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Biomedical subjects

M Muramatsu

Publications and source records attributed to M Muramatsu.

At least 19 recordsLinked to original sources
PubMed1992

[Two-dimensional time-of-flight MR angiography of mediastinum and pulmonary hilar vessels: initial clinical experiences].

Two-dimensional time-of-flight magnetic resonance angiography (2D TOF MRA) of mediastinal and pulmonary hilar vessels was performed in 10 patients, seven men and three women with a mean age (range) of 65.7 (48-88) years. The rate of visualization of the vessels and the diagnostic ability of 2D TOF MRA were assessed in comparison with contrast-enhanced CT. A radiofrequency-spoiled gradient echo sequence (SPGR) was used during repeated breath-holding (8-27 seconds) in coronal (8 patients) and axial (2 patients) imaging planes on a 1.5 Tesla superconducting scanner under the following conditions: repetition time/echo time/flip angle/excitation: 25-33/7-8 ms/45 degrees/1, field-of-view: 30 x 30 cm, slice thickness: 2.5 mm, 32 slices, 256 (frequency) x 192 (phase) matrix, with gradient moment nulling technique. Visualization sufficient to enable diagnosis of the vascular lesion was obtained in 95 (52%) vessels, mere visualization in 63 (35%), and non-visualization in 24 (13%) of the 182 evaluable vessels. The rates of good visualization of pulmonary hilar vessels (26/86, 30%) and veins (26/48, 54%) were significantly lower than that of arteries (43/48, 90%, p < 0.05). The sensitivity and specificity of 2D TOF MRA were 77% (10/13) and 100% (83/83), respectively, in 96 evaluable vessels of nine patients. 2D TOF MRA of mediastium and pulmonary hili is clinically feasible, and may be useful because of its high specificity.

Aged↗
PubMed1992

Effect of stilbene derivatives on gastric H+, K(+)-ATPase.

The effect of naturally occurring hydroxystilbene, 3,3',4,5-tetrahydroxystilbene (piceatanol), and its derivatives on gastric H+, K(+)-ATPase was studied. Piceatanol inhibited H+, K(+)-ATPase in a dose-dependent manner. The 50% inhibition value was 4.3 x 10(-6) M. It was found from the kinetic study that the inhibition of the enzyme by piceatanol was competitive with respect to ATP and was noncompetitive with respect to K+. Piceatanol also effectively inhibited gastric acid secretion. However, methylation of phenolic hydroxy groups of piceatanol resulted in a complete loss of inhibition of the enzyme and acid secretion, suggesting the role of phenolic hydroxy groups in the inhibition. The study on hydroxystilbene derivatives also showed that phenolic hydroxy groups are important in the interaction with H+, K(+)-ATPase and that stilbenes with neighbouring hydroxy groups are the most effective inhibitors.

Adenosine Triphosphate↗
PubMed1992

The regulation of the murine Hox-2.5 gene expression during cell differentiation.

The mouse Hox-2.5 gene containing a Drosophila Antennapedia-type homeobox sequence is expressed in a spatially and temporally restricted manner during embryogenesis. We found that the mouse embryonal carcinoma cell line P19 expresses Hox-2.5 during differentiation by the treatment with retinoic acid (RA). Expression of the Hox-2.5 gene was not detected in undifferentiated P19 cells, but detected 72 hours after treatment with RA. In order to analyze this inductive response, we first identified the Hox-2.5 transcription initiation site and a possible promoter region. Subsequently, we prepared constructs containing various Hox-2.5 DNA fragments fused to a firefly luciferase reporter gene and transfected these into undifferentiated or differentiating P19 cells. These studies have demonstrated that a region -279 to +15 with respect to the transcription initiation site has a differentiation-responsive promoter activity. Deletion analysis suggests that the sequences responsible for this induction are located in several distinct domains within the 294 bp promoter region. Two of the possible differentiation-responsive elements were identified by analysis of DNA-protein interactions, and in vivo competition assays lend support to the notion that these regions are involved in the differential expression of Hox-2.5 promoter activity.

Animals↗
PubMed1992

Protein kinase C mutants in the auto-inhibitory region exhibit two distinct properties.

To define the role of the auto-inhibitory region of protein kinase C (PKC), Arg22-Lys23-Gly24-Ala25-Leu26-Arg27, site-directed mutations were introduced into the basic residues. Three mutants, PKCAla22,23, PKCAla27, and PKCAla22,23,27, apparently fell into two distinct types with regard to their biochemical properties and biological activities, as judged by the enhancement of a c-fos promoter in Jurkat cells and by the initiation of germinal vesicle breakdown (GVBD) in Xenopus laevis oocytes. (i) PKCAla22,23 and PKCAla27 had activators independent in vitro kinase activity, high phosphorylation levels in vivo, and localized in both cytosolic and particulate fractions. These mutants were not fully biologically active. (ii) PKCAla22,23,27 had a low phosphorylation level in vivo, was found predominantly in the particulate fraction and was the most biologically active. These results suggest that basic residues in the auto-inhibitory domain account for the regulation of kinase activity and the cytosolic retention of PKC. The particulate association or the cytosolic clearance of PKC may facilitate signal transduction in the cell.

Amino Acid Sequence↗
PubMed1992

The dyad palindromic glutathione transferase P enhancer binds multiple factors including AP1.

Glutathione Transferase P (GST-P) gene expression is dominantly regulated by an upstream enhancer (GPEI) consisting of a dyad of palindromically oriented imperfect TPA (12-O-tetradecanoyl-phorbol-13-acetate)-responsive elements (TRE). GPEI is active in AP1-lacking F9 cells as well in AP1-containing HeLa cells. Despite GPEI's similarity to a TRE, c-jun co-transfection has only a minimal effect on transactivation. Antisense c-jun and c-fos co-transfection experiments further demonstrate the lack of a role for AP1 in GPEI mediated trans-activation in F9 cells, although endogenously present AP1 can influence GPEI in HeLa cells. Co-transfection of delta fosB with c-jun, which forms an inactive c-Jun/delta FosB heterodimer that binds TRE sequences, inhibits GPEI-mediated transcription in AP1-lacking F9 cells as well as AP1-containing HeLa cells. These data suggest novel factor(s) other than AP1 are influencing GPEI. Binding studies reveal multiple nucleoproteins bind to GPEI. These factors are likely responsible for the high level of GPEI-mediated transcription observed in the absence of AP1 and during hepatocarcinogenesis.

Animals↗
PubMed1992

Suppression of glutathione transferase P expression by glucocorticoid.

A strong enhancer element, GPEI, of the glutathione transferase P gene (GST-P) gene is composed of two phorbol 12-O-tetradecanoate 13-acetate (TPA) responsive element (TRE)-like sequences at opposite orientation. Unlike TRE sequences of other genes, GPEI exhibits a strong enhancer activity in F9 cells, which contains little AP-1. GPEI bound to AP-1 In vitro and GST-P expression was activated by TPA and exogenously introduced c-jun gene in a rat fibroblast cell line. Both the stimulated expression of GST-P gene by TPA and that by over-expressed c-Jun were suppressed to the basal level by dexamethasone, an inhibitor of AP-1. Basal expression of GST-P gene, however, was not inhibited by dexamethasone. Transfected chloramphenicol acetyltransferase (CAT) gene having GPEI also behaved as the endogenous GST-P gene. These results indicate that the GPEI is activated by AP-1 but constitutive activity of this enhancer in a rat fibroblast cell line 3Y1 cells is due to some unknown mechanism other than AP-1.

Animals↗
PubMed1992

Isolation and characterization of activin receptor from mouse embryonal carcinoma cells. Identification of its serine/threonine/tyrosine protein kinase activity.

The activin receptor protein was isolated from the mouse embryonal carcinoma (EC) cell line P19 by three cycles of affinity chromatography on an activin A-immobilized column. The purified receptor had a specific and high affinity for activins A, AB, and B (Kd = 345 pM), but not for transforming growth factor beta. The purified activin receptor was identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and ligand blotting analysis as a single protein of 70 kDa. The amino acid sequence of the first 18 NH2-terminal residues revealed that the receptor is a member of the activin receptor family. The purified receptor phosphorylated itself and exogenous substrate proteins on serine, threonine, and tyrosine residues, indicating that the activin receptor is a transmembrane serine/threonine/tyrosine protein kinase. These results suggest that signal transduction of activin employs a novel pathway via a new class of cellular receptor in EC P19 cells.

Activin Receptors↗
PubMed1992

Induction of differentiation of the human promyelocytic cell line HL-60 by activin/EDF.

A human promyelocytic cell line, HL-60, treated with activin/EDF was found to differentiate into monocyte/macrophage-like cells. This was shown not only by morphology but by the loss of myeloperoxidase granules and the appearance of nonspecific esterase. Dose-dependent inhibition of the differentiation by follistatin, an activin-binding protein, confirmed that it was indeed caused by activin. Thus, activin/EDF exerts its effect on hematopoietic cells not only on erythroid differentiation but also on at least a part of myeloid cell differentiation.

Activins↗
PubMed1992

Molecular cloning of rabbit CAP-50, a calcyclin-associated annexin protein.

CAP-50 is a member of annexin family proteins which binds specifically to calcyclin in a Ca2+ dependent manner (Tokumitsu. H., Mizutani. A., Minami. H., Kobayashi. R., and Hidaka. H. (1992) J. Biol. Chem. 267,8919-8924). The cDNA representing the rabbit form of this protein has been cloned from rabbit lung cDNA library. Sequence analysis of two overlapping clones revealed a 81-nucleotides 5'-nontranslated region, 1512-nucleotides of open reading frame, a 672-nucleotides 3'-nontranslated region, and a poly(A) tail. Authenticity of the clones was confirmed by comparison of portions of the deduced amino acid sequence with eight sequences of proteolytic peptides obtained from rabbit lung protein. CAP-50 cDNA encodes a 503 residue protein with a calculated M(r) of 54,043 and shows that the protein is composed of four imperfect repeats and hydrophobic N-terminal region. C-terminal region including four imperfect repeats shows 58.1% identity with human synexin (annexin VII), 48.0% identity with annexin I, 47.4% identity with annexin II, 60.1% identity with annexin IV, 54.5% identity with annexin V. Hydrophobic N-terminal region composed of 202 amino acid residues is not homologous with other annexin proteins suggesting that CAP-50 is a novel member of annexin family proteins.

Amino Acid Sequence↗
PubMed1992

Inhibition of gastric H+,K(+)-ATPase and acid secretion by cassigarol A, a polyphenol from Cassia garrettiana Craib.

The effects of cassigarol A, a naturally occurring polyphenol, on gastric H+,K(+)-ATPase and gastric acid secretion were studied. Cassigarol A inhibited H+,K(+)-ATPase and K-stimulated p-nitrophenyl phosphatase from hog gastric mucosa with 50% inhibition of 1.2 x 10(-6) and 6.3 x 10(-6) M, respectively. The kinetic study showed that the inhibition of H+,K(+)-ATPase by cassigarol A was competitive with respect to ATP and non-competitive with respect to K+. Cassigarol A inhibited both H+,K(+)-ATPase-mediated proton transport and 2-deoxy-D-glucose-induced acid secretion. On the other hand, cassigarol A acetate, in which phenolic hydroxy groups are acetylated, was not effective in the inhibition of enzyme activity and acid secretion. These results indicate that cassigarol A is a potent inhibitor of gastric H+,K(+)-ATPase, that the anti-secretory activity of cassigarol A is related to the inhibition of H+,K(+)-ATPase and that an important moiety of cassigarol A in the interaction with the enzyme is the phenolic hydroxy groups.

Adenosine Triphosphatases↗
PubMed1992

Follistatin is a developmentally regulated cytokine in neural differentiation.

Activin acts mitogenically on P19 cells as well as being inhibitory of the differentiation of retinoic acid-treated P19 cells and some neuroblastoma cell lines. Here, we show some lines of evidence that follistatin, an activin-binding protein, is also involved in neural differentiation. Counteracting the activity of activin, addition of follistatin suppresses the anchorage-independent growth of P19 cells in soft agar and stimulates neurite outgrowth of a neuroblastoma cell line, IMR-32 cells. While activin does not seem to be expressed significantly, follistatin is demonstrated in the conditioned medium of these cells. Furthermore, the expression of follistatin in P19 cells is subject to dynamic fluctuations in response to retinoic acid treatment. These neural cells may produce follistatin in a cell stage-specific manner in order to interact with exogenously derived activin.

Activin Receptors↗
PubMed1992

Demonstration of a testis-specific trans-acting factor Tet-1 in vitro that binds to the promoter of the mouse protamine 1 gene.

We have established testis-specific in vitro transcription of the mouse protamine 1 (MP1) gene using rat testis nuclear extracts. Addition of testis nuclear extracts to brain extracts enhanced transcription from the MP1 upstream sequence-carrying adenovirus major late promoter. Moreover, the MP1 upstream region from positions -92 to -41 alone exhibited transcriptional activation in a tissue-specific manner. DNase I footprinting demonstrated the presence of a DNA-binding factor around position -60 (Tet-1) in testis nuclear extracts, but not in other tissues. Gel shift analysis also revealed the presence of testis-specific Tet-1. Since mutational analysis in transcriptional and binding assays demonstrates that the Tet-1 site is responsible for transcriptional activation, we suggest that Tet-1 is a novel tissue-specific trans-acting factor. The Tet-1-recognizing sequence was delineated to the 11-mer TGACTTCATAA at position -64. Although the first 8-mer in the Tet-1 11-mer shares homology with the cyclic AMP-responsive element, Tet-1 is demonstrated to be distinct from known cAMP-responsive element-binding factors.

Adenoviridae↗
PubMed1992

Functional regulation of osteoblastic cells by the interaction of activin-A with follistatin.

A high number of 125I-activin-A binding sites (an apparent Kd of 260 pM and 5,600 sites/cell) were observed on MC3T3-E1 cells, a well characterized osteoblastic cell line. Activin-A has a mitogenic effect on these cells, with the greatest influence being observed on cells in an undifferentiated state, as well as a suppressive effect on the alkaline phosphatase activity. Northern and ligand blotting analyses revealed that these osteoblastic cells produce follistatin, which was down-regulated by retinoic acid treatment. Because follistatin is an activin-A-binding protein, we suggest that activin-A modulates the function of osteoblastic cells by being regulated by follistatin during differentiation.

Activins↗
PubMed1992

Mouse rRNA gene transcription factor mUBF requires both HMG-box1 and an acidic tail for nucleolar accumulation: molecular analysis of the nucleolar targeting mechanism.

RNA polymerase I requires at least two nucleolar transcription factors, UBF and SL-1, for ribosomal RNA gene (rDNA) transcription. UBF requires SL-1 for the formation of a stable initiation complex on the rDNA promoter region. We have determined the region of mouse UBF (mUBF) required for nucleolar targeting. Although mUBF has a nuclear localization sequence, this sequence alone is not sufficient for mUBF to accumulate in the nucleolus. Deletion analyses show that mUBF requires a wide region except for the N-terminal 101 amino acids for nucleolar targeting. Deletion of either the HMG-box1, a region crucial for rDNA binding, or the acidic tail, a region that may interact with SL-1, results in the loss of nucleolar targeting. We show by DNA affinity analysis that the HMG-box1 is absolutely necessary for mUBF to bind to the upstream control element of the rDNA. We also show that mUBFs with various internal deletions retain both nucleolar targeting and DNA binding ability. A clear correlation was demonstrated between the DNA binding and nucleolar targeting ability. These results suggest that UBF is transferred to the nucleus by its NLS and is sequestered in the nucleolus by its specific and stable binding to the rDNA promoter via HMG-boxes and the acidic tail.

Animals↗
PubMed1992

Purification and partial characterization of K+ channel blockers from the venom of Dendroaspis angusticeps.

Two polypeptides (designated DTX-A and DTX-B) were purified from crude snake venom of Dendroaspis angusticeps using gel filtration, cation exchange column chromatography and cation exchange high performance liquid chromatography, and their blocking actions of K+ channels were investigated in rat brain synaptosomes. Both DTX-A and DTX-B inhibited the voltage-dependent 42K efflux from the synaptosomes. DTX-A blocked 42K efflux of both the rapidly inactivating phase (component T) and the slowly inactivating phase (component S). The inhibitory effect of DTX-A on component T was pronounced compared with that on component S. However, DTX-B selectively blocked 42K efflux of component S. The molecular weights of DTX-A and DTX-B were estimated to be ca 10,000 by SDS-polyacrylamide gel electrophoresis. The amino acid composition of these toxins is different from that of polypeptide purified from the venom of D. angusticeps (alpha-, beta-, gamma- and delta-DTX). These results suggest that DTX-A and DTX-B are new polypeptides which block voltage-dependent K+ channels selectively, and that they are useful tools for investigating the K+ channel.

Amino Acid Sequence↗
PubMed1992

Inhibitory effect of tannic acid on gastric H+,K(+)-ATPase.

The effect of tannic acid on gastric H+,K(+)-ATPase was studied. Tannic acid dose-dependently inhibited pig gastric H+,K(+)-ATPase activity with an IC50 value of 2.9 x 10(-8) M. Tannic acid also inhibited K(+)-stimulated p-nitrophenyl phosphatase (K(+)-pNPPase) activity, which is found in gastric H+,K(+)-ATPase preparations, as well as H+,K(+)-ATPase activity, with an IC50 value of 4.1 x 10(-7) M. Kinetic studies showed that the inhibition of H+,K(+)-ATPase activity by tannic acid was competitive with respect to ATP and noncompetitive with respect to K+. These results show that tannic acid is a potent inhibitor of gastric H+,K(+)-ATPase; this may be related to its anti-secretory and anti-ulcerogenic effects.

Adenosine Triphosphatases↗