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N Hirayama

Publications and source records attributed to N Hirayama.

At least 19 recordsLinked to original sources
PubMed1999

Tyrosine kinase involvement in apamin-sensitive inhibitory responses of rat distal colon.

1. It has been suggested that pituitary adenylate cyclase activating peptide (PACAP) may be involved in the non-adrenergic, non-cholinergic (NANC) inhibitory response of longitudinal muscle of rat distal colon. In this study, we have investigated the intracellular mechanism of PACAP-induced relaxation in this muscle. 2. PACAP induced an apamin-sensitive relaxation of the longitudinal muscle. The tyrosine kinase inhibitors genistein at 10 microM and tyrphostin 25 at 30 microM, but not the cyclic AMP-dependent protein kinase inhibitor Rp-8-bromoadenosine-3',5'-cyclic monophosphorothioate at 30 microM significantly inhibited the PACAP-induced relaxation to 60% and 25% of control values, respectively. PACAP did not increase the cyclic AMP content of the muscle. 3. Tyrphostin 25 at 10 microM significantly inhibited the relaxation of longitudinal muscle induced by electrical field stimulation (EFS), to 50% of control values. Apamin at 1 microM, an antagonist of small conductance Ca2+-activated K+ channels, also inhibited the relaxation, to 42 % of control values. The inhibitory effects of tyrphostin 25 and apamin were not additive (44 % of control values). 4. PACAP induced an apamin-sensitive, slow hyperpolarization of the cell membrane of the muscle. Tyrphostin 25 at 3 microM inhibited this PACAP-induced hyperpolarization. Tyrphostin 25 at 10 microM and genistein at 10 microM inhibited the apamin-sensitive inhibitory junction potentials induced by a single pulse of EFS. 5. The PACAP-induced relaxation of longitudinal muscle occurred with a concomitant decrease in intracellular Ca2+ levels ([Ca2+]i). Tyrphostin 25 at 10 microM and apamin at 1 microM abolished these PACAP-induced responses. 6. From these findings it is suggested that the activation of tyrosine kinase is involved in PACAP-induced relaxation of longitudinal muscle from rat distal colon, 'upstream of' the activation of apamin-sensitive K+ channels.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1999

Molecular forms of circulating adrenomedullin in patients with congestive heart failure.

In the biosynthesis of adrenomedullin (AM), an intermediate form, AM(1-52)-glycine-COOH (iAM), is cleaved from proAM and subsequently processed to a biologically active mature form, AM(1-52)-NH2 (mAM), by enzymatic amidation. We recently reported that immunoreactive AM in human plasma consists of mAM and iAM. To clarify the pathophysiological roles of mAM and iAM in heart failure, we established an assay method to specifically detect mAM, and we determined the plasma concentrations of mAM and iAM in 68 patients with congestive heart failure (CHF). The plasma mAM concentrations of the CHF patients classified as being class I or II of New York Heart Association (NYHA) functional classification were significantly greater than those of the 28 healthy controls, and a further increase was noted in the class III or IV patients. Similar increases in plasma iAM were also observed in these patients compared with controls. The increased plasma mAM and iAM in 12 patients with exacerbated CHF were significantly reduced by treatment of their CHF for 7 days. In addition, the plasma concentrations of both mAM and iAM were significantly correlated with pulmonary capillary wedge pressure, pulmonary artery pressure, right atrial pressure, cardiothoracic ratio, heart rate, and the plasma concentrations of atrial and brain natriuretic peptides in the CHF patients. Thus the plasma concentrations of both mAM and iAM were increased progressively in proportion to the severity of CHF. These results suggest that, though the role of iAM remains to be clarified, mAM acts against the further deterioration of heart failure in patients with CHF.

Adrenomedullin↗
PubMed1998

Separation of the two reactions, oxidation and isomerization, catalyzed by Streptomyces cholesterol oxidase.

Site-directed mutagenesis was used to identify key amino acid residues of the cholesterol oxidase from Streptomyces sp., which catalyzes the oxidation of cholesterol and the isomerization of 5-cholesten-3-one. Eight mutant enzymes were constructed and the following amino acid substitutions were identified: N318A, N318H, E356A, E356D, H441A, H441N, N480A and N480Q. Mutants N318A and N318H retained both oxidation and isomerization activities. The mutant E356D retained oxidation but not isomerization activity. On the other hand, mutants N480A and N480Q showed no oxidation activity but retained their isomerization activities. The two catalytic reactions, oxidation and isomerization, in cholesterol oxidase were thus successfully separated. When the H441A or H441N mutation was introduced, both the oxidase and isomerase activities were completely lost. The H441, E356 and N480 residues thus appear to participate in the catalysis of cholesterol oxidase, whereas N318 does not. An analysis of the products of these mutant enzymes suggested that the previously proposed 6-hydroxylation reaction by cholesterol oxidase is actually autooxidation from 5-cholesten-3-one. Kinetic studies of the purified wild-type and mutant enzymes showed that the k(cat)/Km values for oxidation in E356D and for isomerization in N480A increased six- and threefold, respectively, over those in the wild-type. These mutational effects and the reaction mechanisms are discussed in terms of the three-dimensional structure of the enzyme constructed on the basis of homology modeling.

Amino Acids↗
PubMed1998

Effect of non-ionic detergents on apparent enzyme mechanism: V121A mutant of Streptomyces cholesterol oxidase endowed with enhanced sensitivity towards detergents.

One of the mutants of Streptomyces cholesterol oxidase with the Val121Ala mutation (V121A) was kinetically analysed. Although the reaction rate-substrate concentration curve of wild type follows a simple Michaelis-Menten equation, that of V121A is sigmoidal. The cooperativity was apparent and caused by non-ionic detergents that were used as a solvent of cholesterol. The concentration dependence of V121A on detergents was more significant than that of wild type, although the reaction rates of both enzymes decrease as the concentrations of detergents increase. Further experiments suggested that less hydrophobic interactions between V121A and detergents should be responsible for the apparent cooperativity. Since Val121 is in a hydrophobic loop located near the active site, the mutational effect is structurally discussed.

Binding Sites↗
PubMed1998

Incidence of urogenital cancers in Gunma Prefecture, Japan: a 10-year summary.

BACKGROUND: Although the incidence of urogenital cancers in Japan is lower than that of other cancers, it is increasing steadily. Thus, an epidemiologic study was necessary to determine the measures that would decrease the mortality rate associated with these cancers. METHODS: The subjects were 4759 patients with urogenital cancer who were living in Gunma Prefecture and who were newly diagnosed between 1985 and 1994. The data were analyzed by year and by patients' ages. The incidence rates of each disease were expressed as the number of cases per 100,000/year, and age-adjusted rates were adjusted to the world population. RESULTS: The number of males and females afflicted by urogenital cancers increased over the 10-year period. The increase in age-adjusted incidence rates was sharpest for prostate, renal cell, and testicular cancers among males, and for renal cell, renal pelvic and ureter cancers among females. When age-specific rates were plotted against age on double logarithmic scales, the cancers were classified as type 1 (linear), type 2 (linear until a certain age, then flattening out or decreasing), or type 3 (irregular) based on the slope of the line. The magnitude of increase in the age-specific incidence rates of type 1 cancers with age was on the order of the 12th power for prostate cancer and the 5th power for bladder cancer. When the 10 years were divided into 2 periods (earlier and later), the age-specific incidence rates of prostate and renal cell cancers increased in all age groups, whereas the age-specific incidence rates of cancers that increased less sharply remained stable or even declined in some age groups. CONCLUSION: These epidemiologic data should be useful in reducing the mortality rates associated with these cancers.

Adult↗
PubMed1997

Structure of KW-2228, a tailored human granulocyte colony-stimulating factor with enhanced biological activity and stability.

KW-2228 is a tailored human granulocyte colony-stimulating factor (hG-CSF) which has more potent granulopoietic activity and is more stable than wild-type hG-CSF. Analysis of the 2.3 A resolution crystal structure of KW-2228 unambiguously revealed a four-alpha-helix bundle motif with up-up-down-down connectivity. The structures of long overhand loops connecting the helices and the N-terminus have been definitively determined. The present analysis has clearly revealed that substituted residues play important roles in fastening a long overhand loop to the N- and C-termini to fix the conformation. This conformation should be responsible for a substantial enhancement of the biological activity and stability.

Crystallography, X-Ray↗
PubMed1997

Improvement of thermal stability of Streptomyces cholesterol oxidase by random mutagenesis and a structural interpretation.

Random mutagenesis was used to enhance the thermal stability of Streptomyces cholesterol oxidase. Four thermostable mutants were isolated and the following amino acid substitutions were identified: Ser103 to Thr (mutant S103T), Val121 to Ala (mutant V121A), Arg135 to His (mutant R135H) and Val145 to Glu (mutant V145E). The wild-type and mutant enzymes were purified and characterized. The properties of mutants S103T, V121A and R135H were similar to those of the wild type but they showed improved thermal stability. When the V145E mutation was introduced, the thermal stability of the enzyme was markedly increased and the optimum pH was desirably changed to encompass a broad range from acid to alkali. Analysis of multiple mutants constructed by site-directed mutagenesis showed that all the mutations except that of R135H had an additive influence on the other mutations. These mutational effects are discussed in terms of a three-dimensional structural model of the enzyme constructed on the basis of homology modelling.

Cholesterol↗
PubMed1997

Molecular and phylogenetic analyses of the haemagglutinin (H) proteins of field isolates of canine distemper virus from naturally infected dogs.

We isolated three strains of canine distemper virus (CDV)--the Ueno, Hamamatsu, and Yanaka strains--from dogs in Japan and analysed the molecular properties of their haemagglutinin (H) proteins. Immunoprecipitation of all three strains with a monoclonal antibody revealed H proteins with molecular masses of 84 kDa, which differs from the molecular mass (78 kDa) of the H protein of the Onderstepoort vaccine strain. However, after tunicamycin treatment immunoprecipitation identified H proteins of identical molecular mass (68 kDa) for all three field isolates and the vaccine strain. Sequence analysis showed nine potential sites for asparagine-linked glycosylation in the H proteins of the new isolates, in contrast to four in the H protein of the Onderstepoort strain. Thus, variation in glycosylation of the H proteins of the isolates and the vaccine strain may cause differences in antigenicity of the viruses. Sequences of the H genes showed that the new Japanese isolates have 99% identity with each other, 95% with other European and American isolates (from seals, a German dog, a ferret and large felids) and 90% with the vaccine strain. Phylogenetically, the new Japanese isolates form one cluster which is separate from recent European or American isolates, all of which are distinct from vaccine strains.

Amino Acid Sequence↗
PubMed1996

Structural studies of mitomycins. VIII. Mitomycin D hydrate, C15H18N4O5.1.5H2O.

The title compound, [1aS]-6-amino-1, 1a,2,4,7,8,8a,8b-octahydro-8a-hydroxy-1,5-dimethyl-4,7-dioxoazirino++ +[2',-3': 3,4]pyrrolo[1,2-a]indol-7-ylmethyl, is a mitomycin derivative, mitomycins being antitumor antibiotics. The O atoms of the quinone ring deviate significantly from the least-squares plane through the quinone ring.

Antibiotics, Antineoplastic↗
PubMed1996

Structural studies of mitomycins. VII. Mitomycin G.

The title compound, [1aS-(1a alpha, 8a alpha, 8b alpha)]-6-amino-1, 1a,2,8,8a,8b-hexahydro-8a-methoxy-1,5-dimethyl-8-methyleneazirino [2',3':3,4]pyrrolo[1,2-a]indole-4,7-dione, C15H17N3O3, is a derivative of the mitomycins, which are antitumor antibiotics. The quinone O atoms deviate significantly from the least-squares plane of the quinone ring.

Antibiotics, Antineoplastic↗
PubMed1996

Use of ELISA for in vitro potency test of rabies vaccines for animal use.

The use of ELISA for the potency test of inactivated rabies vaccines for animal use was evaluated. Sandwich ELISA was developed, using monoclonal antibodies which enabled to recognize the glycoprotein (G-protein) of rabies virus and showed a protective effect in mice. Soluble G-protein which displays an ELISA activity but a low immunogenicity was removed by gel filtration before ELISA was carried out. The ELISA titres of the first fraction of vaccines separated by gel filtration were correlated with the neutralizing antibody titres of vaccinated guinea-pigs. Our results suggest that the ELISA titres of the first fraction of vaccines separated by gel filtration reflected the protective G-protein contents for the in vitro potency test of rabies vaccines compared with the current in vivo test.

Animals↗
PubMed1996

Increased plasma adrenomedullin in acute myocardial infarction.

Adrenomedullin has a potent vasodilating effect comparable to that of calcitonin gene-related peptide. To investigate the pathophysiologic role of endogenous adrenomedullin, we determined sequentially the plasma adrenomedullin level in 15 consecutive patients with acute myocardial infarction (AMI). Plasma adrenomedullin was higher immediately after the onset of AMI and decreased gradually; plasma levels during the 3-week period after the AMI were higher than plasma levels in 15 healthy control subjects (p < 0.001), with higher levels in patients with congestive heart failure than in patients without congestive heart failure throughout the period of the study (p < 0.05). Plasma adrenomedullin was positively correlated with pulmonary capillary wedge pressure, pulmonary arterial pressure, right atrial pressure, and heart rate in the early stage of AMI. These findings suggest that the elevation of plasma adrenomedullin is related to the retention of body fluid volume, the enhancement of sympathetic activity, and/or the elevation of pressure in pulmonary vascular beds. Adrenomedullin may act against excessive vasoconstrictors increased in AMI.

Adrenomedullin↗
PubMed1996

[A structure based pharmaceutical database for drug interactions].

A structure-based pharmaceutical database for drug interactions has been developed. This database is based on the ISIS/Desktop and the Microsoft Access relational database system for Windows. Data of Japanese accepted name, molecular formula, molecular weight, CAS registry number, therapeutic category index code, structural formula, Japan ethical drugs code, side effects information, drug interactions information were taken from "Japanese Accepted Names for Pharmaceuticals 1992", "Drugs in Japan Ethical Drugs 1993" and "Drug Intelligence Reinforce".

Chemistry, Pharmaceutical↗
PubMed1995

(E)-4-(2-[[3-(indol-5-yl)-1-oxo-2-butenyl]amino]phenoxy)butyric acid derivatives: a new class of steroid 5 alpha-reductase inhibitors in the rat prostate. 1.

A series of (E)-4-(2-[[3-(indol-5-yl)-1-oxo-2-butenyl]amino]phenoxy)butyric acid derivatives was prepared, and the derivatives were demonstrated to be potent inhibitors of steroid 5 alpha-reductase in the rat prostate. The structure-activity relationships were as follows. An alpha-branched alkyl or benzyl substituent of proper size at position 1 of the indole is crucial for optimal enzyme inhibitory activity. N-Methylation of the amide NH resulted in complete loss of activity. Thus, coplanarity of the benzene ring and amide moiety is essential for such activity. Among the compounds prepared, (E)-4-(2-[[3-[1-[bis(4-fluorophenyl)methyl]indol-5-yl]-1-oxo-2- butenyl]-amino]phenoxy)butyric acid (57, KF18678) was one of the most potent compounds (rat prostate 5 alpha-reductase IC50 = 3.3 nM).

5-alpha Reductase Inhibitors↗