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Biomedical subjects

A Miyake

Publications and source records attributed to A Miyake.

At least 145 records · Page 8Linked to original sources
PubMed1994

Characterization of cloned human cholecystokinin-B receptor as a gastrin receptor.

The cholecystokinin (CCK)-B receptor cloned from human brain was characterized as a gastrin receptor by using heterologous expression systems of COS-7 cells and Xenopus oocytes. 125I-gastrin binding to human CCK-B receptor expressed in COS-7 was time-dependent, saturable and also specific, as well as 125-I-CCK-8. The binding of 125I-gastrin was inhibited by CCK-8 about 10-fold more potently than by gastrin. The rank order of potency of several antagonists to 125I-gastrin binding was YM022 > CI-988 > L-365,260 > L-364,718. Addition of GTP gamma S, a nonhydrolysable analog of GTP, dose-dependently inhibited 125I-gastrin binding, and lowered the gastrin binding affinity, Gastrin (10(-9)-10(-7) M) also evoked a Ca(2+)-dependent Cl- current in Xenopus oocytes expressing CCK-B receptors. These results suggest that the pharmacological profile of the cloned human CCK-B receptor using 125I-gastrin is closely parallel to that reported in gastric mucosa, and that the receptor transduces cellular signals of gastrin as well as those of CCK-8.

Amino Acid Sequence↗
PubMed1994

Characterization of rat pituitary cells by their responses to hypothalamic releasing hormones.

Rat pituitary cells in monolayer culture were characterized by their [Ca2+]i responses to hypothalamic releasing hormones, growth hormone (GHRH), thyrotropin-releasing hormone (TRH), gonadotropin-releasing hormone (GnRH) and corticotropin-releasing hormone (CRH). The percentages of the cell population responding to GHRH, TRH, GnRH, CRH and non-responding cells were 27.3%, 47.6%, 13.8%, 6.2% and 35.3%, respectively. Some of the cells responded to two or more of those hormones. In the GHRH-responding cells, the population of TRH-responding cells was 51.4%, In the TRH-responding cells, the population of GHRH-responding cells was 30.8%. Some of the GHRH-responding cells also responded to CRH and GnRH. In the GnRH-responding cells, the population of TRH-responding cells was 61.8%. In summary, GHRH-responding cells have an especially close relationship with TRH-responding cells, and GnRH-responding cells also have close relationship with TRH-responding cells. There is also some relationship between the populations responding to other pairs of releasing hormones. These findings suggest functional overlapping among each population of pituitary cells.

Animals↗
PubMed1994

A possible involvement of tyrosine kinase in TRH-induced prolactin secretion in GH3 cells.

Thyrotropin-releasing hormone (TRH) is a well-known regulatory factor of prolactin (PRL) secretion and synthesis in lactotrophs. Recently we have found that TRH stimulates early tyrosine phosphorylation of MAP kinase in GH3 cells. Then we investigated whether tyrosine phosphorylation in TRH action is involved in TRH-stimulated PRL secretion by GH3 cells, using a 4-hydroxycinnamamide derivative (ST638), a tyrosine kinase inhibitor. TRH-stimulated tyrosine phosphorylation of MAP kinase and PRL secretion were remarkably inhibited by ST638 treatment. These results suggest that tyrosine phosphorylation of MAP kinase is strongly associated with TRH-stimulated PRL secretion.

Animals↗
PubMed1994

Differential expression patterns of mRNAs for members of the fibroblast growth factor receptor family, FGFR-1-FGFR-4, in rat brain.

We have examined the region-specific expression of mRNAs for four members of rat FGF receptor family, FGFR-1, FGFR-2 FGFR-3, and FGFR-4, in rat brain by in situ hybridization. The FGFR-1, FGFR-2, and FGFR-3 mRNAs were expressed widely but differentially in the brain. However, the FGFR-4 mRNA was not expressed in the brain. The FGFR-1 mRNA was strongly expressed in several regions including the hippocampus, cerebellum, and pedunculopotine tegmental nucleus. The FGFR-2 mRNA expression was high in the choroid plexus, and moderate in the fiber-rich regions (the corpus callosum, external capsule, and internal capsule) and the olfactory bulb. The FGFR-3 mRNA was expressed diffusely in the brain. We have also examined the cellular localization of these mRNAs in the brain. Although the FGFR-1 mRNA was expressed preferentially in neurons, the FGFR-2 and FGFR-3 mRNAs were expressed preferentially in glial cells. The present findings that the FGFR-1, FGFR-2, and FGFR-3 mRNAs were expressed widely but with region- and cell-specificity in the brain indicate that these receptors have different roles in the brain.

Amino Acid Sequence↗
PubMed1994

Exogenous group II phospholipase A2 induces prostaglandin E2 production in mouse peritoneal macrophages.

Cultures of mouse peritoneal resident macrophages produced prostaglandin E2 when exposed to extracellular group II phospholipase A2. The response to group II phospholipase A2 was concentration dependent, and prostaglandin E2 production in response to 1 microgram/ml purified group II enzyme was comparable to the maximal response elicited by lipopolysaccharide. Group II phospholipase A2 required millimolar concentrations of extracellular Ca2+ for the induction of prostaglandin E2 production, as well as for phospholipase A2 activity. YM-26734 (4-(3,5-didodecanoyl-2,4,6-trihydroxyphenyl)-7-hydroxy-2-(4-hydroxyph eny l) chroman), a selective inhibitor of group II phospholipase A2, inhibited not only the enzyme activity but also the prostaglandin E2 production-inducing activity of group II phospholipase A2 in a concentration-dependent manner. These findings suggest that group II phospholipase A2 released into the extracellular space may induce prostaglandin E2 production through hydrolysis of plasma membrane phospholipids. Taken together with the previous finding that YM-26734 suppressed inflammatory responses in vivo, these results suggest that group II phospholipase A2 may play a role in the excitation and/or progression of inflammatory processes through the production of eicosanoids.

Animals↗
PubMed1994

Thyrotropin-releasing hormone stimulates MAP kinase activity in GH3 cells by divergent pathways. Evidence of a role for early tyrosine phosphorylation.

Regulation of the mitogen-activated protein (MAP) kinase by thyrotropin-releasing hormone (TRH) in GH3 rat pituitary tumor cells was investigated. Both TRH and epidermal growth factor (EGF) acutely activated this enzyme, via tyrosine and serine/threonine phosphorylation. Down-regulation of cellular protein kinase C (PKC) only partly inhibited the phosphorylation of MAP kinase by TRH, suggesting both PKC-dependent and -independent pathways. Both TRH and EGF similarly increased the phosphorylation of raf-1, by a PKC-independent mechanism. Both TRH and EGF stimulated the formation of a ras-GTP complex. This activation of ras by growth factors is thought to involve the tyrosine phosphorylation of Shc. EGF stimulated the tyrosine phosphorylation of three Shc proteins and their subsequent association with its receptor. TRH stimulated the tyrosine phosphorylation of the 52-kDa Shc protein, although neither phorbol esters nor the calcium ionophore A23187 had any effect, indicating that this effect of TRH was not dependent on PKC. Both TRH and EGF induced the association of tyrosine phosphorylated Shc proteins with a fusion protein containing SH2 and SH3 domains of Grb2, another important component in ras activation. These results provide evidence that MAP kinase is acutely activated by TRH through a PKC-dependent pathway as well as a second pathway possibly involving tyrosine phosphorylation.

Adaptor Proteins, Signal Transducing↗
PubMed1994

Rat FGF receptor-4 mRNA in the brain is expressed preferentially in the medial habenular nucleus.

The fibroblast growth factor (FGF) receptor family consists of four members, FGFR-1, FGFR-2, FGFR-3 and FGFR-4, that are closely related receptor tyrosine kinases. We examined the expression of rat FGFR-4 mRNA in the brain by in situ hybridization and compared it with that of the mRNAs for other FGF receptors. In contrast with FGFR-1, FGFR-2 and FGFR-3 mRNAs which are expressed widely in the brain, the FGFR-4 mRNA in the brain is expressed preferentially in the medial habenular nucleus neurons. The present finding indicates that FGFR-4 has a function specific to the medial habenular nucleus.

Animals↗
PubMed1994

The hypothalamic-pituitary-ovarian axis in patients with endometriosis is suppressed by leuprolide acetate but not by danazol.

OBJECTIVE: To investigate the effects of leuprolide acetate (LA), a GnRH agonist (GnRH-a), and of danazol on the hypothalamic-pituitary-ovarian axis in patients with endometriosis. DESIGN: Ten patients were divided into LA and danazol treatment groups. MEASURES: Serum levels of E2, immunoreactive and bioactive LH, pulsatility of LH, and gonadotropins release by GnRH. Changes in serum E2 levels by hMG administration during LA treatment. RESULTS: Serum E2 level decreased to near castrated levels during the LA treatment, while it remained unchanged during the danazol treatment. Leuprolide acetate administration resulted in a significant suppression of the serum level of bioactive LH, of the pulsatility of LH release, of the pituitary response to GnRH injection, and of the elevation in the serum E2 level by hMG administration, but danazol treatment did not show these suppressive effects. CONCLUSION: Our results suggest that the hormonal actions of LA and danazol on endometriosis are different from each other, especially in the suppression of serum E2 level.

Adult↗
PubMed1994

Roles of prostaglandins and intracellular free calcium mobilisation in epidermal growth factor-induced proliferation of human amnion cells.

OBJECTIVE: To investigate the mechanisms which regulate the growth of human amnion cells. DESIGN: A prospective descriptive study. SUBJECTS: Women undergoing caesarean section at term before the onset of labour. INTERVENTIONS: Amnion cells were cultured in monolayer. MAIN OUTCOME MEASURES: Cell cycle analysis, intracellular calcium levels, prostaglandin (PG) production rates. RESULTS: Epidermal growth factor (EGF) stimulated intracellular Ca2+ mobilisation and PGE2 production in cultured amnion cells. The addition of a Ca2+ channel blocker (cobalt) or a Ca2+ chelator (EGTA) into the culture medium inhibited intracellular Ca2+ mobilisation and PGE2 production induced by EGF. The analysis of cell cycles showed that EGF induced the initiation of DNA synthesis and that the addition of cobalt or EGTA into the culture medium inhibited EGF-induced DNA synthesis. The addition of a cyclo-oxygenase inhibitor (indomethacin) inhibited PGE2 production and DNA synthesis induced by EGF without the effect on intracellular Ca2+ mobilisation. Moreover, the inhibitory effect of indomethacin on EGF-induced DNA synthesis was attenuated by the addition of exogenous PGE2 or PGF2 alpha. CONCLUSIONS: These data suggest that EGF induces an increase in intracellular Ca2+ levels and the rate of prostaglandin production which leads to proliferation of human amnion cells.

Amnion↗
PubMed1994

Expression of epidermal growth factor and transforming growth factor-alpha in fallopian tube epithelium and their role in embryogenesis.

We studied the expression of epidermal growth factor (EGF) and transforming growth factor (TGF)-alpha in human fallopian tube epithelium at various menstrual stages. Immunohistochemical staining using anti-EGF and anti-TGF-alpha antibodies showed a specific staining in ampullary tube epithelium at late follicular and luteal stages but the staining was very weak at the early follicular stage. Quantitative reverse transcription and polymerase chain reaction (RT-PCR) using beta-actin mRNA as an internal standard revealed the menstrual-stage-specific expression of EGF and TGF-alpha gene transcripts: amounts of EGF and TGF-alpha mRNA relative to those of beta-actin were significantly higher at late follicular and luteal stages than at the early follicular stage. To clarify the biological role of these growth factors, mouse 2-cell embryos were cocultured with human fallopian tube epithelial cells with or without blocking the action of these growth factors. Cocultures significantly promoted blastocyst formation, but this promotive effect of the tubal epithelial cells was completely abolished by the addition of anti-EGF and/or anti-TGF-alpha monoclonal neutralizing antibodies to the coculture system. These results demonstrated that EGF and TGF-alpha were synthesized and expressed in fallopian tube epithelium at specific menstrual stages, and may be involved in early embryonic development.

Animals↗
PubMed1994

Epidermal growth factor promotes adipogenesis of 3T3-L1 cell in vitro.

We have reported the importance of epidermal growth factor (EGF) for the induction of obesity in mice. In this study, we studied the effects of EGF on the induction of lipogenic enzymes and on the accumulation of triglyceride in a differentiated mouse adipocyte cell in vitro. Mouse 3T3-L1 preadipocytic cells differentiated into mature adipocytes after the differentiation procedure by insulin, dexamethasone, and methyl-isobutyl-xanthine. 125I-EGF binding studies in the differentiated 3T3-L1 cells showed specific 125I-EGF bindings, and they expressed gene transcripts for EGF receptors by reverse transcription and polymerase chain reaction at all differentiative stages examined. Although EGF showed inhibitory effects on the triglyceride accumulation when administered to the preadipocytic 3T3-L1 cells, EGF enhanced the adipogenesis in the differentiated cells in dose- and time-dependent manners. Administration of EGF at 0.1-1 nM from 4 days after the differentiation procedure for 10 days, significantly enhanced the acyl-Co A synthetase and lipoprotein lipase messenger RNA levels, both of which are rate-limiting enzymes to synthesize triglyceride in adipocytes. Moreover, 0.1-1 nM EGF increased the amounts of triglyceride accumulated in the cells, in proportion to the acyl-Co A synthetase and lipoprotein lipase messenger RNA levels. EGF rather failed the adipogenesis at 10 nM. Time course studies revealed that 1 nM EGF significantly increased the intracellular triglyceride levels from 4 through 16 days administration. These results suggest that EGF shows biphasic effects on adipocytes: although EGF inhibits preadipocytes differentiation into mature adipocytes, it promotes adipogenesis in the differentiated adipocytes.

3T3 Cells↗
PubMed1994

Identification of estrogen receptor in human adipose tissue and adipocytes.

Estrogen has various effects on adipose tissue. Although the presence of estrogen receptor (ER) has been demonstrated in rat adipose tissue and adipocytes, ER has not been identified in human adipose tissue. In this study, we demonstrated the existence of ER protein and ER messenger RNA (mRNA) in human sc adipose tissue and adipocytes. The cytosol fraction of human adipose tissue was partially purified by ammonium sulfate precipitation, and the presence of ER protein was analyzed by [3H]estradiol (E2) binding assay and Western blot analysis. [3H]E2 binding assay showed a low specific binding due to high nonspecific binding, and the dissociation constant (Kd) and maximal binding sites could not be obtained by Scatchard analysis. Western blots, however, showed the presence of ER protein in both the partially purified cytosol and nuclear fractions of human adipose tissue. The mol wt of ER in both fractions was approximately 66,000. Furthermore, Northern blot analysis of total RNA samples isolated from human adipose tissue showed the expression of ER mRNA at 6.2 kilobase in size. ER mRNA was also identified in isolated human adipocytes by the reverse transcription and polymerase chain reaction. These results indicated that both ER protein and ER mRNA are expressed in human adipocytes, suggesting that the effect of estrogen on human adipose tissues might involve a direct action.

Adipocytes↗
PubMed1994

Involvement of autocrine mechanism of transforming growth factor-beta in the functional differentiation of pregnant mouse mammary gland.

We studied the presence and possible role of the autocrine mechanism of transforming growth factor-beta (TGF-beta) in pregnant mouse mammary gland. Northern blot analysis revealed the expression of the TGF-beta 1 gene transcript at 2.5 kb in mammary epithelial cells isolated from virgin and mid-pregnant mice. The TGF-beta activity was higher in the conditioned medium from mid-pregnant mouse mammary explants than that from virgin explants by a bioassay system using mink lung epithelial cells. A binding study using [125I]TGF-beta 1 as a ligand showed that pregnant mouse mammary epithelial cells possessed a single class of high-affinity TGF-beta 1 binding sites (Kd = 28.0 pmol/l, 1.2 x 10(4) sites per cell). These results suggested the presence of a TGF-beta autocrine mechanism in pregnant mouse mammary epithelial cells. Next, we examined the effect of TGF-beta 1 on the functional differentiation of pregnant mouse mammary gland. Transforming growth factor-beta 1 inhibited alpha-lactalbumin production in cultured mammary explants from mid-pregnant mice in a dose-dependent manner without inhibiting DNA synthesis. All these results suggest that TGF-beta may play a role in regulating the functional differentiation of mouse mammary glands during pregnancy.

Animals↗
PubMed1994

Selective inhibition of mouse placental lactogen II secretion by tumour necrosis factor-alpha.

The placental members of the prolactin-GH-placental lactogen (PL) gene family of the mouse include mPL-I, mPL-II, proliferin (PLF) and proliferin-related protein (PRP). The aim of the present study was to assess the effects of tumour necrosis factor-alpha (TNF-alpha) on the secretion of these proteins in primary cultures of placental cells from days 7, 9 and 12 of pregnancy. The effects of epidermal growth factor (EGF) on the secretion of PLF and PRP were also determined. EGF has previously been shown to stimulate mPL-I and inhibit mPL-II secretion. Incubation of placental cells from day 7 of pregnancy for 5 days with 10 nmol human (h)TNF-alpha/l did not affect the mPL-II concentration of the medium, but similar treatment of cells from days 9 or 12 of pregnancy resulted in a significant reduction in the mPL-II concentration of the medium by the second or third day of culture. The intracellular concentration of mPL-II, the number of cells that released mPL-II as assessed by reverse haemolytic plaque assay, and steady-state levels of mPL-II mRNA as assessed by Northern analysis were also reduced by hTNF-alpha treatment. The lowest concentration of hTNF-alpha that significantly inhibited mPL-II secretion by cells from day 12 of pregnancy was 0.01 nmol/l. hTNF-alpha treatment did not affect the secretion of mPL-I, PLF or PRP, as assessed by the concentrations of these proteins in the medium during a 5-day incubation. Incubation of the cells with 20 ng EGF/ml also did not affect the PLF or PRP concentration of the medium during 5 days of culture. To determine whether the effect of hTNF-alpha on mPL-II secretion was mediated by interleukin-6 (IL-6), the IL-6 concentration of the medium of control and hTNF-alpha-treated cells was determined. Bioactive and immunoreactive IL-6 could not be detected in medium from either treatment group. The presence of binding sites for hTNF-alpha was assessed in cells from day 12 of pregnancy. Scatchard analysis detected a single class of binding sites having a Kd of 1.61 +/- 0.34 nmol/l, with about 1350 sites per cell. The results of this study demonstrate that hTNF-alpha inhibits the secretion of mPL-II by placental cells from days 9 and 12 of pregnancy, suggesting that TNF-alpha may be one of the factors that regulate the production of this hormone in vivo.

Animals↗
PubMed1994

Involvement of epidermal growth factor (EGF)/EGF receptor autocrine and paracrine mechanism in human trophoblast cells: functional differentiation in vitro.

We have studied the expression of epidermal growth factor (EGF) and EGF receptors (EGF-R) in isolated human trophoblast cells at various stages of differentiation and also the biological significance of the EGF/EGF-R autocrine and paracrine mechanism. Cytotrophoblast cells were isolated from human placental tissues of 6-9 weeks of gestation. Trophoblast cells underwent morphological and functional differentiation during in vitro culture. The expression of EGF and EGF-R protein and mRNA was studied in trophoblast cells cultured for 0-5 days, using immunocytochemical staining, and reverse transcription and polymerase chain reaction. Monoclonal antibodies (mAbs) against EGF and EGF-R showed specific staining in trophoblast cells at all stages of differentiation. Both EGF and EGF-R gene transcripts were detected in RNA samples isolated from trophoblast cells at all stages. These data suggest the presence of an EGF/EGF-R autocrine and paracrine mechanism in human trophoblast cells. Next, we examined the biological significance of this mechanism on trophoblast cell differentiation in vitro. EGF added to the culture medium significantly increased human chorionic gonadotrophin-beta (hCG-beta) secretion and, more importantly, anti-EGF neutralizing mAbs significantly reduced both hCG-beta and human placental lactogen secretion from trophoblast cells in culture. All these results suggest that human trophoblast cells express both EGF and EGF-R, and that EGF may play an important role in the functional differentiation of human trophoblast cells.

Base Sequence↗
PubMed1994

HTLV-I seroprevalence in patients with undefined uveitis in central Japan.

Recently, human T-lymphotropic virus type I (HTLV-I) has been shown to cause endogenous uveitis, HTLV-I associated uveitis. To investigate the association of hereditary or environmental factors with the incidence of this uveitis, HTLV-I seroprevalence was studied in patients with undefined uveitis in central Japan, where HTLV-I infection has not been considered highly endemic. Of 129 patients with undefined uveitis, 6 (4.6%) were seropositive, and 4 of these 6 seropositive cases with undefined uveitis were born in southwestern Japan, where HTLV-I infection is highly endemic. As regards the incidence rate of uveitis, 4 of 9 (44.4%) seropositive cases from southwestern Japan developed uveitis, whereas only 2 of 21 (9.5%) seropositive cases from central Japan developed uveitis. The difference was statistically significant (P < 0.05). This results suggests that the incidence of HTLV-I associated uveitis could be influenced by environmental or hereditary factors including HLA.

Adolescent↗
PubMed1993

Interleukin 6 inhibits mouse placental lactogen II but not mouse placental lactogen I secretion in vitro.

The mouse placenta produces several polypeptides belonging to the prolactin-growth hormone gene family, including mouse placental lactogen (mPL) I and mPL-II. The present study was undertaken to determine whether the secretion of mPL-I and mPL-II is regulated by interleukin 6 (IL-6), which is present in the placenta and has previously been reported to stimulate the secretion of pituitary members of this gene family. Effects of human and mouse IL-6 on mPL-I and mPL-II secretion were examined in primary cultures of placental cells from days 7, 9, and 12 of pregnancy. IL-6 caused a dose-dependent reduction in the mPL-II concentration in the medium of cells from days 9 and 12 of pregnancy but did not affect the mPL-II concentration in the medium of cells from day 7 of pregnancy or the mPL-I concentration in the medium of cells from days 7 or 9 of pregnancy. The lowest concentration of human IL-6 that significantly inhibited mPL-II secretion was 250 pM. The effect of IL-6 on the mPL-II concentration in the medium was due primarily to inhibition of mPL-II synthesis, which resulted at least partly from a decrease in the steady-state level of mPL-II mRNA. These data raise the possibility that IL-6 may regulate mPL-II production after midpregnancy in vivo.

Animals↗