Percorrer por autor "Machado, Marina"
A mostrar 1 - 7 de 7
Resultados por página
Opções de ordenação
- Dietary methionine supplementation improves the European seabass (Dicentrarchus labrax) immune status following long-term feeding on fishmeal-free dietsPublication . Machado, Marina; Engrola, Sofia; Colen, R.; Conceicao, Luis E. C.; Dias, Jorge; Costas, BenjaminMethionine is a limiting amino acid (AA) in fish diets, particularly in those containing high levels of plant protein (PP), and is key in the immune system. Accordingly, outcome on the fish immune mechanisms of methionine-deficient and methionine-supplemented diets within the context of 0 % fishmeal formulation, after a short and prolonged feeding period, was studied in European seabass (Dicentrarchus labrax). For this, seabass juveniles were fed a (i) fishmeal-free diet, meeting AA requirements, but deficient in methionine (MET0·65); (ii) as control, the MET0·65 supplemented with L-methionine at 0·22 % of feed weight (CTRL); (iii) two diets, identical to MET0·65 but supplemented at 0·63 and 0·88 % of feed weight of L-methionine (MET1·25 and MET1·5, respectively); and (iv) a fishmeal-based diet (FM), as positive control. After 2 and 12 weeks of feeding, blood and plasma were sampled for leucocyte counting and humoral parameter assays and head-kidney collected for gene expression. After 2 weeks of feeding, a fishmeal-free diet supplemented with methionine led to changes in the expression of methionine- and leucocyte-related genes. A methionine immune-enhancer role was more evident after 12 weeks with an increased neutrophil percentage and a decreased expression of apoptotic genes, possibly indicating an enhancement of fish immunity by methionine dietary supplementation. Furthermore, even though CTRL and FM present similar methionine content, CTRL presented a reduced expression of several immune-related genes indicating that in a practical PP-based diet scenario, the requirement level of methionine for an optimal immune status could be higher.
- Dietary tryptophan intervention counteracts stress-induced transcriptional changes in a teleost fish HPI axis during inflammationPublication . Peixoto, Diogo; Carvalho, Inês; Machado, Marina; Aragão, Cláudia; Costas, Benjamín; Azeredo, RitaImmune nutrition is currently used to enhance fish health by incorporating functional ingredients into aquafeeds. This study aimed to investigate the connections between tryptophan nutrition and the network that regulates the communication pathways between neuroendocrine and immune systems in European seabass (Dicentrarchus labrax). When tryptophan was supplemented in the diet of unstressed fish, it induced changes in the hypothalamic-pituitary-interrenal axis response to stress. Tryptophan-mediated effects were observed in the expression of anti-inflammatory cytokines and glucocorticoid receptors. Tryptophan supplementation decreased pro-opiomelanocortin b-like levels, that are related with adrenocorticotropic hormone and cortisol secretion. When stressed fish fed a tryptophan-supplemented diet were subjected to an inflammatory stimulus, plasma cortisol levels decreased and the expression of genes involved in the neuroendocrine response was altered. Modulatory effects of tryptophan dietary intervention on molecular patterns seem to be mediated by altered patterns in serotonergic activity.
- Dietary tryptophan intervention counteracts stress-induced transcriptional changes in a teleost fish HPI axis during inflammationPublication . Peixoto, Diogo; Carvalho, Inês; Machado, Marina; Aragão, Cláudia; Costas, Benjamín; Azeredo, RitaImmune nutrition is currently used to enhance fish health by incorporating functional ingredients into aquafeeds. This study aimed to investigate the connections between tryptophan nutrition and the network that regulates the communication pathways between neuroendocrine and immune systems in European seabass (Dicentrarchus labrax). When tryptophan was supplemented in the diet of unstressed fish, it induced changes in the hypothalamic-pituitary-interrenal axis response to stress. Tryptophan-mediated effects were observed in the expression of anti-inflammatory cytokines and glucocorticoid receptors. Tryptophan supplementation decreased pro-opiomelanocortin b-like levels, that are related with adrenocorticotropic hormone and cortisol secretion. When stressed fish fed a tryptophan-supplemented diet were subjected to an inflammatory stimulus, plasma cortisol levels decreased and the expression of genes involved in the neuroendocrine response was altered. Modulatory effects of tryptophan dietary intervention on molecular patterns seem to be mediated by altered patterns in serotonergic activity.
- Dietary tryptophan plays a role as an anti-inflammatory agent in european seabass (dicentrarchus labrax) juveniles during Chronic InflammationPublication . Azeredo, Rita; Peixoto, Diogo; Paulo Santos; Duarte, Inês; Ricardo, Ana; Machado, Marina; Costas, Benjamín; Aragão, CláudiaWhere teleost fish are concerned, the effects of a dietary tryptophan surplus are mostly immunosuppressive, making it a potential dietary anti-inflammatory strategy. The goal of the present work was to evaluate the effects of tryptophan dietary supplementation on immune and neuroendocrine responses of the European seabass, Dicentrarchus labrax, undergoing chronic inflammation. Juvenile European seabass were intraperitoneally injected with an inflammatory agent (inflamed group) or a saline solution (control group). Within each group, fish were fed a control and a control-based diet supplemented with tryptophan for 4 weeks. Different tissues were sampled every week for the assessment of immune-related parameters. When tryptophan was provided to fish undergoing inflammation, the gene expression of a macrophage marker increased sooner and remained high until the end of the experiment. The same fish showed a concurrent increase in peripheral monocyte counts. After one week, molecular patterns of anti-inflammatory processes seemed to be favoured by tryptophan. Altogether, results show that a short administration period seems to be critical where tryptophan supplementation is concerned since at later inflammatory stages—and longer feeding periods—fish fed this diet displayed a molecular profile similar to that of fish fed a control diet.
- Microalgal biomasses have potential as ingredients in microdiets for Senegalese sole (Solea senegalensis) post-larvaePublication . Peixoto, Diogo; Pinto, Wilson; Gonçalves, Ana Teresa; Machado, Marina; Reis, Bruno; Silva, Joana; Navalho, Joao; Dias, Jorge; Conceicao, Luis; Costas, BenjaminSenegalese sole (Solea senegalensis) production presents several nutritional challenges, making this species a good candidate to study the dietary potential of bioactive compounds. Since proper nutrition plays a fundamental role in fish biology, it is necessary to further investigate species-specific and well-balanced diets in order to improve Senegalese sole juvenile farming. Algae have antioxidant properties, high-quality dietary protein, and are a source of bioactive compounds. This study evaluates the effects of dietary microalgal inclusion in both health status and growth performance of Senegalese sole post-larvae. Individuals 41 days after hatching (DAH) were randomly distributed among 12 tanks and four experimental diets were randomly distributed by triplicate groups. A basal diet served as CTRL and the experimental diets were formulated to include 3% of each of the algal biomass (CHLO, Chlorella sp. from heterotrophic production; PHAEO, Phaeodactylum sp.; and NANNO, Nannochloropsis sp.). At 50 DAH, 20 post-larvae/tank were collected and homogenized for analysis of immune and oxidative status, and at 61 DAH the total length, dry weight, and survival were assessed. No changes were observed in survival and total length of individuals, post-larvae fed NANNO, and CHLO dietary treatments increased dry weight at 61 DAH compared with those fed CTRL. While post-larvae immune status was apparently not altered by dietary treatments at 50 DAH, the total glutathione content decreased in fish fed PHAEO and CHLO dietary treatments compared to control diet. The observed results on improvement of growth performance without adverse effects on the immune status and decrease of endogenous total glutathione point to the fact that Nannochloropsis sp., Phaeodactylum sp., and Chlorella sp. could work as potential candidates for inclusion in microdiets for Senegalese sole.
- Tryptophan modulatory role in European Seabass (Dicentrarchus labrax) immune response to acute inflammation under stressful conditionsPublication . Machado, Marina; Peixoto, Diogo; Santos, Paulo; Ricardo, Ana; Duarte, Inês; Carvalho, Inês; Raquel Cêa de Aragão Teixeira, Cláudia; Azeredo, Rita; Costas, BenjamínThe present work aimed to study the role of dietary tryptophan supplementation in modulating the European seabass (Dicentrarchus labrax) immune condition during stressful rearing conditions (i.e., 15 days exposure to high density), as well as the immune response to acute inflammation after intraperitoneal injection of a bacterial pathogen. Stress alone did not compromise seabass health indicators. In contrast, a clear peripheral and local inflammatory response was observed in response to the inoculated bacteria. Moreover, exposure to a high stocking density seemed to exacerbate the inflammatory response at early sampling points, compared to fish stocked at a lower density. In contrast, stressed fish presented some immune-suppressing effects on the T-cell surface glycoprotein receptor expressions at a late sampling point following inflammation. Regarding the effects of dietary tryptophan, no changes were observed on seabass immune indicators prior to inflammation, while a small number of immunosuppressive effects were observed in response to inflammation, supporting tryptophan’s role in the promotion of immune-tolerance signals during inflammation. Nonetheless, tryptophan dietary supplementation improved the inflammatory response against a bacterial pathogen during stressful conditions, supported by a reduction of plasma cortisol levels, an up-regulation of several immune-related genes at 48 h, and an inversion of the previously observed, stress-induced T-cell suppression. Finally, the involvement of tryptophan catabolism in macrophages was confirmed by the up-regulation of genes involved in the kynurenine pathway. The present study brings new insights regarding the immune modulatory role of tryptophan during stressful conditions in fish, thus allowing for the development of novel prophylactic protocols during vaccination by intraperitoneal injection in the European seabass.
- Two probiotic candidates of the genus psychrobacter modulate the immune response and disease resistance after experimental infection in turbot (Scophthalmus maximus, Linnaeus 1758)Publication . Wuertz, Sven; Beça, Filipa; Kreuz, Eva; Wanka, Konrad M.; Azeredo, Rita; Machado, Marina; Costas, BenjaminProbiotic bacteria are a recognized alternative to classical methods of disease prophylaxis and therapy. We tested the effects of their application on the immune reaction in juvenile turbot. To prevent digestion of the probiotics, rectal administration was applied to maximise colonization, by-passing digestion in the stomach. The application of Psychrobacter nivimaris and Psychrobacter faecalis showed beneficial effects on the inflammatory response and disease resistance after infection with the common pathogen Tenacibaculum maritimum. Treatment with P. nivimaris and P. faecalis resulted in 0% and 8% mortalities post-infection, while in the treatment control, an elevated mortality of 20% was observed. In the challenge controls (no infection), no mortalities were observed during the entire experimental period. After an experimental infection, mRNA expression of selected immune markers (mhc II alpha, il-1 beta, tcr, tgf beta and tnf alpha) were determined by RT-QPCR at 0, 1 and 5 days post-infection (dpi). At 0 dpi, gene expression was comparable between the treatments and the treatment control, suggesting that probiotics did not act via immune stimulation of the host. At 1 dpi, all genes were up-regulated in the treatment control but not in the probiotic groups, indicating that the infection in probiotic-treated fish developed at a less severe level. At 5 dpi, mRNA expression returned to baseline levels. As a conclusion, the native probiotic candidates P. nivimaris and P. faecalis improved survival, whereas, in the control, mortality increased and expression of the immune markers was up-regulated post infection. This highlights a potential application of P. nivimaris and P. faecalis in disease prophylaxis, but further research is needed.