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M Muramatsu

Publications and source records attributed to M Muramatsu.

At least 73 records · Page 4Linked to original sources
PubMed2001

[Fawn-Hooded Rat; an animal model of development of pulmonary hypertension].

The Fawn-Hooded Rat (FHR) spontaneously develops pulmonary hypertension (PH) at sea level, and an increased severity of this disease is observed upon exposure to mild hypoxia. A recent report suggested that lung hypoplasia with decreased alveolarization and altered vascular growth led by the decreased activity of endothelial nitric oxide synthase may contribute to the development of PH in the FHR. Exposure to mild hypoxia (P1O2 = 120 mmHg) leads to severe PH in FHR but not in Tester Moriyama rat, a strain that has a serotonin platelet storage-pool deficiency (PSPD) similar to that of the FHR. A serotonin PSPD does not appear to predispose FHR to PH. Endothelin-1 (ET-1) mRNA and peptide levels are increased in the hypertensive lungs of mildly hypoxic FHR. ET-1 may at least partly contribute to the development of PH in this strain.

Animals↗
PubMed2001

Late detection of supraclinoid carotid artery aneurysm after traumatic subarachnoid hemorrhage and occlusion of the ipsilateral cervical internal carotid artery.

BACKGROUND AND PURPOSE: We report the first case of traumatic aneurysm of the supraclinoid internal carotid artery (ICA), which we speculate may have developed or grown after traumatic occlusion of the ipsilateral cervical ICA. CASE DESCRIPTION: A 26-year-old man presented with severe traumatic subarachnoid hemorrhage (SAH) and occlusion of the right cervical ICA after a motor vehicle accident. Three-dimensional CT angiography on admission showed no aneurysm. However, cerebral angiography 3 weeks after the injury showed a large aneurysm of the right supraclinoid ICA. The aneurysm was trapped, and pathological examination showed that it was a traumatic aneurysm. CONCLUSIONS: In this case we cannot be sure that the aneurysm was not present on admission. In view of the significant SAH, a lesson of this case may be to suspect such an aneurysm early on and perform early diagnostic cerebral angiography.

Accidents, Traffic↗
PubMed2001

Cancer-associated myofibroblasts possess various factors to promote endometrial tumor progression.

Myofibroblastic invasion associated with malignant epithelial cells of endometrial cancer as well as other cancers is often found in the interstitium. To assess the myofibroblastic-epithelial interaction, frozen sections from a total of 10 endometrial cancers with or without invasive myofibroblasts were immunohistochemically examined. Interestingly, the invasive myofibroblasts adjacent to malignant epithelial cells showed frequently intensive positive staining of several growth factors such as vascular endothelial growth factor (VEGF), insulin-like growth factor I, and epidermal growth factor, the cognate receptors such as Fetal liver kinase-1/Kinase Insert Domain-containing receptor/VEGF receptor-2, fms-like tyrosine kinase-1/VEGF receptor-1, and epidermal growth factor receptor, several cell cycle regulators such as cyclins and cyclin dependent kinases, and estrogen receptor alpha. Moreover, we indicated that the majority of the myofibroblasts as well as cancer epithelial cells are proliferating because of their positive staining of proliferating cell nuclear antigen and Ki-67. Furthermore, the myofibroblasts were also positive of hypoxia-inducible factor 1 alpha, which is a marker protein of hypoxia, probably followed by activation of VEGF-Flk-1 and VEGF-fms-like tyrosine kinase-1 signals, which could initiate angiogenesis. These findings suggest directly that the myofibroblasts might participate in the progression of tumor cells in terms of cancer cell growth stimulation and also activated initiation of angiogenesis.

Adult↗
PubMed2000

An estrogen receptor beta isoform that lacks exon 5 has dominant negative activity on both ERalpha and ERbeta.

An alternatively spliced isoform of human estrogen receptor beta (ERbeta) has been isolated from normal human testis mRNA that is coexpressed with wild-type ERbeta by reverse transcription polymerase chain reaction (RT-PCR). Sequence analysis of the ERbeta isoform PCR product reveals the absence of 139 bp that corresponds to the entire exon 5 of wild-type ERbeta, which predicts to lack part of the hormone-binding domain. The transient expression of the exon 5-deleted isoform of ERbeta (ERbetaDelta5) had no effect on basal transactivation activity of an estrogen-responsive luciferase reporter gene. This finding was in contrast to the previous reports that the exon 5-deleted isoform of ERalpha (ERalphaDelta5) acts as a dominant positive receptor, increasing basal gene transactivation itself. Moreover, when ERbetaDelta5 was cotransfected with the wild-type ERalpha or ERbeta, it behaved as a dominant negative receptor that inhibited not only estradiol-stimulated transactivation by ERbeta but also that by ERalpha. The ligand-independent nuclear localization of ERbetaDelta5 was confirmed by immunohistochemistry, and the coexpression of the isoform and the wild-type receptors could be observed in a single cell that transfected with both receptor cDNAs. These findings indicate that ERbetaDelta5 has a potential as a dominant negative receptor that blocks both ERalpha and ERbeta signaling pathways, suggesting some physiological roles of this isoform as an "ER inhibitor".

Alternative Splicing↗
PubMed2000

Interaction of the Unc-51-like kinase and microtubule-associated protein light chain 3 related proteins in the brain: possible role of vesicular transport in axonal elongation.

We identified two mammalian ULK1 (Unc-51-like kinase involved in neurite extension) binding proteins by yeast two-hybrid screening. Both proteins showed high structural similarity to microtubule-associated protein (MAP) light chain 3 (LC3). One is identical to the Golgi-associated ATPase Enhancer of 16 kDa (GATE-16), an essential factor for intra-Golgi transport [39]. The other is identical to the gamma 2-subunit of GABA-A receptor associated protein (GABARAP) which has a possible role in receptor transport [46]. Using the yeast two-hybrid system and the in vitro GST pull-down assay, we found that the N-terminal proline/serine rich (PS) domain of ULK1 (amino acid 287-416) is required for ULK1-GATE-16 and ULK1-GABARAP protein interactions. However, the kinase activity of ULK1 affected neither ULK1-GATE-16 nor ULK1-GABARAP interaction. Immunohistochemical analysis using ULK1 and GABARAP antibodies showed that the ULK1 and the GABARAP proteins co-localized to many kind of neurons such as pyramidal cells of the hippocampus, mitral cells of the olfactory bulb, and Purkinje cells of the cerebellum. In HeLa cells, endogenous ULK1 and tagged GABARAP showed punctate structures in the cytosol, and were colocalized. These results suggest that the interaction of ULK1 and GABARAP is important to vesicle transport and axonal elongation in mammalian neurons.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Isolation of a cDNA for a novel human RING finger protein gene, RNF18, by the virtual transcribed sequence (VTS) approach(1).

We have recently developed a novel database system, designated as the virtual transcribed sequence (VTS) which efficiently extracts many genes from public human genome databases, and tested the feasibility of this novel computational approach (N. Miyajima, C. Burge, T. Saito, Biochem. Biophys. Res. Commun. 272 (2000) 801; http://host45.maze.co.jp/vts/). In this study, using the VTS approach, we isolated a cDNA for a novel human gene with RING finger motif (C(3)HC(4)), which is not deposited in public EST databases. The isolated cDNA clone is 2163 bp in length, and contains an open reading frame of 452 amino acids. We designated the novel gene as RNF18. A database search showed that the RNF18 gene had the moderate similarity to SS-A/Ro52 protein, which is a ribonucleoprotein reactive with autoantibodies in patients with Sjögren's syndrome and systemic lupus erythematosus. Tissue distribution analyses by Northern blot and RT-PCR methods demonstrated that the RNF18 messenger RNA was preferentially expressed in testis. The exon-intron boundaries of RNF18 gene were determined by aligning the cDNA sequence with the corresponding genome sequence. The isolated cDNA consists of eight exons that span about 11 kb of the genome DNA. The precise chromosomal location of the RNF18 gene was determined by PCR-based radiation hybrid mapping, and the gene was located to centromere region of chromosome 11 between markers NIB1900 and D11S1350. Taken together, the VTS approach should provide a novel cDNA cloning strategy for isolating unidentified genes, which are not found even in EST databases but are detectable computationally.

Amino Acid Sequence↗
PubMed2000

Molecular cloning of ring finger protein 21 (RNF21)/interferon-responsive finger protein (ifp1), which possesses two RING-B box-coiled coil domains in tandem.

We have cloned the full length of a novel cDNA, named ring finger protein 21 (RNF21), composed of the RING finger-B box-coiled coil (RBCC) domain and the B30.2 domain, which are characteristic of the RBCC-B30.2 family. As a structural feature, the RNF21 cDNA possessed at least three kinds of isoforms, due to alternative splicing, consisting of the long form with the RBCC-RBCC-B30.2 domain, the medium form with the RBCC-B30.2 domain, and the short form with only the RBCC domain. Moreover, respective transcripts corresponding to the three isoforms were detected in various human organs by reverse transcription-PCR and Northern blot analyses. Interestingly, the medium form of the RNF21 mRNA expressed most predominantly was dramatically up-regulated within 8-16 h by interferon stimulation of HeLa cells. These findings suggest that RNF21 is a downstream gene that may mediate interferon's biological action.

Alternative Splicing↗
PubMed2000

Molecular cloning of testis-abundant finger Protein/Ring finger protein 23 (RNF23), a novel RING-B box-coiled coil-B30.2 protein on the class I region of the human MHC.

We have identified a genomic DNA fragment, using the PCR method with degenerate oligonucleotide primers which contain the conserved sequence of the RING finger domain. Using the DNA fragment as a probe, a novel cDNA was cloned from human and mouse testis. The cDNA had a domain structure of the typical RING-B box-coiled coil (RBCC)-B30.2 domain and therefore was named testis-abundant finger protein (tfp). Indeed, the transcript was highly expressed in the testis, although it was also found ubiquitously in various organs by Northern blot analysis. The tfp gene was mapped at the class I region of the human MHC (major histocompatibility complex), within which some known RBCC-B30.2 proteins such as RFP, RFB30/HERF1, AFP, and HZF had been localized. These findings demonstrate that several RBCC-B30.2 proteins including tfp, which are non-HLA proteins, are clustered within the class I region of the human MHC.

Amino Acid Sequence↗
PubMed2000

Class switch recombination and hypermutation require activation-induced cytidine deaminase (AID), a potential RNA editing enzyme.

Induced overexpression of AID in CH12F3-2 B lymphoma cells augmented class switching from IgM to IgA without cytokine stimulation. AID deficiency caused a complete defect in class switching and showed a hyper-IgM phenotype with enlarged germinal centers containing strongly activated B cells before or after immunization. AID-/- spleen cells stimulated in vitro with LPS and cytokines failed to undergo class switch recombination although they expressed germline transcripts. Immunization of AID-/- chimera with 4-hydroxy-3-nitrophenylacetyl (NP) chicken gamma-globulin induced neither accumulation of mutations in the NP-specific variable region gene nor class switching. These results suggest that AID may be involved in regulation or catalysis of the DNA modification step of both class switching and somatic hypermutation.

APOBEC-1 Deaminase↗
PubMed2000

Activation-induced cytidine deaminase (AID) deficiency causes the autosomal recessive form of the Hyper-IgM syndrome (HIGM2).

The activation-induced cytidine deaminase (AID) gene, specifically expressed in germinal center B cells in mice, is a member of the cytidine deaminase family. We herein report mutations in the human counterpart of AID in patients with the autosomal recessive form of hyper-IgM syndrome (HIGM2). Three major abnormalities characterize AID deficiency: (1) the absence of immunoglobulin class switch recombination, (2) the lack of immunoglobulin somatic hypermutations, and (3) lymph node hyperplasia caused by the presence of giant germinal centers. The phenotype observed in HIGM2 patients (and in AID-/- mice) demonstrates the absolute requirement for AID in several crucial steps of B cell terminal differentiation necessary for efficient antibody responses.

APOBEC-1 Deaminase↗
PubMed2000

Isolation of novel mouse genes differentially expressed in brain using cDNA microarray.

The major issue in the post-genome sequencing era is determination of gene expression patterns in variety of biological systems. A microarray system is a powerful technology for analyzing the expression profile of thousands of genes at one experiment. In this study, we identified highly expressed genes in mouse brain using the cDNA microarray carrying 2304 cDNAs derived from oligo-capped mouse cDNA library. Nine genes were highly expressed in adult mouse brain compared to kidney, liver, and skeletal muscle. Tissue distribution analysis by reverse transcription-coupled polymerase chain reaction (RT-PCR) revealed that consistent with the microarray data, all of the selected 9 genes were predominantly expressed in the brain. A database search showed that 5 of the 9 genes, MBP, SC1, HiAT3, S100 protein-beta, and SNAP25, were previously known to be expressed at high level in the brain and in the nervous system. One gene was highly sequenced similar to rat S-Rex-s/human NSP-C, suggesting that the gene is a mouse homologue. The remaining three genes did not match to known genes in the GenBank/EMBL database, indicating that these are novel genes highly expressed in the brain. Taken together, our cDNA microarray system can be an excellent tool for identifying differentially expressed genes in mouse brain.

Animals↗
PubMed2000

Chymase mediates mast cell-induced angiogenesis in hamster sponge granulomas.

We investigated the contribution of mast cell chymase in mast cell-dependent angiogenesis using the hamster sponge-implant model, where angiogenesis in the granulation tissue surrounding the subcutaneously implanted sponge was evaluated by measuring the hemoglobin content. Daily local injection of compound 48/80 (3-100 microg/site/day), a potent mast cell activator, induced formation of granulomas and angiogenesis in time- and dose-dependent manners. This angiogenic response was inhibited by chymase inhibitors including chymostatin (> or = 1 nmol/site/day), soybean trypsin inhibitor (SBTI; > or = 1.4 nmol/site/day) and lima bean trypsin inhibitor (LBTI; > or = 3.3 nmol/site/day), but not by a tryptase inhibitor like leupeptin (> or = 700 nmol/site/day). Although pyrilamine (> or = 2,580 nmol/site/day), a histamine H1 receptor antagonist, and protamine (300 microg/site/day) also inhibited angiogenesis, these effects were much less pronounced than those by chymase inhibitors. Furthermore, antigen-induced angiogenesis in hamsters pre-sensitized with ovalbumin was also inhibited by the chymase inhibitors by 60-70%. Our results suggest that chymase is a major mediator in mast cell-mediated angiogenesis.

Animals↗
PubMed2000

Isolation, tissue distribution, and chromosomal localization of the human activation-induced cytidine deaminase (AID) gene.

The gene encoding activation-induced cytidine deaminase (AID), a member of the cytidine deaminase family, was isolated from a murine B cell lymphoma line, CH12F3-2, induced by combined stimulation of TGF-beta, IL-4, and CD40L. We have isolated the human orthologue of mouse AID cDNA, which has an open reading frame of 198 residues containing a conserved cytidine deaminase motif. The amino acid sequence of human AID is 92% identical to that of mouse AID. RT-PCR analysis of 15 human tissues showed that AID mRNA is expressed strongly in lymph nodes and tonsils. The complete human AID gene consisting of five exons was isolated and mapped to chromosome 12p13 by fluorescence in situ hybridization.

Amino Acid Sequence↗
PubMed2000

p300-mediated acetylation facilitates the transfer of histone H2A-H2B dimers from nucleosomes to a histone chaperone.

We have used a purified recombinant chromatin assembly system, including ACF (Acf-1 + ISWI) and NAP-1, to examine the role of histone acetylation in ATP-dependent chromatin remodeling. The binding of a transcriptional activator (Gal4-VP16) to chromatin assembled using this recombinant assembly system dramatically enhances the acetylation of nucleosomal core histones by the histone acetyltransferase p300. This effect requires both the presence of Gal4-binding sites in the template and the VP16-activation domain. Order-of-addition experiments indicate that prior activator-meditated, ATP-dependent chromatin remodeling by ACF is required for the acetylation of nucleosomal histones by p300. Thus, chromatin remodeling, which requires a transcriptional activator, ACF and ATP, is an early step in the transcriptional process that regulates subsequent core histone acetylation. Glycerol gradient sedimentation and immunoprecipitation assays demonstrate that the acetylation of histones by p300 facilitates the transfer of H2A-H2B from nucleosomes to NAP-1. The results from these biochemical experiments suggest that (1) transcriptional activators (e.g., Gal4-VP16) and chromatin remodeling complexes (e.g., ACF) induce chromatin remodeling in the absence of histone acetylation; (2) transcriptional activators recruit histone acetyltransferases (e.g., p300) to promoters after chromatin remodeling has occurred; and (3) histone acetylation is important for a step subsequent to chromatin remodeling and results in the transfer of histone H2A-H2B dimers from nucleosomes to a histone chaperone such as NAP-1. Our results indicate a precise role for histone acetylation, namely to alter the structure of nucleosomes (e.g., facilitate the loss of H2A-H2B dimers) that have been remodeled previously by the action of ATP-dependent chromatin remodeling complexes. Thus, transcription from chromatin templates is ordered and sequential, with precise timing and roles for ATP-dependent chromatin remodeling, subsequent histone acetylation, and alterations in nucleosome structure.

Acetylation↗
PubMed2000

Impaired estrogen sensitivity in bone by inhibiting both estrogen receptor alpha and beta pathways.

Although it is well established that estrogen deficiency causes osteoporosis among the postmenopausal women, the involvement of estrogen receptor (ER) in its pathogenesis still remains uncertain. In the present study, we have generated rats harboring a dominant negative ERalpha, which inhibits the actions of not only ERalpha but also recently identified ERbeta. Contrary to our expectation, the bone mineral density (BMD) of the resulting transgenic female rats was maintained at the same level with that of the wild-type littermates when sham-operated. In addition, ovariectomy-induced bone loss was observed almost equally in both groups. Strikingly, however, the BMD of the transgenic female rats, after ovariectomized, remained decreased even if 17beta-estradiol (E(2)) was administrated, whereas, in contrast, the decrease of littermate BMD was completely prevented by E(2). Moreover, bone histomorphometrical analysis of ovariectomized transgenic rats revealed that the higher rates of bone turnover still remained after treatment with E(2). These results demonstrate that the prevention from the ovariectomy-induced bone loss by estrogen is mediated by ER pathways and that the maintenance of BMD before ovariectomy might be compensated by other mechanisms distinct from ERalpha and ERbeta pathways.

Animals↗
PubMed2000

Promoter analysis and chromosomal mapping of human EBAG9 gene.

The human EBAG9 was previously identified as an estrogen responsive gene using CpG-genomic binding site cloning (Watanate et al., (1998) Mol. Cell. Biol. 18: 442-449). Recently it was revealed that the EBAG9 is identical with RCAS1 which is a cancer cell surface antigen implicated in immune escape. Here, we isolated and analyzed the 5'-flanking region of human EBAG9 gene. We determined transcription initiation site, which has a homology with an initiator element YYCAYYYY, and found that TATA motif was absent. Deletion analysis of the 5'-flanking region using MCF-7 breast cancer cells indicated that the sequences -86 to -36 containing the ERE had the basal level of promoter activity and the upstream GC-rich region positively regulated the activity. EBAG9 promoter luciferase reporters containing the ERE could respond to estrogen, and electrophoretic mobility shift assay showed that ERalpha bound to the ERE. Moreover, fluorescent in situ hybridization analysis has shown that the human EBAG9 gene is located at chromosome 8q23 which is frequently amplified in tumors. These findings suggest that the human EBAG9 might be involved in carcinogenesis as an estrogen responsive gene.

Base Sequence↗