| 1. |
- Ebbesson, Lars O. E., et al.
(författare)
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Exposure to continuous light disrupts retinal innervation of the preoptic nucleus during parr-smolt transformation in Atlantic salmon
- 2007
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Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486 .- 1873-5622. ; 273:2-3, s. 345-349
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Konferensbidrag (refereegranskat)abstract
- High quality salmon smolts are essential for aquaculture, enhancement programs and wild populations. However, intensification of aquaculture smolt production and changes in natural habitats can cause sub-optimal environmental conditions, which may result in poor smolt quality. The salmon brain, as the integrator of environmental information, plays a focal role in relaying this information through the light-brain-pituitary axis, which includes retinal and pineal innervation of the hypothalamus. Here we investigated the effect of rearing juvenile Atlantic salmon, Salmo salar, under constant light (LL) on optic nerve fiber growth into the hypothalamus. This was compared with the normal increased fiber growth in fish reared under a simulated-natural photoperiod (LDN). Parr were sampled from the LDN group in February and from the LDN and LL groups in May (peak smolt status for the LDN group). Retinohypothalamic projections to the preoptic area were traced using 1, 1'-dioctadecyl-3,3, 3,3-tetramethylindocarbocyanine perchlorate (DiI) and confocal laser scanning microscopy. Data showed that parr exposed to LL did not develop the same extensive retinal innervation to the preoptic nucleus (NPO) observed in control salmon smolts raised under LDN. Since the cells in NPO are central pituitary regulatory neurones, the increased retinohypothalamic innervation during normal smoltification may be responsible for the increased endocrine response to photoperiod information. The deprivation of photoperiod information, during continuous light exposure, may inhibit the natural developmental program to proceed during the parr-smolt transformation. (C) 2007 Elsevier B.V. All rights reserved.
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| 2. |
- Nilsen, Tom O, et al.
(författare)
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Differential expression of gill Na+,K+-ATPase alpha- and beta-subunits, Na+,K+,2Cl- cotransporter and CFTR anion channel in juvenile anadromous and landlocked Atlantic salmon Salmo salar.
- 2007
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Ingår i: The Journal of experimental biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 210:Pt 16, s. 2885-96
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Tidskriftsartikel (refereegranskat)abstract
- This study examines changes in gill Na(+),K(+)-ATPase (NKA) alpha- and beta-subunit isoforms, Na(+),K(+),2Cl(-) cotransporter (NKCC) and cystic fibrosis transmembrane conductance regulator (CFTR I and II) in anadromous and landlocked strains of Atlantic salmon during parr-smolt transformation, and after seawater (SW) transfer in May/June. Gill NKA activity increased from February through April, May and June among both strains in freshwater (FW), with peak enzyme activity in the landlocked salmon being 50% below that of the anadromous fish in May and June. Gill NKA-alpha1b, -alpha3, -beta(1) and NKCC mRNA levels in anadromous salmon increased transiently, reaching peak levels in smolts in April/May, whereas no similar smolt-related upregulation of these transcripts occurred in juvenile landlocked salmon. Gill NKA-alpha1a mRNA decreased significantly in anadromous salmon from February through June, whereas alpha1a levels in landlocked salmon, after an initial decrease in April, remained significantly higher than those of the anadromous smolts in May and June. Following SW transfer, gill NKA-alpha1b and NKCC mRNA increased in both strains, whereas NKA-alpha1a decreased. Both strains exhibited a transient increase in gill NKA alpha-protein abundance, with peak levels in May. Gill alpha-protein abundance was lower in SW than corresponding FW values in June. Gill NKCC protein abundance increased transiently in anadromous fish, with peak levels in May, whereas a slight increase was observed in landlocked salmon in May, increasing to peak levels in June. Gill CFTR I mRNA levels increased significantly from February to April in both strains, followed by a slight, though not significant increase in May and June. CFTR I mRNA levels were significantly lower in landlocked than anadromous salmon in April/June. Gill CFTR II mRNA levels did not change significantly in either strain. Our findings demonstrates that differential expression of gill NKA-alpha1a, -alpha1b and -alpha3 isoforms may be important for potential functional differences in NKA, both during preparatory development and during salinity adjustments in salmon. Furthermore, landlocked salmon have lost some of the unique preparatory upregulation of gill NKA, NKCC and, to some extent, CFTR anion channel associated with the development of hypo-osmoregulatory ability in anadromous salmon.
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| 3. |
- Nilsen, Tom O, et al.
(författare)
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Endocrine systems in juvenile anadromous and landlocked Atlantic salmon (Salmo salar): seasonal development and seawater acclimation.
- 2008
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Ingår i: General and comparative endocrinology. - : Elsevier BV. - 0016-6480. ; 155:3, s. 762-72
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Tidskriftsartikel (refereegranskat)abstract
- The present study compares developmental changes in plasma levels of growth hormone (GH), insulin-like growth factor I (IGF-I) and cortisol, and mRNA levels of their receptors and the prolactin receptor (PRLR) in the gill of anadromous and landlocked Atlantic salmon during the spring parr-smolt transformation (smoltification) period and following four days and one month seawater (SW) acclimation. Plasma GH and gill GH receptor (GHR) mRNA levels increased continuously during the spring smoltification period in the anadromous, but not in landlocked salmon. There were no differences in plasma IGF-I levels between strains, or any increase during smoltification. Gill IGF-I and IGF-I receptor (IGF-IR) mRNA levels increased in anadromous salmon during smoltification, with no changes observed in landlocked fish. Gill PRLR mRNA levels remained stable in both strains during spring. Plasma cortisol levels in anadromous salmon increased 5-fold in May and June, but not in landlocked salmon. Gill glucocorticoid receptor (GR) mRNA levels were elevated in both strains at the time of peak smoltification in anadromous salmon, while mineralocorticoid receptor (MR) mRNA levels remained stable. Only anadromous salmon showed an increase of gill 11beta-hydroxysteroid dehydrogenase type-2 (11beta-HSD2) mRNA levels in May. GH and gill GHR mRNA levels increased in both strains following four days of SW exposure in mid-May, whereas only the anadromous salmon displayed elevated plasma GH and GHR mRNA after one month in SW. Plasma IGF-I increased after four days in SW in both strains, decreasing in both strains after one month in SW. Gill IGF-I mRNA levels were only increased in landlocked salmon after 4days in SW. Gill IGF-IR mRNA levels in SW did not differ from FW levels in either strain. Gill PRLR mRNA did not change after four days of SW exposure, and decreased in both strains after one month in SW. Plasma cortisol levels did not change following SW exposure in either strain. Gill GR, 11beta-HSD2 and MR mRNA levels increased after four days in SW in both strains, whereas only the anadromous strain maintained elevated gill GR and 11beta-HSD2 mRNA levels after one month in SW. The results indicate that hormones and receptors of the GH and cortisol axes are present at significantly lower levels during spring development and SW acclimation in landlocked relative to anadromous salmon. These findings suggest that attenuation of GH and cortisol axes may, at least partially, result in reduced preparatory upregulation of key gill ion-secretory proteins, possibly a result of reduced selection pressure for marine adaptations in landlocked salmon.
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| 4. |
- Ebbesson, Lars O.E., et al.
(författare)
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Free plasma thyroxine levels in coho salmon, Oncorhynchus kisutch, during parr-smolt transformation : Comparison with total thyroxine, total triiodothyronine, and growth hormone levels
- 2000
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Ingår i: Fish Physiology and Biochemistry. - 0920-1742. ; 22:1, s. 45-50
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Tidskriftsartikel (refereegranskat)abstract
- Free plasma thyroxine (FT4) levels were measured in coho salmon, Oncorhynchus kisutch, during parr-smolt transformation (smoltification) using an equilibrium dialysis system followed by a radioimmunoassay. The FT4 data were correlated to total plasma thyroxine (TT4), triiodothyronine (TT3), and growth hormone (GH). Plasma samples were taken weekly from early April to late May, when the salmon where released from the hatchery. Free thyroxine and GH levels increased gradually through smoltification. TT4 levels increased significantly in mid-April and in mid-May. TT3 levels increased in April and remained elevated until late-May after which they declined to the lowest levels. During the first increase in TT4 levels, FT4 levels remained low and TT3 levels did not increase until FT4 levels increased in late-April. In addition, after TT4 levels decreased in late May, FT4 levels remained elevated. These data show that there are differences between the plasma FT4 and TT4 profiles during smoltification. Nevertheless, regression analysis indicates that FT4 levels are highly correlated to the increases in the levels of GH (r=0.73) and TT4 (r=0.70). In addition, GH is less correlated to TT4 and TT3 (r = 0.24 and r = -0.46, respectively) compared with FT4 (r = 0.73), suggesting a close relationship between the increases of FT4 and GH. In addition, these data suggest that this method of measuring free plasma thyroxine may provide a new tool for studying the timing of thyroid hormone action and regulation during parr-smolt transformation in salmonids.
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| 5. |
- Ebbesson, Lars, et al.
(författare)
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Daily endocrine profiles in parr and smolt Atlantic salmon.
- 2008
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Ingår i: Comparative Biochemistry and Physiology A. - : Elsevier BV. - 1531-4332 .- 1095-6433. ; 151, s. 698-704
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Tidskriftsartikel (refereegranskat)abstract
- To elucidate possible mechanisms behind the endocrine control of parr-smolt transformation, the daily plasma profiles in thyroid hormones (TH; free thyroxine (FT(4)), total thyroxine (TT(4)), and total 3,5,3'-triiodothyronine (TT(3))), growth hormone (GH) and cortisol were studied in Atlantic salmon parr and smolts under simulated-natural winter (8 L:16D) and spring (16.5 L:7.5D) photoperiods, respectively. Overall, TT(4), TT(3) and GH levels were higher in smolts than in parr, whereas FT(4) levels fluctuated within the same range in parr and smolts. Significant diurnal changes in plasma TH were present in parr. Both FT(4) and TT(4) levels increased during the photophase and decreased during the scotophase, while TT(3) levels followed an inverse pattern. Growth hormone showed no significant changes in parr. Changes in FT(4), TT(4), GH, and cortisol, but not TT(3), levels, were observed in smolts with peak levels during both the photophase and scotophase for FT(4), TT(4) and GH. Plasma cortisol was not assayed in parr but in smolts the peaks were associated with dusk and dawn. In addition to the general increases in TH, GH and cortisol, the distinct endocrine differences in nighttime levels between parr in the winter and smolts in the spring suggest different interactions between TH, GH, cortisol and melatonin at these different time points. These spring scotophase endocrine profiles may represent synergistic hormone interactions that promote smolt development, similar to the synergistic endocrine interactions shown to accelerate anuran metamorphosis. The variations in these diurnal rhythms between parr and smolts may represent part of the endocrine mechanism for the translation of seasonal information during salmon smoltification.
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| 6. |
- Kling, Peter, 1968, et al.
(författare)
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A homologous salmonid leptin radioimmunoassay indicates elevated plasma leptin levels during fasting of rainbow trout
- 2009
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Ingår i: General and Comparative Endocrinology. ; 162:3, s. 307-312
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Tidskriftsartikel (refereegranskat)abstract
- The present study was conducted to establish a homologous radioimmunoassay (RIA) for quantifying plasma leptin (Lep) levels in salmonid species, and to study Lep levels in relation to nutritional status. A part of the Lep peptide, a 14 amino acid long sequence, identical between a Salmo and an Oncorhynchus species was synthesised. Polyclonal antibodies were raised in rabbit against this antigen and both were subsequently used in the development of a RIA protocol for assessing plasma Lep levels. The limit of detection of the assay was 0.3 nM, and intra- and interassay coefficient of variation (CV) were 8.4% and 13%, respectively. Apart from Atlantic salmon and rainbow trout, the assay exhibits measuring parallelism for a range of fish species, including arctic char, Atlantic cod and turbot, suggesting that the established RIA is useful for quantifying Lep levels in several fish species. The RIA indicates that Lep is found in salmonid plasma at levels of 0.5–5 nM, which is comparable with other peptide hormones, and well within the measuring range of the RIA. A study of fed and fasted rainbow trout showed elevated plasma Lep levels during fasting. In addition there was no correlation between Lep levels and condition factor. These data suggest that the relation between circulating Lep levels and energy status differs from that in mammals. While Lep is linked to energy balance, it may not act as an adiposity signal in salmonids, possibly pointing to functional divergence among ectothermic and endothermic vertebrates.
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| 7. |
- Kling, Peter, 1968, et al.
(författare)
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The role of GH in lipid homeostasis, energy utilization and partitioning in rainbow trout: interactions with ghrelin, leptin and insulin-like growth factor I
- 2012
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Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 175:1, s. 153-162
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Tidskriftsartikel (refereegranskat)abstract
- The growth-promoting effects of in vivo growth hormone (GH) treatment were studied in relation to size and lipid content of energy stores including liver, mesentery, white muscle and belly flap in rainbow trout. In order to elucidate endocrine interactions and links to regulation of growth, adiposity and energy metabolism, plasma levels of GH, insulin-like growth factor I (IGF-I), leptin (Lep) and ghrelin, were assessed and correlated to growth and energy status. In addition tissue-specific expression of lepa1 mRNA was examined. Juvenile rainbow trout were implanted with sustained-release bovine GH implants and terminally sub-sampled at 1, 3 and 6 weeks. GH increased specific growth rate, reduced condition factor (CF) and increased feed conversion efficiency resulting in a redistribution of energy stores. Thus, GH decreased mesenteric (MSI) and liver somatic index (LSI). Lipid content of the belly flap increased following GH-treatment while liver and muscle lipid content decreased. Independent of GH substantial growth was accompanied by an increase in muscle lipids and a decrease in belly flap lipids. The data suggest that the belly flap may function as an energy buffering tissue during episodes of feeding and lean growth. Liver and muscle lipids were positively correlated to body weight, indicating a size-dependent change in adiposity. Hepatic lepa1 mRNA positively correlated to MSI and CF and its expression decreased following GH treatment, coinciding with decreased hepatic lipid content. Plasma Lep was positively correlated to MSI and belly flap lipid content, suggesting that Lep may communicate energy status. In summary, the observed GH tissue-specific effects on lipid metabolism in rainbow trout highlight the complex physiology of the energy reserves and their endocrine control.
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| 8. |
- Ronnestad, Ivar, et al.
(författare)
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Leptin and leptin receptor genes in Atlantic salmon: Cloning, phylogeny, tissue distribution and expression correlated to long-term feeding status
- 2010
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Ingår i: GENERAL AND COMPARATIVE ENDOCRINOLOGY. - 0016-6480. ; 168:1, s. 55-70
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Tidskriftsartikel (refereegranskat)abstract
- The present study reports the complete coding sequences for two paralogues for leptin (sLepA1 and sLepA2) and leptin receptor (sLepR) in Atlantic salmon. The deduced 171-amino acid (aa) sequence of sLepA1 and 175 aa sequence for sLepA2 shows 71.6% identity to each other and clusters phylogenetically with teleost Lep type A, with 22.4% and 24.1% identity to human Lep. Both sLep proteins are predicted to consist of four helixes showing strong conservation of tertiary structure with other vertebrates. The highest mRNA levels for sLepA1 in fed fish (satiation ration = 100%) were observed in the brain, white muscle, liver, and ovaries. In most tissues sLepA2 generally had a lower expression than sLepA1 except for the gastrointestinal tract (stomach and mid-gut) and kidney. Only one leptin receptor ortholog was identified and it shares 24.2% aa sequence similarity with human LepR, with stretches of highest sequence similarity corresponding to domains considered important for LepR signaling. The sLepR was abundantly expressed in the ovary, and was also high in the brain, pituitary, eye, gill, skin, visceral adipose tissue, belly flap, red muscle, kidney, and testis. Fish reared on a rationed feeding regime (60% of satiation) for 10 months grew less than control (100%) and tended to have a lower sLepA1 mRNA expression in the fat-depositing tissues visceral adipose tissue (p < 0.05) and white muscle (n.s.). sLepA2 mRNA levels was very low in these tissues and feeding regime tended to affect its expression in an opposite manner. Expression in liver differed from that of the other tissues with a higher sLepA2 mRNA in the feed-rationed group (p < 0.01). Plasma levels of sLep did not differ between fish fed restricted and full feeding regimes. No difference in brain sLepR mRNA levels was observed between fish fed reduced and full feeding regimes. This study in part supports that sLepA1 is involved in signaling the energy status in fat-depositing tissues in line with the mammalian model, whereas sLepA2 may possibly play important roles in the digestive tract and liver. At present, data on Lep in teleosts are too scarce to allow generalization about how the Lep system is influenced by tissue-specific energy status and, in turn, may regulate functions related to feed intake, growth, and adiposity in fish. In tetraploid species like Atlantic salmon, different Lep paralogues seems to serve different physiological roles.
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