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Biomedical subjects

H Yamaguchi

Publications and source records attributed to H Yamaguchi.

At least 343 records · Page 19Linked to original sources
PubMed1999

Topological and functional characterization of the N-glycans of soybean (Glycine max) agglutinin.

Soybean agglutinin (SBA), is a noncovalently bound tetramer comprised of four identical subunits having a single N-glycan chain, Man9GlcNAc2, that is known to be essential for regeneration of the functional tetrameric structure from unfolded subunits. In this study, SBA was found to have strong affinity for concanavalin A, indicating that the N-glycans are extensively solvent-exposed. The susceptibilities of the N-glycans to alpha-mannosidase and endo-beta-N-acetylglucosaminidase revealed that their distal areas have nonreducing ends embedded among the subunits, whereas their proximal regions are solvent-exposed. Endo-beta-N-acetylglucosaminidase-digested SBA was unable to retain its conformation and gradually unfolded. Periodate-oxidized SBA, whose N-glycans closely correspond to the invariant pentasaccharide core, tended to dissociate into the subunits, but permitted to stay as folded monomers. This SBA species was capable of refolding from unfolded subunits but unable to form the functional tetramer. It seems probable that the proximal regions of the N-glycans function in the formation and stabilization of the subunit conformation, whereas the branches outside the invariant cores stabilize the tetrameric structure.

Carbohydrate Conformation↗
PubMed1999

Binding affinity of N-glycans for aromatic amino acid residues: implications for novel interactions between N-glycans and proteins.

This study advances direct evidence of the binding affinity of N-glycans for aromatic amino acid residues. The intrinsic fluorescence intensities of bovine pancreatic RNase A, bovine alpha-lactalbumin, and aromatic amino acids were markedly depressed in solutions (1 mM or so) of free N-glycans of both the high-mannose and complex types. In addition, free N-glycans inhibited the chemical modifications of the solvent-exposed tyrosine and tryptophan residues of these proteins, confirming the affinity of N-glycans for aromatic amino acid residues. The results are discussed in connection with the roles of N-glycans in novel interactions between N-glycans and proteins.

Amino Acids↗
PubMed1999

Identification of essential amino acid residues of an alpha-amylase inhibitor from Phaseolus vulgaris white kidney beans.

Kidney bean (Phaseolus vulgaris) alpha-amylase inhibitors, which are bivalent inhibitors with the subunit stoichiometry of (alphabeta)(2) complex, have been inferred to contain unique arginine, tryptophan, and tyrosine residues essential for the inhibitory activity. To test the validity of this inference, an attempt was made to identify the essential amino acid residues of a white kidney bean (P. vulgaris) alpha-amylase inhibitor (PHA-I) by using the chemical modification technique combined with amino acid sequencing and mass spectrometry. Exhaustive modification of the arginine residues by phenylglyoxal did not lead to a marked loss of activity, suggesting that no arginine residue is directly associated with the inhibitory activity. N-Bromosuccinimide treatment of PHA-I in the presence or absence of a substrate alpha-amylase revealed the involvement of two tryptophan residues in alpha-amylase inhibition, and they were identified as Trp188 of the beta-subunit by amino acid sequencing and mass spectrometry of lysylendopeptidase peptides. Further, two tyrosine residues were preferentially modified either by N-acetylimidazole or by tetranitromethane, resulting in a concomitant loss of most of the PHA-I activity. Amino acid sequencing of the lysylendopeptidase peptides from a tetranitromethane-modified PHA-I identified Tyr186 of the beta-subunit as an essential residue.

Amino Acid Sequence↗
PubMed1999

Development of hepatocellular carcinoma in a patient with chronic hepatitis C after 6 years of a sustained and complete response to IFN-alpha.

The authors report a rare case of hepatocellular carcinoma (HCC) that developed 6 years after a sustained and complete response to interferon (IFN) therapy for chronic hepatitis C. A 61-year-old Japanese man presented with a mass in the liver that was diagnosed as HCC. Six years earlier he was treated with IFN-alpha and responded successfully to therapy, with sustained normalization of serum aminotransferases and eradication of serum hepatitis C virus (HCV)-ribonucleic acid (RNA). HCV-RNA was also not detected in the resected tumorous and nontumorous liver tissues. The findings suggest that all patients with chronic HCV infection should be followed closely for as long as possible for the potential development of HCC even after a complete and sustained response to IFN treatment.

Carcinoma, Hepatocellular↗
PubMed1999

Monoclonal antibody to human midkine reveals increased midkine expression in human brain tumors.

We produced a rat IgG2a monoclonal antibody against the carboxyl terminal region of human midkine (MK), a novel growth factor. This monoclonal antibody was used in immunohistochemical studies to compare the expression of MK, proliferating cell nuclear antigen (PCNA) and p53 protein in 133 primary brain tumors and 21 carcinoma metastases to the central nervous system. Approximately half of the glioblastomas multiforme (GBMs) (19/32), medulloblastomas (8/14), primitive neuroectodermal tumors (PNETs) (5/11), breast carcinoma metastases (Br-Mts) (6/10) and lung carcinoma metastases (L-Mts) (5/11) as well as some astrocytomas (2/14) had tumor cells that expressed MK; however, oligodendrogliomas, ependymomas, schwannomas, meningiomas, and pituitary adenomas did not express MK. The values of the PCNA-labeling index were statistically higher in GBMs, medulloblastomas, PNETs, Br-Mts, and L-Mts that expressed MK than in those that did not (Wilcoxon rank-sum test, p < 0.05). There was no correlation between MK and p53 protein in all tumor types. Normal and non-neoplastic brain tissues were negative for MK, PCNA, and p53 protein. We conclude that primary and metastatic tumors of the brain express MK and that the MK expression in brain tumors may depend, in part, on the proliferating potential.

Animals↗
PubMed1999

Hepatocyte growth factor and fibroblast growth factor 2 are overexpressed after cerulein-induced acute pancreatitis.

The regenerative process after acute inflammation of the pancreas is characterized by cell proliferation as well as synthesis and transient deposition of extracellular matrix. Although the regulation of these processes is still unknown, there is growing evidence that the coordinated activity of various growth factors plays an important role in regeneration. Cerulein-induced pancreatitis in the rat was used to analyze whether growth factors and their receptor concentrations are changed in the acute pancreatitis. Messenger RNA hybridization revealed an individual expression pattern for each analyzed growth factor. The mRNA levels of platelet-derived growth factor B (PDGF B), epidermal growth factor (EGF), and insulin-like growth factor 2 (IGF-2) were not altered, whereas fibroblast growth factor-1 (FGF-1) and 2, IGF-1, transforming growth factor-alpha (TGFalpha), and hepatocyte growth factor (HGF) showed markedly increased concentrations with different expression maxima and duration compared with mRNA levels in healthy pancreata. The FGF-2 and IGF-1 expressions were increased between 1 and 3 days after induction of pancreatitis with maxima at day 2. HGF and FGF-1 mRNAs were upregulated between days 3 and 5. In contrast, TGFalpha exhibited the most prolonged overexpression. In the corresponding receptors, only c-met, the HGF-binding protein, showed higher mRNA and protein levels, whereas the expression of the other receptors did not change. Furthermore, in cultured pancreatic epithelial cells, HGF stimulated the expression of its own receptor in an autocrine manner. These results point out that the highly coordinated process of regeneration after pancreatitis may be influenced by a sequential induction and expression of peptide growth factors and their receptors.

Acute Disease↗
PubMed1999

Cloning of nicotianamine synthase genes, novel genes involved in the biosynthesis of phytosiderophores.

Nicotianamine synthase (NAS), the key enzyme in the biosynthetic pathway for the mugineic acid family of phytosiderophores, catalyzes the trimerization of S-adenosylmethionine to form one molecule of nicotianamine. We purified NAS protein and isolated the genes nas1, nas2, nas3, nas4, nas5-1, nas5-2, and nas6, which encode NAS and NAS-like proteins from Fe-deficient barley (Hordeum vulgare L. cv Ehimehadaka no. 1) roots. Escherichia coli expressing nas1 showed NAS activity, confirming that this gene encodes a functional NAS. Expression of nas genes as determined by northern-blot analysis was induced by Fe deficiency and was root specific. The NAS genes form a multigene family in the barley and rice genomes.

Alkyl and Aryl Transferases↗
PubMed1999

Cloning two genes for nicotianamine aminotransferase, a critical enzyme in iron acquisition (Strategy II) in graminaceous plants.

Nicotianamine aminotransferase (NAAT), the key enzyme involved in the biosynthesis of mugineic acid family phytosiderophores (MAs), catalyzes the amino transfer of nicotianamine (NA). MAs are found only in graminaceous plants, although NA has been detected in every plant so far investigated. Therefore, this amino transfer reaction is the first step in the unique biosynthesis of MAs that has evolved in graminaceous plants. NAAT activity is dramatically induced by Fe deficiency and suppressed by Fe resupply. Based on the protein sequence of NAAT purified from Fe-deficient barley (Hordeum vulgare) roots, two distinct cDNA clones encoding NAAT, naat-A and naat-B, were identified. Their deduced amino acid sequences were homologous to several aminotransferases, and shared consensus sequences for the pyridoxal phosphate-binding site lysine residue and its surrounding residues. The expression of both naat-A and naat-B is increased in Fe-deficient barley roots, while naat-B has a low level of constitutive expression in Fe-sufficient barley roots. No detectable mRNA from either naat-A or naat-B was present in the leaves of either Fe-deficient or Fe-sufficient barley. One genomic clone with a tandem array of naat-B and naat-A in this order was identified. naat-B and naat-A each have six introns at the same locations. The isolation of NAAT genes will pave the way to understanding the mechanism of the response to Fe in graminaceous plants, and may lead to the development of cultivars tolerant to Fe deficiency that can grow in calcareous soils.

Amino Acid Sequence↗
PubMed1999

Effective inhibition of Candida albicans growth by the combination of murine peritoneal neutrophils and activated macrophages.

The effect of leukocytes on the anti-Candida activity of neutrophils was examined. Murine neutrophils which were purified from casein-induced peritoneal cells inhibited the mycelial growth of Candida albicans. This anti-Candida activity of neutrophils was augmented by the addition of spleen cells prepared from mice pretreated with bacterial lipopolysaccharide 3 hr before, but not from non-treated mice. The population in the spleen cells, which enhanced the anti-Candida activity of neutrophils, was plastic-plate adherent, nylon-fiber columns adherent and anti-Mac-1 antigen-positive. These immunological profiles suggested that the enhancing cells are classified to splenic macrophages. Peritoneal-exudated macrophages from mice treated with lipopolysaccharide also augmented the anti-Candida activity of neutrophils. These results suggest that the anti-Candida activity of neutrophils may be upregulated by activated macrophages.

Animals↗
PubMed1999

Runaway pacemaker caused by a stuck accelerometer.

We report a case of runaway pacemaker with a ventricular pacing rate of 190 beats/min. The runaway occurred when the accelerometer became stuck due to the magnet application during VVIR pacing. Runaways in modern pacemakers are particularly rare, but they do still occur. The best solution for this phenomenon is generator replacement.

Electrocardiography↗
PubMed1999

Conservation and diversification of MHC class I and its related molecules in vertebrates.

The elucidation of the complete peptide-binding domains of the highly polymorphic shark MHC class I genes offered us an opportunity to examine the characteristics of their predicted protein products in the light of the latest advance in the structural studies of the MHC class I molecules. The results suggest that the fundamental characteristics in the T-cell recognition of the MHC class I molecule/peptide complex are expected to have been established at the early stage of the vertebrate evolution. The elucidation of the typical classical class I molecules from fishes and also of some MHC class I-related molecules may help us-to explore the common denominator of the ancient class I molecules.

Amino Acid Sequence↗
PubMed1999

[Antibacterial effects of cacao mass on enterohemorrhagic Escherichia coli O157:H7].

The antimicrobial activities of aqueous cacao mass extract against enterohemorrhagic Escherichia coli (EHEC) O157:H7 006 strain were studied. Hot water extract of cacao mass (cocoa extract) was shown to inhibit the growth of EHEC O157:H7 006 strain in PBS or CAYE medium. In addition, the production of verotoxins (types 1 and 2) of EHEC O157:H7 006 strain was significantly inhibited by 8.0% cocoa extract. The cocoa extract did not neutralize the cytotoxity of verotoxins, but had inhibitory effect on adhesion of verotoxins to the target Vero cells. These results demonstrate that cacao mass has antimicrobial effects on EHEC O157:H7.

Bacterial Toxins↗
PubMed1999

[Antagonistic interaction between Clostridium butyricum and enterohemorrhagic Escherichia coli O157:H7].

Antagonistic interaction between Clostridium butyricum strain MIYAIRI 588 and enterohemorrhagic Esherichia coli (EHEC) strain O157:H7 006 was examined using streptomycin-treated SPF mice and germ free mice. All SPF mice pretreated with streptomycin were colonized with EHEC O157:H7. On the other hand, only 20% of the SPF mice pretreated with streptomycin and C. butyricum were colonized with EHEC O157:H7. In addition, germ free mice died within 4-7 days after infection with EHEC O157:H7. In contrast, all gnotobiotic mice mono-associated with C. butyricum survived after the challenge with EHEC O157:H7. Both the number of EHEC and the amounts of shiga-like cytotoxin (SLT, type 1 and type 2) in fecal contents of gnotobiotic mice treated with C. butyricum were less than those of mice infected with only EHEC O157:H7. In conclusion, the probiotic bacterium, C. butyricum strain MIYAIRI 588, has a preventive effect against EHEC O157:H7 infection.

Animals↗
PubMed1999

Illegitimate recombination induced by overproduction of DnaB helicase in Escherichia coli.

Illegitimate recombination that usually takes place at a low frequency is greatly enhanced by treatment with DNA-damaging agents. It is thought that DNA double-strand breaks induced by this DNA damage are important for initiation of illegitimate recombination. Here we show that illegitimate recombination is enhanced by overexpression of the DnaB protein in Escherichia coli. The recombination enhanced by DnaB overexpression occurred between short regions of homology. We propose a model for the initiation of illegitimate recombination in which DnaB overexpression may excessively unwind DNA at replication forks and induce double-strand breaks, resulting in illegitimate recombination. The defect in RecQ has a synergistic effect on the increased illegitimate recombination in cells containing the overproduced DnaB protein, implying that DnaB works in the same pathway as RecQ does but that they work at different steps.

Bacterial Proteins↗
PubMed1999

Phylogenetic classification and species identification of dermatophyte strains based on DNA sequences of nuclear ribosomal internal transcribed spacer 1 regions.

The mutual phylogenetic relationships of dermatophytes of the genera Trichophyton, Microsporum, and Epidermophyton were demonstrated by using internal transcribed spacer 1 (ITS1) region ribosomal DNA sequences. Trichophyton spp. and Microsporum spp. form a cluster in the phylogenetic tree with Epidermophyton floccosum as an outgroup, and within this cluster, all Trichophyton spp. except Trichophyton terrestre form a nested cluster (100% bootstrap support). Members of dermatophytes in the cluster of Trichophyton spp. were classified into three groups with ITS1 homologies, with each of them being a monophyletic cluster (100% bootstrap support). The Arthroderma vanbreuseghemii-Arthroderma simii group consists of A. vanbreuseghemii, A. simii, Trichophyton mentagrophytes isolates from humans, T. mentagrophytes var. quinckeanum, Trichophyton tonsurans, and Trichophyton schoenleinii. Arthroderma benhamiae, T. mentagrophytes var. erinacei, and Trichophyton verrucosum are members of the Arthroderma benhamiae group. Trichophyton rubrum and Trichophyton violaceum form the T. rubrum group. This suggests that these "species" of dermatophytes have been overclassified. The ITS1 sequences of 11 clinical isolates were also determined to identify the species, and all strains were successfully identified by comparison of their base sequences with those in the ITS1 DNA sequence database.

Arthrodermataceae↗
PubMed1999

Giant aneurysm of the left main coronary artery in Takayasu aortitis.

Takayasu aortitis is a chronic inflammatory vasculitis characterised by stenosis or obliteration of large and medium sized arteries. Although coronary arteries are affected in approximately 10% of cases, most of the lesions are luminal narrowing, and coronary aneurysm formation is extremely rare. A case is described of giant aneurysm of the left main coronary artery complicated with Takayasu aortitis in a 46 year old Japanese woman who was followed until her death at age 71. Pronounced intimal proliferation and adventitial fibrous thickening of the involved arterial wall usually induce constriction or occlusion at the orifice of the main branch of the aorta in Takayasu aortitis. However, systemic hypertension, which resulted from renovascular stenoses in this case, is likely to have enlarged the vessel lumen before replacement of medial and adventitial fibrosis after extensive destruction of medial elastic fibres in the left main coronary artery. Moreover, associations such as autoimmune hepatitis, chronic thyroiditis, and Sjögren syndrome strongly suggests that Takayasu aortitis may be an autoimmune disease.

Aorta↗
PubMed1999

Lumped constant for deoxyglucose is decreased when myocardial glucose uptake is enhanced.

Quantification of myocardial glucose uptake by positron emission tomography with [18F]fluorodeoxyglucose (FDG) requires the "lumped constant" (LC), which corrects the difference of affinity between glucose and FDG to glucose transporters and phosphorylating system. Since LC was introduced, it has been considered to be constant. However, this has recently been questioned. To elucidate the constancy of LC by other than radioisotope techniques, the accumulation rate of sugar phosphates (d[SP]/dt) was measured in isolated, perfused rat hearts by 31P NMR spectroscopy with 2-deoxyglucose (DG). We postulate alpha as the affinity of DG to transporters and the phosphorylating system relative to that of glucose. Theoretically, alpha is equivalent to LC. We determined alpha by measuring d[SP]/dt at DG concentration ([DG]) = 10, 7, 5, and 3 mmol/l, keeping the total of glucose concentration ([glucose]) and [DG] to 10 mmol/l. When the glucose uptake was enhanced by insulin (10 mU/ml) or stunning, calculated alpha was reduced (insulin stimulated, 0.15; stunning, 0.19) compared with the control (0.59). These results indicate that LC can be evaluated by methods without radiolabeled tracers and is smaller when glucose uptake is augmented.

Animals↗