urea nitrogen and glucose levels.

Adrenergic Antagonists↗

PubMed1997

Insulin attenuates formalin-induced nociceptive response in mice through a mechanism that is deranged by diabetes mellitus.

Although hypoglycemic doses of insulin (0.24-7.5 U/kg s.c.) did not significantly change acetic acid-induced writhing in mice, they dose-dependently attenuated formalin-induced nociceptive responses, and their effects were more potent on the second phase (ID50 = .62 U/kg) than on the first (ID50 > 7.5 U/kg). Intracerebroventricular doses of insulin (250-1000 microU/animal) mimicked the effects of the s.c. dose, but caused little change in blood glucose levels. The antinociceptive activity of insulin (0.75 U/kg, s.c.) in the formalin test was significantly inhibited by naloxone (10 mg/kg i.p., an opiate receptor antagonist), sulpiride (10 mg/kg i.p., a dopamine 2 receptor antagonist), pindolol (1 mg/kg i.p., a 5-hydroxytryptamine 1 receptor antagonist) and ketanserin (1 mg/kg i.p., a 5-hydroxytryptamine 2 receptor antagonist), but not by 3-tropanyl-indole-3-carboxylate (1 mg/kg i.p., a 5-hydroxytryptamine 3 receptor antagonist). Insulin also exerted antinociception in streptozotocin-induced diabetic mice and genetically diabetic db/db mice which, however, were less sensitive (ID50s around 7.5 U/kg) to the of insulin effect than normal mice. The results suggest that insulin attenuates chronic rather than acute pains through a mechanism mediated by dopamine, 5-hydroxytryptamine and opioids. The antinociceptive pathway appears to be deranged by diabetes mellitus.

Analgesics↗

PubMed1997

Possible involvement of 5-HT2 receptor activation in aggravation of diet-induced acute pancreatitis in mice.

Acute pancreatitis was induced in mice by feeding with a choline-deficient ethionine-supplemented diet. All the mice developed acute pancreatitis, and approximately 80% of them died within 4 days. Stereomicroscopic and light microscopic examinations revealed that pancreatic necrosis and circulatory disturbance that were not apparent on day 1 were increased markedly on days 2 and 3. Serum levels of pancreatic enzymes were normal or reduced on day 1 but then increased to peak on day 3. Plasma 5-hydroxyindoleacetic acid levels, which may indicate serotonin release, were significantly increased on days 1 through 3. Pretreatment with D, L-p-chlorophenylalanine methylester hydrochloride (200-400 mg/kg) significantly attenuated the mortality of the mice with pancreatitis. Dose-dependent attenuation was also obtained with ketaserin (0. 01-10 mg/kg), cyproheptadine (0.01-10 mg/kg), pindolol (0.1-100 mg/kg) and NAN-190 (0.1-100 mg/kg), but not with 0.01 to 10 mg/kg of ICS205-930 or M-840, and the activities were significantly correlated with the binding affinities for serotonin2 receptor on the rat cerebral cortex. In addition, ketanserin or cyproheptadine attenuated the morphologic changes in the choline-deficient ethionine-supplemented diet mice at a dose (3.2 mg/kg) that hardly affected the serum enzyme levels. We propose that serotonin2 receptor activation plays an important role in the aggravation of diet-induced acute pancreatitis.

Acute Disease↗

PubMed1996

Inhibition of myocardial endothelin pathway improves long-term survival in heart failure.

Occlusion of the diseased coronary artery in humans causes acute myocardial infarction, survivors of which have a high risk for the development of chronic heart failure. Cardiac myocytes and vascular endothelial cells produce endothelin-1 (refs 2-4), which increases the contractility of cardiac muscle and of vascular smooth muscle cells. Endothelin-1 also exerts long-term effects such as myocardial hypertrophy, and causes cellular injury in cardiac myocytes. Production of endothelin-1 is markedly increased in the myocardium of rats with heart failure, and acute application of an endothelin-receptor antagonist decreases myocardial contractility in such rats, indicating that myocardial endothelin-1 may help to support contractility of the failing heart. But we report here that the upregulated myocardial endothelin system may contribute to the progression of chronic heart failure, because long-term treatment with an endothelin-receptor antagonist greatly improved the survival of rats with chronic heart failure. This beneficial effect was accompanied by significant amelioration of left ventricular dysfunction and prevention of ventricular remodelling, in which there is usually an increase in the ventricular mass and cavity enlargement of the ventricle.

Animals↗

PubMed1996

Pulmonary hypertension caused by congestive heart failure is ameliorated by long-term application of an endothelin receptor antagonist. Increased expression of endothelin-1 messenger ribonucleic acid and endothelin-1-like immunoreactivity in the lung in congestive heart failure in rats.

OBJECTIVES: The purpose of this study was to investigate whether 1) endothelin-1, a potent vasoconstrictor peptide, is involved in progression of pulmonary hypertension caused by congestive heart failure (CHF); and 2) whether long-term treatment with BQ-123, an endothelin receptor antagonist, ameliorates pulmonary hypertension caused by CHF. BACKGROUND: Congestive heart failure accompanies pulmonary hypertension, and the severity of pulmonary hypertension is an important determinant of prognosis. Although we reported that production of endothelin-1 is increased in the failing heart in rats with CHF, it is not known whether production of endothelin-1 in the lung is altered by CHF. METHODS: Congestive heart failure was induced by coronary artery ligation in rats. Expression of preproendothelin-1 messenger ribonucleic acid (mRNA) in the lung and kidney was determined. Endothelin-1 staining (immunoreactivity) in the lung was studied by immunohistochemical analysis. Effects of long-term BQ-123 treatment on the rats were studied. RESULTS: Two weeks postoperatively, CHF accompanied by pulmonary hypertension developed in the rats (CHF rats). Expression of preproendothelin-1 mRNA in the lung was markedly higher in the CHF rats than in the sham-operated rats, whereas that in the kidney did not differ between the two groups. Endothelin-1 staining on the pulmonary vascular endothelial cells was more intense in the CHF rats. BQ-123 treatment over a 2-week period in the CHF rats greatly reduced right ventricular systolic pressure and central venous pressure, but it did not affect blood pressure or left ventricular contractility (peak positive first derivative of left ventricular pressure) in these rats. CONCLUSIONS: Long-term BQ-123 treatment greatly ameliorated pulmonary hypertension in the CHF rats. The present study suggests that endothelin-1 plays an important role in the progression of pulmonary hypertension caused by CHF and that an endothelin receptor antagonist may be a new therapeutic agent for CHF-induced pulmonary hypertension.

Animals↗