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Biomedical subjects

H Nakamura

Publications and source records attributed to H Nakamura.

At least 163 records · Page 9Linked to original sources
PubMed2001

Role of Na(+)/H(+) exchanger in dilator responses of rat basilar artery in vivo.

We tested the hypothesis that activation of Na(+)/H(+) exchanger is involved in dilator responses of the basilar artery to endothelium-dependent vasodilators in vivo. Using a cranial window in anesthetized rats, we examined responses of the basilar artery to acetylcholine and bradykinin. Topical application of acetylcholine and bradykinin increased diameter of the basilar artery in a concentration-related manner. Because N(G)-nitro-L-arginine, an inhibitor of nitric oxide synthase, almost abolished vasodilator responses to acetylcholine and bradykinin, vasodilatation produced by the agonists appears to be mediated primarily by nitric oxide. 5-N,N-Hexamethyleneamiloride, an inhibitor of Na(+)/H(+) exchanger, did not affect baseline diameter of the basilar artery, but inhibited vasodilatation in response to acetylcholine and bradykinin, without affecting vasodilatation produced by sodium nitroprusside. FR183998, another inhibitor of Na(+)/H(+) exchanger, also attenuated acetylcholine-induced dilatation of the basilar artery without affecting vasodilatation in response to sodium nitroprusside. Monomethylamine hydrochloride, which produces intracellular alkalinization, enhanced acetylcholine-induced dilatation of the basilar artery in the presence of 5-N,N-hexamethyleneamiloride. These results suggest that intracellular alkalinization produced by activation of Na(+)/H(+) exchanger may enhance nitric oxide production in the basilar arterial endothelium and thereby contribute to dilator responses of the artery in vivo.

Acetylcholine↗
PubMed2001

Expression of HNK1 epitope by the cardiomyocytes of the early embryonic chick: in situ and in vitro studies.

Monoclonal antibody HNK1 reacts with a carbohydrate epitope in cell surface glycoproteins and glycolipids. During development, in various species the HNK1 epitopes are expressed in migrating neural crest cells and in the developing conduction cardiomyocytes. The conduction system is generally thought to be developed from cardiomyocytes, but some investigators have hypothesized that it is derived from the neural crest because conduction myocytes express neural antigens, including HNK1. Using immunohistochemistry, we examined the spatiotemporal expression of HNK1 in early chick cardiogenesis (stages 4 to 18) and whether cultured precardiac mesoderm does or does not express HNK1 as well as sarcomeric myosin (MF20). HNK1 was first expressed in the premyocardium at stage 8. At stage 10, HNK1-positive cardiomyocytes were scattered along the straight heart tube. By stage 18, HNK1-positive cardiomyocytes had become restricted to the atrium and sinus venosus. Atrioventricular cushion mesenchyme also expressed an HNK1 epitope. Immunostaining of HNK1 and MF20 in cultured precardiac mesoderm showed that there are at least three types of cells: 1) cardiomyocytes without HNK1 expression, 2) cells possessing both HNK1- and MF20-immunoreactivity, and 3) mesenchymal cells with HNK1. Immunogold electron microscopy showed that cardiomyocytes containing sparsely distributed myofibrils associated with the Z-band react with anti-HNK1 antibody. Our observations showed a direct evidence for the first time that the precardiac mesoderm generates HNK1-positive cardiomyocytes with morphological features similar to those of conduction cardiomyocytes.

Animals↗
PubMed2001

Correlation between 25-hydroxyvitamin D3 1 alpha-hydroxylase gene expression in alveolar macrophages and the activity of sarcoidosis.

PURPOSE: To demonstrate expression of the 25-hydroxyvitamin D3 1 alpha-hydroxylase (1 alpha-hydroxylase) gene in human alveolar macrophages and measure the correlations among the 1 alpha-hydroxylase mRNA level, the activity of sarcoidosis, and calcium metabolism. SUBJECTS AND METHODS: We examined 7 patients with sarcoidosis and 6 control patients with other pulmonary disorders who underwent bronchoalveolar lavage. Levels of 1 alpha-hydroxylase mRNA were measured by semiquantitative polymerase chain reaction amplification. We measured serum levels of calcium, ionized calcium, parathyroid hormone, calcitriol (1,25-dihydroxyvitamin D3), and 25-hydroxyvitamin D3 to evaluate calcium metabolism. To estimate the activity of sarcoidosis, we measured the cell count, the CD4/CD8 ratio in bronchoalveolar lavage cells, and the serum angiotensin-converting enzyme (ACE) activity. RESULTS: Expression of 1 alpha-hydroxylase was demonstrated in purified human alveolar macrophages. The 1 alpha-hydroxylase mRNA levels in bronchoalveolar lavage cells were fivefold higher in sarcoidosis patients than in control patients (10.8 +/- 3.6 vs. 2.2 +/- 1.4, P <0.003). Among all patients studied, there were significant correlations between the 1 alpha-hydroxylase mRNA level in bronchoalveolar lavage samples and the percentage of alveolar lymphocytes (r = 0.83, P <0.005), the CD4/CD8 ratio (r = 0.77, P <0.02), serum ACE level (r = 0.58, P <0.05), serum ionized calcium level (r = 0.58, P <0.05), and the calcitriol/25-hydroxyvitamin D3 ratio (r = 0.57, P <0.05). In the sarcoidosis patients, a significant correlation was also observed between 1 alpha-hydroxylase mRNA and the percentage of alveolar lymphocytes (r = 0.82, P <0.05). CONCLUSION: There is a correlation between 1 alpha-hydroxylase gene expression in alveolar macrophages with the activity of sarcoidosis and its associated disturbances in calcium metabolism.

Adult↗
PubMed2001

Inhibition of epidermal growth factor-induced RhoA translocation and invasion of human pancreatic cancer cells by 3-hydroxy-3-methylglutaryl-coenzyme a reductase inhibitors.

3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors prevent the conversion of HMG-CoA to mevalonate and thereby inhibit the synthesis of other products derived from this metabolite. This includes a number of small prenylated GTPases involved in cell growth, motility, and invasion. We studied the effect of HMG-CoA reductase inhibitors (fluvastatin and lovastatin) on in vitro invasion of human pancreatic cancer PANC-1 cells. Epidermal growth factor (EGF) induced a dose-dependent increase of PANC-1 cell invasion in a modified Boyden chamber assay. Stimulation of cancer cells with EGF induced translocation of RhoA from the cytosol to the membrane fraction and actin stress fiber assembly. Furthermore, Clostridium botulinum C3 transferase, a specific inhibitor of Rho, inhibited the ability of EGF to promote invasion, indicating that EGF-induced cancer cell invasion is regulated by Rho signaling. Treatment of PANC-1 cells with fluvastatin markedly attenuated EGF-induced translocation of RhoA from the cytosol to the membrane fraction and actin stress fiber assembly, whereas it did not inhibit the tyrosine phosphorylation of EGF receptor and c-erbB-2. The induction of cancer cell invasion by EGF was inhibited by the addition of fluvastatin or lovastatin in a dose-dependent manner. The effects of fluvastatin or lovastatin on cell morphology and invasion were reversed by the addition of all-trans-geranylgeraniol but not by the addition of all-trans-farnesol. These results suggest that HMG-CoA reductase inhibitors affect RhoA activation by preventing geranylgeranylation, which results in inhibition of EGF-induced invasiveness of human pancreatic cancer cells.

ADP Ribose Transferases↗
PubMed2001

Cytogenetic analysis and clinical significance in adult T-cell leukemia/lymphoma: a study of 50 cases from the human T-cell leukemia virus type-1 endemic area, Nagasaki.

Identification of cytogenetic abnormalities is an important clue for the elucidation of carcinogenesis. However, the cytogenetic and clinical significance of adult T-cell leukemia/lymphoma (ATLL) is still unclear. To address this point, cytogenetic findings in 50 cases of ATLL were correlated with clinical characteristics. Karyotypes showed a high degree of diversity and complexity. Aneuploidy and multiple breaks (at least 6) were observed frequently in acute and lymphoma subtypes of ATLL. Breakpoints tended to cluster at specific chromosomal regions, although characteristic cytogenetic subgroups of abnormalities were not found. Of these, aberrations of chromosomes 1p, 1q, 1q10-21, 10p, 10p13, 12q, 14q, and 14q32 correlated with one or more of the following clinical features: hepatosplenomegaly, elevated lactate dehydrogenase, hypercalcemia, and unusual immunophenotype, all indicators of clinical severity of ATLL. Multiple breaks (at least 6); abnormalities of chromosomes 1p, 1p22, 1q, 1q10-21, 2q, 3q, 3q10-12, 3q21, 14q, 14q32, and 17q; and partial loss of chromosomes 2q, 9p, 14p, 14q, and 17q regions correlated with shorter survival. These cytogenetic findings are relevant in predicting clinical outcome and provide useful information to identify chromosomal regions responsible for leukemogenesis. This study also indicates that one model of an oncogenic mechanism, activation of a proto-oncogene by translocation of a T-cell-receptor gene, may not be applicable to the main pathway of development of ATLL and that a multistep process of leukemogenesis is required for the development of ATLL. (Blood. 2001;97:3612-3620)

Adult↗
PubMed2001

A role of the third complementarity-determining region in the affinity maturation of an antibody.

We recently found that there are two distinct antibody maturation pathways for the immune response of C57BL/6 mice to (4-hydroxy-3-nitrophenyl) acetyl and that a junctional amino acid introduced at a point far in advance of somatic hypermutation determined which pathway of affinity maturation was used. We describe here the structural basis for this aspect of maturation using recently developed H3 rules, which allow for reliable identification of the conformation of the third complementarity-determining region of the heavy chain (CDR-H3) from the primary amino acid sequences only. By the application of these rules, the anti-(4-hydroxy-3-nitrophenyl) acetyl antibodies examined here were classified into two major groups on the basis of their CDR-H3 structure, and these groups were found to be consistent with the maturation pathways. In addition, circular dichroism measurements revealed that the versatile nature of the antigen binding of the antibodies was significantly influenced by the pathway employed. We postulated in this study that flexibility in the CDR-H3 structure in the antigen-combining site could facilitate efficient antibody maturation supported by a plurality of possible antigen binding modes.

Animals↗
PubMed2001

Effect of long-term administration of JTP-2942, a novel thyrotropin-releasing hormone analogue, on neurological outcome, local cerebral blood flow and glucose utilization in a rat focal cerebral ischemia.

The effect of JTP-2942, a novel thyrotropin-releasing hormone analogue on neurological examination, local cerebral blood flow (l-CBF) and local cerebral glucose utilization (l-CGU) were examined when JTP-2942 was administered for 4 weeks after 1 week reperfusion following ischemia in a rat middle cerebral artery (MCA) occlusion. Left middle cerebral artery ischemia was induced for 90 min followed by reperfusion. JTP-2942 (0.03 or 0.003 mg/kg) or saline (vehicle) were administered for 4 weeks after 1 week ischemia, and then the drug was withdrawn. Neurological symptoms and motor disturbance based on inclined plane test were measured once a week after 1 week ischemia. l-CBF and l-CGU were measured by quantitative autoradiographic technique after 6 weeks ischemia. The adjacent sections subjected to l-CBF or l-CGU measurement were stained with Hematoxylin-Eosin, and the infarction volume was measured. JTP-2942 (0.03 mg/kg) significantly ameliorated neurological symptoms and motor disturbance at 5 weeks after ischemia as compared with vehicle, and then after completion of drug administration, amelioration effect continued. JTP-2942 (0.03 mg/kg) also significantly ameliorated the reduced l-CBF and l-CGU in the peri-infarcted areas such as the frontal cortex, motor cortex and medial caudate-putamen. No significant differences were noted in the infarction volume among MCA occlusion rats. This indicates that activating reduced metabolic turnover associated with synaptic connection changes or the activation of compensation mechanisms may result in improvement of neurological symptoms and motor disturbances. It is therefore expected that JTP-2942 may be a possible therapeutic agent for motor disturbance during the subacute or chronic cerebral infarction.

Animals↗
PubMed2001

Large vortex-like structure of dipole field in computer models of liquid water and dipole-bridge between biomolecules.

We propose a framework to describe the cooperative orientational motions of water molecules in liquid water and around solute molecules in water solutions. From molecular dynamics (MD) simulation a new quantity "site-dipole field" is defined as the averaged orientation of water molecules that pass through each spatial position. In the site-dipole field of bulk water we found large vortex-like structures of more than 10 A in size. Such coherent patterns persist more than 300 ps although the orientational memory of individual molecules is quickly lost. A 1-ns MD simulation of systems consisting of two amino acids shows that the fluctuations of site-dipole field of solvent are pinned around the amino acids, resulting in a stable dipole-bridge between side-chains of amino acids. The dipole-bridge is significantly formed even for the side-chain separation of 14 A, which corresponds to five layers of water. The way that dipole-bridge forms sensitively depends on the side-chain orientations and thereby explains the specificity in the solvent-mediated interactions between biomolecules.

Amino Acids↗
PubMed2001

Carboranyl bisglycosides for the treatment of cancer by boron neutron capture therapy.

Boron neutron capture therapy is a special type of radiotherapy for the treatment of cancer by using boron compounds. Problems often arise from the low water solubility of these compounds, their unselective uptake into the cancer cells, and their toxicity. Here we describe the novel water-soluble ortho-carboranyl bisglycosides 7 and 10 containing either lactose or glucose and the mixed bisglycosides 1 and 28 containing glucose, mannose, and galactose. The carboranyl bisglycosides show almost no toxicity toward bronchial carcinoma cells of line A549 up to a concentration of 0.50 mM. As anticipated, these compounds exhibit nearly no uptake into C6 glioma cells; they can therefore be used for a selective delivery into malignant cells by using conjugates of glycohydrolases and monoclonal antibodies which bind to tumor-associated antigens, since by enzymatic hydrolysis the bisglycosides are transformed into lipophilic compounds.

Antineoplastic Agents↗
PubMed2001

Synthesis of [Cys(5)]mu-conotoxin GIIIA and its derivatives as a probe of Na(+) channel analysis.

The residue of Thr-5 in mu-conotoxin GIIIA (GIIIA), a receptor site I sodium channel blocker, was replaced with Cys. The synthesized [Cys(5)]GIIIA had a similar 3D structure to the native GIIIA, revealed by CD and NMR. [Cys(5)]GIIIA and its tagged peptides inhibited the electrically stimulated contraction of the rat diaphragm with relatively comparable potency to that of GIIIA. Since the contractile response to electrical stimuli is caused by the activation of sodium channels, [Cys(5)]GIIIA could be a prototype for synthesizing useful tools for the analysis of sodium channels. Thus, [Cys(5)]GIIIA could be a prototype for synthesizing useful tools for the analysis of sodium channels.

Amino Acid Sequence↗
PubMed2001

Idiopathic spinal cord herniation associated with intervertebral disc extrusion: a case report and review of the literature.

STUDY DESIGN: A case of idiopathic spinal cord herniation is reported, and the literature is reviewed. OBJECTIVE: To report a case of thoracic spinal cord herniation with a ventral dural defect, probably caused by thoracic disc extrusion. SUMMARY OF BACKGROUND DATA: Recently, reports of spinal cord herniation have been increasing. This increase can be attributed to the development of magnetic resonance imaging and increased awareness of this entity. However, the cause of the ventral dural defect remains unknown. METHODS: A 54-year-old woman had experienced Brown-Séquard syndrome for 2 years. Magnetic resonance imaging demonstrated an S-shaped anterior kinking of the spinal cord, with dilation of the dorsal subarachnoid space. RESULTS: After incision of the dural sac and gentle retraction of the spinal cord, a dural defect was recognized into which the spinal cord had herniated. An extruded disc was visualized through the defect at T3-T4. The ventral dural defect and the dorsal incision of the dural sac were repaired with a fascial graft from the thigh. CONCLUSIONS: Intraoperative findings suggest that the thoracic disc herniation in the current case was the probable cause of the ventral dural defect. Surgical reconstruction using double fascial graft under careful spinal cord monitoring resulted in a satisfactory neurologic recovery.

Brown-Sequard Syndrome↗
PubMed2001

Analysis of mutational effects of a polyhydroxybutyrate (PHB) polymerase on bacterial PHB accumulation using an in vivo assay system.

Polymerase is a central enzyme involved in the biosynthesis of polyhydroxybutyrate (PHB), a well-known bacterial biodegradable polyester. In this study, we have established an in vivo assay system to analyze mutational effects of Ralstonia eutropha polymerase (termed PhbC(Re)) on the level of PHB accumulation in recombinant strains of Escherichia coli. This in vitro evolution system consists of a polymerase chain reaction-mediated random mutagenesis and two assay procedures, a plate assay using a PHB-staining dye and a high-pressure liquid chromatographic assay based on the converting reaction from PHB to crotonic acid. The distribution pattern of the PHB accumulation level of the mutant population using 378 clones arbitrarily selected, suggested that the present level of PhbC(Re) is high and well-optimized. It is noteworthy that many of the amino acid substitutions affecting the PHB accumulation occurred in the conserved positions or regions within an 'alpha/beta hydrolase fold' which is commonly found among hydrolytic enzymes. From a good correlation with the level of PHB accumulation, an activity estimation of the PhbC(Re) would be efficiently achieved by monitoring the level of PHB accumulation using the in vivo assay system established here.

Acyltransferases↗
PubMed2001

The fibronectin-derived antiadhesive peptides suppress the myofibroblastic conversion of rat hepatic stellate cells.

We previously found that fibronectin (FN) had a functional site (YTIYVIAL sequence in the 14th type III module) suppressing the integrin-mediated cell adhesion to extracellular matrix. FN-derived peptides containing this antiadhesive site were also shown to regulate cellular processes such as proliferation, differentiation, and apoptosis. The present study shows that the FN-derived antiadhesive peptides suppress the myofibroblastic conversion of rat hepatic stellate cells (HSC). Freshly isolated HSC underwent myofibroblastic conversion during culture in the presence of FBS, as evaluated by indices representing the phenotypic activation of HSC, including increased proliferation, consumption of vitamin A-enriched lipid droplets, and expression of alpha-smooth muscle actin. However, appearance of these myofibroblastic characters was suppressed by coculturing HSC with the FN-derived antiadhesive peptides. On the other hand, the activated HSC, which had already acquired the myofibroblastic phenotype through repeated subculture, secreted FN and then stimulated matrix assembly of ED-A (+) cellular FN as well as plasma FN, while the FN-derived antiadhesive peptides inhibited them. Furthermore, the FN-derived antiadhesive peptides suppressed the integrin-mediated adhesion of the primary HSC to plasma FN and ED-A (+) cellular FN substrates. These results suggested that the FN-derived antiadhesive peptides down-regulated the myofibroblastic conversion of HSC in an indirect manner by inhibiting the integrin-mediated adhesive interaction of HSC with ED-A (+) cellular FN.

Amino Acid Sequence↗
PubMed2001

Inhibition of ADAMTS4 (aggrecanase-1) by tissue inhibitors of metalloproteinases (TIMP-1, 2, 3 and 4).

ADAMTS4 (aggrecanase-1) is considered to play a key role in the degradation of aggrecan in arthritides. The inhibitory activity of tissue inhibitors of metalloproteinases (TIMPs) to ADAMTS4 was examined in an assay using aggrecan substrate. Among the four TIMPs, TIMP-3 inhibited the activity most efficiently with an IC(50) value of 7.9 nM, which was at least 44-fold lower than that of TIMP-1 (350 nM) and TIMP-2 (420 nM) and >250-fold less than that of TIMP-4 (2 microM for 35% inhibition). These results suggest that TIMP-3 is a potent inhibitor against the aggrecanase activity of ADAMTS4 in vivo.

ADAM Proteins↗
PubMed2001

Genetic and clinical features of human pancreatic ductal adenocarcinomas with widespread microsatellite instability.

The incidences of microsatellite instability (MSI) and underlying DNA mismatch repair (MMR) defects in pancreatic carcinogenesis have not been well established. We analyzed 100 sporadic and 3 hereditary pancreatic ductal adenocarcinomas for MSI, and high-frequency MSI (MSI-H) and low-frequency MSI (MSI-L) tumors were further analyzed for frameshift mutations of possible target genes and for promoter methylation and mutation of DNA MMR genes, including hMLH1, hMSH2, hMSH3, and hMSH6 genes. Among the 100 sporadic tumors, 13 (13%) were MSI-H, 13 (13%) were MSI-L, and 74 (74%) were microsatellite stable (MSS) tumors. All of the three hereditary tumors from hereditary nonpolyposis colorectal cancer (HNPCC) patients were MSI-H. MSI-H tumors were significantly associated with poor differentiation and the presence of wild-type K-RAS and p53 genes. Patients with MSI-H tumors had a significantly longer overall survival time than did those with MSI-L or MSS tumors (P = 0.0057). Frameshift mutations of hMSH3, hMLH3, BRCA-2, TGF-beta type II receptor, and BAX genes were detected in MSI-H tumors. Hypermethylation of the hMLH1 promoter was observed in 6 (46%) of the 13 sporadic MSI-H tumors but not in any of the 3 hereditary MSI-H tumors or 13 MSI-L tumors. All of the 3 HNPCC cases had germ-line hMLH1 mutation accompanied by loss of heterogeneity or other mutation in the tumor. Our results suggest that pancreatic carcinomas with MSI-H represent a distinctive oncogenic pathway because they exhibit peculiar clinical, pathological, and molecular characteristics. Our results also suggest the principal involvement of epigenetic or genetic inactivation of the hMLH1 gene in the pathogenesis of pancreatic carcinoma with MSI-H.

Base Pair Mismatch↗