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Delgadin T.H.,Laboratorio Of Neuroendocrinologia Del Crecimiento Y La Reproduccion | Perez Sirkin D.I.,Laboratorio Of Neuroendocrinologia Del Crecimiento Y La Reproduccion | Perez Sirkin D.I.,CONICET | Karp P.J.,Laboratorio Of Neuroendocrinologia Del Crecimiento Y La Reproduccion | And 3 more authors.
Belgian Journal of Zoology | Year: 2014

Environmental factors and social interactions are known to affect somatic growth and reproduction in teleost fish. It has been described for Cichlasoma dimerus that only one pair is formed under a wide range of laboratory conditions. However, this was not observed in tanks composed of three males and three females, where multiple pair formation occurred. Thus, our objective was to evaluate somatic growth and reproductive performance in C. dimerus under this particular condition, in which more than one pair is expected to be formed. A clear sexual growth dimorphism, with males growing faster than females, and multiple pair formation, sometimes simultaneously, were observed. Both features were absent in previous studies with other aquaria structures. Additionally, there was a significant association between reproductive events and body size, where the bigger the fish, both male and female, the higher the number of reproductive events. Despite the sexual growth dimorphism, no differences were observed between males and females in IGF-I and GHR2 mRNA levels. The results obtained for this social species show a high inter-individual variability in the aquaria in regard to reproductive success and growth. This may have implications on experimental design, where a low level of heterogeneity between fish is desirable. If this variability is not taken into account, possible treatment effects may not be detected. © 2014, Societe Royale Zoologique de Belgique. All rights reserved. Source


Delgadin T.H.,Laboratorio Of Neuroendocrinologia Del Crecimiento Y La Reproduccion | Delgadin T.H.,CONICET | Perez Sirkin D.I.,Laboratorio Of Neuroendocrinologia Del Crecimiento Y La Reproduccion | Perez Sirkin D.I.,CONICET | And 5 more authors.
Fish Physiology and Biochemistry | Year: 2014

Cichlasoma dimerus is a social cichlid fish capable of growing at high rates under laboratory conditions, but knowledge on somatic growth regulation is still unclear. Growth hormone (GH)/insulin-like growth factor I (IGF-I) axis is the key regulator of somatic growth in vertebrates. Two types of growth hormone receptors have been described in teleost fish, named GH receptor type 1 (GHR1) and type 2 (GHR2). In addition, isoforms of these receptors lacking part of the intracellular region have been described. The aim of this study was to evaluate the somatic growth, liver histology and changes in the GH/IGF-I axis after 4 weeks of food deprivation in C. dimerus. Four-week fasted fish showed reductions in specific growth rates in body weight (p < 0.001) and standard length (p < 0.001). Additionally, the hepatosomatic index (p < 0.001) and hepatocyte area (p < 0.001) decreased in fasted fish, while no changes in glucose levels were detected in plasma. The starvation protocol failed to induce changes in GH mRNA levels in the pituitary and IGF-I mRNA levels in liver. In contrast, IGF-I mRNA levels in muscle decreased in fasted fish (p = 0.002). On the other hand, GHR2 (detected with primer sets designed over the extracellular and intracellular region) was upregulated by starvation both in liver and muscle (p < 0.05), while GHR1 remained unchanged. These results show that a fasting period reduced somatic growth both in length and body weight concomitantly with alterations on liver and muscle GHR2 and muscle IGF-I mRNA expression. © 2014, Springer Science+Business Media Dordrecht. Source


Di Yorio M.P.,Laboratorio Of Neuroendocrinologia Del Crecimiento Y La Reproduccion | Di Yorio M.P.,CONICET | Delgadin T.H.,Laboratorio Of Neuroendocrinologia Del Crecimiento Y La Reproduccion | Delgadin T.H.,CONICET | And 4 more authors.
Fish Physiology and Biochemistry | Year: 2015

Neuropeptide Y (NPY) is considered the most potent orexigenic peptide, increasing before meal time and during fasting. In teleost, most studies on NPY action upon growth hormone (GH) and luteinizing hormone (LH) were conducted in females or group of animals without sex discrimination. The aim of this study was to evaluate whether NPY modulates the expression and release of GH and gonadotropins in both sexes of Cichlasoma dimerus. By double-label immunofluorescence, we first determined the association between NPY fibers and pituitary cells. In addition, we performed in vitro studies to evaluate the effect of NPY on GH and gonadotropins expression by real-time PCR, and release by Western blot, in males and females separately. Contacts between NPY fibers and GH and follicle-stimulating hormone (FSH)-producing cells were detected, indicating possible functional relationships. We observed an increase in GH release in the culture medium at 2 nM for males (p = 0.043) and 20 nM for females (p = 0.028). Pituitary FSH release was stimulated at 20 nM (p = 0.026) and 200 nM (p = 0.033) for males and females, respectively. Finally, NPY only increased β-LH mRNA expression at 20 nM in females (p = 0.028) and its release at 2 nM (p = 0.049) and 200 nM for males (p = 0.005) and 200 nM for females (p = 0.018). In conclusion, NPY acts as a GH-, LH- and FSH-releasing factor, in a dose- and sex-dependent way. © 2015, Springer Science+Business Media Dordrecht. Source

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