Browsing by Author "Afonso, A."
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- Effects of dietary amino acids and repeated handling on stress response and brain monoaminergic neurotransmitters in Senegalese sole (Solea senegalensis) juvenilesPublication . Costas, B.; Aragão, C.; Soengas, J. L.; Míguez, J. M.; Rema, P.; Dias, J.; Afonso, A.; Conceição, L. E. C.The present study aimed to assess the effects of increased availability of dietary amino acids (AA) on brain monoamine neurotransmitters and the metabolic processes resulting from stressful situations in fish. Senegalese sole (Solea senegalensis) juveniles (24.2 ± 0.4 g wet mass) were weekly subjected to an acute handling stressor (HDLG) or remained undisturbed (CTL). Additionally, both treatments were fed a control or a high protein (HP) diet (CTL, CTL HP, HDLG and HDLG HP). The HP diet slightly increased the levels of digestible indispensable AA, together with tyrosine and cysteine. Repeated handling induced a stress response after 14 and 28 days in fish held at both HDLG and HDLG HP treatments. While dietary treatment and handling stress activated the serotonergic system at 14 days, these effects were not observed after 28 days. In addition, the HP diet minimized the decrease in plasma indispensable AA due to repeated handling stress after 28 days. It was concluded that HP diet decreased post-stress plasma glucose and lactate levels in HDLG HP specimens only at 14 days of treatment. Moreover, dietary treatment was also effective in stimulating DA synthesis and release, thus dietary phenylalanine supplementation can increase DA biosynthesis in fish.
- Interactive effects of a high-quality protein diet and high stocking density on the stress response and some innate immune parameters of Senegalese sole Solea senegalensisPublication . Costas, B.; Aragão, C.; Dias, J.; Afonso, A.; Conceição, L. E. C.Amino acids (AA) regulate key metabolic pathways, including some immune responses. Therefore, this study aimed to assess whether an increased availability of dietary AA can mitigate the expected increase in plasma cortisol and metabolites levels due to high stocking density and its subsequent immunosuppression. Senegalese sole (Solea senegalensis) were maintained at low stocking density (LSD; 3.5 kg m−2) or high stocking density (HSD; 12 kg m−2) for 18 days. Additionally, both treatments were fed a control or a high protein (HP) diet (LSD, LSD HP, HSD and HSD HP). The HP diet slightly increased the levels of digestible indispensable AA, together with tyrosine and cysteine. HSD was effective in inducing a chronic stress response after 18 days of treatment since fish held at HSD presented higher plasma cortisol, glucose and lactate levels. Moreover, this increase in stress indicators translated in a decrease in plasma lysozyme, alternative complement pathway (ACP) and peroxidase activities, suggesting some degree of immunosuppression. Interestingly, while plasma glucose and lactate levels in HSD HP specimens decreased to similar values than LSD fish, plasma lysozyme, ACP and peroxidase activities increased, with even higher values than LSD groups for ACP activity. It is suggested that the HP diet may be used as functional feed since it may represent a metabolic advantage during stressful events and may counteract immunosuppression in sole.
- 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.
- Preliminary results from project MAST/AM-advanced tracking and telemetry methodologies to study marine animalsPublication . Oliveira, P.; Silvestre, C.; Morgado, M.; Erzini, Karim; Bentes, L.; Afonso, A.; Hazin, Fábio H. V.; Block, B.This paper proposes advanced methodologies for the study of tagged marine animals, resorting to telemetry techniques. The robotic tools to be developed and operated will be able to track the acoustic signals emitted by the animals, based on range and depth data acquired with ultra-short baseline positioning (USBL) systems aided Inertial Navigation Systems (INS). The USBL is composed of an array of hydrophones with a pre-specified structure and the INS is based on the numerically integrated measurements from triads of low cost accelerometers, rate-gyroscopes, and magnetometers, complemented with data from depth cells. The preliminary design and implementation phases will be described and the results obtained to validate the proposed approach will be presented. Finally, the next development and validation phases will be briefly outlined.