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Biomedical subjects

M Yamaguchi

Publications and source records attributed to M Yamaguchi.

At least 361 records · Page 20Linked to original sources
PubMed1999

Enhancement of neutral phosphatase activity in the cytosol and nuclei of regenerating rat liver: role of endogenous regucalcin.

The role of endogenous regucalcin (RC) in the regulation of neutral phosphatase activity in regenerating rat liver was investigated. The liver weight reduced by a partial hepatectomy (about 70%) was completely restored at 72 h after surgery. Phosphotyrosine, phosphoserine, and phosphothreonine were used as the substrate for the assay of phosphatase activity. Phosphatase activity toward phosphotyrosine in the hepatic cytosol and nuclei was significantly increased at 24-72 h after hepatectomy. Such an increase was not seen in the case of phosphoserine and phosphothreonine. However, the presence of anti-RC monoclonal antibody (200 ng/ml) in the enzyme reaction mixture caused a remarkable elevation of phosphatase activity toward three phosphoaminoacids in the hepatic cytosol at 24 and 48 h after hepatectomy. In the liver nuclei after sham operation or hepatectomy, phosphatase activity toward three phosphoaminoacids was significantly raised by the addition of anti-RC antibody (150 ng/ml). The nuclear phosphatase activity toward phosphothreonine in regenerating liver was significantly enhanced in the presence of anti-RC antibody (100 and 150 ng/ml). The effect of anti-RC antibody to increase phosphatase activity toward three phosphoaminoacids in the cytosol and nuclei of regenerating liver was completely blocked by the addition of exogenous RC (1.0 microM). The present study demonstrates that protein phosphatase activity in the cytoplasm and nuclei is enhanced in regenerating rat liver. This enhancement may be suppressed by endogenous RC.

Animals↗
PubMed1999

Characterization of cleavage enzymes for sterol regulatory element binding protein in hamster liver microsomes.

Sterol regulatory element binding proteins (SREBP-1 and SREBP-2) are the key transcription factors for the regulation of the cellular cholesterol level. To identify proteolytic enzymes for SREBPs, a fluorogenic peptide substrate, MOCAc-GRSVLSFK(Dnp)rr-NH2, was synthesized according to the proposed cleavage site of human SREBP-2. In microsome fractions from hamster liver, we found a peptidase activity inhibitable by the synthetic inhibitor Ac-GRSVL-aldehyde with an IC50 of 40 nM. This peptidase separated into three peaks of approximately 400 kDa, 60 kDa, and 30 kDa (Mp400, Mp60 and Mp30 respectively) upon gel permeation chromatography. Mp30 was purified to apparent homogeneity with an Mr of 32 kDa. The partial amino acid sequence of Mp30 possessed homology to cathepsin B (EC 3.4.22.1). A 109 kDa protein band on SDS-PAGE which corresponded to Mp400 exhibited homology to neprilysin (EC 3.4.24.11) in partial amino acid sequence. These findings suggest several degradative pathways for SREBP in liver microsome membranes.

Amino Acid Sequence↗
PubMed1999

Genetic analysis of ossification of the posterior longitudinal ligament.

STUDY DESIGN: The human leukocyte antigen (HLA) haplotypes in families of patients with known ossification of the posterior longitudinal ligament (OPLL) were reviewed. OBJECTIVE: To clarify how genetic factors relate to the development of OPLL. SUMMARY OF BACKGROUND DATA: The association between genetic factors and the development of OPLL is still unknown. MATERIALS AND METHODS: The association between HLA haplotypes and OPLL was studied in families of 24 patients with OPLL. RESULTS: The prevalence of OPLL was higher in the siblings showing a higher share of identical HLA haplotypes: 10 (53%) of 19 with concurrence of two strands, and 5 (24%) of 21 with concurrence of one strand. Of 21 subjects who had no HLA haplotype identical with that in OPLL patients, only one showed evidence of OPLL. CONCLUSION: Genetic factors predispose toward the development of OPLL.

Aged↗
PubMed1999

Effect of cellular aging on the induction of cyclooxygenase-2 by mechanical stress in human periodontal ligament cells.

The production of prostaglandin (PGE2) in human periodontal ligament fibroblast (hPLF) cells is increased by mechanical stress, however, the age-related changes in the susceptibility of hPLF cells in response to mechanical stress remain unclear. The purpose of this study was to examine the influence of in vitro cellular aging on PGE2 production and the gene expression of cyclooxygenase (COX) in mechanically stressed hPLF cells. In vitro cellular aged hPLF cells were prepared by sequential subcultivations of hPLF cells from young healthy periodontal ligaments. In vitro cellular aged hPLF cells produced a significantly higher amount of PGE2, as compared with young hPLF cells, when the cells were exposed to cyclic tension force in a time- and magnitude-dependent manner. The COX-2 mRNA level in aged cells was higher than that in young cells, whereas COX-1 mRNA remained unchanged. Since PGE2 from hPLF cells was stimulated by in vitro aging as presented here, aging of hPLF cells may affect the severity of inflammation and bone resorption in the aged through the production of a large amount of PGE2 in response to an excessive force such as a traumatic occlusion.

Cells, Cultured↗
PubMed1999

IgE enhances Fc epsilon receptor I expression and IgE-dependent release of histamine and lipid mediators from human umbilical cord blood-derived mast cells: synergistic effect of IL-4 and IgE on human mast cell Fc epsilon receptor I expression and mediator release.

We investigated the effects of IgE versus IL-4 on Fc epsilon RI surface expression in differentiated human mast cells derived in vitro from umbilical cord blood mononuclear cells. We found that IgE (at 5 micrograms/ml) much more strikingly enhanced surface expression of Fc epsilon RI than did IL-4 (at 0.1-100 ng/ml); similar results were also obtained with differentiated mouse mast cells. However, IL-4 acted synergistically with IgE to enhance Fc epsilon RI expression in these umbilical cord blood-derived human mast cells, as well as in mouse peritoneal mast cells derived from IL-4-/- or IL-4+/+ mice. We also found that: 1) IgE-dependent enhancement of Fc epsilon RI expression was associated with a significantly enhanced ability of these human mast cells to secrete histamine, PGD2, and leukotriene C4 upon subsequent passive sensitization with IgE and challenge with anti-IgE; 2) preincubation with IL-4 enhanced IgE-dependent mediator secretion in these cells even in the absence of significant effects on Fc epsilon RI surface expression; 3) when used together with IgE, IL-4 enhanced IgE-dependent mediator secretion in human mast cells to levels greater than those observed in cells that had been preincubated with IgE alone; and 4) batches of human mast cells generated in vitro from umbilical cord blood cells derived from different donors exhibited differences in the magnitude and pattern of histamine and lipid mediator release in response to anti-IgE challenge, both under baseline conditions and after preincubation with IgE and/or IL-4.

Animals↗
PubMed1999

Colocalization of leptin receptor (OB-R) mRNA and placental lactogen-II in rat trophoblast cells: gestational profile of OB-R mRNA expression in placentae.

The present study was designed to clarify the cellular localization and expression of leptin receptor(s) [OB-R(s)] mRNA including its splice variants and their correlation with the cells which secrete placental hormone, placental lactogen-II (PL-II), in rat placentae. By in situ hybridization analysis, hybridization signals for OB-Rb and the common extracellular domain of OB-R were first detectable in some cells of the labyrinth zone of the placentae on day 14 of pregnancy and then a lot of cells dispersed in the entire area of the labyrinth zone expressed OB-Rb during the latter half of pregnancy. However, no expression was observed in the decidua and the junctional zone of the placentae during pregnancy. Double staining study revealed that signals for OB-R expressing trophoblast cells showed PL-II immunoreactivity in the labyrinth zone of the placentae. In Northern blot analysis, two bands (2.8 kb and 5.1 kb) of OB-R mRNA expression were observed in the placentae from day 17 to 21 of pregnancy and the expression of both increased markedly up to day 21 of pregnancy. RT-PCR analysis revealed that OB-Rb, OB-Ra, and OB-Re are expressed in the placentae on days 19 and 21 of pregnancy. These results suggest that the OB-R may have a physiological significance in the placental function during the latter half of pregnancy.

Alternative Splicing↗
PubMed1999

Interhemispheric asymmetry of event-related fields concerned with logical processing during auditory oddball stimulation.

This study investigated the cortex during logical processing of auditory information using a 122-channel dc-SQUID gradiometer. The experimental task was designed to require a simple logical decision prior to counting rare paired tones, which consisted of two different pitches and were presented to separate ears. Among six subjects, left and right predominant dipolar activity was observed in three subjects each. When the dipolar sources were superimposed on MR images, the inferior region of the supramarginal gyrus showed activation, suggesting that logical processing occurred in the association cortex but not in the auditory cortex. We propose a modified cognitive sequence model in which auditory information processed in Heschl's gyri is transmitted to the supramarginal gyrus to commence automatic detection processing.

Acoustic Stimulation↗
PubMed1999

Tyrosine phosphorylation of STAT3 by leptin through leptin receptor in mouse metaphase 2 stage oocyte.

Leptin is the product of the obese gene (ob), and is secreted in plasma from mature adipocytes. It has been recently reported that leptin is synthesized in granulosa and cumulus cells within the follicle of the ovary, and is present in mature human oocytes, suggesting possible roles of leptin in several aspects of pre- and post-ovulatory follicular development. On the other hand, STAT (Signal Transducer and Activator of Transcription) transcription factors are involved in leptin-associated signal transduction. In this report, we studied the expression of leptin receptor and STAT3 activation by leptin in metaphase 2 stage (M2) oocytes. Reverse transcriptase-polymerase chain reaction (RT-PCR) and immunoblotting showed that mRNA and protein of leptin receptor were expressed in M2 stage oocyte. Leptin at 15 ng/ml, the concentration observed in follicular fluid, caused tyrosine phosphorylation of STAT3 in mouse M2 stage oocytes. These results suggest possible roles of leptin in several aspects during oocyte maturation by activating the STAT signal transduction pathway.

Adipocytes↗
PubMed1999

Promoter characterization of the rat gene for Ca2+-binding protein regucalcin. Transcriptional regulation by signaling factors.

To understand the mechanism underlying the regulation of the Ca2+-binding protein regucalcin gene expression, we characterized the 5'-flanking region of the rat regucalcin gene. The transcriptional start site of the rat regucalcin gene was determined by the cap site hunting method with rat liver cap site cDNA. The 5'-flanking region of the rat regucalcin gene ligated to a luciferase reporter gene possessed functional promoter activity in rat H4-II-E hepatoma cells. 3'- and 5'-deletion analyses indicated the sequence required for basal functional promoter activity of the rat regucalcin gene. The promoter activity of the rat regucalcin gene was enhanced by treatment with Bay K 8644, dibutyryl cAMP, phorbol esters, insulin, and dexamethasone. Using gel mobility shift assays, we found that nuclear proteins from H4-II-E cells specifically bind to the 5'-flanking region of the rat regucalcin gene. Moreover, gel mobility shift assays revealed that Bay K 8644, dibutyryl cAMP, phorbol esters, and insulin stimulated the binding of nuclear factors to the 5'-flanking region of the rat regucalcin gene in H4-II-E cells. These results suggest that Bay K 8644-, dibutyryl cAMP-, phorbol ester-, and insulin-inducible nuclear factors mediate the stimulatory effect of each regulator on promoter activity of the rat regucalcin gene.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1999

Identification of three conserved regions in the DREF transcription factors from Drosophila melanogaster and Drosophila virilis.

The genes for a DNA replication-related element-binding factor (DREF) were isolated from Drosophila melanogaster and Drosophila virilis, and their nucleotide sequences were determined. Drosophila virilis DREF consists of 742 amino acid residues, which is 33 amino acids longer than D.melanogaster DREF. Comparison of the amino acid sequences revealed that D.virilis DREF is 71% identical to its D. melanogaster homolog. Three highly conserved regions were identified at amino acid positions 14-182 (CR1), 432-568 (CR2) and 636-730 (CR3) of the D.virilis DREF, with 86.4, 86.1 and 83.3% identities, respectively. Transgenic flies in which expression of three conserved regions of D.melanogaster DREF was targeted to the eye imaginal disc were established. Expression of CR1 in the developing eye imaginal discs resulted in a severe rough eye phenotype in adult flies. Expression of CR3 also caused a rough eye phenotype, while that of CR2 had no apparent effect on eye morphology. Expression of either CR1 or CR3 in eye imaginal disc cells inhibited cell cycle progression and reduced incorporation of 5-bromo-2'-deoxyuridine into the S-phase zone (the second mitotic wave) behind the morphogenetic furrow. The results indicate that both CR1 and CR3 are important for DREF functions.

Amino Acid Sequence↗
PubMed1999

Cyano2Dbase updated: linkage of 234 protein spots to corresponding genes through N-terminal microsequencing.

The cyanobacterium Synechocystis sp. strain PCC6803 is an interesting model organism for preoteome study because it is a photosynthetic procaryote and its genomic sequence has already been determined at our institute. We thus initiated characterization of this organism from a proteomic viewpoint by exploiting two-dimensional (2-D) gel electrophoresis coupled with N-terminal protein sequencing. In a previous study, we linked 130 protein spots on two dimensional gels with the genes that encoded them. As an extension of the previous study, the number of protein spots linked to their corresponding genes was increased to 227 in this study by separately analyzing cyanobacterial proteins in four different fractions (soluble, insoluble, thylakoid membrane, and secretory protein fractions). The resultant updated 2-D protein-gene linkage database, named Cyano2Dbase, will serve as an indispensable tool in future cyanobacterial proteomic studies. From the data compiled in the Cyano2Dbase, we can extract many items of information concerning translation, posttranslational processing including characteristics of cyanobacterial signal sequences and modification of cyanobacterial proteins. The Cyano2Dbase is available to the public through the World Wide Web (http://www.kazusa.or.jp/tech/sazuka/cyano/pr oteome.html).

Amino Acid Sequence↗
PubMed1999

Polyethylene wear vector in vivo: a three-dimensional analysis using retrieved acetabular components and radiographs.

Polyethylene wear of the acetabular component can be described as one or more vectors. To help clarify the mechanisms of wear advancement in vivo, we used a combination of retrieved implants and radiographs to describe the three-dimensional wear vectors in total hip arthroplasty. The wear vectors in 41 retrieved implants from a single manufacturer were measured with use of the shadowgraph technique, and the spatial orientation of each implant was calculated from serial anteroposterior pelvic radiographs. On the basis of the combination of the wear vector in the implant and implant orientation in the pelvis, the wear vectors in vivo were determined. The mean wear vector was directed 8.1 degree lateral in the coronal plane and 4.1 degree posterior in the sagittal plane. The wear vectors in vivo showed a relatively wide range of directions, not necessarily coinciding with the commonly presumed resultant force in the hip. The wear vectors were not associated with the spatial orientation of the acetabular components, but cups with impingement demonstrated more anterior wear than did those without impingement. Our results suggest that the process of polyethylene wear is not as simple as previously described and that several factors influence advancement of wear in vivo.

Acetabulum↗
PubMed1999

Overexpression of p21Waf-1 in vascular smooth muscle cells: regulation of proliferation, differentiation, and cell size.

Cyclin-dependent kinase inhibitor p21Waf-1 is recognized as a negative regulator of cell cycle progression, and it possibly mediates cell differentiation and apoptosis. To understand the role of p21Waf-1 in phenotypic modulation of vascular smooth muscle cells (SMC), we induced the overexpression of p21Waf-1 in cultured rat SMC. The recombinant adenovirus vector encoding p21Waf-1 (AdvCMVp21) was constructed by homologous recombination and the vector encoding beta-galactosidase (AdvCMVLacZ) was used as an experimental control. Administration of AdvCMVp21 suppressed serum-induced proliferation and cell cycle progression; however, the number of quiescent cells and the population of TUNEL-positive cells were not altered. Overexpression of p21Waf-1 did not affect the expression of contractile proteins and the availability of an endogenous growth factor signal p21Waf-1 may regulate cell cycle progression in SMC without affecting the apoptotic process and cell differentiation. Furthermore, the longitudinal diameter of AdvCMVp21 infected cells was increased compared with that of AdvCMVLacZ infected cells. Total protein content was also increased in AdvCMVp21 infected cells. Responses to the serum stimulation, proliferation and total protein synthesis may be independently regulated. Thus, the suppression of cell cycle progression by p21Waf-1 resulted in cellular hypertrophy of SMC.

Adenoviridae↗
PubMed1999

The effect of flow on the neutrophil-mediated Ca2+ responses in human vascular endothelial cells stimulated by endotoxin.

Leukocyte-vascular endothelial cell (EC) interactions which promote inflammatory and immune reactions involve bidirectional signaling between two cell types. We investigated the effects of flow on neutrophil-mediated changes in endothelial intracellular Ca2+ levels ([Ca2+]i). Cultured human umbilical vein ECs stimulated by endotoxin were labeled with Fura-2 and exposed to fluid flow with neutrophils. The individual changes in [Ca2+]i were monitored. The application of flow with neutrophils to stimulated ECs led to an increase in [Ca2+]i although either flow without neutrophils or neutrophils without flow rarely induced a rise in [Ca2+]i. Furthermore, flow application with neutrophils to unstimulated ECs also rarely promoted a rise in [Ca2+]i. These findings suggest that the flow might thus induce or enhance the inflammatory process by the induction of Ca2+ signaling in endotoxin-stimulated endothelium facing neutrophils in the blood flow.

Calcium↗
PubMed1999

Conversion of right atrioventricular to total cavopulmonary anastomosis in the management of post-Fontan arrhythmia: report of a case.

Both the original and modified Fontan procedures are associated with several late complications such as atrial arrhythmias, thromboembolism, and right pulmonary vein compression caused by a markedly enlarged right atrium. We describe herein the case of a patient who underwent conversion of right atrioventricular to total cavopulmonary anastomosis to control atrial arrhythmia that developed 12 years after a modified Fontan operation. The procedure proved successful in alleviating his symptoms immediately. He is now doing well with no recurrence of atrial arrhythmia 1 year after the operation.

Arrhythmias, Cardiac↗
PubMed1999

Molecular characterization of mitotic cyclins in rice plants.

Cyclins are known to activate cyclin-dependent protein kinases, which are essential for cell cycle progression in eukaryotes. We isolated full-length cDNAs encoding rice mitotic cyclins named CycA1; os; 1 and CycB2;os;1, which are related to A- and B-type cyclins, respectively, from animals. To characterize the function of these mitotic cyclins, as well as that of another B-type cyclin, CycB2;os;2, each cDNA was introduced into yeast cells. When cDNAs encoding CycA1;os;1, CycB2;os; or CycB2;os;2 were overexpressed in the yeast mutant DLI, which is deficient in G1 cyclins, the mutant phenotype was rescued, indicating that these mitotic cyclins are functional in yeast cells. When the cDNA encoding CycB2;os;1 was expressed in the wild-type yeast strain, the cells lost the ability to grow, whereas the expression of either cycA1;os: 1 or cycB2;os;2 did not inhibit growth. In situ hybridization of these mitotic cyclin genes with rice root apices and counterstaining of chromosomes with a DNA-specific dye revealed that cycA1;os;1 is expressed from the G2 phase to the early M phase, while transcripts of cycB2:os;1 and cycB2;os;2 accumulated until the end of mitosis. Our results indicate that these B2-type cyclins may be involved in the control of mitosis, in combination with a G2/M-phase CDK.

Amino Acid Sequence↗
PubMed1999

Cloning and characterization of a gene (arpA) from Aspergillus oryzae encoding an actin-related protein required for normal nuclear distribution and morphology of conidiophores.

We have isolated the arpA gene from Aspergillus oryzae as a homologue of the Neurospora crassa ro-4 gene. In N. crassa, mutations in the ro-4 gene, which encodes a major component of the dynactin complex Arp1, causes curling of hyphae and abnormalities in nuclear distribution. The arpA gene contains two introns and encodes a polypeptide of 381 amino acids, with a 78% sequence identity to the N. crassa Arp1. Overexpression of the arpA gene causes a defect in nuclear migration into elongating hyphae of germlings in A. oryzae. We constructed arpA disruptant strains of A. oryzae. The arpA null mutants showed poor growth and hyper-branched mycelia, as well as a nuclear distribution defect. Scanning electron microscopy revealed that the arpA null mutant has an aberrant conidiophore morphology with irregular phialides.

Actins↗