Comparative ultrastructure of the zona radiata from eggs of six species of salmonids

Summary The zona radiata from unactivated and activated eggs from chinook salmon (Oncorhynchus tshawytscha), chum salmon (O. kisutch), pink salmon (O. gorbuscha), brown trout (Salmo trutta), rainbow trout (S. gairdneri) and lake trout (Salvelinus namaycush) were examined using scanning and transmission microscopy. The zona radiata in all species examined consisted of an outer adhesive coating, a thin densely staining zona radiata externa with pore canal plugs and a thick, fibrous zona radiata interna with a fibrous network on the inner surface. There was a two layer adhesive coating over the zona radiata externa in all species except pink salmon in which only one layer was observed. There were structural differences among species in the adhesive layer, zona radiata externa and plugs in the pore-canal openings.Scientific Journal Series, Paper No. 14,627, Minnesota Agricultural Experiment StationPartially funded by Minnesota Sea Grant NA-82-AA 12-000-39, Project RF-12, Minnesota Sea Grant Contribution 168     

Fine structures of oocyte envelopes of three related cobitid species in the genus Iksookimia (Cobitidae)

Fine structures of the oocyte envelope (zona radiata) in three spined loaches, Iksookimia longicorpus, I. hugowolfeldi, and I. yongdokensis, are examined and compared. The zona radiata surrounding the oocyte is composed of two layers, a zona radiata externa, which comprised the outermost zona radiata (Z₁) of a homogeneous less electron dense single layer and the middle zona radiata (Z₂) of a homogeneous more electron dense single layer, and a zona radiata interna, which comprised the innermost zona radiata (Z₃) of heterogeneous electron-dense multilayers. Especially, the surface of the outermost zona radiata (Z₁) showed a morphological difference in its external appearance among the species. In the surface structures of Z₁, I. yongdokensis had a round granule appearance, and both I. hugowolfeldi and I. longicorpus were villus in morphology. In the villus appearance of these two species, however, there were clear differences between I. hugowolfeldi and I. longicorpus: the former had a few short thin villi, 1.0–1.7 μm in length, but in the latter species the villi were numerous, long, and thick, 2.0–2.5 μm long. The variety of such structures in these three species of Iksookimia may be a useful aid in taxonomic relationships and closely related to their habitats. Received: February 15, 2000 / Revised: August 3, 2000 / Accepted: September 3, 2000     

Immunohistochemical analysis of the vitellogenin response in the liver of Atlantic salmon exposed to environmental oestrogens

Induction of vitellogenin (Vtg) in oviparous vertebrates has been used as a biomarker of response for environmental oestrogens. This study reports the cellular localization of oestrogen- and xenoestrogen-induced Vtg synthesis in the liver of juvenile Atlantic salmon (Salmo salar). Paraffin-embedded liver sections were incubated with homologous monoclonal antibody against Atlantic salmon Vtg. Following intraperitoneal (ip) exposure of fish to estradiol-17beta E₂; 5 mg kg-1 or 4-nonylphenol NP; 125 mg kg-1, Vtg induction was primarily demonstrated immunohistochemically in the cytoplasm of hepatocytes, endothelial cells and within hepatic sinusoids. Vtg staining of hepatocytes was not evenly distributed, as there was a high degree of polarization toward the sinusoid. The intensity of positive Vtg staining was stronger in the liver sections of E₂-treated fish, compared with NP-treated fish. Hepatocytes of E₂-, NP- and vehicle (control)-treated fish showed normal cellular structures, thus showing no evidence of histopathological changes. In parallel, indirect enzyme-linked immunosorbent assay (ELISA) and immunoblot analysis of plasma Vtg levels show significant induction of Vtg in E₂- and NP-treated fish, as compared with untreated (control) fish. The present study demonstrates the applicability of immunohistochemistry in studies of cellular structures, processes and responses of fish exposure to oestrogen and oestrogen-mimicking compounds.     

Suppressive Subtraction Libraries to Identify Interferon-Inducible Genes in Fish

Previous attempts to identify genes in fish that respond to virus infection or interferon induction have not been particularly productive. Since these genes are very important in developing strategies to control disease outbreaks in aquaculture, we began a study of interferon-inducible genes in fish using suppressive subtraction hybridization to construct cDNA libraries enriched for interferon-inducible genes. Subtraction hybridization libraries were constructed with cDNA obtained from the kidney, spleen, and liver of Chinook salmon (Oncorhynchus tshawytscha) and staghorn sculpin (Hemilepidotus spinosus) before and after injection with poly IC, a potent interferon inducer. The ``identified' genes in both cDNA libraries corresponded to previously identified genes of the fish complement system, the interferon-inducible proteins observed in mammalian cells, and the Vig-1 gene, identified in fish cells after infection with fish rhabdoviruses. Received June 19, 2001; accepted July 13, 2001     

Changes in elemental composition of fertilized and unfertilized northern pike (Esox lucius) eggs incubated in buffer with and without dimethyl sulfoxide: An X-ray microanalysis study

Fertilized and unfertilized eggs from the northern pike (Esox lucius) were incubated 2 hr in buffer with 0 and 10% (v/v) dimethyl sulfoxide and then quickly frozen in the wells of aluminum blocks submerged in liquid nitrogen. Control eggs and ovarian fluid were similarly frozen immediately after collection. The frozen eggs were sectioned, freeze dried, mounted on stubs, and carbon coated. X-ray microanalysis was used to determine changes in element levels and dimethyl sulfoxide (Me₂SO) penetration in the zona radiata, cytoplasm, cortical alveoli, and egg yolk. Unfertilized eggs incubated without Me₂SO showed decreased levels of Na, Cl, and K in the zona radiata; fertilized eggs, incubated without Me₂SO showed decreased levels of Na, P, and Cl in the zona radiata and increased levels of K in the cytoplasm; unfertilized eggs, incubated with 10% Me₂SO showed decreased Na and Cl in the zona radiata, decreased K in the cytoplasm and increased K in the cortical alveoli; fertilized eggs incubated in buffer with 10% Me₂SO showed decreased levels of Na, P, Cl, and K (zona radiata), P, Cl, and K (cytoplasm), Na (yolk), and increased Cl in the yolk (all P<.01). Me₂SO (v/v) levels reached 1.5-3.1% in the zona radiata, 0-3.2% in cytoplasm, 2.3-8.7% in cortical alveoli, and 0-1.6% in the yolk. Unfertilized eggs showed more Me₂SO penetration than fertilized eggs.     

Hydrogen peroxide treatment in Atlantic salmon induces stress and detoxification response in a daily manner

Daily variation in the absorption, metabolism and excretion of toxic substances will ultimately determine the actual concentration to which the cells and tissues are exposed. In aquaculture, Atlantic salmon (Salmo salar) can be frequently exposed to hydrogen peroxide (H₂O₂) to treat topical skin and gill infections, particularly in relation to parasitic infections (e.g. sea lice Lepeophtheirus salmonis and amoebic gill disease caused by Neoparamoeba perurans). It is well accepted that the time of administration influences pharmacodynamics and pharmacokinetics of drugs which in turn affects their efficacy and toxicity. Consequently, a better understanding of drug side effects as a function of time of day exposure would help to improve treatment efficacy and fish welfare. To this end, salmon were exposed to H₂O₂ (1500 mg/L) for 20 min at six different times of the day during a 24-h cycle and we investigated the time-dependent effects of exposure on physiological stress (glucose, lactate and cortisol) and antioxidant enzyme expression (gpx1, cat, Mn-sod and hsp70) in liver and gills. In addition, at each sampling point, 8 control fish were also sampled. Our results revealed that the time of administration of H₂O₂ caused significant differences in the induction of both physiological and oxidative stress responses. Glucose and lactate were higher in the treated fish during daytime whereas cortisol levels appeared to be systematically increased (>1000 ng/mL) after H₂O₂ treatment irrespective of exposure time, although differences with control levels were higher during the day. In liver, gene expression of antioxidant enzymes displayed daily rhythmicity in both treated and control groups and showed higher mRNA expression levels in salmon treated with H₂O₂ at ZT6 (6 h after lights onset). In gills, rhythmic expression was only found for gpx1 in the control fish and for hsp70 and Mn-sod in the treated groups. However, in the treated salmon, higher gene expression levels of all the investigated enzymes were also observed at ZT6-10. Clock gene expression showed rhythmicity only in the liver in accordance with the daily rhythm of enzyme expression observed in this tissue. Altogether, this study provides first evidence of chronotoxicity in Atlantic salmon treated with H₂O₂ and suggests increased sublethal toxic effect during the first half of the day. These results have direct relevance to the salmon and broader aquaculture industry by optimising the timing of treatment administration, opening the door to chronotherapy to treat fish diseases.     

The steady-state relationship between sodium and chloride transmembrane electrochemical potential differences inNecturus gallbladder

Summary Intracellular C1, K and Na activities (a _Cl ⁱ ,a _k ⁱ anda _Na ⁱ ) and transmucosal membrane potential (E _m) in epithelial cells ofNecturus gallbladder were measured at different external Na concentrations ([Na]_o), with liquid ion-exchanger and conventional microelectrodes. Bladders were mounted in a divided chamber at 23°C between identical HCO₃-free Ringer solutions containing 5mm K. The pH was 7.2. Tris was substituted for Na. Measurements were made under steady-state conditions as determined by the constancy of the transepithelial potential difference. Both,a _Cl ⁱ anda _Na ⁱ increased in a saturable fashion with [Na]_o.E _m did not change significantly. Average values (±sem) under normal conditions ([Na]_o=100mm) fora _Cl ⁱ ,a _Na ⁱ andE _m were 16.8±0.8mm (n=9), 9.7±0.6mm (n=10) and –52.6±0.6 mV (n=26), respectively. In Na-free mediaa _Cl ⁱ declined to its equilibrium value.a _K ⁱ (96±2mm;n=7) did not change when [Na]_o was varied between 100 and 10mm but decreased to 80±3mm (n=4) in Na-free media.Transmembrane electrochemical potential differences, , for Cl and Na were calculated at four different [Na]_o levels. A highly significant linear relation between and was found, indicating that Cl and Na transport are energetically linked. The results support the view that the energy necessary for intracellular Cl accumulation is derived from the simultaneous dissipation of the chemical potential gradient of Na across the apical membrane and that the coupled entry mechanism is electroneutral.     

Effects of plant species on phosphorus availability in a range of grassland soils

Vegetative conversion from grass to forest may influence soil nutrient dynamics and availability. A short-term (40 weeks) glasshouse experiment was carried out to investigate the impacts of ryegrass (Lolium perenne) and radiata pine (Pinus radiata) on soil phosphorus (P) availability in 15 grassland soils collected across New Zealand using ³³P isotopic exchange kinetics (IEK) and chemical extraction methods. Results from this study showed that radiata pine took up more P (4.5–33.5 mg P pot^–1) than ryegrass (1.1–15.6 mg pot^–1) from the soil except in the Temuka soil in which the level of available P (e.g., E _1min P_i, bicarbonate extractable P_i) was very high. Radiata pine tended to be better able to access different forms of soil P, compared with ryegrass. There were no significant differences in the level of water soluble P (Cp, intensity factor) between soils under ryegrass and radiata pine, but the levels of Cp were generally lower compared with original soils due to plant uptake. The growth of both ryegrass and radiata pine resulted in the redistribution of soil P from the slowly exchangeable P_i pool (E _{> 10m} P_i, reduced by 31.8% on the average) to the rapidly exchangeable P_i (E _1min-1d P_i, E _1d-10m P_i) pools in most soils. The values of R/r ₁ (the capacity factor) were also generally greater in most soils under radiata pine compared with ryegrass. Specific P mineralisation rates were significantly greater for soils under radiata pine (8.4–21.9%) compared with ryegrass (0.5–10.8%), indicating that the growth of radiata pine enhanced mineralisation of soil organic P. This may partly be ascribed to greater root phosphatase activity for radiata pine than for ryegrass. Plant species × soil type interactions for most soil variables measured indicate that the impacts of plant species on soil P dynamics was strongly influenced by soil properties.     

Growth and energy budget of F2'all-fish' growth hormone gene transgenic common carp

The growth and energy budget for F₂‘all‐fish’ growth hormone gene transgenic common carp Cyprinus carpio of two body sizes were investigated at 29·2° C for 21 days. Specific growth rate, feed intake, feed efficiency, digestibility coefficients of dry matter and protein, gross energy intake (I_E), and the proportion of I_E utilized for heat production (H_E) were significantly higher in the transgenics than in the controls. The proportion of I_E directed to waste products [faecal energy (F_E) and excretory energy loss (Z_E+U_E) where Z_E is through the gills and U_E through the kidney], and the proportion of metabolizable energy (M_E) for recovered energy (R_E) were significantly lower in the transgenics than in the controls. The average energy budget equation of transgenic fish was as follows: 100 I_E= 19·3 F_E+ 6·0 (Z_E+U_E) + 45·2 H_E+ 29·5 R_E or 100 M_E= 60·5 H_E+ 39·5 R_E. The average energy budget equation of the controls was: 100 I_E= 25·2 F_E+ 7·4 (Z_E+U_E) + 35·5 H_E+ 31·9 R_E or 100 M_E= 52·7 H_E+ 47·3 R_E. These findings indicate that the high growth rate of ‘all‐fish’ transgenic common carp relative to their non‐transgenic counterparts was due to their increased feed intake, reduced lose of waste productions and improved feed efficiency. The benefit of the increased energy intake by transgenic fish, however, was diminished by their increased metabolism.     

Effects of temperature and altitude on ventilation and gas exchange in chukars (Alectoris chukar)

Summary The effects of ambient temperature (T _a) on ventilation and gas exchange in chukar partridges (Alectoris chukar) were determined after acclimation to low and high altitute (LA and HA; 340 and 3,800 m, respectively).At both LA and HA, oxygen consumption ( ) increased with decreasingT _a atT _a from 20 to –20°C. AtT _a of 35 to 40°C, increased above thermoneutral values at HA but remained constant and minimal at LA. Water loss rates increased rapidly atT _a>30°C at both altitudes as birds began to pant. Ventilation rates (f) during panting were 5-to 23-fold greater than the minimalf at thermoneutralT _a.Increased atT _a below thermoneutrality was supported by increased minute volume (V i) at both altitudes. The change inV i was primarily a function of changing tidal volume (V t), althoughf increased slightly asT _a declined. Oxygen extraction ( ) remained fairly constant atT _a below 20°C at both altitudes. BothV t and were considerably lower when birds were panting than at lowerT _a.Chukars showed few obvious ventilatory adaptations to HA. The 35% change in between 340 and 3,800 m was accommodated by a corresponding change inV i (btps), most of which was accomplished by increasedf at HA, along with a slight increase in .Abbreviations and symbols HA high altitude - LA low altitude - rate of evaporative water loss - oxygen extraction efficiency - f respiratory frequency - V t tidal volume - V i minute volume - BMR basal metabolic rate - MHP metabolic heat production     

Comparative oxygen affinity of fish and mammalian myoglobins

Summary Myoglobins from rat, coho salmon (Oncorhynchus kisutch), buffalo sculpin (Enophrys bison) hearts, and yellowfin tuna (Thunnus albacares) red skeletal muscle were partially purified and their O₂ binding affinities determined. Commercially prepared sperm whale myoglobin was employed as an internal standard. Tested at 20°C, myoglobins from salmon and sculpin bound O₂ with lower affinity than myoglobins from the rat or sperm whale. Oxygen binding studies at 12°C and 37°C suggest that this difference is adaptive, permitting myoglobins from cold-adapted fish to function at physiologically relevant temperatures. Taken together, purification and O₂ binding data obtained in this study reveal a previously unrecognized diversity of myoglobin structure and function.     

Characterization of a glucose 3-dehydrogenase from the cultivated mushroom (Agaricus bisporus )

An extracellular enzyme with glucose dehydrogenase activity was purified from liquid cultures of the basidiomycete Agaricus bisporus after growth with d-cellobiose or d-glucose as carbon source. The molecular mass was measured as 57 kDa by gel filtration and 55 kDa by sodiumdodecyl sulphate/polyacrylamide gel electrophoresis, while the isoelectric point was at pH 3.6. By analysis of ¹H-NMR spectra in D₂O, the product of d-glucose oxidation was identified as 3-ketoglucose. The substrates oxidized included d-cellobiose, l-arabinose, d-xylose and sucrose, but the specificity parameter (k _cat/K _m) was highest for d-glucose. Two electron acceptors were identified, namely 2,6-dichloroindophenol and p-benzoquinone, but reduction of dioxygen, ferricyanide or cytochrome c was not detectable. The selective C-3 oxidation of d-glucose is well-characterized for Agrobacterium and Flavobacterium, but this is the first report for a fungus. Received: 19 June 1998 / Received revision: 15 September 1998 / Accepted: 17 September 1998     

Sex differences in circulatory oxygen transport parameters of sockeye salmon (Oncorhynchus nerka) on the spawning ground

Upon reaching sexual maturity, several species of male salmonids possess a relative ventricular mass (rM_V) that may be up to 90% larger than females. This can increase maximum cardiac stroke volume and power output, which may be beneficial to increasing the oxygen transport capacity of male salmonids during the spawning period. It may be further hypothesized, therefore, that other variables within the circulatory oxygen transport cascade, such as blood oxygen-carrying capacity and heart rate, are similarly enhanced in reproductively mature male salmonids. To test this idea, the present study measured a range of circulatory oxygen transport variables in wild male and female sockeye salmon (Oncorhynchus nerka) during their spawning period, following a 150 km migration from the ocean. The rM_V of male fish was 13% greater than females. Conversely, the haemoglobin concentration ([Hb]) of female fish was 19% higher than males, indicative of a greater blood oxygen-carrying capacity (138 vs. 116 ml O₂ l⁻¹, respectively). Surgically implanted physiological data loggers revealed a similar range in heart rate for both sexes on the spawning ground (20–80 beats min⁻¹ at 10°C), with a tendency for male fish to spend a greater percentage of time (64%) than females (49%) at heart rates above 50 beats min⁻¹. Male fish on average consumed significantly more oxygen than females during a 13-h respirometry period. However, routine oxygen consumption rates ranged between 1.5 and 8.5 mg min⁻¹ kg⁻¹ for both sexes, which implies that males did not inherently possess markedly higher routine aerobic energy demands, and suggests that the higher [Hb] of female fish may compensate for the smaller rM_V. These findings reject the hypothesis that all aspects of the circulatory oxygen transport cascade are inherently superior in male sockeye salmon. Instead, it is suggested that any differences in between sexually mature male and female sockeye salmon can likely be attributed to activity levels.     

On the infiltration of Golgi bodies from the follicular epithelium to the egg

Summary 1. In a well advanced oocyte of the tortoise the egg membranes besides the theca and the single-layered epithelium consist of a zona pellucida often differentiated into zona striata and a homogeneous layer; underlying these two layers is a layer of cortical fibrillae or fibrillar layer, Next to this layer, is the limiting membrane of the egg which is not present in all stages and generally disappears in a well developed oocyte. In certain animals either the homogeneous layer or fibrillar layer is absent. 2. In certain animals,Golgi bodies seem to be extruded into the follicle cells from the theca cells. 3. At a particular stage of development the follicle cells become very active and produce a large number of smallGolgi bodies. TheseGolgi granules filter through canalicular passages of the zona radiata into either the homogeneous layer and from thence into the fibrillar layer or where a homogeneous layer is not present directly to the fibrillar layer. Where a fibrillar layer is not present they are transferred directly to the limiting membrane and from thence to the egg. 4. In certain cases e. g. in Fowl, Calotes and Uromastix, fairly large lumps ofGolgi bodies are extruded from the follicle cells through the zona pellucida into the egg. Here the fine canilicular passages do not seem to form a vehicle for the passage of these comparatively larger bodies. 5. The fine canalicular passages in the zona radiata ofTestudo graeca andKachuga smithii and the fibrillar prolongation of the cytoplasm which we have called the fibrillar layer are marked features of the egg membranes at certain stages of development of the egg. During the period when infiltration ofGolgi bodies through these passages takes place slides prepared by silver nitrate and osmic methods show black beaded chains ofGolgi granules in various stages of descent. 6. It is claimed that the extrusion and infiltration ofGolgi bodies from the follicular epithelium to the egg are established phenomena at least in the Vertebrates.     

Activation of brain steroidogenesis and neurogenesis during the gonadal differentiation in protandrous black porgy,Acanthopagrus schlegelii

The early brain development, at the time of gonadal differentiation was investigated using a protandrous teleost, black porgy. This natural model of monosex juvenile fish avoids the potential complexity of sexual dimorphism. Brain neurogenesis was evaluated by histological analyses of the diencephalon, at the time of testicular differentiation (in fish between 90 and 150 days after hatching). Increases in the number of both Nissl‐stained total brain cells, and Pcna‐immunostained proliferative brain cells were observed in specific area of the diencephalon, such as ventromedialis thalami and posterior preoptic area, revealing brain cell proliferation. qPCR analyses showed significantly higher expression of the radial glial cell marker blbp and neuron marker bdnf. Strong immunohistochemical staining of Blbp and extended cellular projections were observed. A peak expression of aromatase (cyp19a1b), as well as an increase in estradiol (E₂) content were also detected in the early brain. These data demonstrate that during gonadal differentiation, the early brain exhibits increased E₂ synthesis, cell proliferation, and neurogenesis. To investigate the role of E₂ in early brain, undifferentiated fish were treated with E₂ or aromatase inhibitor (AI). E₂ treatment upregulated brain cyp19a1b and blbp expression, and enhanced brain cell proliferation. Conversely, AI reduced brain cell proliferation. Castration experiment did not influence the brain gene expression patterns and the brain cell number. Our data clearly support E₂ biosynthesis in the early brain, and that brain E₂ induces neurogenesis. These peak activity patterns in the early brain occur at the time of gonad differentiation but are independent of the gonads. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 76: 121–136, 2016     

Nitrogen regulation of gibberellin biosynthesis in Gibberella fujikuroi

Summary In Gibberella fujikuroi, ammonium (NH₄ ⁺) interfered with the production of gibberellic acid (GA₃). Optimal production occurred at 19 mm (NH₄)₂SO₄ and the synthesis of GA₃ was reduced threefold in a medium with 38 mm (NH₄)₂SO₄. Using a resting cell system with mycelia previously grown on two concentrations (19 mm and 38 mm) of (NH₄)₂SO₄, it was found that NH₄ ⁺ depressed synthesis of the gibberellin-synthesizing enzymes. Furthermore, addition of NH₄ ⁺ to a producing system shut off gibberellin formation, indicating that the negative effect of NH₄ ⁺ ions is also due to inhibition of one or more enzymes in the gibberellin biosynthesis pathway. The onset of gibberellin biosynthesis in media with high (38 mm) and low (19 mm) concentrations of (NH₄)₂SO₄ was studied by addition of cycloheximide to batch cultures of various ages. Offprint requests to: B. Brückner     

Choline Modulates Cardiac Membrane Repolarization by Activating an M3 Muscarinic Receptor and its Coupled K+ Channel

Choline is a necessary substrate of the lipid membrane and for acetylcholine synthesis. Accumulating evidence indicates that besides being a structural component, choline is also a functional modulator of the membrane. It has been shown to be a muscarinic acetylcholine receptor (mAChR) agonist and can induce a novel K⁺ current in cardiac cells. However, the potential role of choline in modulating cardiac functions remained unstudied despite that mAChRs are known to be important in regulating heart functions. With microelectrode techniques, we found that choline produced concentration-dependent (0.1∼10 mm) decreases in sinus rhythm and action potential duration in isolated guinea pig atria. The effects were reversed by 2 nm 4DAMP (an M₃-selective antagonist). Whole-cell patch-clamp recordings in dispersed myocytes from guinea pig and canine atria revealed that choline is able to induce a K⁺ current with delayed rectifying properties. The choline-induced current was suppressed by low concentrations of 4DAMP (2∼10 nm). Antagonists toward other subtypes (M₁, M₂ or M₄) all failed to alter the current. The affinity of choline (K _d ) at mAChRs derived from displacement binding of [³H]-NMS in the homogenates from dog atria was 0.9 mm, consistent with the concentration needed for the current induction and for the HR and APD modulation. Our data indicate that choline modulates the cellular electrical properties of the hearts, likely by activating a K⁺ current via stimulation of M₃ receptors. Received: 1 December 1998/Revised: 12 February 1999     

Production of trehalose synthase from a basidiomycete, Grifola frondosa, in Escherichia coli

The genomic DNA and cDNA for a gene encoding a novel trehalose synthase (TSase) catalyzing trehalose synthesis from α-d-glucose 1-phosphate and d-glucose were cloned from a basidiomycete, Grifola frondosa. Nucleotide sequencing showed that the 732-amino-acid TSase-encoding region was separated by eight introns. Consistent with the novelty of TSase, there were no homologous proteins registered in the databases. Recombinant TSase with a histidine tag at the NH₂-terminal end, produced in Escherichia coli, showed enzyme activity similar to that purified from the original G. frondosa strain. Incubation of α-d-glucose 1-phosphate and d-glucose in the presence of recombinant TSase generated trehalose, in agreement with the enzymatic property of TSase that the equilibrium lay far in the direction of trehalose synthesis. Received: 12 January 1998 / Received revision: 20 February 1998 / Accepted: 20 March 1998     

Effects of surgically implanted acoustic transmitters >2% of body mass on the swimming performance, survival and growth of juvenile sockeye and Chinook salmon

The influence of surgical implantation of an acoustic transmitter on the swimming performance, growth and survival of juvenile sockeye salmon Oncorhynchus nerka and Chinook salmon Oncorhynchus tshawytscha was examined. The transmitter had a mass of 0·7 g in air while sockeye salmon had a mass of 7·0–16·0 g and Chinook salmon had a mass of 6·7–23·1 g (a transmitter burden of 4·5–10·3% for sockeye salmon and 3·1–10·7% for Chinook salmon). Mean critical swimming speeds (U_crit) for Chinook salmon ranged from 47·5 to 51·2 cm s^?1 [4·34–4·69 body lengths (fork length, L_F) s^?1] and did not differ among tagged, untagged and sham‐tagged groups. Tagged sockeye salmon, however, did have lower U_crit than control or sham fish. The mean U_crit for tagged sockeye salmon was 46·1 cm s^?1 (4·1 L_F s^?1), which was c. 5% less than the mean U_crit for control and sham fish (both groups were 48·6 cm s^?1 or 4·3 L_F s^?1). A laboratory evaluation determined that there was no difference in L_F or mass among treatments (control, sham or tag) either at the start or at the end of the test period, suggesting that implantation did not negatively influence the growth of either species. None of the sockeye salmon held under laboratory conditions died from the influence of surgical implantation of transmitters. In contrast, this study found that the 21 day survival differed between tagged and control groups of Chinook salmon, although this result may have been confounded by the poor health of Chinook salmon treatment groups.