Y. A. Fontaine

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In freshwater or seawater female silver eel, the release of gonadotropin (GTH) accumulated in the pituitary under estradiol (E2) influence could be stimulated by a conjugated treatment with a mammalian gonadoliberin agonist (GnRH-A = des-Gly10, (D-Ala6)-LH-RH ethylamide) and a blocker of dopamine receptor (pimozide). Furthermore, despite the GTH release, no(More)
The gonadotrophic function of the European eel (Anguilla anguilla L.) at the silver stage is very weak: gonadotrophin-releasing hormone (GnRH) secretion is deficient and, moreover, dopamine inhibition overrides GnRH action. At the silver stage, oestradiol stimulates the biosynthesis of the type-II gonadotrophin (GTH-II). To study the molecular mechanism of(More)
In teleosts, the pituitary contains a single glycoprotein gonadotropic hormone (GTH) composed of two dissimilar alpha- and beta-subunits. The European eel, Anguilla anguilla L, is sexually immature at the silver stage due to a deficiency in GTH synthesis and secretion. In previous studies we (S.D., YA.F.) have demonstrated a strong stimulatory action of(More)
Gonadotropin-releasing hormone (GnRH) peptides in the brain and pituitary of the European eel (Anguilla anguilla) were investigated by reverse phase high performance liquid chromatography (HPLC) and radioimmunoassay with region-specific antisera. Two GnRH molecular forms were demonstrated in brain and pituitary extracts. One form eluted in the same position(More)
Oestradiol treatment enhances type-II gonadotrophin (GTH-II) synthesis in the European eel (Anguilla anguilla) at the silver stage. As a first step in studying the molecular mechanisms involved in this stimulation, we cloned and characterized the cDNA encoding the beta subunit of eel GTH-II. A cDNA library was constituted in lambda gt10 from(More)
Human chorionic gonadotrophin (hCG) increased cyclic adenosine monophosphate (cAMP) in pieces of eel ovary in vitro. Although the ED50 (about 0.1 micrograms/ml) was the same as for carp gonadotrophin (cGTH), the maximal stimulation (close to 3 times basal level) was about 10 times lower than that for the fish hormone. The mechanism of this atypical action(More)
A cDNA library constructed using mRNAs isolated from pituitary glands of estradiol-treated eels was screened with a cDNA fragment for the rat glycoprotein hormone alpha-subunit. Three out of 10,000 cDNA clones were revealed and subcloned in pUC13 for characterization and sequencing. All three had the same nucleotide sequence except for a single, silent(More)
Cyclic AMP (cAMP) in pieces of eel ovary was greatly increased in vitro by the gonadotropin (cGTH) of carp, another teleost fish; after one hour at 20 degrees C, maximal stimulation = 31.7 and E.D. 50 = 0.08 micrograms/ml. Ovine lutropin (oLH) had less effect (maximal stimulation: 2.35; E.D. 50: 1.42 micrograms/ml); its action suggested that it involved a(More)
Eel brain contains a factor which exhibited a complete cross-reaction in a radioimmunoassay (RIA) for mammalian luteinizing hormone-releasing hormone (LHRH) and which exhibited a behavior similar to that of synthetic mammalian LHRH on Sephadex G-25. Eel brains contained 920 +/- 135 pg of this LHRH-like immunoreactive factor (IR-LHRH); 75% of(More)
We obtained the sequence of eel thyrotropin beta-subunit cDNA. About 1,100 bp long, it encodes a 147-amino acid protein including a 20-residue signal peptide. We analyse homologies between angTSH beta and the other known beta-subunits taking in account the ability of mammal gonadotropins (GTH) to stimulate teleost thyroid. A peptide corresponding to(More)