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Tedesco S.,Environmental Research Institute | Doyle H.,Tyndall National Institute | Blasco J.,Institute Ciencias Marinas Andalucia CSIC | Redmond G.,Tyndall National Institute | Sheehan D.,Environmental Research Institute
Comparative Biochemistry and Physiology - C Toxicology and Pharmacology | Year: 2010

Relatively little is known about how gold nanoparticles (GNP) might interact in vivo with marine organisms. Mytilus edulis was exposed (24 h) to ~ 15 nm GNP, menadione and both compounds simultaneously (GNP/menadione). GNP was detected by inductively coupled plasma-optical emission spectroscopy mainly in digestive gland of samples exposed to GNP though not GNP/menadione, perhaps due to impaired feeding. Thioredoxin reductase activity and malondialdehyde levels were determined in all tissues. Thioredoxin reductase inhibition was detected only in digestive gland exposed to menadione whilst malondialdehyde levels did not vary in response to treatment in all tissues. GNP caused a decrease in the reduced/oxidized glutathione ratio in digestive gland, but no difference was found in other tissues or for other treatments. One dimensional electrophoresis of proteins containing thiol groups was performed in all tissues and revealed a reduction in protein thiols for all treatments in digestive gland. Two dimensional electrophoresis of digestive gland extracts, from GNP and control groups, showed decreased levels of thiol proteins in response to GNP which we attribute to oxidation. Our results suggest that GNP causes a modest level of oxidative stress sufficient to oxidize thiols in glutathione and proteins but without causing lipid peroxidation or induction of thioredoxin reductase activity. © 2009 Elsevier Inc. All rights reserved. Source


Montoya A.,University of Murcia | Lopez-Olmeda J.F.,University of Murcia | Yufera M.,Institute Ciencias Marinas Andalucia CSIC | Sanchez-Muros M.J.,University of Almeria | Sanchez-Vazquez F.J.,University of Murcia
Aquaculture | Year: 2010

Feeding cycles entrain biological rhythms, which enables animals to anticipate feeding times and so maximizes food utilization. In this article the effect of mealtime on locomotor activity, blood glucose, gastric pH and digestive enzymes was studied in two groups of seabream (Sparus aurata): one group received a single daily meal at random times either during the light or the dark (random feeding, RF), whereas the other group received the meal during the light period every day at the same time (periodic feeding, PF). PF fish showed strong synchronisation of locomotor activity to the light phase (97.9 ± 0.2% of their total daily activity during daytime). In addition, the locomotor activity rhythm of PF fish showed a statistically significant daily rhythm (p<0.05) for a period of 24. h, whereas RF fish did not display a statistically significant rhythm. Blood glucose levels were higher in RF fish during the 8. h following feeding. Gastric pH showed a postprandial decrease in both groups, but RF fish showed a lower daily average value (4.31 ± 0.21 compared with 5.52 ± 0.20). Amylase and alkaline protease activity increased some hours before mealtime in PF fish, whereas amylase activity increased 1. h after feeding and alkaline protease showed no statistically significant differences in RF fish. Acid protease activity showed no statistically significant differences in any group. Taken together, these results demonstrate that altering the feeding time affects the physiology and behaviour of seabream, which have the capacity to prepare themselves for a forthcoming meal. © 2010 Elsevier B.V. Source


Saavedra M.,Instituto Nacional dos Recursos Biologicos IPIMAR | Conceicao L.E.C.,University of Algarve | Barr Y.,Nofima AS | Helland S.,Nofima AS | And 3 more authors.
Aquaculture Research | Year: 2010

Phenylalanine is the precursor of tyrosine, which is involved in the synthesis of several molecules with key roles in the regulation of metabolism and growth, stress response and pigmentation. In this study, three experimental diets were tested: an amino acid (AA) balanced diet supplemented with phenylalanine, another supplemented with phenylalanine and tyrosine and a non-supplemented AA balanced diet. Rotifers were enriched with liposomes encapsulating free AA in order to obtain a balanced AA profile. The experimental diets resulted in similar larval survival, growth, enzyme activities of AA catabolism and nitrogen excretion in all treatments. High levels of skeletal deformities were registered and significant differences were found between the control and the phenylalanine treatment for the percentage of vertebral compressions in the trunk region of the vertebral column (30% in the control and 5% in the phenylalanine group). A significantly higher survival to a temperature stress test was found for larvae fed the diet supplemented with phenylalanine and tyrosine. The results suggest that supplementation of phenylalanine/tyrosine in fish diets may be useful in order to reduce skeletal deformities and mortalities caused by stress. The present study confirms that AA requirements may be sufficient for covering growth and survival but insufficient to cover other metabolic processes. © 2010 The Authors. Aquaculture Research © 2010 Blackwell Publishing Ltd. Source


Montoya A.,University of Murcia | Martins D.A.,University of Algarve | Martins D.A.,Institute Ciencias Marinas Andalucia CSIC | Yufera M.,Institute Ciencias Marinas Andalucia CSIC | Sanchez-Vazquez F.J.,University of Murcia
Aquaculture | Year: 2011

The present research looked at the ability of gilthead seabream to discriminate between two similar diets differing only in the extent of lipid oxidation. Six groups of 4 fish (254. g initial wet weight) were allowed to be selected by means of self-feeders between two complete diets (34.5% casein. +. gelatin, 14.8% fish oil. +. soybean oil, 24.8% dextrin and 25.9% vitamins, minerals, filler and binder) which differed only in the oxidation level of the lipid source: 6.2. meq/kg for the control (D1) and 100.0. meq/kg for the oxidized diet (D2). During the first nine days of the trial, fish took similar amounts of D1 and D2, although there was a clear tendency to gradually avoid D2. Finally, on day 10 fish demanded a significantly higher percentage (82%) of D1. When the diets were interchanged to investigate feeder preferences, two selection patterns were observed: three groups resumed their selection for D1 from day 7 onwards, while the other three groups did not show a clear preference for any diet until they were subjected to a 3-week fasting period (which boosts internal oxidation), after which they significantly selected D1. Taking together the results before and after fasting, gilthead seabream were able to discriminate and avoid a diet with oxidized lipids, and the physiological state of fish (oxidative stress caused by fasting) appeared to reinforce their selection/avoidance behavior. © 2011 Elsevier B.V. Source

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