Search PubMed⌕ Search

Biomedical subjects

N Miyasaka

Publications and source records attributed to N Miyasaka.

At least 55 records · Page 3Linked to original sources
PubMed2000

A novel point mutation of the splicing donor site in the intron 2 of the plasmin inhibitor gene.

Plasmin inhibitor (PI) is a major physiological inhibitor of plasmin-mediated fibrinolysis; hence, its deficiency results in a severe haemorrhagic diathesis. We analyzed the PI gene of a French boy apparently homozygous for PI deficiency and his heterozygous parents. Both alleles of the homozygous patient had a novel G to A transition at the consensus splicing donor site in the intron 2 of the PI gene. In an expression assay using the heterologous cells transfected with the mutant PI expression vector, 3 types of aberrant transcripts using a cryptic splicing donor site within the intron 2 were detected. All of these mRNAs had a stop codon upstream of the cryptic splicing site and encode only 25 amino acids, comprising the first 21 amino acids of the signal peptide (27 amino acids) plus 4 new amino acids. This mutant was designated as PI-Paris-Trousseau.

Animals↗
PubMed2000

[Rheumatoid arthritis].

Explore the source record for details and available documents.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1999

CrkL mediates Ras-dependent activation of the Raf/ERK pathway through the guanine nucleotide exchange factor C3G in hematopoietic cells stimulated with erythropoietin or interleukin-3.

CrkL is an SH2 and SH3 domain-containing adaptor protein implicated in pathogenesis of chronic myelogenous leukemia. Here, we demonstrate that overexpression of CrkL enhances the erythropoietin (Epo)- or interleukin (IL)-3-induced activation of Elk-1 and the c-fos gene promoter activity in 32D/EpoR-Wt cells. Moreover, the Epo-induced activation of ERK1 and ERK2 was augmented and prolonged in cells inducibly overexpressing CrkL. A moderate increase in Epo-induced activation of JNK was also observed in cells overexpressing CrkL. Overexpression of C3G enhanced the Elk-1 activation synergistically with CrkL, while a C3G mutant lacking the guanine nucleotide exchange domain showed an inhibitory effect. Studies using a dominant negative Ha-Ras mutant demonstrated that the Elk-1 and ERK2 activation enhanced by CrkL and C3G was dependent on Ras. Consistent with this, the Epo-induced activation of Ras was augmented in cells inducibly overexpressing CrkL. Most importantly, a CrkL mutant defective in the SH2 or N-terminal SH3 domain showed an inhibitory effect on the Epo-induced activation of ERK2. These data indicate that the CrkL-C3G complex plays a role in Epo- or IL-3-induced, Ras-dependent activation of the Raf/ERK pathway leading to the activation of Elk-1 and the c-fos gene transcription.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Foreign gene expression in an organotypic culture of cortical anlage after in vivo electroporation.

A high level of foreign gene expression in organotypic cultures of the cerebral cortical anlage was achieved by electroporation-mediated gene transfer in vivo. A mammalian expression plasmid for green fluorescent protein (GFP) gene was injected into the lateral ventricle of rat embryos. Immediately after the plasmid DNA injection, the head of the embryo was electroporated between a pair of tweezer-type electrodes. The cortical anlage was isolated and maintained organotypically up to 21 days in vitro (DIV). The GFP-transgene was expressed intensely in neural progenitor cells at 1 DIV. GFP-expressing cells were still detectable and were demonstrated to differentiate into neurons and glia at 21 DIV. This system is expected to be useful for molecular analysis of cerebral cortical development and function.

Animals↗
PubMed1999

Signaling through the antigen receptor of B lymphocytes activates a p53-independent pathway of c-Myc-induced apoptosis.

Deregulated expression of c-Myc has been shown to induce or enhance apoptosis in various different cell types. c-Myc requires p53 for apoptosis in some but not all the cell types, indicating heterogeneous mechanisms for c-Myc-induced apoptosis. In B lymphoma line WEHI-231, stable expression of c-Myc has been demonstrated to protect cells from BCR-mediated apoptosis. However, stable expression of c-Myc carrying pro-apoptotic functions may generate variant cells resistant to apoptosis. By utilizing an inducible system for c-Myc, we demonstrated here that deregulated expression of c-Myc induced apoptosis of WEHI-231 by itself, indicating that c-Myc induces apoptosis in WEHI-231 as is the case for other cell types. When transactivation of p53 was inactivated, WEHI-231 cells overexpressing c-Myc no longer underwent apoptosis in the absence of other stimuli, but showed markedly enhanced apoptosis in the presence of BCR ligation. These results indicate that deregulated c-Myc expression enhances apoptosis by a p53-independent pathway in the presence of BCR signaling but requires p53 for apoptosis in the absence of BCR crosslinking in WEHI-231. BCR ligation may thus activate a p53-independent pathway of c-Myc-induced apoptosis.

Apoptosis↗
PubMed1999

CrkL activates integrin-mediated hematopoietic cell adhesion through the guanine nucleotide exchange factor C3G.

CrkL is a member of the Crk family of adapter proteins consisting mostly of SH2 and SH3 domains. CrkL is most abundantly expressed in hematopoietic cells and has been implicated in pathogenesis of chronic myelogenous leukemia. However, its function has not been precisely defined. Here, we show that overexpression of CrkL enhances the adhesion of hematopoietic 32D cells to fibronectin. The CrkL-induced increase in cell adhesion was blocked by antibodies against VLA-4 (alpha4beta1) and VLA-5 (alpha5beta1) but was observed without changes in surface expression levels of these integrins. Studies using CrkL mutants demonstrated that the SH2 domain is partially required for enhancing cell adhesion, whereas the C-terminal SH3 domain as well as the tyrosine phosphorylation site (Y207) is dispensable. In contrast, the N-terminal SH3 domain, involved in binding C3G and other signaling molecules, was showed to play a crucial role, because a mutant defective of this domain showed an inhibitory effect on the cell adhesion to fibronectin. Furthermore, overexpression of C3G also increased the adhesion of hematopoietic cells to fibronectin, whereas a C3G mutant lacking the guanine nucleotide exchange domain abrogated the CrkL-induced increase in cell adhesion. On the other hand, a dominant negative mutant of H-Ras or that of Raf-1 enhanced the basal and CrkL-induced cell adhesion and that of R-Ras modestly decreased the adhesion. Taken together, these results indicate that the CrkL-C3G complex activates VLA-4 and VLA-5 in hematopoietic cells, possibly by activating the small GTP binding proteins, including R-Ras, through the guanine nucleotide exchange activity of C3G.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Genomic organization and regulatory elements of the rat latexin gene, which is expressed in a cell type-specific manner in both central and peripheral nervous systems.

Latexin, a carboxypeptidase A inhibitor, is expressed in a cell type-specific manner in both central and peripheral nervous systems in the rat. In the neocortex, a specific subpopulation of neurons in layers V and VI expresses latexin. In the primary sensory ganglia, the expression is restricted to smaller diameter neurons. As a first step to clarify regulatory mechanisms underlying cell type-specific expression of latexin, we have determined the organization of the rat latexin gene and analyzed its regulatory elements. The latexin gene spans approximately 5.8 kb, and consists of six exons and five introns. Three transcription initiation sites were mapped. The upstream region lacks typical TATA or CAAT boxes but has several GC-rich sites. To assess promoter activity, the luciferase reporter gene fused to the 5'-flanking region (6.4 kb) of the latexin gene was transiently transfected into several cell lines. Luciferase activity was 2-8 times higher in latexin-expressing cells (PC12) than non-expressing cells (NS20 and L6). Deletion analysis with PC12 cells revealed that a core promoter is located between nucleotide positions -261 and -201 relative to the A of the initiation codon. Nerve growth factor (NGF)-responsive element(s) is located between positions -518 and -262, in which AP-1, AP-2 and NF-kappaB binding sites are found. Furthermore, we demonstrate that a 1.3 kb genomic fragment containing the first intron has transcriptional enhancing activity in PC12 cells. These results suggest that up and downstream regulatory elements are involved in the control of cell type-specific expression of latexin.

5' Untranslated Regions↗
PubMed1999

Physical interaction between interleukin-12 receptor beta 2 subunit and Jak2 tyrosine kinase: Jak2 associates with cytoplasmic membrane-proximal region of interleukin-12 receptor beta 2 via amino-terminus.

IL-12 is a heterodimeric cytokine, composed of p40 and p35 subunits, that exerts its biological effects by binding to specific cell surface receptors. Two human IL-12 receptor proteins, designated IL-12R beta 1 and IL-12R beta 2, have been previously identified. IL-12R beta 2 has box 1 motif, box 2 motif, and three tyrosine residues in its cytoplasmic domain. In response to IL-12, Jak2 and Tyk2, family members of Janus family protein tyrosine kinases, are phosphorylated in PHA-activated T lymphocytes. The present study demonstrates that Jak2 binds to the cytoplasmic membrane-proximal region of IL-12R beta 2, and box 2 motif and tyrosine residues in the cytoplasmic domain were not required for binding. The amino-terminus of Jak2 is necessary for association with IL-12R beta 2.

Amino Acid Substitution↗
PubMed1999

The proto-oncogene Bc16 inhibits apoptotic cell death in differentiation-induced mouse myogenic cells.

The Bc16 gene is located at chromosomal band 3q27, a breakpoint for translocation that frequently occurs in B cell lymphomas. Bc16 has been found to be preferentially expressed in germinal center B cells, and expression of this gene has been shown to be essential for germinal center formation in vivo. The physiological function of Bc16 and its role in lymphomagenesis, however, are not yet known. Since significant expression of Bc16 has been demonstrated in skeletal muscle, we have utilized a differentiation-inducible mouse myogenic cell line, C2C12, to elucidate the function of the Bc16 gene product. Expression of Bc16 mRNA was very low in growing myocytes, but was increased in differentiating myocytes cultured in serum-starved medium. Incubation of these cells with cytokines or chemicals that are known to block differentiation suppressed this increased Bc16 message abundance, indicating that Bc16 induction is related to the process of terminal differentiation in muscle cells. While a fraction of myocytes is known to undergo apoptosis after serum-starvation to induce differentiation, adenovirus-mediated overexpression of Bc16 enhanced the viability of the differentiating cells by preventing the apoptosis. High levels of Bc16 antisense mRNA expression induced substantial apoptosis during the differentiation of C2C12 cells, but this was effectively prevented by infection with adenovirus that expressed Bc16 sense mRNA. These results indicate that Bc16 acts to prevent apoptotic cell death in differentiating myocytes. The deregulation of expression of this antiapoptotic gene may also contribute to the development of B cell lymphomas.

Animals↗
PubMed1999

Relationship between Helicobacter pylori infection and histologic features of gastritis in biopsy specimens in gastroduodenal diseases, including evaluation of diagnosis by polymerase chain reaction assay.

We investigated the relationship between Helicobacter pylori infection and the histologic features of gastritis in gastroduodenal disease, and evaluated the diagnostic usefulness of the polymerase chain reaction (PCR) assay for the detection of H. pylori before and after eradication therapy. Endoscopic biopsy specimens from 81 patients with gastroduodenal disease were examined for the presence of H. pylori by culture and histologic examination. Histologic features of gastritis were classified according to the updated Sydney System, and results of the PCR assay were compared with those of histologic examination, using histologic scores. The density of H. pylori was significantly correlated with polymorphonuclear neutrophil activity and chronic inflammation. These findings suggest that the grades of infiltration of polymorphonuclear neutrophil cells and chronic inflammatory cells correspond to the density of H. pylori infection assessed by the updated Sydney System. Patients with positive results on PCR assay and negative results on histologic examination may have a low density of H. pylori because of severe atrophy in the gastric mucosa. Differences in results for the PCR assay and histologic examination were found in 2 of 12 patients in the detection of H. pylori after eradication therapy. According to the results of the PCR assay and histologic features before and after eradication, the gastric tissue-based PCR assay for H. pylori after eradication may be too sensitive to judge successful eradication of H. pylori.

Adolescent↗
PubMed1999

The role of Bcl6 in mature cardiac myocytes.

OBJECTIVE: The Bcl6 gene encodes a sequence-specific transcriptional repressor and is ubiquitously expressed in adult murine tissues including heart muscle. The objective of this study was to examine the role of Bcl6 in cardiac myocytes. METHOD: We developed Bcl6-deficient (Bcl6-/-) mice and histologically examined hearts from these mice. RESULTS: Massive myocarditis with eosinophilic infiltration occurred in Bcl6-/- mice after 4-6 weeks of age. Since expression of the Bcl6 gene was induced in normal cardiac myocytes after 2 weeks of age and thereafter detected through adulthood, loss of Bcl6 in mature cardiac myocytes may be related to the induction of eosinophilic myocarditis. To examine the effects of eosinophils from Bcl6-/- mice on normal hearts, bone marrow cells from Bcl6-/- mice were adoptively transferred into sublethally irradiated RAG1-deficient mice. Although massive eosinophilic infiltration was detected in conjunctivas and spleens from the chimeric mice, myocarditis was never observed. Electron microscopic analysis of cardiac myocytes from Bcl6-/- mice revealed a spectrum of degenerative changes prior to eosinophilic infiltration. CONCLUSION: Bcl6 maynot be essential for the maturation of cardiac myocytes but may play a role in protecting mature cardiac myocytes from eosinophilic inflammation.

Adoptive Transfer↗
PubMed1999

Induction of the p16INK4a senescence gene as a new therapeutic strategy for the treatment of rheumatoid arthritis.

Synovial tissue affected by rheumatoid arthritis is characterized by proliferation, which leads to irreversible cartilage and bone destruction. Current and experimental treatments have been aimed mainly at correcting the underlying immune abnormalities, but these treatments often prove ineffective in preventing the invasive destruction. We studied the expression of cyclin-dependent kinase inhibitors in rheumatoid synovial cells as a means of suppressing synovial cell proliferation. Synovial cells derived from hypertrophic synovial tissue readily expressed p16INK4a when they were growth-inhibited. This was not seen in other fibroblasts, including those derived from normal and osteoarthritis-affected synovial tissues. In vivo adenoviral gene therapy with the p16INK4a gene efficiently inhibited the pathology in an animal model of rheumatoid arthritis. Thus, the induction of p16INK4a may provide a new approach to the effective treatment of rheumatoid arthritis.

Adenoviridae↗
PubMed1999

Slow-fast form of atrioventricular nodal reentrant tachycardia with eccentric retrograde left-sided activation.

A case of atypical AV nodal reentrant tachycardia (AVNRT) with eccentric retrograde left-sided activation, masquerading as tachycardia using a left-sided accessory pathway, is reported. Initially, it appeared that the tachycardia was a typical slow-fast form of AVNRT. The earliest retrograde activation, however, was registered at a site approximately 3 cm from the coronary sinus orifice (left atrial free wall), indicating atypical AVNRT. Atrial tachycardia and orthodromic AV reciprocating tachycardia using an accessory AV pathway were excluded. Slow pathway ablation at the posteroseptal right atrium eliminated the tachycardia. It was suggested that the anterograde limb of the tachycardia circuit was a slow AV nodal pathway with typical posteroseptal location, whereas the retrograde limb was a long atrionodal pathway connecting the compact AV node and the left atrial free wall near the mid-coronary sinus.

Atrioventricular Node↗
PubMed1999

[A case of Takayasu's arteritis with ulcerative colitis diagnosed by carotodynia and MRI findings].

We experienced a case of Takayasu's arteritis (TA) with ulceritive colitis (UC) having the onset of carotodynia, not accompanied by ischemic symptoms. MRI findings of the neck demonstrated a thickening of the bilateral carotid artery walls. The patient was treated by prednisolone with a marked improvement in both clinical symptoms and MRI findings. The patient had a unique HLA haplotype reported to correlate with both TA and UC. Carotodynia is an early but pathognomonic symptom of TA and MRI is helpful for the early diagnosis of TA.

Adult↗