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Insulin-like growth factor (IGF)-I, which is crucially involved in fish growth, differentiation, and reproduction, occurs in tilapia pituitary. IGF-I peptide, which is probably produced in hypothalamic perikarya, is present in axons of the neurohypophysis, and IGF-I mRNA and peptide are present in the adenohypophysis in adrenocorticotrophic hormone cells, melanocyte-stimulating hormone cells, with interindividual differences in growth hormone cells, and, starting with puberty, in gonadotrophic hormone (GTH) cells. Subordinate males showed a high IGF-I but a lower beta-luteinizing hormone expression, while in dominant males the opposite was found. IGF-I from the GTH cells may act as auto/paracrine regulators of GTH cell proliferation and enhance GTH synthesis and release during puberty and reproduction, depending on the social status.

Background The hormonal control of oocyte maturation and ovulation as well as the molecular mechanisms of nuclear maturation have been thoroughly studied in fish. In contrast, the other molecular events occurring in the ovary during post-vitellogenesis have received far less attention. Methods Nylon microarrays displaying 9152 rainbow trout cDNAs were hybridized using RNA samples originating from ovarian tissue collected during late vitellogenesis, post-vitellogenesis and oocyte maturation. Differentially expressed genes were identified using a statistical analysis. A supervised clustering analysis was performed using only differentially expressed genes in order to identify gene clusters exhibiting similar expression profiles. In addition, specific genes were selected and their preovulatory ovarian expression was analyzed using real-time PCR. Results From the statistical analysis, 310 differentially expressed genes were identified. Among those genes, 90 were up-regulated at the time of oocyte maturation while 220 exhibited an opposite pattern. After clustering analysis, 90 clones belonging to 3 gene clusters exhibiting the most remarkable expression patterns were kept for further analysis. Using real-time PCR analysis, we observed a strong up-regulation of ion and water transport genes such as aquaporin 4 (aqp4) and pendrin (slc26). In addition, a dramatic up-regulation of vasotocin (avt) gene was observed. Furthermore, angiotensin-converting-enzyme 2 (ace2), coagulation factor V (cf5), adam 22, and the chemokine cxcl14 genes exhibited a sharp up-regulation at the time of oocyte maturation. Finally, ovarian aromatase (cyp19a1) exhibited a dramatic down-regulation over the post-vitellogenic period while a down-regulation of Cytidine monophosphate-N-acetylneuraminic acid hydroxylase (cmah) was observed at the time of oocyte maturation. Conclusion We showed the over or under expression of more that 300 genes, most of them being previously unstudied or unknown in the fish preovulatory ovary. Our data confirmed the down-regulation of estrogen synthesis genes during the preovulatory period. In addition, the strong up-regulation of aqp4 and slc26 genes prior to ovulation suggests their participation in the oocyte hydration process occurring at that time. Furthermore, among the most up-regulated clones, several genes such as cxcl14, ace2, adam22, cf5 have pro-inflammatory, vasodilatory, proteolytics and coagulatory functions. The identity and expression patterns of those genes support the theory comparing ovulation to an inflammatory-like reaction.

Evaluating the ecological impact of an oil spill is a complex issue requiring coherently articulated examination of the sequence of interactions that link the cell, where contaminants exert their effects, to the ecosystem, where interactions with human activities arise. This sequence of interactions traverses the frontiers between scientific disciplines (chemistry, toxicology, physiology, and fisheries ecology). Using the common sole (Solea solea L.) as a model species for the coastal habitats polluted by the "Erika" oil spill, our research project attempted to define indices of functional integrity that characterised the consequences of fuel exposure at the different biological levels. The coupling of field observations with experimental laboratory work revealed how functional alterations which are readily observable within individuals and their organs are progressively obscured as investigation progresses towards more complex organisational levels. Some of the approaches and indices are proposed as instruments for evaluating the impact of contamination by hydrocarbons., L'évaluation des conséquences écologiques d'une marée noire est un problème complexe qui requiert un examen articulé et cohérent de la chaîne d'interactions qui relie l'échelle cellulaire, à laquelle agit le contaminant, à l'échelle écosystémique, où se situent les interactions avec les activités humaines. Cette chaîne d'interactions traverse les frontières des disciplines scientifiques (chimie, toxicologie, physiologie, écologie halieutique). En prenant la sole (Solea solea L.) comme espèce cible - espèce caractéristique des habitats côtiers pollués par l'"Erika" - le programme de recherche ECTOPHY est une première tentative de mise en place d'une approche multidisciplinaire visant à définir, valider et mettre en relation des indicateurs d'intégrité fonctionnelle caractérisant les différents niveaux biologiques. Le couplage d'observations in situ avec des expositions en milieu contrôlé a montré que des pertes de fonctionnalité évidentes et durables à l'échelle de l'individu sont masquées à l'échelle de la population. Certaines des approches (in situ ou expérimentale) et certains des indicateurs testés peuvent être proposés comme instruments utilisables dans le cadre d'évaluation d'impact de pollutions par des hydrocarbures.

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The common dentex (Dentex dentex) is a sparid fish which is considered a suitable candidate for Mediterranean aquaculture. A seven-weeks feeding trial was conducted over the summer period with common dentex, sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax). All three species were fed to visual satiety with two practical diets with varying crude protein and crude fat levels (55 % protein, 9 % lipids; 46 % protein, 17 % lipids). The initial body weights were 8.2, 11.6 and 17.3 g for common dentex, sea bass and sea bream, respectively. In all cases, specific growth rates were not significantly affected by dietary treatment, but they varied among species (sea bass 1.7-1.8 %; sea bream 2.1-2.3 %; common dentex 3.1-3.2 %). When comparisons between fish species were made, we observed that the increase in growth rates was linked to a decrease of the whole body fat content, as a consequence of a greater utilisation of dietary lipids as energy substrates. Furthermore, in common dentex, the 17 % lipid diet was able to improve protein retention, but this diet effect was less significant in sea bream and sea bass. In contrast to sea bream, the 17 % lipid diet did not up-regulate plasma GH levels in common dentex, which provides additional evidence for a more efficient utilisation of dietary lipids., Le dentex est un sparidé reconnu comme ayant un potentiel aquacole en Méditerranée. Une étude comparative de croissance entre le dentex, la daurade et le bar a été réalisée. Les trois espèces (poids moyen initial: 8,2; 11,6 et 17,3 g respectivement pour le dentex, le bar et la daurade) ont été nourries à satiété avec deux régimes expérimentaux (55 % de protéines brutes avec 9 % de lipides ou 46 % de protéines brutes avec 17 % de lipides). Chez chacune des espèces, le taux de croissance spécifique (TCS) n'a pas varié en fonction du régime alimentaire. En revanche, une différence significative interspécifique a été observée (bar 1,7¿1,8 %; daurade 2,1¿2,3 %; dentex 3,1¿3,2 %) avec également une différence significative dans le dépôt lipidique corporel, reflétant des différences dans l'utilisation des apports énergétiques d'origine lipidique. L'effet de rétention de protéines par des lipides a été plus important chez le dentex que chez les deux autres espèces. Par ailleurs, contrairement à ce qui est observé chez la daurade, le régime riche en lipides n'induit pas une régulation de la sécrétion de l'hormone de croissance chez le dentex, indiquant aussi une meilleure utilisation des lipides alimentaires.

The regulation of the Glucocorticoid Receptor (GR) transcript was investigated in the gills of Atlantic salmon (Salmo salar) during the parr-smolt transformation. Sampling of parr and smolt fish was performed between December and July and in particular during the smoltification period occurring in spring. Quantification of GR transcripts revealed differences between the two groups in March and at the beginning of April. During these dates, the amounts of GR mRNA in parr gills were respectively three and two fold lower than those measured in smolts. In order to determine which factors are responsible for these differences, we studied the long-term effects of prolactin and Cortisol treatments on GR transcript in the gills of presmolt fish. The plasma levels of these two hormones respectively drop and rise during smoltification. Contrary to Cortisol long-term treatment which did not modify the amount of gill GR transcript, short-term treatment induced a significant decrease within 12 hours. Prolactin long-term treatment caused a significant increase of GR transcript abundance after 13 days of implant treatment. This result is unexpected with regard to those obtained in the smoltification analysis but is in agreement with previous studies performed in mammary gland revealing a positive control of PRL on GR in epithelial cells. Our data suggest that the regulation of the GR transcript during the parr-smolt transformation probably involves several hormonal factors.; La régulation de l'expression du gène codant pour le récepteur aux glucocorticoïdes (GR) dans les branchies de saumon atlantique (Salmo salar) a été étudiée durant la période de smoltification. Les prélèvements chez les poissons parrs et smolts ont été réalisés entre décembre et juillet et plus particulièrement pendant la phase de smoltification au printemps. La quantification du transcrit GR a révélé des différences significatives entre les deux groupes en mars et début avril. Durant ces périodes, les quantités d'ARNm GR dans les branchies de saumons parrs sont respectivement trois et deux fois plus faibles comparées à celles mesurées chez les saumons smolts. Dans le but de déterminer quels facteurs interviennent dans ces variations, nous avons étudié les effets à long terme de traitements à la prolactine et au Cortisol sur la quantité de transcrits GR dans les branchies de saumons presmolts. Les concentrations plasmatiques de ces deux hormones chutent et augmentent respectivement durant la période de smoltification. Contrairement au traitement à long terme du Cortisol qui n'a pas modifié la quantité d'ARNm GR, un traitement à court terme par cette même hormone induit une baisse significative des taux de transcrits GR à partir de 12 heures de traitement. D'autre part, un traitement à long terme par la prolactine provoque une augmentation significative des taux de transcrits GR à partir de 13 jours de traitement. Ce résultat, allant à rencontre de ceux obtenus dans l'analyse de la phase de smoltification, est en accord avec les résultats obtenus dans des lignées de cellules épithéliales de glandes mammaires qui démontrent un contrôle positif de la prolactine sur la quantité de récepteurs GR. Nos résultats suggèrent donc que de multiples facteurs doivent probablement intervenir dans la régulation survenant sur la quantité d'ARNm GR branchiale durant la smoltification.

Short-term storage over several days as well as cryopreservation of turbot (Scophthalmus maximus) sperm were studied. Two extenders, Ringer 200 and artificial seminal liquid (ASL2), are suggested for semen collection in order to avoid the deleterious effect of urine contamination, and for the purpose of short-term storage between 0 and 15 degrees C. Oxygen atmosphere is not suitable for turbot sperm storage. Turbot spermatozoa undergo cryopreservation with a high rate of success especially in a sucrose solution with 10% dimethyl sulfoxide (DMSO) and 10% egg yolk.

International audience; The influence of the gonads and/or of LHRH on gonadotropic function, and possibly on gonadal development, was studied in juvenile rainbow trout treated with low doses of testosterone or untreated. Whatever the treatment, all fish of both sexes remained sexually immature, although large individual variations in plasma GTH were observed in all experimental and control groups. This dispersion in the individual values of plasma GTH seemed to be the first sign of an increase in the previously low gonadotropic activity and might announce the beginning of a pubertal period several months before the onset of meiosis in males and of vitellogenesis in females. Castration did not change the plasma and pituitary GTH values, suggesting that control of the gonadotropic function did not depend mainly on sexual steroids during this period. In our experimental conditions, LHRH administration did not lead to any change in plasma or pituitary levels of GTH. Only the testosterone treatment (20 μg) had an effect, causing a higher pituitary GTH load in some fish which was not modified either by castration or by LHRH and decreased with time ; neither of these treatments changed the plasma GTH levels. Thus, the fact that the required amount of GTH was not released to initiate early onset of gametogenesis did not seem to be due to a repressive control by the gonads or to the absence of stimulation by an LHRH-like hypothalamic factor. The quantity of GTH accumulated in the pituitary gland and the dose of steroid used have been discussed.

International audience; During a 9-month period (corresponding to a sexual cycle), the adult male tench, Tinca tinca, was kept in fish farm ponds receiving heated water from a power plant. In 1974, the males were submitted to three different temperature regimes : group I : ambiant temperature ; group II : ambiant temperature + 3 °C ; group III : ambiant temperature + 6 °C. The experiment was repeated in 1975, but only using groups I and Ill. The reproductive cycle and thermal treatment were studied from a quantitative analysis of spermatogenesis, the duration of the spawning cycle and radioimmunoassay (RIA) measurement of gonadotropin (GTH) in plasma and pituitary, using a carp RIA system turned out to be sensitive enough to assay tench GTH, which was expressed in a c-GTH equivalent. Spermatogenesis in the tench was a discontinuous process, starting in the spring and finishing in the summer. It began earlier in heated water in which the spawning period was also considerably longer (3 months in group III against 1 month in group I). At the beginning of spermatogenesis, pituitary and plasma GTH was low, but rose rapidly when spermatogenesis was initiated (appearance of type B spermatogonial cysts and meiosis). The highest GTH levels in the blood were recorded during the spawning period, with important fluctuations probably due to discharges from the pituitary.

International audience; Cryopreservation trials on rainbow trout (Salmo gairdneri) sperm were carried out using two basic extenders : Mounib's medium (M) and Ménézo's medium (Me) to which were added bovine serum albumin (BSA) and tellurite egg yolk (Institut Pasteur). After 10 p. 100 of DMSO was added to these different deep-freeze diluents (DD), they were mixed with the sperm and then deep-frozen into 100 !Ll pellets on dry ice. The pellets were stored in liquid nitrogen for periods lasting from 3 days to 6 months. The intensity of sperm motility and fertilizing ability were measured before and after cryopreservation. After the sperm was diluted in Ménézo's medium, slight spermatozoon motility was noticed, which probably caused their early exhaustion and would explain the lower fertilizing ability observed after thawing. Mounib's medium gave better results, especially after 10 p. 100 of egg yolk was added. The optimal deep-freeze conditions were : 1/3 dilution, no equilibration after dilution but immediate deep-freezing at a rate of 10 to 40 °C¡min. Thawing had to be carried out rapidly in 10 sec. However, the spermatozoa were altered during the freezing-thawing process, and during insemination more frozen spermatozoa had to be used to equal the fertilization rate obtained with non-frozen sperm. However, the fertile spermatozoa gave normal embryogenesis and no abnormal development was seen up to the vesicle resorption stage. At the end of spermiation, sperm fitness for deep-freezing decreased, perhaps due to sperm senescence. Pooling the sperm of several males partially compensated for the loss of fertilizing ability seen at the end of the reproductive period.

International audience; A stereotaxic apparatus and technique for electrode placement in diencephalic nuclei of sexually immature rainbow trout of 120-140 g body weight is described. An atlas of nuclei in the diencephalon is also presented.

International audience; Juvenile rainbow trout (weighing 10 or 20 g) were treated thrice weekly for 10 weeks with salmon-gonadotropin (S-GTH), salmon pituitary extract (S-PE), S-GTH plus estradiol-17β, and estradiol-17β alone. The effects of these treatments on the oocytes were studied at ultrastructural level. Saline-injected control fish contained oocytes at previtellogenic stage of development. S-GTH (0.1 or 0.5 µg/g) induced a synthesis of endogenous yolk in the oocyte cytoplasm but failed to initiate incorporation of exogenous yolk or vitellogenin into the oocytes. S-GTH (0.1 µg/g) in combination with estradiol-17β (1 µg)g) produced similar results to those with S-GTH alone. Estradiol-17β alone failed to induce vitellogenesis. In contrast, S-PE (10 µkg/g) induced the incorporation of exogenous yolk into the oocyte indicated by an extensive pinocytotic activity at the oocyte membrane. It is suggested that gonadotropin is necessary for the induction of endogenous yolk synthesis and that some other pituitary hormone(s) is involved in the process of incorporation of exogenous yolk or vitellogenin into the oocyte.