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1.	Ebbesson, Lars, et al. (författare) Daily endocrine profiles in parr and smolt Atlantic salmon. 2008 Ingår i: Comparative Biochemistry and Physiology A. - : Elsevier BV. - 1531-4332 .- 1095-6433. ; 151, s. 698-704 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.
2.	Aksnes, A, et al. (författare) Size-fractionated fish hydrolysate as feed ingredient for rainbow trout (Oncorhynchus mykiss) fed high plant protein diets. I: Growth, growth regulation and feed utilization 2006 Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486. ; 261:1, s. 305-317 Tidskriftsartikel (refereegranskat)abstract Six experimental diets were fed to rainbow trout to examine the effect of fish hydrolysate and ultra filtered fish hydrolysate on growth performance, feed utilization and growth regulation using diets low in dietary fish meal inclusion. One diet contained a high level of plant protein sources (90.6% of total dietary protein) and a low level of fish meal (9.4% of dietary protein). Two diets contained different levels of hydrolysate in exchange for the plant protein sources, reducing the plant protein level to 73.9% and 57.2%, respectively. Two further diets were identical in composition except that the hydrolysate was ultra filtered to remove low molecular weight compounds. A moderate level of fish meal was used in the sixth diet which had a dietary plant protein level of 57.0%. All diets were made equal in protein, lipid, energy and lysine. The feeding trial lasted for 90 days and for the fastest growing group, fed moderate level of fish meal, the fish increased in weight from 149 g at start to a final weight of 443 g. All groups showed significant differences in growth and feed utilizations. Specific growth rates were; 0.30% day− 1 for the plant protein diet, 0.98% day− 1 for the high hydrolysate diet, 0.72% day− 1 for the group containing the high level of ultra filtered hydrolysate, and 1.21% day− 1 for the moderate fish meal diet. Feed efficiencies (g fish weight gain per g feed intake) were found to be 0.57 for plant protein diet, 0.97 for high level of hydrolysate, 0.83 for ultra filtered hydrolysate and 1.03 for the moderate fish meal diet. Half dietary inclusions of hydrolysate and ultra filtered hydrolysate revealed values between the plant protein diets and high levels of these ingredients, respectively. Feed consumption in percentage of average fish weight per day, correlated with the feed efficiency for all groups. PER, PPV and BV correlated with the differences in growth. Protein digestibilities were equal for all groups, while the moderate fish meal diet showed higher lipid and energy digestibilities than the plant protein diets. Although some of the differences may be due to growth inhibitors in plant resources other explanations may be relevant. Plasma growth hormone (GH) levels were significantly higher in fish fed the plant protein diet than fish fed the fish meal or high hydrolysate diet, which is most likely a result of their poor feeding status. Plasma IGF-I levels were not affected by diet. Comparisons of groups with similar inclusion of plant ingredients, and thus equal level of growth inhibitors, show that in removing small molecular weight compounds from fish hydrolysate, the growth and feed efficiency were significantly reduced. Some of these small compounds in fish hydrolysate thus seem to be essential for biological performance. Further, as fish meal revealed the best performance, fish muscle protein is not the only nutrient that makes fish meal an essential ingredient in aqua feed for carnivorous fish. This information is important in the work to find replacement of fish meal in a sustainable growing global aquaculture industry.
3.	Albertsson, Eva, 1979, et al. (författare) Marin fiskodling på den svenska västkusten: Biologiska förutsättningar : Rapport nummer 1 från Vattenbrukscentrum Väst, Göteborgs universitet 2013 Rapport (övrigt vetenskapligt/konstnärligt)abstract I den av regeringen beställda utredningen ”Det växande Vattenbrukslandet” föreslås att ”Göteborgs universitet (GU) tillförs resurser för att fortsätta att utveckla vattenbruksrelaterad forskning när det gäller musslor, ostron och marina fiskarter”. Därför tog under 2011 företrädare inom den odlingsrelaterade fiskforskningen vid Gö- teborgs universitet initiativet till denna studie om förutsättningarna för marin fiskodling. Studien har syftet att utreda de odlingsbiologiska förutsättningarna för etablering av vattenbruk av marina fiskarter på den svenska västkusten. Målet är att den ska kunna användas som kunskapsunderlag för en framtida handlingsplan för fiskodling på västkusten, och främja kunskapsutbytet mellan den fiskodlingsrelaterade forskningen, beslutsfat- tande organ och privata entreprenörer för att utveckla konkurrenskraftiga innovationer inom vattenbruket. En central fråga för sammanhanget är vilka fiskarter det finns potential för att odla på den svenska västkusten. Vattenbruket måste vara ekonomiskt bärkraftigt och en urvalsmodell baserad på svenska marina fiskarters kg- pris i förhållande till en minsta tänkbara produktionskostnad användes därför i denna studie. Vidare bedöm- des arterna utifrån kunskapsläge och odlingspotential. Arterna hälleflundra, tunga, piggvar, havskatt (vanlig och fläckig) samt lyrtorsk och torsk bedömdes att vara ”kandidatarter” för framtida odling i Sverige. För dessa arter gjordes omfattande studier för att vidare utreda behov och möjligheter. Det gjordes även en analys av de abiotiska faktorerna (vattentemperatur, syrgas- och salthalt) på den svenska västkusten. I en sista del av studien kombinerades kunskapen om kandidatarternas biologiska förutsättningar med västkustens abiotiska faktorer. De abiotiska förhållandena på den svenska västkusten är inte odlingsbiologiskt optimala för traditionell nät- kasseodling för någon av de framtagna kandidatarterna, då för höga sommartemperaturer skapar problem för kallvattensarterna medan varmvattensarterna hämmas av de låga vintertemperaturerna. En av de huvudsak- liga slutsatserna i denna rapport är därför att året-runt-bedriven fiskodling i öppna system, såsom i kustnära nätkassar, knappast är praktiskt genomförbart på den svenska västkusten för de arter som i denna studie i övrigt ansågs ha hög odlingspotential. För etablering av framgångsrika odlingssystem behövs speciella tekniska lösningar, som möjliggör reglering av abiotiska faktorer såsom syrgashalter och temperatur. För att Sverige skall kunna bli ett växande vattenbruksland krävs samordnade insatser mellan forskare från flera discipliner, privata aktörer och andra intressenter. Dessutom krävs satsningar på forskning och utredning av de mera tekniskt avancerade odlingssystem som den svenska västkusten kommer behöva. Med tanke på miljöbelastningsproblematiken kring öppna havsbaserade system för fiskodling samt de abiotiska faktorerna längs västkusten som inte är optimala för någon av kandidatarterna i utredningen, så är slutsatsen att man bör undersöka, alternativa odlingssystem till traditionella öppna nätkassar för fiskodling, där man kan kontrollera faktorer som temperatur, salthalt och syrenivåer och minimera utsläppen. Nästa steg som föreslås är att göra en teknisk/ekonomisk utredning kring hållbara havs- eller landbaserade system för marin fiskodling. Utred- ningen bör innehålla fall-studier för en eller två fiskarter och ett kräftdjur och inkludera en myndighetspröv- ning för de framtagna koncepten. Ytterligare en förutsättning för att vattenbruket skall kunna utvecklas är satsningar på nödvändig infrastruktur, som ett marint kläckeri för forskning och utvecklingsarbete.
4.	Arnason, T., et al. (författare) Effects of salinity and temperature on growth, plasma ions, cortisol and immune parameters of juvenile Atlantic cod (Gadus morhua) 2013 Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486. ; 380-383, s. 70-79 Tidskriftsartikel (refereegranskat)abstract The effects of salinity and temperature on growth, plasma ions, cortisol and immune parameters were investigated in two experiments. In the first experiment small, medium and large juvenile Atlantic cod Gadus morhua (initial average weights of 1.9, 8 and 83 g, respectively) were reared at four constant salinities (6 to 32 parts per thousand) for a short period (19-57 days, depending on size), then returned to seawater (32 parts per thousand) without acclimation and reared for another period (20-391 days). The highest growth rates were found at 10 parts per thousand in all size-classes. After the fish were returned to seawater the growth rates were inversely related to the salinity change in all size-classes and long-term rearing of the medium-sized fish revealed that abrupt salinity increase from 6 and 10 parts per thousand to seawater may permanently reduce the growth capacity of juvenile cod. In another long-term experiment, there was no significant difference in the growth rate of cod (initial average weight 3.4 g) reared at either 13.5 or 32 parts per thousand for 187 days. Rearing at 13.5 parts per thousand neither enhanced growth rate at 6.3 degrees C nor at 10 degrees C in larger juveniles (>245 g) compared with rearing in seawater. The study shows that rearing salinity and abrupt salinity changes have limited or no effects on stress and immune-related parameters, and there are no indications of ion regulatory disturbances at salinities as low as 6 parts per thousand. This shows that the Atlantic cod is an extremely euryhaline marine teleost species, and indicates that commercial Atlantic cod aquaculture can just as well be carried out in locations with low as with high environmental salinity. (C) 2012 Published by Elsevier B.V.
5.	Arnason, T., et al. (författare) Impact of temperature and growth hormone on growth physiology of juvenile Atlantic wolffish (Anarhichas lupus) 2019 Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486. ; 504, s. 404-413 Tidskriftsartikel (refereegranskat)abstract The effects of temperature and growth hormone (GH) implantation on growth of juvenile Atlantic wolffish (Anarhichas lupus) were investigated. The year-long study had three sequential experimental phases (EP) termed EP1, EP2 and EP3, lasting for 6, 9 and 37 weeks, respectively. The experimental fish were divided into four groups and reared at different target temperatures (3, 7, 11 and 15 degrees C) during EP1 and EP2, but at a constant temperature of 7 degrees C during EP3. At the beginning of EP2, half of the fish from each group was implanted with formulation of recombinant bovine GH (Posilac (R)), while the other half was sham-implanted with vehicle. The optimal temperature for growth (T-opt.G) of early juveniles (geometric mean weight 7.5 g) was determined as 12.1 degrees C during EP1, while the upper critical temperature (Tc) was concluded to be very close to 15 degrees C, as fish at that temperature had stunted growth, increased mortality and showed external signs of skeletal deformities. Thus, the species was found to be relatively stenothermic during the early juvenile stages and therefore vulnerable to relatively modest increases in environmental temperature above T-opt.G At 15 degrees C, GH implantation had no effects on growth rate. This indicates that the high allostatic load at this temperature leaves no scope for increased growth. In contrast, at lower rearing temperatures, the GH implantation had substantial, long-term effects on growth rate and induced remarkably similar relative growth stimulation at 3, 7 and 11 degrees C, suggesting a temperature-independent mechanism for the growth-promoting effects of GH.
6.	Arnason, T., et al. (författare) Long-term rearing of Arctic charr Salvelinus alpinus under different salinity regimes at constant temperature 2014 Ingår i: Journal of Fish Biology. - : Wiley. - 0022-1112. ; 85:4, s. 1145-1162 Tidskriftsartikel (refereegranskat)abstract Arctic charr Salvelinus alpinus of the Holar strain (mean+/- s. e. body mass= 152.1+/-3.1g) were reared at four different salinity regimes at a constant temperature of 7.4 degrees C. Two groups were given a three-month acclimation in salinity 18 before the salinity was increased to either 25 or 29 (groups called A25 and A29), and two groups were reared in salinities 25 or 29 over the full experimental period of 409 days (groups called F25 and F29). In the first 3months, the A25 and A29 groups had the highest growth rates. By October 2011, there were no significant differences (two-way nested ANOVA, P> 0.05) in the mean body masses among A25, F25 and F29 (c. 1450 g), whereas A29 had a lower mean mass (1282 g). The growth in the last period from October 2011 to January 2012 was reduced by sexual maturation in the highest salinity regimes (A29 and F29), whereas fish in groups A25 and F25 showed high growth throughout the study. Males in all salinity groups had higher growth rates than females for the most part of the study, but the divergence between the sexes was most pronounced in the highest salinity regimes. All salinity groups showed distinct changes in Na+, K+-ATPase activity, with high activity in spring and summer, and lower activity in the autumn. Plasma sodium (Na+) levels were stable indicating that none of the experimental groups had problems in maintaining hydromineral balance during the study. While plasma leptin levels were not affected by salinity regimes, it was noted that these levels were 13-30% higher in fish with empty guts compared with those having food in their gut at the time of sampling. This suggests a link between leptin levels and food intake, indicating that this hormone may play a role in food intake and energy allocation in fishes.
7.	Benedet Perea, Susana, 1972, et al. (författare) Cloning of somatolactin alpha, beta forms and the somatolactin receptor in Atlantic salmon: Seasonal expression profile in pituitary and ovary of maturing female broodstock 2008 Ingår i: Reproductive Biology and Endocrinology. - : Springer Science and Business Media LLC. - 1477-7827. ; 6:42 Tidskriftsartikel (refereegranskat)abstract Background Somatolactin (Sl) is a fish specific adenohypophyseal peptide hormone related to growth hormone (Gh). Some species, including salmonids, possess two forms: Sl alpha and Sl beta. The somatolactin receptor (slr) is closely related to the growth hormone receptor (ghr). Sl has been ascribed many physiological functions, including a role in sexual maturation. In order to clarify the role of Sl in the sexual maturation of female Atlantic salmon (Salmo salar), the full length cDNAs of slr, Sl alpha and Sl beta were cloned and their expression was studied throughout a seasonal reproductive cycle using real-time quantitative PCR (RTqPCR). Methods Atlantic salmon Sl alpha, Sl beta and slr cDNAs were cloned using a PCR approach. Gene expression of Sl alpha, SL beta and slr was studied using RTqPCR over a 17 month period encompassing pre-vitellogenesis, vitellogenesis, ovulation and post ovulation in salmon females. Histological examination of ovarian samples allowed for the classification according to the degree of follicle maturation into oil drop, primary, secondary or tertiary yolk stage. Results The mature peptide sequences of Sl alpha, Sl beta and slr are highly similar to previously cloned salmonid forms and contained the typical motifs. Phylogenetic analysis of Atlantic salmon Sl alpha and Sl beta shows that these peptides group into the two Sl clades present in some fish species. The Atlantic salmon slr grouped with salmonid slr amongst so-called type I ghr. An increase in pituitary Sl alpha and Sl beta transcripts before and during spawning, with a decrease post-ovulation, and a constant expression level of ovarian slr were observed. There was also a transient increase in Sl alpha and Sl beta in May prior to transfer from seawater to fresh water and ensuing fasting. Conclusion The up-regulation of Sl alpha and Sl beta during vitellogenesis and spawning, with a subsequent decrease post-ovulation, supports a role for Sl during gonadal growth and spawning. Sl could also be involved in calcium/phosphate mobilization associated with vitellogenesis or have a role in energy homeostasis associated with lipolysis during fasting. The up-regulation of both Sl alpha and Sl beta prior to fasting and freshwater transfer, suggests a role for Sl linked to reproduction that may be independent of the maturation induced fasting.
8.	Benedet Perea, Susana, 1972, et al. (författare) Cloning of two Atlantic salmon growth hormone receptor isoforms and in vitro ligand-binding response. 2006 Ingår i: Fish Physiology and Biochemistry. - : Springer Science and Business Media LLC. - 0920-1742 .- 1573-5168. ; 31:4, s. 315-329 Tidskriftsartikel (refereegranskat)abstract Two isoforms of the full-length cDNA of the growth hormone receptor (GHR) of the Atlantic salmon (Salmo salar; ss) were cloned by a PCR approach using RACE. Respectively, the cDNA sequences of ssGHR isoforms 1 and 2 are 2654 and 2608 nucleotides long, with 1782 and 1773 nucleotide ORFs. The resulting coded proteins are 594 and 590 aa long, with 19 and 20 aa signal peptides. The two isoforms share 86% protein and 87% cDNA sequence similarity. Isoform 1 is most similar to other salmonid GHR isoforms 1 while isoform 2 is most similar to salmonid GHR isoforms 2 (93–95%). Similarity with other teleost species was lower (37–44%). The bioactivity of the cloned ssGHR was tested by transfecting the ssGHR isoform 1 cDNA into CHO-K1 hamster cells, incubating with recombinant salmon GH (sGH) or native ovine prolactin (oPRL), and measuring cell proliferation by the MTT assay. The ssGHR-transfected cells significantly increased proliferation when stimulated by sGH at all concentrations. oPRL stimulated ssGHR-transfected cells at higher concentrations due to receptor cross reaction. ssGHR isoforms 1 and 2 contain a single transmembrane domain and the typical conserved motifs found in other teleost GHRs, including four paired cysteine residues and five potential N-glycosylation sites in the extracellular domain, Box I and Box II, as well as seven potential tyrosine phosphorylation sites in the intracellular domain. However, in salmonids, these motifs differ from those of other teleosts, and could be responsible for differentiated hormone binding, signal transduction and response.
9.	Benedet Perea, Susana, 1972, et al. (författare) Pituitary and plasma growth hormone dynamics during sexual maturation of female Atlantic salmon 2010 Ingår i: GENERAL AND COMPARATIVE ENDOCRINOLOGY. - 0016-6480. ; 167:1, s. 77-85 Tidskriftsartikel (refereegranskat)abstract Growth hormone in fish regulates many important physiological processes including growth, metabolism and potentially reproduction. In salmonid fish, GH secretion is episodic with irregularly spaced GH peaks. Plasma GH reflects secretion episodes as well as the clearance rate of the hormone, and plasma levels may thus not always reflect the level of activation of the GH axis. This study measured the production dynamics of GH over a 17-month period in sexually maturing female Atlantic salmon which included final maturation and spawning. For the first time, the level of pituitary GH mRNA, pituitary GH protein and plasma GH protein were analyzed concurrently in the same individuals. mRNA and protein were extracted in parallel from the same samples with subsequent real time quantitative PCR to measure mRNA transcripts and radioimmunoassay to measure pituitary and plasma GH protein. Further, the effects of photoperiod manipulation on these parameters were studied. The results show no correlation between mRNA and protein levels except at some time points, and indicate that it is inappropriate to correlate pooled temporal data and averages in time series unless the relationship among the variables is stable over time. The results indicate complex and shifting relationships between pituitary GH mRNA expression, pituitary GH content and plasma GH levels, which could result from changes in clearance rather than secretion rate at different times and its episodic secretion. The study also suggests that there is a functionally important activation of the GH system during spring leading up to maturation and spawning.
10.	Björnsson, Björn Thrandur, 1952, et al. (författare) Arrested Development: The Molecular and Endocrine Basis of Flatfish Metamorphosis (ARRDE) 2006 Rapport (övrigt vetenskapligt/konstnärligt)
11.	Björnsson, Björn Thrandur, 1952, et al. (författare) Endocrine control and tailor-made seafood 2006 Ingår i: Aqua 2006, Florence, 9-13 May. Konferensbidrag (övrigt vetenskapligt/konstnärligt)
12.	Björnsson, Björn Thrandur, 1952, et al. (författare) Environmental endocrinology of salmon smoltification 2011 Ingår i: GENERAL AND COMPARATIVE ENDOCRINOLOGY. - 0016-6480. ; 170:2, s. 290-298 Tidskriftsartikel (refereegranskat)
13.	Björnsson, Björn Thrandur, 1952, et al. (författare) Fiskars odlingsbiologi- svenska framtidsperspektiv 2013 Ingår i: Formas fokuserar. ; 21, s. 257-269 Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
14.	Björnsson, Björn Thrandur, 1952, et al. (författare) Gastrointestinal functions and food intake regulation in salmonids: impact of dietary lipids 2002 Rapport (övrigt vetenskapligt/konstnärligt)abstract GUTINTEGRITY, Q5RT-2000-31656, Annual progress report for the first reporting period: 2001-01-01 – 2001-12-31
15.	Björnsson, Björn Thrandur, 1952, et al. (författare) Gastrointestinal functions and food intake regulation in salmonids: impact of dietary lipids 2003 Rapport (övrigt vetenskapligt/konstnärligt)abstract GUTINTEGRITY Q5RT-2000-31656 Annual progress report for the second reporting period: 2002-01-01 – 2002-12-31
16.	Björnsson, Björn Thrandur, 1952, et al. (författare) Gastrointestinal functions and food intake regulation in salmonids: impact of dietary lipids. 2004 Rapport (övrigt vetenskapligt/konstnärligt)abstract Final report for the EC-project. GUTINTEGRITY Q5RT-2000-31656
17.	Björnsson, Björn Thrandur, 1952, et al. (författare) Gastrointestinal functions and food intake regulation in salmonids: impact of dietary lipids. 2004 Rapport (övrigt vetenskapligt/konstnärligt)abstract GUTINTEGRITY Q5RT-2000-31656 Annual progress report for the third reporting period: 2003-01-01 – 2004-03-31
18.	Björnsson, Björn Thrandur, 1952, et al. (författare) Growth hormone endocrinology of salmonids: regulatory mechanisms and mode of action 2002 Ingår i: FISH PHYSIOLOGY AND BIOCHEMISTRY. - 0920-1742. ; 27:3-4, s. 227-242 Tidskriftsartikel (refereegranskat)abstract The focus of this review is on the regulatory mechanisms and the mode of action of GH in salmonids. To stimulate further research, it aims at highlighting areas where numerous important breakthroughs have recently been made, as well as where data are currently lacking. The regulation of GH secretion is under complex hypothalamic control, as well as under negative feedback control by GH and IGF-I. Further, the recently characterized ghrelin is a potent GH secretagogue, and may prove to be a link between feed intake and growth regulation. GH plasma profiles show indications of diurnal changes, but whether salmonids have true pulsatile GH secretion remains to be elucidated. The recent cloning and characterization of the salmon GH receptor (GHR) is a major research break-through which will give new insights into the mechanisms of GH action. It should also stimulate research into circulating GH-binding proteins (GHBPs), as they appear to be a soluble form of the GHR. The salmonid GHR sequences show evolutionary divergence from other fish species, but with a high degree of identity within the salmonid group. Radioreceptorassay studies have found GHR present in all tissues examined, which is in line with the highly pleiotropic action of GH. Data are currently scarce on the plasma dynamics of GH in salmonids, and further studies on GHR and GHBPs dynamics coupled to assessments of GH clearance rates and pathways are needed. The direct versus indirect nature of GH action remains to be clarified, but GH appears to act both locally at the target tissue level to stimulate the autocrine/paracrine action of IGF-I, as well as on the liver to increase plasma IGF-I levels. In addition, GH interacts with other hormones such as cortisol, thyroid hormones, insulin, and reproductive hormones, generating a wide range of physiological effects. GH may act both peripherally and directly at the level of the central nervous system to modify behavior, probably by altering the dopaminergic activity in the brain.
19.	Björnsson, Björn Thrandur, 1952, et al. (författare) Is salmon smoltification an example of vertebrate metamorphosis? Lessons learnt from work on flatfish larval development 2012 Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486. ; 362-363, s. 264-272 Tidskriftsartikel (refereegranskat)abstract The terms metamorphosis and smoltification both describe developmental processes. However, the question on what specific criteria define these terms continues to engage scientists. At the same time, various views have been expressed on whether or not smoltification of anadromous salmonids should be regarded as an example of vertebrate metamorphosis. This short overview tries to summarize some of these discussions and starts by determining if smoltification meets any of the criteria used to define metamorphosis. In particular, it broadly compares the process of flatfish metamorphosis with that of salmonid smoltification from a morphological, endocrine, molecular and behavioral perspective. Tools and approaches developed and used in metamorphosis research which could be useful in continued work on smoltification are highlighted. (c) 2011 Elsevier B.V. All rights reserved.
20.	Björnsson, Björn Thrandur, 1952, et al. (författare) Past successes, present misconceptions and future milestones in salmon smoltification research 2007 Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486. ; 273:2-3, s. 384-391 Tidskriftsartikel (refereegranskat)abstract Although the parr–smolt transformation of salmonids has been investigated for some fifty years, an array of specific aspects of the process remains unclear. At the 7th International Workshop on Salmon Smoltification convened in Tono, Japan, there was a consensus for the need for a review of the most pertinent findings on smoltification over the years and a discussion of what the future holds. We present here a three-part summary based to a large extent on the presentations and lively discussions which took place at the Workshop. The first part outlines some of the impressive successes this research has fostered. The second part deals with some current misconceptions, often based on over-interpretation of data and/or the lack of data. Finally, a discussion of future targets and aims and their applications is presented.
21.	Björnsson, Björn Thrandur, 1952, et al. (författare) Photoperiod regulation of plasma growth hormone levels during induced smoltification of underyearling Atlantic salmon. 2000 Ingår i: General and comparative endocrinology. - : Elsevier BV. - 0016-6480. ; 119:1, s. 17-25 Tidskriftsartikel (refereegranskat)abstract Earlier studies have established that increased daylength increases plasma growth hormone (GH) levels during spring smoltification of yearling Atlantic salmon. Recently, the Atlantic salmon aquaculture industry has started the production of underyearling ("summer") smolts. This involves fast juvenile growth on continuous light (24L), the transfer of juveniles over 8 cm in length to short day (12L) for 6 weeks in the summer, followed by transfer to 24L for another 6 weeks before transfer to seawater in late October. Three groups were studied in fresh water from July to the following May in order to elucidate the GH response to this photoperiod manipulation: one group was kept on 24L throughout (long-day group), while the other two groups were exposed to short day from July 15th. Of these, one was brought back onto long day on September 1st (winter group) while the other was kept on short day (short-day group). Plasma GH levels of the long-day group were around 1.6 ng/ml throughout the study. The short-day transfer suppressed GH levels to 0.7 ng/ml within 2 weeks (short-day and winter groups). The long-day transfer (winter group) increased GH levels to 11 ng/ml within 3 weeks, and this elevation of GH levels was sustained for about 3 months, before declining to pretreatment levels. The study demonstrates that underyearling Atlantic salmon react to increased daylength in a way similar to traditional yearling smolts. It also demonstrates for the first time that decreased daylength can suppress plasma GH levels in fish. It is concluded that winter photoperiod manipulation causes an out-of-season initiation and completion of the parr-smolt transformation of underyearling Atlantic salmon and that growth hormone plays a major role in this process.
22.	Björnsson, Björn Thrandur, 1952, et al. (författare) The Impact of Initial Energy Reserves on Growth Hormone Resistance and Plasma Growth Hormone-Binding Protein Levelsin Rainbow Trout Under Feeding and Fasting Conditions 2018 Ingår i: Frontiers in Endocrinology. - : Frontiers Media SA. - 1664-2392. ; 9 Tidskriftsartikel (refereegranskat)abstract The growth hormone (GH)-insulin-like growth factor I (IGF-I) system regulates important physiological functions in salmonid fish, including hydromineral balance, growth, and metabolism. While major research efforts have been directed toward this complex endocrine system, understanding of some key aspects is lacking. The aim was to provide new insights into GH resistance and growth hormone-binding proteins (GHBPs). Fish frequently respond to catabolic conditions with elevated GH and depressed IGF-I plasma levels, a condition of acquired GH resistance. The underlying mechanisms or the functional significance of GH resistance are, however, not well understood. Although data suggest that a significant proportion of plasma GH is bound to specific GHBPs, the regulation of plasma GHBP levels as well as their role in modulating the GH-IGF-I system in fish is virtually unknown. Two in vivo studies were conducted on rainbow trout. In experiment I, fish were fasted for 4 weeks and then refed and sampled over 72 h. In experiment II, two lines of fish with different muscle adiposity were sampled after 1, 2, and 4 weeks of fasting. In both studies, plasma GH, IGF-I, and GHBP levels were assessed as well as the hepatic gene expression of the growth hormone receptor 2a (ghr2a) isoform. While most rainbow trout acquired GH resistance within 4 weeks of fasting, fish selected for high muscle adiposity did not. This suggests that GH resistance does not set in while fat reserves as still available for energy metabolism, and that GH resistance is permissive for protein catabolism. Plasma GHBP levels varied between 5 and 25 ng ml(-1), with large fluctuations during both long-term (4 weeks) fasting and short-term (72 h) refeeding, indicating differentiated responses depending on prior energy status of the fish. The two opposing functions of GHBPs of prolonging the biological half-life of GH while decreasing GH availability to target tissues makes the data interpretation difficult, but nutritional regulatory mechanisms are suggested. The lack of correlation between hepatic ghr2a expression and plasma GHBP levels indicate that ghr2a assessment cannot be used as a proxy measure for GHBP levels, even if circulating GHBPs are derived from the GH receptor molecule.
23.	Breves, J. P., et al. (författare) Cortisol regulates insulin-like growth-factor binding protein (igfbp) gene expression in Atlantic salmon parr 2020 Ingår i: Molecular and Cellular Endocrinology. - : Elsevier BV. - 0303-7207 .- 1872-8057. ; 518 Tidskriftsartikel (refereegranskat)abstract © 2020 Elsevier B.V. The growth hormone (Gh)/insulin-like growth-factor (Igf)/Igf binding protein (Igfbp) system regulates growth and osmoregulation in salmonid fishes, but how this system interacts with other endocrine systems is largely unknown. Given the well-documented consequences of mounting a glucocorticoid stress response on growth, we hypothesized that cortisol inhibits anabolic processes by modulating the expression of hepatic igfbp mRNAs. Atlantic salmon (Salmo salar) parr were implanted intraperitoneally with cortisol implants (0, 10, and 40 μg g−1 body weight) and sampled after 3 or 14 days. Cortisol elicited a dose-dependent reduction in specific growth rate (SGR) after 14 days. While plasma Gh and Igf1 levels were unchanged, hepatic igf1 mRNA was diminished and hepatic igfbp1b1 and -1b2 were stimulated by the high cortisol dose. Plasma Igf1 was positively correlated with SGR at 14 days. Hepatic gh receptor (ghr), igfbp1a, -2a, -2b1, and -2b2 levels were not impacted by cortisol. Muscle igf2, but not igf1 or ghr, levels were stimulated at 3 days by the high cortisol dose. As both cortisol and the Gh/Igf axis promote seawater (SW) tolerance, and particular igfbps respond to SW exposure, we also assessed whether cortisol coordinates the expression of branchial igfbps and genes associated with ion transport. Cortisol stimulated branchial igfbp5b2 levels in parallel with Na+/K+-ATPase (NKA) activity and nka-α1b, Na+/K+/2Cl--cotransporter 1 (nkcc1), and cystic fibrosis transmembrane regulator 1 (cftr1) mRNA levels. The collective results indicate that cortisol modulates the growth of juvenile salmon via the regulation of hepatic igfbp1s whereas no clear links between cortisol and branchial igfbps previously shown to be salinity-responsive could be established.
24.	Breves, J. P., et al. (författare) Hepatic insulin-like growth factor binding protein (igfbp) responses to food restriction in Atlantic salmon smolts 2016 Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 233, s. 79-87 Tidskriftsartikel (refereegranskat)abstract The growth hormone (Gh)/insulin-like growth-factor (Igf) system plays a central role in the regulation of growth in fishes. However, the roles of Igf binding proteins (Igfbps) in coordinating responses to food availability are unresolved, especially in anadromous fishes preparing for seaward migration. We assayed plasma Gh, Igf1, thyroid hormones and cortisol along with igfbp mRNA levels in fasted and fed Atlantic salmon (Salmo solar). Fish were fasted for 3 or 10 days near the peak of smoltification (late April to early May). Fasting reduced plasma glucose by 3 days and condition factor by 10 days. Plasma Gh, cortisol, and thyroxine (T-4) were not altered in response to fasting, whereas Igf1 and 3,5,3'-triiodo-L-thyronine (T-3) were slightly higher and lower than controls, respectively. Hepatic igfbp1b1, -1b2, -2a,-2b1 and -2b2 mRNA levels were not responsive to fasting, but there were marked increases in igfbp1a1 following 3 and 10 days of fasting. Fasting did not alter hepatic igf1 or igf2; however, muscle igf1 was diminished by 10 days of fasting. There were no signs that fasting compromised branchial ionoregulatory functions, as indicated by unchanged Na+/K+-ATPase activity and ion pump/transporter mRNA levels. We conclude that dynamic hepatic igfbp1a1 and muscle igf1 expression participate in the modulation of Gh/Igf signaling in smolts undergoing catabolism.
25.	Breves, J. P., et al. (författare) In vivo effects of 17α-ethinylestradiol, 17β-estradiol and 4-nonylphenol on insulin-like growth-factor binding proteins (igfbps) in Atlantic salmon 2018 Ingår i: Aquatic Toxicology. - : Elsevier BV. - 0166-445X. ; 203, s. 28-39 Tidskriftsartikel (refereegranskat)abstract Feminizing endocrine disrupting compounds (EDCs) affect the growth and development of teleost fishes. The major regulator of growth performance, the growth hormone (Gh)/insulin-like growth-factor (Igf) system, is sensitive to estrogenic compounds and mediates certain physiological and potentially behavioral consequences of EDC exposure. Igf binding proteins (Igfbps) are key modulators of Igf activity, but their alteration by EDCs has not been examined. We investigated two life-stages (fry and smolts) of Atlantic salmon (Salmo salar), and characterized how the Gh/Igf/Igfbp system responded to waterborne 17α-ethinylestradiol (EE2), 17β-estradiol (E2) and 4-nonylphenol (NP). Fry exposed to EE2 and NP for 21 days had increased hepatic vitellogenin (vtg) mRNA levels while hepatic estrogen receptor α (erα), gh receptor (ghr), igf1 and igf2 mRNA levels were decreased. NP-exposed fry had reduced body mass and total length compared to controls. EE2 and NP reduced hepatic igfbp1b1, -2a, -2b1, -4, -5b2 and -6b1, and stimulated igfbp5a. In smolts, hepatic vtg mRNA levels were induced following 4-day exposures to all three EDCs, while erα only responded to EE2 and E2. EDC exposures did not affect body mass or fork length; however, EE2 diminished plasma Gh and Igf1 levels in parallel with reductions in hepatic ghr and igf1. In smolts, EE2 and E2 diminished hepatic igfbp1b1, -4 and -6b1, and stimulated igfbp5a. There were no signs of compromised ionoregulation in smolts, as indicated by unchanged branchial ion pump/transporter mRNA levels. We conclude that hepatic igfbps respond (directly and/or indirectly) to environmental estrogens during two key life-stages of Atlantic salmon, and thus may modulate the growth and development of exposed individuals.
26.	Breves, J. P., et al. (författare) Variation in branchial expression among insulin-like growth-factor binding proteins (igfbps) during Atlantic salmon smoltification and seawater exposure 2017 Ingår i: BMC Physiology. - : Springer Science and Business Media LLC. - 1472-6793. ; 17:1 Tidskriftsartikel (refereegranskat)abstract Background: In preparation for migration from freshwater to marine habitats, Atlantic salmon (Salmo salar L.) undergo smoltification, a transformation that includes the acquisition of hyposmoregulatory capacity. The growth hormone (Gh)/insulin-like growth-factor (Igf) axis promotes the development of branchial ionoregulatory functions that underlie ion secretion. Igfs interact with a suite of Igf binding proteins (Igfbps) that modulate hormone activity. In Atlantic salmon smolts, igfbp4,-5a,-5b1,-5b2,-6b1 and-6b2 transcripts are highly expressed in gill. We measured mRNA levels of branchial and hepatic igfbps during smoltification (March, April, and May), desmoltification (July) and following seawater (SW) exposure in March and May. We also characterized parallel changes in a broad suite of osmoregulatory (branchial Na+/K+-ATPase (Nka) activity, Na + /K + /2Cl - cotransporter 1 (nkcc1) and cystic fibrosis transmembrane regulator 1 (cftr1) transcription) and endocrine (plasma Gh and Igf1) parameters. Results: Indicative of smoltification, we observed increased branchial Nka activity, nkcc1 and cftr1 transcription in May. Branchial igfbp6b1 and -6b2 expression increased coincidentally with smoltification. Following a SW challenge in March, igfbp6b1 showed increased expression while igfbp6b2 exhibited diminished expression. igfbp5a,-5b1 and-5b2 mRNA levels did not change during smolting, but each had lower levels following a SW exposure in March. Conclusions: Salmonids express an especially large suite of igfbps. Our data suggest that dynamic expression of particular igfbps accompanies smoltification and SW challenges; thus, transcriptional control of igfbps may provide a mechanism for the local modulation of Igf activity in salmon gill. © 2017 The Author(s).
27.	Brockmark, Sofia, 1973, et al. (författare) Effects of rearing density and tank enrichment on the pre- and post-release performance of Atlantic salmon (Salmo salar) 2007 Ingår i: Trans. Am. Fish. Soc.. - 0002-8487. ; 136, s. 1453-1462 Tidskriftsartikel (refereegranskat)
28.	Crespo, D., et al. (författare) The initiation of puberty in Atlantic salmon brings about large changes in testicular gene expression that are modulated by the energy status 2019 Ingår i: BMC Genomics. - : Springer Science and Business Media LLC. - 1471-2164. ; 20 Tidskriftsartikel (refereegranskat)abstract BackgroundWhen puberty starts before males reach harvest size, animal welfare and sustainability issues occur in Atlantic salmon (Salmo salar) aquaculture. Hallmarks of male puberty are an increased proliferation activity in the testis and elevated androgen production. Examining transcriptional changes in salmon testis during the transition from immature to maturing testes may help understanding the regulation of puberty, potentially leading to procedures to modulate its start. Since differences in body weight influence, via unknown mechanisms, the chances for entering puberty, we used two feed rations to create body weight differences.ResultsMaturing testes were characterized by an elevated proliferation activity of Sertoli cells and of single undifferentiated spermatogonia. Pituitary gene expression data suggest increased Gnrh receptor and gonadotropin gene expression, potentially responsible for the elevated circulating androgen levels in maturing fish. Transcriptional changes in maturing testes included a broad variety of signaling systems (e.g. Tgf, Wnt, insulin/Igf, nuclear receptors), but also, activation of metabolic pathways such as anaerobic metabolism and protection against ROS. Feed restriction lowered the incidence of puberty. In males maturing despite feed restriction, plasma androgen levels were higher than in maturing fish receiving the full ration. A group of 449 genes that were up-regulated in maturing fully fed fish, was up-regulated more prominently in testis from fish maturing under caloric restriction. Moreover, 421 genes were specifically up-regulated in testes from fish maturing under caloric restriction, including carbon metabolism genes, a pathway relevant for nucleotide biosynthesis and for placing epigenetic marks.ConclusionsUndifferentiated spermatogonia and Sertoli cell populations increased at the beginning of puberty, which was associated with the up-regulation of metabolic pathways (e.g. anaerobic and ROS pathways) known from other stem cell systems. The higher androgen levels in males maturing under caloric restriction may be responsible for the stronger up-regulation of a common set of (449) maturation-associated genes, and the specific up-regulation of another set of (421) genes. The latter opened regulatory and/or metabolic options for initiating puberty despite feed restriction. As a means to reduce the incidence of male puberty in salmon, however, caloric restriction seems unsuitable.
29.	Cucherousset, J., et al. (författare) Growth-enhanced salmon modify stream ecosystem functioning 2021 Ingår i: Journal of Fish Biology. - : Wiley. - 0022-1112 .- 1095-8649. ; 99:6, s. 1978-1989 Tidskriftsartikel (refereegranskat)abstract Use of fast-growing domesticated and/or genetically modified strains of fish is becoming increasingly common in aquaculture, increasing the likelihood of deliberate or accidental introductions into the wild. To date, their ecological impacts on ecosystems remain to be quantified. Here, using a controlled phenotype manipulation by implanting growth hormone in juvenile Atlantic salmon (Salmo salar), we found that growth-enhanced fish display changes in several phenotypic traits known to be important for ecosystem functioning, such as habitat use, morphology and excretion rate. Furthermore, these phenotypic changes were associated with significant impacts on the invertebrate community and key stream ecosystem functions such as primary production and leaf-litter decomposition. These findings provide novel evidence that introductions of growth-enhanced fish into the wild can affect the functioning of natural ecosystems and represent a form of intraspecific invasion. Consequently, environmental impact assessments of growth-enhanced organisms need to explicitly consider ecosystem-level effects.
30.	Einarsdottir, Ingibjörg, 1951, et al. (författare) Atlantic halibut growth hormone: structure and plasma levels of sexually mature males and females during photoperiod-regulated annual cycles 2002 Ingår i: General and Comparative Endocrinology. - 0016-6480 .- 1095-6840. ; 127:1, s. 94-104 Tidskriftsartikel (refereegranskat)abstract The main objectives of this study were to obtain the amino acid sequence of Atlantic halibut (Hippoglossus hippoglossus) growth hormone (hhGH) and compare it with other teleost species, to establish a radioimmunoassay to assess plasma hhGH levels and thus to gain information about possible biological functions and regulation by photoperiod. The hhGH gene was cloned and its amino acid sequence deduced from the cDNA. The mature hhGH protein consists of 186 amino acids. Comparison with other flatfish species as well as a species from a different order, the pufferfish, reveals that the sequence similarities of the mature hhGH with that of the barfin flounder, the Japanese flounder, the sole and the pufferfish are 99.5, 81.7, 74.2, and 65.2%, respectively. The sequence similarities appear to correctly reflect the gross phylogenetic relationships among these telcost species. A specific GH-RIA was developed for measurements of Atlantic halibut GH levels. Assessment of plasma GH levels in adult halibut revealed large gender differences, with GH levels frequently being an order of magnitude higher in males than females. The mean (+/-SEM) plasma GH for males kept on normal annual photoperiod were 25.2 +/- 6.11 ng ml(-1) and for females were 5.14 +/- 1.94 ng ml(-1). It appears likely that plasma growth hormone levels in Atlantic halibut can be inversely correlated to growth and metabolism. Shifting of the annual photoperiod cycles demonstrated that photoperiod in not a regulator of plasma GH levels in the Atlantic halibut. but further research is needed to assess whether GH plays a role in the reproduction of this marine teleost species. (C) 2002 Elsevier Science (USA). All rights reserved.
31.	Einarsdottir, Ingibjörg, 1951, et al. (författare) Distribution of ghrelin-producing cells and Na+,K+-ATPase in tissues of Atlantic halibut (Hippoglossus hippoglossus) during early development. 2010 Ingår i: European Aquaculture Scociety, Porto, Potugal, October 5-8, 2010. ; Conference Program Konferensbidrag (övrigt vetenskapligt/konstnärligt)
32.	Einarsdottir, Ingibjörg, 1951, et al. (författare) GH-receptor derived plasma GH binding protein in rainbow trout : Effects of fasting and a single-meal refeeding 2012 Ingår i: 7th International Symposium of Fish Endocrinology, Buenos Aires, Argentina, 3-6 September 2012. ; Program and Abstract Book Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract Plasma growth hormone binding proteins (GHBPs) transport circulating growth hormone (GH), function as a GH pool and prevent GH from degradation. In mammals, high-affinity GHBPs are identical to the extracellular domain of the growth hormone receptor (GHR). GHBPs have been demonstrated in fish, but their molecular identity has not been confirmed. To examine a possible GHR origin of plasma GHBPs in rainbow trout, a GHBP radioimmunoassay was established, using antibodies raised against a synthesized peptide sequence of the salmonid GHR extracellular domain, and recombinant proteins for iodination and standards. In order to examine effects of nutritional state on GHBP levels, rainbow trout were fasted for four weeks while a control group was fed to satiation. Then, all fish received a single meal and were sampled 2, 4, 8, 24 and 72 h postprandially. During the 4-week fasting, GHBP levels did not change, while plasma GH levels increased, as has been shown in earlier studies. Following the meal, a transient decrease in both GH and GHBP was seen in the fasted fish, lasting 2 to 4 h. This is the first time plasma GHBP levels have been measured in fish. The data indicate that GHBP and GH levels may be regulated independently or in concert. Supported by EU (Project LIFECYCLE FP7-222719).
33.	Einarsdottir, Ingibjörg, 1951, et al. (författare) Growth hormone profiles and development of somatotrophs in Atlantic halibut larvae 2000 Ingår i: International Congress on the Biology of Fish, July 23-27, 2000. Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract Introduction. The Atlantic halibut is the largest flatfish species, and as other flatfish, has a complicated larval development. The pelagic larvae hatch after about two weeks and feeding starts six weeks later. After three to four months, they start to undergo metamorphosis. Following major changes in body shape, including the migration of the left to the right side, the larvae settle as bottom dwelling. In Atlantic halibut aquaculture, the larval rearing is a critical rearing stage, with high incidence of mortality and abnormal development. Growth hormone in teleost fishes is known to participate in the regulation of several important physiological processes including metabolism, growth, appetite, and osmoregulation. It is therefore likely that the hormone may be important for larval growth and development. Therefore, this study was carried out in order to elucidate the growth hormone (GH) endocrinology of halibut larvae, by measuring GH tissue content as well as the histology of the pituitary somatotrophs. Materials and Methods. The study was carried out with unfertilized eggs and larvae from hatching through metamorphosis (from 22 to 859 day-degrees (D°)), collected at the halibut hatchery of Fiskey Ltd, Northern Iceland, over two consecutive years. In order to study GH profiles during early development, a homologous radioimmunoassay was established. GH was isolated from adult halibut pituitaries collected at Fiskey Ltd, using methods modified from Johnson et al (1997). In the radioimmunoassay, this GH was used for standards and iodination, together with specific antibodies raised in rabbits, courtesy of Dr. P. Swanson. For the immunohistochemistry of GH-producing somatotrophs in the pituitaries, anti-halibut antibodies were raised in rabbits and validated. Results and Conclusions. Tissue GH analysis revealed that GH is detectable in unfertilized eggs. In developing larvae, tissue GH content per body weight increased during development from hatching to metamorphosis. The earliest stage at which GH was localized in the somatotrophs by immunohistochemistry, was at the age of 187 D°. The present study demonstrates that there appears to be a maternal source of growth hormone in halibut eggs, similar to what has been demonstrated for thyroid hormones in eggs of different teleost species (Kobuke et al 1987). The study further demonstrates that endogenous production of growth hormone is initiated early in larval development, during the yolk-sack stage, prior to first feeding. The study establishes that GH can play a regulatory role during early development of the Atlantic halibut
34.	Einarsdottir, Ingibjörg, 1951, et al. (författare) Isolation of Atlantic halibut pituitary hormones by continuous-elution electrophoresis followed by fingerprint identification, and assessment of growth hormone content during larval development 2007 Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 150:2, s. 355-363 Tidskriftsartikel (refereegranskat)abstract Continuous-elution electrophoresis (CEE) has been applied to separate putative hormones from adult Atlantic halibut pituitaries. Soluble proteins were separated by size and charge on Model 491 Prep Cell (Bio-Rad), where the homogenate runs through a cylindrical gel, and protein fractions are collected as they elute from the matrix. Protein fractions were assessed by SDS–PAGE and found to contain purified proteins of molecular size from 10 to 33 kDa. Fractions containing proteins with molecular weights of approximately 21, 24, 28 and 32 kDa, were identified as putative growth hormone (GH), prolactin, somatolactin and gonadotropins, respectively. These were analyzed further by mass spectrometry and identified with peptide mass protein fingerprinting. The CEE technique was used successfully for purification of halibut GH with a 5% yield, and appears generally well suited to purify species-specific proteins often needed for research in comparative endocrinology, including immunoassay work. Thus, the GH obtained was subsequently used as standards and iodination label in a homologous radioimmunoassay, applied to analyze GH content through larval development in normally and abnormally metamorphosing larvae. As GH is mainly found in the pituitary, GH contents were analyzed in tissue extracts from the heads only. The pituitary GH content increases proportionally to increased larval weight from first feeding to metamorphic climax. No difference in relative GH content was found between normal and abnormal larvae and it still remains to be established if GH has a direct role in metamorphosis.
35.	Einarsdottir, Ingibjörg, 1951, et al. (författare) Occurrence of ghrelin-producing cells, the ghrelin receptor and Na+,K+-ATPase in tissues of Atlantic halibut 2011 Ingår i: Cell and Tissue Resarch. - 0302-766X. ; 344:3, s. 481-498 Tidskriftsartikel (refereegranskat)abstract Ghrelin is a pituitary growth hormone (GH)-secretagogue that also has metabolic, reproductive, proliferative, immunological and brain functions in mammals. Far less is known about its role in fish. We have therefore performed an immunohistochemical determination of its tissue distribution in the developing Atlantic halibut (Hippoglossus hippoglossus) to gain insights into its potential function. Ghrelin immunoreactivity was detected in first-feeding halibut larvae in the skin, urinary bladder, gastrointestinal (GI) tract and olfactory lobe of the brain. In subsequent stages up to metamorphosis, ghrelin immunoreactivity declined in the skin and became evident in the gills. When the stomach developed, ghrelin immunoreactivity declined throughout the GI tract with the exception of the stomach, which exhibited an intense signal. Immunoreactive ghrelin cells were also present in the olfactory lobe, nerve and epithelium and in occasional cells of the buccal cavity and oesophagus. Ghrelin immunoreactivity had an overlapping distribution with that for Na(+),K(+)-ATPase, colocalisation also being observed in some ionocytes of the gill. The co-expression of ghrelin and the GH-secretagogue receptor in the same tissue indicates that ghrelin can exert both endocrine and paracrine actions in the developing halibut. The presence of immunoreactive ghrelin in several osmoregulatory tissues, the GI tract and sensory tissue provides strong evidence that ghrelin has multiple functions during development and also suggests targets for future investigations.
36.	Einarsdottir, Ingibjörg, 1951, et al. (författare) PITUITARY HORMONE PURIFICATION BY CONTINUOUS-ELUTION ELECTROPHORESIS 2006 Ingår i: 7th International Congress on the Biology of Fishes, Book of Abstracts. Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract Widely used methods for peptide hormone purification, such as gel filtration chromatography combined with rpHPLC, are time-consuming and often give low yields and instable proteins. The Model 491 Prep Cell from Bio-Rad provides a continuous-elution electrophoresis technique to separate proteins. The protein mixture runs through a cylindrical gel, proteins are separated by size and charge, as they elute from the matrix and are collected using a fraction collector. Sub-samples are assessed by SDS-PAGE and protein identity is verified by Western blot analysis. We applied this technique to separate putative hormones from adult Atlantic halibut pituitaries. Soluble proteins from homogenized pituitaries were denatured and subjected to continuous-elution electrophoresis. The fractions sampled contained purified proteins with molecular sizes ranging from 10 to 33 kDa. Fractions containing proteins with molecular weights of approximately 21, 24, 28 and 32 kDa were identified as putative growth hormone, prolactin, somatolactin and gonadotropins. These were analyzed further by mass spectrometry (MS) and identified with peptide mass protein fingerprinting. Good yield of highly purified GH was obtained, identified, and found to be biologically stable. Subsequently, it was used for radioactive labeling and as standards in a homologous RIA. Using this assay, the GH was measured in halibut larvae from start-feeding through metamorphosis, showing a stable size-related GH content of the head region. Funded by the EU.
37.	Einarsdottir, Ingibjörg, 1951, et al. (författare) Plasma growth hormone-binding protein levels in Atlantic salmon Salmo salar during smoltification and seawater transfer 2014 Ingår i: Journal of Fish Biology. - : Wiley. - 0022-1112. ; 85:4, s. 1279-1296 Tidskriftsartikel (refereegranskat)abstract Specific growth hormone (GH)-binding protein (Ghbp) was purified from Atlantic salmon Salmo salar and rainbow trout Oncorhynchus mykiss plasma with immunoprecipitation and characterized in cross-linking studies using autoradiography and western blots. The size of the Ghbp was estimated to be c. 53 kDa. A radioimmunoassay was established to measure Ghbp in salmonids, using antibodies specific against the extracellular segment of the S. salar growth hormone receptor 1 (grh1; GenBank AY462105). Plasma Ghbp levels were measured in S. salar smolts in fresh water and after transfer to seawater (SW; experiments 1 and 2), and in post-smolts kept at different salinities (0, 12, 22 and 34) for 3 months (experiment 3). A transient increase in plasma Ghbp, which lasted for 1 month or less, was noted in smolts after transfer to SW. Concomitantly, plasma GH and gill Na+-K+-ATPase activity increased during smoltification (in experiment 2). No difference in plasma Ghbp was evident between post-smolts kept at different salinities, although the fish kept at salinity 34 had higher plasma GH than the group kept at salinity 22 and higher hepatic ghr1 expression than post-smolts kept at salinity 12. This suggests that plasma Ghbp regulation may respond to salinity changes in the short term. The lack of correlation between Ghbp, plasma GH and hepatic ghr1 expression in the long-term post-smolt experiment indicates that Ghbp levels may be regulated independently of other components of the endocrine GH system in salmonids.
38.	Einarsdottir, Ingibjörg, 1951, et al. (författare) Plasma growth hormone levels during sexual maturation of Atlantic halibut: influence of annual photoperiod cycle 2001 Ingår i: 14th International Congress of Comparative Endocrinology (ICCE), Sorrento, Italy, May 26-30, 2001. ; Book of Abstracts Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract Three groups of sexually mature male and female Atlantic halibut (Hippoglossus hippoglossus), kept in indoor tanks under computer-simulated photoperiod regimes, were serially sampled every month over three annual maturational cycles (Björnsson et al 1998). During the ini¬tial phase of the study, the annual photoperiod cycle was advanced by four months for one group and delayed by four months for another, while the third control group was kept on simulated natural annual pho¬toperiod cycle. Plasma growth hormone levels (GH) were assessed using a newly estab¬lished halibut GH-RIA (Einarsdottir et al 2000, in prep). In the control group, males had much higher GH levels than females and showed strong annual variations, with a rapid rise in GH levels to ca 50 ng/ml towards the beginning of female spawning. At that time, the GH levels of the females were only around 0.5-2 ng/ml, and rarely exceeding 10 ng/ml at other times of the year. The advancement and delay of the annual photoperiod cycle by four months resulted in gradual corresponding shifts in spawning time, reaching four months after three annual cycles (Björnsson et al 1998). As in controls, the over-all difference in GH levels between males and females was seen in the advanced and the delayed groups. However, the shift in annual photoperiod cycle caused a certain disruption of the annual GH cycle in males, but the pattern re-emerged towards the end of the study, shifted in line with the annual photoperiod shift. As the annual spawning period and GH changes are shifted in parallel, the study does not establish a causal relationship between GH levels and sexual maturation in the halibut. However, as in other teleost species such as the salmonids, seasonal changes in plasma GH levels appear to be under photoperiod control. Financial support by EU-FAIR (CT96-1422) and the Nordic Industrial Fund Björnsson et al 1998. Aquaculture 166: 117-140
39.	Einarsdottir, Ingibjörg, 1951, et al. (författare) Purification of pituitary hormones from the Atlantic halibut (Hippoglossus hippoglossus) by continuous-elution electrophoresis and identification of isolated proteins by fingerprinting 2004 Ingår i: 5th International Symposium on Fish Endocrinology, Book of Abstracts. Konferensbidrag (övrigt vetenskapligt/konstnärligt)
40.	Einarsdottir, Ingibjörg, 1951, et al. (författare) The growth hormone – IGF-I system is involved in cranial tissue remodeling in metamorphosing Atlantic halibut larvae 2008 Ingår i: Sixth International Symposium on Fish Endocrinology (6ISFE) Program and Abstract Book. Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract The Atlantic halibut is a large, cold-water flatfish which inhabits the North Atlantic. The pelagic and symmetric larvae undergo metamorphosis as an adaptation to better suit them for a benthic life. Metamorphosis involves many dramatic biological changes including a major reconstruction of the cranium during which the left eye migrates to the right side of the head. The structural driving force of eye migration is assumed to be the growth and migration of the ethmoid plate and the migration of the frontal processes towards the future ocular side, and fibroblast proliferation ventrally to the migrating eye. Metamorphosis is under endocrine control and thyroid hormones are known to be the main regulatory hormones. Data on the role of other growth regulators, including the growth hormone (GH) - insulin-like growth factor I (IGF-I) system, in halibut metamorphosis are sparse. GH content in the head region increases steadily from first feeding throughout the larval phase until post-metamorphosis, while IGF-I content in the body increases until the onset of metamorphosis and decline thereafter. In situ hybridization and immunohistochemistry reveal that mRNA and proteins of the type I GH receptor (GHR), and mRNA of the type II GHR and the IGF-I receptor (IGF-IR) are expressed in fibroblasts in soft tissue between the eyes, frontal bone osteocytes and dorsal cranial chondrocytes during the metamorphic process. In fibroblasts and chondrocytes, the expression appears most intense at the start of metamorphosis (stage 8) and decreases during subsequent developmental stages. IGF-IR expression decreases in frontal bone osteocytes after the completion of metamorphosis (stage 10). The decrease in tissue IGF-I content during metamorphosis, and the localization and change in abundance of GHRs and IGF-IR in head structures undergoing reconstruction, indicate the involvement of the GH-IGF-I system in Atlantic halibut metamorphosis. Acknowledgement: Work financed by the Commission of the European Communities within the project “Arrested development: the molecular and endocrine basis of flatfish metamorphosis” (Q5RS-2002-01192).
41.	Einarsdottir, Ingibjörg, 1951, et al. (författare) The relationship between growth hormone, growth hormone receptor and growth hormone binding proteins in smolting Atlantic salmon 2013 Ingår i: Smolt-conference, Reykjavik, Island, 12-16 August 2013. Konferensbidrag (övrigt vetenskapligt/konstnärligt)
42.	Einarsdottir, Ingibjörg, 1951, et al. (författare) Thyroid and pituitary gland development from hatching through metamorphosis of a teleost flatfish, the Atlantic halibut 2006 Ingår i: Anatomy and Embryology. - : Springer Science and Business Media LLC. - 0340-2061 .- 1432-0568. ; 211:1, s. 47-60 Tidskriftsartikel (refereegranskat)abstract Fish larval development, not least the spectacular process of flatfish metamorphosis, appears to be under complex endocrine control, many aspects of which are still not fully elucidated. In order to obtain data on the functional development of two major endocrine glands, the pituitary and the thyroid, during flatfish metamorphosis, histology, immunohistochemistry and in situ hybridization techniques were applied on larvae of the Atlantic halibut (Hippoglossus hippoglossus), a large, marine flatfish species, from hatching through metamorphosis. The material was obtained from a commercial hatchery. Larval age is defined as day-degrees (D degrees=accumulated daily temperature from hatching). Sporadic thyroid follicles are first detected in larvae at 142 D degrees (27 days post-hatch), prior to the completion of yolk sack absorption. Both the number and activity of the follicles increase markedly after yolk sack absorption and continue to do so during subsequent development. The larval triiodothyronine (T-3) and thyroxine (T-4) content increases, subsequent to yolk absorption, and coincides with the proliferation of thyroid follicles. A second increase of both T-3 and T-4 occurs around the start of metamorphosis and the T-3 content further increases at the metamorphic climax. Overall, the T-3 content is lower than T-4. The pituitary gland can first be distinguished as a separate organ at the yolk sack stage. During subsequent development, the gland becomes more elongated and differentiates into neurohypophysis (NH), pars distalis (PD) and pars intermedia (PI). The first sporadic endocrine pituitary cells are observed at the yolk sack stage, somatotrophs (growth hormone producing cells) and somatolactotrophs (somatolactin producing cells) are first observed at 121 D degrees (23 days post-hatch), and lactotrophs (prolactin producing cells) at 134 D degrees (25 days post-hatch). Scarce thyrotrophs are evident after detection of the first thyroid follicles (142 D degrees), but coincident with a phase in which follicle number and activity increase (260 D degrees). The somatotrophs are clustered in the medium ventral region of the PD, lactotrophs in the anterior part of the PD and somatolactotrophs are scattered in the mid and posterior region of the pituitary. At around 600 D degrees, coinciding with the start of metamorphosis, somatolactotrophs are restricted to the interdigitating tissue of the NH. During larval development, the pituitary endocrine cells become more numerous. The present data on thyroid development support the notion that thyroid hormones may play a significant role in Atlantic halibut metamorphosis. The time of appearance and the subsequent proliferation of pituitary somatotrophs, lactotrophs, somatolactotrophs and thyrotrophs indicate at which stages of larval development and metamorphosis these endocrine cells may start to play active regulatory roles.
43.	Fjelldal, Per Gunnar, et al. (författare) Exogenous growth hormone (GH) increases dimension and reduces strength of vertebrae in Atlantic salmon (Salmo salar) 2024 Ingår i: AQUACULTURE. - 0044-8486 .- 1873-5622. ; 589 Tidskriftsartikel (refereegranskat)abstract Growth hormone (GH) administration increases bone strength in rats, mainly through alterations of the dimensional proportions of vertebrae. However, similar knowledge is lacking in other clades. In order to pursue this, Atlantic salmon were fed diets with high or low vitamin C and E and administered a slow -release implant of bovine GH. While neither the diets or the GH treatment affected growth, GH reduced condition factor and carcass -somatic index, and increased the hepatosomatic and visceral -somatic indexes. GH had an impact on the dimensional proportions of the vertebrae and increased the relative dorso-ventral and lateral vertebra diameters. Moreover, GH decreased the mechanical strength of the vertebra, both with (modulus of elasticity, failure point) and without (stiffness) normalizing the mechanical data for the dimensions of the vertebrae. Diet did not impact on the vertebra morphometry or mechanical strength. RNA-seq of vertebra centra show that several genes associated with bone growth and remodelling were affected by GH, while there was an interactive effect between diet vitamin level and GH on several genes associated with lipid metabolism. The data may suggest that exogenous GH affects the bone cellular mechanisms of Atlantic salmon postsmolts in such a way that their vertebrae increase in diameter but not length, not disturbing growth in body length. The GH and diet effects on lipid metabolism associated genes indicate a complex regulation of the lipids stored inside the vertebral column by endocrine and nutritional factors.
44.	Froiland, E., et al. (författare) Seasonal appetite regulation in the anadromous Arctic charr: Evidence for a role of adiposity in the regulation of appetite but not for leptin in signalling adiposity 2012 Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 178:2, s. 330-337 Tidskriftsartikel (refereegranskat)abstract The aim of this study was to investigate whether the seasonal feeding cycle of the anadromous Arctic charr (Salvelinus alpinus) is regulated by a lipostatic mechanism and if leptin (Lep) might act as an endocrine signal of adiposity. Offspring of anadromous Arctic charr with a body mass of 121 g were divided into two treatment groups; one was given feed in excess from March to November. and the other was fasted between April and early June and fed in excess thereafter. In the continuously fed group there was an 8-fold increase in body mass, and a doubling of percentage body fat, from March to August, after which there was no further increase. Fish in the other group lost weight and body fat during fasting, but grew rapidly on being fed, and had partially compensated for their deficit in body mass by August. Differences in percentage body fat between treatment groups were eliminated by August. providing evidence for a lipostatic regulation of feeding and energy homeostasis in Arctic charr. Neither liver total LepA gene expression nor plasma Lep concentrations correlated positively with fish adiposity, so there was no evidence that Lep acts as a signal of adiposity in this species. On the other hand, there was a strong increase in liver LepA1 gene expression at the end of the fasting period, concomitant with fat mobilization and increased plasma glucose, indicating that LepA1 may play a role in regulating metabolic processes associated with fasting. (C) 2012 Elsevier Inc. All rights reserved.
45.	Fuentes, EN, et al. (författare) IGF-I/PI3K/Akt and IGF-I/MAPK/ERK pathways in vivo in skeletal muscle are regulated by nutrition and contribute to somatic growth in the fine flounder 2011 Ingår i: American Journal of Physiology - Regulatory, Integrative. - 0363-6119. ; 300:6, s. 1532-1542 Tidskriftsartikel (refereegranskat)abstract The insulin-like growth factor-I (IGF-I) is a key regulator of skeletal muscle growth in vertebrates, promoting mitogenic and anabolic effects through the activation of the MAPK/ERK and the PI3K/Akt signaling pathways. Nutrition also affects skeletal muscle growth, activating intracellular pathways and inducing protein synthesis and accretion. Thus, both hormonal and nutritional signaling regulate muscle mass. In this context, plasma IGF-I levels and the activation of both pathways in response to food were evaluated in the fine flounder using fasting and refeeding trials. The present study describes for the first time in a nonmammalian species that the MAPK/ERK and PI3K/Akt are activated by exogenous circulating IGF-I, as well as showing that the MAPK/ERK pathway activation is modulated by the nutritional status. Also, these results show that there is a time-dependent regulation of IGF-I plasma levels and its signaling pathways in muscle. Together, these results suggest that the nutritionally managed IGF-I could be regulating the activation of the MAPK/ERK and the PI3K/Akt signaling pathways differentially according to the nutritional status, triggering different effects in growth parameters and therefore contributing to somatic growth in fish. This study contributes to the understanding of the nutrient regulation of IGF-I and its signaling pathways in skeletal muscle growth in nonmammalian species, therefore providing insight concerning the events controlling somatic growth in vertebrates.
46.	Fuentes, E. N., et al. (författare) Inherent Growth Hormone Resistance in the Skeletal Muscle of the Fine Flounder Is Modulated by Nutritional Status and Is Characterized by High Contents of Truncated GHR, Impairment in the JAK2/STAT5 Signaling Pathway, and Low IGF-I Expression 2012 Ingår i: Endocrinology. - : The Endocrine Society. - 0013-7227 .- 1945-7170. ; 153:1, s. 283-294 Tidskriftsartikel (refereegranskat)abstract A detailed understanding of how the GH and IGF-I regulate muscle growth, especially in early vertebrates, is still lacking. The fine flounder is a flatfish species exhibiting remarkably slow growth, representing an intriguing model for elucidating growth regulatory mechanisms. Key components of the GH system were examined in groups of fish during periods of feeding, fasting, and refeeding. Under feeding conditions, there is an inherent systemic and local (muscle) GH resistance, characterized by higher levels of plasma GH than of IGF-I, skeletal muscle with a greater content of the truncated GH receptor (GHRt) than of full-length GHR (GHRfl), an impaired activation of the Janus kinase 2 (JAK2)-signal transducers and activators of transcription 5 (STAT5) signaling pathway, and low IGF-I expression. Fasting leads to further elevation of plasma GH levels concomitant with suppressed IGF-I levels. The ratio of GHRfl to GHRt in muscle decreases during fasting, causing an inactivation of the JAK2/STAT5 signaling pathway and suppressed IGF-I expression, further impairing growth. When fish are returned to nutritionally favorable conditions, plasma GH levels decrease, and the ratio of GHRfl to GHRt in muscle increases, triggering JAK2/STAT5 reactivation and local IGF-I expression, concomitant with increased growth. The study suggests that systemic IGF-I is supporting basal slow growth in this species, without ruling out that local IGF-I is participating in muscle growth. These results reveal for the first time a unique model of inherent GH resistance in the skeletal muscle of a nonmammalian species and contribute to novel insights of the endocrine and molecular basis of growth regulation in earlier vertebrates. (Endocrinology 153:283-294, 2012)
47.	Fuentes, E. N., et al. (författare) Nutritional status modulates plasma leptin, AMPK and TOR activation, and mitochondrial biogenesis: Implications for cell metabolism and growth in skeletal muscle of the fine flounder 2013 Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 186, s. 172-180 Tidskriftsartikel (refereegranskat)abstract Insight of how growth and metabolism in skeletal muscle are related is still lacking in early vertebrates. In this context, molecules involved in these processes, such as leptin, AMP-activated protein kinase (AMPK), target of rapamicyn (TOR), peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α, and oxidative phosphorylation complexes (OXPHOS), were assessed in the skeletal muscle of a fish species. Periods of fasting followed by a period of refeeding were implemented, using the fine flounder as a model (Paralichthys adspersus). This species exhibits remarkably slow growth and food intake, which is linked to an inherent growth hormone (GH) resistance and high circulating levels of leptin. Leptin increased during fasting concomitantly with AMPK activation, which was inversely correlated with TOR activation. On the other hand, AMPK was directly correlated with an increase in PGC-1α and OXPHOS complexes contents. Dramatic changes in the activation and content of these molecules were observed during short-term refeeding. Leptin, AMPK activation, and PGC-1α/OXPHOS complexes contents decreased radically; whereas, TOR activation increased significantly. During long-term refeeding these molecules returned to basal levels. These results suggest that there is a relation among these components; thus, during fasting periods ATP-consuming biosynthetic pathways are repressed and alternative sources of ATP/energy are promoted, a phenomenon that is reversed during anabolic periods. These results provide novel insight on the control of metabolism and growth in the skeletal muscle of a non-mammalian species, suggesting that both processes in fish muscle are closely related and coordinated by a subset of common molecules.
48.	Fuentes, E. N., et al. (författare) Plasma leptin and growth hormone levels in the fine flounder (Paralichthys adspersus) increase gradually during fasting and decline rapidly after refeeding 2012 Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 177:1, s. 120-127 Tidskriftsartikel (refereegranskat)abstract In fish, recent studies have indicated an anorexigenic role of leptin and thus its possible involvement in regulation of energy balance and growth. In the present study, the effects of fasting and refeeding periods on plasma leptin levels were studied in the fine flounder, a flatfish with remarkably slow growth. To further assess the endocrine status of the fish during periods of catabolism and anabolism, plasma growth hormone (GH) levels were also analyzed. Under normal feeding condition, plasma leptin and CH levels remained stable and relatively high in comparison with other teleost species. For the three separate groups of fish, fasted for 2, 3, and 4 weeks, respectively, plasma leptin levels increase gradually, becoming significantly elevated after 3 weeks, and reaching highest levels after 4-week fasting. Plasma GH levels were significantly elevated after 2-week fasting. At the onset of refeeding, following a single meal, leptin levels decline rapidly to lower than initial levels within 2 h, irrespective of the length of fasting. Plasma GH also decline, the decrease being significant after 4, 24 and 2 h for the 2, 3 and 4-week fasted groups, respectively. This study shows that plasma leptin levels in the fine flounder are strongly linked to nutritional status and suggests that leptin secretion is regulated by fast-acting mechanisms. Elevated leptin levels in fasted fish may contribute to a passive survival strategy of species which experience natural food shortage periods by lowering appetite and limiting physical foraging activity. (C) 2012 Elsevier Inc. All rights reserved.
49.	Fuentes, E. N., et al. (författare) Regulation of skeletal muscle growth in fish by the growth hormone - Insulin-like growth factor system 2013 Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 192, s. 136-148 Tidskriftsartikel (refereegranskat)abstract The growth hormone (GH)-insulin-like growth factor (IGF) system is the key promoter of growth in vertebrates; however, how this system modulates muscle mass in fish is just recently becoming elucidated. In fish, the GH induces muscle growth by modulating the expression of several genes belonging to the myostatin (MSTN), atrophy, GH, and IGF systems as well as myogenic regulatory factors (MRFs). The GH controls the expression of igf1 via Janus kinase 2 (JAK2)/signal transducers and activators of the transcription 5 (STAT5) signaling pathway, but it seems that it is not the major regulator. These mild effects of the GH on igf1 expression in fish muscle seem to be related with the presence of higher contents of truncated GH receptor1 (tGHR1) than full length GHR (flGHR1). IGFs in fish stimulate myogenic cell proliferation, differentiation, and protein synthesis through the MAPK/ERK and PI3K/AKT/TOR signaling pathways, concomitant with abolishing protein degradation and atrophy via the PI3K/AKT/FOXO signaling pathway. Besides these signaling pathways control the expression of several genes belonging to the atrophy and IGF systems. Particularly, IGFs and amino acid control the expression of igf1, thus, suggesting other of alternative signaling pathways regulating the transcription of this growth factor. The possible role of IGF binding proteins (IGFBPs) and the contribution of muscle-derived versus hepatic-produced IGF1 on fish muscle growth is also addressed. Thus, a comprehensive overview on the GH-IGF system regulating fish skeletal muscle growth is presented, as well as perspectives for future research in this field.
50.	Fuentes, E. N., et al. (författare) The TORC1/P70S6K and TORC1/4EBP1 signaling pathways have a stronger contribution on skeletal muscle growth than MAPK/ERK in an early vertebrate: Differential involvement of the IGF system and atrogenes 2015 Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 210, s. 96-106 Tidskriftsartikel (refereegranskat)abstract Knowledge about the underlying mechanisms, particularly the signaling pathways that account for muscle growth in vivo in early vertebrates is still scarce. Fish (Paralichthys adspersus) were fasted for 3 weeks to induce a catabolic period of strong muscle atrophy. Subsequently, fish were refed for 2 weeks to induce compensatory muscle hypertrophy. During refeeding, the fish were treated daily with either rapamycin (TORC blocker), P098059 (MEK blocker), or PBS (V; vehicle), or were untreated (C; control). Rapamycin and P098059 differentially impaired muscle cellularity in vivo, growth performance, and the expression of growth-related genes, and the inhibition of TORC1 had a greater impact on fish muscle growth than the inhibition of MAPK. Blocking TORC1 inhibited the phosphorylation of P70S6K and 4EBP1, two downstream components activated by TORC1, thus affecting protein contents in muscle. Concomitantly, the gene expression in muscle of igf-1, 2 and igfbp-4, 5 was down-regulated while the expression of atrogin-1, murf-1, and igfbp-2, 3 was up-regulated. Muscle hypertrophy was abolished and muscle atrophy was promoted, which finally affected body weight. TORC2 complex was not affected by rapamycin. On the other hand, the PD98059 treatment triggered ERK inactivation, a downstream component activated by MEK. mRNA contents of igf-1 in muscle were down-regulated, and muscle hypertrophy was partially impaired. The present study provides the first direct data on the in vivo contribution of TORC1/P70S6K, TORC1/4EBP1, and MAPK/ERK signaling pathways in the skeletal muscle of an earlier vertebrate, and highlights the transcendental role of TORC1 in growth from the cellular to organism level. (C) 2014 Elsevier Inc. All rights reserved.

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