Search PubMed⌕ Search

Biomedical subjects

Y Katagiri

Publications and source records attributed to Y Katagiri.

At least 19 recordsLinked to original sources
PubMed2000

Cloning and characterization of the promoter region of the rat epidermal growth factor receptor gene and its transcriptional regulation by nerve growth factor in PC12 cells.

Our previous studies have shown that treatment of PC12 cells with nerve growth factor (NGF) causes a profound down-regulation of the epidermal growth factor receptor (EGFR) mRNA and protein. Further, the NGF-induced down-regulation of the EGFR is under transcriptional control. To elucidate the molecular mechanism of this down-regulation we have cloned a 2.7-kilobase sequence from the promoter region of the rat EGFR from a rat P1 library. Six transcriptional start sites were identified by 5'-rapid amplification of cDNA ends and primer extension. Sequence analysis showed a 62% overall homology with the human EGFR promoter region. To investigate its transcription, 1.1 kilobases of the 5'-flanking sequence were fused to a luciferase reporter gene. This sequence exhibited functional promoter activity in transient transfection experiments with PC12, C6, and CV-1 cells. Treatment of PC12 cells with NGF inhibited promoter activity. By transfection of promoter deletion constructs, a silencer element was found between nucleotides -260 and -181, and TCC repeat sequences appeared to be at least partially responsible for the down-regulation of the EGFR by NGF. Supportive evidence for the relevance of this sequence was obtained from gel mobility shift assays and by transfection of TCC mutation constructs. Our results demonstrate that TCC repeat sequences are required for the down-regulation of rat EGFR by NGF in PC12 cells and may lead to the identification of the NGF-responsive transcription factors.

Animals↗
PubMed2000

Modulation of retinoid signalling through NGF-induced nuclear export of NGFI-B.

The retinoid-X receptor (RXR) regulates multiple hormonal pathways through heterodimerization with nuclear receptors such as the all-trans retinoic acid receptor (RAR). The orphan nuclear receptor NGFI-B (also called Nur77) can heterodimerize with RXR. Here we show that nerve growth factor (NGF) induces the phosphorylation of Ser 105 of NGFI-B in PC12 phaeochromocytoma cells, resulting in translocation of the NGFI-B-RXR heterodimer complex out of the nucleus using nuclear export signals within NGFI-B. As a consequence of the redistribution of RXR, the transcriptional activity of RXR-RAR is reduced. NGFI-B-mediated nuclear export of receptors may serve as a mechanism for crosstalk between NGF and retinoid pathways.

Amino Acid Sequence↗
PubMed2000

Delayed and sustained activation of p42/p44 mitogen-activated protein kinase induced by proteasome inhibitors through p21(ras) in PC12 cells.

Proteolysis by the ubiquitin/proteasome pathway regulates the intracellular level of several proteins, some of which control cell proliferation and cell cycle progression. To determine what kinds of signaling cascades are activated or inhibited by proteasome inhibition, we treated PC12 cells with specific proteasome inhibitors and subsequently performed in-gel kinase assays. N-Acetyl-Leu-Leu-norleucinal and lactacystin, which inhibit the activity of the proteasome, induced the activation of p42/p44 mitogen-activated protein (MAP) kinases [extracellular signal-regulated kinases (ERKs) 1 and 2]. In contrast, N-acetyl-Leu-Leu-methional, which inhibits the activity of calpains, but not of the proteasome, failed to induce ERK activation. Uniquely, the kinetics of MAP kinase activation induced by proteasome inhibitors are very slow compared with those resulting from activation by nerve growth factor; ERK activation is detectable only after a 5-h treatment with the inhibitors, and its activity remained unchanged for at least until 27 h. Proteasome inhibitor-initiated ERK activation is inhibited by pretreatment with the ERK kinase inhibitor PD 98059, as well as by overexpression of a dominant-negative form of Ras. Thus, proteasome inhibitors induce sustained ERK activation in a Ras-dependent manner. Proteasome inhibitor-induced neurite outgrowth, however, is not inhibited by PD 98059, indicating that sustained activation of ERKs is not the factor responsible for proteasome inhibitor-induced morphological differentiation. Our data suggest the presence of a novel mechanism for activation of the MAP kinase cascade that involves proteasome activity.

Acetylcysteine↗
PubMed2000

Structure-specific effects of thyroxine analogs on human liver 3 alpha-hydroxysteroid dehydrogenase.

The NADP(H)-linked oxidoreductase activity of a major isozyme of human liver 3 alpha-hydroxysteroid dehydrogenase was activated 5-, 4-, and 2-fold by D-thyroxine (T(4)), L-T(4) and DL-3,3', 5'-triiodothyronine (reverse T(3)), respectively. Kinetic analysis of the activation indicated that D-T(4), L-T(4), and reverse T(3) are non-essential activators, showing binding constants of 1.5, 1.1, and 3.6 microM, respectively. Comparison of the effects of the T(4) analogs on the activities of the mutant enzymes suggests that the binding site is composed of at least Lys-270, Arg-276, and the C-terminal loop of the enzyme. L-T(3), DL-thyronine, and D-tyrosine had no effect on the enzyme, but 3,5,3',5'-tetra- and 3,5, 3'-tri-iodo thyropropionic acids were potent competitive inhibitors with K(i) values of 42 and 60 nM, respectively, with respect to the substrate. The inhibition constant was lowered upon the activation of the enzyme by D-T(4), and the inhibition by the deamino derivatives of T(4) and T(3) disappeared upon modification of the C-terminal loop of the enzyme, but not upon replacement of Lys-270 or Arg-276 with Met. These results indicate that, depending on their structures, the T(4) analogs bind differently to two distinct sites at the active center of the enzyme to produce stimulatory and inhibitory effects.

3-Hydroxysteroid Dehydrogenases↗
PubMed2000

Selection of mobile phase in high-performance liquid chromatographic determination for medicines.

A convenient method was developed to select mobile phase to separate drugs commonly used in clinical therapy, using high-performance liquid chromatography (HPLC). The separation conditions determined by this method were similar for each compound. Two kinds of mobile phase, a mixture of acetonitrile-phosphate buffers, pH 4.2 and 2.5, was used and the composition of mobile phase used for a drug in HPLC analysis was systematically determined as follows: (1) the retention time of a drug was measured under the gradient condition, (2) this retention time value was applied to the regression equation which was determined from the retention time values of p-hydroxybenzoate derivatives under the gradient condition and the concentration of acetonitrile in mobile phase, giving about 5 min of retention time, (3) percentage of acetonitrile in the isocratic condition was calculated from this regression equation and a target drug was eluted with the mobile phase consisting of the calculated concentration of acetonitrile. According to the proposed method, the composition of mobile phase, with which retention time value was between 4 to 8 min in the isocratic condition, was examined for 75 drugs clinically used. Seventy-two of the 75 drugs were analyzed well in the mobile phase, their composition was calculated by the regression equation, and the peak shape of each compound was observed to be sharp. Using this method, the time required for not only the setting of HPLC conditions but also the analysis will be shortened.

Buffers↗
PubMed2000

HPLC analysis of white lupin isoflavonoids.

An investigation of the HPLC analytical conditions for simple isoflavones, prenylated isoflavones and some of their glucosyl derivatives resulted in reasonable separation and total elution in 35 min when using a reversed-phase C18 Lichrospher column and a gradient elution system of MeCN-THF-H2O. This method was successfully applied to quantify the changes in isoflavonoid constituents in white lupin (Lupinus albus L.) tissues: (a) young legumes (pods and seeds) during maturation, and (b) soaked, germinating seeds. In developing legumes, genistein and 2'-hydroxygenistein, as well as their prenylated derivatives, were present in the pods as the major components, together with minor amounts of glucosides, whereas only minute amounts of isoflavonoids were detectable in the ripening seeds. When soaked with water, mature lupin seeds which normally contain trace amounts of isoflavonoids, started rapidly to biosynthesize simple isoflavones and accumulate large amounts of genistein 7-O-glucoside and its 6"-O-malonyl derivative. These dynamic changes are discussed in relation to the role of isoflavonoids in the lupin defense system.

Chromatography, High Pressure Liquid↗
PubMed1999

Nerve growth factor (NGF)-induced calcium influx and intracellular calcium mobilization in 3T3 cells expressing NGF receptors.

The neurotrophins have been implicated in the acute regulation of synaptic plasticity. Neurotrophin-stimulated presynaptic calcium uptake appears to play a key role in this process. To understand the mechanism of neurotrophin-stimulated calcium uptake, the regulation of calcium uptake and intracellular mobilization by nerve growth factor (NGF) was investigated using NIH 3T3 cells stably transfected with either the high affinity NGF receptor p140(trk) (3T3-Trk) or the low affinity NGF receptor p75(NGFR) (3T3-p75). In 3T3-Trk cells, NGF increased both calcium uptake and intracellular calcium mobilization. In 3T3-p75 cells, NGF increased calcium uptake but not intracellular calcium mobilization. K-252a alone increased intracellular calcium in 3T3-Trk cells but not in 3T3-p75 cells. Nifedipine, an inhibitor of calcium uptake through L-type calcium channels, inhibited the action of NGF on both 3T3-Trk cells and 3T3-p75 cells, indicating that both p140(trk) and p75(NGFR) receptors are linked to nifedipine-sensitive L-type calcium channels. These studies show that either NGF receptor will support increases in intracellular calcium but that p140(trk) does so by increasing both uptake and mobilization, whereas p75(NGFR) does so by increasing uptake only.

3T3 Cells↗
PubMed1999

Urinary excretion of the vitronectin receptor (integrin alpha V beta 3) in patients with Fabry disease.

A renal disorder is one of the important manifestations of Fabry disease, but the details of the pathogenesis have not been clarified yet. We examined the possibility that the vitronectin receptor (VNR, integrin alpha V beta 3), one of the integrins, is involved in the progression of the renal injury in Fabry disease. We measured the urinary excretion of beta 3 originating from VNR in Fabry patients by immunoblotting analysis and enzyme-linked immunosorbent assay (ELISA). Immunofluorescent microscopic analyses for VNR and globotriaosylceramide were performed on urinary sediments from Fabry patients. Furthermore, beta 3 and vitronectin in kidney tissues were analyzed immunohistochemically. Immunoblotting analysis and ELISA showed that the urinary excretion of beta 3 originating from VNR was significantly increased in the Fabry group compared with both the pathological and healthy control groups. Immunofluorescent microscopy revealed the expression of VNR and accumulation of globotriaosylceramide in urinary sediments from the Fabry patients. Increased expression of beta 3 was observed in glomerular epithelial cells, and in Bowman's capsular epithelial layer and tubular cells, and the amount of vitronectin was moderately increased in the kidney tissues from the Fabry patients. The urinary excretion of VNR was increased, and the expression of VNR was observed in Fabry kidney tissues. The expression of VNR may be involved in the progression of the renal injury in this disease.

Adolescent↗
PubMed1999

Distribution of the cfiA gene among Bacteroides fragilis strains in Japan and relatedness of cfiA to imipenem resistance.

The cfiA gene, encoding an imipenem-hydrolyzing metallo-beta-lactamase produced by Bacteroides fragilis, and insertion-like elements were detected by PCR amplification with B. fragilis strains isolated in Japan. The cfiA gene was found in 1.9 and 4.1% of the imipenem-susceptible B. fragilis isolates collected from 1987 to 1988 and from 1992 to 1994, respectively. Insertion-like elements adjacent to the cfiA gene were found in all nine metallo-beta-lactamase-producing imipenem-resistant strains tested but not in nine cfiA-positive strains with no detectable metallo-beta-lactamase activity.

Bacterial Proteins↗
PubMed1999

Two cases of cutaneous apocrine ductal carcinoma of the axilla. Case report and review of the literature.

We report 2 cases of cutaneous apocrine ductal carcinoma (CADC) of the axilla in a 64- and a 54-year-old male. Histological examination revealed 2 solid, ductal and glandular tumors with decapitation secretion. Tumor cells showed cellular and nuclear atypism, and infiltrative growth of tumor cell nests was also observed. Although there were no characteristic features of extramammary Paget's disease on the overlying skin, case 1 exhibited a typical Paget's phenomenon. We concluded that the Paget's phenomenon of case 1 was a result of upward extension of the tumor in the dermis. The neoplastic cells of both cases were immunohistochemically positive for gross cystic disease fluid protein, lysozyme, CD15 and carcinoembryonic antigen but negative for S-100 protein. Based on these findings, we concluded that these tumors were cutaneous apocrine ductal carcinomas. There was no evidence of tumor remnants in the axilla, and the patients have shown no signs of local recurrence or metastasis. We also reviewed the literature and summarize here the clinical features of CADC.

Adenocarcinoma↗
PubMed1998

Roles of the C-terminal domains of human dihydrodiol dehydrogenase isoforms in the binding of substrates and modulators: probing with chimaeric enzymes.

Human liver dihydrodiol dehydrogenase (DD; EC 1.3.1.20) exists in isoforms (DD1, DD2 and DD4) composed of 323 amino acids. DD1 and DD2 share 98% amino acid sequence identity, but show lower identities (approx. 83%) with DD4, in which a marked difference is seen in the C-terminal ten amino acids. DD4 exhibits unique catalytic properties, such as the ability to oxidize both (R)- and (S)-alicyclic alcohols equally, high dehydrogenase activity for bile acids, potent inhibition by steroidal anti-inflammatory drugs and activation by sulphobromophthalein and clofibric acid derivatives. In this study, we have prepared chimaeric enzymes, in which we exchanged the C-terminal 39 residues between the two enzymes. Compared with DD1, CDD1-4 (DD1 with the C-terminal sequence of DD4) had increased kcat/Km values for 3alpha-hydroxy-5beta-androstanes and bile acids of 3-9-fold and decreased values for the other substrates by 5-100-fold. It also became highly sensitive to DD4 inhibitors such as phenolphthalein and hexoestrol. Another chimaeric enzyme, CDD4-1 (DD4 with the C-terminal sequence of DD1), showed the same (S)-stereospecificity for the alicyclic alcohols as DD1, had decreased kcat/Km values for bile acids with 7beta- or 12alpha-hydroxy groups by more than 120-fold and was resistant to inhibition by betamethasone. In addition, the activation effects of sulphobromophthalein and bezafibrate decreased or disappeared for CDD4-1. The recombinant DD4 with the His314-->Pro (the corresponding residue of DD1) mutation showed intermediate changes in the properties between those of wild-type DD4 and CDD4-1. The results indicate that the binding of substrates, inhibitors and activators to the enzymes is controlled by residues in their C-terminal domains; multiple residues co-ordinately act as determinants for substrate specificity and inhibitor sensitivity.

Amino Acid Sequence↗
PubMed1998

Nerve growth factor treatment prevents the increase in superoxide produced by epidermal growth factor in PC12 cells.

Stimulation of pheochromocytoma (PC12) cells with the mitogen epidermal growth factor (EGF) produced a rapid and robust accumulation of intracellular reactive oxygen species (ROS), an accumulation which, in other systems, has been shown to be essential for mitogenesis. Brief pretreatment of the cells with nerve growth factor (NGF) suppressed the EGF-mediated ROS increase. EGF failed to produce elevations in ROS in a PC12 variant stably expressing a dominant-negative p21(ras) construct (PC12-N17) or in cells pretreated with the MEK inhibitor PD098059. NGF failed to suppress the increase in ROS in the PC12 variant nnr5, which lacks p140(trk) receptors. The suppression of the increase in ROS by NGF was restored in nnr5 cells stably expressing p140(trk) (nnr5-trk), but NGF failed to prevent the increase in ROS in nnr cells expressing mutant p140(trk) receptors that lack binding sites for Shc and phospholipase Cgamma. Among several inhibitors of superoxide-generating enzymes, only the lipoxygenase inhibitor, nordihydroguaiaretic acid reduced EGF-mediated ROS accumulation. The inhibitory action of NGF on ROS production was mimicked by the nitric oxide donor, sodium nitroprusside, and was blocked by an inhibitor of nitric-oxide synthetase, L-nitroarginine methyl ester. These results suggest a novel mechanism for the rapid interruption of mitogenic signaling by the neurotrophin NGF.

Animals↗
PubMed1998

Spermine is not essential for growth of Saccharomyces cerevisiae: identification of the SPE4 gene (spermine synthase) and characterization of a spe4 deletion mutant.

Spermine, ubiquitously present in most organisms, is the final product of the biosynthetic pathway for polyamines and is synthesized from spermidine. In order to investigate the physiological roles of spermine, we identified the SPE4 gene, which codes for spermine synthase, on the right arm of chromosome XII of Saccharomyces cerevisiae and prepared a deletion mutant in this gene. This mutant has neither spermine nor spermine synthase activity. Using the spe4 deletion mutant, we show that S. cerevisiae does not require spermine for growth, even though spermine is normally present in the wild-type organism. This is in striking contrast to the absolute requirement of S. cerevisiae for spermidine for growth, which we had previously reported using a mutant lacking the SPE3 gene (spermidine synthase) [Hamasaki-Katagiri, N., Tabor, C. W., Tabor, H., 1997. Spermidine biosynthesis in Saccharomyces cerevisiae: Polyamine requirement of a null mutant of the SPE3 gene (spermidine synthase). Gene 187, 35-43].

Amino Acid Sequence↗
PubMed1998

Transcriptional down-regulation of epidermal growth factor receptors by nerve growth factor treatment of PC12 cells.

Treatment of PC12 cells with nerve growth factor leads to a decrease in the number of epidermal growth factor receptors on the cell membrane. The mRNA for the epidermal growth factor receptor decreases in a comparable fashion. This decrease appears due to a decrease in the transcription of the epidermal growth factor receptor gene because first, there is no difference in the stability of the epidermal growth factor receptor mRNA, second, newly transcribed epidermal growth factor receptor mRNA is decreased in nerve growth factor-differentiated cells, and third, constructs containing the promoter region of the epidermal growth factor receptor gene are transcribed much less readily in nerve growth factor-differentiated cells than in untreated cells. The decreases in mRNA are not seen in the p140(trk)-deficient variant PC12nnr5 cells nor in cells containing either dominant-negative Ras or dominant-negative Src. Treatment with nerve growth factor also increases the cellular content of GCF2, a putative transcription factor inhibitory for the transcription of the epidermal growth factor receptor gene. The increase in GCF2, like the decrease in the epidermal growth factor receptor mRNA, is not seen in PC12nnr5 cells nor in cells expressing either dominant-negative Ras or dominant-negative Src. The results suggest that nerve growth factor-induced down-regulation of the epidermal growth factor receptor is under transcriptional control, is p140(trk)-, Ras-, and Src-dependent, and may involve transcriptional repression by GCF2.

Animals↗
PubMed1998

Development of porous apatite ceramic for local delivery of chemotherapeutic agents.

An experimental study was conducted on a drug delivery system (DDS), using porous apatite ceramics (PAC): hydroxyapatite block (HAb) [Ca10(PO4)6(OH)2] having a porosity of 35-48% and pore size range of 50-300 microm, and beta-tricalcium phosphate block (TCP) [Ca3(PO4)2] having a porosity of 75-80% and pore size range of 100-400 microm, for sustained release of a chemotherapeutic agent. Methotrexate (MTX) was loaded in the pores of PAC blocks by centrifuging the blocks in MTX solution. Impregnation of MTX in PAC blocks (1 cm3) was confirmed by a magnetic resonance imaging (MRI) study using Gadolinium-DTPA enhancement. The MRI showed high signal intensity in the PAC, which was confirmed by dye loading into the pores. To estimate the MTX-releasing capability of the PAC, the blocks were stored in 3 mL of phosphate-buffered saline (PBS) at 37 degrees C and the PBS was replaced every 48 h. The amount of MTX released was assayed by high-performance liquid chromatography. This study showed that MTX-impregnated PAC (0.63-2.25 mg/block) released the drug in a steady manner and maintained its concentration (0.1-1.0 microg/mL) up to 12 days. This concentration is high enough to be effective against tumor cells. Chemotherapeutic agent-impregnated PAC, prepared by simple centrifugation, could be a valuable form of local chemotherapy when used as a strut graft to repair bone defects. This new DDS material could also be used as an adjuvant to extended curettage and provide a means to reduce the recurrence of tumors without risk of systemic toxicity.

Antimetabolites, Antineoplastic↗
PubMed1998

Involvement of tyrosine phosphorylation in inhibition of fMLP-induced PLD activation by N-acetyl-L-cysteine in differentiated HL60 cells.

N-acetyl-L-cysteine (NAC), which is known as a multipotential agent; an antioxidant, a thiol reagent, or a tyrosine kinase inhibitor, inhibited N-formyl-methionyl-leucyl-phenylalanine (fMLP)-induced phospholipase D (PLD) activation in HL60 cells in a concentration-dependent manner (IC50 = 2 mM). Its inhibitory mechanism was examined in this study to gain insight into the regulation of PLD activity. NAC had no direct effect on membrane PLD activity in an in vitro assay system. fMLP-induced formation of inositol phosphates via phospholipase C (PLC) was not affected by the drug, suggesting that the receptor-G protein coupling was not inhibited. H2O2, which is known to induce PLD activation in several types of cells, failed to activate PLD in HL60 cells. Pretreatment of 3-amino-1,2,4-triazole (ATZ), a catalase inhibitor, did not enhance fMLP-induced PLD activation. NAC inhibited fMLP-induced tyrosine phosphorylation of several protein bands (42, 44, 64, and 138 kDa) in a concentration-dependent manner. The temporal and concentration-dependent inhibitory profiles for tyrosine phosphorylation of 64- and 138-kDa proteins were well correlated with PLD activation. However, thiol reagents, 1 mM 2,3-dimercapto-l-propanol (2,3-DMP), 1 mM dithiothreitol (DTT), and 2 mM cysteine also did not suppress protein tyrosine phosphorylation or PBut formation by fMLP. Wortmannin, a selective phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor, inhibited these two tyrosine phosphorylation bands. These results suggest that NAC inhibits fMLP-induced PLD activation through blockage of protein tyrosine phosphorylation, which is located at the downstream of PI-3 kinase.

Acetylcysteine↗
PubMed1998

Influence of intermittent ischemia on thioacetamide-induced rat liver cirrhosis.

We studied the influence of intermittent ischemic injury on thioacetamide-induced liver cirrhosis in rats. Wistar rats were divided into group A, intermittent ischemic injury to liver cirrhosis, and group B, continuous ischemic injury to liver cirrhosis. Total ischemic time was 60 min in both groups. In group A, ischemic injury consisted of a repetition 4 times of 15 min ischemia and 5 min reperfusion. The ATP level of the liver was measured before ischemia, before reperfusion, and 60 min after reperfusion. Bile was collected to determine bile flow rate. The ATP level in the liver tissue 60 min after reperfusion was significantly (p < 0.05) higher in group A than in group B. The ATP level immediately before reperfusion was also significantly (p < 0.05) higher in group A than in group B. The survival rate 1 week after ischemic injury and bile flow rate 60 min after reperfusion were significantly (p < 0.01) higher in group A compared with those in group B. The energy level was much higher in intermittent ischemic injury than in continuous ischemic injury immediately before reperfusion and after reperfusion. Survival rate and bile flow rate were higher in intermittent ischemic injury than in continuous ischemic injury. Therefore it suggests that the viability of the liver was maintained better in intermittent ischemic injury than in continuous ischemic injury.

Adenosine Triphosphate↗