Biomedical subjects

H Tanaka

Publications and source records attributed to H Tanaka.

At least 199 records · Page 11Linked to original sources

PubMed2002

Antibacterial activity of isoflavonoids isolated from Erythrina variegata against methicillin-resistant Staphylococcus aureus.

AIMS: To screen 16 isoflavonoids isolated from Erythrina variegata (Leguminosae) for their antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). METHODS AND RESULTS: The roots of E. variegata were macerated with acetone. The chloroform-soluble fraction of the residue was subjected to repeated silica gel column chromatography followed by elution with various solvents. Structures of the isolated compounds were determined by extensive spectroscopic studies. Each compound was dissolved in dimethyl sulphoxide and added to agar plates (final concentration 1.56-100 microg ml(-1) and suspensions of MRSA spotted onto the agar plates to determine the minimum inhibitory concentration (MIC). Repeated silica gel chromatography yielded 16 compounds and spectroscopic studies revealed that all were isoflavonoids. Whilst 14 compounds showed antibacterial activity in this concentration range, the MIC values varied significantly among them. Of the active compounds, 3,9-dihydroxy-2,10-di(gamma,gamma-dimethylallyl)-6a,11a-dehydropterocarpan (erycristagallin) and 9-hydroxy-3-methoxy-2-gamma,gamma-dimethylallylpterocarpan (orientanol B) exhibited the highest activity with MIC values of 3.13-6.25 microg ml(-1). CONCLUSIONS: Erycristagallin and orientanol B showed the highest anti-MRSA activity (3.13-6.25 microg ml(-1). SIGNIFICANCE AND IMPACT OF THE STUDY: Erycristagallin and orientanol B could be leading compounds for phytotherapeutic agents against MRSA infections.

Anti-Bacterial Agents↗

PubMed2002

Characterization of infiltrating T cells and Th1/Th2-type cytokines in the synovium of patients with osteoarthritis.

OBJECTIVE: It has been suggested that osteoarthritis (OA) is induced by mechanical stress followed by cartilage destruction, and it is generally accepted that there is little involvement of an immune response in OA compared with that in rheumatoid arthritis (RA). We have previously found clonally expanded transcripts of Vbeta chain of the T cell receptor (TCR) in the synovium of patients with OA. To test the hypothesis that an immune response is involved in OA, we determined: (a) whether CD3+, CD4+, and CD8+ T-cells were infiltrating the synovial membrane of patients with OA; (b) the Th1/Th2-type cytokines produced at the protein level in the synovium of patients with OA. METHODS: Immunohistochemical analysis was performed to identify T-cells that infiltrated the synovium of patients with OA using specific antibodies against CD3+, CD4+, and CD8+ T-cell differential antigens, interferon-gamma (IFN-gamma as a marker for Th1 cells, and interleukin-4 (IL-4) as a marker for Th2 cells. RESULTS: CD4+ T-cells were strongly detected in the sublining layer of the synovium of patients with OA compared with the number detected in the same synovial layer of normal subjects. The number of IFN-gamma+ cells was significantly higher than that of IL-4+ cells in the synovium of patients with OA (P< 0.05). CONCLUSION: These observations suggest that Th1 cells predominate in the synovium of patients with OA, which clearly indicates that immune regulation occurs and may play critical roles in inflammation and cartilage destruction in patients with OA.

Aged↗

PubMed2002

Overtime work, insufficient sleep, and risk of non-fatal acute myocardial infarction in Japanese men.

OBJECTIVES: To examine the relation between working hours and hours of sleep and the risk of acute myocardial infarction (AMI), with special reference to the joint effect of these two factors. METHOD: Case-control study in Japan. Cases were 260 men aged 40-79 admitted to hospitals with AMI during 1996-8. Controls were 445 men free from AMI matched for age and residence who were recruited from the resident registers. Odds ratios of AMI relative to mean weekly working hours and daily hours of sleep in the past year or in the recent past were calculated. RESULTS: Weekly working hours were related to progressively increased odds ratios of AMI in the past year as well as in the past month, with a twofold increased risk for overtime work (weekly working hours >or=61) compared with working hours <or=40. Short time sleep (daily hours of sleep <or=5) and frequent lack of sleep (2 or more days/week with <5 hours of sleep) were also associated with a two to threefold increased risk. Frequent lack of sleep and few days off in the recent past showed greater odds ratios than those in the past year. CONCLUSIONS: Overtime work and insufficient sleep may be related to increased risk of AMI.

Adult↗

PubMed2002

DNA-directed magnetic network formations with ferromagnetic nanoparticles.

We formed a DNA network embedding ferromagnetic cobalt nanoparticles with a 12-nm diameter through a nanoscale self-assembly of DNA molecules on large-scale mica surfaces (12 mm x 12 mm); we then confirmed its structural characteristics with an atomic force microscope. Moreover, noncontact magnetic force microscope measurement revealed that some embedded cobalt nanoparticles have different directions of magnetization, similar to "bits" in magnetic data storage devices.

Aluminum Silicates↗

PubMed2002

Nuclear export of glucocorticoid receptor is enhanced by c-Jun N-terminal kinase-mediated phosphorylation.

The c-Jun N-terminal kinase (JNK) phosphorylates the glucocorticoid receptor (GR) and inhibits GR-mediated transcription. However, the biological effect of the GR phosphorylation remains unknown. Here we demonstrate that activated JNK phosphorylates human GR at Ser226 and enhances its nuclear export after withdrawal of a ligand for GR, dexamethasone. At 1 h after dexamethasone withdrawal, green fluorescent protein-GR molecules were mostly retained at the nucleus, whereas UV exposure enhanced its nuclear export, and approximately 30-40% of cells revealed distinct nuclear export. JNK overexpression alone mimics UV exposure and enhanced GR export accompanied by inhibition of GR-mediated transcription. However, mutation of the Ser226 JNK phosphorylation site in GR abrogated UV-mediated enhancement of GR nuclear export. Furthermore, overexpression of a dominant negative SEK1 mutant also abrogated the effects of UV exposure on GR export. Taken together, these findings suggest that JNK-mediated phosphorylation of the GR-Ser226 enhances GR nuclear export and may contribute to termination of GR-mediated transcription.

Active Transport, Cell Nucleus↗

PubMed2002

Pancreatic necrosis and ventricular erosion in adenovirus-associated hydropericardium syndrome of broilers.

Seven 19-day-old broiler chickens affected with hydropericardium syndrome (HPS) with pancreatic necrosis and gizzard erosions were investigated pathologically and virologically. Mortality increased after 13 days of age in a flock on a broiler farm. The mortality rate of the flock reached 10% by 19 days of age. Macroscopically, the chickens had hydropericardium (the characteristic gross change of HPS), pinpoint white foci in the pancreas, and ventricular erosions. Histologically, the chickens had multifocal hepatic necrosis with intranuclear inclusions in hepatocytes, a marked increase of macrophages in the spleen and lung, mild epicardial edema, multifocal necrosis of pancreatic acinar cells with intranuclear inclusions, focal necrosis of the ventricular koilin layer, and degeneration of the ventricular glandular epithelium with intranuclear inclusions. Immunohistochemically, intranuclear inclusions in the liver, pancreas, and ventriculi were stained positively against group I avian adenovirus (GIAAV) antigens. Ultrastructurally, 67-nm diameter viral particles were present in intranuclear inclusions. Virologically, serotype 4 of GIAAV was isolated from the liver, heart, and kidney of affected chickens. The pathologic changes of the present cases differ from previous cases of HPS; therefore, the present strain of GIAAV may have different pathogenicity for chickens than the previous virus strain of HPS.

Adenoviridae Infections↗

PubMed2002

Effect of IGF-I and PDGF administered in vivo on the expression of osteoblast-related genes in old rats.

In order to establish the cellular basis for using growth factors as possible therapeutic agents for the age-dependent deficit in bone formation activity, we examined the individual and combined effects of IGF-I and/or platelet-derived growth factor (PDGF) on the gene expression of osteoblast-related markers in male rats. The expression of osteoblast markers was examined in the femurs of adult and old rats following marrow ablation, which amplifies gene expression activity. The mRNA levels of collagen(alpha1) (I) (COLI), alkaline phosphatase (AP), osteopontin (OP) and osteocalcin (OC) were significantly lower in the old as compared with the adult rats. To determine whether growth factors can abolish the age-related deficits in mRNA expression in old bone, PDGF and/or IGF-I were infused directly into the right femur for 5 days following marrow ablation. The contralateral femur was infused with vehicle only and used as a control. PDGF stimulated the expression of OP mRNA in both adult and old rats, whereas COLI, AP and OC mRNAs were not affected. IGF-I infusion did not have a significant effect on mRNA expression in adult rats. In contrast, treatment with IGF-I significantly enhanced the mRNA levels of COLI, AP and OP in old rats. To examine whether the combination of both factors could affect the expression of osteoblast markers synergistically, PDGF and IGF-I were infused together. In adult bones, the combined treatment with PDGF and IGF-I caused a slight increase in the level of OP gene expression but no change in AP, OC or COLI genes. Although neither IGF-I nor PDGF alone was effective in stimulating the expression of OC, the combined treatment in old bones enhanced OC expression significantly. The expression of COLI, AP and OP was also stimulated, but the stimulation was no different from that of IGF-I alone. In PDGF plus IGF-I treatment with a high dose, no dose-response effects were observed. Within the limits of the present study, it is suggested that IGF-I and, to a much lesser extent, PDGF may partially restore the deficit in the expression of osteoblast markers in old bones, and that the combination of both factors is slightly better than IGF-I alone in stimulating OC expression.

Alkaline Phosphatase↗

PubMed2002

Application of toxicity monitor using nitrifying bacteria biosensor to sewerage systems.

Toxic substances may be included in wastewater influent and can damage biological processing of wastewater treatment, therefore continuous toxic-monitoring of wastewater influent is needed. This paper describes the potential toxic-monitoring applications of the toxicity monitor using a nitrifying bacteria biosensor to sewerage systems. The results of sensitivity tests show that aspects of wastewater do not affect the sensor sensitivity and confirm that the sensor can be applied to wastewater monitoring as it is. The monitor with a prototype of filtration system installed in a wastewater treatment plant is able to operate continuously for one month at least after the modification of filtration system and the optimization of operation conditions.

Biosensing Techniques↗

PubMed2002

Quantitative comparison of forests and other areas with dry weather input loading in the Lake Biwa catchment area.

For the evaluation of pollutants loading to Lake Biwa, comprehensive river surveys on river mouths and forest sites were conducted 9 times from 1996 to 1999, on 25-40 main rivers in the Lake Biwa watershed. The main results obtained are as follows. (1) River water quality reflects regional characteristics a of their catchment areas, and the concentration difference among rivers ranged between 2-3 fold. (2) Concentration variation shows different patterns with time and location depending on water quality indices a used. (3) Indices related to organic matter and nutrients have lower correlation between forests and river mouths, but those related to ionic species showed strong correlation. (4) Flux comparison of forest and river mouth sites suggests that pollutants from catchment areas are conveyed to the lake not only through rivers but also underground. (5) In dry weather conditions, forests contribute 30% to the whole pollutants (TN, TP, and TCOD(Mn)) loading, and the remainder is derived mainly from paddy fields and residential/commercial zones. (6) Unit loading factors from forests are estimated as 640, 57 and 1200 kg/km2/y, respectively for TN, TP and TCOD(Mn), while those from other areas are estimated as 2,500, 208 and 4,200 kg/km2/y.

Agriculture↗

PubMed2002

2-Nicotinamidoethyl nitrale (2-NN) protects myocardium in ischemia and reperfusion via the protein kinase C pathway.

BACKGROUND: Several recent studies have suggested an ATP-sensitive potassium channel opener (2-nicotinamidoethyl nitrate: 2-NN) may exert a protective effect against the myocardial ischemic/reperfusion injury. This study examines the effects of 2-NN on intracellular signaling by measuring intracellular cyclic AMP, cyclic GMP accumulation and protein kinase C (PKC) activity after 2-NN perfusion. METHODS: Ischemia/reperfused hearts were made by LAD occlusion for 30 min followed by 30 min of reperfusion in isolated rat hearts. Hearts were pre-perfused with 0.1 mM 2-NN, 100 nM Calphostin C, or 2-NN plus Calphostin C for 10 min prior to ischemia. The left ventricular function, cyclic AMP, cyclic GMP and LDH were examined to determine the effects of 2-NN on ischemic/reperfusion injury. Four separate groups of hearts were stained with a bisindolylmaleimide PKC inhibitor conjugated to fluorescein (fim, Teflabs) and PKC activity was measured. RESULTS: 2-NN reduced ischemia/reperfusion injury as evidenced by the enhanced myocardial functional recovery, decreased LDH release after reperfusion, and decreased reperfusion arrhythmias. The PKC inhibitor attenuated myocardial functional recovery but not reperfusion arrhythmias. Cyclic AMP levels decreased after 10 min of 2-NN perfusion, compared to controls. We observed an increase in PKC activity after 2-NN treatment. CONCLUSIONS: These results suggest that PKC plays a significant role in the cardioprotective effect of 2-NN on ischemic and reperfused myocardium. The anti-arrhythmic effect of 2-NN in the reperfusion phase may be linked its action on the ATP-sensitive potassium channel itself rather than its effect on PKC activity.

Animals↗

PubMed2002

Comparison of yeast-based estrogen receptor assays.

In order to quantitatively compare measurement methods used to evaluate estrogenic activity in environmental samples, 13 substances and sewage samples were measured using three methods that employ recombinant yeast to measure such estrogenic activity. The estrogenic activity of the chemical substances confirmed a correlation between the three measurement methods. Two methods failed to measure estrogenic activity in some of the sewage samples because the yeast growth was inhibited. But the one remaining method was able to estimate the estrogenic activities of all sewage samples without the inhibition of the yeast growth. Similar correlation was observed between the methods for the estrogenic activities of the final discharge that was measured.

Biological Assay↗

PubMed2001

Involvement of Ca2+ waves in excitation-contraction coupling of rat atrial cardiomyocytes.

Two-dimensional and line-scan analyses of the early phase Ca2+ transients in rat cardiomyocytes were performed with a rapid-scanning laser confocal microscope and fluo-3 to elucidate the mechanism of activation of Ca2+ release from the sarcoplasmic reticulum in atrial myocytes which lack a well developed T-tubular network. On electrical stimulation of ventricular myocytes, Ca2+ concentration began to rise earliest at the Z-line level and became uniform throughout the cytoplasm within about 10 msec. In contrast, on stimulation of atrial myocytes, the earliest rise in Ca2+ occurred at the cell periphery and then spread to the cell interior; cytoplasmic Ca2+ became uniform after more than 30msec. The velocity of the propagation of rise in Ca2+ was 112 +/- 5.1 microm/sec (n = 10), which was similar to that of spontaneous Ca2+ waves observed in atrial and ventricular myocytes. No difference in frequency, amplitude and kinetics of spontaneous Ca2+ sparks was observed between the subsarcolemmal and central regions of atrial myocytes. Ryanodine concentration-dependently decreased the contractile force of isolated rat atrial and ventricular tissue preparations; the sensitivity was higher in atrial myocytes. The present study visualized the involvement of a propagated Ca2+-induced-Ca+ release mechanism in atrial but not ventricular myocytes. This difference may underlie some of the atrioventricular difference in response to physiological and pharmacological stimuli.

Animals↗

PubMed2001

Enzyme-linked immunosorbent assay for glycyrrhizin using anti-glycyrrhizin monoclonal antibody and an eastern blotting technique for glucuronides of glycyrrhetic acid.

Hybridomas secreting a monoclonal antibody against glycyrrhizin were produced by fusing splenocytes from a mouse immunized against a glycyrrhizin-bovine serum albumin conjugate with the hypoxanthine-aminopterin-thymidine-sensitive mouse myeloma cell line, P3-X63-Ag8-653. A very weak cross-reaction with glycyrrhetinic acid monoglucuronide and glycyrrhetic acid occurred. An enzyme-linked immunosorbent assay (ELISA) that had an effective measuring range of 20 -200 ng/mL of glycyrrhizin was established using this monoclonal antibody. In addition, a method named eastern blotting for the detection of glycyrrhizin was investigated. In this method, we developed a new way to separate the glycyrrhizin molecule into two functional parts using a simple and well-known chemical reaction. The sugar parts were oxidized by sodium periodate to give dialdehydes, which reacted with amino groups on the protein and covalently bound to the adsorbent membrane. The monoclonal antibody bound to the aglycone part of the glycyrrhizin molecule for immunostaining. This method was validated by immunocytolocalization of glycyrrhizin in fresh Glycyrrhiza root.

Animals↗

PubMed2001

DNA-PKcs is critical for telomere capping.

The DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is critical for DNA repair via the nonhomologous end joining pathway. Previously, it was reported that bone marrow cells and spontaneously transformed fibroblasts from SCID (severe combined immunodeficiency) mice have defects in telomere maintenance. The genetically defective SCID mouse arose spontaneously from its parental strain CB17. One known genomic alteration in SCID mice is a truncation of the extreme carboxyl terminus of DNA-PKcs, but other as yet unidentified alterations may also exist. We have used a defined system, the DNA-PKcs knockout mouse, to investigate specifically the role DNA-PKcs specifically plays in telomere maintenance. We report that primary mouse embryonic fibroblasts (MEFs) and primary cultured kidney cells from 6-8 month-old DNA-PKcs-deficient mice accumulate a large number of telomere fusions, yet still retain wild-type telomere length. Thus, the phenotype of this defect separates the two-telomere related phenotypes, capping, and length maintenance. DNA-PKcs-deficient MEFs also exhibit elevated levels of chromosome fragments and breaks, which correlate with increased telomere fusions. Based on the high levels of telomere fusions observed in DNA-PKcs deficient cells, we conclude that DNA-PKcs plays an important capping role at the mammalian telomere.

Animals↗

PubMed2001

Involvement of gicerin in the extension of microvilli.

Gicerin is a cell adhesion molecule belonging to the immunoglobulin superfamily. To study the functional differences between l- and s-gicerin, we first examined the distribution of endogenous gicerin in B16 cells and found that l-gicerin was densely localized in microvilli. To clarify the relationship between gicerin and the microvilli, we established independent stable cell lines expressing l- and s-gicerin in L cells and found that l-gicerin localized to the microvilli. Scanning electron microscopic analysis revealed that the microvilli of l-gicerin-transfected cells were longer than those of s-gicerin and control transfectants. This suggested that l-gicerin might participate in the elongation of the microvilli. When cells were double-stained with antibodies to gicerin and moesin, a microvilli-specific protein, the staining of l-gicerin corresponded to that of moesin in the elongated microvilli. Moesin was coprecipitated with glutathione S-transferase-fusion proteins of the l-gicerin cytoplasmic domain but not with the s-gicerin cytoplasmic domain. To determine the region involved in the extension of microvilli, we generated transfectants of two truncated forms of l-gicerin cytoplasmic domain, and we found that only the transfectants of the longer mutant had the longer microvilli, while the shorter mutant exhibited short microvilli. These results suggested that l-gicerin-specific amino acid residues, especially amino acids 16-39, within the cytoplasmic domain of l-gicerin might be involved in the extension of microvilli.

Actins↗

PubMed2001

Calmegin is required for fertilin alpha/beta heterodimerization and sperm fertility.

Loss of the endoplasmic reticulum resident chaperone calmegin leads to the production of sterile sperm that do not bind to the egg zona pellucida (M. Ikawa et al., 1997, Nature 387, 607-611). In the present study, we demonstrate that calmegin -/- sperm were defective in migrating into the oviducts and in binding to the egg plasma membrane. Despite the impaired adhesive function, calmegin -/- sperm could fertilize eggs when zonae pellucidae were partially dissected, and eggs fertilized in this manner could develop normally to term. Since these sperm characteristics were similar to those found in fertilin beta -/- sperm, we investigated the interaction of calmegin with fertilin beta. Using immunoprecipitation techniques, calmegin was found to bind to sperm membrane proteins, fertilin alpha and beta, during spermatogenesis. The binding was specific to calmegin: another endoplasmic reticulum chaperone calnexin, a calmegin homologue, was not able to bind to fertilin alpha and beta. In the calmegin -/- mice, a loss of heterodimerization of fertilin alpha and beta was observed and fertilin beta was not detectable in mature sperm. The data not only explain why the calmegin and fertilin beta knockout mouse lines share a common infertile phenotype, but also reveal the importance of the maturation of sperm membrane proteins in the endoplasmic reticulum.

ADAM Proteins↗

PubMed2001

Electrophysiological analysis of the negative chronotropic effect of endothelin-1 in rabbit sinoatrial node cells.

1. Electrophysiological effects of endothelin-1 (ET-1) were studied in rabbit sinoatrial node (SAN) using conventional microelectrode and whole-cell voltage and current recordings. 2. In rabbit SAN, RT-PCR detected ET(A) endothelin receptor mRNA. ET-1 (100 nM) increased the cycle length of action potentials (APs) from 305 +/- 15 to 388 +/- 25 ms; this effect was antagonised by the ET(A) receptor-selective antagonist BQ-123 (1 microM). ET-1 increased AP duration (APD50) by 22%, depolarised the maximum diastolic potential (MDP) from -59 +/- 1 to -53 +/- 2 mV, shifted the take-off potential by +5 mV and decreased the pacemaker potential (PMP) slope by 15%. Under exactly the same experimental conditions, ET-1 caused a positive chronotropic effect in guinea-pig SAN with a decrease of 13% in APD50, a shift of -4 mV in the take-off potential and an increase of 8% in the PMP slope. 3. Rabbit SAN exhibited two major cell types, distinguished both by their appearances and by their electrophysiological responses to ET-1. Whereas the spontaneous pacing rate and the PMP slope were similarly decreased by ET-1 (10 nM) in both cell types, ET-1 depolarised MDP from -67 +/- 1 to -62 +/- 4 mV in spindle-shaped cells but hyperpolarised it from -73 +/- 1 to -81 +/- 3 mV in rod-shaped cells. ET-1 decreased APD50 by 8 and 52% and shifted the take-off potential by +5 and -9 mV in spindle- and rod-shaped cells, respectively. 4. ET-1 decreased the high-threshold calcium current (I(CaL)) by about 50% in both cell types, without affecting its voltage dependence, and decreased the delayed rectifier K+ current (I(K)) with significant shifts (of +4.7 and +14.0 mV in spindle- and rod-shaped cells, respectively) in its voltage dependence. It was exclusively in rod-shaped cells that ET-1 activated a sizeable amount of time-independent inward-rectifying current. 5. The hyperpolarisation-activated current (I(f)), observed exclusively in spindle-shaped cells, was significantly increased by ET-1 at membrane potentials between -74.7 and -84.7 mV whereas it was significantly decreased at more negative potentials. ET-1 significantly decreased the slope of the current-voltage (I-V) relation of the I(f) tail without changing its half-maximum voltage. 6. The overall negative chronotropic influence of ET-1 on the whole rabbit SAN is interpreted as resulting from the integration of its different actions on spindle- and rod-shaped SAN cells through electrotonic interaction.

Action Potentials↗

PubMed2001

Inhibitory PAS domain protein is a negative regulator of hypoxia-inducible gene expression.

Alteration of gene expression is a crucial component of adaptive responses to hypoxia. These responses are mediated by hypoxia-inducible transcription factors (HIFs). Here we describe an inhibitory PAS (Per/Arnt/Sim) domain protein, IPAS, which is a basic helix-loop-helix (bHLH)/PAS protein structurally related to HIFs. IPAS contains no endogenous transactivation function but demonstrates dominant negative regulation of HIF-mediated control of gene expression. Ectopic expression of IPAS in hepatoma cells selectively impairs induction of genes involved in adaptation to a hypoxic environment, notably the vascular endothelial growth factor (VEGF) gene, and results in retarded tumour growth and tumour vascular density in vivo. In mice, IPAS was predominantly expressed in Purkinje cells of the cerebellum and in corneal epithelium of the eye. Expression of IPAS in the cornea correlates with low levels of expression of the VEGF gene under hypoxic conditions. Application of an IPAS antisense oligonucleotide to the mouse cornea induced angiogenesis under normal oxygen conditions, and demonstrated hypoxia-dependent induction of VEGF gene expression in hypoxic corneal cells. These results indicate a previously unknown mechanism for negative regulation of angiogenesis and maintenance of an avascular phenotype.

Amino Acid Sequence↗