http://idl-bnc.idrc.ca:80/dspace/handle/10625/49269 2013-05-25T18:13:31Z http://idl-bnc.idrc.ca:80/dspace/handle/10625/49793 Title: New insights into gill epithelial transport: Linking ammonia excretion and sodium uptake Authors: Wright, P A; Wood, C M; Cooper, C A Abstract: Models of gill epithelial transport are rapidly changing as researchers discover more complex and specialized cell types and use genomic data to uncover completely new protein transporters. Maetz and Garcia Romeu (1964) first suggested a linkage between ammonia excretion and active Na+ uptake at the gills of freshwater animals. Although many studies have provided supporting evidence for such a linkage, only in the last 4 years with the discovery of ammonia-transporting Rhesus (Rh) glycoproteins in gill tissue have we been able to more fully understand the model of gill ammonia transport in freshwater animals. Recent evidence supports an apical “Na+/NH4 + exchange complex” consisting of several membrane transporters (Rhcg, V type H+ATPase, Na+/H+ exchanger (NHE 2/3, Na+ channel) working together as a metabolon providing an acid-trapping mechanism for apical excretion in freshwater fish. The model for gill ammonia transport in seawater is more controversial, although Rhcg also appears to be associated with Na+ transport. 2011-01-01T00:00:00Z http://idl-bnc.idrc.ca:80/dspace/handle/10625/49792 Title: Mechanisms of sodium extrusion in isolated mitochondria-rich cells of the freshwater mussel Lasmigona costata after copper exposure Authors: Nogueira, L S; Wood, C M; Bianchini, A; Gillis, P L Abstract: Gill tissues in aquatic animals are composed of various cell types, each with specific functions such as respiration, excretion, acid-base balance and ionic regulation. In the bivalves, the gill is the main route of contaminant uptake and metals can be absorbed through specific transporters in cell membranes. Among the gill cells, mitochondria-rich cells (MRCs) are considered to be the primary sites responsible for iron transport. In order to determine the mechanisms of sodium extrusion in MRCs after copper exposure, gill cells from Lasmigona costata were isolated and layered on a discontinuous Percoll gradient. The pavement cells (PCVs) and MRCs populations were confirmed by a specific mitochondrial dye (DASPEI) and Na, K-ATPase activity. It is the first time at literature that isolated fill cells from freshwater mussels are identified in two different populations and used in toxicological experiments. MRCs were then exposed to a range of copper concentrations environmentally relevant (5, 10 and 20 ug/L) for 3 hours. Copper accumulation increased in all copper exposures. In contrast, the sodium content did not change in low exposures and decreased significantly when cells were exposed to high copper concentrations. To further explore this result, both sodium and copper were measured after specific pharmacological blockade of Na, K-ATPase and carbonic anhydrase enzymes. Carbonic anhydrase inhibition suggest that sodium and copper uptake mechanisms are not dependent on a supply of protons and intracellular increase of both ions might be associated to blocked of Na extrusion via Na/HCO3-. The inhibition of Na, K-ATPase by ouabain also resulted in an increase in sodium and copper content in the MRCs. This enzyme is responsible for sodium extrusion from the cell, and the results suggest that it is also a route for copper extrusion. 2011-01-01T00:00:00Z http://idl-bnc.idrc.ca:80/dspace/handle/10625/49791 Title: Avaliação da lipoperoxidação em peixe como potencial biomarcador de contaminação aquática Authors: Gomes, E G; Machado, A A S; Hoff, M L M; Bianchini, A Abstract: A contaminação aquática por pesticidas, metais e hidrocarbonetos pode ser monitorada usando-se biomarcadores. A lipoperoxidação (LPO) é um biomarcador que pode ser induzido pela exposição a contaminantes como atrazina (pesticida), cobre (metal) e fenantreno (hidrocarboneto). Avaliar LPO em músculo, brânquia e fígado do peixe Poecilia viviparaapós exposição a cobre, atrazina e fenantreno. Machos de P. vivípara foram coletados no Arroio do Gelo (Rio Grande, RS), aclimatados à salinidade 24, fotoperíodo 12:12 h C:E e 20°C, e expostos (96 h) aatrazina(controle, controle metanol, 2, 10, 100µg/L), Cu (controle, 5, 9 e 20µg Cu/L) e fenantreno (controle, controle DMSO, 10, 20, 200µg/L) em água do mar filtrada (0,5 µm). Após expostos, os peixes foram anestesiados e retirados brânquias, fígado e músculo. A LPO foi avaliada nestes tecidos através do método TBARS. ANOVA, Kruskal Wallis e coeficiente de correlação linear de Spearman foram utilizados. Os peixes expostos ao cobre apresentaram um aumento da LPO branquial e hepática em função da concentração do metal (brânquia r = 0,83; fígado r = 0,90). A exposição a 100 µg/L de atrazina induziu aumento da LPO branquial. Por sua vez, a exposição a 10 µg/L causou uma diminuição da LPO muscular. No fígado, observou-se uma tendência de diminuição da LPO com o aumento da concentração de atrazina (r = -0,88). A exposição a 10 µg/L de fenantreno causou um aumento da LPO branquial. No músculo, este contaminante causou um aumento da LPO em função da concentração (r = 0,94). Por sua vez, não foi observada variação significativa na LPO hepática. Os resultados obtidos indicam que o cobre, a atrazina e o fenantreno afetam a LPO em tecidos de P. vivipara, porém o efeito é dependente do tecido analisado e da concentração testada. Assim, um aumento da LPO muscular remete à exposição ao fenantreno, enquanto uma diminuição da LPO hepática em paralelo a um aumento da LPO branquial remete à exposição à atrazina e um aumento da LPO hepática conjuntamente a um aumento da LPO branquial remete à exposição ao cobre. Estes resultados indicam que a LPO se constitui em um potencial biomarcador para identificar a exposição de peixes à contaminação por fenantreno, atrazina e cobre em ambientes estuarinos. 2011-01-01T00:00:00Z http://idl-bnc.idrc.ca:80/dspace/handle/10625/49790 Title: The effects of salinity on growth of juvenile mullet Mugil platanus Authors: Lisboa da Cunha, Viviana; Barcarolli, Indianara Fernanda; Sampaio, Luis André; Bianchini, Adalto Abstract: Assuming the energetic cost of osmoregulation is minimized in an isosmotic medium, the energy spared could support a higher growth rate of fish. The isosmotic point of juvenile mullet Mugil platanus was estimated at 414 mOsmol/Kg H2O, which corresponds to salinity 12‰.The aim of this study was to investigate the effect of salinity on the performance of juvenile mullet reared at different salinities. Four hundred and eighty fish (0.48±0.01g and 3.27±0.01cm) were randomly distributed into 16 tanks (50L). These tanks were connected to four recirculating aquaculture systems (RAS) equipped with UV sterilization, mechanical and biological filtration and temperature controllers. Each RAS was maintained at salinities 0, 6, 12, and 24, equivalent to 0, 50, 100 and 200% of the isosmotic point of M. platanus. During the experimental period (40 days), fish were maintained at 28.2 ± 0.1°C and oxygen saturation was always above 90%. Fish were fed 4 times per day on NRD INVE (50% protein) until apparent satiation. Results were analyzed by analysis of variance (One-Way) followed by Test of Tukey. All analyses were performed with significance level of p<0.05 and were conducted using the software Statistic 6.0. Salinity did not influence survival of juvenile mullet (p>0.05), nor influenced feed efficiency. However, final weight and specific growth rate were significantly affected at different salinities (p<0.05). Overall survival was above 90% and feed efficiency was y. Fish reared at salinities 12 and 24 grew faster than those reared at lower salinities (Figure 1 and 2) Results indicated that salinity plays an important role in juvenile mullet growth and that final weight and SGR were maximized when they were reared at salinity equivalent to, or higher, than the isosmotic point. 2011-01-01T00:00:00Z http://idl-bnc.idrc.ca:80/dspace/handle/10625/49789 Title: Dietary salt supplementation for juvenile mullet Mugil platanus reared in freshwater Authors: Lisboa da Cunha, Viviana; Barcarolli, Indianara Fernanda; Sampaio, Luis André; Bianchini, Adalto Abstract: Dietary salt supplementation for seawater/euryhaline fish reared in low salinities and/or freshwater might spare energy expenditure for osmoregulation allowing more energy for growth. Growth of mullet Mugil platanus is hampered in hypoosmotic environments, thus the objective of this study was to evaluated the effect of dietary salt supplementation on their performance when reared in freshwater. Two hundred and forty fish (4.50 ± 0.07g e 7.41 ± 0.03cm) were randomly distributed into 16 tanks (50L). These tanks were connected to a recirculating aquaculture system (RAS) equipped with UV sterilization, mechanical and biological filtration and temperature controller. A commercial diet (32%CP and 1.5% NaCl) was grinded to powder, supplemental salt was added, and cellulose was used to compensate for the extra salt. Fish were fed 3 times per day on diets supplemented with 0, 3, 6, and 9% NaCl. During the experiment, fish were maintained at temperature of 27 ± 0.1°C, oxygen saturation above 89%, 78.56 ± 1.09, 7.92 ± 0.02 and photoperiod 14C:10E. Fish were fed three times per day until apparent satiation. Biometry was made every 15 days. The data (average ± SE) were analyzed by analysis of variance (One-Way) (ANOVA) followed by Test of Tukey. All analyses were performed with significance level of p<0.05 and were conducted using the software statistic 6.0. Dietary salt supplementation did not affect survival of juvenile mullet, survival was above 90% in all tanks. Feed efficiency was not influenced by the experimental diets either, it averaged 0.31 ± 0.01 (p>0.05). However, final weight of juvenile mullet fed NaCl-enriched diets (6 and 9%) was significantly smaller than fish fed control or NaCl-enriched (3%) diets (p<0.05) (Figure 1). Considering the specific growth rate, juvenile mullet fed NaCl-enriched diet (9%) showed the poorest performance when compared to fish fed any other diet (Figure 2). Results indicated that diets supplemented with NaCl are not beneficial to juvenile mullet. Furthermore, excess salt (6% and 9% NaCl) are harmfull and compromise their growth 2011-01-01T00:00:00Z