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Presence and activity of compounds with GnRH-like activity in the ovary of seabream Sparus aurata.
No full textThe binding and activity of gonadotropin-releasing hormone (GnRH) were characterized in the mature gilthead seabream (Sparus aurata) ovary by use of an analogue of salmon GnRH([D-Arg6,Trp7,Leu8,Pro9-N(Et)]GnRH, sGnRH-A) as labeled ligand. The binding of 125I-sGnRH-A to the seabream ovarian membrane preparation was saturable, displaceable, reversible, and dependent on time, temperature and tissue concentration. Addition of unlabeled s-GnRH-A displaced the radio-ligand in a dose-related manner, indicating the presence of one class of high-affinity binding sites with an equilibrium dissociation constant of 45.5 +/- 6.2 nM. Addition of other GnRH peptides, including salmon GnRH ([Trp7,Leu8]GnRH) and chicken GnRH-II ([His5,Trp7,Tyr8]GnRH), also displaced 125I-sGnRH-A; all these peptides bound with lower affinities than sGnRH-A to the seabream ovarian binding site. In this study, we also demonstrated the presence of compounds with GnRH-like activity in the ovary of seabream. Seabream ovarian extract stimulated pituitary gonadotropin release from the goldfish pituitary and displaced 125I-sGnRH-A binding in the seabream ovary. Furthermore, addition of sGnRH-A to cultured seabream oocytes directly stimulated reinitiation of oocyte meiosis, as indicated by germinal vesicle breakdown. Overall, the present study characterizes GnRH-binding sites in the seabream ovary and supports the hypothesis that GnRH or compounds with GnRH-like activity play an autocrine/paracrine role in the regulation of ovarian function in the seabream ovary
Acetyl salmon endorphin-like and interrenal stress response in male gilthead sea bream, Sparus aurata
No full textThe present study investigates the role of melanotrope proopiomelanocortinderived peptide in the interrenal stress response to different stressors in male gilthead sea bream, Sparus aur ata. Plasma cortisol and acetyl salmon endorphin (acetyl s-EP), as well as pituitary acetyl s-EP contents, were measured during two stress paradigms: (a) long-term (l-month) confinement and crowding, and (b) short-term (60-min) confinement, crowding, and manipulation. In addition, naltrexone, a highly specific opioid receptor antagonist, was employed in some experimental groups to evaluate the adaptability of the opioid response to interrenal stress. In the long-term (I-month) confinement and crowding, higher plasma cortisol levels and acetyl s-EP concentrations than in the control group were found. However, although plasma cortisol levels significantly increased in both types of stress paradigm, a significant rise in plasma acetyl s-EP was observed only in the case of confinement plus crowding. These data seem to suggest a direct correlation of acetyl s-EP plasma levels exclusively in cases of specific stress, and support previous observations about the different nature of the pituitary-interrenal stress response in salmonids and in mammals. The results obtained in the short-term (60-min) experiments demonstrate the double activation of both the opioid and corticotrope systems when manipulation plus crowding was applied
Growth hormone and insulin-like growth factor-I in inducing vitellogenin synthesis by frog hepatocytes
Full text linkDifferential splicing of three gonadotropin-releasing hormone transcripts in the ovary of seabream (Sparus aurata).
Full text linkPrevious studies demonstrated the presence of high-affinity GnRH binding sites and compounds with GnRH-like activity in the ovary of seabream, Sparus aurata, providing evidence for the role of GnRH as a paracrine/autocrine regulator of ovarian function in this species. In the present study, the expression of three forms of GnRH (salmon, chicken-II, and seabream) genes in this marine teleost species was demonstrated for the first time. Moreover, there is evidence for differential splicing and intronic expression of cGnRH-II and sbGnRH. Treatment of seabream follicle-enclosed oocytes with salmon GnRH stimulated reinitiation of oocyte meiosis, whereas chicken GnRH-II treatment was without effect. Novel information was also provided about organization of cGnRH-II and seabream GnRH transcripts, confirming that GnRH gene organization is maintained through evolution, despite changes in the size and sequence of exons and intron
Cloning of sole proopiomelanocortin (POMC) cDNA and the effects of stocking density on POMC mRNA and growth rate in sole, Solea solea
No full textProopiomelanocortin (POMC) is an important gene implicated in different functions, such as the stress response of the hypothalamus–
pituitary–adrenal axis. The aim of the present study was to determine whether farming conditions, such as stocking density, can
be considered a powerful stressor influencing in turn the growth rate in juvenile fish. Thus, POMC cDNA expression was investigated
during adaptation to farming conditions in sole (Solea solea), as a model for studying the effects of rearing densities on stress response;
different stocking densities (50, 100, and 250 animals/m2) were applied and, after 7 and 21 days, the fishes were examined for body weight
and plasma cortisol levels as indicators of stress. In addition, proopiomelanocortin was cloned and sequenced from the brain of sole,
allowing semi-quantitative RT-PCR to be performed to evaluate POMC mRNA expression in brain tissue. There was a significant
increase in cortisol levels in fish reared at high stocking densities of 250/m2 compared to fish reared at control densities of 100 and
50/m2, in both experimental times, i.e., 7 and 21 days. The high stocking densities were also found to decrease the specific growth rate
of fish. Moreover, it was demonstrated that the highest stocking density induced a significant decrease in sole POMC mRNA expression.
It is concluded that POMC and cortisol are both involved in the stress response due to high rearing densities, during which cortisol may
serve as a negative regulator of POMC
Partial cloning of CB1 cDNA and its involvement in the modulation of stress responses in the sole, Solea solea
No full textEndogenous cannabinoids, through the CB1 receptor, are involved in the control of several functions including stress responses. The aim of this study was to investigate the presence of cannabinoid receptor CB1 in the sole ovary by partial cloning of brain CB1 cDNA; in a stress paradigm of disturbance by handling, which consisted in catching, netting and hand-sorting, changes of CB1 mRNA were related with those of proopiomelanocortin (POMC) mRNA; the trend and timing of stress responses and adaptation were monitored by measuring plasma cortisol levels. We characterized two forms of CB1-like receptor, termed CB1A and CB1B. The two sole CB1 (both 799 bp) share 76% identity in their cDNAs, and the deduced amino acid sequences are 80% identical. The handling stress induced a sustained increase in plasma cortisol levels 1 h after the
handling began and decreased to low levels 12 h after initiation of handling, showing the same trend of ovarian POMC mRNA expression. In addition, while CB1A mRNA did not show any significant changes during handling stress, significantly lower levels of CB1B mRNA were found in stressed fish 1 h after the beginning of handling, with CB1 expression increased 24 h after stress induction, both in the ovary and brain. It can be
concluded that endocannabinoid system is involved in the modulation of adaptive responses to environmental conditions
Proopiomelanocortin gene expression in the ovary of the frog, Rana esculenta.
Full text linkThe presence of proopionmelanocortin (POMC)-like mRNA has been demonstrated
in a variety of extrapituitary tissues including hypothalamus,1 placenta,2 ovary,2 and
testis.3 In amphibians, the POMC gene is actively expressed in the pituitary, both in
melanotrope cells of the pars intermedia and in corticotrope cells of the pars distalis.
4–6 POMC gene expression in peripheral organs has also been investigated in
Rana esculenta,7 indicating that POMC is actually synthetized in the ovary. Previous
studies have shown that POMC-derived peptides are involved in local control of
ovarian function and display seasonal changes.8,9 The aim of the present work was
to develop a competitive reverse transcriptase polymerase chain reaction (RT-PCR)
method using a synthetic, deletion mutant of POMC cRNA as an internal standard
in order to quantify the amount of POMC mRNA in the ovary of Rana esculenta
PCR-ELISA detection of estrogen receptor mRNA expression and plasma vitellogenin induction in juvenile sole (Solea solea) exposed to waterborne 4-nonylphenol
No full textIn this study, the effect of 4-nonylphenol (4NP) on reproductive axis of sole (Solea solea) has been investigated by using selected biomarkers of estrogenic effects: vitellogenin (VTG) and estrogen receptor beta (ERb) mRNA. Furthermore, an enzyme linked immunosorbent assay (ELISA) detection system of reverse
transcriptase-polymerase chain reaction (RT-PCR) products for the analysis of sole ERb mRNA expression was developed and validated. The proposed method allows large-scale analyses of different mRNAs in fast and not expensive way. Our results have demonstrated that the PCR–ELISA method developed shows
high sensitivity, good reproducibility and also the potential for semi-quantitative analysis of hepatic ERb mRNAs. Both plasma VTG level and ERb mRNA expression were increased in tested animals following a short exposure to environmental relevant concentrations (10-6 M) of 4NP, confirming the functional role
of ERb in the regulation of xenoestrogens-induced production of VTG. The methodology provided in the present study together with the preliminary results on the hepatic expression of ERb may be useful in environmental xenoestrogens monitoring studies, using flatfish as ‘‘sentinel’’ species
Effect of photo-thermal and feeding regimes in the spawning induction of the sole, Solea vulgaris (Quensel, 1806)
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