| 1. |
- 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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| 2. |
- Ekström, Andreas, 1979, et al.
(författare)
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Cardiac oxygen limitation during an acute thermal challenge in the European perch: Effects of chronic environmental warming and experimental hyperoxia
- 2016
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Ingår i: American Journal of Physiology. Regulatory Integrative and Comparative Physiology. - : American Physiological Society. - 0363-6119 .- 1522-1490. ; 311:2
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Tidskriftsartikel (refereegranskat)abstract
- Oxygen supply to the heart has been hypothesized to limit cardiac performance and whole animal acute thermal tolerance (CTmax) in fish. We tested these hypotheses by continuously measuring venous oxygen tension (PvO2) and cardiovascular variables in vivo during acute warming in European perch (Perca fluviatilis) from a reference area during summer (18°C) and a chronically heated area (Biotest enclosure) that receives warm effluent water from a nuclear power plant and is normally 5–10°C above ambient (24°C at the time of experiments). While CTmax was 2.2°C higher in Biotest compared with reference perch, the peaks in cardiac output and heart rate prior to CTmax occurred at statistically similar PvO2 values (2.3– 4.0 kPa), suggesting that cardiac failure occurred at a common critical PvO2 threshold. Environmental hyperoxia (200% air saturation) increased PvO2 across temperatures in reference fish, but heart rate still declined at a similar temperature. CTmax of reference fish increased slightly (by 0.9°C) in hyperoxia, but remained significantly lower than in Biotest fish despite an improved cardiac output due to an elevated stroke volume. Thus, while cardiac oxygen supply appears critical to elevate stroke volume at high temperatures, oxygen limitation may not explain the bradycardia and arrhythmia that occur prior to CTmax. Acute thermal tolerance and its thermal plasticity can, therefore, only be partially attributed to cardiac failure from myocardial oxygen limitations, and likely involves limiting factors on multiple organizational levels. © 2016 the American Physiological Society.
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| 3. |
- Ekström, Andreas, 1979, et al.
(författare)
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Chronic environmental warming alters cardiovascular and haematological stress responses in European perch (Perca fluviatilis)
- 2016
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Ingår i: Journal of Comparative Physiology B-Biochemical Systemic and Environmental Physiology. - : Springer Science and Business Media LLC. - 0174-1578 .- 1432-136X. ; 186:8, s. 1023-1031
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Tidskriftsartikel (refereegranskat)abstract
- Environmental warming and acute stress increase cardiorespiratory activity in ectothermic animals like fish. While thermal acclimation can buffer the direct thermal effects on basal cardiorespiratory function during chronic warming, little is known about how acclimation affects stress-induced cardiorespiratory responses. We compared cardiovascular and haematological responses to chasing stress in cannulated wild European perch (Perca fluviatilis) from a reference area at natural temperature (16 A degrees C) with perch from the 'Biotest enclosure'; an experimental system chronically warmed (22 A degrees C) by effluents from a nuclear power plant. Routine blood pressure was similar, but Biotest perch had slightly higher resting heart rate (59.9 +/- 2.8 vs 51.3 +/- 2.9 beats min(-1)), although the Q (10) for heart rate was 1.3, indicating pronounced thermal compensation. Chasing stress caused hypertension and a delayed tachycardia in both groups, but the maximum heart rate increase was 2.5-fold greater in Biotest fish (43.3 +/- 4.3 vs 16.9 +/- 2.7 beats min(-1)). Moreover, the pulse pressure response after stress was greater in reference fish, possibly due to the less pronounced tachycardia or a greater ventricular pressure generating capacity and thermally mediated differences in aortic compliance. Baseline haematological status was also similar, but after chasing stress, the haematocrit was higher in Biotest fish due to exacerbated red blood cell swelling. This study highlights that while eurythermal fishes can greatly compensate routine cardiorespiratory functions through acclimation processes, stress-induced responses may still differ markedly. This knowledge is essential when utilising cardiorespiratory variables to quantify and compare stress responses across environmental temperatures, and to forecast energetic costs and physiological constraints in ectothermic animals under global warming.
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| 4. |
- Ekström, Andreas, 1979, et al.
(författare)
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Dynamic changes in scope for heart rate and cardiac autonomic control during warm acclimation in rainbow trout
- 2016
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 219:8, s. 1106-1109
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Tidskriftsartikel (refereegranskat)abstract
- Time course studies are critical for understanding regulatory mechanisms and temporal constraints in ectothermic animals acclimating to warmer temperatures. Therefore, we investigated the dynamics of heart rate and its neuro-humoral control in rainbow trout (Onchorhynchus mykiss L.) acclimating to 16 degrees C for 39 days after being acutely warmed from 9 degrees C. Resting heart rate was 39 beats min(-1) at 9 degrees C, and increased significantly when fish were acutely warmed to 16 degrees C (Q(10)=1.9), but then declined during acclimation (Q(10)=1.2 at day 39), mainly due to increased cholinergic inhibition while the intrinsic heart rate and adrenergic tone were little affected. Maximum heart rate also increased with warming, although a partial modest decrease occurred during the acclimation period. Consequently, heart rate scope exhibited a complex pattern with an initial increase with acute warming, followed by a steep decline and then a subsequent increase, which was primarily explained by cholinergic inhibition of resting heart rate.
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| 5. |
- Sandblom, Erik, 1978, et al.
(författare)
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Cardiac reflexes in awarming world: Thermal plasticity of barostatic control and autonomic tones in a temperate fish
- 2016
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 219:18, s. 2880-2887
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Tidskriftsartikel (refereegranskat)abstract
- Thermal plasticity of cardiorespiratory function allows ectotherms like fish to cope with seasonal temperature changes and is critical for resilience to climate change. Yet, the chronic thermal effects on cardiovascular homeostatic reflexes in fish are little understood although this may have important implications for physiological performance and overall resilience to climate warming.We compared cardiac autonomic control and baroreflex regulation of heart rate in perch (Perca fluviatilis L.) from a reference area in the Baltic Sea at 18-19C with conspecifics from the Biotest enclosure, a chronically heated ecosystem receiving warmed effluent water (24-25C) from a nuclear power plant. Resting heart rate of Biotest fish displayed clear thermal compensation and was 58.3±2.3 beats min-1 compared with 52.4±2.6 beats min-1 in reference fish at their respective environmental temperatures (Q10=1.2). The thermally compensated heart rate of Biotest fish was a combined effect of elevated inhibitory cholinergic tone (105% in Biotest fish versus 70% in reference fish) and reduced intrinsic cardiac pacemaker rate. A barostatic response was evident in both groups, as pharmacologically induced increases and decreases in blood pressure resulted in atropine-sensitive bradycardia and tachycardia, respectively. Yet, the tachycardia in Biotest fish was significantly greater, presumably due to the larger scope for vagal release. Acclimation of Biotest fish to 18C for 3 weeks abolished differences in intrinsic heart rate and autonomic tone, suggesting considerable short-term thermal plasticity of cardiovascular control in this species. The heightened hypotensive tachycardia in Biotest perch may represent an important mechanism of ectothermic vertebrates that safeguards tissue perfusion pressure when tissue oxygen demand is elevated by environmental warming. © 2016. Published by The Company of Biologists Ltd.
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| 6. |
- Sandblom, Erik, 1978, et al.
(författare)
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Physiological constraints to climate warming in fish follow principles of plastic floors and concrete ceilings
- 2016
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the resilience of aquatic ectothermic animals to climate warming has been hindered by the absence of experimental systems experiencing warming across relevant timescales (for example, decades). Here, we examine European perch (Perca fluviatilis, L.) from the Biotest enclosure, a unique coastal ecosystem that maintains natural thermal fluctuations but has been warmed by 5-10 degrees C by a nuclear power plant for over three decades. We show that Biotest perch grow faster and display thermally compensated resting cardiorespiratory functions compared with reference perch living at natural temperatures in adjacent waters. However, maximum cardiorespiratory capacities and heat tolerance limits exhibit limited or no thermal compensation when compared with acutely heated reference perch. We propose that while basal energy requirements and resting cardiorespiratory functions (floors) are thermally plastic, maximum capacities and upper critical heat limits (ceilings) are much less flexible and thus will limit the adaptive capacity of fishes in a warming climate.
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| 7. |
- Vadeby, Anna, 1969-, et al.
(författare)
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Säker framkomlighet : sammanfattande slutrapport 2015
- 2016
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Föreliggande rapport redovisar övergripande resultat av fyra olika åtgärder som implementerats inomTrafikverkets projekt ”Säker framkomlighet” vilket haft som syfte att förbättra framkomlighet ochtrafiksäkerhet på främst befintliga tvåfältsvägar med hastighetsgräns 90 km/tim. Åtgärderna somstuderats är: frästa mitträfflor på 2-fältsvägar, vägrensräffling på motorväg, smala mötesfria vägar(”gles 2+1-väg med räcke”) och riktningsseparerade vägar (2+1 med målad/räfflad mitt).Resultaten visar att för samtliga åtgärder har trafiksäkerhetseffekterna varit positiva med minskningarav de dödade och svårt skadade trafikanterna. Vad gäller spårdjupstillväxt visar resultaten att mitträfflinginte har en kanaliserande effekt på trafiken och därmed påverkas inte heller spårbildningen.För mötesfria vägar är den årliga spårdjupsutvecklingen cirka 25 procent högre för mötesfri väg än förmotsvarande vanlig väg för årsdygnstrafik (ÅDT) > 8 000 fordon/dygn. För lägre ÅDT är skillnaden 10–15 procent.För riktningsseparerade vägar visar resultaten endast på högre spårdjupstillväxt för ÅDT över 8 000fordon/dygn. En studie om effekter och konsekvenser av olika räffeltyper avseende buller visar att detinte finns kända argument för att inte använda sinusräffla, men ytterligare studier kring effekten förförare av tunga fordon rekommenderas. Studien avseende framkomlighetseffekter visar att andelentung trafik är en viktig faktor att beakta i utformningen av mötesfria vägar.
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