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Hiroki Ito

Publications and source records attributed to Hiroki Ito.

At least 19 recordsLinked to original sources
PubMed2007

Structural assignment of disialylated biantennary N-glycan isomers derivatized with 2-aminopyridine using negative-ion multistage tandem mass spectral matching.

To investigate the possibility of structural assignment based on negative-ion multistage tandem mass (MS(n)) spectral matching, four isomers of disialylated biantennary N-glycans (alpha2-6 and/or alpha2-3 linked sialic acid on alpha1-6 and alpha1-3 antennae) derivatized with 2-aminopyridine (PA) were analyzed by employing high-performance liquid chromatography/electrospray ionization linear ion trap time-of-flight mass spectrometry (HPLC/ESI-LIT-TOFMS), which uses helium gas for ion trapping and collision-induced dissociation (CID). It is shown that the MS(2) spectra derived from each precursor ion [M-2H](2-) are reproducible and useful for distinguishing the four isomers. Thus, they can be assigned by negative-ion MS(2) spectral matching based on correlation coefficients. In addition, MS(3) spectra derived from D-type fragment ions clearly differentiate the alpha2-3- or alpha2-6-linked sialic acid on the alpha1-6 antenna due to their characteristic spectral patterns. The C(4)-type fragment ions, which are produced from both the alpha1-6 and alpha1-3 antennae, show the characteristic MS(3) spectra reflecting alpha2-3- or alpha2-6- linkage type or a mixture of both types. Thus, the differentiation and assignment of these disialylated biantennary N-glycan isomers can also be supported with the MS(3) spectra of C(4)- and D-type ions.

Aminopyridines↗
PubMed2006

Altered venous capacitance as a cause of postprandial hypotension in multiple system atrophy.

Patients with multiple system atrophy (MSA) often have clinically significant postprandial hypotension (PPH). To elucidate the cause of insufficient cardiac preload augmentation that underlies PPH, we recorded calf venous capacitance (CVC) by strain-gauge plethysmography, in 17 MSA patients and eight healthy controls before and after oral glucose ingestion. Among 17 MSA patients, nine who showed a decrease in systolic blood pressure exceeding 20 mmHg and were diagnosed with PPH. MSA patients without PPH showed a significant decrease in CVC and a significant increase in cardiac output after oral glucose ingestion, as did controls; those with MSA exhibiting PPH showed a significant increase in CVC and no significant change in cardiac output. The change in CVC correlated positively with the decrease in systolic and diastolic blood pressure after glucose ingestion, and also correlated negatively with the increase in cardiac output. Physiologically, PPH is prevented by a decrease in venous capacitance, which increases circulating blood volume and cardiac output. In some MSA patients, failure of venous capacitance to decrease may induce PPH.

Aged↗
PubMed2006

Insulin responses to selective arterial calcium infusion under hyperinsulinemic euglycemic glucose clamps: case studies in adult nesidioblastosis and childhood insulinoma.

Selective arterial calcium stimulation and hepatic venous sampling (ASVS) for insulin secretion is used as a diagnostic procedure in patients with insulinomas or adult nesidioblastosis. In some of those patients, severe hypoglycemia requiring urgent glucose administration occurs during the procedure. Such glucose administration, however, may affect the results and damage the validity of the test. We report two cases of hyperinsulinemic hypoglycemia, in which ASVS tests were successfully performed under hyperinsulinemic euglycemic glucose clamps. A 40-year-old male with nesidioblastosis developed continual severe hypoglycemia several years after a Billroth II-Braun gastrectomy, and continuous glucose infusion could not be stopped even during ASVS tests. A 9-year-old girl with an insulinoma that showed atypical hypovascularity on imaging examinations had ASVS tests under a glucose clamp for safety. Hyperinsulinemic (approximately 100 microU/ml) euglycemic (approximately 90 mg/dl) clamps were achieved by an artificial endocrine pancreas. The insulin analogue lispro was utilized for clamps and endogenous insulin was measured with an assay that does not cross-react with the analogue. Diagnostically significant responses (more than twofold) of insulin secretion were observed under hyperinsulinemic clamps in both cases. The use of the hyperinsulinemic glucose clamp technique during the ASVS test should be considered for maintaining the safety of some hypoglycemic patients.

Adult↗
PubMed2006

Separation of isomeric 2-aminopyridine derivatized N-glycans and N-glycopeptides of human serum immunoglobulin G by using a zwitterionic type of hydrophilic-interaction chromatography.

Isomeric oligosaccharides and isomeric glycopeptides are sometimes difficult to separate on normal-phase (NP) and reversed-phase (RP) columns. A zwitterionic type of hydrophilic-interaction chromatography column with sulfobetaine groups (called ZIC-HILIC column) was first applied to the separation of 2-aminopyridine derivatized (PA) N-glycans and tryptic peptides of human serum immunoglobulin G (IgG). It is shown that the ZIC-HILIC column has high capability for structural recognition of isomeric N-glycans as well as high selectivity for glycopeptides. The former feature (i.e., structural recognition) was proven by sufficient separation of neutral PA N-glycan isomers, which are usually difficult to separate on NP and RP columns. In addition, it is noteworthy that IgG glycopeptides consisting of isomeric N-glycans and the same peptide sequences can be sufficiently separated on a ZIC-HILIC column. The latter feature (i.e., selectivity) was also demonstrated by easily separating two peptide groups with/without N-glycans. Thus, we note that the ZIC-HILIC column is highly promising for a simple analysis of N-glycans and N-glycopeptide samples.

Aminopyridines↗
PubMed2006

Simple separation of isomeric sialylated N-glycopeptides by a zwitterionic type of hydrophilic interaction chromatography.

Asparagine-linked oligosaccharides (N-glycans) usually show structural heterogeneity, especially in proteins with sialylated N-glycans and, therefore, their structural analysis is still very difficult. A zwitterionic type of hydrophilic interaction chromatography column with sulfobetaine functional groups (called a ZIC-HILIC column) was applied to the separation of tryptic peptides of alpha-1-acid glycoprotein. It was demonstrated that the ZIC-HILIC separation column has a selectivity for sialylated N-glycopeptides and a high capability for separation based on the structural recognition of sialylated N-glycan isomers as well as for the previously reported neutral N-glycans and N-glycopeptides. The retention characteristics of neutral and sialylated N-glycans derivatized with 2-aminopyridine (PA N-glycans) demonstrate that the retentions of the N-glycans are based primarily on hydrophilic interaction with the water-rich liquid layer generated on the surface of the ZIC-HILIC column. In addition, the electrostatic repulsion interaction shielded with counter ions effectively tunes the separation and recognition of sialylated N-glycan isomers.

Aminopyridines↗
PubMed2006

Structural assignment of isomeric 2-aminopyridine-derivatized monosialylated biantennary N-linked oligosaccharides using negative-ion multistage tandem mass spectral matching.

To investigate the possibility of structural assignment based on negative-ion tandem multistage (MSn) mass spectral matching, four isomers of 2-aminopyridine (PA)-derivatized monosialylated oligosaccharides (i.e., complex-type N-glycans with an alpha2-3- or alpha2-6-linked sialic acid on alpha1-6 or alpha1-3 antennae) were analyzed using high-performance liquid chromatography/electrospray ion trap time-of-flight mass spectrometry (HPLC/ESI-IT-TOFMS). The negative ion [M-2H]2- is observed predominantly in the MS1 spectra without the loss of a sialic acid. The MS2 spectra derived from it are sufficiently reproducible that MS2 spectral matching based on correlation coefficients can be applied to the assignment of these isomers. The isomers containing a sialic acid on alpha1-6 or alpha1-3 antennae can be distinguished by MS2 spectral matching, but the alpha2-3 and alpha2-6 linkage types of sialic acid cannot be distinguished by their MS2 spectra. However, MS3 spectra derived from fragment ions containing a sialic acid (i.e., C4- and D-type ions) clearly differentiate the alpha2-3 and alpha2-6 linkage types of sialic acid in their MS3 spectral patterns. This difference might be rationalized in terms of a proton transfer from the reducing-end mannose to the negatively charged sialic acid. These two moieties are very close in the structural conformations of the precursor C4-type fragment ions of alpha2-6 linkage type, as predicted by molecular mechanics calculations. Thus, negative-ion MSn (n = 2, 3) spectral matching was demonstrated to be useful for the structural assignment of these four monosialylated PA N-glycan isomers.

Aminopyridines↗
PubMed2006

Complementary structural information of positive- and negative-ion MSn spectra of glycopeptides with neutral and sialylated N-glycans.

Positive- and negative-ion MSn spectra of chicken egg yolk glycopeptides binding a neutral and a sialylated N-glycan were acquired by using electrospray ionization linear ion trap time-of-flight mass spectrometry (ESI-LIT-TOFMS) and collision-induced dissociation (CID) with helium as collision gas. Several characteristic differences were observed between the positive- and negative-ion CID MSn (n = 2, 3) spectra. In the positive-ion MS2 spectra, the peptide moiety was presumably stable, but the neutral N-glycan moiety caused several B-type fragmentations and the sialylated N-glycan almost lost sialic acid(s). In contrast, in the negative-ion MS2 spectra, the peptide moiety caused several side-chain and N-glycan residue (e.g., N-acetylglucosamine (GlcNAc) residue) fragmentations in addition to backbone cleavages, but the N-glycan moieties were relatively stable. The positive-ion MS3 spectra derived from the protonated peptide ion containing a GlcNAc residue (203.1 Da) provided enough information to determine the peptide amino-acid sequence including the glycosylation site, while the negative-ion MS3 spectra derived from the deprotonated peptide containing a 0,2X1-type cross-ring cleavage (83.1 Da) complicated the peptide sequence analysis due to side-chain and 0,2X1 residue related fragmentations. However, for the structural information of the N-glycan moiety of the glycopeptides, the negative-ion CID MS3 spectra derived from the deprotonated 2,4A6-type cross-ring cleavage ion (neutral N-glycan) or the doubly deprotonated B6-type fragment ion (sialylated N-glycan) are more informative than are those of the corresponding positive-ion CID MS3 spectra. Thus, the positive-ion mode of CID is useful for the analyses of peptide amino-acid sequences including the glycosylation site. The negative-ion mode of CID is especially useful for sialylated N-glycan structural analysis. Therefore, in the structural analysis of N-glycopeptides, their roles are complementary.

Animals↗
PubMed2006

Direct structural assignment of neutral and sialylated N-glycans of glycopeptides using collision-induced dissociation MSn spectral matching.

Mass spectrometric analyses of various N-glycans binding to proteins and peptides are highly desirable for elucidating their biological roles. An approach based on collision-induced dissociation (CID) MS(n) spectra acquired by electrospray ionization linear ion trap time-of-flight mass spectrometry (ESI-LIT-TOFMS) in the positive- and negative-ion modes has been proposed as a direct method of assigning N-glycans without releasing them from N-glycopeptides. In the positive-ion mode of this approach, the MS(2) spectrum of N-glycopeptide was acquired so that a glycoside-bond cleavage occurs in the chitobiose residue (i.e., GlcNAcbeta1-4GlcNAc, GlcNAc: N-acetylglucosamine) attached to asparagine (N), and two charges on the [M+H+Na](2+) precursor ion are shared with both of the resulting fragments. These fragments are sodiated B(n)-type fragment ions of oligosaccharide (N-glycan) and a protonated peptide ion retaining one GlcNAc residue on the asparagine (N) residue. The structure of N-glycan was assigned by comparing MS(3) spectra derived from both the sodiated B(n)-type fragment ions of N-glycopeptide and the PA (2-aminopyridine) N-glycan standard (i.e., MS(n) spectral matching). In a similar manner, the structural assignment of sialylated N-glycan was performed by employing the negative-ion CID MS(n) spectra of deprotonated B(n)-type fragment ions of N-glycopeptide and the PA N-glycan standard. The efficacy of this approach was tested with chicken egg yolk glycopeptides with a neutral and a sialylated N-glycan, and human serum IgG glycopeptides with neutral N-glycan isomers. These results suggest that the approach based on MS(n) spectral matching is useful for the direct and simple structural assignment of neutral and sialylated N-glycans of glycopeptides.

Algorithms↗
PubMed2006

The prevalence and prognosis of a Brugada-type electrocardiogram in a population of middle-aged Japanese-American men with follow-up of three decades.

BACKGROUND: The Brugada syndrome is an inherited arrhythmogenic and nonstructural heart disease associated with an increased risk of sudden cardiac death from ventricular fibrillation. There are conflicting data about its prevalence and prognosis. Particularly, population-based studies are lacking in the United States and other countries. METHODS: A total of 8006 Japanese-American men aged 45 to 68 years participated in the initial examination of the Honolulu Heart Program during the period of 1965 through 1968. After excluding prevalent cases with coronary heart disease, 864 electrocardiograms coded as right bundle branch block were reviewed using the specified criteria for Brugada-type electrocardiogram. Baseline characteristics and the prognosis of Brugada-type electrocardiogram were compared with 5983 control subjects who had electrocardiograms coded as normal at the initial examination. RESULTS: There were 12 typical cases and 11 atypical cases of Brugada-type electrocardiogram at the initial examination (prevalence, 0.15% and 0.14%, respectively). Analysis of baseline characteristics revealed no difference between control cases and either typical or atypical Brugada-type electrocardiogram cases except significantly lower body mass index in subjects with Brugada-type electrocardiogram. During the 30-year follow-up period, none of the subjects died suddenly within 24 hours after the onset of symptoms. Survival analysis revealed no significant difference between case and control groups. CONCLUSIONS: Brugada-type electrocardiograms among middle-aged or elderly Japanese-American men are uncommon and are not associated with increased risk of either sudden death or total mortality.

Arrhythmias, Cardiac↗
PubMed2006

Reduction of muscle fatigue by catchlike-inducing intermittent electrical stimulation in rat skeletal muscle.

Catchlike property is the force enhancement produced when a brief, high-frequency burst of pulses is added to a constant low-frequency stimulation. In functional electrical stimulation, constant low-frequency stimulation of approximately 20 Hz has primarily been used to reduce muscle fatigue. The purpose of this study was to investigate the effects of catchlike-inducing intermittent stimulation on muscle fatigue in relation to continuous intermittent low-frequency stimulation. Twenty-two adult male Wistar ST rats were randomly assigned into the constant frequency stimulation (CFS) group or the catchlike-inducing stimulation (CIS) group. In the CFS group, constant low-frequency stimulation of 20 Hz was applied intermittently (4 seconds "ON"/15 seconds "OFF"). In the CIS group, a single electrical burst of 100 Hz was applied at the start of the every 4-second period of stimulation. The muscle fatigue test lasted for 16 min and isometric muscle force, muscle fatigue, and muscular workload were evaluated. CIS significantly increased the maximum muscular force (under fatigued condition) and workload, and significantly decreased muscle fatigue (p < 0.05). The results of this study suggest that catchlike-inducing intermittent electrical stimulation is useful in the clinical administration of functional electrical stimulation.

Animals↗
PubMed2005

Combinatorial synthesis of an oligosaccharide library by using beta-bromoglycoside-mediated iterative glycosylation of selenoglycosides: rapid expansion of molecular diversity with simple building blocks.

A new method for constructing an oligosaccharide library composed of structurally defined oligosaccharides is presented based on an iterative glycosylation of selenoglycosides. Treatment of 2-acyl-protected selenoglycosides with bromine selectively generates beta-bromoglycosides, which serve as glycosyl cation equivalents in the oligosaccharide synthesis. Thus, the coupling of the bromoglycosides with another selenoglycoside affords the corresponding glycosylated selenoglycosides, which can be directly used to next glycosylation. The iteration of this sequence allows the synthesis of a variety of oligosaccharides including an elicitor active heptasaccharide. A characteristic feature of the iterative glycosylation is that glycosyl donors and acceptors with the same anomeric reactivity can be selectively coupled by activation of the glycosyl donor prior to coupling with the glycosyl acceptor. Therefore, same selenoglycosides can be used for both the glycosyl donors and the acceptors. This feature has been exemplified by a construction of an oligosaccharide library directed to elicitor-active oligosaccharides. The library composed of stereochemically defined oligoglucosides with considerable structural diversity can be constructed starting from simple selenoglycosides.

Carbohydrate Sequence↗
PubMed2005

Acute annular outer retinopathy.

Acute annular outer retinopathy is an uncommon disorder of uncertain aetiology characterized by a unilateral visual field defect with an irregular annular band of grey-white, deep retinal opacification in a peripapillary location. Acute annular outer retinopathy is considered to be a variant of acute zonal occult outer retinopathy. The case is reported of acute annular outer retinopathy with spontaneous good visual recovery and no ophthalmoscopic sequelae.

Acute Disease↗
PubMed2005

Prevalence of venous thromboembolism at a teaching hospital in Okinawa, Japan.

Limited data suggest that Asian Americans may have a lower risk of venous thromboembolism (VTE) than Caucasians. However, the actual prevalence of VTE among Asians remains controversial, and has not been described in Japan. We studied all 131,060 patients hospitalized at a single medical centre in Japan (January 1987 - December 1999). Patients with VTE were identified through discharge diagnoses. Hospital records were reviewed for information on patient demographics, risk factors, and diagnostic modalities. VTE occurred in 0.11% of admissions (n=141, 95%CI 0.09-0.13%). Mean age (+/-SD) was 64+/-17 years, 70% were women, 91% had deep vein thrombosis, and 29% pulmonary embolism. Among hospitalized patients 50-69 years old, VTE was significantly more common among women than men (0.31% vs. 0.08%; OR 3.88; 95%CI 1.45-6.31). We found a low prevalence of VTE in Japan compared to that reported in the US. Future studies are needed to clarify the reasons for our findings.

Adult↗
PubMed2004

Increase of galanin-like immunoreactivity in rat hypothalamic arcuate neurons after peripheral nerve injury.

Galanin and galanin receptors are widely distributed within the central nervous system, and may play important roles in pain signaling and modulation. In the present study, we examined the galanin immunoreactivity (IR) in the hypothalamus and the amygdala following peripheral nerve injury. Four weeks after the operation, the ipsilateral mechanical threshold in the spared nerve injury (SNI) group (0.87 +/- 0.33 g) was significantly lower than that in the sham group (12.53 +/- 3.41 g; P < 0.05). In the SNI group, the number of galanin-IR neurons per section in the arcuate nucleus (Arc) of the hypothalamus was 10.2 +/- 1.7, significantly higher than that in the sham group (5.6 +/- 1.0; P < 0.05). These data suggest that the galanin-ergic neurons in the Arc may be involved in the functional modulation of descending pain modulation system following peripheral nerve injury.

Animals↗
PubMed2004

Nodular fasciitis of the finger.

Nodular fasciitis is a benign reactive lesion, often mistaken for a soft tissue sarcoma in clinical practice. Involvement of the finger is very rare and, as a result, in this location the lesion has sometimes been treated by ray amputation because of misdiagnosis. We report on the clinical and histological features of nodular fasciitis in a 30-year-old man who was treated by excisional biopsy. There has been no evidence of local recurrence at the recent follow-up 8 years after surgery. The importance of careful histological examination to avoid radical surgery should be emphasized because marginal excision can provide good results in the treatment of nodular fasciitis.

Adult↗
PubMed2004

Stoichiometric interactions between cyanobacterial clock proteins KaiA and KaiC.

We determined the stoichiometry of KaiA-KaiC interactions. Using immunoblotting and two-dimensional Native- and SDS-PAGE (2DNS-PAGE) analysis, we demonstrated that the reaction products of KaiA-KaiC interactions in the presence of ATP consisted of only phosphorylated KaiC whereas in the presence of the unhydrolyzable analogue 5'-adenylylimidodiphosphate (AMPPNP) they consisted of KaiA and KaiC. In the presence of ATP, the KE (molar ratio of KaiA dimer to KaiC hexamer giving half saturation in the enhancement of KaiC phosphorylation) was 0.25, and IAsys affinity biosensor analysis demonstrated that 1 molecule of KaiA dimer interacted with 1 molecule of KaiC hexamer. In the presence of AMPPNP, the ratio of KaiA dimer to KaiC hexamer in KaiA-KaiC complexes was determined to be 2 by 2DNS-PAGE, Native-PAGE/Scatchard plot, and IAsys analyses. These results suggest that 2 molecules of KaiA dimer can interact with 1 molecule of KaiC hexamer, and that interactions of at least 1 molecule of KaiA dimer with 1 molecule of KaiC hexamer are enough to enhance the phosphorylation of KaiC by KaiA at an almost saturated level.

Adenylyl Imidodiphosphate↗
PubMed2004

Oncogenic activation of c-Myb correlates with a loss of negative regulation by TIF1beta and Ski.

The c-myb proto-oncogene product (c-Myb) regulates proliferation of hematopoietic cells by inducing the transcription of a group of target genes. Removal or mutations of the negative regulatory domain (NRD) in the C-terminal half of c-Myb leads to increased transactivating capacity and oncogenic activation. Here we report that TIF1beta directly binds to the NRD and negatively regulates the c-Myb-dependent trans-activation. In addition, three corepressors (Ski, N-CoR, and mSin3A) bind to the DNA-binding domain of c-Myb together with TIF1beta and recruit the histone deacetylase complex to c-Myb. Furthermore, the Drosophila TIF1beta homolog, Bonus, negatively regulates Drosophila Myb activity. The Ski corepressor competes with the coactivator CBP for binding to c-Myb, indicating that the selection of coactivators and corepressors is a key event for c-Myb-dependent transcription. Mutations or deletion of the NRD of c-Myb and the mutations found in the DNA-binding domain of v-Myb decrease the interaction with these corepressors and weaken the corepressor-induced negative regulation of Myb activity. These observations have conceptual implications for understanding how the nuclear oncogene is activated.

Animals↗