Percorrer por autor "Martos-Sitcha, J. A."
A mostrar 1 - 5 de 5
Resultados por página
Opções de ordenação
- AVT is involved in the regulation of ion transport in the intestine of the sea bream (Sparus aurata)Publication . Martos-Sitcha, J. A.; Gregorio, Silvia; Carvalho, Edison Samir Mascarelhas; Canario, Adelino V. M.; Power, Deborah; Mancera, J. M.; Martínez-Rodriguez, G.; Fuentes, J.The intestine of marine fish plays a crucial role in ion homeostasis by selective processing of ingested fluid. Although arginine vasotocin (AVT) is suggested to play a role in ion regulation in fish, its action in the intestine has not been demonstrated. Thus, the present study investigated in vitro the putative role of AVT in intestinal ion transport in the sea bream (Sparus aurata). A cDNA encoding part of an AVT receptor was isolated and phylogenetic analysis revealed it clustered with the V1a2-type receptor clade. V1a2 transcripts were expressed throughout the gastrointestinal tract, from esophagus to rectum, and were most abundant in the rectum regardless of long-term exposure to external salinities of 12, 35 or 55 p.p.t. Basolateral addition of AVT (10 6 M) to the anterior intestine and rectum of sea bream adapted to 12, 35 or 55 p.p.t. mounted in Ussing chambers produced rapid salinity and region dependent responses in short circuit current (Isc), always in the absorptive direction. In addition, AVT stimulation of absorptive Isc conformed to a dose–response curve, with significant effects achieved at 10 8 M, which corresponds to physiological values of plasma AVT for this species. The effect of AVT on intestinal Isc was insensitive to the CFTR selective inhibitor NPPB (200 lM) applied apically, but was completely abolished in the presence of apical bumetanide (200 lM). We propose a role for AVT in the regulation of ion absorption in the intestine of the sea bream mediated by an absorptive bumetanide-sensitive mechanism, likely NKCC2.
- Characterization of the peripheral thyroid system of gilthead seabream acclimated to different ambient salinitiesPublication . Ruiz-Jarabo, I.; Klaren, P. H. M.; Louro, Bruno; Martos-Sitcha, J. A.; Pinto, P. I.; Vargas-Chacoff, L.; Flik, G.; Martinez-Rodriguez, G.; Power, Deborah; Mancera, J. M.; Arjona, F. J.Thyroid hormones are involved in many developmental and physiological processes, including osmoregulation. The regulation of the thyroid system by environmental salinity in the euryhaline gilthead seabream (Sparus aurata) is still poorly characterized. To this end seabreams were exposed to four different environmental salinities (5, 15, 40 and 55 ppt) for 14 days, and plasma free thyroid hormones (fT3, ff4), outer ring deiodination and Na+/K+ -ATPase activities in gills and kidney, as well as other osmoregulatory and metabolic parameters were measured. Low salinity conditions (5 ppt) elicited a significant increase in fT3 (29%) and ff4 (184%) plasma concentrations compared to control animals (acclimated to 40 ppt, natural salinity conditions in the Bay of Cadiz, Spain), while the amount of pituitary thyroid stimulating hormone subunit 13 (tshb) transcript abundance remained unchanged. In addition, plasma fT4 levels were positively correlated to renal and branchial deiodinase type 2 (dio2) mRNA expression. Gill and kidney T4-outer ring deiodination activities correlated positively with dio2 mRNA expression and the highest values were observed in fish acclimated to low salinities (5 and 15 ppt). The high salinity (55 ppt) exposure caused a significant increase in tshb expression (65%), but deiodinase gene expression (diol and dio2) and activity did not change and were similar to controls (40 ppt). In conclusion, acclimation to different salinities led to changes in the peripheral regulation of thyroid hormone metabolism in seabream. Therefore, thyroid hormones are involved in the regulation of ion transport and osmoregulatory physiology in this species. The conclusions derived from this study may also allow aquaculturists to modulate thyroid metabolism in seabream by adjusting culture salinity. (C) 2016 Elsevier Inc. All rights reserved.
- Effect of bile salts on intestinal epithelial function in gilthead seabream (Sparus aurata)Publication . Fuentes, J.; Gregorio, Silvia; F. Fonseca; Robles-Arozarena, R.; Martos-Sitcha, J. A.; Moyano, F. J.In the context of modern aquaculture, the effort to reduce the reliance on fishmeal/marine ingredients in fish diets has led to the exploration of plant-based protein sources as potential substitutes, a dietary shift that disrupts the bile acid profile in fish. Therefore, bile salts are being sought as additives. However, artificially increased intestinal levels of bile acids may significantly impact mucosal function. Therefore, here, we explored the regulatory role in the intestine of gilthead sea bream (Sparus aurata) of (i) chenodeoxycholic acid (CDC), (ii) a mixture formed by two bile acids, 3% cholic acid and 97% deoxycholic acid (MIX), and (iii) a conjugated bile salt sodium taurocholate (TC) in Ussing chambers with the epithelial voltage clamp technique. We tested the bile salts in a 50-500 mu g/ml concentration range, and all of them promoted ion absorption. Yet, clear concentration-dependent and more pronounced effects on the ion transport were observed in the posterior intestine. On the other hand, bile salts had no or minor effects on tissue resistance. However, there are indications that the MIX could have adverse effects at high concentrations (500 mu g/ml), promoting a threefold increase in tissue permeability measured using FITC-dextran (4 kD) regardless of the intestinal region, thus suggesting an alteration in intestinal permeability at high bile salt concentrations. The findings from our study emphasize the importance of considering intestinal function when contemplating the possible use of a particular bile salt as a dietary supplement. It appears that bile salts, whether acting individually or in combination, play a pivotal role in orchestrating nutrient absorption by influencing the function of epithelial ion transport. However further research is needed to fully grasp the region-dependent nuances of bile salt effects on ion transport and the ultimate consequences for nutrient absorption in the context of fish aquaculture.
- Health status in gilthead seabream (Sparus aurata) juveniles fed diets devoid of fishmeal and supplemented with Phaeodactylum tricornutumPublication . Reis, B.; Ramos-Pinto, L.; Martos-Sitcha, J. A.; Machado, M.; Azeredo, R.; Fernandez-Boo, S.; Engrola, S.; Unamunzaga, C.; Calduch-Giner, J.; Conceicao, L. E. C.; Silva, T.; Dias, J.; Costas, B.; Perez-Sanchez, J.To enhance fish general health, feeds can be supplemented with health-promoting additives, reducing the need to use chemotherapeutics. Incorporation of marine algae biomasses in aquafeeds has been shown to improve fish immune status by enhancing innate immune response. This study evaluated the effects of Phaeodactylum tricornutum incorporation in feed by two different processes, either as freeze-dried biomass or broken cell wall biomass, on fish health status and performance. Triplicate groups of gilthead seabream juveniles (13.3 +/- 0.3 g) were either fed a control diet (CTRL) with an extreme (i.e., 0% fishmeal), nutritionally balanced, formulation, or two experimental diets formulated as the CTRL with 1% inclusion of the microalga P. tricornutum at the expense of wheat meal: BC diet contains P. tricornutum broken cells and WC diet microalgae whole cells. After 2 and 12 weeks of feeding, blood was collected for hematological procedures, whereas plasma and mucus were sampled for immune parameters. Head-kidney, liver, and white skeletal muscle were also collected for gene expression measurements. No major differences were observed in hematological nor plasma humoral parameters after 12 weeks irrespective of dietary treatment. Arrays of 29-31 genes were analyzed in the different tissues, revealing an early dietary effect (2 weeks) in a tissue-specific pattern. In the liver, the major effect was found in the GH/IGF axis and in muscle there was a late downregulation of myostatin (mstn) gene, mainly due to WC diet, even though all fish had similar growth performance. Regarding the head-kidney, BC diet led to alpha-2-macroglobulin (a2m) gene upregulation. Also, the same treatment showed increased mucus alternative complement pathway and bactericidal activity at 2 and 12 weeks, respectively. Hence, it seems that BC diet has a potential stimulatory effect that might be relevant as a prophylactic measure before a predictable stressful event.
- Physiological responses of Senegalese sole (Solea senegalensis Kaup, 1858) after stress challenge: Effects on non-specific immune parameters, plasma free amino acids and energy metabolismPublication . Costas, B.; Conceição, L. E. C.; Aragão, C.; Martos-Sitcha, J. A.; Ruiz-Jarabo, I.; Mancera, J. M.; Afonso, A.Physiological responses after an acute handling stress and their subsequent effects on innate immune parameters, plasma free amino acids (AA) and liver energy substrates were assessed in Senegalese sole (Solea senegalensis). Eight groups of six specimens (136.1± 58.4 g wet weight) were maintained undisturbed, while other eight groups of six specimens were used for acute stress challenge (air exposed during 3 min). A group of six specimens was sampled for blood and head-kidney collection immediately after air exposure (time 0), while the remaining groups were sampled at 5 and 30 min, 1, 2, 4, 6 and 24 h. Undisturbed fish were sampled at the same times and used as control. Fish were fasted for 24 h prior to air exposure and sampling. Plasma cortisol, glucose, lactate and osmolality levels increased immediately after stress peaking at 1 h in air exposed fish. Changes in plasma free AA were also observed at 1 and 24 h after stress. In liver, glycogen levels significantly decreased at 30 min and 1 h, while triglycerides values significantly increased at 1, 2 and 4 h in air exposedfish. In addition, total AA levels in liver augmented significantly at 2 h holding high until 24 h in air exposed specimens. The respiratory burst of head-kidney leucocytes from air exposed fish was significantly higher than that from control groups at 2 and 6 h after air exposure. On the other hand, plasma lysozyme activity significantly decreased at 4 h after acute stress in air exposed fish, while plasma alternative complement pathway followed an inverse linear relationship with respect to cortisol showing the lowest value at 1 h after air exposure. The present study suggests that Senegalese sole presents a stress response comparable to that observed in other teleosts. While some indispensable AA may be used for the synthesis of compounds related to the stress response or fatty acid transport, dispensable AA were probably mainly employed either as energy sources or in gluconeogenesis. Moreover, results from non-specific immune parameters assessed suggest that cortisol may act as regulator of the innate immune system.