| 1. |
- Nilsen, Tom Ole, et al.
(författare)
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EFFECTS OF ANDROGENS AND CORTISOL ON GILL ION TRANSPORTERS AND OMSMOREGULATORY CAPACITY IN ATLANTIC SALMON (SALMO SALAR)
- 2014
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Ingår i: ICBF 2014, Edinburgh.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Sex steroids have been reported to compromise ion homeostasis in teleosts, yet there is limited and somewhat contradicting knowledge about the mechanisms through which androgens impact osmoregulatory capacity in salmonids. Immature Atlantic salmon post-smolts in seawater (SW) were injected with 11-ketoandrostenedione (OA; 25 µg/g BW), cortisol (F; 25 µg/g BW), F+OA (25 µg/g BW) and sham control (CON). After 8 days treatment, androgen treated fishdemonstrated a striking transcriptional increase in freshwater (FW)-type of ion transporters (NKA α1a ) , concurrent with no apparent ion perturbations, or down regulation of SW gill ion-transporters (NKA α1b). F treated post-smolts displayed increased gill NKA α1a transcription, with an additive effect of F+OA.. Moreover, F also resulted in decreased transcription of NKA α1b whilst fish treated with combinations of F and OA experienced severe ion perturbations and mortalities in SW, while no mortality occurred when only F was administered. Our findings suggests that androgens have, either directly or indirectly, a role in remodelling the gill epithelia for FW entry, rather than leading to osmoregulatory dysfunction in SW acclimated post-smolts. Moreover, maturing post-smolts may be sensitive to stress since combinations of elevated androgens and cortisol levels may have detrimental effects on homeostasis and fish welfare.
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| 2. |
- 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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| 3. |
- Sundh, Henrik, 1976, et al.
(författare)
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NUTRIENT ABSORPTION IN THE ATLANTIC SALMON (SALMO SALAR L.) INTESTINE IS AFFECTED BY ENVIRONMENTAL SALINITY
- 2014
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Ingår i: ICBF 2014, Edinburgh.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Na+/K+-ATPases (NKA) located in the basolateral membrane of the intestinal absorptive cells (enterocytes) are the main driving force for both ion-coupled intestinal fluid transport and nutrient absorption in Atlantic salmon in seawater. It is hypothesized that a decreased need for osmoregulation in brackish water may be beneficial for the nutrient uptake and thereby the growth of the fish. Atlantic salmon post-smolts were acclimated to freshwater (FW), 12, 22 and 34 ppt seawater (SW) for several months. The intestinal nutrient transport (L-lysine and D-glucose) was measured in Ussing chambers and separate fish were used for intestinal mRNA expression of selected ion and nutrient transporters. No differences were found in mRNA levels of the NKA-α1c, NKCC2 co-transporter or SGLT-1 in relation to salinity, whereas the specific high-affinity low capacity Na+-coupled nutrient transport was significantly higher in FW and 22 ppt as compared to the 34 ppt group. The results suggest an allocation of the electrochemical gradient towards ion driven fluid transport in full strength SW.
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