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Biomedical subjects

Y Murayama

Publications and source records attributed to Y Murayama.

At least 19 recordsLinked to original sources
PubMed1995

Inhibition of gastrin-stimulated enterochromaffin-like cell proliferation and mucosal histamine production in the rat stomach by the somatostatin analogue octreotide.

The effect of octreotide, a potent and long-acting analogue of somatostatin, on gastrin-stimulated proliferation and function of enterochromaffin-like (ECL) cells were examined in rats. Animals were divided into four groups and each group was continuously infused with saline, octreotide alone (40 micrograms/kg per day), gastrin alone (60 nmol/kg per day), or octreotide (40 micrograms/kg per day) plus gastrin (60 nmol/kg per day) respectively for 9 days via osmotic minipumps. Gastrin induced the increase of the bromodeoxyuridine labeling index and density of oxyntic mucosal ECL cells as well as oxyntic mucosal histidine decarboxylase activity. Octreotide completely abolished the gastrin-induced increases in the labeling index and density of ECL cells and oxyntic mucosal histidine decarboxylase activity. These results indicate that octreotide inhibits gastrin-stimulated proliferation of ECL cells and histamine production by these cells.

Animals↗
PubMed1995

Ligand-dependent G protein coupling function of amyloid transmembrane precursor.

Amyloid precursor protein (APP), a transmembrane precursor of beta-amyloid, possesses a function whereby it associates with G(o) through its cytoplasmic His657-Lys676. Here we demonstrate that APP has a receptor function. In phospholipid vesicles consisting of baculovirally made APP695 and brain trimeric G(o), 22C11, a monoclonal antibody against the extracellular domain of APP, increased GTP gamma S binding and the turnover number of GTPase of G(o) without affecting its intrinsic GTPase activity. This effect of 22C11 was specific among various antibodies and was observed neither in G(o) vesicles nor in APP695/Gi2 vesicles. In APP695/G(o) vesicles, synthetic APP66-81, the epitope of 22C11, competitively antagonized the action of 22C11. Monoclonal antibody against APP657-676, the G(o) binding domain of APP695, specifically blocked 22C11-dependent activation of G(o). Therefore, APP has a potential receptor function whereby it specifically activates G(o) in a ligand-dependent and ligand-specific manner.

Amyloid beta-Protein Precursor↗
PubMed1995

Expression of the hepatocyte growth factor gene during chick limb development.

It has been shown that mirror-image duplications of the zeugopodia and digits are formed when MRC-5 fibroblasts producing hepatocyte growth factor (HGF) are applied to the anterior region of the chick limb bud (Yonei et al. [1993] Dev. Biol. 160:246-253). To evaluate the role of HGF in limb development, we observed the expression pattern of the HGF gene using in situ hybridization. The HGF gene was expressed in the mesoderm of the limb bud and in the central core region of mandibular arch and maxillary processes at stages 17 to 24. When both wing and leg buds begin to extend distally, the HGF gene is expressed in the mesenchymal cells, but not in the ectodermal cells and somites. Concomitant with establishment of the apical ectodermal ridge, distal mesenchymal cells of the limb bud express the HGF gene intensely with a gradient higher in the distal region. The HGF expression is later confined to the ventral and subapical mesenchyme of the limb bud, although no signal is detectable in the apical and non-ridge ectoderm. However, signal for the c-met proto-oncogene encoding the HGF receptor is not detectable in the limb bud at stages 17 to 24. These results suggest that HGF produced in the limb mesoderm may be involved in initial induction and maintenance of the apical ectoderm during limb development.

Animals↗
PubMed1995

Localization of heparin-binding epidermal growth factor-like growth factor in human gastric mucosa.

BACKGROUND & AIMS: Heparin-binding epidermal growth factor-like growth factor (HB-EGF) has been recently identified as a member of the EGF family. EGF receptors to which HB-EGF can bind have been detected in some types of gastric epithelial cells. The aim of this study was to investigate whether HB-EGF is produced in gastric epithelial cells to maintain normal gastric mucosa. METHODS: Gene expression and production of HB-EGF protein were investigated using Northern hybridization and immunohistochemistry, and the types of cells producing this protein were determined in human gastric mucosa. RESULTS: HB-EGF messenger RNA was detected in the body and antrum. Immunohistochemical staining showed that HB-EGF was localized mainly in parietal cells of fundic glands and in gastrin cells of pyloric glands. Also, the immunoreactivity of EGF receptors was observed in parietal cells and gastrin cells and faintly in surface epithelial cells and mucous neck cells of the proliferative zone. CONCLUSIONS: The results suggest that HB-EGF is synthesized mainly in parietal cells and gastrin cells and may act in an autocrine and/or paracrine manner in the regulation of proliferation and differentiation of the gastric mucosal cells through their surface EGF receptors.

Adult↗
PubMed1995

Long-term potentiation of glycinergic inhibitory synaptic transmission.

1. Tetanizing protocols were used to test whether glycinergic inhibition undergoes long-term plasticity in vivo. For this purpose we studied the inhibition evoked disynaptically in the teleost Mauthner (M) cell by stimulation of the posterior branch of the contralateral VIIIth nerve. The advantage of this experimental design is that the inhibition, which is mediated by identified second-order commissural interneurons, is not contaminated by parallel excitation. 2. The VIIIth-nerve-evoked inhibitory postsynaptic potentials (IPSPs), which are generated at the level of the soma, are depolarizing in Cl(-)-loaded M cells. After VIIIth nerve tetanization, these IPSPs exhibited potentiation lasting > 30 min in 23 of 31 cells. The maximum enhancement measured 5-10 min after the onset of the tetanization averaged 100 +/- 19% (mean +/- SE). In contrast, the non-"tetanized" collateral IPSP induced by antidromic stimulation of the M axon did not increase significantly suggesting synaptic specificity of the potentiation. 3. Single-electrode voltage-clamp studies of Cl(-)-loaded M cells indicated that this plasticity is due to an increased synaptic conductance that occurs without obvious modifications of the kinetics or voltage dependence of the inhibitory postsynaptic currents. 4. The synaptic conductance and its changes during potentiation were quantified by measuring the inhibitory shunt of the antidromic spike while recording with potassium-acetate-filled electrodes. For this purpose the ratio, r', of the inhibitory to resting membrane conductances, was calculated using the expression (V/V')--1, where V and V' are the amplitudes of the control and the test antidromic spikes, respectively. This ratio was called fractional conductance. Measured at the peak of the expected VIIIth-nerve-evoked IPSP, r' increased by 114 +/- 18% (n = 46). Again the collateral inhibitory conductance was not modified. 5. Because there are two synapses in the inhibitory pathway, it became important to determine whether modifications of the second-order inhibitory junctions contribute to the overall potentiation. Several experimental procedures were used for this purpose. 6. The input-output relationship at the inhibitory synapses was determined by comparing the size of the presynaptic volley and r'. The former was recorded intra- or extracellularly as a monophasic positive potential, the so-called extrinsic hyperpolarizing potential, which increases in parallel with the strength of VIIIth nerve stimulation. In 12 experiments where the presynaptic volley was unaffected by the tetanization, suggesting lack of involvement of the first relay, r' nevertheless increased in amplitude by 79 +/- 14%.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

Studies on the phenotypic and functional characterization of peripheral blood lymphocytes from patients with early-onset periodontitis.

Juvenile and rapidly progressive periodontitis are grouped under the heading of patients with early-onset periodontitis (EOP). Many studies have investigated host risk factors in the etiology of EOP patients but these remain inconclusive. This study was undertaken to assess the possibility that an abnormality in the systemic lymphocyte subpopulation or function is involved in the etiology of EOP patients. Fourteen (14) patients with juvenile periodontitis (JP), 18 with rapidly progressive periodontitis (RPP), 22 with adult periodontitis (AP), and 33 with a healthy periodontium (HP) participated in this study. Lymphocyte subsets were determined by using panels of monoclonal antibodies (mAbs) and fluorescent flow cytometry. T cell blastogenesis was evaluated by [3H]-thymidine uptake. Pokeweed mitogen induced immunoglobulin G (IgG) and IgM synthesis were detected by sandwich enzyme-linked immunosorbent assay. There were wide distributions of values in all examinations among subjects. No significant difference could be found between the periodontitis patients and HP groups with the exception of a high CD4/CD8 ratio in all patient groups (P < 0.0001) and the depressed percentages of CD3 positive cells noted in the AP patient group (P < 0.0001). These results suggest that the majority of EOP patients do not show significantly different lymphocyte profiles from AP patients and HP subjects, and that lymphocyte cell dysfunctions are not always seen, even in EOP patients.

Adolescent↗
PubMed1994

Bidirectional regulation of c-fos promoter by an oncogenic gip2 mutant of G alpha i2. A novel implication of retinoblastoma gene product.

G alpha i2 is a tissue-specific proto-oncogene product, whose activated mutant gip2 induces transformation through less defined downstream pathways. We found that c-fos promoter is a target of gip2 in multiple kinds of cells. Serum response element was shown to be the positive enhancer element that mediates gip2-induced c-fos expression. We further demonstrated that gip2 stimulates the negative silencer activity of the retinoblastoma (Rb) control element (RCE) and inhibits the c-fos promoter activity through RCE located in the c-fos promoter region. The effect of gip2 on RCE was shown to be mediated by the Rb gene product (pRb). Furthermore, gip2 augmented underphosphorylated active form of pRb by promoting pRb expression and by affecting the phosphorylation state of pRb. gip2 therefore propagates both positive and negative signals to the c-fos promoter through two different elements, and pRb mediates the negative signal of gip2. We conclude that gip2 has bifunctional roles in transformation which pRb critically regulates. Given that Rat-1 cells, which gip2 can transform, lack the sensitivity to the gip2/pRb-mediated negative pathway, this study provides a novel insight into oncogenesis by gip2 and its tissue specificity.

Animals↗
PubMed1994

Heat shock protein 60 (GroEL) from Porphyromonas gingivalis: molecular cloning and sequence analysis of its gene and purification of the recombinant protein.

Porphyromonas gingivalis is associated with human periodontal disease. We cloned and sequenced the gene for heat shock protein 60 (GroEL, HSP60) from P. gingivalis FDC381. The identified clone carried a 2.6 kb DNA fragment which contained two open reading frames (ORFs) encoding a 9.6- and a 58.4-kDa protein. The translated amino acid sequence of these ORFs showed a high degree of homology with known sequences for GroES and GroEL from several bacterial species and humans. Escherichia coli carrying this clone expressed a 65-kDa protein which was recognized by anti-Mycobacterium leprae HSP60 monoclonal antibody. We purified the 65-kDa protein by DEAE-sepharose chromatography and hydroxyapatite chromatography. This protein was immunogenic and was recognized by sera from a number of patients with periodontal disease. This immunological reactivity and the existence of molecular mimicry between the P. gingivalis GroEL and other HSP homologs may indicate an important role for this molecule in periodontal lesion.

Amino Acid Sequence↗
PubMed1994

An intrinsic guanine nucleotide exchange inhibitor in Gi2 alpha. Significance of G-protein self-suppression which antagonizes receptor signal.

The alpha subunit of Gi2 (Gi2 alpha) is a member of the heterotrimeric G protein family, which transduces receptor signals as a proto-oncogene product. We have found a novel self-suppressive region in Gi2 alpha near its C terminus. A polypeptide consisting of residues 338-352 of Gi2 alpha (Gi2 alpha-339-352) antagonizes receptor- and receptor peptide-stimulated Gi2 alpha activation, without affecting basal activity. Antagonism by Gi2 alpha-338-352 is attributable to an interaction with activated Gi2 alpha, which is not competitive with receptor polypeptides. Combined with the reports suggesting the presence of self-suppressive domains in a juxta-C-terminal portion of Gi2 alpha and G(o) alpha, this study supports the hypothesis that Gi2 alpha-338-352 constitutes an intrinsic guanine nucleotide exchange inhibitor, which in turn antagonizes receptor stimulation, suggesting that G proteins are activated by receptors through relaxation of a self-suppressive conformation.

Amino Acid Sequence↗
PubMed1994

Structure and differential expression of two distinct genes encoding the chloroplast elongation factor Tu in tobacco.

We have isolated two nuclear genes, tufA and tufB, encoding chloroplast EF-Tu from a tobacco (Nicotiana sylvestris) genomic library. The tufA gene encodes a polypeptide of 478 amino-acid residues, consisting of a putative transit peptide of 70 residues and a mature EF-TuA of 408 residues. The tufB gene codes for a precursor proteins of 485 residues, containing a transit peptide of 77 residues and a mature EF-TuB of 408 residues. No introns were found in either gene. The sequence similarity within the coding regions of the two genes is 84.3% for nucleotides and 89.7% for amino acids. Multiple 5' ends of transcripts were observed for both tuf genes. Northern analysis revealed that the EF-Tu mRNA accumulated at least 30-fold more in leaf than in root tissue. Ribonuclease protection assays using gene-specific probes showed that the level of tufB mRNA is three-fold higher than that of tufA mRNA in leaves but in roots the tufB mRNA levels is less than half that of tufA mRNA. The relative amount of tufB mRNA is 30-fold higher in leaves than in roots whereas tufA messages are only five-fold higher in leaves. These data suggest that expression of both tuf genes is differentially regulated according to tissue and plastid type.

Amino Acid Sequence↗
PubMed1994

Isolation and characterization of a 53 kDa major cell envelope protein antigen from Treponema denticola ATCC 35405.

A major cell envelope protein was purified from the cell envelope fraction of Treponema denticola ATCC 35405 by ion exchange chromatography after extraction with Zwittergent 3-14. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed a relative molecular mass of 53 kDa for this protein with a pI of 6.3-6.8. Amino acid analysis revealed that this protein contained high proportions of hydrophobic amino acids (40.4%), and no cysteine could be detected. The N-terminus of the protein was blocked to Edman degradation. Rabbit antiserum raised against the purified 53 kDa protein reacted with the outer envelope of the T. denticola cell surface as confirmed by immunoelectron microscopy. This rabbit antiserum reacted with 4 of the 11 strains of treponemes tested in this study. Sera from 9 to 18 periodontitis patients reacted strongly with this 53 kDa cell envelope protein of T. denticola as determined by immunoblotting analysis.

Amino Acids↗
PubMed1994

Improved fold width and increased acid secretion after eradication of the organism in Helicobacter pylori associated enlarged fold gastritis.

This study examined the effects of eradication of Helicobacter pylori (H pylori) infection on gastric mucosal morphology and acid secretion. Sixteen H pylori positive patients with enlarged gastric body folds were divided into two groups: (a) patients with moderate enlargement (fold width: 6 to 10 mm, n = 8) and (b) patients with severe enlargement (> 10 mm, n = 8). After successful treatment, gastric body fold width was reduced in both groups (p < 0.01) with an associated decrease in inflammatory infiltrates in the body mucosa (p < 0.01 and p < 0.05). Basal acid output and tetragastrin stimulated maximal acid output (mean (SEM)) in all 16 patients significantly increased from 1.1 (0.5) to 2.9 (0.9) mmol/h (p < 0.05) and from 5.4 (1.3) to 18.7 (2.3) mmol/h (p < 0.01), respectively, with a significant decrease in fasting serum gastrin concentrations, from 127.1 (16.1) to 59.6 (3.8) pg/ml (p < 0.01). The increase in acid secretion after eradication of H pylori was more noticeable in the severe group, who had shown lower acid secretion and higher serum gastrin concentrations (p < 0.05) before eradication, than the increase seen in the moderate group. The decreases in ammonia nitrogen content seen after eradication were significant in basal (from 0.91 (0.17) to 0.37 (0.08) mmol/h, p < 0.05) and stimulated gastric secretions (from 1.57 (0.19) to 0.37 (0.13) mmol/h, p < 0.01), although these changes were too small to explain the increases in basal acid output and maximal acid output. These results suggest that inflammation of the gastric body mucosa caused by H pylori infection is associated with enlarged gastric body folds and inhibition of acid secretion in H pylori positive patients with enlarged gastric body folds.

Adult↗
PubMed1994

Molecular basis of leukocyte adhesion molecules in early-onset periodontitis patients with decreased CD11/CD18 expression on leukocytes.

We analyzed the cell-cell adherence related to CD11/CD18 and CD18 mRNA in individuals with decreased CD11/CD18 expression on their neutrophil surface. Epstein Barr virus-transformed B cell lines were developed from one localized juvenile periodontitis (LJP) patient with decreased CD11/CD18 in the peripheral blood neutrophils and without systemic diseases; two siblings with generalized prepubertal periodontitis (GPP) caused by leukocyte adhesion deficiency (LAD); another LJP patient; one localized prepubertal periodontitis (LPP) patient; and two healthy subjects. Adhesion of leukocytes to each other was measured as cluster formation by aggregation assay. The length and the amount of CD18 mRNA expressed in the cell lines were analyzed by Northern blotting using the 32P-labeled CD18 cDNA. The coding region of the mRNA was analyzed by the reverse transcription-polymerase chain reaction method. Base-mismatches between CD18 mRNA and the 32P-labeled RNA probe synthesized from CD18 cDNA were analyzed by RNase protection assay. In the adherence assay, cells from the LJP patients with decreased CD11/CD18 formed more clusters of smaller size and fewer cells than those of the other subjects. The cells from GPP and LAD patients did not aggregate and did not form clusters either in the absence or presence of PMA. There were no differences in the length and the amount of mRNA between the LJP patients and the other subjects, while GPP-LAD patients expressed a small amount of long mRNA. The whole coding region (2,313 base pairs) of all subjects was amplified except for the GPP-LAD patients, and the 5'-region (1,119 base pairs) was amplified from all subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Aggressive Periodontitis↗
PubMed1994

Cytokine-dependent synergistic regulation of interleukin-8 production from human gingival fibroblasts.

Human Gingival Fibroblasts (HGF) may have an important role in the orchestration of immuno-participant cells infiltrating the gingiva in response to continuously recurring bacterial infection. To examine the cytokine network regulating HGF-derived interleukin (IL)-8, a potent neutrophil chemotactic cytokine, we analyzed the effects of inflammatory cytokines alone and in combination on IL-8 production by HGF. IL-1 beta, tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), IL-6, and IL-8 were used as stimulants. HGF secreted IL-8 in a dose-dependent manner after stimulation with either IL-1 beta or TNF-alpha, but not with IFN-gamma or IL-6. Furthermore, IL-8 itself did not affect IL-8 mRNA accumulation in HGF in an autocrine manner. The combination of IL-1 beta and TNF-alpha synergistically enhanced the secretion of IL-8, whereas IFN-gamma suppressed IL-8 secretion by IL-1 beta- or TNF-alpha-stimulated HGF. These effects were also observed at each level of IL-8 mRNA expression in HGF. IL-8 secretion by cytokine-stimulated HGF was not influenced by the inhibition of PGE2 synthesis with indomethacin, indicating that endogenous PGE2 was not involved in IL-8 production by HGF. These results indicate that IL-8 production by HGF is synergistically stimulated by specific cytokines, IL-1 beta and TNF-alpha, and suggest that these stimulatory effects are down-regulated by IFN-gamma at the transcriptional level through PGE2-independent pathways. Thus, neutrophil-mediated processes in periodontal disease may be regulated in part by HGF in the cytokine network of immuno-participant cells.

Chemotaxis, Leukocyte↗
PubMed1994

Prostaglandin E2 inhibits interleukin-6 release but not its transcription in human gingival fibroblasts stimulated with interleukin-1 beta or tumor necrosis factor-alpha.

Inflammatory mediators produced by human gingival fibroblasts (HGF) have been implicated in the initiation and progression of periodontal disease. The purpose of this study was to examine whether prostaglandin E2 (PGE2), which is produced in abundance from HGF after stimulation with interleukin (IL)-1 beta or tumor necrosis factor-alpha (TNF-alpha), could regulate IL-6 production by HGF. HGF stimulated with either IL-1 beta or TNF-alpha showed a rapid and dose-dependent increase in IL-6 mRNA accumulation and IL-6 secretion, as demonstrated by reverse transcription-polymerase chain reaction analysis and bioassay. IL-6 secretion from either IL-1 beta- or TNF-alpha-stimulated HGF was enhanced by the inhibition of PGE2 synthesis with indomethacin. Furthermore, the addition of PGE2 inhibited IL-6 secretion from these cells. In contrast, indomethacin or PGE2 did not affect the accumulation of IL-6 mRNA in IL-1 beta-stimulated HGF. These data indicate that IL-6 production by HGF is up-regulated by specific cytokines, IL-1 beta and TNF-alpha, and suggest that this production may be partially down-regulated by endogenous and exogenous PGE2 at the post-transcriptional level.

Cells, Cultured↗
PubMed1994

Assessment of interleukin-6 in the pathogenesis of periodontal disease.

This study was performed to investigate the aspects of interleukin-6 (IL-6) production in both the gingival tissue and the peripheral blood of patients with periodontal disease and of periodontally healthy subjects. In addition, IL-6 expression in human gingival tissues was studied by reverse transcription-polymerase chain reaction analysis and by immunoperoxidase staining with anti-IL-6 monoclonal antibody. The levels of IL-6 in the culture supernatants from peripheral blood mononuclear cells (PBMC) stimulated with lipopolysaccharide and in serum were examined by bioassay. We detected IL-6 mRNA expression in all inflamed gingival tissues (17/17) examined and in 2/4 in healthy gingival tissues. IL-6 protein was detected mainly in endothelial cells, fibroblasts, and macrophages but not in the area containing T or B cells in the inflamed gingival tissues, and was not detected at all in healthy gingival tissues. There was no significant difference between the subjects with periodontal disease and those with healthy gingival tissues either in serum IL-6 levels or in the amount of IL-6 produced by PBMC. These results suggest that non-lymphoid cells in inflamed gingival tissue may contribute to the pathogenesis of periodontal disease via IL-6 production, and that the IL-6 produced in gingival tissue may not reflect the IL-6 levels in peripheral blood.

Adult↗
PubMed1994

Role of cytokine in the induction of adhesion molecules on cultured human gingival fibroblasts.

This study was undertaken in an effort to understand the role of cytokines on human gingival fibroblasts and T lymphocyte trafficking into inflamed gingival tissue. Using flow cytometry we examined gingival fibroblasts to determine the level of cell surface expression and the percentage of cells positive for intercellular adhesion molecule 1 (ICAM-1), the HLA-DR antigen, lymphocyte function-associated antigen 3 (LFA-3), and the CD44 molecule, which are involved in antigen presentation. The following cytokines were used: interleukin-1 beta (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), IL-6, and IL-8. The levels of ICAM-1 expression were enhanced in a dose- and time-dependent manner by IL-1 beta, TNF-alpha, or IFN-gamma, but not by IL-6 or IL-8. HLA-DR surface expression was induced only by IFN-gamma in a dose- and time-dependent manner, but not by the other cytokines tested. In contrast, the expression of LFA-3 and the CD44 molecule could be detected without the stimulation of any cytokine, but the levels of their expression were not significantly changed by any cytokines. The enhanced ICAM-1 expression by cytokines was reduced in a time-dependent manner following the removal of cytokines from the reaction mixture, while IFN-gamma-induced HLA-DR expression was maintained even 7 days after the removal of IFN-gamma. These data support an interactive role for inflammatory cytokines and the expression of adhesion molecules on gingival fibroblasts in the pathogenesis of gingival inflammation in periodontal disease.

Antigen-Presenting Cells↗