Brain distribution of myosin Va in rainbow trout Oncorhynchus mykiss

This study presents data on myosin Va localization in the central nervous system of rainbow trout. We demonstrate, via immunoblots and immunocytochemistry, the expression of myosin Va in several neuronal populations of forebrain, midbrain, hindbrain and spinal cord. The neuronal populations that express myosin Va in trout constitute a very diverse group that do not seem to have many specific similarities such as neurotransmitters used, cellular size or length of their processes. The intensity of the immunoreactivity and the number of immunoreactive cells differ from region to region. Although there is a broad distribution of myosin Va, it is not present in all neuronal populations. This result is in agreement with a previous report, which indicated that myosin Va is approximately as abundant as conventional myosin II and kinesin, and it is broadly involved in neuronal motility events such as axoplasmatic transport. Furthermore, this distribution pattern is in accordance with what was shown in rats and mice; it indicates phylogenetic maintenance of the myosin Va main functions.     

Antibacterial proteins in rainbow trout, Oncorhynchus mykiss

Antibacterial proteins are an important part of the innate immune system for all animals. They have been extensively studied in mammals, amphibians and invertebrates, but have received only scant attention in fish. Their expression and processing, however, provide a way of monitoring defence vigour during development or with seasonal changes in physiology. The aim of the present work was to identify and characterise antibacterial proteins in rainbow trout. In vitro analyses of extracts of the peripheral blood leucocytes, head kidney leucocytes and mucus from adult unstimulated (non-immune) fish showed marked antibacterial activity against Gram positive bacteria. Fractionation by ion exchange chromatography and RP-HPLC of head kidney extracts showed the presence of two forms of lysozyme but no constitutively expressed antimicrobial proteins of < 10 kDa. By contrast, chromatographic analyses of mucus revealed at least four antibacterial proteins. Two are conventional lysozymes, a third is an unusual lysozyme-like protein with a low isoelectric point, and the fourth is a highly hydrophobic, cationic peptide of c. 3 kDa.     

Tissue-specific distribution patterns of retinoids and didehydroretinoids in rainbow trout Oncorhynchus mykiss

Retinoids (vitamin A) are known to be involved in many key biological functions in mammals, such as embryonic development, reproduction or vision. Besides standard vitamin A forms, freshwater fish tissues contain high levels of didehydroretinoids or vitamin A₂ forms. However, the tissue distribution, metabolism and function of both standard and particularly the didehydroretinoids are still poorly known in fish. In this study, we have quantified the levels of retinoids, including retinol, retinaldehyde, retinyl palmitate and their corresponding didehydro forms, as well as the levels of the active polar retinoids all-trans-, 9-cis- and 13-cis-retinoic acid in distinct tissues of juvenile rainbow trout. Our results indicate that the liver is clearly the main retinoid storage tissue in juvenile rainbow trout. Didehydroretinoids were dominant over retinoids in all analyzed tissues with the exception of plasma. Additionally, significant differences among tissues were observed between retinoids and didehydroretinoids, such as differences in the ester profiles and the proportions between free and esterified forms, suggesting that mechanisms that favor the utilization or storage of one of the other groups of compounds might exist in fish. Our data also show the presence of polar retinoids in different tissues of fish at the fmol/g scale. Overall, this study clearly demonstrates the presence of tissue-specific patterns of accumulation of both polar and nonpolar retinoids in fish tissues. The biological relevance of these findings should be the focus of future studies.     

虹鳟对时间和地点的学习记忆(英文)

为确定虹鳟(Oncorhynchus mykiss)是否能将日投放两次食物的不同时间和地点联系起来,在30天内,于09:00-10:00将食饵投放在水族箱一侧,于15:00-16:00将食饵投放在水族箱另一侧.在第21天和28天,不放食饵以确定虹鳟对时间-地点的学习记忆.结果表明,虹鳟将不同时间和地点联系起来以获取食物,并且在水族箱两个投放食饵之处均表现出预取食活动,提示该物种具有控制时间-地点学习任务的内在机制.     

Localization of somatostatin mRNAs in the brain and pancreas of rainbow trout (Oncorhynchus mykiss)

Rainbow trout possess three distinct mRNAs, each encoding a separate precursor: PPSS I, which contains a 14-amino acid sequence at its C-terminus (somatostatin-14) that is highly conserved among vertebrates, as well as two others, PPSS II' and PPSS II", both containing [Tyr(7), Gly(10)]-somatostatin-14 at their C-terminus. In this study, we used RNA template-specific PCR and in situ hybridization to determine the distribution and cellular localization of PPSS mRNAs in the brain and Brockmann body of rainbow trout. PPSS I, PPSS II' and PPSS II" were expressed in the Brockmann body and pituitary; the expression of PPSS mRNAs in the brain was region specific. PPSS I mRNA was expressed in the Brockmann body predominantly by cells other than those that expressed PPSS IIs; however, there were several instances where PPSS I and PPSS IIs were co-expressed within the same cell. Of the PPSS II-expressing cells, many were observed to express both PPSS II' and PPSS II" mRNA; however, some cells expressed only PPSS II' mRNA, while other cells expressed only PPSS II" mRNA. In the brain, PPSS I mRNA was expressed in the optic tectum (OT) and in many hypothalamic nuclei, including the nucleus rotundus (NR), nucleus anterioris hypothalami (NAH), nucleus anterior tuberis (NAT), nucleus lateral tuberis (NLT), as well as in the pituitary (adenohypophysis). PPSS II" mRNA was present in the same regions as PPSS I mRNA; however, PPSS II' mRNA was present primarily in OT, NAT, NLT and adenohypohysis. These results indicate that PPSS mRNAs are expressed differently by different cells, suggesting that cell-specific mechanisms are involved with the control of PPSS expression and that particular biological responses may be associated with a specific SS isoform.     

Domestication shapes morphology in rainbow trout Oncorhynchus mykiss

In this study, clonal lines from North American resident and migratory populations of rainbow trout Oncorhynchus mykiss adapted to different geographical conditions and with different domestication histories were characterized morphologically. Lines reared in a common‐garden experiment were characterized for external shape and meristic values, searching for a general pattern of morphological variation due to exposure to captive conditions. A sharp distinction was identified between wild and captive lines. The body profile was deeper in captive lines, with longer dorsal and anal fins and shorter and deeper caudal peduncles. Highly significant differences were also identified in meristic values among the lines but no consistent relation between meristic values and domestication status was detected. This morphological characterization will facilitate the selection of lines with divergent phenotypes for subsequent quantitative trait loci analysis, aimed at identifying genome regions linked with morphological adaptive response to captive conditions.     

A blue variant in the rainbow trout, Oncorhynchus mykiss Walbaum

A blue variant of the rainbow trout, which appeared in a French fish farm, displayed an iridescent body color that was cobalt blue on the back, lighter on the undersides, and silvery on the belly and which held up to adult stage. This color was supposed to result from a Tyndall effect involving a structural arrangement of melanin pigments because it disappeared when it was associated with a depigmenting gene. This blue variant appeared to be governed by an autosomal recessive gene. Blue fry survival and body weight were about 25% less than those of wild-type sibs, but no major problem was observed in further breeding performances, including reproduction. These features do not correspond with those of the blue variants previously described in the rainbow trout.     

Ubiquitin genes in rainbow trout (Oncorhynchus mykiss)

Ubiquitin is a small protein involved in intracellular proteolysis. It is highly conserved throughout eukaryotic phyla and has been detected in such diverse species as yeast, barley, Drosophila and man. A previous study showed that chromatin of rainbow trout testis contains free ubiquitin with a sequence similar to that of other phyla. In the present study, which focused on rainbow trout but included eleven other species, it is shown that fish ubiquitin genetic organisation and expression are similar to those of other phylogenetic groups through the following set of observations: (a) Multiple loci were detected, (b) These loci encode repeats of ubiquitin, (c) Although the DNA sequences are not conserved, the encoded amino acid sequences are fully conserved, (d) The expression of ubiquitin was influenced by cell culture conditions and viral infection.     

Coronary vascular volume remodelling in rainbow trout Oncorhynchus mykiss

The 34% increase in relative ventricular mass (M_rv) resulting from chronic anaemia (induced by an intraperitoneal injection of phenylhydrazine hydrochloride) was accompanied by a 117% increase in coronary vascular volume of diploid rainbow trout Oncorhynchus mykiss. Coronary vascular volume of normocythemic triploid fish was similar to that of normocythemic diploid fish despite a larger M_rv. These observations, in combination with previous studies, suggest that the vascularity of compact myocardium in O. mykiss can vary independently of M_rv.     

Exhaustive exercise and the cellular stress response in rainbow trout, Oncorhynchus mykiss

The goal of this study was to examine the cellular response to exhaustive exercise in male and female rainbow trout to determine if HSPs are involved in the early stages of the recovery process. Levels of HSPs and key metabolic parameters were measured in white muscle, heart plasma, and blood plasma throughout 6 h of recovery from exhaustive burst exercise. Plasma creatine kinase (CK) was also quantified as an indicator of exercise-induced tissue damage. The observed trends in ATP and lactate were consistent with established patterns of exhaustion and the beginnings of metabolic recovery. However, no upregulation of hsp70, hsp30, or hsp90 was evident in heart or muscle tissue of males or females, and plasma CK measurements suggest that tissue damage was minimal. Our results indicate that hsp70, hsp30, and hsp90 are not part of the early recovery process from burst exercise in fish, perhaps due to the maintenance of core temperatures as well as a lack of exercise-induced tissue damage.     

Formation of chromosome aberrations in androgenetic rainbow trout Oncorhynchus mykiss

Residues of maternal nuclear DNA in the form of chromosome fragments were observed in the healthy and morphologically normal androgenetic rainbow trout Oncorhynchus mykiss. A hypothetical model for formation of chromosome re‐arrangements caused by the incomplete maternal nuclear DNA inactivation in the androgenetic rainbow trout was proposed in the present paper.     

Distribution of canthaxanthin in immature rainbow trout Oncorhynchus mykiss serum

• 1.1. The present study was undertaken in order to define the distribution of canthaxanthin between the lipoprotein fractions in serum of immature rainbow trout fed a diet supplemented with synthetic canthaxanthin (80 mg/kg).
• 2.2. Lipoproteins were separated by density-gradient ultracentrifugation.
• 3.3. Canthaxanthin was found in all lipoprotein fractions, in different amounts according to the density of the lipoprotein fraction: VLDL, 13.9%; LDL, 15.2% or LDL, 29.1% since the density of the first fraction was 1.006 g/ml; HDL, 60.4% and VHDL, 10.5%.

     

Identification,characterization and genetic mapping of TLR1 loci in rainbow trout (Oncorhynchus mykiss)

Induction of innate immune pathways is critical for early anti-microbial defense but there is limited understanding of how teleosts recognize microbial molecules and activate these pathways. In mammals, Toll-like receptors (TLR) 1 and 2 form a heterodimer involved in recognizing peptidoglycans and lipoproteins of microbial origin. Herein, we identify and describe the rainbow trout (Oncorhynchus mykiss) TLR1 gene ortholog and its mRNA expression. Two TLR1 loci were identified from a rainbow trout bacterial artificial chromosome (BAC) library using DNA sequencing and genetic linkage analyses. Full length cDNA clone and direct sequencing of four BACs revealed an intact omTLR1 open reading frame (ORF) located on chromosome 14 and a second locus on chromosome 25 that contains a TLR1 pseudogene. The duplicated trout loci exhibit conserved synteny with other fish genomes that extends beyond the TLR1 gene sequences. The omTLR1 gene includes a single large coding exon similar to all other described TLR1 genes, but unlike other teleosts it also has a 5′ UTR exon and intron preceding the large coding exon. The omTLR1 ORF is predicted to encode an 808 amino-acid protein with 69% similarity to the Fugu TLR1 and a conserved pattern of predicted leucine-rich repeats (LRR). Phylogenetic analysis grouped omTLR1 with other fish TLR1 genes on a separate branch from the avian TLR1 and mammalian TLR1, 6 and 10. omTLR1 expression levels in rainbow trout anterior kidney leukocytes were not affected by the human TLR2/6 and TLR2/1 agonists diacylated lipoprotein (Pam₂CSK₄) and triacylated lipoprotein (Pam₃CSK₄). However, due to the lack of TLR6 and 10 genes in teleost genomes and up-regulation of TLR1 mRNA in response to LPS and bacterial infection in other fish species we hypothesize an important role for omTLR1 in anti-microbial immunity. Therefore, the identification of a TLR2 ortholog in rainbow trout and the development of assays to measure ligand binding and downstream signaling are critical for future elucidation of omTLR1 functions.     

Evidence for an intrarenal renin-angiotensin system in the rainbow trout, Oncorhynchus mykiss

Physiological and molecular approaches were used to investigate the existence of an intrarenal renin-angiotensin system (RAS) in rainbow trout. Inhibition of angiotensin-converting enzyme by captopril (5 x 10(-4 )M) rapidly decreased vascular resistance of the trunk of the trout, perfused at 19 mmHg, resulting in an increased perfusate flow rate and a decreased intrarenal dorsal aortic pressure. A profound diuresis occurred in the in situ perfused kidney and reflected both increased glomerular filtration rates and decreased water reabsorption (osmolyte reabsorption was unchanged). Renal and vascular parameters recovered once captopril treatment was stopped. Diuretic and vascular effects of captopril on the in situ trout kidney concur with an inhibition of known vasoconstrictor and antidiuretic actions of angiotensin II. However, at a higher perfusion pressure (28 mmHg), captopril had no effect on intrarenal aortic pressure or perfusate and urine flow rates, suggesting that the trout intrarenal RAS is activated by low perfusion pressures/flows. Existence of the renal RAS in trout was further supported by evidence for angiotensinogen gene expression in kidney as well as liver.     

Marker-assisted estimation of quantitative genetic parameters in rainbow trout,Oncorhynchus mykiss

Estimation of quantitative genetic parameters conventionally requires known pedigree structure. However, several methods have recently been developed to circumvent this requirement by inferring relationship structure from molecular marker data. Here, two such marker-assisted methodologies were used and compared in an aquaculture population of rainbow trout (Oncorhynchus mykiss). Firstly a regression-based model employing estimates of pairwise relatedness was applied, and secondly a Markov Chain Monte Carlo (MCMC) procedure was employed to reconstruct full-sibships and hence an explicit pedigree. While both methods were effective in detecting significant components of genetic variance and covariance for size and spawning time traits, the regression model resulted in estimates that were quantitatively unreliable, having both significant bias and low precision. This result can be largely attributed to poor performance of the pairwise relatedness estimator. In contrast, genetic parameters estimated from the reconstructed pedigree showed close agreement with ideal values obtained from the true pedigree. Although not significantly biased, parameters based on the reconstructed pedigree were underestimated relative to ideal values. This was due to the complex structure of the true pedigree in which high numbers of half-sibling relationships resulted in inaccurate partitioning of full-sibships, and additional unrecognized relatedness between families.     

Behavioural fever boosts the inflammatory response in rainbow trout Oncorhynchus mykiss

Behavioural fever, manifested as an increased preferred temperature, was shown in rainbow trout Oncorhynchus mykiss following an injection of bacterial lipopolysaccharide. Simulated behavioural fever, through a 2·5° C water temperature rise following bacterial lipopolysaccharide injection, enhanced the expression of the cytokine interleukin-1β, in comparison with an untreated group held at the initial temperature. The present findings show that an important mediator in the immune response can be boosted through behavioural fever in fishes.     

Peripheral serotonin dynamics in the rainbow trout (Oncorhynchus mykiss)

Serotonin (5-hydroxytryptamine, 5-HT) occurs in a wide range of tissues throughout the body of the rainbow trout. Results reported here indicate that the main peripheral sources of serotonin are the intestinal tract and the gill epithelium (levels above 1500 ng/g). The high intestinal serotonin concentration is mostly due to serotoninergic nerve fibres, which are present at high density in the intestinal wall. Only about 2% of serotonin is associated with mucosal enterochromaffin cells. In the remaining tissues studied serotonin concentration was below 160 ng/g: the highest concentrations were seen in the anterior and posterior kidneys, followed by the liver, heart, and spleen. 5-Hydroxyindolacetic acid (5-HIAA) levels, except in plasma, were generally lower than serotonin levels, and were below our detection limits in heart, spleen and posterior kidney. Acute d-fenfluramine treatment (5 or 15 mg/kg i.p.) significantly increased 5-HIAA/5-HT ratio in the anterior intestine, pyloric caeca and plasma. Serotonin released from intestinal serotoninergic fibres in response to d-fenfluramine treatment is metabolized locally, and only a small part reaches the blood, from where it can be taken up and metabolized by other peripheral tissues, such as the liver and gill epithelium. The non-metabolized serotonin pool in the blood appears to be located extracellularly, not intracellularly as in mammals. In view of these findings, we present an overview of peripheral serotonin dynamics in rainbow trout.     

Streptococcus iniae type II infections in rainbow trout Oncorhynchus mykiss

Clinical and pathological findings (anorexia, hemorrhage, lethargy, loss of orientation and exophthalmia) indicated that Streptococcus iniae type II is responsible for a fatal disease in rainbow trout. Histopathological findings revealed that S. iniae type II produces a systemic disease, including a diffuse necrotizing myositis. The distribution of viable bacteria in infected tissues substantiated the pathological findings, confirming that S. iniae type II is responsible for a generalized septic disease of rainbow trout.