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Y Koyama

Publications and source records attributed to Y Koyama.

At least 19 recordsLinked to original sources
PubMed2001

The biocompatibility and osteoconductive activity of a novel hydroxyapatite/collagen composite biomaterial, and its function as a carrier of rhBMP-2.

A hydroxyapatite/type I collagen (HAp/Col) composite, in which the hydroxyapatite nanocrystals align along the collagen molecules, has been prepared. The biocompatibility, osteoconductive activity, and efficacy as a carrier of recombinant human bone morphogenetic proteins (rhBMPs) of this novel biomaterial were examined. The composite material was implanted in the backs of Wistar rats, and specimens were collected for histological observations until week 24. In a second experiment, other samples of the composite material (5 x 5 x 10 mm3) were drilled and immersed in a solution of rhBMP-2 (0, 200, 400 microg/mL), and subsequently grafted in radii and ulnae in beagle dogs. As a control, three unfilled holes were left in one radius and ulna. X-ray images were prepared, and specimens collected for histological observation at weeks 8 and 12. Histological findings of the composites grafted in rats showed that the surface of the material was eroded as a result of macrophage infiltration. X-ray images and histological findings for the composites implanted in dogs support the idea that HAp/ Col has a high osteoconductive activity and is able to induce bone-remodeling units. In cases where the implants are grafted at weight bearing sites, treatment with rhBMP-2 at a dose of 400 microg/mL may be useful to shorten the time needed until bone union has occurred.

Animals↗
PubMed2001

47,XXX male: A clinical and molecular study.

We report a 53-year-old Japanese male with a 47,XXX karyotype. His clinical features included hypoplastic scrotal testes (4 ml bilaterally), normally formed small penis (3.8 cm), relatively poor pubic hair development (Tanner stage 3), gynecomastia, age-appropriate male height (159.1 cm), and mental retardation (verbal IQ of 56). Serum testosterone was markedly reduced (0.6 nmol/L). A needle biopsy showed severe testicular degeneration. FISH analysis revealed complex mosaicism consisting of (1) 47,XXX cells with a single copy of SRY (n = 177), two copies of SRY (n = 3), and no SRY (n = 1); (2) 46,XX cells with a single copy of SRY (n = 9) and no SRY (n = 3); (3) 45,X cells with no SRY (n = 5); and (4) 48,XXXX cells with a single copy of SRY (n = 1) and two copies of SRY (n = 1). PCR analysis showed the presence of Yp portion with the breakpoint between DYS264 and AMELY. Microsatellite analysis demonstrated three alleles for DMD and AR. X-inactivation analysis for the methylation status of the AR gene showed random inactivation of the three X chromosomes. The results suggest that this 47,XXX male has resulted from abnormal X-Y interchange during paternal meiosis and X-X nondisjunction during maternal meiosis. Complex mosaicism may be due to the age-related increase in mitotic nondisjunction which is prone to occur in rapidly dividing lymphocytes and to the presence of two randomly inactivated X chromosomes which may behave asynchronously during mitosis, and clinical features of this male would primarily be explained by the genetic information on the SRY (+) der(X) chromosome and his advanced age.

Adolescent↗
PubMed2001

Angiotensin AT(1) and AT(2) receptors differentially regulate angiopoietin-2 and vascular endothelial growth factor expression and angiogenesis by modulating heparin binding-epidermal growth factor (EGF)-mediated EGF receptor transactivation.

Angiotensin II (Ang II)-mediated signals are transmitted via heparin binding epidermal growth factor (EGF)-like growth factor (HB-EGF) release followed by transactivation of EGF receptor (EGFR). Although Ang II and HB-EGF induce angiogenesis, their link to the angiopoietin (Ang)-Tie2 system remains undefined. We tested the effects of Ang II on Ang1, Ang2, or Tie2 expression in cardiac microvascular endothelial cells expressing the Ang II receptors AT(1) and AT(2). Ang II significantly induced Ang2 mRNA accumulations without affecting Ang1 or Tie2 expression, which was inhibited by protein kinase C inhibitors and by intracellular Ca(2+) chelating agents. Ang II transactivated EGFR via AT(1), and inhibition of EGFR abolished the induction of Ang2. Ang II caused processing of pro-HB-EGF in a metalloproteinase-dependent manner to stimulate maturation and release of HB-EGF. Neutralizing anti-HB-EGF antibody blocked EGFR phosphorylation by Ang II. Ang II also upregulated vascular endothelial growth factor (VEGF) expression in an HB-EGF/EGFR-dependent manner. AT(2) inhibited AT(1)-mediated Ang2 expression and phosphorylation of EGFR. In an in vivo corneal assay, AT(1) induced angiogenesis in an HB-EGF-dependent manner and enhanced the angiogenic activity of VEGF. Although neither Ang2 nor Ang1 alone induced angiogenesis, soluble Tie2-Fc that binds to angiopoietins attenuated AT(1)-mediated angiogenesis. These findings suggested that (1) Ang II induces Ang2 and VEGF expression without affecting Ang1 or Tie2 and (2) AT(1) stimulates processing of pro-HB-EGF by metalloproteinases, and the released HB-EGF transactivates EGFR to induce angiogenesis via the combined effect of Ang2 and VEGF, whereas AT(2) attenuates them by blocking EGFR phosphorylation. Thus, Ang II is involved in the VEGF-Ang-Tie2 system via HB-EGF-mediated EGFR transactivation, and this link should be considerable in pathological conditions in which collateral blood flow is required.

Angiopoietin-1↗
PubMed2000

KB-R7943 inhibits store-operated Ca(2+) entry in cultured neurons and astrocytes.

We have studied cyclopiazonic acid (CPA)-sensitive store-operated Ca(2+) entry (SOCE) in cultured neurons and astrocytes and examined the effect of 2-[2-[4-(4-nitrobenzyloxy)phenyl]]isothiourea (KB-R7943), which is often used as a selective inhibitor of the Na(+)-Ca(2+) exchanger (NCX), on the SOCE. CPA increased transiently intracellular Ca(2+) concentration ([Ca(2+)](i)) followed by a sustained increase in [Ca(2+)](i) in neurons and astrocytes. The sustained increase in [Ca(2+)](i) depended on the presence of extracellular Ca(2+) and inhibited by SOCE inhibitors, but not by a Ca(2+) channel inhibitor. CPA also caused quenching of fura-2 fluorescence when the cells were incubated in Mn(2+)-containing medium. KB-R7943 at 10 microM inhibited significantly CPA-induced sustained increase in [Ca(2+)](i) in neurons and astrocytes. KB-R7943 also inhibited CPA-induced quenching of fura-2 fluorescence in the presence of extracellular Mn(2+). These results indicate that cultured neurons and astrocytes possess SOCE and that KB-R7943 inhibits not only NCX but also SOCE.

Animals↗
PubMed2000

Desensitization, surface expression, and glycosylation of a functional, epitope-tagged type I PACAP (PAC(1)) receptor.

To study desensitization and glycosylation of the type I pituitary adenylate cyclase-activating polypeptide (PACAP) receptor (PAC(1)R), a hemagglutinin (HA) epitope was inserted within the N-terminal extracellular domain, allowing immunological detection of PAC(1)R both in intact and permeabilized cells. PAC(1)R was tagged without loss of functions in ligand binding and ligand-stimulated cAMP production. In transiently transfected COS-7 cells, PAC(1)R was localized both in the plasma membrane and the cytoplasm around the nucleus. By immunoblot analysis, the immunoreactive bands with relative molecular masses ranging from 45 to 70 kDa were detected in the membrane fractions of PAC(1)R-expressing COS-7 cells. Digestion of the membranes with endoglycosidase F or treatment of the cells with tunicamycin decreased the size of the receptor to major bands of smaller size (approximately 45 and 48 kDa), suggesting that these two forms of PAC(1)R represent core proteins. Flow cytometric analysis indicated that the agonist promoted a disappearance of cell surface receptor. In accordance with this observation, preexposure of cells to PACAP38 induced a desensitization of PAC(1)R to the agonist response, although it did not cause a reduction in PAC(1)R mRNA or protein level and even slightly elevated them. These results suggest that agonist-induced desensitization of PAC(1)R involves the receptor sequestration.

Amino Acid Sequence↗
PubMed2000

Na(+)-Ca(2+) exchanger isoforms in rat neuronal preparations: different changes in their expression during postnatal development.

We examined the relative amounts of Na(+)-Ca(2+) exchanger (NCX) isoform mRNAs in cultured neurons, astrocytes and developmental rat brain. NCX1 transcript was predominant in neurons and astrocytes, but NCX2 transcript was about four-fold higher than NCX1 or NCX3 transcript in adult rat cortex. NCX2 transcript in the cortex increased markedly during postnatal development, whereas NCX1 and NCX3 transcripts decreased. Na(+)-dependent 45Ca(2+) uptake in the cortical homogenate increased significantly during postnatal development.

Animals↗
PubMed2000

Angiotensin II initiates tyrosine kinase Pyk2-dependent signalings leading to activation of Rac1-mediated c-Jun NH2-terminal kinase.

Ca(2+)-sensitive tyrosine kinase Pyk2 was shown to be involved in angiotensin (Ang) II-mediated activation of extracellular signal-regulated kinase (ERK) via transactivation of epidermal growth factor receptor (EGF-R). In this study, we tested the involvement of Pyk2 and EGF-R in Ang II-induced activation of JNK and c-Jun in cardiac fibroblasts. Ang II markedly stimulated JNK activities, which were abolished by genistein and intracellular Ca(2+) chelators but partially by protein kinase C depletion. Inhibition of EGF-R did not affect Pyk2 and JNK activation by Ang II. Stable transfection with a dominant negative (DN) mutant for Pyk2 (PKM) completely blocked JNK activation by Ang II. DN mutants of Rac1 (DN-Rac1) and MEK kinase (DN-MEKK1) also abolished it, whereas those of Cdc42, RhoA, and Ha-Ras had no effect. Induction of c-Jun gene transcription by Ang II was abolished in PKM, DN-Rac1, and DN-MEKK1, in which Ang II-induced binding of ATF2/c-Jun heterodimer to the activator protein-1 sequence at -190 played a key role. These results suggest that 1) in cardiac fibroblasts activation of JNK and c-Jun by Ang II is initiated by Pyk2-dependent signalings but not by downstream signals of EGF-R or Ras, 2) Rac1 but not Cdc42 is required for JNK activation by Ang II upstream of MEKK1, and 3) ATF-2/c-Jun binding to the activator protein-1 sequence at -190 plays a key role for induction of c-Jun gene by Ang II.

Angiotensin II↗
PubMed2000

Histone deacetylase inhibitors suppress IL-2-mediated gene expression prior to induction of apoptosis.

Histone deacetylase (HDAC) inhibitors can induce transcriptional activation of a number of genes and induce cellular differentiation as histone acetylation levels increase. Although these inhibitors induce apoptosis in several cell lines, the precise mechanism by which they do so remains obscure. This study shows that HDAC inhibitors, sodium butyrate and trichostatin A (TSA), abrogate interleukin (IL)-2-mediated gene expression in IL-2-dependent cells. The HDAC inhibitors readily induced apoptosis in IL-2-dependent ILT-Mat cells and BAF-B03 transfectants expressing the IL-2 receptor betac chain, whereas they induced far less apoptosis in cytokine-independent K562 cells. However, these inhibitors similarly increased acetylation levels of histones in both cells. Although histone hyperacetylation is believed to lead to transcriptional activation, the results showed an abrogation of IL-2-mediated induction of c-myc, bag-1, and LC-PTP gene expression. This observed abrogation of gene expression occurred prior to phosphatidylserine externalization, a process that occurs in early apoptotic cells. Considering the biologic role played by IL-2-mediated gene expression in cell survival, these data suggest that its abrogation may contribute to the apoptotic process induced by HDAC inhibitors. (Blood. 2000;96:1490-1495)

Animals↗
PubMed2000

Unilateral spatial neglect in AD: significance of line bisection performance.

BACKGROUND: Unilateral spatial neglect has been rarely reported in patients with AD, although they often have right and left asymmetry of temporoparietal dysfunction. OBJECTIVE: To investigate if patients with AD would show unilateral spatial neglect in the line bisection test, and to reveal the relationship between their neglect and the area of cerebral dysfunction. METHOD: Thirty-two patients with mild to moderate AD and 32 age-matched healthy control subjects underwent an extensive line bisection test. SPECT was also obtained for the patients. RESULTS: Rightward bisection errors exceeded the normal range in 25% of patients with AD. They exhibited greater rightward errors for the longer lines in the left hemispace than in the right hemispace, and with the right hand than with the left hand; this corresponds to the characteristics of neglect seen after right hemisphere lesions. All patients who bisected 200 mm lines with errors over 10 mm showed disproportionate lowering of performance IQ and asymmetric right hemisphere hypoperfusion, especially in the temporoparietal region. Seventy-five percent of the patients performed normally in the center presentation but erred slightly toward the body midline in the right and left hemispaces. CONCLUSION: Left unilateral spatial neglect in mild to moderate AD may be rather common if tested with the line bisection test. Rightward errors over 10 mm suggest right temporoparietal dysfunction. In AD, three or more bisections of 200 mm lines in the center presentation are recommended for detection of neglect. Patients with AD but without neglect may have difficulty in shifting attention into the peripheral sector of the egocentric space.

Aged↗
PubMed2000

T-588 inhibits astrocyte apoptosis via mitogen-activated protein kinase signal pathway.

The effect of (1R)-1-benzo[b]thiophen-5-yl-2-[2-(diethylamino)ethoxy]ethan -1-ol hydrochloride (T-588), a cognition enhancer, on reperfusion injury was studied in cultured rat astrocytes. T-588 at 1-10 microM partially protected astrocytes against reperfusion injury after exposure to Ca(2+)-free medium or hydrogen peroxide. Nerve growth factor (NGF) had a similar protective effect. Addition of both T-588 and NGF resulted in complete protection against Ca(2+) reperfusion injury. T-588 did not stimulate NGF production in astrocytes. The effect of T-588 on Ca(2+) reperfusion injury including apoptosis was inhibited by the mitogen-activated protein (MAP)/extracellular signal-regulated kinase (ERK) kinase inhibitor 2'-amino-3'-methoxyflavone (PD98059), but not by the phosphoinositide 3-kinase inhibitor wortmannin. The effect of NGF was inhibited by PD98059 and wortmannin. T-588 stimulated rapidly the phosphorylation of ERK, but did not affect that of Akt in astrocytes. These findings suggest that the ERK MAP kinase pathway has a role in the protective effects of T-588 and NGF.

Androstadienes↗
PubMed2000

L-lactate inhibits L-cystine/L-glutamate exchange transport and decreases glutathione content in rat cultured astrocytes.

In several brain pathologies, the level of brain L-lactate increases. The stimulation of L-lactate production is a detrimental factor in promoting neuronal cell damage and astrocytic dysfunction. Astrocytic glutathione metabolism has an important role to protect brain cells against oxidative stress. In this study, effects of L-lactate on L-cystine uptake and glutathione level in rat-cultured astrocytes were examined. L-Lactate decreased the L-(35)S-cystine and Na(+)-independent L-(3)H-glutamate uptakes into astrocytes at the concentrations more than 2.5 mM. The L-lactate-induced decrease in L-(35)S-cystine uptake was neither affected by modification of extracellular pH nor mimicked by acetate, propionate and butyrate. The apparent Km value of the L-(35)S-cystine uptake was increased by L-lactate, while the Vmax was not changed. Astrocytic glutathione and nonprotein thiol content was decreased by incubation with 20 mM L-lactate for 48 hours (65% and 75% of control values, respectively). The decreases in astrocytic glutathione and nonprotein thiol content were restored to normal levels by withdrawal of L-lactate. These results suggest that L-lactate inhibits astrocytic L-cystine/L-glutamate exchangers and affects the glutathione contents.

Animals↗
PubMed2000

Macrophage migration inhibitory factor up-regulates expression of matrix metalloproteinases in synovial fibroblasts of rheumatoid arthritis.

Neutral matrix metalloproteinases (MMPs) are responsible for the pathological features of rheumatoid arthritis (RA) such as degradation of cartilage. We herein show the up-regulation of MMP-1 (interstitial collagenase) and MMP-3 (stromelysin) mRNAs of cultured synovial fibroblasts retrieved from rheumatoid arthritis (RA) patients in response to macrophage migration inhibitory factor (MIF). The elevation of MMP-1 and MMP-3 mRNA was dose-dependent and started at 6 h post-stimulation by MIF, reached the maximum level at 24 h, and was sustained at least up to 36 h. Interleukin (IL)-1beta mRNA was also up-regulated by MIF. These events were preceded by up-regulation of c-jun and c-fos mRNA. Tissue inhibitor of metalloproteinase (TIMP)-1, a common inhibitor of these proteases, was slightly up-regulated by MIF. Similarly, mRNA up-regulation of MMP-1 and MMP-3 was observed in the synovial fibroblasts of patients with osteoarthritis. However, their expression levels were much lower than those of RA synovial fibroblasts. The mRNA up-regulation by MIF was inhibited by the tyrosine kinase inhibitors genestein and herbimycin A, as well as the protein kinase C inhibitors staurosporine and H-7. On the other hand, the inhibition was not seen after the addition of the cyclic AMP-dependent kinase inhibitor, H-8. The mRNA up-regulation of MMPs was also inhibited by curcumin, an inhibitor of transcription factor AP-1, whereas interleukin-1 receptor antagonist, an IL-1 receptor antagonist, failed to inhibit the mRNA up-regulation. Considering these results, it is suggested that 1) MIF plays an important role in the tissue destruction of rheumatoid joints via induction of the proteinases, and 2) MIF up-regulates MMP-1 and MMP-3 via tyrosine kinase-, protein kinase C-, and AP-1- dependent pathways, bypassing IL-1beta signal transduction.

Arthritis, Rheumatoid↗
PubMed2000

New long-tip guiding catheters designed for right transradial coronary intervention.

New long-tip catheters, one for the left and the other for the right coronary artery, were designed specifically for right transradial intervention. We utilized the overbending principle to achieve more precise control of the catheters. We also analyzed principal factors involved to determine guiding catheter support considering the anatomy of the innominate artery, ascending aorta, left and right coronary arteries. Catheter shapes were designed to exploit favorable factors to compensate for mechanically disadvantageous anatomy. The catheter for the left coronary artery has an initial loop to make use of the angle between the innominate artery and the ascending aorta to introduce the catheter to the correct position to provide strong backup support. The catheter for the right coronary artery has a unique three-dimensional curve that provides sufficient backup support and compensates for the angles between the innominate artery and the proximal portion of right coronary artery to achieve coaxial engagement. The distal portions of these catheters include long tips aiming to minimize the loss of transmitted force. The performance of these catheters was studied in 143 patients with 161 lesions. Successful engagement was achieved in 138 patients with 156 lesions (97%) and coronary intervention was successful in 136 patients with 154 lesions (99%). No major complications or coronary artery dissection occurred due to use of these catheters. This study showed the present long-tip catheters to be safe and highly effective for right transradial coronary intervention. Cathet. Cardiovasc. Intervent. 49:218-224, 2000.

Angioplasty, Balloon, Coronary↗
PubMed2000

Anatomic variations of the radial artery in patients undergoing transradial coronary intervention.

Anatomic variations of the radial artery and their effect on the use of the radial artery as a route for transradial coronary intervention (TRI) were studied. Ultrasonography of the radial artery was performed prospectively in 115 patients selected to undergo elective TRI. Anatomic variations were observed in 11 of 115 patients (9.6%). Variations included six tortuous configurations (5. 2%), two stenoses (1.7%), two hypoplasias (1.7%), and one radioulnar loop (0.9%). The hypoplastic radial arteries and the radioulnar loop were inaccessible for catheterization, and coronary intervention was planned via the femoral artery. The transradial approach was attempted in the remaining 112 patients (97.4%) with only one instance of access failure, in a patient who had a stenotic vessel. These findings indicate that anatomic variations of the radial artery is not rare, and that preoperative ultrasound examination may help to exclude patients with inaccessible arteries and those at high risk for access failure.

Aged↗
PubMed2000

Nonoperative treatment of reperforated duodenal ulcer: report of three cases.

During the period between 1983 and 1998, a total of 58 patients were admitted to the surgical department of Akita Red Cross Hospital with acute duodenal perforation. Of these 58 patients, 16 were treated operatively and 42 were treated nonoperatively. Among the 38 men and 4 women who received nonoperative treatment, 3 developed reperforation. The incidence of reperforation was 7.1% and the mean average interval from the initial treatment until reperforation was 3.5 years. Endoscopic biopsy and/or serum anti-H. pylori IgG measurement revealed Helicobacter pylori infection in all three patients. No serious complications developed during the nonoperative treatment of reperforation in these three patients, and their recovery was uneventful. The hospital stay ranged from 10 to 18 days, with a mean stay of 12 days after the first perforation and from 14 to 18 days, with a mean stay of 15.6 days after the reperforation. Nonoperative treatment proved successful as a life-saving procedure for reperforation of a duodenal ulcer in all three patients.

Adult↗
PubMed2000

Why are some patients with severe neglect able to copy a cube? The significance of verbal intelligence.

Cube-copying is often used to assess constructional ability of brain-damaged patients and the influence of unilateral spatial neglect is often pointed out in patients with right hemisphere lesions. However, some patients with severe neglect perform cube-copying satisfactorily. The aim of the present study is to identify the factors that affect the performance of cube-copying in patients with left unilateral spatial neglect. Constructional performance was investigated in 100 patients with unilateral spatial neglect using a task to copy the Necker cube. The relationship of the patients' cube-copying performance to the severity of their neglect, as well as other factors (verbal intelligence, age, duration after onset of the disease, educational level, lesion site, piecemeal approach, and side of starting to copy) was analyzed. Twenty-two normal subjects also participated in this study as controls. Among many factors adopted for analysis, neglect severity and verbal intelligence were found to be primary factors affecting the cube-copying performance of the patients with unilateral spatial neglect. The effect of neglect severity on cube-copying performance was apparent in the patients whose verbal intelligence was deteriorated, but was not observed in the patients with preserved verbal intelligence. Similarly, the effect of verbal intelligence on cube-copying performance was apparent in the patients with severe neglect, but not in the patients with mild neglect. We conclude that constructional ability in the copying of a cube is determined by verbal intelligence, as well as by the severity of unilateral spatial neglect.

Aged↗