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Biomedical subjects

A Miyake

Publications and source records attributed to A Miyake.

At least 73 records · Page 4Linked to original sources
PubMed1997

Bihormonal cells secreting both prolactin and gonadotropins in normal rat pituitary cells.

The present study was designed to characterize bihormonal cells in rat pituitary cells which secrete PRL and gonadotropins. This was done by using sandwich cell immunoblot assay (CIBA) and reverse hemolytic plaque assay (RHPA) in combination with immunocytochemistry (ICC) and by measuring the intracellular free calcium concentration ([Ca2+]i). The result of the experiment with sandwich CIBA revealed that the populations of LH- and FSH-secreting cells in the PRL-secreting cells were 6.23% and 5.91%, respectively, and the populations of the PRL secreting cells in the LH- and FSH-secreting cells were 18.4% and 15.5%, respectively. Additional studies by the combined techniques of RHPA with ICC revealed that the populations of LH- and FSH-containing cells in the PRL secreting cells were 4.43% and 2.40%, respectively, which were consistent with the results of Sandwich CIBA. Some of the PRL-secreting cells determined by RHPA showed responsiveness to TRH and GnRH in [Ca2+]i. These results suggest that bihormonal cells which secrete both PRL and LH, or both PRL and FSH are present in the normal rat pituitaries.

Animals↗
PubMed1997

Participation of JAK, STAT and unknown proteins in human placental lactogen-induced signaling: a unique signaling pathway different from prolactin and growth hormone.

The signal transduction mechanism involved in human placental lactogen (hPL) was studied. We have identified that hPL rapidly stimulated the tyrosine phosphorylation of at least 7 proteins including Janus Kinases (JAK1 and JAK2) and a signal transducer and activator of transcription protein (Stat3). This is the first evidence that the JAK-STAT pathway is involved in the hPL signaling. Moreover, two unknown proteins which were different from STAT proteins (Stat1, 3 and 5) in sizes were predominantly tyrosine-phosphorylated. Because human growth hormone (hGH) activates Stat1, 3, 5 and human prolactin (hPRL) activates Stat5, these results show that hPL uses a unique signal transduction pathway which is different from hGH and hPRL.

Acute-Phase Proteins↗
PubMed1997

Involvement of SNAP-25 in TRH-induced exocytosis in pituitary GH4C1 cells.

The synaptic membrane protein synaptosomal-associated protein (SNAP-25) has recently been implicated as one of the key proteins involved in exocytotic membrane fusion in neurons. However, the role of SNAP-25 in pituitary hormone release is not known. In this study, we determined that SNAP-25 is involved in regulated exocytosis in the clonal pituitary cell line GH4C1. SNAP-25 messenger RNA and protein were detected in GH4C1 cells by RT-PCR and immunoblot analysis, respectively. Immunofluorescence analysis indicated that SNAP-25 protein was localized in the plasma membrane. Next, to determine the function of SNAP-25 in GH4C1 cells, specific inhibitors of SNAP-25, botulinum neurotoxin (BoNT)/A or /E, and antisense SNAP-25 oligonucleotide were used. Neither BoNT/A nor BoNT/E affected thyrotropin-releasing hormone (TRH)-induced cytosolic Ca2+ increase, but both inhibited TRH-induced exocytosis. Moreover, they dose-dependently inhibited TRH-induced prolactin release. The introduction of antisense oligonucleotide into the cells also inhibited TRH-induced prolactin release. These results suggest that SNAP-25 is involved in regulated exocytosis in GH4C1 cells.

Calcium↗
PubMed1997

[Possibility of drug design of beta-lactam antibiotics effective for multiresistant gram-positive pathogens].

Since infectious diseases are caused by various bacteria and most of them are treated empirically, broad-spectrum antibiotics are required. To expand the spectrum, an imidazopyridazinium group and aminothiadiazole group were introduced to 3- and 7-side chain of cephem nucleus, respectively. The resulting compound, cefozopran, was able to permeate not only outer membrane of Pseudomonas aeruginosa but also envelope of gram-positive bacteria, which functioned as a barrier to antipseudomonal cephalosporins, and showed potent activity against wide variety of bacteria including those which produced a large amount of cephalosporinase and were resistant to third-generation cephalosporins. In spite of the broad antibacterial spectrum, cefozopran only weakly affected gastrointestinal flora of mice and prevented colonization by MRSA.

Animals↗
PubMed1996

The role of mitogen-activated protein kinase in oxytocin-induced contraction of uterine smooth muscle in pregnant rat.

Oxytocin causes the rapid tyrosine phosphorylation of mitogen-activated protein (MAP) kinase in both human and rat puerperal uterine myometrial cultured cells. The potential role of the MAP kinase pathway in oxytocin action was investigated with the specific MAP kinase kinase (MEK) inhibitor, PD98059. Oxytocin stimulation of the tyrosine phosphorylation of MAP kinase in both human and rat cultured puerperal uterine cells was abolished by pretreatment of the cells with MEK inhibitor in a dose-dependent manner. Although MEK inhibitor had no effect on oxytocin-induced intracellular Ca2+ mobilization in either pregnant human or pregnant rat uterine cells, it partly inhibited oxytocin-induced pregnant rat uterine contraction in a dose-dependent manner. These results suggest that MAP kinase pathway may have some important roles in oxytocin-induced uterine contraction.

Animals↗
PubMed1996

Transforming growth factor-alpha promotes tumor markers secretion from human ovarian cancers in vitro.

BACKGROUND: The regulatory mechanism of tumor markers secretion has not been well clarified. METHODS: Serum levels of CA 125 and tissue polypeptide antigen (TPA) from 17 patients with Stage III serous cystadenocarcinoma were measured prior to an initial surgical treatment. Epidermal growth factor receptor (EGFR) status was examined by an 125I-EGF binding assay in a human serous cystadenocarcinoma cell (SHIN-3) and in the 17 primary carcinomas. SHIN-3 cell and the EGFR-expressing primary cancer cells (n = 4) were cultured with or without various concentrations of transforming growth factor (TGF-alpha), a ligand for EGFR, and the CA 125 and TPA concentrations in the conditioned media were measured. RESULTS: EGFR was expressed in 12 primary carcinomas and in the SHIN-3 cell, and it was absent in the remaining 5 carcinomas. Pre-therapeutic serum CA 125 and TPA levels were significantly greater (P < 0.05) in patients with EGFR-expressing carcinomas (n = 5). These data suggest a possible involvement of EGFR in regulating these tumor markers secretion. TGF-alpha increased the CA 125 and TPA secretion from SHIN-3 cell. It also promoted the CA 125 secretion in 2 of 4 EGFR-expressing primary ovarian carcinoma specimens. CONCLUSIONS: These results suggest that a signal through the EGFR may be involved in regulating the CA 125 and TPA secretion from human ovarian carcinomas.

Binding Sites↗
PubMed1996

Rat oligodendrocytes and astrocytes preferentially express fibroblast growth factor receptor-2 and -3 mRNAs.

Fibroblast growth factors (FGFs) exert various effects on glial cells as well as on neurons in the brain. The mRNAs for four FGF receptors (FGFR-1-FGFR-4) are expressed in the brain. Although FGFR-1 and -4 mRNAs are preferentially expressed in neurons, FGFR-2 and -3 mRNAs are preferentially expressed in glial cells. However, the glial cells that express these receptors remained to be identified. In this study, we found that oligodendrocytes and astrocytes in the brain preferentially expressed FGFR-2 and FGFR-3 mRNAs, respectively. The isoforms of immunoglobulin-like domain III (IIIb and IIIc) of the receptors have crucial roles in ligand binding. We also determined the isoforms of FGFR-2 and FGFR-3 expressed in glial cells to be of type IIIc. The expression of FGFR-2 IIIc and FGFR-3 IIIc with different ligand specificities might play important roles in the various effects of FGFs on oligodendrocytes and astrocytes.

Alternative Splicing↗
PubMed1996

Structure and expression of the rat mRNA encoding a novel member of the fibroblast growth factor family.

We isolated the cDNA encoding a novel member of the fibroblast growth factor (FGF) family from rat embryos by homology-based polymerase chain reaction. The FGF-related cDNA encodes a protein of 215 amino acids (approximately 24 kDa), which has a conserved approximately 120-amino acid core with approximately 30-60% amino acid sequence identity with the FGF family. This protein with a hydrophobic amino terminus appears to be a secreted protein. The cDNA was translated in a coupled in vitro transcription-translation system. The molecular mass of the translation product was observed to be approximately 26 kDa. The expression of the FGF-related mRNA in the rat embryo and adult tissues was determined by Northern analysis and in situ hybridization. The mRNA was expressed in several discrete regions of the embryo. In adult tissues, the mRNA was preferentially expressed in the lung. The expression profile of the FGF-related mRNA was different from those of other FGF family mRNAs. As this protein is the 10th documented protein related to FGFs, we tentatively term this protein FGF-10.

Amino Acid Sequence↗
PubMed1996

G protein-gated K+ channel (GIRK1) protein is expressed presynaptically in the paraventricular nucleus of the hypothalamus.

We prepared a specific antibody against GIRK1, the major subunit of the G protein-gated K+ (KG) channel. Immunohistochemical study revealed that GIRK1 immunoreactivity was detected in the presynaptic, but not in the postsynaptic, region in the paraventricular nucleus of the rat hypothalamus (PVN). Therefore, activation of the KG channel may underlie presynaptic inhibition of neurotransmitter release by various agonists, such as dopamine, noradrenaline, opioids, and histamine, in PVN.

Adenosine↗
PubMed1996

Comparison of [3H]YM060 binding to native and cloned rat 5-HT3 receptors.

We characterized [3H]YM060 ([methyl-3H]-(-)-(R)-5-[(methyl-1H- indol-3-yl)carbonyl]-4,5,6,7-tetrahydro-1H-benzimidazole monohydrochloride) binding in membrane homogenates prepared from three different rat tissues (cerebral cortex, ileum and colon), and compared the binding characteristics between the native and cloned rat 5-HT3 receptors. The dissociation constant (Kd) of [3H]YM060 was similar in all membranes. In competition studies, the affinity of 5-HT3 receptor agonists and antagonists was similar between the native and the cloned rat 5-HT3 receptors. In conclusion, intra-species difference of 5-HT3 receptor was not observed in rats and pharmacological properties of the cloned rat 5-HT3 receptor were nearly identical to that of the native rat 5-HT3 receptor.

Animals↗
PubMed1996

Rat fibroblast growth factor receptor-4 mRNA in the brain is preferentially expressed in cholinergic neurons in the medial habenular nucleus.

We examined the cellular localization of fibroblast growth factor receptor (FGFR)-4 mRNA preferentially expressed in the medial habenular nucleus by in situ hybridization. FGFR-4 mRNA was expressed in the ventral part of the medial habenular nucleus. FGFR-4 mRNA was colocalized with choline acetyltransferase mRNA to a high degree (more than 90%), indicating that FGFR-4 mRNA-expressed cells are cholinergic neurons. The present finding indicates that FGFR-4 in the brain has a function specific to cholinergic neurons in the ventral part of the medial habenular nucleus.

Acetylcholine↗
PubMed1996

Regulation of mouse placental lactogen secretion by G proteins before midpregnancy.

To determine whether G proteins are involved in the regulation of mouse placental lactogen-I (mPL-I) and/or mPL-II secretion before midpregnancy, mouse placental tissue from day 7 of pregnancy was dispersed with collagenase, cells were fractionated on a percoll gradient, and the purified trophoblast cells were cultured in a serum-free medium with cholera toxin (CTX) or pertussis toxin (PTX) which modulate the activities of distinct G proteins for 5 days. CTX inhibited both mPL-I and mPL-II secretion, but PTX inhibited mPL-I secretion and stimulated mPL-II secretion in a time- and dose-dependent manner. Addition of both CTX and PTX additionally inhibited mPL-I secretion but did not affect mPL-II secretion. 8-Bromo cAMP, which increases intracellular cAMP accumulation, inhibited both mPL-I and mPL-II secretion similarly to CTX. In contrast, H8, an inhibitor of cAMP-dependent protein kinase A, stimulated both mPL-I and mPL-II secretion. Addition of PTX and H8 synergistically stimulated mPL-II secretion. These findings suggest that G proteins play important roles in regulation of mPL-I and mPL-II secretion before midpregnancy.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1996

Gestational changes of glucose transporter gene expression in the mouse placenta and decidua.

Glucose is required for fetal development and energy metabolism. The glucose transfer from maternal circulation to fetus, in which glucose transporter (GLUT) should play an important role, is fundamental in the utero-placental-fetal system. In this study, the gestational changes of GLUT1 and GLUT3 mRNA level in the mouse placenta and decidua were analyzed by Northern blot analysis. The levels of GLUT1 mRNA in the mouse placenta and decidua increased as gestational day proceeded. Although the level of GLUT3 mRNA in the decidua slightly decreased as pregnancy proceeded, there was a switch in size of a major band of GLUT3 from 4.1 kb to 2.7 kb in the mouse placenta detected by Northern blot analysis. These findings suggest the presence of a difference in the gestational modulation of the level of GLUT1 and GLUT3 in the uteroplacental system.

Animals↗
PubMed1996

Intraventricular administration of estradiol modulates rat prolactin secretion and synthesis.

The effect of estradiol (E2) on rat tuberoinfundibular dopaminergic (TIDA) neurons was examined in vivo, employing chronic intraventricular (i.c.v.) infusion technique using an osmotic mini-pump. The activity of TIDA neurons was assessed by the release and synthesis of prolactin (PRL) in the rat pituitary gland and by the changes in the 3, 4-dihydroxyphenylacetic acid (DOPAC) and dopamine (DA) levels and in the DOPAC/DA ratio in the rat hypothalamus. We also examined the [3H] E2 binding in the rat hypothalamus. Ovariectomized female Wistar rats with E2 replacement were treated with daily i.c.v. infusion of 1 microM of E2 or saline vehicle for 1, 3, and 7 days using the Alzet osmotic mini-pump and brain infusion kit. At 1 day of i.c.v. infusion of E2, the serum PRL level was significantly decreased compared with that in the vehicle group. Northern blot analysis of the total RNA isolated from the pituitary glands demonstrated a decrease in the PRL gene transcript level in the E2 group. At 3 days of E2 treatment, however, the serum PRL level was significantly increased compared with that of the vehicle-injected group and Northern blot analysis also demonstrated that the PRL gene transcript level was increased in the E2 group. At 7 days of E2 administration, there were no significant differences between the E2 and vehicle groups in either serum PRL or PRL gene transcript levels. There was a significant increase in the DOPAC/DA ratio after 1 day in the E2 group. However, no significant effects of E2 on this ratio were observed at 3 and 7 days of treatment. The DOPAC concentration in the E2 group was significantly increased at day 1 and significantly decreased at day 3, compared with that of the respective time in vehicle group. At day 7 there was no significant change in DOPAC concentration in either groups. The DA concentrations in the hypothalamus was not changed on any day in either group. Specific [3H] E2 binding was observed in the rat hypothalamus. These data suggest that E2 may have a biphasic effect on the accumulation of PRL gene transcripts and on the PRL secretion in the rat pituitary by first stimulating and then inhibiting the TIDA neuronal activity.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1996

Regulation of mouse placental lactogen-II secretion by transforming growth factor-alpha after midpregnancy.

We investigated whether transforming growth factor-alpha (TGF-alpha) regulates mouse placental lactogen-II (mPL-II) secretion by cells from day 12 of pregnancy. TGF-alpha significantly inhibited mPL-II secretion by the third and fourth day of culture, and then stimulated mPL-II secretion from the sixth day. The inhibitory and stimulatory effects of TGF-alpha on mPL-II secretion were dose-dependent, and the lowest concentration of TGF-alpha-which caused significant inhibition or stimulation of mPL-II secretion was 10 ng/ml. When TGF-alpha treatment of placental cells was begun on the fifth day of the culture, significant stimulation of mPL-II secretion was observed 3 days later. TGF-alpha inhibited steady-state levels of mPL-II mRNA on the third day of culture but stimulated steady-state levels of mPL-II mRNA on the seventh day of culture. These results suggest that TGF-alpha biphasically regulates mPL-II secretion through regulation of mPL-II gene expression after midpregnancy.

Animals↗