The effect of humic substances on the toxicity of aluminium to adult rainbow trout, Oncorhynchus mykiss (Walbaum)

Some physiological parameters were measured in adult rainbow trout during a 10-day exposure to 180 μg Al_total l⁻¹ in acid water (pH 4.7) with or without humic substances (10 mg l⁻). The fish were acclimatized to pH 5.0 for 7 days prior to the experimental treatments.
Chemical analyses revealed that, in the presence of human substances, 74–80% of the A1 was organic bound, while in the absence of humic substances most of the Al(987percnt;) occurred in the inorganic form.
Al bound to humic substances (13–150 μg l⁻¹) did not alter the plasma NaCl-concentration, nor the haematocrit value, of rainbow trout during an exposure period of 10 days. This contrasts with the high death rate obtained within 2–3 days when most of the A1 (175 μg l⁻¹) was in the inorganic form. The lethality was accompanied by a 25% decrease in the plasmaconcentration of NaCl and a doubling of the haematocrit value. Bulk analysis revealed that when the metal was present in inorganic forms the total Al content of the gills (75 μg A1 g⁻¹ wet weight) was 15 times higher than when it was present as bound to the humic substances. These experiments showed that the accumulation of A1 at the gills was accompanied by physiological disturbances, both being a function of the chemical speciation of Al.     

The accumulation of dietary aluminium by rainbow trout, Oncorhynchus mykiss, at high exposure concentrations

A high oral concentration of 10g Al kg⁻¹ dry weight promoted toxicant accumulation in the muscle, gill, liver, kidney and mucus of trout. One mortality occurred and only a small proportion of the exposure dose was retained by the fish. The limited acute oral toxicity of Al implies that contamination levels found in food species are unlikely to be acutely toxic to wild trout.     

Factors affecting male potency in pooled gamete crosses of rainbow trout,Oncorhynchus mykiss

Synopsis Numbers of offspring produced by genetically marked male and female rainbow trout,Oncorhynchus mykiss were determined by an electrophoretic analysis of 1713 progeny from crosses produced by premixing gametes from different parents prior to insemination and associated full- and half-sib controls. We examined whether male potency, defined as the ability of males to sire progeny when their semen is pooled with that of other males, is affected by interaction with female gametes, concentration of sperm cells and the timing of semen application. Male potency differed significantly and was not affected by which of two females was involved in either of two sets of experiments. The differential between males decreased significantly when sperm concentrations were equalized. The first male sired over 75% of progeny when semen from four males was added sequentially to ova at 30 s intervals in each of two experiments. The lack of significant deviations of marker genotypes from expected Mendelian segregation in full-sib families suggested that there was no differential survival of progeny with specific marker genotypes. Furthermore, there was no correspondence between the survival of progeny of specific males in control crosses and the number of progeny sired in matings where sperm was premixed prior to insemination. Thus. variation in male reproductive success appeared the result of differential fertilization rates.     

The effects of diet composition and ration on biotransformation enzymes and stress parameters in rainbow trout, Oncorhynchus mykiss

Juvenile rainbow trout (Oncorhynchus mykiss) were fed one of three isoenergetic diets varying in protein (35-55%) and lipid content (8-18%), at full satiation levels or half rations for 6 weeks in order to investigate the effects of diet on baseline stress parameters and biotransformation enzyme activity. Growth was greatest in fish fed to satiation on a low protein and high lipid diet. Stress parameters, including plasma lactate, glucose and cortisol concentrations were not significantly affected by dietary treatment or ration. Basal biotransformation enzymes, including glutathione S-transferase (GST) and ethoxyresorufin O-deethylase (EROD) activity, were also unaffected by dietary treatment. Fish exposed to the biotransformation enzyme inducer beta-naphthoflavone did not exhibit an alteration in stress indicators or GST activity; however, EROD activity was increased (87- to 210-fold) in fish receiving all diets and rations. The results of the present study indicate that, unlike mammals, fish may be more recalcitrant to different levels of ingestion of isoenergetic diets varying in protein and lipid concentration with respect to stress responses and the maintenance of basal titers of biotransformation enzymes and their induction.     

Measurement of branchial vascular space of trout,Oncorhynchus mykiss: effects of adrenaline

Summary Using the isolated-perfused head preparation at a constant flow rate, hemodynamic effects of adrenaline were studied in trout gills. The calculation of the vascular spaces was performed with the isotopic pulse technique allowing measurement of the distribution space of the tracer.The results show that the branchial arterial circuit was cleared more quickly than the branchial venous and cephalic circuits. Adrenaline addition significantly increased the volume of the branchial arterial circuit at the expense of the venous circuit, illustrating the closing of arterio-venous sphincters under catecholamine control. The increase of the arterial volume could be explained by a vasodilation of the arterial circuit, rather than resulting from lamellar recruitment. Furthermore, the flow rate of the cephalic circuit represented 5% of the total branchial flow rate.Abbreviations dpm radioactive decay per minute - F flow rate - HSA human serum albumin - T_1/2 half-time clearance - V distribution space     

Copper exposure impairs intra- and extracellular acid-base regulation during hypercapnia in the fresh water rainbow trout (Oncorhynchus mykiss)

In order to evaluate the impact of water-borne copper on acid-base regulation in fresh water rainbow trout, chronically cannulated fish were exposed to copper (0.6 mg 1⁻¹), hypercapnia (water PCO₂ of 6 mmHg) or a combination of copper and hypercapnia, while a fourth untreated group served as the control. Blood samples obtained at 0 h, 4 h and 24 h were analysed for acid-base status, ion concentrations and respiratory parameters. Tissue samples from caudal skeletal muscle, liver and gill filaments were examined for intracellular acid-base status, ion- and water contents, and copper concentration. Exposure to copper alone elicited a small extracellular metabolic alkalosis, no changes in arterial PO₂, and a minor decrease in plasma ion concentrations. Hypercapnia alone increased arterial PCO₂ from approximately 2 mmHg to 7.2 mmHg, but the extracellular respiratory acidosis present at 4 h was almost completely compensated at 24 h due to an increase in plasma bicarbonate concentration [HCO₃ ⁻] from 8.1 mM to 24.4 mM. Combined exposure to hypercapnia and copper resulted in a slightly larger acidosis at 4 h, and the fish failed to restore extracellular pH at 24 h, because plasma [HCO₃ ⁻] only increased to 16.3 mM. Fish exposed to hypercapnia and copper also showed a delayed recovery of intracellular pH in skeletal muscle, compared to fish exposure to hypercapnia only. Thus, copper exposure impaired both extracellular and intracellular acid-base regulation during hypercapnia. When seen in connection with only minor effects of copper on osmoregulatory and respiratory parameters, the reduced ability to regulate acid-base suggests that acid-base regulation may be one of the most copper-sensitive branchial functions. Accepted: 18 August 1998     

Production of recombinant leptin and its effects on food intake in rainbow trout (Oncorhynchus mykiss)

Leptin is a key factor for the regulation of food intake and energy homeostasis in mammals, but information regarding its role in teleosts is still limited. There are large differences between mammalian and teleost leptin at both gene and protein levels, and in order to characterize the function of leptin in fish, preparation of species-specific leptin is therefore a key step. In this study, full-length cDNA coding for rainbow trout leptin was identified. In spite of low amino acid sequence similarity with other animals, leptin is highly conserved between trout and salmon (98.7%). Based on the cDNA, we produced pure recombinant trout leptin (rt-leptin) in E. coli, with a final yield of 20 mg/L culture medium. We then examined the effects of intraperitoneal (IP) injection of rt-leptin on feeding behavior and gene expression of hypothalamic NPY and POMCs (POMC A1, A2 and B) in a short-term (8 h) experiment. The rt-leptin suppressed food intake and led to transient reduction of NPY mRNA levels, while the expression of POMCs A1 and A2, was elevated compared with vehicle-injected controls. These results for rainbow trout are the first that describe a physiological role of leptin using a species-specific orthologue in teleosts, and they suggest that leptin suppresses food intake mediated by hypothalamic regulation. This anorexic effect is similar to that observed in mammals and frogs and supports that the neuroendocrine pathways that control feeding by leptin are ancient and have been conserved through evolution.     

Two-substrate kinetic analysis: a novel approach linking ion and acid-base transport at the gills of freshwater trout,Oncorhynchus mykiss

Summary The novel application of a two-substrate model (Florini and Vestling 1957) from enzymology to transport kinetics at the gills of freshwater trout indicated that Na⁺/acidic equivalent and Cl^-/basic equivalent flux rates are normally limited by the availability of the internal acidic and basic counterions, as well as by external Na⁺ and Cl^- levels. Adult rainbow trout fitted with dorsal aortic and bladder catheters were chronically infused (10–16 h) with isosmotic HCl to induce a persistent metabolic acidosis. Acid-base neutral infusions of isosmotic NaCl and non-infused controls were also performed. Results were compared to previous data on metabolic alkalosis in trout induced by either isosmotic NaHCO₃ infusion or recovery from environmental hyperoxia (Goss and Wood 1990a, b). Metabolic acidosis resulted in a marked stimulation of Na⁺ influx, no change in Cl^- influx, positive Na⁺ balance, negative Cl^- balance, and net H⁺ excretion at the gills. Metabolic alkalosis caused a marked inhibition of Na⁺ influx and stimulation of Cl^- influx, negative Na⁺ balance, positive Cl^- balance, and net H⁺ uptake (=base excretion). Mean gill intracellular pH qualitatively followed extracellular pH. Classical one-substrate Michaelis-Menten analysis of kinetic data indicated that changes in Na⁺ and Cl^- transport during acid-base disturbance are achieved by large increases and decreases in J_max, and by increases in K_m. However, one-substrate analysis considers only external substrate concentration and cannot account for transport limitations by the internal substrate. The kinetic data were fitted successfully to a two-substrate model, using extracellular acid-base data as a measure of internal HCO ₃ ^- and H⁺ availability. This analysis indicated that true J_max values for Na⁺/acidic equivalent and Cl^-/basic equivalent transport are 4–5 times higher than apparent J_max values by one-substrate analysis. Flux rates are limited by the availability of the internal counterions; transport K_m values for HCO ₃ ^- and H⁺ are far above their normal internal concentrations. Therefore, small changes in acid-base status will have large effects on transport rates, and on apparent J_max values, without alterations in the number of transport sites. This system provides an automatic, negative feedback control for clearance or retention of acidic/basic equivalents when acid-base status is changing.Abbreviations Amm total ammonia in water - DMO 55-dimethyl-24-oxyzolidine-dione - J_in unidirectional inward ion movement across the gill - J_out unidirectional outward ion movement across the gill - J_net net transfer of ions (sum of J_in and J_out) across the gill - J_max maximal transport rate for ion - K_m inverse of affinity of transporter for ion - PIO₂ partial pressure of oxygen in inspired water - P_aCO₂ partial pressure of carbon dixide in arterial blood - TAlk titratable alkalinity of the water - PEG polyethylene glycol - NEN New England Nuclear     

Effects of low pH on the chorion of rainbow trout, Oncorhynchus mykiss, and brown trout, Salmo trutta f. fario

Morphological studies on the effect of low pH on egg shells (chorion) of rainbow trout, Oncorhynrhus mykiss Walbaum (formerly Salmo gairdneri ), and brown trout, Salmo trutta f. fario L., showed that the plugs of the outer layer of the chorion, which block the channels of the underlying layer, developed distinctive vacuolization at low pH exposure. This may lead to loss of chorional semi-permeability. Chorions were incompletely degraded at low pH inducing hatching problems. Partially hatched alevins showed only a small local zone of dissolution of the chorion around the head of the embryo preventing the larvae from being freed.     

Changes in tissue and mitochondrial membrane composition during rapid growth, maturation and aging in rainbow trout, Oncorhynchus mykiss

Membrane compositions, particularly of mitochondria, could be critical factors in the mechanisms of growth and aging processes, especially during phases of high oxidative stress that result in molecular damage. In the present study, liver and mitochondrial membrane phospholipid (PL) compositions were analyzed in rainbow trout during its four first years of life, a period characterized by rapid growth and high oxidative stress. Specifically, farmed fish of three ages (1-, 2- and 4-years) were studied, and PL compositions of whole liver and liver mitochondria, and fatty acid compositions of individual PL classes were determined. Liver mitochondrial membranes showed a PL composition different to that of the whole tissue suggesting adaptation of cell and subcellular membranes to specific functions. Individual PL had characteristic fatty acid compositions that were similar in whole liver and mitochondrial membranes. Whole liver and mitochondria showed increased lipid peroxidation with age along with changes in membrane PL fatty acid compositions. Most PL classes showed similar changes in fatty acid composition among the age groups, with reduced proportions of docosahexaenoic acid (DHA) and, generally, concomitantly increased levels of monounsaturated fatty acids, which together resulted in reduced peroxidation index (PIn). However, total polyunsaturated fatty acid (PUFA) content did not change significantly with age due to increased eicosapentaenoic acid, docosapentaenoic acid and, in most PL, increased n−6 PUFA. These results suggest there may be oxidation of PL DHA with compensatory mechanisms to maintain membrane fluidity and function. However, modification of fatty acid composition of specific PLs, such as cardiolipin, could affect the electron transport chain efficiency and propagate the oxidative reaction throughout the cell. In addition, both the content and fatty acid composition of sphingomyelin, which has been suggested as a possible mediator of cell dysfunction and apoptosis, changed with age differently to the other PL classes. Moreover, these changes showed different trends between mitochondria and whole liver. These data suggest there is marked oxidative stress associated with rapid growth and maturation in rainbow trout. Changes observed in membrane lipids point to their possible participation in the processes involved in this species response to oxidative stress and damage accumulation rate.     

Compliance and smooth muscle reactivity of rainbow trout (Oncorhynchus mykiss) vessels in vitro

Systemic veins have a profound influence on cardiac output in mammals. Venoregulatory mechanisms have not been adequately studied in fish and their existence has been questioned. In the present study, two characteristics of vascular mechanics, compliance and agonist-induced tension development, were investigated in rainbow trout vessels in vitro. Rapid compliance in the anterior cardinal vein and efferent branchial artery was calculated from step-wise changes in the volume-pressure curve of isolated vessel segments. Agonist-induced tension development was examined in four veins; anterior and posterior cardinals, intestinal and duct of Cuvier. Venous compliance was not altered in response to epinephrine, norepinephrine or angiotensin II, while efferent branchial artery compliance was decreased by 10^-6 mol·l^-1 epinephrine and norepinephrine but not angiotensin II. The ratios of venous to arterial compliance in vessels from two rainbow trout strains were similar (21:1 and 32:1) and consistent with the ratio reported for mammalian viens (24:1). Trout veins contracted in response to agonists in both an, agonist- and vesselspecific manner. The greatest tension per vessel wet weight was produced in anterior cardinal vein. The response pattern of anterior cardinal vein and duct of Cuvier were similar; acetylcholine, arginine vasotocin, epinephrine and norepinephrine, and the thromboxane A₂ agonist, U-44,069, produced approximately identical contractions, whereas angiotensin II was virtually ineffective. Conversely, angiotensin II was more potent than epinephrine in posterior cardinal vein. In cumulative dose-response experiments, epinephrine was equipotent in anterior cardinal vein and duct of Cuvier, whereas the latter was less sensitive to acetylcholine. Both atrial natriuretic peptide and sodium nitroprusside relaxed precontracted veins. This is the first study to determine compliance in fish vessels and the contractile nature of different rainbow trout veins. These findings suggest that venous tone and therefore cardiac output in fish may be regulated by neural or humoral mechanisms.Abbreviations ACH acetylcholine - ACV anterior cardinal vein - ANG II salmon asn¹-val⁵ angiotensin II - ANP rat atrial natriuretic peptide - AVT arginine vasotocin - DNR Department of Natural Resources - DOC duct of Cuvier - EBA efferent branchial artery - EC₅ threshold dose producing 5% maximal contraction - EC₅₀ dose producing 50% maximal contraction - EPI epinephrine - HI K⁺ 80 mmol·l^-1 - KCl IV, intestinal vein - NEPI norepinephrine - PBS phosphate buffered saline - PCV posterior cardinal vein - SNP sodium nitroprusside - U-44,069 thromboxane A₂ agonist     

Mechanisms of aluminium extraction and accumulation at the gills of rainbow trout, Oncorhynchus mykiss (Walbaum), in acidic soft water

Rainbow trout were fitted with latex masks for the measurement of ventilatory flow rate (V?_w) and with opercular catheters for sampling expired water from close to the branchial surface. Fish were exposed for 6 h to pH 5.1, 4.7 or 4.1 in the presence (138 μg l ¹) or nominal absence (1 μg 1^–1) of Al. Inspired and expired Al concentrations and water pH were measured via the opercular catheters. Gills were sampled for accumulated Al at the end of the experiments. V?_w increased during Al exposures at all three pHs. However, in the absence of Al, V?_w increased only at pH 4.1. Aluminium extraction from the water and Al accumulation on the gills were highest at inspired pH 5.1 and lowest at pH 4.1, and correlated well with expired pH, which was 0.2–0.7 pH units higher than inspired pH. Gill Al accumulations amounted to only about one-tenth of deposition calculated from Al extraction from the water and V?_w, and gill Al was tightly bound to the branchial surface. Calculations of Al solubility, oversaturation, and species composition were made using measured expired pH values, and were compared with Al extraction from the water and measured gill Al concentrations. In general, these analyses indicated that reduced Al solubility near the gills is a reasonable explanation of Al extraction from the water, and that Al(OH)₂⁺ and Al(OH)₃° are the Al species most likely to interact initially at the gills. It is suggested that mucus sloughing removes most precipitated Al, and that only the charged form persists, bound to structural elements on the gill surface. A model incorporating these results, and pH changes in the fish gill micro-environment in general, is presented to explain previously-reported ionoregulatory and respiratory effects of Al.     

Haematological disturbances and osmotic shifts in rainbow trout,Oncorhynchus mykiss (Walbaum) under acid and aluminium exposure

Summary Elevated values of haematocrit were observed in rainbow trout (Oncorhynchus mykiss) during combined acid and aluminium exposure. Possible causes of this, i.e., decreased plasma volume, swelling of erythrocytes, and/or mobilization of erythrocytes into the blood were investigated. Slight haematocrit increases (10–20%) during mild acid stress (pH 5.0, 25 mol Ca²⁺·1^-1) were mostly caused by osmotic shifts. Both swelling of erythrocytes rocytes and a significant decrease of the plasma volume were demonstrated in fish at pH 5.0. These osmotic disturbined were greater during acid exposure (pH 5.0) combined with Al (60 g·1^-1; 200 g·1^-1). In addition, numbers of erythrocytes increased by 40% compared to acid exposure, which contributed to the severe haematocrit rise (35%) during Al exposure. A contraction of the spleen releasing erythrocytes into the blood is suggested to occur as an adrenergic response to hypoxia, which is observed in fish acutely exposed to Al.Abbreviations BV blood volume - ECFV extracellular fluid volume - ICFV intracellular fluid volume - ISFV interstitial fluid volume - MCHC mean cell haemoglobin concentration - MCV mean cell volume - PV plasma volume     

Formation of the vitelline envelope precedes the active uptake of vitellogenin during oocyte development in the rainbow trout,Oncorhynchus mykiss

In order to study the initial formation of the vitelline envelope and the appearance of vitellogenin in oocytes of rainbow trout, females were sampled monthly from 19 to 5 mo before ovulation. lmmunohistochemistry revealed that the formation of the vitelline envelope starts when the oocytes reach a diameter of about 450 μm. Oocytes of this size were first found in females sampled a year before ovulation at the time when plasma levels of estradiol-17β increased from 0.2 to 0.6 ng/ml. An antiserum directed against vitellogenin crossreacted with small vesicles (around 2 μm) present just inside the oolemma, when the oocytes reached a diameter of 600 μm. This was interpreted as an active uptake of vitellogenin. Oocytes of this size were first found in females sampled 9 mo before ovulation at the time when estradiol 17β levels increased from 0.6 to 1.0 ng/ml and the gonadal somatic index was doubled. Oocytes with a diameter of 600 μm had an immunoreactive vitelline envelope with a thickness of about 3 μm. It is apparent that the initial formation of the vitelline envelope starts before the active uptake of vitellogenin and that the low previtellogenic plasma levels of estradiol-17β observed in females are of physiological significance. © 1994 Wiley-Liss, Inc.     

Characterization and expression of embryonic globin in the rainbow trout, Oncorhynchus mykiss: Intra-embryonic initiation of erythropoiesis

When fractionated by reverse-phase high performance liquid chromatography (HPLC), the embryonic hemoglobin of the rainbow trout, Oncorhynchus mykiss, consisted of eight globins different from adult globins in terms of retention time. Amino acid sequences of the N-terminal regions of some globins were determined. In addition, four cDNA clones for embryonic globins from 10-day embryos were isolated (at 15 degrees C), sequenced and the amino acid sequences predicted. In comparison with the sequences of previously characterized globins, they corresponded to two alpha-type and two beta-type globins and therefore were named em.alpha-1, em.alpha-2, em.beta-1 and em.beta-2. The N-terminal 36 amino acids of one (E2) of the embryonic globins isolated by HPLC were identical to those of the sequence deduced from a cDNA, em.beta-2. The phylogenetic relationship between the embryonic globins and other globins previously reported was discussed. The present study is the first demonstration of amino acid sequences of embryonic globins in a teleost. To understand the initiation of erythropoiesis in the early development of the rainbow trout, histochemistry using o-dianisidine/hydrogen peroxide, immunohistochemistry using an antibody against embryonic hemoglobin, and northern blotting and whole embryo in situ hybridization using antisense RNA probe for em.beta-2 were performed. Embryonic globin mRNA, globin and hemoglobin appeared first in the anterior part of the intermediate cell mass (ICM) located in the median line beneath the notochord of embryos 6-7 days after fertilization at 15 degrees C (Vernier's stages 16-20). Shortly after that, the expression signal extended to the posterior part of the ICM and spread out laterally to blood islands on the posterior yolk sac. Thus, the initiation of erythropoiesis in the early embryo of rainbow trout is intraembryonic.     

The effects of repeated physical stress or fasting on catccholamine storage and release in the rainbow trout, Oncorhynchus mykiss

Rainbow trout, Oncorhynchus mykiss, were subjected to either physical stress (twice daily chasing to exhaustion for 5 days) or a period of 2 months of fasting. Following these treatments, the levels of catecholamines, adrenaline and noradrenaline, stored within the kidney and posterior cardinal vein (PCV) were determined. The ability of the catecholamine-storing chromaffin cells to release catecholamines in response to cholinergic stimulation was measured using an in situ saline-perfused PCV preparation. In the physically stressed fish, the concentration (μg catecholamine g^?1 tissue) of noradrenaline within the anterior and middle thirds of the kidney increased; the concentration of adrenaline was unchanged in all tissues. The content (μg) of noradrenaline or adrenaline, within the various tissues, was similar in both groups of fish with the exception of a higher noradrenaline content in the middle third of the kidney in the physically stressed fish. The total catecholamine content (μg catecholamine) of these tissues (kidney+PCV) was unaffected by physical stress. With the exception of a lower concentration of adrenaline in the middle third of the kidney, the concentrations of catecholamines were unaffected by fasting. There was a trend towards a greater content (μg) of noradrenaline within all of the tissue regions of the fed fish, however, a significant difference was only observed in the anterior third of the kidney. The content of adrenaline in the fed fish was greater in all regions of the kidney as well as the middle third of the PCV. The total catecholamine content (kidney + PCV) was lower in the fasted fish owing to significantly lower PCV and kidney masses. Prolonged physical stress caused a decrease in the responsiveness of the chromaffin cells to the cholinoceptor agonist carbachol (10^?8 to 10^?4mol). The ED₅₀ (the dose of carbachol required to elicit a half maximal response) for catecholamine release was 0·96 ± 10^?6mol carbachol in the physically stressed fish and 0·84 ± 10^?7 in the control fish. Fasting did not alter the pattern of catecholamine release. The ED₅₀ values were 0·96 ± 10^?7 and 1·24 ± 10^?7 mol for fasted and fed fish, respectively. Thus, a physical stress affected both catecholamine storage and release whereas fasting affected only storage and not the release process.     

Paraquat and menadione exposure of rainbow trout (Oncorhynchus mykiss)--studies of effects on the pentose-phosphate shunt and thiamine levels in liver and kidney

Possible xenobiotic interactions with thiamine were studied in salmonid fish, by repeatedly injecting two model substances, paraquat and menadione, into juvenile rainbow trout (Oncorhynchus mykiss). These two substances were chosen because of their well-known ability to redox-cycle and cause depletion of NADPH in several biological systems. Depletion of NADPH increases metabolism through the pentose-phosphate shunt and may thereby increase the need for thiamine diphosphate by heightened transketolase activity. A special food was produced with lower thiamine content than commercial food, usually enriched with thiamine, which could mask an effect on the thiamine level. After 9 weeks of exposure, glucose-6-phosphate dehydrogenase, transketolase, glutathione reductase and ethoxyresorufin O-deethylase were analysed in liver and kidney cellular sub-fractions as well as analysis of total thiamine concentrations in liver, kidney and muscle. The results showed that paraquat caused a large increase in hepatic glutathione reductase activity and induced hepatic glucose-6-phosphate dehydrogenase activity, i.e., the rate-limiting enzyme in the oxidative part of the pentose-phosphate shunt. Despite this paraquat exposure did not affect transketolase activity and total thiamine concentration.     

Substrate mobilization and hormonal changes in rainbow trout (Oncorhynchus mykiss,L.) and common carp (Cyprinus carpio,L.) during deep hypoxia and subsequent recovery

Common carp (at 20°C) and rainbow trout (at 15°C) were fitted with an indwelling cannula in the dorsal aorta. The fish were exposed to a controlled decline of waterpO₂ followed by 90 min deep hypoxia at 0.3 kPa (carp) or 4.8 kPa (trout). Thereafter, normoxic recovery was monitored in both species for 48 h. At regular intervals blood samples were analysed for glucose, lactate, free fatty acids, adrenaline, noradrenaline and cortisol. The oxygen restriction was maximal in both species and resulted in a significant increase of plasma lactate levels. In carp, adrenaline, noradrenaline and cortisol levels increased to 2, 50, and 753 ng·ml^-1 respectively during anoxia, whereas in trout these hormones increased to 12, 8 and 735 ng·ml^-1 respectively during hypoxia. In hypoxic trout, the plasma levels of glucose (3 mol·l^-1) were increased modestly whereas levels of free fatty acids (0.25 mmol·l^-1) were decreased to 0.15 mmol·l^-1. In carp, however, a marked and prolonged hyperglycaemia (from 5 to 10 mmol·l^-1) and a significant continuous depression of plasma levels of free fatty acids (from 0.4 to 0.2 mmol·l^-1) were observed indicating a difference in metabolic organization. It is suggested that hyperglycaemia is likely to be the result of hepatic glycogenolysis, stimulated by circulating catecholamines and a stimulation of gluconeogenesis by cortisol during recovery. The mechanism for the decline of plasma levels of free fatty acids is most probably a reduction of lipolytic activity, which appears to be an adaptation to hypoxia.     

Use of androgenesis for estimating maternal and mitochondrial genome effects on development and oxygen consumption in rainbow trout, Oncorhynchus mykiss

Chromosome set manipulation was used to produce rainbow trout, Oncorhynchus mykiss, with identical nuclear backgrounds, but different maternal backgrounds to determine mitochondrial effects on development rate and oxygen consumption. Significant differences in development rate and oxygen consumption were observed between groups from different females. Development rates ranged from a mean of 317.97 degree days (°d) to 335.25 °d in progeny from different females. Mean oxygen consumption rates ranged from 3.31 μmol O₂ g^− 1 wet mass h^− 1 to 9.66 μmol O₂ g^− 1 wet mass h^− 1. Oxygen consumption and development rate analysis revealed the two slowest developing groups had the highest oxygen consumption rates. Development rate differences between second generation clonal females indicate that mitochondrial genomes play a significant role on early development and are comparable to development rate differences between clonal lines of rainbow trout. These results indicate that selection for mitochondrial genomes could increase growth rates and possibly food conversion ratios in aquaculture species.