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Biomedical subjects

Hiroyuki Ito

Publications and source records attributed to Hiroyuki Ito.

At least 55 records · Page 3Linked to original sources
PubMed2004

Cloning and heterologous expression of a glucodextranase gene from Arthrobacter globiformis I42, and experimental evidence for the catalytic diad of the recombinant enzyme.

The gene encoding a glucodextranase from Arthrobacter globiformis I42 was cloned and, subsequently, heterologously expressed in Escherichia coli. This glucodextranase gene consists of 1048 amino acid residues with a calculated molecular mass of 109,135 Da. The roles of two residues at the active site of A. globiformis I42 glucodextranase were examined by site-directed mutagenesis. Glutamic acid residues 458 and 656, which are part of the apparent catalytic residues, were found to be essential for hydrolase activity.

Journal Article↗
PubMed2004

Cloning and heterologous expression of a beta-fructofuranosidase gene from Arthrobacter globiformis IFO 3062, and site-directed mutagenesis of the essential aspartic acid and glutamic acid of the active site.

We have cloned the gene encoding a beta-fructofuranosidase from Arthrobacter globiformis IFO 3062, and subsequently, the gene was heterologously expressed in Escherichia coli. This beta-fructofuranosidase gene encodes a protein of 548 amino acid residues with a calculated molecular mass of 60,519 Da. We have examined the roles of three residues of A. globiformis IFO 3062 beta-fructofuranosidase by site-directed mutagenesis, and found that aspartic acid 130 and glutamic acid 392, which are two of the apparent catalytic residues, are essential for hydrolase activity. This study provides the first experimental evidence showing that these two amino acid residues of beta-fructofuranosidase play a critical role in hydrolyzing sucrose.

Journal Article↗
PubMed2004

Enzymatic synthesis of two novel non-reducing oligosaccharides using transfructosylation activity with beta-fructofuranosidase from arthrobacter globiformis.

Two novel non-reducing oligosaccharides together with tri- and tetra-saccharides were synthesized by transfructosylation activity from sucrose as a donor and cellobiose or cellotriose as an acceptor with a purified beta-fructofuranosidase from Arthrobacter globiformis IFO 3062, and these oligosaccharides were identified as O-beta-D-glucopyranosyl-(1-->4)-alpha-D-glucopyranosyl-(1-->2)-alpha,beta-D-fructofuranoside and O-beta-D-glucopyranosyl-(1-->4)-beta-D-glucopyranosyl-(1-->4)-alpha-D-glucopyranosyl-(1-->2)-alpha,beta-D-fructofuranoside by spectrometric analyses. Both oligosaccharides were stable under condition at 100 degrees C for 30 min, and showed no degradation at pH 2.

Arthrobacter↗
PubMed2004

Site-directed mutagenesis establishes aspartic acids-227 and -342 as essential for enzyme activity in an isomalto-dextranase from Arthrobacter globiformis.

Isomalto-dextranase, from Arthrobacter globiformis T6, is a member of the glycoside hydrolase family 27. However, the alignments of the whole amino acid sequence are distinct from other members of this family. The enzymes cleave the glycosidic bond of the substrate in two different manners: either retaining or inverting the anomeric configuration. We believe that a retaining enzyme is involved in a two-step, double-displacement mechanism utilizing active site carboxylic acids as the nucleophile and general acid/base catalysts in the hydrolytic reaction. The critical amino acid residues at the isomalto-dextranase active site that catalyzes the hydrolysis reaction of dextran have been identified and the roles of nine amino acid residues (D107, D163, D227, D295, D340, D342, D373, D396, and E420) in the isomalto-dextranase from A. globiformis analyzed by site-directed mutagenesis. Of 15 mutant enzymes that were prepared, eight had reduced activities for dextran hydrolysis. Aspartic acids-227 and -342, which are part of the apparent catalytic dyad, were essential for hydrolase activity toward dextran.

Animals↗
PubMed2004

Ten rice peroxidases redundantly respond to multiple stresses including infection with rice blast fungus.

Class III plant peroxidases are believed to function in diverse physiological processes including disease resistance and wound response, but predicted low substrate specificities and the presence of 70 or more isoforms have made it difficult to define a specific physiological function(s) for each gene. To select pathogen-responsive POX genes, we analyzed the expression profiles of 22 rice POX genes after infection with rice blast fungus. The expression of 10 POX genes among the 22 genes was induced after fungal inoculation in both compatible and incompatible hosts. Seven of the 10 POX genes were expressed at higher levels in the incompatible host than in the compatible host 6-24 h after inoculation by which time no fungus-induced lesions have appeared. Organ-specific expression and stress-induced expression by wounding and treatment with probenazole, an agrichemical against blast fungus, jasmonic acid, salicylic acid and 1-aminocyclopropane-1-carboxylate, a precursor of ethylene, indicated that rice POXs have individual characteristics and can be classified into several types. A comparison of the amino acid sequences of POXs showed that multiple isoforms with a high sequence similarity respond to stress in different or similar ways. Such redundant responses of POX genes may guarantee POX activities that are necessary for self-defense in plant tissues against environmental stresses including pathogen infection.

Amino Acids, Cyclic↗
PubMed2004

Recurrence of cervical carcinoma manifesting as cardiac metastasis three years after curative resection.

We report a rare case of cardiac metastasis from carcinoma of the uterine cervix. A 58-year-old woman presented with multiple pulmonary emboli, disseminated intravascular coagulation, and right heart failure 43 months after a curative resection of cervical carcinoma (stage IB1). Transthoracic echocardiography and computed tomography revealed large tumors in the right ventricle and right main pulmonary artery. No evidence of recurrence was obtained in the pelvis and abdomen. Surgical removal of the tumors remarkably improved her general condition, which had been declining progressively. The patient declined further treatment, including adjuvant chemotherapy, and was followed in the outpatient clinic. The right ventricular tumor recurred 4 months later and she died of heart failure. The possibility of late recurrence of cervical carcinoma in the heart should be considered even after curative resection.

Female↗
PubMed2004

Prognostic impact of survivin, cyclin D1, integrin beta1, and VEGF in patients with small adenocarcinoma of stage I lung cancer.

The purpose of this study was to investigate the impact of survivin, cyclin D1, integrin beta1, and vascular endothelial growth factor (VEGF) in tumor on survival of patients with small adenocarcinoma of the lung. Seventy-two patients with pathologic stage I resected tumors <2 cm in diameter were entered into the study. Each patient underwent curative surgical resection for lung cancer between July 1992 and November 1999. The resected tumors were subjected to immunostaining for each gene. Thirty-five, 26, 6, and 16 patients had tumors with >10% survivin-, >20% cyclin D1-, >10% integrin beta1-, and >10% VEGF-positive cells, respectively. When the survival of 72 patients was compared according to each gene expression, the overall survival of patients with positive expression of survivin, cyclin D1, and integrin [beta]1 was significantly worse than that of individuals whose tumors had negative expression of each gene. By multivariate analysis controlling for each gene expression, no gene expression was an independent marker of poor prognosis, however, the overall survival of the complex gene expression (2 or more gene-positive) group (n = 35) was significantly worse than that of 0 or 1 gene-positive group (n = 37; log-rank test, P = 0.0011; Wilcoxon test, P = 0.0011). When the association between survival and pathologic factors, including lymphatic invasion, venous invasion, type of bronchioalveolar carcinoma, and complex gene positive expression was analyzed, only complex gene-positive expression was found to be a significant independent factor (hazard ratio = 0.085, P = 0.0299). It can be concluded that multiple increased expression of oncogene is a poor prognostic factor in patients with small adenocarcinoma of the lung.

Adenocarcinoma↗
PubMed2004

Cloning of a gene cluster responsible for the biosynthesis of diterpene aphidicolin, a specific inhibitor of DNA polymerase alpha.

The fungal diterpene, aphidicolin, is a well-known specific inhibitor of DNA polymerase alpha. Terpenoids are an important class of natural products. However, identification of the biosynthetic gene cluster in terpenoids is relatively rare compared with another important class of natural products, polyketides. To explore a reliable identification method for the biosynthetic gene cluster in fungal diterpenoids, cloning of the biosynthetic gene cluster of aphidicolin was employed. The application of a simple PCR method for genome walking based on the sequence of cDNA encoding aphidicolan-16beta-ol synthase (ACS) allowed us to analyze a 15.6-kb region of the Phoma betae genomic DNA. Six ORFs, PbGGS, ACS, PbP450-1, PbP450-2, PbTP, and PbTF were found in this region, and respectively expected to encode geranylgeranyl diphosphate synthase, diterpene synthase, two cytochrome P-450s, the transporter and transcription factor. Their amino acid sequences and introns were deduced by a corresponding cDNA analysis. This study shows that simple PCR-based genome walking without constructing a genomic DNA library is useful for identification of a small gene cluster. We propose a general strategy for the cloning the biosynthetic genes of fungal diterpenoids by using fungal GGS.

Alkyl and Aryl Transferases↗
PubMed2004

Characterization of starch synthase I and II expressed in early developing seeds of kidney bean (Phaseolus vulgaris L.).

Plant starch synthase (SS) contributes to the elongation of glucan chains during starch biosynthesis and hence plays an essential role in determining the fine structure of amylopectin. To elucidate the role of SS activity in the formation of amylopectin in kidney bean (Phaseolus vulgaris L.), a study was undertaken to isolate cDNA clones for SS and to characterize the enzymatic properties of the coded recombinant enzymes. Two SS cDNAs, designated pvss1 and pvss21, which were isolated from early developing seeds, encoded SSI and SSII (designated PvSSI and PvSSII-1) that displayed significant identity (more than 65%) with other SSI and SSII members, respectively. RNA gel blot analysis indicated that both transcripts accumulate in leaves and developing seeds at the early stage. Immunoblot analysis with antisera raised against both recombinant proteins (rPvSSI and rPvSSII-1) showed that the accumulation of both proteins parallels the gene expression profiles, although both were detectable only in starch-granule fractions. Recombinant enzymes expressed by Escherichia coli cells showed distinct chain-length specificities for the extension of glucan chains. Our results suggest that these SS isozymes for synthesis of transitory starch are also responsible for synthesis of storage starch in early developing seeds of kidney bean.

Amino Acid Sequence↗
PubMed2004

Audiovisual integration: an investigation of the "streaming-bouncing" phenomenon.

Temporal aspects of the perceptual integration of audiovisual information were investigated by utilizing the visual "streaming-bouncing" phenomenon. When two identical visual objects move towards each other, coincide, and then move away from each other, the objects can either be seen as streaming past one another or bouncing off each other. Although the streaming percept is dominant, the bouncing percept can be induced by presenting an auditory stimulus during the visual coincidence of the moving objects. Here we show that the bounce-inducing effect of the auditory stimulus is paramount when its onset and offset occur in temporal proximity of the onset and offset of the period of visual coincidence of the moving objects. When the duration of the auditory stimulus exceeded this period, visual bouncing disappears. Implications for a temporal window of audiovisual integration and the design of effective audiovisual warning signals are discussed.

Acoustic Stimulation↗
PubMed2004

Controlling visually induced self-motion perception: effect of overlapping dynamic visual noise.

The effect of overlapping dynamic visual noise on visually induced self-motion perception (vection) by upward or downward optical flow was tested. The dynamic visual noise consisted of rapidly refreshed sparse random dots. Binocular disparity of the overlapping noise plane was varied. The results showed that when the noise was presented on the flow plane or on a plane farther than the flow plane, vection was totally impaired. This demonstrates that dynamic visual noise is functionally equivalent to static patterns in the vection suppression effect. A possibility of dynamic visual noise as a vection suppressor in an application on a 3-D display is discussed in relation to simulator sickness.

Humans↗
PubMed2004

[Clinical characteristics of 16 patients suspected preclinical Cushing's syndrome].

PURPOSE: In 1996, Japanese guidelines for the diagnosis of preclinical adrenal Cushing's syndrome were proposed. However, several patients with preclinical Cushing's syndrome (PCS) didn't clearly show that these diagnostic guidelines were universally applicable. The aim of the present study was to evaluate the validity of these diagnostic guidelines on the basis of our clinical experience. PATIENTS AND METHODS: We performed adrenalectomy for adrenal incidentaloma in 16 patients with suspected PCS at our university hospital from 1990 through 2002. Eight patients met the Japanese criteria for the diagnosis of PCS (PC group) and 8 did not (dexamethasone [DXM] suppression group). Clinical characteristics and pathology profiles were compared between the groups. RESULTS: No patients in the DXM suppression group showed responses of serum cortisol levels on a 1-mg overnight dexamethasone suppression test. Twenty-four-hour urinary levels of 17-hydroxycorticosteroids were significantly higher in the PC group than in the DXM suppression group. In all patients of both groups, adrenal scintigraphy showed marked accumulation of radioisotope in the adhesive, atrophic adrenal cortex. One patient of the DXM suppression group had severe adrenal symptoms after adrenalectomy. Several patients in the DMX suppression group showed clinical improvement after adrenalectomy, as well as did several patients in the PC group. CONCLUSION: Endocrine activity may have been higher in the PC group than in the DXM suppression group. However, because patients who failed a 1-mg DXM suppression test may in fact have autonomous cortisol secretion, adrenalectomy may still be indicated. Autonomous cortisol secretion might not be documented with the 1-mg overnight DXM suppression test; therefore, the results must be interpreted carefully.

Adrenocorticotropic Hormone↗
PubMed2004

Extracellular potassium dependent negative dromotropic action of nicorandil in guinea pig myocardium.

Although the antiarrhythmic action of nicorandil is drawing an increasing attention, dromotropic effect of this agent is unclear. Therefore, this was investigated by microelectrode technique to the superfused guinea pig papillary muscle to record the action potential and extracellular potential during conduction. The correlation of myocardial internal longitudinal resistance (r1) assumed to reflect the global gap junctional resistance, maximum rate of rise of the action potential upstroke (Vmax), and conduction velocity was examined under the alterations of external potassium concentrations ([K+]e; ranging from 3.0 to 12.0 mM) in the presence or absence of 100 microM nicorandil. In the minimum [K+]e, nicorandil caused significant (p < 0.05) hyperpolarization and reduction in Vmax. Negative dromotropic action of nicorandil was slight but significant (p < 0.05) in low (3.0 mM) [K+]e but was not evident in physiologic (5.4 mM) or elevated (9.0 to 12.0 mM)[K+]e. In conclusion, nicorandil exerts negative dromotropic action as [K+]e decreased, which was accounted for by the cable analysis and may contribute to the prevention of low [K+]e-induced arrhythmia.

Animals↗
PubMed2003

New thiazole derivatives as potent and selective 5-hydroxytriptamine 3 (5-HT3) receptor agonists for the treatment of constipation.

The syntheses and biological evaluation of a series of novel indeno[1,2-d]thiazole derivatives are described. Several groups reported 5-HT(3) receptor agonists which were mainly evaluated for their activities on the von Bezold-Jarisch reflex (B-J reflex). We discovered that tetrahydrothiazolopyridine derivative 1b had a contractile effect on the isolated guinea pig colon with weak B-J reflex. Our efforts to find a new type of 5-HT(3) receptor agonists on the isolated guinea pig colon focused on the synthesis of a fused thiazole derivative 1d modified from 1b and reverse-fused thiazole derivatives (7-10). In this series, 10f (YM-31636) showed high affinity and selectivity for the cloned human 5-HT(3) receptor; furthermore, it showed potent and selective 5-HT(3) receptor agonistic activity. YM-31636 was examined for its effects on defecation in animals, thus evaluating the compound as an agent against constipation.

Animals↗
PubMed2003

Changes in catecholamine metabolism by ascorbic acid deficiency in spontaneously hypertensive rats unable to synthesize ascorbic acid.

We have previously reported the establishment of a novel rat strain, SHR-od, with both spontaneous hypertension and a defect of ascorbic acid biosynthesis. Blood pressure in mature SHR-od fed an ascorbic acid-supplemented diet is over 190-200 mmHg, while it decreased to around 120 mmHg at 4-5 weeks after the cessation of ascorbic acid supplementation. With regard to possible mechanisms of blood pressure lowering, we focused on catecholamine synthesis in adrenal glands, since catecholamine is a major factor for blood pressure regulation and ascorbic acid is a co-factor of dopamine beta-hydroxylase (DBH) in catecholamine biosynthesis. Male SHR-od (25-week-old) and normotensive ODS rats with a defect in ascorbic acid biosynthesis (25-week-old) were fed a Funabashi-SP diet with or without ascorbic acid (300 mg/kg diet) for 28 days or 35 days. In SHR-od, systolic blood pressure (191 +/- 6 mmHg) began to decrease from day 21 in the ascorbic acid-deficient group, whereas no significant difference was found in ODS rats. In spite of significant lowering of blood pressure, no significant differences were found in catecholamine levels in serum, adrenal glands and brain on day 28. On day 35, however, urinary excretion of norepinephrine and epinephrine in the ascorbic acid-deficient SHR-od were higher at 490% (P < 0.05) and 460% (P < 0.05) of the respective control. Serum catecholamine concentrations and the adrenal catecholamine content tended to be higher in the ascorbic acid-deficient SHR-od than the control of SHR-od and reached to similar level in ODS rats. The administration of ascorbic acid (intraperitoneal injection, 60 mg ascorbic acid/kg body weight, once a day) to the ascorbic acid-deficient SHR-od restored blood pressure to the range 180-190 mmHg within two days. These findings indicate that ascorbic acid deficiency affects catecholamine metabolism in the adrenal glands of SHR-od in response to blood pressure lowering, suggesting catecholamines are not involved in the mechanism for the remarkable reduction in blood pressure in response to ascorbic acid deficiency.

Adrenal Glands↗
PubMed2003

Structure and physicochemical properties of starches from kidney bean seeds at immature, premature and mature stages of development.

Starches from kidney bean (Phaseolus vulgaris L. cv. Toramame) seeds at the immature, premature, mature stages of development were examined. The starch content increased from 94, 219 to 265 mg per seed. Starches showed the C(a)-crystalline type composed of small (<5 micrometer) and large (10-35 micrometer) granules, with the large granules largely increasing with maturity. The amylose content increased from 21, 26 to 27%, and rapid viscograms and DSC thermograms suggested that the mature-stage starch was gelatinized with ease. The amylose increased in size from DPn 820, 1000 to 1080 and a number of chains per molecule (NC) from 3.3, 4.2 to 4.5. The branched amylose was a minor component (11-18% by mole) with NC 20-22. The amylopectin was similar in CL (23), beta-amylolysis limit (59%), and chain-length distribution, but reduced in size (DPn 17,100-5270) and increased in content of phosphorus (114-174 ppm) with an increase in the amount of phosphorus linked to C-6 of the glucose residue (8-66%).

Microscopy, Electron, Scanning↗
PubMed2003

Modulation of type I IL-1 receptor and IL-1 beta mRNA expression followed by endotoxin treatment in the corticotropin-releasing hormone-deficient mouse.

In an attempt to define the possible role of corticotropin-releasing hormone (CRH) on lipopolysaccharide (LPS)-induced type I interleukin-1 receptor (IL-1R1), IL-1alpha, and IL-1beta mRNAs in the pituitary, adrenal gland and spleen, we used CRH-deficient (knockout, KO) mouse in this study. LPS administration resulted in a robust increase in IL-1R1 mRNA levels in the pituitary, adrenal gland and spleen of wild-type (WT) and CRH KO mice, but this elevation was attenuated in the pituitary and adrenal gland of CRH KO mice. CRH deficiency did not affect LPS administration induced increase of IL-1alpha mRNA as well as IL-1beta mRNA in the pituitary and adrenal gland. Lack of CRH attenuated LPS administration induced increase of IL-1beta mRNA expression in the spleen. These data demonstrate the pivotal and organ-specific modulation of CRH for IL-1 and IL-1R1 mRNAs following endotoxin treatment.

Adrenal Glands↗