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PubMed1992

[Triiodothyronine is needed for the acclimatization of brown trout (Salmo trutta) or rainbow trout (Oncorhynchus mykiss) to seawater].

Brown and rainbow trout, held in freshwater at 13 +/- 1 degrees, were injected, every 3 days, with iopanoic acid (IOP: 5 mg/100 g body wt), an inhibitor of deiodination of thyroxine (T4) to triiodothyronine (T3). One group of IOP-treated rainbow trout was immersed in T3 (20 micrograms/l water). In IOP trout, plasma T3 fell to very low levels by day 7, while changes in T4 levels were less marked. In IOP + T3 trout plasma T3 increased fivefold, plasma T4 being unchanged. No mortality occurred and plasma osmolarity (OP) was not altered by any treatment. After direct transfer to seawater (30/1000), IOP trout were unable to acclimate to salinity: all died within 2 or 3 days, while the survival at day 3 was 100% in control brown trout and 45 and 74% in control and IOP + T3 rainbow trout respectively. OP increased more in IOP and less in IOP + T3 than in controls. There was a significant inverse correlation between T3, but not T4, plasma level, at the time of transfer and the OP 1 day later. In conclusion, although T3 does not play a significant role in osmoregulation in freshwater, T3 and therefore the deiodination of T4 into T3, were required for the development of hypo-osmoregulatory capacity involved in acclimation of trout to seawater.

Adaptation, Physiological↗
PubMed2003

Streptococcus iniae expresses a cell surface non-immune trout immunoglobulin-binding factor when grown in normal trout serum.

Three capsulated isolates of S. iniae representing serotype I and II and being arginine dihydrolase positive, negative or variable (AD+ve, AD-ve, AD+-ve) were investigated for their ability to bind rainbow trout serum immunoglobulin by the Fc region. Using a coagglutination assay with bacteria grown in Todd-Hewitt broth (THB), no evidence of non-specific Fc-binding of trout immunoglobulin (Ig) was obtained. However, when grown in normal trout serum, all isolates produced similar protein patterns in SDS-PAGE, but they were markedly different from the patterns of the bacteria grown in THB. Some bands with MW 70 kDa and over 100 kDa were very intense in the profiles of the serum-grown isolates. In Western blots, these bands of all isolates were immunostained with the conjugated goat antiserum to trout Ig, after blocking with normal goat serum, demonstrating that the bacteria had bound the trout Ig during growth in the serum. When the isolates were grown overnight in trout antiserum against Lactococcus garvieae they coagglutinated with L. garvieae cells but S. iniae isolates grown in normal trout serum did not. These data indicate that S. iniae grown in serum express surface factors which can bind trout Ig by the Fc-region.

Agglutination Tests↗
PubMed1995

cDNA sequence and structure of a trout HMG-2 gene. Evidence for a trout-specific 3'-untranslated region.

A complete cDNA sequence (1026 bp) and a partial structure of a gene encoding the trout testis chromosomal HMG (high mobility group) 2 protein (HMG-T2) is presented. The deduced protein consists of 214 amino acids and shares over 80% similarity to the trout HMG-1 protein (HMG-T1) as well as to the mammalian or avian HMG-2 proteins. Northern blot analysis revealed two transcripts, a major one of 1.2 kb and a minor one of 1.6 kb. Southern analysis and polymerase chain reaction of trout genomic DNA indicated that the HMG-T2 gene is encoded by several introncontaining genes. The 5'-UTR (untranslated region) of the HMG-T2 is interrupted by an intron and the coding region of the HMG-T2 is divided into four exons by three relatively short introns (173, 91 and 78 bp). The exon/intron boundaries of trout HMG-2 are identical to those of human HMG-2, as reported earlier [Shirakawa and Yoshida, J. Biol. Chem. 267 (1992) 6641-6645], suggesting the evolution of the HMG-1/2 family genes from a common ancestor. Phylogenetic analysis indicated that the common ancestor of trout HMG-1/2 genes very likely diverged from the ancestor of the mammalian (or avian) HMG-1/2 genes before its separation into two distinct mammalian or (avian) HMG-1 and HMG-2 genes. Sequence comparisons of the 3'UTR of trout HMG-2 cDNA with the corresponding regions in the mammalian (or avian) HMG-2 revealed that the trout 3'-UTR was clearly distinct from the 3'-UTR of the mammalian or avian HMG-2 cDNAs which were otherwise remarkably well conserved.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed2002

Relative sensitivity of bull trout (Salvelinus confluentus) and rainbow trout (Oncorhynchus mykiss) to acute copper toxicity.

Bull trout (Salvelinus confluentus) were recently listed as threatened in the United States under the federal Endangered Species Act. Past and present habitat for this species includes waterways contaminated with heavy metals released from mining activities. Because the sensitivity of this species to copper was previously unknown, we conducted acute copper toxicity tests with bull and rainbow trout (Oncorhynchus mykiss) in side-by-side comparison tests. Bioassays were conducted using water at two temperatures (8 degrees C and 16 degrees C) and two hardness levels (100 and 220 mg/L as CaCO3). At a water hardness of 100 mg/L, both species were less sensitive to copper when tested at 16 degrees C compared to 8 degrees C. The two species had similar sensitivity to copper in 100-mg/ L hardness water, but bull trout were 2.5 to 4 times less sensitive than rainbow trout in 220-mg/L hardness water. However, when our results were viewed in the context of the broader literature on rainbow trout sensitivity to copper, the sensitivities of the two species appeared similar. This suggests that adoption of toxicity thresholds that are protective of rainbow trout would be protective of bull trout; however, an additional safety factor may be warranted because of the additional level of protection necessary for this federally threatened species.

Animals↗
PubMed1994

Cloning and sequencing of the major rainbow trout constitutive cytochrome P450 (CYP2K1): identification of a new cytochrome P450 gene subfamily and its expression in mature rainbow trout liver and trunk kidney.

We have cloned and sequenced a full-length cDNA encoding the major constitutive rainbow trout liver cytochrome P450 that we had earlier designated as cytochrome P450 LMC2 (Arch. Biochem. Biophys. 268, 227, 1989). The 1859-bp cDNA was isolated from a male rainbow trout liver cDNA library and contained an open reading frame encoding for a protein of 504 amino acids and having a calculated molecular weight of 56,795. From nucleotide and amino acid sequence comparisons, the trout P450 LMC2 has been assigned to a new cytochrome P450 gene subfamily designated P4502K1 or CYP2K1. Marked differences in the sex- and tissue-specific expression of this gene were found at both the transcriptional and translational level in sexually mature rainbow trout liver and trunk kidney. Transcriptional expression investigated by Northern analysis of total RNA using a 440-bp 3'-terminal cDNA probe (2K1,7c) showed sexual and organ differences. Mature male trunk kidney expressed 2K1,7c-hybridizable mRNA to a substantially greater extent than did female trunk kidney, with multiple mRNA bands appearing in approximately the 2.8- and 1.9-kb region. While the livers of some males displayed separate 2.8-kb hybridizable bands, such bands were generally undetectable in female liver samples. By contrast, 1.9-kb mRNA bands were found at generally similar concentrations in the livers of both sexes. Taking into consideration the individual biological variabilities, it was apparent that mature male trout expressed the 2.8-kb mRNA much more strongly in trunk kidney than in liver. Translational expression, analyzed by Western blotting of microsomes separated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and probed with rabbit polyclonal antibody and two different monoclonal antibodies prepared against P450 LMC2, demonstrated corresponding sex- and organ-related differences in P450 protein expression. Southern analysis of sexually mature male trout genomic DNA suggested that CYP2K1 is not a single copy gene, thus providing additional evidence for the complexity of the CYP2K1 system in rainbow trout.

Aging↗
PubMed2003

Passive immunization of rainbow trout, Oncorhynchus mykiss (Walbaum), against Flavobacterium psychrophilum, the causative agent of bacterial coldwater disease and rainbow trout fry syndrome.

Flavobacterium psychrophilum, the causative agent of bacterial coldwater disease (CWD) and rainbow trout fry syndrome (RTFS), causes high mortality in cultured salmonids. The present study was designed to determine the role antibody plays in conferring protection to rainbow trout fry, Oncorhynchus mykiss (Walbaum), by passive immunization with convalescent serum or serum from adult rainbow trout immunized with F. psychrophilum, and goat anti-F. psychrophilum serum. In each experiment, rainbow trout fry were injected intraperitoneally with antiserum and challenged by subcutaneous injection with a virulent strain (CSF-259-93) of F. psychrophilum 24-h post-immunization. Relative percentage survival (RPS) ranged from 9-42% when rainbow trout fry (mean weight 1.3 g) were injected with a 1:2 dilution of 25 microL of convalescent serum ranging in enzyme-linked immunosorbent assay antibody titres from 1600-102400. Rainbow trout fry (mean weight 1.0 g) passively immunized with 25 microL of serum from immunized adult fish exhibited RPS values of up to 57%. In each of these experiments, RPS increased with increasing antibody titres against F. psychrophilum. Passive immunization with 25 or 50 microL goat anti-F. psychrophilum serum, however, did not confer protection to fry (mean weight 1.3 g). These results suggest that trout antibody plays a role in conferring protection to F. psychrophilum, but antibody alone is unable to provide complete protection.

Animals↗
PubMed2001

Genetic characterization of hybridization and introgression between anadromous rainbow trout (Oncorhynchus mykiss irideus) and coastal cutthroat trout (O. clarki clarki).

Interspecific hybridization represents a dynamic evolutionary phenomenon and major conservation problem in salmonid fishes. In this study we used amplified fragment length polymorphisms (AFLP) and mitochondrial DNA (mtDNA) markers to describe the extent and characterize the pattern of hybridization and introgression between coastal rainbow trout (Oncorhynchus mykiss irideus) and coastal cutthroat trout (O. clarki clarki). Hybrid individuals were initially identified using principle coordinate analysis of 133 polymorphic AFLP markers. Subsequent analysis using 23 diagnostic AFLP markers revealed the presence of F1, rainbow trout backcross, cutthroat trout backcross and later-generation hybrids. mtDNA analysis demonstrated equal numbers of F1 hybrids with rainbow and cutthroat trout mtDNA indicating reciprocal mating of the parental types. In contrast, rainbow and cutthroat trout backcross hybrids always exhibited the mtDNA from the recurrent parent, indicating a male hybrid mating with a pure female. This study illustrates the usefulness of the AFLP technique for generating large numbers of species diagnostic markers. The pattern of hybridization raises many questions concerning the existence and action of reproductive isolating mechanisms between these two species. Our findings are consistent with the hypothesis that introgression between anadromous populations of coastal rainbow and coastal cutthroat trout is limited by an environment-dependent reduction in hybrid fitness.

Animals↗
PubMed1978

Primary structure of hemoglobin from trout (Salmo irideus). Amino acid sequence of alpha chain of Hb trout I.

The amino acid sequence of the alpha chain of the hemoglobin component of trout's blood which is devoid of heterotropyc phenomena, i.e. Hb trout I, is presented. The sequence has been determined by analyzing the soluble tryptic peptides obtained from the whole globin and the peptides obtained after redigesting the insoluble 'core' with chymotrypsin. Alignment of the peptides with the structure of human as well as carp and Catostomus clarkii alpha chains shows that Hb trout I alpha chain differs from the corresponding human protein by 43% amino acid substitutions and from the two other fish by 34.5% and 33.1%, respectively. Further comparison of sequence data available for the N-terminal region suggests that the divergence between Hb trout I and IV, the other major hemoglobin component of trout's blood, is greater than that found between each trout hemoglobin and the other two fishes (carp and C. clarkii.).

Amino Acid Sequence↗
PubMed1994

Cadmium toxicity to rainbow trout Oncorhynchus mykiss Walbaum and brown trout Salmo trutta L. over extended exposure periods.

The toxicity of cadmium in water is well known, but there have been few reports on the long-term effects of this metal on fish at concentrations near the European inland water standard of 5 micrograms Cd liter-1. This paper describes experiments in which adult rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta were exposed to cadmium concentrations near water quality standard levels for periods of up to 90 weeks. The survival and growth of these fish were assessed, and sperm and eggs were stripped from them to conduct early-life-stage tests. Continuous exposure of rainbow trout adults to cadmium concentrations of up to 5.5 micrograms Cd liter-1 did not affect their survival or growth. However, eggs obtained from rainbow trout exposed to 1.8 and 3.4 micrograms Cd liter-1 failed to develop to the fry stage. Oogenesis appeared to be delayed in brown trout exposed to 9.3 and 29.1 micrograms Cd liter-1, but the eggs and fry that were produced developed normally after fertilization. Adult brown trout suffered considerable mortality in the 29.1 micrograms Cd liter-1 treatment, with a median period of survival of 54 weeks.

Animals↗
PubMed1983

Primary structure of hemoglobin from trout (Salmo irideus) amino acid sequence of the beta chain of trout Hb I.

The amino acid sequence of the beta chain of trout Hb I is presented; it adds to the previously reported sequence of the alpha chain (Bossa et al. (1978) Biochim. Biophys. Acta 536, 298-305), thus completing the primary structure of the hemoglobin component of trout's blood devoid of heterotropic phenomena. Comparison of beta chain from trout Hb I with the corresponding sequences from human and carp shows differences of 46.6% and 34.7%, respectively; the sequence (almost completed) of the beta chain from the other major hemoglobin component of trout, i.e., trout Hb IV, displays more differences (41.6%) from beta trout Hb I than from the corresponding chain of other fishes, such as carp or goldfish.

Amino Acid Sequence↗
PubMed1998

Effect of cryopreservation on the fine structure of spermatozoa of rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta F. fario)

Freeze-fracture electron microscopy has revealed that changes are induced in the organization of the plasma membranes of spermatozoa of rainbow and brown trout when they are cryopreserved. Electron-micrographic images of spermatozoa that had not been exposed to cryopreservation showed a protoplasmic surface with particles homogeneously distributed. The concentration of the particles was low. In the median portion of the tail the authors observed longitudinal strips, consisting of particles located along the bands. In the neck of the spermatozoon the particles were aggregated in a chaotic manner. Electron micrographs of trout spermatozoa that had been cryopreserved showed particles grouped in rounded clusters on the protoplasmic surfaces of both the head and the tail. In some spermatozoa, folding of the protoplasmic membrane, with the particle-free sites, were found. The dimensions of the clusters and the spaces that were free of particles suggest that, after thawing, the spermatozoa of the brown trout is likely to experience greater difficulty in restoring their physiological integrity than those of the rainbow trout. These results suggest that the membrane proteins of spermatozoa of the species of trout that were studied possess high motility and diffuse, with the formation of clusters, in very short periods of time (about 30 s). The changes in membrane structure of the trout spermatozoa following cryopreservation appear to indicate high lability. Copyright 1998 Academic Press.

Journal Article↗
PubMed2000

Cardiovascular actions of centrally and peripherally administered trout urotensin-I in the trout.

The cardiovascular effects of centrally and peripherally administered synthetic trout urotensin (U)-I, a member of the corticotropin-releasing hormone family of neuroendocrine peptides, were investigated in unanesthetized rainbow trout Oncorhynchus mykiss. Intracerebroventricular injections of U-I (5.0 and 12.5 pmol) produced a sustained increase in mean dorsal aortic blood pressure (P(DA)) without significant change in heart rate (HR). This elevation in P(DA) was associated with an increase in cardiac output, but systemic vascular resistance did not change. Intra-arterial injection of U-I (12.5-500 pmol) evoked a dose-dependent increase in P(DA), but in contrast to the hemodynamic effects of centrally administered U-I, the hypertensive effect was associated with an increase in systemic vascular resistance and an initial fall in cardiac output. HR did not change or underwent a delayed increase. Pretreatment of trout with prazosin, an alpha-adrenoreceptor antagonist, completely abolished the rise in arterial blood pressure after intra-arterial administration of U-I, which was replaced by a sustained hypotension and tachycardia. Trout U-I produced a dose-dependent (pD(2) = 7.74 +/- 0.08) relaxation of preconstricted rings of isolated trout arterial vascular smooth muscle, suggesting that the primary action of the peptide in the periphery is vasorelaxation that is rapidly reversed by release of catecholamines. Our results suggest that U-I may regulate blood pressure in trout by acting centrally as a neurotransmitter and/or neuromodulator and peripherally as a neurohormone functioning either as a locally acting vasodilator or as a potent secretagogue of catecholamines.

Adrenergic alpha-Antagonists↗
PubMed2004

Comparative susceptibility of Atlantic salmon, lake trout and rainbow trout to Myxobolus cerebralis in controlled laboratory exposures.

The susceptibility of lake trout Salvelinus namaycush, rainbow trout Oncorhynchus mykiss and Atlantic salmon Salmo salar to Myxobolus cerebralis, the causative agent of whirling disease, was compared in controlled laboratory exposures. A total of 450 (225 for each dose) fry for each species were exposed to a low (200 spores per fish) or high (2000 spores per fish) dose of the infective triactinomyxon. At 22 wk post-exposure, 60 fish from each group, as well as controls for each species, were examined for clinical signs (whirling behavior, blacktail, deformed heads and skeletal deformities), microscopic lesions, and presence of spores. Rainbow trout were highly susceptible to infection, with 100% being positive for spores and with microscopic pathological changes in both exposure groups. Rainbow trout were the only species to show whirling behavior and blacktail. Atlantic salmon were less susceptible, with only 44 and 61% being positive for spores, respectively, in the low and high dose groups, while 68 and 75%, respectively, had microscopic pathology associated with cartilage damage. Rainbow trout heads contained mean spore concentrations of 2.2 (low dose) or 4.0 (high dose) x 10(6) spores g tissue(-1). The means for positive Atlantic salmon (not including zero values) were 1.7 (low) and 7.4 (high) x 10(4) spores g tissue(-1). Lake trout showed no clinical signs of infection, were negative for spores in both groups and showed no histopathological signs of M. cerebralis infection.

Analysis of Variance↗
PubMed1991

Comparison of rainbow trout and mammalian cytochrome P450 enzymes: evidence for structural similarity between trout P450 LMC5 and human P450IIIA4.

Studies were undertaken to determine the immunochemical relationship between constitutive trout cytochrome P450s and mammalian cytochrome P450IIIA enzymes. Polyclonal antibodies (IgG) generated against trout P450 LMC5 reacted strongly with P450IIIA1 in dexamethasone-induced rat liver microsomes and with P450IIIA4 in human liver microsomes in immunoblots. In contrast, rabbit anti-P450 LMC1 IgG did not recognize these proteins in rat and human liver microsomes. Reciprocal immunoblots using anti-rat P450IIIA1 showed that this antibody does not recognize trout P450 LMC1 or LMC5. However, anti-human P450IIIA4 IgG was found to cross react strongly with P450 LMC1 and LMC5. Progesterone 6 beta-hydroxylase activity of trout liver microsomes, a reaction catalyzed by P450 LMC5, was markedly inhibited by anti-P450IIIA4 and by gestodene, a mechanism-based inactivator of P450IIIA4. These results provide evidence for a close structural similarity between trout P450 LMC5 and human P450IIIA4.

Animals↗
PubMed1982

Response of rainbow trout (Salmo gairdneri) to increased levels of available carbohydrate in practical trout diets.

1. The physiological response of rainbow trout (Salmo gairdneri) reared on different levels of available carbohydrate in practical trout diets having the same levels of energy and nitrogen for 16-24 weeks was determined. 2. Weight gain was significantly reduced in trout reared on the highest level of available carbohydrate, 210 g cerelose (alpha-glucose) kg, and there was a significant linear regression (R2 0.88 of dietary carbohydrate on weight gain. 3. Liver: body-weight values and liver glycogen levels increased in relation to increased dietary carbohydrate. 4. Liver glucose-6-phosphate dehydrogenase (EC 1.1.1.49) activity increased and liver phosphoenolpyruvate carboxykinase (EC 4.1.1.32) activity decreased per kg body-weight of fish with increasing dietary carbohydrate. However, no significant effect was noted on the activity of these liver enzymes above a dietary cerelose level of 140 g/kg. 5. Liver fructose diphosphatase (EC 3.1.3.11) activity increased with increasing dietary carbohydrate has been interpreted as meaning a recycling of triosephosphate to glucose-6-phosphate. 6. Dietary carbohydrate level had no significant effect on the liver pyruvate kinase (EC 2.7.1.40) activity, the rate of glucose utilization or the percentage conversion of [14C]alanine to glucose in the plasma of trout. 7. The results indicate that rainbow trout have a limited ability to adapt to increased dietary carbohydrate and a level in excess of 140 g/kg of the diet is not efficiently utilized.

Alanine↗
PubMed2004

Comparative susceptibility of brown trout and rainbow trout to Discocotyle sagittata (Monogenea).

The susceptibility of brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) to the monogenean Discocotyle sagittata in the United Kingdom was assessed by experimental infection of naive fish. One month postinfection with 100 oncomiracidia/host, brown trout harbored significantly lower burdens (27.7 worms/host +/- 4.13 SE) than rainbow trout (47.8 worms/host +/- 3.90; P = 0.002). This indicates that the consistently lower prevalence and intensity of D. sagittata recorded in naturally infected farmed fishes reflects differences in susceptibility to the parasite. The outcome may be related to the comparatively short-term association of this parasite with rainbow trout (introduced to Britain in the 1880s) compared with the established native host-parasite association.

Animals↗