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| 2. |
- Bowman, Jennifer, et al.
(författare)
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Non-invasive recording of brain function in rainbow trout: Evaluations of the effects of MS-222 anaesthesia induction
- 2019
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Ingår i: Aquaculture Research. - : Hindawi Limited. - 1355-557X .- 1365-2109. ; 50:11, s. 3420-3428
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Tidskriftsartikel (refereegranskat)abstract
- Effective methods of producing instantaneous and irreversible unconsciousness at the time of slaughter are crucial for ensuring animal welfare in commercial aquaculture. However, the traditional method of visually evaluating unconsciousness has been shown to be insufficient and may lead to misjudgements of stunning efficiency. In this study, we developed a non-invasive technique that measures brain activity in fish as an alternative to traditional invasive, brain implants and used it to determine when a change in consciousness occurs in trout during anaesthesia induction. Nine rainbow trout (Oncorhynchus mykiss) were equipped with a custom designed silicone cup fitted with electrodes and submerged in 10 degrees C water with dissolved MS-222. During anaesthesia, the state of consciousness was assessed by recordings of electroencephalogram (EEG). The EEG recordings were analysed both by visually evoked responses from light stimulation (VERs) and from changes in signal amplitude, median frequency and relative signal power. According to the loss of VERs and decrease in signal amplitude, trout transitioned to surgical depth of anaesthesia within 5 min. Our results show that consciousness, or loss of, can be determined using a non-invasive system to record EEG in fish.
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| 4. |
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| 5. |
- Brijs, Jeroen, et al.
(författare)
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Cardiorespiratory upregulation during seawater acclimation in rainbow trout: effects on gastrointestinal perfusion and postprandial responses
- 2016
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Ingår i: American Journal of Physiology-Regulatory Integrative and Comparative Physiology. - : American Physiological Society. - 0363-6119 .- 1522-1490. ; 310:9
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Tidskriftsartikel (refereegranskat)abstract
- Increased gastrointestinal blood flow is essential for euryhaline fishes to maintain osmotic homeostasis during the initial phase of a transition from freshwater to seawater. However, the cardiorespiratory responses and hemodynamic changes required for a successful long-term transition to seawater remain largely unknown. In the present study, we simultaneously measured oxygen consumption rate ((M)over dot(O2)), cardiac output (CO), heart rate (HR), and gastrointestinal blood flow (GBF) in rainbow trout (Oncorhynchus mykiss) acclimated to either freshwater or seawater for at least 6 wk. Seawater-acclimated trout displayed significantly elevated ((M)over dot(O2)) (day: 18%, night: 19%), CO (day: 22%, night: 48%), and GBF (day: 96%, night: 147%), demonstrating that an overall cardiorespiratory upregulation occurs during seawater acclimation. The elevated GBF was achieved via a combination of increased CO, mediated through elevated stroke volume (SV), and a redistribution of blood flow to the gastrointestinal tract. Interestingly, virtually all of the increase in CO of seawater-acclimated trout was directed to the gastrointestinal tract. Although unfed seawater-acclimated trout displayed substantially elevated cardiorespiratory activity, the ingestion of a meal resulted in a similar specific dynamic action (SDA) and postprandial GBF response as in freshwater-acclimated fish. This indicates that the capacity for the transportation of absorbed nutrients, gastrointestinal tissue oxygen delivery, and acid-base regulation is maintained during digestion in seawater. The novel findings presented in this study clearly demonstrate that euryhaline fish upregulate cardiovascular function when in seawater, while retaining sufficient capacity for the metabolic and cardiovascular changes associated with the postprandial response.
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| 7. |
- Brijs, Jeroen, et al.
(författare)
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Experimental manipulations of tissue oxygen supply do not affect warming tolerance of European perch
- 2015
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 218, s. 2448-2454
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Tidskriftsartikel (refereegranskat)abstract
- A progressive inability of the cardiorespiratory system to maintain systemic oxygen supply at elevated temperatures has been suggested to reduce aerobic scope and the upper thermal limit of aquatic ectotherms. However, few studies have directly investigated the dependence of thermal limits on oxygen transport capacity. By manipulating oxygen availability (via environmental hyperoxia) and blood oxygen carrying capacity (via experimentally-induced anemia) in European perch (Perca fluviatilis, Linneaus), we investigated the effects of oxygen transport capacity on aerobic scope and the critical thermal maximum (CTmax). Hyperoxia resulted in a two-fold increase in aerobic scope at the control temperature of 23°C, but this did not translate to an elevated CTmax in comparison with control fish (34.6±0.1°C vs. 34.0±0.5°C, respectively). Anemia (∼43% reduction in haemoglobin concentration) did not cause a reduction in aerobic scope nor CTmax (33.8±0.3°C) compared with control fish. Additionally, oxygen consumption rates of anemic perch during thermal ramping increased in a similar exponential manner as in control fish, highlighting that perch have an impressive capacity to compensate for a substantial reduction in blood oxygen carrying capacity. Taken together, these results indicate that oxygen limitation is not a universal mechanism determining the CTmax of fishes.
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| 8. |
- Brijs, Jeroen, et al.
(författare)
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Exposure to seawater increases intestinal motility in euryhaline rainbow trout (Oncorhynchus mykiss).
- 2017
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Ingår i: The Journal of experimental biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 220, s. 2397-2408
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Tidskriftsartikel (refereegranskat)abstract
- Upon exposure to seawater, euryhaline teleosts need to imbibe and desalinate seawater to allow for intestinal ion and water absorption, as this is essential for maintaining osmotic homeostasis. Despite the potential benefits of increased mixing and transport of imbibed water for increasing the efficiency of absorptive processes, the effect of water salinity on intestinal motility in teleosts remains unexplored. By qualitatively and quantitatively describing in vivo intestinal motility of euryhaline rainbow trout (Oncorhynchus mykiss), this study demonstrates that in freshwater, the most common motility pattern consisted of clusters of rhythmic, posteriorly propagating contractions that lasted ∼1-2 minutes followed by a period of quiescence lasting ∼4-5 minutes. This pattern closely resembles mammalian migrating motor complexes (MMCs). Following a transition to seawater, imbibed seawater resulted in a significant distension of the intestine and the frequency of MMCs increased two to three-fold with a concomitant reduction in the periods of quiescence. The increased frequency of MMCs was also accompanied by ripple-type contractions occuring every 12 to 60 seconds. These findings demonstrate that intestinal contractile activity of euryhaline teleosts is dramatically increased upon exposure to seawater, which is likely part of the overall response for maintaining osmotic homeostasis as increased drinking and mechanical perturbation of fluids is necessary to optimize intestinal ion and water absorption. Finally, the temporal response of intestinal motility in rainbow trout transitioning from freshwater to seawater coincides with previously documented physiological modifications associated with osmoregulation and may provide further insight on the underlying reasons shaping the migration patterns of salmonids.
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| 9. |
- Brijs, J., et al.
(författare)
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In vivo aerobic metabolism of the rainbow trout gut and the effects of an acute temperature increase and stress event
- 2018
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 221:14
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Tidskriftsartikel (refereegranskat)abstract
- The fish gut is responsible for numerous potentially energetically costly processes, yet little is known about its metabolism. Here, we provide the first in vivo measurements of aerobic metabolism of the gut in a teleost fish by measuring gut blood flow, as well as arterial and portal venous oxygen content. At 10 degrees C, gut oxygen uptake rate was 4.3 +/- 0.5 ml O-2 h(-1) kg(-1) (similar to 11 % of whole-animal oxygen uptake). Following acute warming to 15 degrees C, gut blood flow increased similar to 3.4-fold and gut oxygen uptake rate increased similar to 3.7-fold (16.0 +/- 3.3 ml O-2 h(-1) kg(-1)), now representing similar to 25% of whole-animal oxygen uptake. Although gut blood flow decreased following an acute stress event at 15 degrees C, gut oxygen uptake remained unchanged as a result of a similar to 2-fold increase in oxygen extraction. The high metabolic thermal sensitivity of the gut could have important implications for the overall aerobic capacity and performance of fish in a warming world and warrants further investigation.
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| 10. |
- Brijs, Jeroen, et al.
(författare)
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Increased gastrointestinal blood flow: An essential circulatory modification for euryhaline rainbow trout (Oncorhynchus mykiss) migrating to sea
- 2015
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- The large-scale migrations of anadromous fish species from freshwater to seawater have long been considered particularly enigmatic, as this life history necessitates potentially energetically costly changes in behaviour and physiology. A significant knowledge gap concerns the integral role of cardiovascular responses, which directly link many of the well-documented adaptations (i.e. through oxygen delivery, water and ion transport) allowing fish to maintain osmotic homeostasis in the sea. Using long-term recordings of cardiorespiratory variables and a novel method for examining drinking dynamics, we show that euryhaline rainbow trout (Oncorhynchus mykiss) initiate drinking long before the surrounding environment reaches full seawater salinity (30–33ppt), suggesting the presence of an external osmo-sensing mechanism. Onset of drinking was followed by a delayed, yet substantial increase in gastrointestinal blood flow through increased pulse volume exclusively, as heart rate remained unchanged. While seawater entry did not affect whole animal energy expenditure, enhanced gastrointestinal perfusion represents a mechanism crucial for ion and water absorption, as well as possibly increasing local gastrointestinal oxygen supply. Collectively, these modifications are essential for anadromous fish to maintain homeostasis at sea, whilst conserving cardiac and metabolic scope for activities directly contributing to fitness and reproductive success.
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