•Growth hormone (GH) is synthesized mainly in the pituitary gland.•The GH / IGF system interacts with the immune system.•We describe for the first time a direct stimulation of GH and GRF in two ...cellular models on some markers of immune response.•The TNF-a and IL-8 expression decreased with respect to the controls.•Our results are suggesting a modulation in the immune response by the GH/IGF axis in Atlantic salmon.
To clarify the role of growth hormone (GH) in the immune system of fish, we examine the comparative effect of GH and Growth Hormone Release Factor (GRF) on leukocytes culture of the head kidney of Atlantic salmon and the SHK-1 cell line. There are studies that associate the growth hormone (GH) / insulin-like growth factor (IGF) axis with the immune regulation of fish. However, there is no evidence that GH and GRF stimulate Atlantic salmon leukocyte cell lines, where there areńt reports on expression changes in different immune response markers. Thus, we investigated the effect of GH and GRF in Atlantic salmon leukocytes extracted from head kidney and the SHK-1 cell line on the different immune response markers such as: NLRC5, NLRC3, IL-1β, TNF-α, and IL-8 through qPCR. Our data suggest that GH increases the expression of NLRC5, NLRC3, and IL-1β mainly at 16 h post-stimulation in Atlantic salmon leukocytes. This indicates differential regulation between the two models used, helping us to better understand the independent action of GH on the immune system and the GH / IGF axis for future research.
Increased levels of tissue monoaminergic neurotransmitters, as well as circulating catecholamines, appear to play a role in the regulation of the physiological responses of teleost fish. Harpagifer ...antarcticus is a stenothermic, Antarctic notothenioid fish. The aim of this study was to determine the effect of increased seawater temperature and decreased salinity on the levels of 5-HT, 5-HIAA, DA, and Noradrenaline in the brain, stomach, and gut of H. antarcticus. Wild-gathered fish were acclimatized to habitat conditions (2 °C, 33 PSU) prior to placement in aquaria with 4 temperatures (2, 5, 8 and 11 °C) and 3 salinities (23, 28 and 33 PSU) for 10 days. Fish exposed to 11 °C had higher levels of the brain neurotransmitters than those at 2 °C. Concomitant exposure to low salinity exacerbated the effect of exposure to 11 °C. At lower temperatures, concomitant alterations in salinity induced differential effects on brain neurotransmitters. When fish were exposed to 28 PSU, 5-HIAA, DA, and Noradrenaline levels at 5 and 8 °C presented no significant differences with those at 2 °C. In contrast, only 5HT and 5-HIAA levels in fish at 33 PSU were elevated at 5 and 8 °C respectively. Fish at 28 and 33 PSU had lower Gut 5HT levels at the 3 elevated temperatures, meanwhile fish at 23 PSU showed a biphasic effect when exposed to elevated temperatures. 5-HIAA levels decreased at 5 and 8 °C at 33 PSU. Stomach 5HT levels also showed a differential response at the 3 salinity levels when exposed to increased temperatures. At 11 °C, 5HT levels were markedly higher than those at 2 °C for fish at 33 PSU, moderately elevated for fish at 28 PSU, and lower for fish at 23 PSU, meanwhile 5-HIAA levels only increased with temperature at 33 PSU. These findings indicate that rapid exposure to alterations in temperate with or without concomitant changes in salinity is associated with differential responses in tissue monoaminergic neurotransmitter levels. The relatively high changes in neurotransmitter levels in fish exposed to moderate salinity and high temperature changes may indicate the physiological plasticity of H. antarcticus to possible changes in ocean temperature and salinity.
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•Harpagifer antarcticus is a stenothermic, Antarctic notothenioid fish.•The aim was to determine the effect of high temperature and decreased salinity on neuroendocrine responses of H. antarcticus.•Concomitant exposure to low salinity exacerbated the effect of exposure to 11 °C.•Rapid exposure to alterations of sea water temperature is associated with differential responses in neurotransmitter levels.•To exposition at moderate salinity and high temperature changes may indicate the physiological plasticity of H. antarcticus.
•The aim was to elucidate the effects of exogenous cortisol on two fish.•Treatment with cortisol implants for 30 days resulted in reduced growth in both species.•Gill NKA activity was strongly ...upregulated by cortisol in Atlantic salmon but not in brook trout.•Our results demonstrate that there are species differences in the sensitivity to cortisol.
Cortisol is the final product of the hypothalamic-pituitary-interrenal (HPI) axis and acts as a gluco- and mineralo-corticoid in fish. Long-term elevations of cortisol have been linked to reduced growth in fishes, but the mechanism(s) and relative sensitivities of species are still unclear. We carried out experiments to examine the relative effects of cortisol on growth and gill NKA activity in two salmonids: Atlantic salmon (Salmo salar) and brook trout (Salvelinus fontinalis). Treatment with intraperitoneal cortisol implants for 30 days resulted in reduced growth in both species, but with greater sensitivity to cortisol in brook trout. Gill NKA activity was strongly upregulated by cortisol in Atlantic salmon, and weakly upregulated in brook trout but with no statistically significant effect. Cortisol treatment resulted in reduced plasma levels of insulin-like growth factor I and increased plasma growth hormone levels in Atlantic salmon. Our results demonstrate that there are species differences in the sensitivity of growth and osmoregulation to cortisol, even among species in the same family (Salmonidae).
Fluctuations in ambient temperature along with the presence of pathogenic microorganisms can induce important cellular changes that alter the homeostasis of ectothermic fish. The aim of this study ...was to evaluate how sudden or gradual changes in environmental temperature together with the administration of Piscirickettsia salmonis modulate the transcription of genes involved in cellular stress response in the liver of Eleginops maclovinus. Fish were subjected to the following experimental conditions in duplicate: C-12 °C: Injection only with culture medium, C+ 12 °C: Injection with P. salmonis, AM 18 °C: Injection only with culture medium under acclimation at 18 °C, AB 18 °C: Injection with P. salmonis under acclimation at 18 °C, SM 18 °C: Injection only with culture medium and thermal shock at 18 °C and SB 18 °C: Injection with P. salmonis and thermal shock at 18 °C and sampling at 4-, 8-, 12-, 16- and 20-day post injection (dpi). The genes implied in the heat shock response (HSP70, HSC70, HSP90, and GRP78), apoptosis pathway (BAX and SMAC/Diablo), ubiquitination (E2, E3, ubiquitin, and CHIP), and 26 proteasome complex (PSMB7, PSMC1, and PSMA2) showed expression profiles dependent on time and type of injection applied. All the genes greatly increased their expression levels at day 16 and showed moderate increases at day 20, except for PSMA2 which showed a higher increase between 4- and 12-day post challenges. Our results suggest that the changes observed at the final days of the experiment are due to temperature more than P. salmonis.
Oncorhynchus kisutch is the third most cultivated salmonid species in the Chilean salmon industry and its farming conditions are characterised by high stocking density leading to the generation of ...high levels of organic matter (food - feces) and decomposition. In addition to the increasingly frequent hypoxic oceanographic events, these inappropriate farming conditions increase the demand for oxygen within the fish farm pen and lead to the appearance of hypoxic events that are harmful to fish.This study aimed to evaluate the stress response (cortisol) and transcription of genes involved in the immune response in head kidney and spleen of Oncorhynchus kisutch subjected to chronic hypoxic stress conditions. The fish were exposed to 100%, 60%, 50%, 35%, and 25% of DO for 28 days, then the blood (plasma), head kidney and spleen were removed. We observed mortality in the 25% DO group at days 15 and 20. Plasma cortisol increased significantly under 35% and 25% DO conditions compared to control. Transcription of Toll-like receptors (TLR1, TLR5M, TLR8, and TLR9) and cytokines (IL-1β, IL6, IL10, TNF-α) increased in the head kidney only in the 50% DO group, while in spleen there was an increase of these markers in the conditions of 60%, 35%, and 25% DO. As for the markers involved in cell-mediated immunity, CD4-MHCII and CD8-MHCI do not have a clear expression pattern, although there was down-regulation in MHCII transcription in the head kidney, in all the hypoxia conditions evaluated. Finally, IgM transcription was increased in the spleen in all hypoxia conditions, although it wasn't always statistically significant compared to the control. These results indicate that chronic hypoxia induces the stress response, increasing plasma cortisol levels and modulating the transcription of genes involved in the innate and adaptive immune response. The expression patterns were tissue-specific, indicating that the degree of hypoxia differentially affects the transcription of genes involved in the immune response of Oncorhynchus kisutch.
1.Oncorhynchus kisutch is the third most cultivated salmonid species in the Chilean salmon industry.2.We evaluate the innate and adaptive immune response in coho salmon under hypoxia condition3.The expression patterns of genes involved in the immune response were tissue-specific in coho salmon under hypoxia.
Eleginops maclovinus is a native species with potential for Chilean aquaculture. Understanding the variations between the post-prandial and fasted metabolic responses can contribute to improving the ...aquaculture of this species. This study aimed to characterize variations in intermediate metabolism during the course of the day in the liver, serum, and gills of fed and unfed fish. For this, 72 fish were assigned to two experimental groups, “fed” and “fasted”. The first group was fed “ad libitum” at 8.30, while the fasted group was not fed for 24 h. Samples were taken from both groups at 9:00, and every 2 h: 11:00, 13:00, 15:00, 17:00, and 19:00. In the fed group, food spent a long time in the gastrointestinal tract, with a large increase in stomach size and without evidence of complete emptying of the stomach at 19:00 (10.5 h post-feeding). In serum, the levels of amino acids, glucose, and triglycerides presented significant differences with peak levels at different times of day in the fed group. The cortisol in the fasted group presented a diurnal pattern with high levels during the morning and very low levels after 13:00, while in the fed group, the high cortisol variability did not allow a clear pattern to be established. In the liver, the effect of time on the enzymatic activity of the intermediary metabolism was greater compared to the effect of feeding. In the liver, enzyme activity decreased at later hours of the day, while glycogen levels increased at later hours of the day in both groups: but its levels were higher in the fed group. In gills, as well as in the liver, time had a greater effect than feeding on intermediate metabolism, since feeding only had a significant effect on the levels of hexokinase, lactate, and amino acids, suggesting an effect on carbohydrate metabolism. Meanwhile, time significantly affected the levels of Na+, K+-ATPase, glutamate dehydrogenase, aspartate aminotransferase, amino acids, and proteins, suggesting an effect on amino acid metabolism. In conclusion, the intermediate metabolism of E. maclovinus presents variations according to the time of day, with an increased metabolism during the morning and decreased metabolism as the day progresses, especially at the hepatic level. The gill tissue, despite not being a metabolic organ, presents feeding-dependent variations in its metabolism. Additional studies will be required to corroborate if coordinating a feeding strategy during the first hours of the day when metabolism is greater would improve the growth of E. maclovinus.
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•Fed fish showed increases in plasma glucose, amino acids and triglycerides at different times of the day.•Hepatic intermediate metabolism was reduced throughout the day.•Plasma cortisol levels decreased in less than 2 h and became stable after 13:00.•Liver glycogen content increased throughout the day independent of food supply.
Cu, Mn, Fe, Zn, Cd and Pb levels were measured in liver and muscle samples of Rainbow Trout Oncorhynchus mykiss collected from three watersheds with different land-uses: native forest, exotic ...plantation, and agriculture in Chile, during January, April, July, and October 2012. Cd and Pb levels were not detected in the liver and muscle, probably since they are under the detection limits. Higher metal concentrations (liver-muscle tissues) were detected in samples from agriculture and exotic plantation streams, whereas trout from native forest streams had lower metal concentrations. Higher metal concentrations were detected in liver tissue compared to muscle tissue, and both negatively correlated to the length and weight of the fish. This suggest the liver had higher ability to accumulate Cu, Mn, Fe and Zn compared to muscle tissue. The concentration range of Fe and Zn recorded in the muscle are within the range reported by other authors, whereas Mn and Cu concentrations are higher than reported in the literature. However, at all sites the concentration of selected metals were below the limits permitted by current legislation (FAO), and therefore did not put the human population at risk, suggesting that is eating wild rainbow trout safe in Chile.
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•Higher heavy metal concentrations were observed in trout inhabiting streams of areas with agricultural and exotic plantations.•Higher concentrations were found in liver compared to muscle tissue.•Heavy metals concentrations in wild rainbow trout were lower the safe fish consumption limit.•O. mykiss can serve as biomonitors of the amount of heavy metals in the water environment.
In teleosts, peripheral serotonin (5-HT) and melatonin (MEL) are synthesised in the gastrointestinal tract (GIT) and regulate secretion and motility processes. Their production is regulated by diet ...and the passage of food through the GIT. This study aimed to evaluate how intestinal 5-HT, melatonin, and the activity of digestive enzymes varied with food passage time through GIT in Atlantic salmon (Salmo salar). We fed fish diets supplemented with tryptophan and melatonin (L-Trp 2.5% and MEL 0.01%) and measured the activity of digestive enzymes (amylase, lipase, and total protease) in the pyloric caeca, midgut, and hindgut at different times after feeding. 5-HT levels increased in all GIT portions and diets at 120 min post-intake and were highest in the pyloric caeca. Intestinal enzymatic activity was varied with diet, post-intake time and in different intestinal portions. In conclusion, food passage time directly affects GIT 5-HT secretion and digestive enzyme activity in S. salar, and diet composition regulates S. salar GIT function.
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•Peripheral serotonin and melatonin are implicated in gastrointestinal tract processes•Food passage of digesta directly affect GIT 5-HT content and digestive enzymes.•The MEL diet produced an inhibitory effect on digestive enzyme activity.
Francisella noatunensis subsp. noatunensis, the etiological agent of Francisellosis, affects a large number of farmed species such as Salmo salar. This species coexists with several native species in ...the same ecosystem, including Eleginops maclovinus. Our objective was to evaluate the susceptibility, presence of clinical symptoms, and the ability of Eleginops maclovinus to respond to Francisella infection. For this, healthy individuals were inoculated with 1.5 × 101, 1.5 × 105, and 1.5 × 1010 bact/μL of Francisella by intraperitoneal injection, subsequently the fish were sampled on days 1, 3, 7, 14, 21, and 28 post injection (dpi). At the end of the experiment, no mortality, nor internal and external clinical signs were observed, although in the high dose anaemia was detected. Additionally, bacteria were detected in all three doses, however there was replication at day 28 only in the liver in the high dose. Analysis of gene expression by qPCR showed that the spleen generated an immune response against infection from day 1 dpi, however at day 7 dpi most of the genes suffered repressed expression; observing over expression of the genes C3, NLRC3, NLRC5, MHCI, IgM. In contrast, expression in the anterior kidney did not vary significantly during the challenge. IgM quantification showed the production of antibodies in the medium and high doses. This study provides new knowledge about Francisella infection and the long-lasting and specific immune response generated by Eleginops maclovinus. It also demonstrates its susceptibility to Francisellosis where there is a difference in the immune response according to the tissue.
•Eleginops maclovinus is living in proximity to salmonid culture centers feeding off of uneaten pellet and salmonid feces.•The aim of this study was to evaluate the innate and adaptive immune responses of E. maclovinus challenged with Francisella noatunensis.•The results suggest activation of the immune response in E. maclovinus injected by distinct Francisella noatunensis doses.•This is the first immunological study to relate an emergent pathogen in salmonids with a native fish.
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