Fasting Fish Research Articles

Characterization, tissue distribution and regulation of neuropeptideY in Schizothorax prenanti.

In this study, the full-length neuropeptide Y (npy) complementary (c)DNA was cloned in ya fish Schizothorax prenanti. npy cDNA was composed of 789 nucleotides with a 288 nucleotide open reading frame encoding a protein of 96 amino acids. The deduced amino acid sequences contained a 28 amino acids signal peptide followed by a 36 amino acids mature neuropeptide Y (NPY). The npy mRNA was expressed mainly in the brain and eye as detected by real-time quantitative polymerase chain reaction RT-PCR (rt-qPCR). The S. prenanti NPY was detectable from blastulation to hatch, suggesting that npy might be involved in the late embryonic development of S. prenanti. An experiment was conducted to determine the expression profile of npy during feeding of a single meal and during long-term fasting. The expression level of npy in fed fish was significantly decreased at 0.5, 1.5, 3 and 9 h post-feeding (hpf) than in fasting fish. Fasting for 14 days induced an increase in npy messenger (m)RNA expression in the brain. Overall, the results suggest that NPY is a conserved peptide that might be involved in the regulation of feeding and other physiological function in S. prenanti.

Effect of small versus large clusters of fish school on the yield of a purse-seine small pelagic fishery including a marine protected area.

We consider a fishery model with two sites: (1) a marine protected area (MPA) where fishing is prohibited and (2) an area where the fish population is harvested. We assume that fish can migrate from MPA to fishing area at a very fast time scale and fish spatial organisation can change from small to large clusters of school at a fast time scale. The growth of the fish population and the catch are assumed to occur at a slow time scale. The complete model is a system of five ordinary differential equations with three time scales. We take advantage of the time scales using aggregation of variables methods to derive a reduced model governing the total fish density and fishing effort at the slow time scale. We analyze this aggregated model and show that under some conditions, there exists an equilibrium corresponding to a sustainable fishery. Our results suggest that in small pelagic fisheries the yield is maximum for a fish population distributed among both small and large clusters of school.

Alternative intrapopulation life‐history strategies and their trade‐offs in an African annual fish

In ephemeral habitats, the same genotypes cope with unpredictable environmental conditions, favouring the evolution of developmental plasticity and alternative life-history strategies (ALHS). We tested the existence of intrapopulation ALHS in an annual killifish, Nothobranchius furzeri, inhabiting temporary pools. The pools are either primary (persisting throughout the whole rainy season) or secondary (refilled after desiccation of the initial pool), representing alternative niches. The unpredictable conditions led to the evolution of reproductive bet-hedging with asynchronous embryonic development. We used a common garden experiment to test whether the duration of embryonic period is associated with post-embryonic life-history traits. Fish with rapid embryonic development (secondary pool strategy, high risk of desiccation) produced phenotypes with more rapid life-history traits than fish with slow embryonic development (primary pool strategy). The fast fish were smaller at hatching but had larger yolk sac reserves. Their post-hatching growth was more rapid, and they matured earlier. Further, fast fish grew to a smaller body size and died earlier than slow fish. No differences in fecundity, propensity to mate or physiological ageing were found, demonstrating a combination of plastic responses and constraints. Such developmentally related within-population plasticity in life history is exceptional among vertebrates.

The effects of geomagnetic storms on proteinase and glycosidase activities in fish intestinal mucosa

It has been demonstrated that the glycosidase activity of cyprinoid fishes (carp and crucian carp) exposed to a geomagnetic storm for up to 20 h considerably decreases; however, the proteinase activity is weakly altered (a statistically significant decrease in the enzyme activity has been observed only in fasting fish). An in vitro study of the effects of individual half hour intervals of the geomagnetic storm that correspond to the main and recovery phases on the same enzyme activities demonstrates the opposite trend. Independently of the experimental conditions, geomagnetic storms have been shown to influence the enzyme system of fasting fish negatively.

MyProbesTM powered by cytocell-development of Fast FISH 22q11.2 gene deletion testing for paediatric cardiac patients

Homozygous Familial Hypercholesterolaemia (FH) occurs in approximately one in a million births. If untreated, it can lead to the development of severe premature coronary artery disease in childhood. Homozygous FH is caused by mutations in both copies of the LDL cholesterol receptor gene (called LDLR). Individuals with homozygous FH have minimally functional LDL receptors and high doses of statins, often in combinationwith othermedications, are onlymoderately effective in improving lipid levels. In our unit, options beyond conventional lipid lowering medication for this group of patients include plasmapheresis to remove the cholesterol, liver transplant to replace non-functioning LDL receptors with functional LDL receptors from the transplanted liver and access to clinical trial of PCSK9 antibody to increase retention and prevent degradation of LDL receptors. We describe two families with diagnoses of Homozygous FH and their adjustment to the diagnosis and treatment choices. Family A are of Lebanese ancestry and their two year-old son was recently diagnosed with homozygous FH. His parents have had to cope with the shock of a lethal early onset disease in their son and make management decisions within a very short timeframe. Family B are a consanguineous Lebanese family with four children, three of whom have Homozygous FH. One sibling had a liver transplant but died shortly after from myocardial infarct and the two surviving affected siblings currently receive biweekly plasmapheresis. The elder sibling has suffered a great psychological burden from her treatment and has asked our clinic to investigate alternative treatments such as the PCSK9 trial.

Short-term fasting and welfare prior to slaughter in rainbow trout, Oncorhynchus mykiss

Fasting fish before slaughter is a common practice in aquaculture but it is not clear how long rainbow trout can be starved before suffering unnecessary stress, nor at what moment of the day slaughter is least stressful. We fasted 90 rainbow trout (Oncorhynchus mykiss; initial average weight 215.0±22.6g) for 24, 48 and 72h (19.5, 38.8 and 58.0°Cdays) and slaughtered them in the morning (08h00), afternoon (14h00) and night (20h00) to observe the effect of fasting duration and slaughter time on welfare indicators, including plasma cortisol, glucose and lactate concentrations as well as hematocrit and leucocyte count. The values of the fasted fish were compared with 90 control fish kept under similar conditions but not fasted. Body weight was not significantly different between fasted fish and controls during the trial but the relative weight of the gut was higher in control trout. Cortisol levels were similar between fasted and control fish and among the treatment groups. Similar results were found for glucose and lactate concentrations in plasma. Hematocrit values were also normal and similar between fasted fish and controls throughout the experiment, but leucocyte count was slightly lower in fasted fish by day three. There were no clear differences in any of the stress parameters in the morning, afternoon and night in either treatment. These results suggest that rainbow trout can cope with fasting up to three days (58.0°Cdays) prior to slaughter and that their welfare is therefore not seriously compromised.

Feeding and swimming modulate iono-and-hormonal regulation differently in goldfish, Carassius auratus and common carp, Cyprinus carpio

Feeding and swimming can influence ion balance in fish. Therefore we investigated their impact on ionoregulation and its hormonal control in goldfish and common carp. As expected due to the osmorespiratory compromise, exhaustive swimming induced increases in gill Na+/K+ ATPase (NKA) activity in both species, resulting in stable levels of plasma ions. In contrast to our expectations, this only occurred in fed fish and feeding itself increased NKA activity, especially in carp. Fasting fish were able to maintain ion balance without increasing NKA activity, we propose that the increase in NKA activity is related to ammonia excretion rather than ion uptake per se. In goldfish, this increase in NKA activity coincided with a cortisol elevation whilst no significant change was found in carp. In goldfish, high conversion of plasma T4 to T3 was found in both fed and fasted fish resulting in low T4/T3 ratios, which increased slightly due to exhaustive swimming. In starved carp the conversion seemed much less efficient, and high T4/T3 ratios were observed. We propose that thyroid hormone regulation in carp was more related to its role in energy metabolism rather than ionoregulation. The present research showed that both species, whether fed or fasted, are able to sufficiently adapt their osmorepiratory strategy to minimise ions losses whilst maintaining gas exchange under exhaustive swimming.

Interactions between hypoxia tolerance and food deprivation in Amazonian oscars, Astronotus ocellatus (Agassiz)

Oscars are often subjected to a combination of low levels of oxygen and fasting during nest-guarding on Amazonian floodplains. We questioned whether this anorexia would aggravate the osmo-respiratory compromise. We compared fed and fasted oscars (10-14 days) in both normoxia and hypoxia (10-20 Torr, 4 h). Routine oxygen consumption rates (O2) were increased by 75% in fasted fish, reflecting behavioural differences, whereas fasting improved hypoxia resistance and critical oxygen tensions (Pcrit) lowered from 54 Torr in fed fish to 34 Torr when fasting. In fed fish, hypoxia reduced liver lipid stores by approximately 50% and total liver energy content by 30%. Fasted fish had a 50% lower hepatosomatic index, resulting in lower total liver protein, glycogen and lipid energy stores under normoxia. Compared with hypoxic fed fish, hypoxic fasted fish only showed reduced liver protein levels and even gained glycogen (+50%) on a per gram basis. This confirms the hypothesis that hypoxia-tolerant fish protect their glycogen stores as much as possible as a safeguard for more prolonged hypoxic events. In general, fasted fish showed lower hydroxyacylCoA dehydrogenase activities compared with fed fish, although this effect was only significant in hypoxic fasted fish. Energy stores and activities of enzymes related to energy metabolism in muscle or gills were not affected. Branchial Na(+) uptake rates were more than two times lower in fed fish, whereas Na(+) efflux was similar. Fed and fasted fish quickly reduced Na(+) uptake and efflux during hypoxia, with fasting fish responding more rapidly. Ammonia excretion and K(+) efflux were reduced under hypoxia, indicating decreased transcellular permeability. Fasted fish had more mitochondria-rich cells (MRC), with larger crypts, indicating the increased importance of the branchial uptake route when feeding is limited. Gill MRC density and surface area were greatly reduced under hypoxia, possibly to reduce ion uptake and efflux rates. Density of mucous cells of normoxic fasted fish was approximately fourfold of that in fed fish. Overall, a 10-14 day fasting period had no negative effects on hypoxia tolerance in oscars, as fasted fish were able to respond more quickly to lower oxygen levels, and reduced branchial permeability effectively.

The effects of caudal fin amputation on metabolic interaction between digestion and locomotion in juveniles of three cyprinid fish species with different metabolic modes

Metabolic competitive modes between digestion and locomotion are classified into three categories, termed the additive, digestion- and locomotion-priority modes. In nature, the caudal fin is frequently observed to sustain damage as a result of social rank, predation or disease. To test whether the metabolic mode changed differently for fish with different metabolic mode after caudal fin amputation as a consequence of intensified energy competition, we investigated the swimming performance of fasting and fed fish with and without the caudal fin in juveniles of three cyprinid fish species: qingbo (Spinibarbus sinensis, locomotion-priority mode), common carp (Cyprinus carpio, additive mode) and goldfish (Carassius auratus, digestion-priority mode). The critical swimming speed (Ucrit) of fasting qingbo, common carp and goldfish decreased significantly by 49%, 32% and 35% after caudal fin amputation. The maximum tail beat amplitude (TBAmax) (all three fishes), maximum tail beat frequency (TBFmax) (only common carp and goldfish) and (or) active metabolic rate (M˙O2active) (only common carp) increased significantly after caudal fin amputation. In the control fish, digestion let to a significantly lower Ucrit in goldfish but not in qingbo and common carp, and the M˙O2active of digesting common carp was higher than that of fasting fish, suggesting locomotion-priority, additive and digestion-priority metabolic modes in qingbo, common carp and goldfish, respectively. However, after fin amputation, digestion showed no effect on Ucrit in any of the three fishes, and only the digesting common carp showed a higher M˙O2active than their fasting counterparts. This result suggested that the metabolic mode of the goldfish changed from the digestion- to the locomotion-priority mode, whereas the metabolic mode of the other two fishes remained the same after fin amputation. The metabolic mode of the common carp showed no change after fin amputation likely due to the high flexibility of the cardio-respiratory capacity of this fish, as indicated by the increased M˙O2active. Although the metabolic mode remained the same, the feeding metabolism in the fin-amputated qingbo was down-regulated at a lower swimming speed than that of the control group due to the intensified competition between digestion and locomotion. The underlying mechanism for the metabolic mode change in the goldfish is not clear and needs further investigation. However, we speculated that in caudal-fin-intact goldfish, the decreased swimming efficiency, rather than irreducible digestive loading, caused a decreased Ucrit in digesting fish (i.e. false digestion-priority mode), and the metabolic mode should not be judged simply by the relative magnitude of the metabolic rates of fasting and digesting fish.

Abstract P1-07-02: New high-quality HER2 IQFISH pharmDx™ assay with a ½ working day procedure and high concordance to HER2 FISH pharmDx™

Abstract Introduction: HER2 assessment for selection of patients that may benefit from HER2 targeting treatment can be performed by either immunohistochemistry (IHC), fluorescence or chromogen in situ hybridization (FISH or CISH). FISH is a robust and reliable technique for direct visualization and quantitative determination of gene amplifications, deletions and translocations in human cancer cells, but FISH protocols are time-consuming and involve toxic reagents. By introducing a new non-toxic ethylene carbonate based hybridization buffer that perform with very short hybridization times, the total FISH assay time on breast cancer tissue sections can be reduced from the traditional 16–20 hours to 3½–4½ hours. Material and methods: The new Dako HER2 IQFISH pharmDx™ was compared with Dako HER2 FISH pharmDx™ in a comparative study on 120 breast cancer specimens, and reproducibility of the HER2 IQFISH pharmDx™ assay was investigated in a study comprising 3 different sites and a total of 6 different observers. Samples for the comparative study was evaluated by Dako HercepTest™ to include all IHC scoring groups (0, 1+, 2+, 3+). Slides were stained according to manufacturer's instructions using microwave oven for heat pretreatment and RTU pepsin for 3–5 minutes at 37 °C. Hybridization was performed for 2 hours when using HER2 IQFISH pharmDx™ and for 17–20 hours when using HER2 FISH pharmDx™ Kit. All slides were blinded before evaluation. HER2 status was classified as “Non-amplified” when the HER2/CEN17 ratio < 2.0 and “Amplified” when the HER2/CEN17 ratio ≥ 2.0. Results: The new non-toxic hybridization buffer introduces a major safety improvement since formamide is no longer needed. Significantly shorter hybridization times are required to generate the same signal intensity (1–2 hour hybridization versus overnight). HER2 IQFISH pharmDx™ was compared with the traditional HER2 FISH pharmDx™ in a comparative study on 120 breast tissue specimens of human breast carcinoma. The preliminary data on HER2 status for 78 patients obtained by the two assays gave an overall agreement of 98.7% with lower and upper 95% confidence limits at 94.2% and 99.9%. The Kappa value was 0.96 (95% CL: 0.89–1.00). The p-value for McNemars test was 1.00 indicating absence of bias between the two assays. Disagreement between the two assays was observed for one specimen - a heterogeneous tissue with a small amplified area. Data from the reproducibility study that included site-to-site variation, day-to-day variation and inter-observer variation showed that the assay has a high degree of reproducibility. Conclusion: The validation studies of the new HER2 IQFISH pharmDx™ showed a very high concordance to the traditional HER2 FISH pharmDx™ and also that the assay is robust and reproducible. Reduction of the overall assay time from a two-day to a half-day procedure for HER2 FISH, offers more flexible laboratory routines and same day reporting for all working days of the week, which could be used for fast and simultaneous FISH and IHC answers and improved patient care. Taken together, the study demonstrates the potential of a new revolutionary platform that enables optimization and acceleration of FISH analysis to the benefit of cancer patients and laboratory personnel. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P1-07-02.

The effects of hypoxia acclimation, exercise training and fasting on swimming performance in juvenile qingbo (Spinibarbus sinensis)

To investigate the effects of hypoxia acclimation, exercise training and fasting on the swimming performance of juvenile qingbo (Spinibarbus sinensis), we measured the critical swimming speed (U (crit)), resting and excess post-exercise oxygen consumption (EPOC) of control, hypoxia-acclimated, exercise-acclimated and fasting fish at 25°C. The muscle and plasma metabolites before and after a bout of exhaustive exercise (produced by chasing) were also measured. The fish were acclimated to hypoxia (48h at 1.0mgL(-1), 12.5% air saturation), exercise training (2weeks at 60% of U (crit), 6h daily) or fasting (2weeks). All treatments resulted in significantly lower resting oxygen consumption ([Formula: see text]O(2rest)) but had no effect on the magnitude of EPOC. Hypoxia acclimation had no effect on U (crit) or peak post-exercise oxygen consumption ([Formula: see text]O(2peak)) but produced a higher depletion of muscle [glycogen] post-chasing (P<0.05). Exercise training produced a significant increase in U (crit), higher liver [glycogen] pre-chasing and higher depletion of muscle [glycogen] post-chasing. Fasting resulted in a significant decrease in U (crit), [Formula: see text]O(2peak), muscle and liver [glycogen]. These results suggested that hypoxia acclimation had no effect on swimming performance in qingbo. Exercise training produced improved swimming performance by increasing the stored energy and the metabolic capacity of muscle. Fasting had a profound effect on swimming performance through both decreased respiratory capacity and a depleted energy store.

Novel FISH and quantitative PCR protocols to monitor artificial consortia composed of different hydrogen-producing Clostridium spp.

The use of an artificial consortium composed of selected hydrogen-producing species, instead of a natural anaerobic sludge, has been proposed for biohydrogen production. In order to monitor such a consortium composed of different Clostridium spp., new protocols were tested for two different assays, FISH and qPCR. New species-specific FISH probes and qPCR primer sets were developed and optimised for three strains: Clostridium butyricum, Clostridium felsineum and Clostridium pasteurianum, that were used in a consortium. Application of a fast two-step FISH protocol, with pre-treatment step at 90 °C for 5 min and a subsequent hybridisation step at higher temperature (55 °C) for 20 min resulted in a much shorter analytical time compared to the standard FISH procedure (46 °C for 2–3 h) and gave a high hybridisation performance. Moreover, to accurately quantify each microorganism by qPCR assay, two innovations were tested: the direct use of cell lysates (omitting the DNA extraction step) and the use of two alternative molecular markers, recA and gyrA. These markers are present in single copies in the genome, whereas there are multiple copies of the ribosomal operons. This resulted in the development of accurate, reliable and fast FISH and qPCR assays for routine monitoring of the dynamics of artificial hydrogen-producing microbial consortia. Moreover, both techniques can be easily adapted to new Clostridium strains.

The effects of temperature on metabolic interaction between digestion and locomotion in juveniles of three cyprinid fish ( Carassius auratus, Cyprinus carpio and Spinibarbus sinensis)

To test whether the effects of temperature on the metabolic mode changed among different fish species, we investigated the specific dynamic action (SDA) and swimming performance of fasting and fed fish at 15 and 25 °C in three juvenile Cyprinidae fish species: goldfish ( Carassius auratus), common carp ( Cyprinus carpio) and qingbo ( Spinibarbus sinensis). Both taxon and temperature had significant effects on the resting oxygen consumption rate ( M ˙ O rest), SDA and swimming performance ( p < 0.05). In addition, the effect of temperature differed significantly among the different species (interaction effect, p < 0.05). Under the low temperature condition, digestion had no effect on either critical swimming speed ( U crit) or the active M ˙ O 2 ( M ˙ O active) for all fish species (additive metabolic mode). When the temperature was increased from 15 to 25 °C, the metabolic scope ( MS) for digestion increased approximately 182, 49 and 17%, and the MS for locomotion increased approximately 129, 58 and 138% in goldfish, common carp and qingbo, respectively. The total metabolic demands for both digestion and locomotion (i.e., the sum of digestive MS and locomotive MS) increased approximately 143, 56 and 112% in goldfish, common carp and qingbo, respectively. The total MS for both digestion and locomotion (the difference between M ˙ O active in fed fish and M ˙ O rest in fasting fish) increased approximately 106, 58 and 78% in goldfish, common carp and qingbo, respectively. Thus, the MS for locomotion in fed goldfish decreased due to the large increase in digestive function at the high temperature, and the U crit of fed goldfish decreased by 11% compared to that of fasting fish ( p < 0.05) (digestion-priory metabolic mode). The metabolic mode of qingbo changed to locomotion-priority mode, as illustrated by the large increase in locomotive MS in response to the increase in temperature. In the common carp, temperature had no effect on metabolic mode as illustrated by the parallel increases in cardio-respiratory capacity and metabolic capacity of digestive and locomotive organs. A discussion on the changes in metabolic mode in response to temperature and its possible relationship with the metabolic characteristics of a given fish species was also documented in this paper.

The effects of fasting on the metabolic interaction between digestion and locomotion in juvenile southern catfish (Silurus meridionalis)

To investigate the effect of fasting on maintenance metabolism, feeding metabolism and aerobic swimming performance as well as their metabolic interactions in juvenile southern catfish, we measured the following: (1) the postprandial oxygen consumption (M˙O2) response (16% body mass meal size) after 0 (control), 1, 2 and 4weeks of fasting and (2) the swimming performance of non-digesting and digesting fish after either 0, 1, 2 or 4weeks of fasting. The fasting groups displayed with lower resting M˙O2 (M˙O2rest), lower peak postprandial M˙O2 (M˙O2peak), larger energy expenditures and longer digestive processes than those of the control groups. The critical swimming speed (Ucrit), the active M˙O2 (M˙O2active) and the metabolic scope (M˙O2active -M˙O2rest, MS) of both non-digesting and digesting fish all decreased progressively after 1, 2 and 4weeks of fasting, with those of non-digesting fish decreased more acutely than digesting fish (P<0.05). Digesting fish displayed with a 14%, 23%, 27% and 71% significantly higher M˙O2active than that of non-digesting fish in the 0-, 1-, 2- and 4-week fasting groups. Digestion only caused a significantly lower Ucrit and MS in both the 0- and 1-week fasting groups (P<0.05). The M˙O2 increased greatly with the swimming speed, and digestion caused a higher M˙O2 when compared to that of the fasting fish in any groups. The M˙O2 of fish in the 4-week fasting group was significantly lower than that of other groups when the swimming speed was the same. In conclusion, both digestive and locomotive functions were down-regulated during fasting. In the 0- and 1-week fasting groups, the decreased MS for swimming during digestion caused a lower Ucrit (i.e., a digestion priority model). However, because the M˙O2active of digesting fish decreased much more slowly than that of fasting fish, the MS of the 2- and 4-week fasting groups did not change during digestion, and the fish could handle both physiological activities independently (i.e., an additive model).

The effects of dissolved oxygen level on the metabolic interaction between digestion and locomotion in juvenile southern catfish ( Silurus meridionalis Chen)

To investigate the effect of dissolved oxygen level ([O 2]) on maintenance metabolism, feeding metabolism, aerobic swimming performance and their metabolic interaction in juvenile southern catfish ( Silurus meridionalis Chen), we measured the following: (1) the resting oxygen consumption rate ( MO 2rest) over a range of water [O 2] and from this we calculated the critical oxygen tension ( P crit) of fasting fish; (2) the postprandial MO 2 response (10% body mass meal size) at water [O 2] of 1, 2, 4 and 8 mgO 2 L − 1 ; and (3) the swimming performance of fasting and digesting fish at water [O 2] of 1, 2, 4 and 8 mgO 2 L − 1 at 25 °C. The MO 2rest remained constant over a broad range of water [O 2] but then dropped markedly upon reaching the P crit (16.4% saturation). Hypoxic groups presented lower peak postprandial MO 2 ( MO 2peak) (1 mgO 2 L − 1 group), larger energy expenditure and longer digestive process (both 1 and 2 mgO 2 L − 1 ) than those of normoxic groups. Both critical swimming speed ( U crit) and the active metabolic rate ( MO 2active) of fasting fish remained unchanged over a decrease in water [O 2] from 8 to 4 mgO 2 L − 1 and then decreased significantly with further decreases in water [O 2]. These parameters in fed fish showed a pronounced decrease as water [O 2] decreased from 8 to 1 mgO 2 L − 1 . Feeding caused a significantly lower U crit in the 2 mgO 2 L − 1 water [O 2] group, a significantly higher MO 2active in both the 2 and 8 mg L − 1 water [O 2] groups and a significantly higher metabolic scope ( MO 2active − MO 2rest) in both the 2 and 4 mgO 2 L − 1 water [O 2] groups compared to fasting fish. The MO 2 increased greatly with swimming speed in the higher water [O 2] groups, whereas it leveled off as swimming speeds approached the U crit in the lower water [O 2] groups. Within all water [O 2] groups, feeding caused a higher MO 2 compared to fasting fish when fish swam at the same speeds, except in the 1 mgO 2 L − 1 group. This finding showed that the critical water [O 2] for maintenance of metabolism, digestion, swimming and postprandial swimming increased sequentially due to the increasing O 2 demand, which challenges respiratory capacity. With the administration of the medium-sized meal that was used in this study, the metabolic mode of juvenile southern catfish changed from an additive mode during normoxia to a digestion-priority mode under moderate hypoxia and to locomotion-priority mode under hypoxia.

An in vivo and in vitro assessment of autophagy-related gene expression in muscle of rainbow trout (Oncorhynchus mykiss)

In mammals, new evidence has demonstrated the important role of the autophagic/lysosomal pathway in regulating muscle mass and identified the transcription factor FoxO3 as a key factor of the control of this proteolytic system by inducing several autophagy-related genes. In contrast, the mechanisms responsible for the regulation of autophagy have not been investigated in teleosts, known to exhibit different muscle growth dynamics. The present work aimed to characterize both in vivo and in vitro the transcriptional regulation of several major genes involved in autophagy (LC3B, gabarapl1, atg12l, atg4b) in the white skeletal muscle of rainbow trout. We found that fasting fish for 14days or serum depletion of trout myocytes strongly induces the expression of all studied genes. Our in vitro study on trout myocytes indicated that IGF1 induces FoxO3 phosphorylation but has a low or no effect on autophagy-related gene expression, suggesting a moderate role for this transcription factor on the autophagic/lysosomal pathway in this species. Data reported here show for the first time in a lower vertebrate, the existence and the regulation of several major genes involved in the autophagy, opening a new area of research on the molecular bases of muscle protein degradation in teleosts.

Autonomic regulation of the heart during digestion and aerobic swimming in the European sea bass (Dicentrarchus labrax)

The autonomic regulation of the heart was studied in European sea bass (Dicentrarchus labrax) during digestion and aerobic exercise by measuring cardiac output (Q), heart rate (fH), stroke volume (Vs) and oxygen consumption (MO2) before and after pharmacological blockade by intraperitoneal injections of atropine and propranolol. The significant rise in MO2 (134±14 to 174±14mgkg−1h−1) 6h after feeding (3% body mass) caused a significant tachycardia (47.7±10.9 to 72.6±7.2beatsmin−1), but only a small elevation of Q. MO2 of fasting fish increased progressively with swimming speed (0.7–2.1BLs−1) causing a significant tachycardia (43±6 to 61±4mLmin−1kg−1) and increased Q but Vs did not change. Inactive fish were characterized by a high vagal tone (98.3±21.7%), and the tachycardia during digestion and exercise was exclusively due to a reduction of vagal tone, while the adrenergic tone remained low during all conditions. Intrinsic fH, revealed after double autonomic blockade, was not affected by digestion (71±4 and 70±6min−1, respectively), indicating that non-adrenergic, non-cholinergic (NANC) factors do not contribute to the tachycardia during digestion in sea bass.

The effects of experimental energy depletion on the physiological condition and survival of adult sockeye salmon (Oncorhynchus nerka) during spawning migration

In 2005 and 2006, adult sockeye salmon (Oncorhynchus nerka) were captured en route to spawning grounds and placed in either a slow (∼ 0.1 m·s−1) or fast (∼0.4 m·s−1) water velocity treatment for 18 days in order to assess how migrational energy depletion during the final stages of maturation affected physiological condition and survival. Fish in the fast treatment utilized more energy than the slow treatment in 2005 (0.91 MJ kg−1 vs. 0.43 MJ kg−1; P = 0.010), and 2006 (0.72 MJ kg−1 vs. 0.37 MJ kg−1; P = 0.021). Non-treatment fish captured upon arrival at spawning grounds showed energy levels intermediate to the two treatments in 2005 and lower than both in 2006, suggesting that energy use during the treatments were within levels normally experienced by this population. No differences in survival were found between treatments (P > 0.05), although females had lower survival than males in both years (both P < 0.01). After 18 days, surviving fish from the fast treatment showed signs of elevated physiological stress relative to fish from the slow treatment. Specifically, plasma osmolality was lower in fast fish in 2005 (P < 0.001), as was plasma chloride in both years (both P < 0.02). In 2006, plasma lactate was higher (P = 0.014) in fast fish. Within the ranges of energetic depletion that were examined here, a more energy-intensive migration can have a substantial influence on the physiological condition and stress of adult sockeye salmon, but not on survival.

The effect of exercise training on the metabolic interaction between digestion and locomotion in juvenile darkbarbel catfish ( Peltebagrus vachelli)

To examine the effects of exercise training on the metabolic interaction between digestion and locomotion in juvenile darkbarbel catfish ( Peltebagrus vachelli) (5.58 ± 0.04 g), the postprandial metabolic response, critical swimming speeds ( U crit) and oxygen consumption rates ( VO 2) during swimming were measured on fish held at a constant temperature (25 °C). Fish were fed a diet of cutlets of freshly killed loach. Fish in the trained group were forced to swim at 60% U crit for 50 min followed by an exhaustive 10-min chase once daily for 21 days. Exercise training did not produce significant differences in resting VO 2 ( VO 2rest) and postprandial peak VO 2 ( VO 2peak) compared to the non-trained groups. However, exercise training elicited a significant decrease in both the duration and energy expenditure of digestion when fed with similar food ( P < 0.05). Feeding had no significant effect on U crit of non-trained fish, while it caused a significantly lower U crit (compared to fasting fish) in trained fish ( P < 0.05). Training resulted in a significantly higher U crit and active VO 2 ( VO 2active) in fasting fish when fish swam at U crit. However, training had no effect on either the U crit or VO 2active of post-feeding fish. Our results suggest that: (1) the central cardio-respiratory systems of non-trained darkbarbel catfish can support the oxygen demands of both digestion and the locomotion simultaneously; (2) the metabolic mode of competition in darkbarbel catfish is flexible; it changed from an additive model to a digestion-priority model after exercise training; (3) training may be accounted for cardio-respiratory capacity increase and following improvement of swimming performance during fasting in darkbarbel catfish, although, the swimming capacity was sacrificed to digestion in the situation of postprandial locomotion.

The metabolic responses and acid–base status after feeding, exhaustive exercise, and both feeding and exhaustive exercise in Chinese catfish (Silurus asotus Linnaeus)

Feeding and exhaustive exercise are known to elevate metabolism. However, acid-base status may be oppositely affected by the two processes. In this study, we first investigated the acid-base response of Chinese catfish to feeding (the meal size was about 8% of body mass) to test whether an alkaline tide (a metabolic alkalosis created by gastric HCl secretion after feeding) would occur. We then determined the combined effects of feeding and exhaustive exercise on excess post-exercise oxygen consumption and acid-base status to determine whether the alkaline tide induced by feeding protects against acid-base disturbance during exhaustive exercise and affects subsequent recovery. Arterial blood pH increased from 7.74 +/- 0.02 before feeding to 7.88 +/- 0.02 and plasma [HCO(3)(-)](pl) increased from 5.42 +/- 0.29 to 7.83 +/- 0.37 mmol L(-1) 6 h after feeding, while feeding had no significant effect on PCO2. Exhaustive exercise led to a significant reduction in pH by 0.46 units and a reduction of [HCO(3)(-)](pl) by approximately 3 mmol L(-1). Lactate concentrations in white muscle and plasma increased by 2.4 mmol L(-1) and 13.4 micromol g(-1), respectively. Fed fish had a higher pH and [HCO(3)(-)](pl) than fasting fish at rest, and the reductions in pH (0.36 units) and [HCO(3)(-)](pl) (approximately 2 mmol L(-1)) were thus lower after exhaustive exercise. However, the recovery of acid-base status and metabolites were similar in digesting and fasting fish. Overall, a significant alkaline tide was found in Chinese catfish after feeding. The alkaline tide elicited by feeding significantly prevented the decreases in pH and [HCO(3)(-)](pl) immediately after exhaustive exercise, but recovery from exhaustive exercise was not affected by digestion.