Low social status impairs hypoxia tolerance in rainbow trout (Oncorhynchus mykiss)

In the present study, chronic behavioural stress resulting from low social status affected the physiological responses of rainbow trout (Oncorhynchus mykiss) to a subsequent acute stressor, exposure to hypoxia. Rainbow trout were confined in fork-length matched pairs for 48-72?h, and social rank was assigned based on behaviour. Dominant and subordinate fish were then exposed individually to graded hypoxia (final water PO(2), PwO(2)?=?40?Torr). Catecholamine mobilization profiles differed between dominant and subordinate fish. Whereas dominant fish exhibited generally low circulating catecholamine levels until a distinct threshold for release was reached (PwO(2)?=?51.5?Torr corresponding to arterial PO(2), PaO(2)?=?24.1?Torr), plasma catecholamine concentrations in subordinate fish were more variable and identification of a distinct threshold for release was problematic. Among fish that mobilized catecholamines (i.e. circulating catecholamines rose above the 95% confidence interval around the baseline value), however, the circulating levels achieved in subordinate fish were significantly higher (459.9?±?142.2?nmol?L(-1), mean?±?SEM, N?=?12) than those in dominant fish (130.9?±?37.9?nmol?L(-1), N?=?12). The differences in catecholamine mobilization occurred despite similar P(50) values in dominant (22.0?±?1.5?Torr, N?=?6) and subordinate (22.1?±?2.2?Torr, N?=?8) fish, and higher PaO(2) values in subordinate fish under severely hypoxic conditions (i.e. PwO(2)?相似文献   

Antibacterial proteins in rainbow trout, Oncorhynchus mykiss

Antibacterial proteins are an important part of the innate immune system for all animals. They have been extensively studied in mammals, amphibians and invertebrates, but have received only scant attention in fish. Their expression and processing, however, provide a way of monitoring defence vigour during development or with seasonal changes in physiology. The aim of the present work was to identify and characterise antibacterial proteins in rainbow trout. In vitro analyses of extracts of the peripheral blood leucocytes, head kidney leucocytes and mucus from adult unstimulated (non-immune) fish showed marked antibacterial activity against Gram positive bacteria. Fractionation by ion exchange chromatography and RP-HPLC of head kidney extracts showed the presence of two forms of lysozyme but no constitutively expressed antimicrobial proteins of < 10 kDa. By contrast, chromatographic analyses of mucus revealed at least four antibacterial proteins. Two are conventional lysozymes, a third is an unusual lysozyme-like protein with a low isoelectric point, and the fourth is a highly hydrophobic, cationic peptide of c. 3 kDa.     

Behavioural fever boosts the inflammatory response in rainbow trout Oncorhynchus mykiss

Behavioural fever, manifested as an increased preferred temperature, was shown in rainbow trout Oncorhynchus mykiss following an injection of bacterial lipopolysaccharide. Simulated behavioural fever, through a 2·5° C water temperature rise following bacterial lipopolysaccharide injection, enhanced the expression of the cytokine interleukin-1β, in comparison with an untreated group held at the initial temperature. The present findings show that an important mediator in the immune response can be boosted through behavioural fever in fishes.     

Exhaustive exercise and the cellular stress response in rainbow trout, Oncorhynchus mykiss

The goal of this study was to examine the cellular response to exhaustive exercise in male and female rainbow trout to determine if HSPs are involved in the early stages of the recovery process. Levels of HSPs and key metabolic parameters were measured in white muscle, heart plasma, and blood plasma throughout 6 h of recovery from exhaustive burst exercise. Plasma creatine kinase (CK) was also quantified as an indicator of exercise-induced tissue damage. The observed trends in ATP and lactate were consistent with established patterns of exhaustion and the beginnings of metabolic recovery. However, no upregulation of hsp70, hsp30, or hsp90 was evident in heart or muscle tissue of males or females, and plasma CK measurements suggest that tissue damage was minimal. Our results indicate that hsp70, hsp30, and hsp90 are not part of the early recovery process from burst exercise in fish, perhaps due to the maintenance of core temperatures as well as a lack of exercise-induced tissue damage.     

虹鳟对时间和地点的学习记忆(英文)

为确定虹鳟(Oncorhynchus mykiss)是否能将日投放两次食物的不同时间和地点联系起来,在30天内,于09:00-10:00将食饵投放在水族箱一侧,于15:00-16:00将食饵投放在水族箱另一侧.在第21天和28天,不放食饵以确定虹鳟对时间-地点的学习记忆.结果表明,虹鳟将不同时间和地点联系起来以获取食物,并且在水族箱两个投放食饵之处均表现出预取食活动,提示该物种具有控制时间-地点学习任务的内在机制.     

The effect of strenuous exercise and beta-adrenergic blockade on the visual performance of juvenile rainbow trout,Oncorhynchus mykiss

It is hypothesised that the visual performance of rainbow trout, Oncorhynchus mykiss, will be impaired by strenuous exercise as a result of metabolic stress (blood lactacidosis) that activates the Root effect and limits the oxygen-carrying capacity of blood flowing to the eye. The ability to resolve high contrast objects on a moving background, as a measure of visual performance, was quantified pre- and post-exercise using the optomotor response. Strenuous exercise induced a metabolic acidosis (8.0 mmol l(-1) blood lactate) and a significant red cell swelling response but no change in the optomotor response threshold (120 min of arc) was observed. Beta-adrenergic blockade (propranolol) abolished post-exercise red cell swelling but optomotor response thresholds were still maintained at 120 min of arc despite a significant blood lactate load (7.8 mmol l(-1)). The choroid rete mirabile of the trout is extremely well developed (rete area:eye area = 0.39) and may maintain visual performance by ensuring a relatively direct supply of oxygen to the central regions of the avascular retina. Exercised fish under beta-adrenergic blockade exhibited an enhanced optomotor response at 240-300 min of arc. Assuming that these responses reflect "tunnel vision", adrenergic regulation of red cell function may preserve a high ocular PO(2) gradient that satisfies the oxygen demand of peripheral retinal cells.     

Acid-base balance during social interactions in rainbow trout (Oncorhynchus mykiss)

Socially subordinate rainbow trout (Oncorhynchus mykiss) experience chronic stress that impacts upon a variety of physiological functions, including Na(+) regulation. Owing to the tight coupling between Na(+) and Cl(-) uptake and, respectively, H(+) and HCO(3)(-) loss at the gill, ionoregulatory changes associated with social status may affect acid-base regulation. The present study assessed the responses of dominant, subordinate and control trout to hypercapnia (1% CO(2)) to test this hypothesis. Social status appeared to impact net acid excretion (J(net)H(+)) as subordinate individuals failed to increase net acid flux in response to hypercapnia. However, blood acid-base status was found to be unaffected by social status before or during hypercapnic exposure, indicating that subordinate fish were as effective as dominant or control trout in achieving compensation for the acid-base disturbance induced by hypercapnic exposure. Compensation in all groups involved decreasing Cl(-) uptake in response to hypercapnia. The branchial activities of both Na(+),K(+)-ATPase (NKA) and V-type H(+)-ATPase were affected by social interactions and/or exposure to hypercapnia. Branchial NKA activity was higher but V-ATPase activity was lower in control fish than in dominant or subordinate trout. In addition, control and subordinate but not dominant trout exposed to 24h of hypercapnia exhibited significantly higher branchial V-ATPase activity than fish maintained in normocapnia. Collectively, the data suggest that subordinate trout are able to regulate blood pH during a respiratory acidosis.     

Domestication shapes morphology in rainbow trout Oncorhynchus mykiss

In this study, clonal lines from North American resident and migratory populations of rainbow trout Oncorhynchus mykiss adapted to different geographical conditions and with different domestication histories were characterized morphologically. Lines reared in a common‐garden experiment were characterized for external shape and meristic values, searching for a general pattern of morphological variation due to exposure to captive conditions. A sharp distinction was identified between wild and captive lines. The body profile was deeper in captive lines, with longer dorsal and anal fins and shorter and deeper caudal peduncles. Highly significant differences were also identified in meristic values among the lines but no consistent relation between meristic values and domestication status was detected. This morphological characterization will facilitate the selection of lines with divergent phenotypes for subsequent quantitative trait loci analysis, aimed at identifying genome regions linked with morphological adaptive response to captive conditions.     

A blue variant in the rainbow trout, Oncorhynchus mykiss Walbaum

A blue variant of the rainbow trout, which appeared in a French fish farm, displayed an iridescent body color that was cobalt blue on the back, lighter on the undersides, and silvery on the belly and which held up to adult stage. This color was supposed to result from a Tyndall effect involving a structural arrangement of melanin pigments because it disappeared when it was associated with a depigmenting gene. This blue variant appeared to be governed by an autosomal recessive gene. Blue fry survival and body weight were about 25% less than those of wild-type sibs, but no major problem was observed in further breeding performances, including reproduction. These features do not correspond with those of the blue variants previously described in the rainbow trout.     

Ubiquitin genes in rainbow trout (Oncorhynchus mykiss)

Ubiquitin is a small protein involved in intracellular proteolysis. It is highly conserved throughout eukaryotic phyla and has been detected in such diverse species as yeast, barley, Drosophila and man. A previous study showed that chromatin of rainbow trout testis contains free ubiquitin with a sequence similar to that of other phyla. In the present study, which focused on rainbow trout but included eleven other species, it is shown that fish ubiquitin genetic organisation and expression are similar to those of other phylogenetic groups through the following set of observations: (a) Multiple loci were detected, (b) These loci encode repeats of ubiquitin, (c) Although the DNA sequences are not conserved, the encoded amino acid sequences are fully conserved, (d) The expression of ubiquitin was influenced by cell culture conditions and viral infection.     

The ontogeny of drinking in the rainbow trout, Oncorhynchus mykiss (Walbaum)

Drinking was measured by the rate of uptake of tritiated dextran in fresh water by the alevins and fry of rainbow trout at various stages of development during a 40-day post-hatch period. Drinking increased almost S-fold during the initial 16 day yolk-sac stage. Drinking rate increased most between 16 and 23 days, the transitional period between yolk-sac absorption and first feeding. The maximum weight-specific drinkingrateof 3.24μlg⁻¹ h⁻¹ recorded for 40-day-old fry was higher than previously recorded for adults. Abrupt transfer from an adaptation temperature of 10 to 19° C increased drinking significantly (Q₁₀= 1.2), but sudden transfer to 1 1‰ salinity sea water caused a substantial fall in drinking rate in 23-day fry. A 24-h period of adaptation to 1 1‰ and 15‰ salinity restored drinking to a rate similar to that in fresh water. The water drunk by 31-day fry fed to satiation was initially higher than by unfed fry, but drinking rates subsequently fell below the control level. The results are discussed in terms of osmoregulation and the uptake of dissolved or suspended substances by the intestinal tract for the purpose of immunization.     

Coronary vascular volume remodelling in rainbow trout Oncorhynchus mykiss

The 34% increase in relative ventricular mass (M_rv) resulting from chronic anaemia (induced by an intraperitoneal injection of phenylhydrazine hydrochloride) was accompanied by a 117% increase in coronary vascular volume of diploid rainbow trout Oncorhynchus mykiss. Coronary vascular volume of normocythemic triploid fish was similar to that of normocythemic diploid fish despite a larger M_rv. These observations, in combination with previous studies, suggest that the vascularity of compact myocardium in O. mykiss can vary independently of M_rv.     

The influence of social interaction on the acclimation of rainbow trout, Oncorhynchus mykiss (Walbaum) to chronic stress

To establish the time required for fish to acclimate to experimental conditions, comprising holding within a spatially restrictive environment, rainbow trout were transferred from rearing tanks (1500 1) to smaller volume holding tanks (50 1). The fish were maintained singly, in pairs, in groups of five fish, and in groups of 10 fish, and selected indices of physiological stress were monitored at intervals following the onset of confinement. In all cases transfer and confinement provoked a stress response in the fish, indicated by significantly elevated plasma cortisol levels, and significantly reduced numbers of circulating lymphocytes. Recovery of these parameters to levels similar to unstressed control fish, was most rapid among the fish confined singly, requiring 2 to 4 weeks, although weight gain, indicative of feeding, was apparent within 1 to 2 weeks. Acclimation of the fish confined as pairs was severely confounded by the development of hierarchical relationships between the fish. This resulted in some individuals displaying rapid acclimation and growth, in contrast to other fish within the groups which failed to acclimate, exhibited signs of chronic stress, and ultimately succumbed to bacterial infections. Similar, though less severe, evidence of social stress was observed among the fish confined as groups of five. A decline in the coefficient of variance for weight within the fish confined as groups of 10 suggested an absence of growth inhibition due to social interaction among these fish. The implications of these results for experimental design are discussed.     

Formation of chromosome aberrations in androgenetic rainbow trout Oncorhynchus mykiss

Residues of maternal nuclear DNA in the form of chromosome fragments were observed in the healthy and morphologically normal androgenetic rainbow trout Oncorhynchus mykiss. A hypothetical model for formation of chromosome re‐arrangements caused by the incomplete maternal nuclear DNA inactivation in the androgenetic rainbow trout was proposed in the present paper.     

Distribution of canthaxanthin in immature rainbow trout Oncorhynchus mykiss serum

• 1.1. The present study was undertaken in order to define the distribution of canthaxanthin between the lipoprotein fractions in serum of immature rainbow trout fed a diet supplemented with synthetic canthaxanthin (80 mg/kg).
• 2.2. Lipoproteins were separated by density-gradient ultracentrifugation.
• 3.3. Canthaxanthin was found in all lipoprotein fractions, in different amounts according to the density of the lipoprotein fraction: VLDL, 13.9%; LDL, 15.2% or LDL, 29.1% since the density of the first fraction was 1.006 g/ml; HDL, 60.4% and VHDL, 10.5%.

     

Brain distribution of myosin Va in rainbow trout Oncorhynchus mykiss

This study presents data on myosin Va localization in the central nervous system of rainbow trout. We demonstrate, via immunoblots and immunocytochemistry, the expression of myosin Va in several neuronal populations of forebrain, midbrain, hindbrain and spinal cord. The neuronal populations that express myosin Va in trout constitute a very diverse group that do not seem to have many specific similarities such as neurotransmitters used, cellular size or length of their processes. The intensity of the immunoreactivity and the number of immunoreactive cells differ from region to region. Although there is a broad distribution of myosin Va, it is not present in all neuronal populations. This result is in agreement with a previous report, which indicated that myosin Va is approximately as abundant as conventional myosin II and kinesin, and it is broadly involved in neuronal motility events such as axoplasmatic transport. Furthermore, this distribution pattern is in accordance with what was shown in rats and mice; it indicates phylogenetic maintenance of the myosin Va main functions.     

Pre-and post-branchial blood respiratory status during acute hypercapnia or hypoxia in rainbow trout,Oncorhynchus mykiss

Simultaneous venous (pre-branchial) and arterial (post-branchial) extracorporeal blood circulations were utilized to monitor continuously the rapid and progressive effects of acute environmental hypercapnia (water partial pressure of CO₂ 4.8±0.2 torr) or hypoxia (water partial pressure of O₂ 25±2 torr) on oxygen and carbon dioxide tensions and pH in the blood of rainbow trout (Oncorhynchus mykiss). During hypercapnia, the CO₂ tension in the arterial blood increased from 1.7±0.1 to 6.2±0.2 torr within 20 min and this was associated with a decrease of arterial extracellular pH from 7.95±0.03 to 7.38±0.03; the acid-base status of the mixed venous blood changed in a similar fashion. The decrease in blood pH in vivo was greater than in blood equilibrated in vitro with a similar CO₂ tension indicating a significant metabolic component to the acidosis in vivo. Under normocapnic conditions, venous blood CO₂ tension was slightly higher than arterial blood CO₂ tension difference was abolished or reversed during the initial 25 min of hypercapnia indicating that CO₂ was absorbed from the water during this period. Arterial O₂ tension remained constant during hypercapnia; however, venous blood O₂ tension decreased significantly (from 22.0±2.6 to 9.0±1.0 torr) during the initial 10 min. Hypercapnia elicited the release of catecholamines (adrenaline and noradrenaline) into the blood. The adrenaline concentration increased from 6±3 to 418±141 nmol · l^-1 within 25 min; noradrenaline concentration increased from 3±0.5 to 50±21 nmol · l^-1 within 15 min. During hypoxia arterial blood O₂ tension declined progressively from 108.4±9.9 to 12.8±1.7 torr within 30 min. Venous blood O₂ tension initially was stable but then decreased abruptly as catecholamines were released into the circulation. The release of catecholamines occurred concomitantly with a sudden metabolic acidosis in both blood compartments and a rise in CO₂ tension in the mixed venous blood only.Abbreviations CCO₂ plasmatotal carbondioxide - CtO₂ blood oxygen content - PO₂ partial pressure of oxygen - PCO₂ partial pressure of carbon dioxide - PaO₂ arterial bloodPO₂ - PaCO₂ arterial bloodPCO₂ - PvCO₂ venous bloodPCO₂ - PwO₂ waterPO₂ - PwCO₂ waterPCO₂ - Hb haemoglobin - SHbO₂ haemoglobin oxygen saturation - HPLC high-performance liquid chromatography - rbc red blood cell(s) - Hct haematocrit