Histopathological changes induced by maneb and carbaryl on some tissues of rainbow trout, Oncorhynchus mykiss

Acute toxicity of the pesticides, maneb and carbaryl, to juvenile rainbow trout were evaluated under static-renewal test conditions. Actual concentrations of maneb ranged from 0.10 mg/L to 2.00 mg/L and carbaryl ranged from 0.20 mg/L to 3.90 mg/L. The concentrations of maneb that killed 50% of the rainbow trout (3.27 ± 0.9 g) within 24-h (24-h; LC₅₀), 48-h, 72-h and 96-h were 1.19 ± 0.12, 1.04 ± 0.11, 0.92 ± 0.12 and 0.81 ± 0.14 mg/L (95% confidence limits), respectively. LC₅₀ values of carbaryl for 24-h, 48-h, 72-h and 96-h were 2.52 ± 0.71, 2.16 ± 0.63, 1.71 ± 0.46 and 1.39 ± 0.15 mg/L, respectively. None of the unexposed control fish died and the first fish died 6 h after exposure to maneb (≥1.30 mg/L), and carbaryl (≥2.60 mg/L). Lamellar edema, separation of epithelium from lamellae, lamellar fusion, swelling of the epithelial cells and epithelial cell necrosis were observed on maneb and carbaryl exposed fish. Gills also had scattered areas of focal lamellar hyperplasia. Fish exposed to pesticides had inflammation and focal necrosis in liver, trunk kidney and spleen. Maneb and carbaryl had similar histopathological lesions. In order, the most affected organs were gill, trunk kidney and liver.     

Rb-Cs ratio as an indicator of fish diet in lakes of the Patagonia, Argentina

The ratios of Rb to Cs contents were studied in five fish species from seven lakes located in the Patagonia Andean Range, Argentina in order to trace fish diet. The species studied were native velvet catfish (Diplomistes viedmensis) and creole perch (Percichthys trucha), and exotic brown trout (Salmo trutta), rainbow trout (Oncorhynchus mykiss), and brook trout (Salvenilus fontinalis). Rainbow trout specimens from two farms were also studied, as well as fish food items and native mussels (Diplodon chilensis). Rb and Cs concentrations were determined by instrumental neutron activation analysis. A positive correlation of Cs concentration in the muscle of velvet catfish with fish length was observed, probably associated with the long biological half-life of this element in this species, whereas the Rb concentration remained constant, hence inhibiting the use of Rb-Cs ratios as a tracer in this case. Seasonal variations observed for rainbow trout and Cs concentration background bias in one of the lakes studied are also a limiting factor to the use of Rb-Cs ratios as a diet tracer. Rb-Cs ratios allowed clear differentiation of rainbow trout raised in farms from the natural specimens that lived in the same environment, in agreement with Rb-Cs ratios determined in both diets. Rb-Cs ratios in rainbow trout showed significant differences between Rivadavia and Futalaufquen lakes compared to Moreno and Nahuel Huapi lakes, which could be associated with a higher participation of plankton in the diet in the first case. No relevant variations in Rb-Cs ratios of brown trout were observed, probably because of the similarity in the diet.     

Uptake and biodistribution of free and liposomally incorporated lipopolysaccharide of aeromonas salmonicida administered via different routes to rainbow trout: (Oncorhynchus mykiss)

Abstract

The effects on uptake and biodistribution of radiolabelled lipopolysaccharide (LPS) due to changing routes of administration, encapsulation of LPS within liposomes and altering liposomal surface charge were examined in rainbow trout (Oncorhynchus mykiss). ³H-labelled LPS, positively- and negatively-charged (¹⁴C-labelled) liposomes or ¹⁴C-labelled liposomes containing ³H-LPS were administered to trout via intravenous, intraperitoneal, intramuscular, or oral routes. Twenty-four hours following administration, relative uptake of LPS and multilamellar vesicles (MLV) based on detection of ³H and ^1AC, respectively, was determined in samples taken from the kidney, spleen, liver, plasma, blood cells and skeletal muscle. In general, regardless of the route of administration, ³H-LPS, ^1AC-MLV and liposomally encapsulated LPS were recovered primarily in the kidney and spleen. Intravenous administration resulted in the greatest uptake of radiolabel by the kidney and spleen, followed by the intraperitoneal and intramuscular routes. Although oral administration yielded the lowest overall uptake of labelled material, detection of ³H and ¹⁴C in the liver was enhanced when compared with the other routes. Negatively-charged MLV were delivered more efficiently to the kidney and spleen than positively-charged MLV; but negatively- and positively-charged MLV containing LPS demonstrated the opposite relationship between charge and distribution among the kidney and spleen. These results suggest that liposomal encapsulation (particularly within positively-charged MLV) enhances delivery of LPS to the primary hemopoietic organs in rainbow trout.     

Peptidylarginine deiminase gene is differentially expressed in freshwater and brackish water rainbow trout

Peptidylarginine deiminase (PADI)-like cDNA sequence was isolated from rainbow trout (Oncorhynchus mykiss). It consists of a 111-bp 5′-untranslated region, a 731-bp 3′-UTR, and a 2,010-bp open reading frame encoding a protein of 669 amino acids. In the presence of calcium ions, PADI enzymes catalyze the post-translational modification reaction generating citrulline residues. Mammalian PADI enzymes are involved in a number of regulatory processes during cell differentiation and development such as skin keratinization, myelin maturation, and histone deimination. Though five PADI isotypes have been isolated from mammals, in bony fish only one PADI enzyme is present, which contains conserved amino acid residues responsible for catalysis and calcium ion-binding. Sequence identity of piscine PADI protein sequences available at gene databases exceeds 67%. Phylogenetic analyses revealed that not only piscine, but also amphibian and avian PADI-like proteins share most identical amino acid residues with mammalian PADI2. mRNA level of trout PADI-like gene is high in skin, fin, gills, brain, and spleen of rainbow trout. Quantitative Real-Time RT-PCR revealed that PADI gene is differentially expressed in liver, trunk kidney, and spleen of two trout strains, the freshwater-cultured STEELHEAD trout and the brackish water strain BORN.     

Selenium and Mercury in Native and Introduced Fish Species of Patagonian Lakes,Argentina

A survey of mercury (Hg) and selenium (Se) contents was performed in fish collected from lakes located in two National Parks of the northern patagonian Andean range. Two native species, catfish (Diplomystes viedmensis) and creole perch (Percichthys trucha), and three introduced species, brown trout (Salmo trutta), rainbow trout (Oncorhynchus mykiss), and brook trout (Salvelinus fontinalis), were caught from lakes Nahuel Huapi, Moreno, Traful, Espejo Chico, and Guillelmo belonging to Nahuel Huapi National Park and from lakes Futalaufquen and Rivadavia, Los Alerces National Park. In lake Moreno, fish diet items were analyzed and rainbow trout grown in a farm. Hg and Se were measured in muscle and liver tissues by instrumental neutron activation analysis. The average concentrations in muscle of Hg for all species, ages, and lakes are between 0.4 to 1.0 μg g⁻¹ dry weight (DW) with a few fish, mainly native, exceeding the United States Environmental Protection Agency health advisory for freshwater fish limited consumption, and from 0.8 to 1.5 μg g⁻¹ DW for Se. Average concentrations in liver of Hg in all species range from 0.4 to 0.9 μg g⁻¹ DW. Brown trout, the top predator in these lakes, showed the lowest average Hg burden in both tissues. Se concentrations in the liver of brown and rainbow trout, up to 279 μg g⁻¹ DW, are higher than those expected for nearly pristine lakes, exceeding 20 μg g⁻¹ DW, the threshold concentration associated with Se toxicity. These species show lower Hg contents in muscle, suggesting a possible detoxification of Hg by a Se-rich diet. Creole perch and velvet catfish livers have lower Se concentrations, with a narrower span of values (2.3 to 8.5 μg g⁻¹ and 3.3 to 5.5 μg g⁻¹ DW respectively).     

Angiotensin II binding to tissues of the rainbow trout,Oncorhynchus mykiss,studied by autoradiography

Summary Tissue slices from seawater-adapted and freshwater-adapted rainbow trout, Oncorhynchus mykiss, were exposed to ¹²⁵I-angiotensin II (1.01·10^-9 M) and binding sites located by light-microscopic autoradiography. Binding/uptake was significantly inhibited by excess (10^-5 M) unlabelled angiotensin II, suggesting specific binding/uptake of angiotensin II to the ventral and dorsal aorta (smooth muscle), urinary bladder (smooth muscle and epithelial lining), glomeruli and proximal tubules, the gill (lamellae and central filament), skin (epithelium), intestine and oesophagus (mucosal epithelium), liver, heart (ventricular myocytes), adrenocortical tissue and brain (cerebellum and medulla oblongata). The specific binding/uptake of angiotensin II to tissues of freshwater- and seawater-adapted animals were generally similar. However, binding/uptake by the proximal tubules was significantly higher in freshwater-adapted trout than seawater-adapted trout. Specific binding/uptake of angiotensin II by the smooth muscle of the bladder was significantly higher in trout adapted to seawater than trout adapted to freshwater.     

Proteome Profiles of Head Kidney and Spleen of Rainbow Trout (Oncorhynchus Mykiss)

The head kidney and spleen are major lymphoid organs of the teleost fish. The authors identify proteome profiles of head kidney and spleen of rainbow trout (Oncorhynchus mykiss) using a shotgun proteomic approach. Gene ontology annotation of proteins is predicted using bioinformatic tools. This study represents detailed proteome profiles of head kidney and spleen of rainbow trout, with a total of 3241 and 2542 proteins identified, respectively. It is found that lymphoid organs are equipped with a variety of functional proteins related to defense, receptor, signal transduction, antioxidant, cytoskeleton, transport, binding, and metabolic processes. The identified proteome profiles will serve as a template for understanding lymphoid organ functions in salmonids and will increase the amount of spectra information of rainbow trout proteins in the public data repository PRIDE. This data can be accessed via ProteomeXchange with identifiers PXD008473 and PXD008478.     

The effect of mycotoxin deoxynivalenol (DON) on the oxidative stress markers in rainbow trout (Oncorhynchus mykiss,Walbaum 1792)

Deoxynivalenol (DON) is one of the most frequently detected mycotoxins in agricultural commodities used as animal feedstuff in Central Europe. This study focuses on determining effects of diets containing DON on oxidative stress markers and detoxifying enzymes in rainbow trout (Oncorhynchus mykiss). The fish were fed with commercial pellets containing DON at a concentration of 2 mg kg^?1. Selected enzymes were measured in liver, gill and caudal kidney of the fish after 23 and 32 days of the experiment. Significant differences between the control and experimental groups were observed concerning activities of glutathione peroxidase (GPx) in kidney, glutathione reductase (GR) in gill and kidney, catalase (CAT) in kidney and liver and glutathione S‐transferase (GST) in gill and liver. No significant differences were found for superoxide dismutase (SOD) gene expression, lipid peroxidation (TBARS) and the ferric reducing ability of plasma (FRAP). The data show that DON in the diet at the concentration below EC recommendation (2006/576/EC) induces oxidative stress in the rainbow trout.     

Basic physico-chemical parameters of milt from sea trout (Salmo trutta m. trutta), brook trout (Salvelinus fontinalis) and rainbow trout (Oncorhynchus mykiss)

The aim of the study was to compare the physico‐chemical parameters of milt from sea trout (Salmo trutta m. trutta), brook trout (Salvelinus fontinalis) and rainbow trout (Oncorhynchus mykiss). Milt was collected by stripping and spermatozoa concentrations, were determined and compared with sperm motility and spermatocrit values along with seminal plasma indices (pH, osmolality, sodium, potassium, chlorine, calcium, magnesium, glucose and protein concentrations). The highest spermatozoa concentration of 22.3 ± 6.7 × 10⁹ ml^?1 was found in the sea trout milt, and was significantly different of those observed in brook trout (11.9 ± 3.3 × 10⁹ ml^?1) and rainbow trout (10.7 ± 4.4 × 10⁹ ml^?1). The values for pH and K⁺ did not differ significantly among species. The mean pH was 8.0 in the milt of each species and the K⁺ concentrations ranged from 24.8 ± 7.2 to 30.5 ± 7.6 mm L^?1. Considerable differences were determined for the Ca²⁺ ions concentrations. The highest value was found in sea trout (1.7 ± 0.3 mm L^?1), while in the rainbow trout it was 0.7 ± 0.5 and in the brook trout 0.4 ± 0.1 mm L^?1. The most pronounced differences were found in the glucose concentration cause of its unnaturally low concentration in rainbow trout of the mean value of 6.0 ± 15.2 mg L^?1. The mean value in sea trout and brook trout was 185.0 ± 172.4 and 231.2 ± 148.4 mg L^?1 respectively. For all species, protein mean values were below 1.3 g L^?1. The mean osmolality was between 230.6 ± 98.6 and 272.0 ± 26.4 mOsm kg^?1 in the species studied. No correlation was found between any components determined in milt and the spermatozoa motility (P > 0.05). The sperm concentration was positively correlated with the protein content in the milt of the three species studied, other less exhibited correlation was found.     

Ontogeny and disease responses of Langerhans-like cells in lymphoid tissues of salmonid fish

The ontogeny and disease responses of Langerhans-like cells within lymphoid tissues of Atlantic salmon, Salmo salar, and rainbow trout, Oncorhynchus mykiss, were investigated. These cells were studied in situ with the use of two markers: the ultrastructural presence of Birbeck-like granules and immunohistochemistry with an antibody against human langerin/CD207 that cross-reacts with salmonid tissues. The appearance of Birbeck-like granules was observed in rainbow trout at 2 weeks post-hatch (PH) in the thymus and anterior kidney prior to the development of the spleen. Spleen first appeared at 3 weeks PH in both Atlantic salmon and rainbow trout, and Birbeck-like granules were observed within cells of the newly developed spleens. The cross-reactivity of langerin as seen by immunohistochemistry was not clearly observed in kidney and spleen until 9 weeks PH, when a strong cytoplasmic reaction was observed. To study langerin-positive cells in spleen and kidney during disease, microsporidial gill disease (MGD) in rainbow trout was used as a known disease model inducing a strong cell-mediated adaptive immune response. Langerin-positive cells in healthy fish were seen predominantly in the spleen, and only low numbers were present in the anterior kidney. During MGD, langerin-positive cell numbers were elevated in the anterior kidney and were significantly higher during 5, 6, and 10 weeks post-exposure (PE) compared with healthy control tissue. During MGD, the distribution of langerin-positive cells in the spleen and anterior kidney shifted from having significantly higher numbers of cells in the spleen than in the kidney in controls and at 1 and 4 weeks PE to having a similar distribution of the cells in the two organs at 2, 3, 5, and 6 weeks PE. By 10 weeks PE, significantly higher numbers of langerin-positive cells occurred in the anterior kidney compared with the spleen.     

Copper exposure and the degeneration of olfactory receptors in rainbow trout (Oncorhynchus mykiss)

Abstract

Sublethal concentrations of copper in water cause the degeneration of olfactory receptors in rainbow trout (Oncorhynchus mykiss). Receptor cell loss has been correlated to the loss of olfaction in fish and may cause difficulties in olfactory mediated behaviors such as migration. This study investigated the effects of three levels of copper (100, 75 and 50 mg L^?1) on the olfactory epithelium of rainbow trout. Twenty fish randomly allocated between three exposure groups and one control were exposed for 24 hours under static renewal conditions. Light and scanning electron microscopic observations of olfactory tissue were taken to determine the extent of degeneration of receptors. In addition, levels of copper and zinc in the brain tissues were analyzed to determine if the olfactory route was a significant route of copper exposure and transfer to fish brain tissue. Results indicate that degeneration of receptors is related to the concentration of copper. Levels of copper in brain were found to be below detection of the instrument. Levels of zinc were extremely variable ranging from 52 to 132 ng zinc g^?1 brain tissue.     

The effects of splenectomy and subsequent starvation on the storage of haemosiderin by the melano-macrophages of rainbow trout Salmo gairdneri Richardson

In clinically normal, cachectic and diseased teleost fish, haemosiderin is observed mostly in the melano-macrophage centres of the spleen and to a much lesser extent in the centres of the kidney and liver. When rainbow trout that had been splenectomised were starved, accumulation of haemosiderin was diverted to the kidney melano-macrophages.     

Direct effects of angiotensin II on glomerular ultrastructure in the rainbow trout,Salmo gairdneri

Summary Slices from the kidneys of the rainbow trout which were exposed to 10^-6 or 10^-5 M angiotensin II (AII) and isolated glomeruli exposed to 10^-7 or 10^-5 M AII showed ultrastructural changes compared to control tissues incubated without AII. The studies indicate that angiotensin II has a direct action on glomerular ultrastructure, flattening the epithelial podocytes and broadening the primary processes with fusion of pedicels in extreme cases. These changes suggest a probable effect of AII on water permeability of the trout glomerulus, an intrarenal action which is believed to form an essential part of the antidiuretic adaptation to increased environmental salinities.     

Uptake of the fish pathogen, Aeromonas salmonicida, by rainbow trout (Salmo gairdneri L.)

Aeromonas salmonicida was detected in the blood, kidney and spleen of rainbow trout within 2 min of immersion in a suspension containing 10⁴ cells/ml. Uptake into fish was enhanced by culturing the pathogen in low levels of nutrient, i.e., 0.1% (w/v) brain heart infusion (BHI) broth and by the addition of latex particles to the bacterial suspensions. However, there was no apparent difference in the uptake of pathogenic or non-pathogenic isolates. Moreover, the fish did not succumb to clinical signs of disease.     

Dietary Ca inhibits waterborne Cd uptake in Cd-exposed rainbow trout, Oncorhynchusmykiss

The effects of chronic exposure to waterborne Cd and elevated dietary Ca, alone and in combination, were examined in juvenile rainbow trout, Oncorhynchusmykiss. Fish were chronically exposed to 0.05 (control) or 2.56 μg/l Cd [as Cd(NO₃)₂·4H₂O] and were fed 2% body mass/day of control (29.6 mg Ca/g) or Ca-supplemented trout food (52.8 mg Ca/g as CaCl₂·2H₂O). Cd accumulated mainly in gill, liver, and kidney. Waterborne Cd inhibited unidirectional Ca uptake from water into the gill and induced hypocalcemia in the plasma on day 40. Waterborne Cd also induced an elevated Ca concentration on day 20 in the gill tissue of trout fed the Ca-supplemented diet and a decreased Ca concentration on day 35 in the gills of trout fed the control diet. Dietary Ca protected against Cd accumulation in gill, liver, and kidney, but did not protect against the inhibition of Ca uptake into the gill or plasma hypocalcemia. When fed Ca-supplemented diet and exposed to waterborne Cd, fish showed 35% mortality, compared to 0–2% in control fish and in the Cd-exposed fish with normal Ca in the diet. Growth, on the other hand, was not affected by any treatment.     

Induction of metallothionein gene expression by cadmium and the retention of the toxic metal in the tissues of rainbow trout (Salmo gairdneri)

1. When rainbow trout were exposed to cadmium by intraperitoneal injection, there was a rapid (within 3hr) and significant (approx. 63%) loss of the metal from the whole bodies of the fish.2. Of the metal retained in the bodies of the fish (approx. 37% of the injected dose), more than 98% was accounted for collectively among the liver, kidney and gills.3. Subsequent maintenance of the rainbow trout in fresh water for up to 98 days post-metal administration, indicated that there was no further loss of the cadmium accumulated in the organs studied and that the distribution of the metal among the liver, kidney and gills remained unchanged over that period.4. During this 98-day period of maintenance of the fish, tissue concentrations of metallothionein-specific mRNA and metallothionein protein were quantified using riboprobe and ELISA systems respectively. Metallothionein-specific mRNA concentrations increased rapidly (within 24 hr) before falling back to levels similar to, or slightly greater than, those found in control animals. The concentration of metallothionein protein also increased significantly (within 3 days) then remained elevated thereafter.5. Throughout the experimental period, the concentrations of zinc and copper were also monitored in the liver, kidney and gills of the rainbow trout. The concentrations of each ion differed between each of the organs but did not change during the experiment.6. The induction of metallothionein gene expression by cadmium in the liver, kidney and gill of rainbow trout and the subsequent sequestration of the toxic metal is discussed with regard to the relative levels of these other essential metal ions.     

A stromal cell line from rainbow trout spleen, RTS34st, that supports the growth of rainbow trout macrophages and produces conditioned medium with mitogenic effects of leukocytes

Summary A rainbow trout spleen cell line, RTS34, was developed from a long-term hemopoietic culture. This cell line consisted of a mixed stromal cell layer with an associated cell population of macrophage-like cells that formed proliferative foci and released nonadherent progeny cells into the culture medium. A stromal cell line, RTS34st, was isolated from the RTS34 cell line. RTS34st cultures contained cells with fibroblast-like and epithelial-like morphologies and showed enhanced [³H]thymidine incorporation in response to either FBS or rainbow trout serum. The combination of FBS and trout serum was synergistic. Conditioned medium from RTS34st stimulated thymidine incorporation by peripheral blood and head kidney leukocytes, but not by leukocytes from the spleen. In addition, RTS34st provided a hemopoietic inductive microenvironment for immature precursor cells, selectively supporting the growth of macrophage-like cells. Therefore, RTS34st appears useful for studying the different roles of the stroma in regulating hemopoiesis in fish.