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1.
Experiments were conducted to test the hypothesis that branchial gas transfer is enhanced in rainbow trout during hypoxia or hypercarbia by bradycardia and systemic vasoconstriction. Gas transfer was indirectly assessed by continuous monitoring of arterial blood gases, PaO2 and PaCO2. Cardiac frequency was maximally decreased by 34.9+/-4.3 and 8.6+/-3.2 bpm in hypoxic and hypercarbic fish, respectively. Pre-treating fish with atropine (1micromol kg(-1)) attenuated or abolished the bradycardia during hypoxia and hypercarbia, respectively. However, there were no significant differences in the arterial blood gases between the control and atropinized fish. Dorsal aortic blood pressure was increased maximally by 11.3+/-2.8 and 17.7+/-2.0mm Hg in the hypoxic and hypercarbic fish. Pre-treatment of fish with prazosin (2.4micromol kg(-1)) prevented these increases in blood pressure. Blood gases were unaltered by prazosin treatment in the hypercarbic fish. However, in the hypoxic fish, gas transfer appeared to be impaired by prazosin on the basis of lowered PaO2 (by approximately 35 mm Hg compared to control fish) and increased PaCO2 (by approximately 0.3mm Hg). Because the normal hyperventilatory response to hypoxia was prevented by prazosin, it is possible that the impairment of gas transfer was related to inadequate ventilation rather than to any differences in the pressor response. The present results provide no evidence that gas transfer in rainbow trout is enhanced by bradycardia nor do they reveal any obvious benefit associated with the increases in blood pressure that accompany hypoxia and hypercarbia.  相似文献   

2.
Potential immunostimulatory effects of orally administered β-glucan were investigated in combination with immersion vaccination against enteric redmouth disease caused by Yersinia ruckeri in rainbow trout (Oncorhynchus mykiss). A linear, unbranched and pure (purity ≥98%) β-1,3-glucan (syn. paramylon) from the alga Euglena gracilis was applied at an inclusion level of 1% β-glucan in feed administered at a rate of 1% biomass?day(-1) for 84 consecutive days. Fish were vaccinated after two weeks of experimental feeding and bath challenged with live Y.?ruckeri six weeks post-vaccination. Blood and head kidney were sampled at day 0, 13 (1 day pre-vaccination), 15, 55, 59 (day 3 post-challenge (p.c.)), 70 and 84. Vaccination induced significantly increased survival p.c., whereas the β-glucan had no effect on survival in either unvaccinated or vaccinated fish. Expression in head kidney of genes related to the acute phase response, i.e. interleukin-1β (IL-1β), serum amyloid A (SAA), precerebellin, and hepcidin, was significantly different in vaccinated fish receiving β-glucan compared to vaccinated controls at day 3 p.c., while no effect of β-glucan was observed among unvaccinated fish. Significant interaction between β-glucan and vaccination was found for the regulation of IL-1β, tumour necrosis factor-α, interferon-γ, SAA, precerebellin and hepcidin p.c. For SAA, the significant effect of β-glucan in vaccinated fish persisted at day 14 p.c. and 28 p.c. The difference in gene expression among vaccinated fish was mainly observed as down-regulations in vaccinated, β-glucan fed fish compared to up-regulations or no regulation in vaccinated controls. Slightly increased levels of plasma lysozyme activity were found in fish (both unvaccinated and vaccinated) receiving β-glucan at day 3 p.c. compared to control fed groups. This was associated with a faster clearance of Y.?ruckeri in unvaccinated fish receiving β-glucan. In contrast to the trend towards a beneficial effect of β-glucan on plasma lysozyme activity, a trend towards suppression of plasma antibodies was seen in both unvaccinated and vaccinated fish receiving β-glucan. However, the effects of β-glucan were not reflected in the survival curves, and the differences seen in plasma lysozyme activity and antibody levels may have counteracted and set off each other as well as counteracted any potential effect represented by the differences in gene expression found.  相似文献   

3.
In this work, the temperature dependence of the sarco-endoplasmic reticulum Ca(2+) -ATPase (SERCA2) activity from rainbow trout Oncorhynchus mykiss cardiac ventricles was measured and compared with the mammalian SERCA2 isoform. The rate of ATP-dependent Ca(2+) transport catalysed by O. mykiss vesicles was totally abolished by thapsigargin and the Ca(2+) ionophore A(23187) . At warm temperatures (25 and 30° C), the SERCA2 from O. mykiss ventricles displayed the same rate of Ca(2+) uptake. At 35° C, the activity of the O. mykiss enzyme decreased after 20 min of reaction time. The rate of Ca(2+) uptake catalysed by the mammalian SERCA2 was temperature dependent exhibiting its maximal activity at 35° C. In contrast to the rate of Ca(2+) uptake, the rate of ATP hydrolysis catalysed by O. mykiss SERCA2 was not significantly different at 25 and 35° C, but the rate of ATP hydrolysis catalysed by the rat Rattus norvegicus SERCA2 isoform at 35° C was two-fold higher than at 25° C. At low temperatures (5 to 20° C), the rate of Ca(2+) uptake from O. mykiss SR was less temperature dependent than the R. norvegicus isoform, being able to sustain a high activity even at 5° C. The mean ±s.e. Q(10) values calculated from 25 to 35° C for ATP hydrolysis were 1·112 ± 0·026 (n = 3) and 2·759 ± 0·240 (n = 5) for O. mykiss and R. norvegicus, respectively. Taken together, the results show that the O. mykiss SERCA2 was not temperature dependent over the 10 to 25° C temperature interval commonly experienced by the animal in vivo. The Q(10) value of SERCA2 was significantly lower in O. mykiss than R. norvegicus which may be key for cardiac function over the wide environmental temperatures experienced in this eurythermal fish.  相似文献   

4.
5.
Molecular genetic assays can contribute to conservation of aquatic taxa by assessing evolutionary and taxonomic distinctiveness, levels of genetic variation within and between populations, and the degree of introgression with introduced taxa. The Athabasca River drainage of␣western Alberta, Canada is one of only three (and the largest) drainages flowing east of the continental divide that contain native populations of rainbow trout (Salmonidae: Oncorhynchus mykiss). The “Athabasca” rainbow trout has been considered a preglacial relict worthy of special conservation measures. In addition, the native range of Athabasca rainbow trout has seen many instances of introductions of non-native populations since the beginning of the 20th century. We assayed rainbow trout from the Athabasca River drainage, from hatchery populations, and from representative populations in adjacent regions (N = 49 localities) for variation at 10 microsatelite loci to assess the level of evolutionary distinctiveness of Athabasca rainbow trout, and to assess the levels of introgression with non-native hatchery fish. We found that native Athabasca rainbow trout did not form a distinctive genetic assemblage and that the greatest amount of allele frequency variation was attributable to contemporary drainage systems (29.3%) rather than by a Athabasca/non-Athabasca distinction (12.6%). We found that 78% of all fish were confidently assigned to a “wild” rather than a “hatchery” genetic grouping and that most of the inferred introgression with hatchery fish was restricted to a few localities (N = 6). Our results suggest that: (i)␣Athabasca River rainbow trout are likely postglacial immigrants from adjacent populations of the Fraser River, and (ii) that there is no evidence of widespread introgression of hatchery alleles into native Athabasca River drainage rainbow trout.  相似文献   

6.
Boldness, a measure of an individual's propensity for taking risks, is an important determinant of fitness but is not necessarily a fixed trait. Dependent upon an individual's state, and given certain contexts or challenges, individuals may be able to alter their inclination to be bold or shy in response. Furthermore, the degree to which individuals can modulate their behaviour has been linked with physiological responses to stress. Here we attempted to determine whether bold and shy rainbow trout, Oncorhynchus mykiss, can exhibit behavioural plasticity in response to changes in state (nutritional availability) and context (predation threat). Individual trout were initially assessed for boldness using a standard novel object paradigm; subsequently, each day for one week fish experienced either predictable, unpredictable, or no simulated predator threat in combination with a high (2% body weight) or low (0.15%) food ration, before being reassessed for boldness. Bold trout were generally more plastic, altering levels of neophobia and activity relevant to the challenge, whereas shy trout were more fixed and remained shy. Increased predation risk generally resulted in an increase in the expression of three candidate genes linked to boldness, appetite regulation and physiological stress responses - ependymin, corticotrophin releasing factor and GABA(A) - but did not produce a significant increase in plasma cortisol. The results suggest a divergence in the ability of bold and shy trout to alter their behavioural profiles in response to internal and exogenous factors, and have important implications for our understanding of the maintenance of different behavioural phenotypes in natural populations.  相似文献   

7.
1. Primary cultures of rainbow trout brain astroglial cells, prelabelled with [1-14C] polyunsaturated fatty acids (PUFA), were treated with various agents and the effects on cell morphology and n-3 PUFA metabolism were investigated.2. The effects of dibutyryl cAMP on trout astroglial cell cultures were similar to those of dibutyryl cAMP on primary cultures of rat brain astroglia, inducing process-bearing morphology.3. Hydrocortisone had the opposite effect to dibutyryl cAMP on the morphology of the trout astroglial cells, reducing the degree of process-bearing morphology.4. Dibutyryl cAMP increased the percentage of [14C]eicosapentaenoic acid (EPA, 20:5n-3) elongated to 22:5, whereas hydrocortisone increased the percentage of [14C]linolenic acid (LNA, 18:3n-3) desaturated and elongated to 20:5.5. Peroxisome effectors also affected trout astroglial cell morphology with the peroxisomal proliferator, clofibrate, reducing the degree of process formation, whereas the peroxisomal inhibitor, 3-aminotriazole, increased the degree of process formation.6. However, the peroxisomal effectors had similar effects on n-3 PUFA metabolism, reducing the percentages of [14C]LNA converted to 20:5 and 22:5, whereas both increased the percentages of [14C]EPA converted to 22:5 and 22:6.7. We concluded that changes in the morphology of trout astroglial cells in vitro are not directly related to changes in n-3 PUFA metabolism.  相似文献   

8.
9.
The aim of this work was to investigate the response of rainbow trout embryos (Oncorhynchus mykiss) (i.e., survival, size at hatching, time to hatching, malformations) to four incubation temperatures (5.8, 8.9, 14.0 and 16.8°C), taking into account the origin of the male parental genome and comparing pure farmed and F1 embryos (farmed female × wild thermal-resistant male). Several consequences of thermal stress were observed: lower accumulated thermal units (ATU) at hatching at high temperatures, and lower survival, shorter hatched free embryos and less-consumed yolk sac at extreme temperatures. The effect of the thermal-adapted male parental genome was shown only in the lower percentage of incompletely hatched free embryos in the F1 families. It appears that to obtain greater modification of thermal performance during early development, the adapted genome of the wild thermal-resistant population has to be included through maternal inheritance, thus producing a stabilized strain selected for domesticity, growth and thermal adaptation.  相似文献   

10.
11.
The emergence of Biotechnology has provided pharmacologists with a variety of methods for investigating the structure, the function, and the regulation of membrane-bound receptors with a precision that was not imagined even five years ago. These new tools have been developed and used to analyze the known catecholamine β1- and β2 receptors and to discover and study a new subtype, the β-adrenergic receptor. We review here the salient features of each of these three receptors, compare their structural and functional properties, and propose models to explain their differential regulation in time and space. A whole family of proteins has now been found to share with the β-adrenergic receptors their most prominent features, including seven transmembrane domains and coupling with GTP-binding “G” proteins. We therefore propose that the biotechnology-based procedures developed for the β-adrenergic receptors will be well applicable to the other members of this “R7G” family of receptors.  相似文献   

12.
Effects of Hilyses®, fermented Saccharomyces cerevisiae (S. cerevisiae), on growth, body composition and skin mucus immune components in rainbow trout were quantified. Ninety rainbow trout (105 ± 5 g) were randomly assigned to 2 groups in triplicates and fed dietary Hilyses® (5 g kg?1) or control diet without Hilyses® for 50 days. Results of this study demonstrated that growth performance increased significantly by the dietary yeast supplement; however body composition was not affected in treatment group. At the 45th and 50th day of feeding trial, results of mucus samples demonstrated that yeast supplementation in treatment group significantly promoted enzyme activities, namely lysozyme, protease, alkaline phosphatase and esterase compared to control group. Significant increases were also observed in hemagglutination and antibacterial activity against Yersinia ruckeri in fish fed treatment diet. The present study suggests that fermented S. cerevisiae may effectively promote the growth performance and skin non-specific immune parameters in rainbow trout.  相似文献   

13.
To identify virulence-associated genes of a fish pathogen Yersinia ruckeri, we screened a total of 1056 mini-Tn5-Km2 signature-tagged mutants in rainbow trout by immersion challenge. Of 1056, 25 mutants were found survival-defective as they could not be re-isolated from fish kidney 7 days after infection. Mutated gene in F2-4 mutant, one of the 25 mutants, was homologous to uvrY that encodes UvrY response regulator of BarA–UvrY two-component system (TCS). Mutant F2-4 was significantly more sensitive (P < 0.05) to H2O2-mediated killing and was less able to infect Epithelioma papulosum cyprini cells. However, UvrY mutation did not affect survival of F2-4 mutant in the presence of non-immune fish serum and its ability to grow under iron starvation. In a time-course co-infection, mutant F2-4 had lower bacterial loads on day 1 itself, and by day 5 there was nearly a 1,000-fold difference in infection levels of the parent and mutant strains. The barA homolog of Y. ruckeri was PCR-amplified and sequence analyses identified four domains that were characteristic of hybrid histidine kinases. To conclude, the BarA–UvrY TCS contributes to the pathogenesis of Y. ruckeri in its natural host rainbow trout, possibly by regulating invasion of epithelial cells and sensitivity to oxidative stress induced by immune cells.  相似文献   

14.
The effects of l-arginine, and its analogues N ω-nitro-l-arginine methyl ester and N ω-nitro-l-arginine on vascular resistance were investigated in the intact coronary system of an isolated non-working trout heart preparation. l-Arginine, at 10–8 mol · l–1induced a slight vasodilatory effect (max 10%). N ω-nitro-l-arginine methyl ester and N ω-Nitro-l-arginine in the range 10–8–10–4 mol · l–1 caused dose-dependent increases in coronary resistance. The vasodilatory action of l-arginine was abolished when the preparation was pretreated with 10–4 mol · l–1 N ω-nitro-l-arginine or N ω-nitro-l-arginine methyl ester. Nitroprusside alone at 1 mmol · l–1 induced a maximum vasodilation (30%) of the coronary system. Methylene blue a known inhibitor of guanylate cyclase, induced a strong vasoconstriction (already significant at 10–5 mol · l–1) and was able to overcome the vasodilative effect of nitroprusside. The endothelial nitric oxide agonists acetylcholine and serotonin, established in mammalian vessels, also mediate vasodilation in trout coronary system. In 50% of preparations, acetylcholine induced a biphasic response with vasodilation at low concentration (max 15% at 10–8 mol · l–1). Serotonin displayed a dose-response vasodilation in the range 10–8–10–4 mol · l–1 (max 20%). These vasodilative effects were reduced or abolished by 10–4 mol · l–1 l-NA. These data support the existence of NO-mediated vasodilation mechanisms in the trout coronary system. Accepted: 1 July 1996  相似文献   

15.
16.
We evaluated the impact of non-native rainbow trout Oncorhynchus mykiss on a population of endemic Cedarberg ghost frog Heleophryne depressa in the upper Krom River (Olifants-Doring River Catchment, Cape Fold Ecoregion). We compared H. depressa abundance (using kick-sampling and underwater video analysis) and environmental conditions between sites above and below a waterfall that marks the upper distribution limit of O. mykiss. Heleophryne depressa abundance was significantly greater above the waterfall than that below it, and, because there was no significant difference in measured environmental variables, O. mykiss presence is identified as the most likely explanation for the observed decrease in H. depressa abundance.  相似文献   

17.
Whole blood from rainbow trout and carp was subjected to hyperosmotic shock and subsequent beta-adrenergic stimulation (isoprenaline) at different oxygen tension ( PO(2)) and carbon dioxide tension ( PCO(2)) levels with the aim to evaluate changes in red blood cell (RBC) volume, pH and ion concentrations and their ultimate effect on blood O(2) transport characteristics. Hyperosmolality (addition of NaCl) induced RBC shrinkage, which was followed by a regulatory volume increase (RVI) that was larger at low than at high PO(2)and more complete in carp than in trout. Carp RBC showed practically full volume recovery within 140 min at low PO(2)and partial recovery at high PO(2), whereas RVI was partial under all PO(2)and PCO(2)conditions in trout. The RVI increased intracellular [Na(+)], water content, and, in carp, also pH (pHi), suggesting activation of Na(+)/H(+) exchange. In trout RBCs, activation of RVI was rapid but succeeded by deactivation. In carp RBCs, activation of Na(+) influx was slower but it continued, allowing full volume recovery. Shrinkage of the RBCs was associated with only minor decreases in blood oxygen saturation and oxygen affinity in both species. Thus, the oxygen affinity decrease expected on the basis of the increased concentration of intracellular haemoglobin and organic phosphates was small, and it appeared to some extent countered during RVI by an oxygen affinity increase via increased pHi. Addition of isoprenaline increased RBC volume and pHi and increased Hb oxygen saturation. The beta-adrenergic response was stronger at low compared to high PO(2) and at high compared to low PCO(2). The PO(2) dependency was largest in carp, whereas the PCO(2) (pH) dependency was more expressed in trout. The adrenergic response of trout RBCs was similar under isoosmotic and hyperosmotic conditions. In carp RBCs, the response was absent at high PO(2) under isoosmotic conditions, but interestingly it could be induced under hyperosmotic conditions. The data suggest that the RBC shrinkage occurring in fish moving from freshwater to seawater has minimal impact on blood O(2) binding properties.  相似文献   

18.
The motility of salmonid sperm is pH-sensitive and the buffering capacity of the seminal plasma is low. The objective of the present study was to determine the extent to which sperm contribute to the buffering capacity of whole steelhead (Oncorhynchus mykiss) semen. To determine the buffering capacity, semen and seminal plasma samples were titrated with HCl and pH measurements taken at 1-2 min. The buffering capacity of semen was not different from that of seminal plasma over the pH range 7.5 to 8.5 and was approximately 15% to 20% less over the range 6.0 to 7.0. Comparable results were obtained for the semen and seminal plasma of the chinook salmon (Oncorhynchus tshawytscha). To assess whether the intracellular environment could influence the buffering capacity, the effects of cell disruption with n-butanol and Triton X-100 (TX-100) were determined. Over the pH range 7.5 to 8.5, the presence of n-butanol or TX-100 resulted in a doubling of the buffering capacity of the semen; TX-100, but not n-butanol, increased semen buffering capacity over the pH range 6.0 to 7.0. To determine whether the sperm's intracellular compartment might contribute to the buffering capacity over a longer duration, semen and seminal plasma samples were acidified with HCl and the pH measured over several hours. These data suggest that intact sperm contribute no more than about 25% to the buffering capacity of whole semen. The buffering capacity of steelhead semen and seminal plasma were comparably and modestly temperature sensitive. The results suggest that the sperm may contribute to the buffering capacity of the semen over a physiological pH range, however, if so, the effect is relatively small.  相似文献   

19.
The important and diverse biological functions of β-adrenergic receptors (βARs) have promoted the search for compounds to stimulate or inhibit their activity. In this regard, unraveling the molecular basis of ligand binding/unbinding events is essential to understand the pharmacological properties of these G protein-coupled receptors. In this study, we use the steered molecular dynamics simulation method to describe, in atomic detail, the unbinding process of two inverse agonists, which have been recently co-crystallized with β(1) and β(2)ARs subtypes, along four different channels. Our results indicate that this type of compounds likely accesses the orthosteric binding site of βARs from the extracellular water environment. Importantly, reconstruction of forces and energies from the simulations of the dissociation process suggests, for the first time, the presence of secondary binding sites located in the extracellular loops 2 and 3 and transmembrane helix 7, where ligands are transiently retained by electrostatic and Van der Waals interactions. Comparison of the residues that form these new transient allosteric binding sites in both βARs subtypes reveals the importance of non-conserved electrostatic interactions as well as conserved aromatic contacts in the early steps of the binding process.  相似文献   

20.
Post-hatch fishes lack a functional gill and use cutaneous surfaces for exchange with the surrounding environment. The ionoregulatory hypothesis posits that ionoregulation is the first physiological process to be limited by cutaneous exchange, necessitating its shift to the gills. We hypothesized that the ontogeny of branchial ammonia excretion (Jamm) is coupled to Na+ uptake () in accordance with the current model for exchange in freshwater. Using divided chambers, branchial and cutaneous Jamm, and oxygen consumption (MO2) by larval rainbow trout were assessed. Following hatch, the skin accounted for 97% and 86% of total Jamm and , respectively. Jamm and shifted to the gills simultaneously at 15 days post-hatch (dph) and were highly correlated (R2 = 0.951) at the gills, but not the skin, over development. Contrastingly, MO2 shifted significantly later at 27 dph, in agreement with the ionoregulatory hypothesis. Moreover, the mRNA expression and/or enzymatic activity of Rhesus proteins, Na+/H+-exchanger, H+-ATPase, Na+/K+-ATPase and carbonic anhydrase, all key components of the -exchange system, increased in the gills over larval development. We propose that the ontogeny of branchial occurs as exchange and provide evidence for a novel element to the ionoregulatory hypothesis, the excretion of potentially lethal metabolic ammonia.  相似文献   

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