| 1. |
- McArley, Tristan J., et al.
(författare)
-
Experimental hyperoxia (O-2 supersaturation) reveals a gill diffusion limitation of maximum aerobic performance in fish
- 2022
-
Ingår i: Biology Letters. - : The Royal Society. - 1744-9561 .- 1744-957X. ; 18:11
-
Tidskriftsartikel (refereegranskat)abstract
- Several studies have demonstrated that hyperoxia increases the maximal O-2 consumption rate (<(M) over dot>O-2max) in fish, but exactly how this occurs remains to be explained. Here, we tested the hypothesis that hyperoxia improves arterial oxygenation in rainbow trout during exhaustive exercise. We demonstrate a 35% higher <(M) over dot>O-2max in hyperoxia (200% air saturation) relative to normoxia, which was achieved through a combined 15% increase in cardiac output due to elevated peak heart rate, and a 19% increase of the arterial-venous (A-V) O-2 content difference. While arterial O-2 partial pressure (PaO2) and O-2 saturation of haemoglobin declined post-exhaustive exercise in normoxia, this did not occur in hyperoxia. This protective effect of hyperoxia on arterial oxygenation led to a 22% higher arterial O-2 content post-exhaustive exercise, thereby allowing a higher A-V O-2 content difference. These findings indicate that <(M) over dot>O-2max is gill diffusion limited in exhaustively exercised rainbow trout. Moreover, as previous studies in salmonids have demonstrated collapsing PaO2 in normoxia at maximal swimming speed and at acutely high temperatures, a diffusion limitation may constrain <(M) over dot>O-2 in other situations eliciting peak metabolic demand. These findings, along with the fact that hyperoxia increases <(M) over dot>O-2max in several other fishes, suggest that gill diffusion limitations of <(M) over dot>O-2max may be widespread in fishes.
|
|
| 2. |
- McArley, Tristan J., et al.
(författare)
-
Normoxic limitation of maximal oxygen consumption rate, aerobic scope and cardiac performance in exhaustively exercised rainbow trout (Oncorhynchus mykiss)
- 2021
-
Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 224:15
-
Tidskriftsartikel (refereegranskat)abstract
- In fish, maximum O-2 consumption rate ((M) over dot(O2,max)) and aerobic scope can be expanded following exhaustive exercise in hyperoxia; however, the mechanisms explaining this are yet to be identified. Here, in exhaustively exercised rainbow trout (Oncorhynchus mykiss), we assessed the influence of hyperoxia on (M) over dot(O2,max), aerobic scope, cardiac function and blood parameters to address this knowledge gap. Relative to normoxia, (M) over dot(O2,max) was 33% higher under hyperoxia, and this drove a similar increase in aerobic scope. Cardiac output was significantly elevated under hyperoxia at (M) over dot(O2,max) because of increased stroke volume, indicating that hyperoxia released a constraint on cardiac contractility apparent with normoxia. Thus, hyperoxia improved maximal cardiac performance, thereby enhancing tissue O-2 delivery and allowing a higher (M) over dot(O2,max) Venous blood O-2 partial pressure (PvO(2)) was elevated in hyperoxia at (M) over dot(O2,max), suggesting a contribution of improved luminal O-2 supply in enhanced cardiac contractility. Additionally, despite reduced haemoglobin and higher PvO(2), hyperoxia treated fish retained a higher arterio-venous O-2 content difference at (M) over dot(O2,max). This may have been possible because of hyperoxia offsetting declines in arterial oxygenation that are known to occur following exhaustive exercise in normoxia. If this occurs, increased contractility at (M) over dot(O2,max) with hyperoxia may also relate to an improved O-2 supply to the compact myocardium via the coronary artery. Our findings show (M) over dot(O2,max) and aerobic scope may be limited in normoxia following exhaustive exercise as a result of constrained maximal cardiac performance and highlight the need to further examine whether or not exhaustive exercise protocols are suitable for eliciting (M) over dot(O2,max) and estimating aerobic scope in rainbow trout.
|
|
| 3. |
- Mendoza, P., et al.
(författare)
-
Starch and fiber intake effects on energy metabolism, growth, and carapacial scute pyramiding of red-footed tortoise hatchlings (Chelonoidis carbonaria)
- 2022
-
Ingår i: Comparative Biochemistry and Physiology a-Molecular & Integrative Physiology. - : Elsevier BV. - 1095-6433. ; 265
-
Tidskriftsartikel (refereegranskat)abstract
- Tortoise husbandry includes reports of excessive growth and carapace pyramiding, although triggers still remain to be fully elucidated. Juvenile red-footed tortoises (Chelonoidis carbonaria) were fed with two different diets, one high in fiber (HF; 14.2% crude fiber; 39.2% neutral detergent fiber, NDF; dry matter basis, DMB) and one high in starch (HS; 27.7% DMB), to assess effects on energy metabolism, nutrient digestibility, and growth. A total of 20 hatchlings (10 per diet) were used to evaluate: apparent digestibility coefficients (Da) of nutrients and gross energy (GE), passage times at 5 and 11 months of age; resting and post-prandial metabolic rates at 6 and 12 months of age; growth rates; pyramiding; and estimated body composition. Animals fed HS showed higher mass-specific intake of digestible energy (113.9 +/- 32.1 kJ kg(-1) day(-1) vs. 99.6 +/- 35.3 kJ kg(-1) day(-1); P < 0.05), digestible DM (6.1 +/- 1.8 g kg(-1) day(-1) vs. 5.0 +/- 1.8 g kg(-1) day(-1); P < 0.01), shorter transit (3 +/- 1 days vs. 4 +/- 1 days; P < 0.01) and retention times (8 +/- 2 days vs. 10 +/- 2 days; P < 0.01), and higher Da of DM, starch, NDF, and GE. Crude protein Da was higher for HF. Rest and post-prandial metabolic rates, and pyramiding degree were not affected by diets. At 13 months, the animals from HS presented wider plastrons and carapaces, and higher carapace width growth rates. In addition, these animals had lower body mineral content (1.88 +/- 0.15% vs. 2.15 +/- 0.19%; P < 0.01) and bone density (0.13 +/- 0.01 g mm(-2) vs. 0.15 +/- 0.02 g mm(-2); P < 0.02). Results provide evidence that highly digestible foods can accelerate shell growth and lower mineralization in this species.
|
|
| 4. |
- Mendoza, P., et al.
(författare)
-
Temperature effects on metabolism and energy requirement during the fast growth phase in the red-footed tortoise, Chelonoidis carbonaria
- 2023
-
Ingår i: Journal of Comparative Physiology B-Biochemical Systems and Environmental Physiology. - 0174-1578. ; 193:6, s. 661-676
-
Tidskriftsartikel (refereegranskat)abstract
- Early life is a challenging phase because of the high rates of morphophysiological development and growth. Changes in ambient temperature, which directly affect energy metabolism and digestive functions in ectotherms, may be of great impact during this phase. We addressed this issue in red-footed tortoise (Chelonoidis carbonaria) hatchlings kept in captivity. To this end, we investigated the effect of temperature (28 degrees C and 18 degrees C) on mass-specific gross energy intake ( GEI(m)), daily body mass gain (MG), daily intake of gross energy (GEI), digestible energy (DEI), resting metabolic rate (RMR), and specific dynamic action (SDA) components during different seasons in the first 13 months after hatching. Greater GEI(m) and MG were observed in spring (381.7 +/- 84.9 J.g(-0.86).day(-1) and 0.9 +/- 0.4 g.day(-1)) and summer (356.9 +/- 58.9 J.g(-0.86).day(-1) and 1.0 +/- 0.4 g.day(-1)). The highest and lowest RMRs at 28 degrees C were observed in spring (36.4 +/- 5.1 kJ.kg(-1).day(-1)) and winter (22.4 +/- 6.2 kJ.kg(-1). day(-1)), respectively. Regardless season, hatchlings showed greater GEI and DEI, O-2 consumption, CO2 production, RMR, maximum metabolic rate after feeding (FMRMAX), and heat increment ( FMRMAX- RMR) at 28 degrees C compared to 18 degrees C. In addition, the significant body mass influence showed allometric exponents of 0.62 at 28 degrees C and 0.92 at 18 degrees C for RMR. Our results indicate an important effect of environmental temperature on energy requirements and utilization in C. carbonaria hatchlings, which is seasonally influenced even in this early phase of life.
|
|
| 5. |
|
|
| 6. |
- Wallbom, Nicklas, 1994, et al.
(författare)
-
Increased reliance on coronary perfusion for cardiorespiratory performance in seawater-acclimated rainbow trout
- 2023
-
Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 226:4
-
Tidskriftsartikel (refereegranskat)abstract
- Salmonid ventricles are composed of spongy and compact myocardium, the latter being perfused via a coronary circulation. Rainbow trout (Oncorhynchus mykiss) acclimated to sea water have higher proportions of compact myocardium and display stroke volume-mediated elevations in resting cardiac output relative to freshwater-acclimated trout, probably to meet the higher metabolic needs of osmoregulatory functions. Here, we tested the hypothesis that cardiorespiratory performance of rainbow trout in sea water is more dependent on coronary perfusion by assessing the effects of coronary ligation on cardiorespiratory function in resting and exhaustively exercised trout acclimated to fresh water or sea water. While ligation only had minor effects on resting cardiorespiratory function across salinities, cardiac function after chasing to exhaustion was impaired, presumably as a consequence of atrioventricular block. Ligation reduced maximum O2 consumption rate by 33% and 17% in fish acclimated to sea water and fresh water, respectively, which caused corresponding 41% and 17% reductions in aerobic scope. This was partly explained by different effects on cardiac performance, as maximum stroke volume was only significantly impaired by ligation in sea water, resulting in 38% lower maximum cardiac output in seawater compared with 28% in fresh water. The more pronounced effect on respiratory performance in sea water was presumably also explained by lower blood O2 carrying capacity, with ligated seawater-acclimated trout having 16% and 17% lower haemoglobin concentration and haematocrit, respectively, relative to ligated freshwater trout. In conclusion, we show that the coronary circulation allows seawater-acclimated trout to maintain aerobic scope at a level comparable to that in fresh water.
|
|
| 7. |
- Zena, Lucas, 1984, et al.
(författare)
-
Ischemia-induced alterations in the electrocardiogram of salmonid fish
- 2024
-
Ingår i: AQUACULTURE. - 0044-8486 .- 1873-5622. ; 581
-
Tidskriftsartikel (refereegranskat)abstract
- Cardiovascular diseases such as coronary arteriosclerosis are widespread and constitute severe health and welfare problems for both farmed and wild salmonid fish. However, effective tools for rapid screening and analysing heart diseases in fish do not currently exist. Electrocardiogram (ECG) recordings are widely used for screening and diagnosing numerous cardiac pathologies in humans, but the use of ECG techniques to diagnose and characterize cardiac abnormalities in fish is still in its infancy. In this study, we induced myocardial ischemia in anaesthetized rainbow trout by surgical coronary artery ligation. Additionally, we experimentally manipulated the fish's heart rate and environmental oxygen availability by altering gill water flow and oxygen saturation (i.e., no flow, normoxic flow and hyperoxic flow), and analyzed changes in the ECG profile in detail. The main ECG abnormalities observed in fish with ligated coronaries in normoxia were atrioventricular blocks, prolonged QRS duration, reduced QRS amplitude and changes in the ST-segment such as the presence of early repolarization pattern. Furthermore, when gill water flow was stopped, fish exhibited pronounced hypoxic bradycardia, which alleviated all ECG abnormalities in coronary ligated fish. This is the first study to provide a detailed characterization of electrocardiographic markers of myocardial ischemia in fish. Our study shows that hypoxic bradycardia improves cardiac electrical conductivity, presumably by reducing mismatches in myocardial oxygen supply and demand. Yet, the importance of avoiding hypoxic bradycardia in experimental and biomedical studies on anaesthetized fish is highlighted as it can potentially lead to incorrect ECG interpretations.
|
|
| 8. |
- Zena, Lucas, 1984, et al.
(författare)
-
It takes time to heal a broken heart: ventricular plasticity improves heart performance after myocardial infarction in rainbow trout, Oncorhynchus mykiss
- 2021
-
Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 224:23
-
Tidskriftsartikel (refereegranskat)abstract
- Coronary arteriosclerosis is a common feature of both wild and farmed salmonid fishes and may be linked to stress-induced cardiac pathologies. Yet, the plasticity and capacity for long-term myocardial restructuring and recovery following a restriction in coronary blood supply are unknown. Here, we analyzed the consequences of acute (3 days) and chronic ( from 33 to 62 days) coronary occlusion (i.e. coronary artery ligation) on cardiac morphological characteristics and in vivo function in juvenile rainbow trout, Oncorhynchus mykiss. Acute coronary artery occlusion resulted in elevated resting heart rate and decreased inter-beat variability, which are both markers of autonomic dysfunction following acute myocardial ischemia, along with severely reduced heart rate scope (maximum-resting heart rate) relative to sham-operated trout. We also observed a loss of myocardial interstitial collagen and compact myocardium. Following long-term coronary artery ligation, resting heart rate and heart rate scope normalized relative to sham-operated trout. Moreover, a distinct fibrous collagen layer separating the compact myocardium into two layers had formed. This may contribute to maintain ventricular integrity across the cardiac cycle or, alternatively, demark a region of the compact myocardium that continues to receive oxygen from the luminal venous blood. Taken together, we demonstrate that rainbow trout may cope with the aversive effects caused by coronary artery obstruction through plastic ventricular remodeling, which, at least in part, restores cardiac performance and myocardium oxygenation.
|
|
