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Biomedical subjects

Y Fujioka

Publications and source records attributed to Y Fujioka.

At least 55 records · Page 3Linked to original sources
PubMed1998

Lysophosphatidic acid-induced association of SHP-2 with SHPS-1: roles of RHO, FAK, and a SRC family kinase.

SHPS-1 is an approximately 120 kDa glycosylated receptor like protein that contains three immunoglobulin-like domains in its extracellular region as well as four potential tyrosine phosphorylation and SRC homology 2 (SH2) domain binding sites in its cytoplasmic region. Lysophosphatidic acid (LPA) stimulated the rapid tyrosine phosphorylation of SHPS-1 and its subsequent association with SHP-2, a protein tyrosine phosphatase containing SH2 domains in Rat-1 fibroblasts. LAP-induced tyrosine phosphorylation of SHPS-1 was inhibited by Clostridium botulinum C3 exoenzyme (which inactivates RHO) but not by pertussis toxin. The protein kinase C activator phorbol ester, 12-O-tetradecanoylphorbol 13-acetate (TPA) also stimulated tyrosine phosphorylation of SHPS-1; however, down-regulation of protein kinase C by prolonged exposure of cells to TPA did not affect LAP-induced tyrosine phosphorylation of SHPS-1. LPA-induced tyrosine phosphorylation of SHPS-1 was markedly reduced in either focal adhesion kinase (FAK)-deficient mouse cells or CHO cells overexpressing the tyrosine kinase CSK. Overexpression of a catalytically inactivate SHP-2 markedly inhibited MAP kinase activation in response to low concentrations of LPA in CHO cells, whereas overexpression of a wild-type SHPS-1 did enhance this effect of LPA. Furthermore, MAP kinase activation in response to a low concentration of LPA was inhibited by botulinum C3 exoenzyme. These results indicate that LPA-induced tyrosine phosphorylation of SHPS-1 and its association with SHP-2 may be mediated by a RHO-dependent pathway that includes FAK and a SRC family kinase. Thus, in addition to its role in receptor tyrosine kinase-mediated MAP kinase activation, the formation of a complex between SHPS-1 and SHP-2 may, in part, play an important role in the activation of MAP kinase in response to low concentrations of LPA.

ADP Ribose Transferases↗
PubMed1998

Interaction of the Na+-K+ pump and Na+-Ca2+ exchange via [Na+]i in a restricted space of guinea-pig ventricular cells.

1. The whole-cell Na+-K+ pump current (INa-K) and Na+-Ca2+ exchange current (INa-Ca) were recorded in guinea-pig ventricular myocytes to study the interaction between the two Na+ transport mechanisms. 2. INa-K was isolated as an external K+-induced current, and INa-Ca as an external Ca2+- induced or Ni2+-sensitive current. The experimental protocol used for one ion carrier did not affect the other. 3. The amplitude of INa-K decreased to 54 +/- 17 % of the initial peak during continuous application of K+ with 20 mM Na+ in the pipette. The outward INa-Ca, which was intermittently activated by brief applications of Ca2+, decreased during activation of INa-K, and recovered after cessation of INa-K activation. These findings revealed a dynamic interaction between INa-K and INa-Ca via a depletion of Na+ under the sarcolemma. 4. To estimate changes in Na+ concentration ([Na+]i) under the sarcolemma, the reversal potential (Vrev) of INa-Ca was measured. Unexpectedly, Vrev hardly changed during activation of INa-K. However, when INa-Ca was blocked by Ni2+ at the same time that INa-K was activated, Vrev changed markedly, maximally by +100 mV, immediately after the removal of Ni2+ and K+. 5. Subsarcolemmal [Na+]i was calculated from the Vrev of INa-Ca on the assumption that the subsarcolemmal Ca2+ concentration ([Ca2+]i) was fixed with EGTA, and mean [Na+]i was calculated from both the time integral of INa-K and the cell volume. The subsarcolemmal [Na+]i was about seven times greater than the mean [Na+]i. 6. The interaction between the Na+-K+ pump and Na+-Ca2+ exchange was well simulated by a diffusion model, in which Na+ diffusion was restricted to one-seventh (14 %) of the total cell volume.

Animals↗
PubMed1998

Integrin-mediated tyrosine phosphorylation of SHPS-1 and its association with SHP-2. Roles of Fak and Src family kinases.

SHPS-1 is a receptor-like glycoprotein that undergoes tyrosine phosphorylation and binds SHP-2, an Src homology 2 domain containing protein tyrosine phosphatase, in response to various mitogens. Cell adhesion to extracellular matrix proteins such as fibronectin and laminin also induced the tyrosine phosphorylation of SHPS-1 and its association with SHP-2. These responses were markedly reduced in cells overexpressing the Csk kinase or in cells that lack focal adhesion kinase or the Src family kinases Src or Fyn. However, unlike Src, focal adhesion kinase did not catalyze phosphorylation of the cytoplasmic domain of SHPS-1 in vitro. Overexpression of a catalytically inactive SHP-2 markedly inhibited activation of mitogen-activated protein (MAP) kinase in response to fibronectin stimulation without affecting the extent of tyrosine phosphorylation of focal adhesion kinase or its interaction with the docking protein Grb2. Overexpression of wild-type SHPS-1 did not enhance fibronectin-induced activation of MAP kinase. These results indicate that the binding of integrins to the extracellular matrix induces tyrosine phosphorylation of SHPS-1 and its association with SHP-2, and that such phosphorylation of SHPS-1 requires both focal adhesion kinase and an Src family kinase. In addition to its role in receptor tyrosine kinase-mediated MAP kinase activation, SHP-2 may play an important role, partly through its interaction with SHPS-1, in the activation of MAP kinase in response to the engagement of integrins by the extracellular matrix.

Animals↗
PubMed1998

Roles of the complex formation of SHPS-1 with SHP-2 in insulin-stimulated mitogen-activated protein kinase activation.

SHPS-1 is a receptor-like protein that undergoes tyrosine phosphorylation and binds SHP-2, an SH2 domain-containing protein tyrosine phosphatase, in response to insulin and other mitogens. The overexpression of wild-type SHPS-1, but not of a mutant SHPS-1 in which all four tyrosine residues in its cytoplasmic region were mutated to phenylalanine, markedly enhanced insulin-induced activation of mitogen-activated protein kinase in Chinese hamster ovary cells that overexpress the human insulin receptor. Mutation of each tyrosine residue individually revealed that the major sites of tyrosine phosphorylation of SHPS-1 in response to insulin are Tyr449 and Tyr473. In addition, mutation of either Tyr449 or Tyr473 abolished the insulin-induced tyrosine phosphorylation of SHPS-1 and its association with SHP-2. Surface plasmon resonance analysis showed that glutathione S-transferase fusion proteins containing the NH2-terminal or COOH-terminal SH2 domains of SHP-2 bound preferentially to phosphotyrosyl peptides corresponding to the sequences surrounding Tyr449 or Tyr473, respectively, of SHPS-1. Furthermore, phosphotyrosyl peptides containing Tyr449 or Tyr473 were effective substrates for the phosphatase activity of recombinant SHP-2 in vitro. Together, these results suggest that insulin may induce phosphorylation of SHPS-1 at Tyr449 and Tyr473, to which SHP-2 then binds through its NH2-terminal and COOH-terminal SH2 domains, respectively. SHPS-1 may play a crucial role both in the recruitment of SHP-2 from the cytosol to a site near the plasma membrane and in increasing its catalytic activity, thereby positively regulating the RAS-mitogen-activated protein kinase signaling cascade in response to insulin.

Amino Acid Sequence↗
PubMed1998

Adenoma with clear cell change of the large intestine.

BACKGROUND AND OBJECTIVES: Clear cell change of the large intestinal neoplasm is rare, and its character remains unclear. We report a case of the large intestinal adenoma with clear cell change with immunohistochemical and molecular studies to investigate whether the clear cell change is associated with a malignant progression of the adenoma. METHODS: We studied the histochemical and immunohistochemical staining characteristics of the tumor by staining with hematoxylin-eosin, periodic acid-Schiff, alcian blue, and by immunostaining using antibodies against carcinoembryonic antigen, epithelial membrane antigen, p53, and Ki-67. The c-K-ras codon 12 point mutations were analyzed using a nonradioactive restriction fragment length polymorphism technique. RESULTS: The tumor was composed of a typical tubular adenoma and a tubular adenoma with clear cytoplasm. The clear cytoplasm was negative by mucin stains. Immunohistochemically p53 was negative in both the components. Labeling index of Ki-67 showed no significant difference between the two components. No codon 12 mutation of c-K-ras gene was observed in both the components. CONCLUSION: These findings suggest that the clear cell change of the tubular adenoma is not associated with a malignant progression in adenoma-carcinoma sequence involving c-K-ras and p53.

Adenoma↗
PubMed1998

Cyclin D1 gene amplification in esophageal carcinosarcoma shown by differential polymerase chain reaction.

We studied cyclin D1 gene amplification in four esophageal carcinosarcomas using the differential polymerase chain reaction. Three cases showed amplification in the sarcomatous components, and one of these also showed amplification in the carcinomatous component. No amplification was detected in the other case. We also examined p53 expression in these four tumors by immunostaining. Both components of all four cases showed diffuse overexpression of p53 protein in the nuclei. Our results showed that the cyclin D1 gene is frequently amplified in esophageal carcinosarcoma, especially in the sarcomatous component. Two cases showed amplification only in the sarcomatous component, suggesting that amplification may have a role in the pathogenesis of that component of this malignancy. The diffuse overexpression of p53 observed in both components suggests that such overexpression, which could be the result of somatic mutation, might be an early event in the pathogenesis of esophageal carcinosarcoma.

Blotting, Southern↗
PubMed1998

Contrast-enhancement for the image of human immunodeficiency virus from ultrathin section by immuno electron microscopy.

A simple contrast-enhancement method is described for electron microscopic imaging of the human immunodeficiency virus (HIV) from a sample embedded in Lowicryl K4M resin, by immuneelectron microscopy. Ultrathin sections were treated with a mixture of ruthenium red dye (RR) and osmium tetroxide (OSO4). This treatment provided good contrast enhancement of the entire ultrastructural image of virus particles without the loss of immunolabelling. RR/OsO4 solution is simple to prepare and provides a better contrast than that which is achieved during conventional post-embedding immunoelectron microscopy. Treatment of ultrathin sections from low temperature-embedded samples with RR/OsO4 solution is recommended.

Cell Line↗
PubMed1998

Deletion of the p16 gene and microsatellite instability in carcinoma arising in pleomorphic adenoma of the parotid gland.

Carcinoma arising in pleomorphic adenoma of the salivary gland is a rare tumor, and its molecular aspects are unknown. Recent studies have revealed that malignant transformation of various human cancers may involve two different genetic alterations: inactivation of the p16 gene, which is a putative tumor suppressor gene, and genetic instability represented by microsatellite instability (MSI). However, so far, molecular investigations including p16 gene alteration and MSI have not been performed on carcinoma arising in pleomorphic adenoma. Both inactivation of the p16 gene and MSI were studied using DNA extracted from paraffin-embedded sections of carcinoma arising in pleomorphic adenoma. Samples also were analyzed for cyclin D1 gene amplification, which is thought to have oncogenic effects similar to those with inactivation of the p16 gene. One case showed the homozygous deletion of the p16 gene in the carcinoma, although hypermethylation of the p16 gene and amplification of the cyclin D1 gene were not observed in any cases. In two of four cases, MSI was observed. One case in two showed MSI in both the pleomorphic adenoma and the carcinoma. Results of this study suggest that two different genetic alterations, the inactivation of the p16 gene and genetic instability, play roles in the malignant transformation of carcinoma in pleomorphic adenoma. The MSI observed in the adenoma suggests that genetic alterations occur in pleomorphic adenoma.

Adenocarcinoma↗
PubMed1998

Cyclin D1 gene amplification and p16 gene deletion in patients with esophageal carcinosarcoma.

Cyclin D1 (CD1) gene amplification is frequently observed in esophageal carcinosarcoma by differential polymerase chain reaction (DPCR). In this study, fluorescence in situ hybridization (FISH) was performed to show more direct evidence of CD1 gene amplification in patients with esophageal carcinosarcoma. FISH results were also compared with DPCR results studied previously. FISH analysis revealed CD1 gene amplification in all four patients with esophageal carcinosarcoma. CD1 gene amplification occurred with a high incidence in both components of esophageal carcinosarcoma, suggesting that CD1 gene amplification could have an important role in malignant transformation processes of esophageal carcinosarcoma. The results of the current study also suggest that FISH is a more sensitive method than DPCR. Because inactivation of p16 gene (which is a putative tumor suppressor gene) is thought to have similar oncogenic effects with CD1 gene amplification, DPCR was used to examine whether p16 homozygous deletion occurs in esophageal carcinosarcoma. These results suggest that homozygous deletion of the p16 gene occurs less frequently than CD1 gene amplification in esophageal carcinosarcoma. It does not seem to be an alternative event to CD1 gene amplification, though the number of studied cases was small.

Aged↗
PubMed1998

Idiopathic retroperitoneal fibrosis with duodenal obstruction successfully treated with corticosteroids.

We report a case of idiopathic retroperitoneal fibrosis presenting with duodenal obstruction. A 55-year-old man suddenly developed severe epigastric pain and was admitted to our hospital. On abdominal computed tomography (CT), a large retroperitoneal mass was found. Hypotonic duodenography showed obstruction of the third portion of the duodenum. He was diagnosed as idiopathic retroperitoneal fibrosis and was treated with prednisolone. The patient improved dramatically. He has been well for twelve months without any further treatment.

Duodenal Obstruction↗
PubMed1998

Staphylococcus aureus causing chorioamnionitis and fetal death with intact membranes at term. A case report.

BACKGROUND: Neonatal infection without premature rupture of amniotic membranes occurs in 1-2% of births. The prevalence of membrane inflammation among term births is approximately 10%. There has been only one case report of Staphylococcus aureus as the cause of chorioamnionitis with intact membranes. CASE: A 24-year-old woman was admitted at 38 weeks of pregnancy with labor pains. On admission, she had a slight fever of 37.8 degrees C, but the other physical findings were within normal limits. There were no symptoms or signs of membrane rupture. Fetal heart monitoring showed slight tachycardia, 160 beats per minute, and loss of variability. Fetal death was detected when the fetal monitoring was resumed after being interrupted for 30 minutes. A male infant weighing 2,920 g was born dead. Artificial rupture of the membranes had been performed just before delivery. CONCLUSION: Culture specimens from the placenta and cord blood showed growth of S aureus, and histologic examination revealed chorioamnionitis. The bacteriologic evidence from the infant clearly identified S aureus.

Adult↗
PubMed1998

[Experience in managing refractory status epilepticus caused by viral encephalitis under long-term anesthesia with barbiturate: a case report].

This is a case study in managing refractory status epilepticus under long-term usage of secobarbital (SB). The patient is a 26-year-old woman with viral encephalitis. Fifteen days after the onset of the disease, status epilepticus with complex partial seizures began. The seizures were so refractory to conventional anti-epileptic drugs, such as valproate, carbamazepine, phenytoin, phenobarbital, clonazepam, lorazepam and lidocaine, that we had to put her on anesthesia with SB for approximately 10 months. Finally, we stopped the administration of SB and support for ventilation; we reduced the dose of SB extremely slowly, using zonisamide at the same time. After trial and error, we found that a reduction of the dosage after long-term anesthesia with high-dose administrations of barbiturate should be made very slowly.

Adjuvants, Anesthesia↗
PubMed1998

Multiple processes are involved in the uptake of chylomicron remnants by mouse peritoneal macrophages.

The processes responsible for the uptake of chylomicron remnants by macrophages were investigated using freshly isolated cells from low density lipoprotein (LDL) receptor, very low density lipoprotein (VLDL) receptor and apolipoprotein E knockout mice. In peritoneal macrophages from normal mice, the metabolism of chylomicron remnants was inhibited 40% by anti-LDL receptor antibody and 60% by a high concentration of receptor-associated protein (RAP). Together they reduced the amount processed by 70%. Digestion of cell proteoglycans decreased remnant degradation by 20% while the addition of acetyl-LDL had no effect. When LDL receptors were absent, the absolute rates of metabolism were less than that of normal cells and were not inhibited by the anti-LDL receptor antibody; the rates, however, were reduced to less than half by RAP. These suggest that the LDL receptor-related protein (LRP) or another LDL receptor family member(s) contributes to chylomicron remnant uptake and becomes the major mechanism of uptake when LDL receptors are absent. In contrast, the VLDL receptor was not involved as its absence did not affect chylomicron remnant metabolism. Similarly, the absence of apoE production did not affect the amount of remnant uptake; however, the proportion that was sensitive to RAP was eliminated. The level of LRP expression was not altered in these cells whereas there was a decrease in LDL receptors. This suggests that the apoE content of chylomicron remnants is sufficient for its recognition by LDL receptors but additional apoE is required for its uptake by the LRP and that there is an up-regulation of a non-LDL receptor family mechanism in apoE deficiency. Together these studies suggest that even in the absence of LDL receptors or apoE secretion, chylomicron remnants could contribute to lipid accumulation in the artery wall during atherogenesis.

Animals↗
PubMed1997

Epidermal growth factor stimulates the tyrosine phosphorylation of SHPS-1 and association of SHPS-1 with SHP-2, a SH2 domain-containing protein tyrosine phosphatase.

SHPS-1 is a 120 kDa glycosylated receptor-like protein that contains immunoglobulin-like domains in its extracellular region and four potential tyrosine phosphorylation for SH2 domain binding sites in its cytoplasmic region. Epidermal growth factor (EGF) stimulated the rapid tyrosine phosphorylation of SHPS-1 and subsequent association of SHPS-1 with SHP-2, a protein tyrosine phosphatase containing SH2 domains, in Chinese hamster ovary cells overexpressing human EGF receptors. In the cells overexpressing SHPS-1, the tyrosine phosphorylation of SHPS-1 was more evident than that observed in parent cells. However, overexpression of SHPS-1 alone did not affect the activation of MAP kinase in response to EGF. These results suggest that SHPS-1 may be involved in the recruitment of SHP-2 from the cytosol to the plasma membrane in response to EGF.

Animals↗
PubMed1997

SP-22 is a thioredoxin-dependent peroxide reductase in mitochondria.

SP-22 is a mitochondrial antioxidant protein in bovine adrenal cortex. The protein is homologous to thioredoxin peroxidase and other antioxidant proteins. It protects radical-sensitive enzymes from oxidative damage by a radical-generating system (Fe2+/dithiothreitol) in the presence of a small amount of serum. In this study we purified a second mitochondrial protein with Mr 11,777, which cooperates with SP-22 to protect glutamine synthetase and other proteins from Fe2+/dithiothreitol-mediated damage. Without SP-22, the protein had no protecting activity. We determined amino acid and nucleotide sequences of the protein and its cDNA, respectively, and found that it was a protein of the thioredoxin family. The protein, designated as mt-Trx (mitochondrial thioredoxin), had a presequence composed of 59 amino acids that seemed to be a mitochondrial targeting signal. Mitochondrial extract prepared from adrenal cortex contained NADPH-dependent 5,5'dithiobis(2-nitrobenzoic acid) (Nbs2) reductase activity. The enzyme was thought to have thioredoxin reductase activity, since the Nbs2-reducing activity was stimulated by mt-Trx. We partially purified the Nbs2 reductase from bovine adrenocortical mitochondria. In the presence of the partially purified reductase, mt-Trx, and NADPH, SP-22 showed the activity to protect oxyhemoglobin against ascorbate-induced damage. Furthermore, with the three protein components (Nbs2 reductase, mt-Trx, and SP-22) NADPH was oxidized in the presence of hydrogen peroxide or tert-butyl hydroperoxide. The oxidation of NADPH was concomitant with the disappearance of an equimolar amount of hydrogen peroxide. Without any one of the protein components no hemoglobin-protecting and peroxide-dependent NADPH-oxidizing activities were observed. From these results we concluded that SP-22 is thioredoxin-dependent peroxide reductase or so-called thioredoxin peroxidase in mitochondria from the adrenal cortex.

Adrenal Cortex↗
PubMed1997

A high-density STS map based on a single contig of YAC and P1 clones in the chromosome 8p12-p21 region.

We have constructed a yeast artificial chromosome (YAC) and P1 contig in the 8p12-p21 region. The contig comprises 16 overlapping YAC clones and 44 overlapping P1 clones. Twelve dinucleotide-repeat polymorphic sequence-tagged site (STS)-markers that were previously isolated mainly from these YAC and P1 clones were genetically mapped. A total of 46 nonpolymorphic STS markers were newly established mainly from the YAC and P1 clone end fragments, and 28 of the 46 nonpolymorphic STSs, as well as the 12 polymorphic STSs, were also mapped physically onto the contig based on STS content analysis of YAC pools and of the P1 and YAC clones. As a result, the YAC and P1 clones were assembled into a single contig covering a minimum of 1.5 Mb physically and 2.8 cM genetically with 12 polymorphic and 28 nonpolymorphic STSs within the 8p12-p21 region. Average STS spacing in the contig was estimated to be 40 kb/STS. In addition, further characterization of the contig suggested that this contig includes a region where genetic recombination occurs frequently. Thus, the resulting cloned region, together with densely mapped STS markers on the contig, should help to promote our understanding of this region.

Bacteriophage P1↗
PubMed1997

Mouse and human SHPS-1: molecular cloning of cDNAs and chromosomal localization of genes.

SHPS-1 (SHP substrate-1) is a glycosylated receptor-like protein with three immunoglobulin-like domains in its extracellular region and four YXX(L/V/I) motifs, potential tyrosine phosphorylation and SRC homology 2 (SH2) domain binding sites, in its cytoplasmic region. Various mitogens and cell adhesion induce tyrosine phosphorylation of SHPS-1 and its subsequent association with SHP-2, and SH2 domain-containing protein tyrosine phosphatase, suggesting that SHPS-1 plays a role in cell signaling in response to both growth factors and cell adhesion. The mouse and human cDNAs encoding SHPS-1 have now been isolated. The deduced amino acid sequences of rat, human, and mouse SHPS-1 show identities of 65 to 81%. In addition to the SH2 domain binding sites, a proline-rich putative SH3 domain binding site was detected in the cytoplasmic region of SHPS-1. Northern blot analysis revealed that human SHPS-1 mRNA is most abundant in brain and that the mouse mRNA is present in embryos as early as day 7. Fluorescence in situ hybridization localized the SHPS-1 gene to human chromosome 20p13 and the F3 band of mouse chromosome 2. Furthermore, interspecific backcross analysis placed the mouse SHPS-1 locus 5.0 centimorgans distal and 1.4 centimorgans proximal to the microsatellite markers D2Mit63 and D2Mit19, respectively, in a region associated with the mutations coloboma (Cm), lethal milk (lm), and well-haarig (we).

Amino Acid Sequence↗