| 1. |
- Ebbesson, Lars, et al.
(författare)
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Neural circuits and their structural and chemical reorganization in the light-brain-pituitary axis during parr-smolt transformation in salmon
- 2003
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Ingår i: Aquaculture. - 0044-8486. ; 222:1-4, s. 59-70
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Tidskriftsartikel (refereegranskat)abstract
- Salmonid parr-smolt transformation (smoltification) is a transitional stage between freshwater and seawater life when the salmon imprint on their natal stream, change from a territorial feeding behavior to downstream migration, increase their hypoosmoregulatory competence, and change body shape and coloration. Photoperiod is recognized as the most potent initiator and regulator of the smoltification processes. Environmental light signals giving information about photoperiod are conveyed through a light-brain-pituitary axis that encompasses the neural pathways between photoreceptor organs, the brain and the pituitary, and the diurnal rhythm in melatonin secretion by the photosensory pineal organ. In addition, changes in photoperiod may elicit changes in this axis. Employing retinal neural tract tracing and growth associated protein-43 (GAP-43) immunocytochemistry, we provide here new evidence of a structural reorganization in the light-brain-pituitary axis during smoltification. Retinal tract tracing revealed that projections in smolts expand into new territories of the ipsilateral nucleus preopticus parvocellularis pars anterior (PPa) and additional fibers invade deeper into the contralateral PPa and the nucleus preopticus magnocellularis (PM). At this time, GAP-43-immunoreactive cells appear transiently in specific cell groups throughout the brain, but mainly in the olfactory bulb, telencephalon, and hypothalamus. These structural changes in the light-brain-pituitary axis and hypophysiotropic systems are followed by sequential surges of brain neurotransmitters and receptors, and occur prior to the major surges of circulating thyroid hormone and growth hormone levels that are central to smoltification-related processes. Our data point to a specific period of structural reorganization in certain brain circuits, and we hypothesize that these are involved in triggering the subsequent behavioral, endocrine, and physiological changes associated with smoltification. (C) 2003 Published by Elsevier Science B.V.
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| 2. |
- 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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| 3. |
- 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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| 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
(författare)
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Temporal dynamics of brain and hormone changes during parr-smolt transformation in salmon
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis describes a series of studies designed to elucidate brain circuitry changes during parr-smolt transformation (smoltification) in salmon. The studies revealed sequential orderly chemical and structural changes of the brain. The first study showed sequential changes in concentration of mu-and kappa-opiate receptors in select cell groups of the brain during various stages of smoltification. Another study, using GAP-43 immunoreactivity, localized brain regions undergoing brain circuitry changes and showed that the timing of appearance of the transient immunoreactive cells and fibers preceded the principal plasma thyroid hormone surge. Moreover, the appearance of transient serotonin-immunoreactive neurons in the preoptic and habenular region of the brain coincide with the transient GAP-43 immunoreactivity. Those results led to investigations on the role of hormones in the observed neural plasticity. These studies led to the development of the method to measure free plasma thyroxine that gives a new perspective on the significance of the observed surges of thyroid hormones in plasma. The research also revealed relationships of thyroid hormones to growth hormone and melatonin. Other studies showed the relationship between daily and seasonal variation in plasma levels of thyroid hormones and growth hormones. A final study showed the effectiveness of propylthiouracil (PTU) in inducing hypothyroidism, reducing both thyroid hormone and growth hormone levels at the time of smoltification in salmon. Overall the studies of this thesis suggest that smoltification in salmon may be an important model for research on neural plasticity. The studies also provided new insights into the complex interaction of hormones during smoltification and their role in modification of the brain. The studies also showed that the brain likely plays important roles in the parr-smolt transformation.
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| 6. |
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| 7. |
- Moltesen, Maria, et al.
(författare)
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Cognitive appraisal of aversive stimulus differs between individuals with contrasting stress coping styles; evidences from selected rainbow trout (Oncorhynchus mykiss) strains
- 2016
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Ingår i: Behaviour. - 0005-7959 .- 1568-539X. ; 153:13-14, s. 1567-1587
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Tidskriftsartikel (refereegranskat)abstract
- In animals, personality variations in response to stress and energy demands have been established. Cognitive processing of negative stimuli correlates with stress response patterns. Still, the relative contribution of cognitive appraisal or physiological demands to the behavioural output needs to be clarified. In this study we utilized reactive (high-responsive, HR) and proactive (low-responsive, LR) rainbow trout strains to investigate how contrasting reactions to hypoxia are related to individual variation in metabolism and/or cognition. The HR-LR strains did not differ in standard metabolic rate or hypoxia tolerance. HR trout displayed more pronounced avoidance to a signal cue after being conditioned with hypoxia, suggesting that they experienced this stimulus more aversive than LR trout. Together with differences in forebrain c-fos activation patterns in dorsomedial pallium, these results suggest cognitive differences between the strains. These results demonstrate that differences in personality/stress coping style can be related to contrasts in cognition, which are independent of metabolic differences.
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| 8. |
- 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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| 9. |
- 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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| 10. |
- Stefansson, S. O., et al.
(författare)
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Molecular mechanisms of continuous light inhibition of Atlantic salmon parr–smolt transformation
- 2007
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Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486. ; 273:2-3, s. 235-245
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Tidskriftsartikel (refereegranskat)abstract
- Atlantic salmon (Salmo salar) rely on changes in photoperiod for the synchronization of the developmental events constituting the parr–smolt transformation. In the absence of photoperiod cues, parr–smolt transformation is incomplete, and such ‘pseudo-smolts’ normally fail to adapt to seawater. The present study addresses the endocrine and molecular mechanisms controlling the development of hypo-osmoregulatory ability and how artificial photoperiod can disrupt these changes. Juvenile Atlantic salmon reared under constant light (LL) from first feeding, were separated into two groups, and exposed to either LL or simulated natural photoperiod (LDN) from October, eight months prior to the expected completion of smoltification. Juveniles reared on LL grew well, but failed to show the smolt-related reduction in condition factor in spring. Gill mRNA levels of Na+, K+–ATPase (NKA) isoform α1a decreased in LDN fish through completion of parr–smolt transformation, while levels remained unchanged in the LL group. In contrast, α1b expression increased 6-fold in the LDN group between February and May, again with no change in the LL group. Further, Na+, K+, 2Cl− co-transporter (NKCC) showed a transient increase in expression in smolts on LDN between February and May, while no changes in mRNA levels were seen in juveniles under LL. Consequently, gill NKA activity and NKA α and NKCC protein abundance were significantly lower in juveniles on LL than in smolts on LDN. LL fish in spring had lower circulating levels of thyroid hormones (THs), growth hormone (GH) and cortisol. Gill GH-receptor mRNA levels, determined by quantitative PCR, were less than 50% of controls. In contrast, circulating levels of IGF-1 and gill IGF-1 receptor expression, were comparable to controls. Our findings show that continuous light prevents the completion of parr–smolt transformation at a very basic level, disrupting the natural up-regulation of key elements of the endocrine system involved in the regulation of the parr–smolt transformation, and consequently inhibiting the smoltification-related increase in expression, abundance and activity of gill ion transport proteins.
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| 11. |
- Stefansson, S. O., et al.
(författare)
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Smoltification
- 2008
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Ingår i: In “Fish Larval Physiology” (Finn A and Kapoor B, eds). - Enfield : Sci Publ. - 9781578083886 ; , s. 639-681
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 12. |
- Svane, Torben Ernst, 1953-, et al.
(författare)
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Enchanting education from student input : Preparing students to envision and develop in an Internet of Things world
- 2017
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Ingår i: Proceedings - Frontiers in Education Conference, FIE. - San Diego : IEEE. - 9781509059201 - 9781509049202 ; , s. 1-4
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Konferensbidrag (refereegranskat)abstract
- Searching for "The Internet of Things" may render thousands of hits in academic databases but a challenge still remains: to let students envision as well as work with the concept in a practical way. Designing "Things for the Internet" will not only require skills in engineering and electronics but also some understanding of digital service design and business models. This paper reports on work in progress between Belgium, Sweden and China. Students with different education backgrounds and levels hand over work (ideas) to others, to develop further. Currently, there are nine open-platform exercises to use as starting points for student work and discussions. Exercises are in English and free to download and use, as are some of the lectures related to them. So far, they are used in a digital service design class and in an introductory course in embedded systems. © 2017 IEEE.
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| 13. |
- Svane, Torben Ernst, 1953-, et al.
(författare)
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Like a snowball : Adding layers of knowledge Enchanting student work with student input
- 2017
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Ingår i: 2017 16th International Conference on Information Technology Based Higher Education and Training (ITHET). - : IEEE conference proceedings. - 9781538639689 - 9781538639696 - 9781538639672
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Konferensbidrag (refereegranskat)abstract
- Internet of Things (IoT) seems to be a popular term nowadays, for business, society and teaching alike. Teaching students about such concepts and more importantly, making them aware of the many competency components (often called KSA-knowledge, skills, abilities) required in the development of IoT systems, services and products has been a major aim in the teaching design presented in this paper. The snowball metaphor symbolizes added layers of input, comments and suggestions delivered by Belgian, Swedish and Chinese students respectively, to peers with different backgrounds (study level, subject major, etc.). Open-platform exercises using Arduino kits are used as starting points and reports. Conceptualizations and suggestions are carried through the snowball ’chain’, which ends nearly two years later. Knowledge components are delivered e.g. through lectures. Among skills developed are practice in receiving input from and delivering output to groups different also in culture, knowledge, etc. Abilities include a demonstrated (and graded) proficiency in combining the acquired set of components, as demonstrated in workshops, discussions and reports, and in a proposed feedback loop to Sweden from China (not yet implemented). © 2017 IEEE.
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| 14. |
- Vindas, Marco A., et al.
(författare)
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How do individuals cope with stress? : Behavioural, physiological and neuronal differences between proactive and reactive coping styles in fish
- 2017
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 220:8, s. 1524-1532
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Tidskriftsartikel (refereegranskat)abstract
- Despite the use of fish models to study human mental disorders and dysfunctions, knowledge of regional telencephalic responses in non-mammalian vertebrates expressing alternative stress coping styles is poor. As perception of salient stimuli associated with stress coping in mammals is mainly under forebrain limbic control, we tested region-specific forebrain neural (i.e. mRNA abundance and monoamine neurochemistry) and endocrine responses under basal and acute stress conditions for previously characterised proactive and reactive Atlantic salmon. Reactive fish showed a higher degree of the neurogenesis marker proliferating cell nuclear antigen (pcna) and dopamine activity under basal conditions in the proposed hippocampus homologue (Dl) and higher post-stress plasma cortisol levels. Proactive fish displayed higher post-stress serotonergic signalling (i.e. higher serotonergic activity and expression of the 5-HT1A receptor) in the proposed amygdala homologue (Dm), increased expression of the neuroplasticity marker brain-derived neurotropic factor (bdnf) in both Dl and the lateral septum homologue (Vv), as well as increased expression of the corticotropin releasing factor 1 (crf(1)) receptor in the Dl, in line with active coping neuro-profiles reported in the mammalian literature. We present novel evidence of proposed functional equivalences in the fish forebrain with mammalian limbic structures.
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