Browsing by Subject "Teleost fish"

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    Circadian rhythms of clock gene expression in Nile tilapia (Oreochromis niloticus) central and peripheral tissues : Influence of different lighting and feeding conditions
    (Springer, 2016) Costa, Leandro; Serrano, Ignacio; Sánchez Vázquez, Francisco Javier; López Olmeda, José Fernando; Fisiología
    The present research aimed to investigate the existence of clock gene expression rhythms in tilapia, their endogenous origin, and how light and feeding cycles synchronize these rhythms. In the first experiment, two groups of fish were kept under an LD cycle and fed at two different time points: in the middle of the light (ML) or in the middle of the dark (MD) phase. In the second experiment, fish fed at ML was fasted and kept under constant lighting (LL) conditions for 1 day. In both experiments, the samples from central ( optic tectum and hypothalamus) and peripheral (liver) tissues were collected every 3 h throughout a 24 h cycle. The express10n levels of clock genes bmall a, clockl, per 1 b, cry2a, and cry5 were analyzed by quantitative PCR. All the clock genes analyzed in brain regions showed daily rhythms: clockl, bmall a, and cry2a showed the acrophase approximately at the end of the light phase (ZT 8:43-11:22 h), whereas perlb and cry5 did so between the end of the dark phase and the beginning of the light phase, respectively (ZT 21: 16-4:00 h). These rhythms persisted under constant conditions. No effect of the feeding time was observed in the brain. In the liver, however, the rhythms of clockl and cry5 were influenced by feeding, anda shift was observed in the MD fish group (ZT 3:58 h for clockl and 11 :20 h for cry5). This study provides the first insights into the molecular clock of tilapia, a very important fish species for aquaculture. It also reveals the endogenous origin of clock gene rhythms and the ability of feeding time to shift the phase in sorne clock genes in the peripheral, but not the central, oscillator.
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    Cytotoxicity and alterations at transcriptional level caused by metals on fish erythrocytes in vitro
    (Springer, 2016-03-15) Morcillo, Patricia; Romero, Diego; Meseguer, José; Cuesta Peñafiel, Alberto; Esteban Abad, María de los Ángeles; Ciencias Sociosanitarias
    The in vitro use of fish erythrocytes to test the toxicity of aquatic pollutants could be a valuable alternative to fish bioassays but has received little attention. In this study, erythrocytes from marine gilthead sea bream (Sparus aurata L.) and European sea bass (Dicentrarchus labrax L.) specimens were exposed for 24 h to Cd, Hg, Pb and As and the resulting cytotoxicity was evaluated. Exposure to metals produced a dose-dependent reduction in the viability, and mercury showed the highest toxicity followed by MeHg, Cd, As and Pb. Moreover, fish erythrocytes incubated with each one of the metals exhibited alteration in gene expression profile of metallothionein, superoxide dismutase, catalase, peroxiredoxin, glutathione reductase, heat shock proteins 70 and 90, Bcl2-associated X protein and calpain1 indicating cellular protection, stress and apoptosis death as well as oxidative stress. This study points to the benefits for evaluating the toxicological mechanisms of marine pollution using fish erythrocytes in vitro.
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    Daily rhythms of the expression of genes from the somatotropic axis : The influence on tilapia (Oreochromis niloticus) of feeding and growth hormone administration at different times
    (Elsevier, 2016) Costa, Leandro; Rosa, Priscila; Fortes Silva, Rodrigo; Sánchez Vázquez, Francisco Javier; Fisiología
    The aim of this research was to investigate the presence of daily rhythms in the somatotropic axis of tilapia fed at two times (mid-light, ML or mid-dark, MD) and the influence of the time of day of growth hormone (GH) administration on the response of this axis. Two different GH injection times were tested: ZT 3 (3 h after lights on) and ZT 15 (3 h after lights off). In both experiments, the mRNA expression levels of hypothalamic pituitary adenylate cyclase-activating polypeptide (pacap), pituitary growth hormone (gh), liver insulin-like growth factors (igf1 and igf2a), and liver and muscle growth hormone receptors (ghr1 and ghr2) and IGF receptors (igf1ra and igf2r) were evaluated by means of qPCR. Daily rhythms were observed in the liver for ghr1, ghr2 and igf2r but only in fish fed at ML, with the acrophases located in the light phase (ZT 3:30, 3:31 and 7:38 h, respectively). In the muscle, ghr1 displayed a significant rhythm in both groups and ghr2 in ML fed fish (acrophases at ZT 5:29, 7:14 and 9:23 h). The time of both GH administration and feeding influenced the response to GH injection: ML fed fish injected with GH at ZT 15 h showed a significant increase in liver igf1, igf2a and ghr2; and muscle ghr2 expression. This is the first report that describes the existence of daily rhythms in the somatotropic axis of tilapia and its time- dependent responses of GH administration. Our results should be considered when investigating the elements of the somatotropic axis in tilapia and GH administration.
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    Specific and non-overlapping functions of testosterone and 11-ketotestosterone in the regulation of professional phagocyte responses in the teleost fish gilthead seabream
    (Elsevier, 2012-09-06) Águila Martínez, Sonia; Castillo Briceño, P.; Sánchez, M.; Cabas, Isabel; García Alcázar, Alicia; Meseguer, José; Mulero Méndez, Victoriano Francisco; García Ayala, Alfonsa; Biología Celular e Histología; ; Medicina
    Sex hormones, both estrogens and androgens, have a strong impact on immunity in mammals. In fish, the role of androgens in immunity has received little attention and contradictory conclusions have been obtained. However, it is well known that sex steroids are involved in fish growth, osmoregulation and gonad remodelation. In this study, we examine the in vitro effects of testosterone and 11-ketotestosterone, the two main fish androgens, on the professional phagocytes of the teleost fish gilthead seabream (Sparus aurata L.). Although both testosterone and 11-ketotestosterone failed to modulate the respiratory burst of seabream phagocytes, testosterone but not 11-ketotestosterone was able to increase the phagocytic ability of non-activated phagocytes. Curiously, 11-ketotestosterone was more powerful than testosterone at inducing the expression of its own receptor, namely androgen receptor b (ARb), in acidophilic granulocytes (AGs), but none of them affected the basal ARb expression levels in macrophages (MØ). Furthermore, although physiological concentrations of testosterone exerted a pro-inflammatory effect on both AGs and MØs, 11-ketotestosterone showed an anti-inflammatory effect in AGs and a strong pro-inflammatory effect in MØs. Interestingly, both androgens modulated the expression of toll-like receptors in these two immune cell types, suggesting that androgens might regulate the sensitivity of phagocytes to pathogens and damage signals. Testosterone and 11-ketotestosterone have a competitive effect, at least, on the modulation of the expression of some genes. Therefore, our results show for the first time a non-overlapping role for testosterone and 11-ketotestosterone in the regulation of professional phagocyte functions in fish.