The presence of 17α,20β-dihydroxy-4-pregnen-3-one receptor activity in the ovary of the brook trout,Salvelinus fontinalis,during terminal stages of oocyte maturation

The presence of 17,20-dihydroxy-4-pregnen-3-one (17,20-DHP) oocyte receptor activity has been demonstrated in brook troutSalvelinus fontinalis. Scatchard analyses of the cytosol fraction during various terminal stages of oocyte maturation gave a high equilibrium association constant (K_a) value of 1.394±0.669 10⁸M^–1 (n=7) and low maximum binding capacities (N_max). The association kinetics of the receptor was second order k₊₁=2.292×10⁶M^–1 sec^–1. The dissociation rate constant k_a was 1.502×10^–2 sec^–1 for the first order dissociation reaction. The K_a=1.526×10⁸M^–1, when it was determined from k₊₁/k_–1 a value close to that found from the Scatchard analysis. Competition studies showed the following binding affinities testosterone > 17-HP > 17,20-DHP > Promegestone > progesterone > estradiol > pregnenolone; cortisol showed no competitive inhibition. Cytosolic extracts when pre-equilibrated with various labelled steroids and eluted from a Sephacryl S-300 column gave multiple specific binding peaks. On sucrose density gradient centrifugation specific binding was observed at 3.05 S in cytosol containing 0.15M sodium chloride buffer. The receptor lost binding activity when incubated with various proteases, but DNase and RNase had no effect. Blood plasma without heparin at (110) dilution also bound [³H]17,20-DHP, Ka was 8.04×10⁷ M^–1.The nuclear pellet extract (750×g) gave very little specific binding activity even at high radiolabelled steroid concentrations and a linear Scatchard plot was not obtained. Nevertheless the nuclear extract, after dextran-charcoal treatment, pre-equilibrated with [³H]17,20-DHP, bound specifically to DNA cellulose, and cytosol from the same oocytes also bound to DNA cellulose under similar conditions. Although specific binding to DNA cellulose was obtained the salt concentrations at which the steroid-receptor complex elution took place was not reproducible in both nuclear extracts and cytosol samples. Also binding activity was extremely small compared to the total cytosolic binding. The nuclear extract when pre-equilibrated with high concentrations (20 nM) of the labelled steroid and then chromatographed on Sephacryl S-300 column gave a specific binding peak which was similar to that of the cytosolic preparation.The receptor levels in cytosol decreased progressively during final maturation (Stages 1–7). There is preliminary evidence for the presence of 17,20-DHP receptor activity in cytosol of landlocked Atlantic salmonSalmo salar ouananiche, and rainbow troutSalmo gairdneri. The zona radiata fraction from late stages oocyes 5, 6, and 7 in brook and rainbow trout oocytes were isolated by ultracentrifugation; from this fraction a protein was characterized which covalently bound [³H]R5020 after photoaffinity labelling. The same protein also bound [³H]17,20-DHP after solubilization in Brig 35 buffer. The SDS gel electrophoresis subunit composition of the above protein was similar to the cytosol counterpart binding [³H]17,20-DHP, although the molecular weights were different. The blood sample [³H]R5020 binding component subunit composition was different from that of the membrane extracted protein. These results demonstrate the presence of 17,20-DHP receptor activity in the cytosol and zona radiata membranes of the oocytes during final maturation.A. Maneckjee is presently NSERC postgraduate scholar at MSRL and Ph.D. candidate at Department of Biochemistry, Memorial University of Newfoundland.     

On sightings of (vagrant?) monk seals,Monachus monachus,in the Mediterranean Basin and their importance for the conservation of the species

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An evaluation of the duration of efficacy of emamectin benzoate in the control of Caligus curtus Müller infestations in Atlantic cod, Gadus morhua L

The duration of efficacy of emamectin benzoate in the control of Caligus curtus infestations in Atlantic cod, Gadus morhua L., was studied following an administration of 50 μg kg^?1 for seven consecutive days. No lice were found on medicated fish when challenged 1 week (challenge 1) or 5 weeks (challenge 2) following termination of medication, whereas the mean abundance of lice among the unmedicated fish was 17.9 and 19.3 lice per fish in challenge 1 and 2, respectively. Muscle concentrations of 19.5 ± 8.2 ng g^?1 and 3.4 ± 0.9 ng g^?1, respectively, and skin concentrations of 23.1 ± 10.8 and 4.2 ± 1.0 ng g^?1, respectively, were found 27 and 55 days following the termination of medication. Tissue concentrations and the duration of efficacy indicate a dosing regime for emamectin in cod, similar to the regime used for Atlantic salmon, Salmo salar L.     

The effects of hypoxia,in vivo,on red blood cell β-adrenoceptors in the rainbow trout,Oncorhynchus mykiss

Rainbow trout, Oncorhynchus mykiss, were exposed to 48h of environmental hypoxia (water partial pressure of oxygen = 8.0 kPa) at either 5 or 15°C. Blood was sampled during hypoxia via a dorsal aorta cannula to measure arterial blood partial pressure of oxygen and plasma catecholamine concentrations. After 48h, the number (B_max) and dissociation constant (K_d) of red blood cell surface -adrenoceptors were determined using a radioligand-displacement binding assay. At 5°C, plasma catecholamine levels were elevated at 24h whereas at 15°C, levels were elevated at 48h. At either temperature, following 48h of hypoxia, there was no change in B_max or K_d of red blood cell surface -adrenoceptors, compared to normoxic control fish. This study demonstrates that chronic exposure to moderate hypoxia does not affect the number or affinity of cell surface -adrenoceptors on trout red blood cells.     

Molecular cloning of the cDNA encoding the β subunit of thyrotropin and regulation of its gene expression by thyroid hormones in the goldfish, Carassius auratus

A cDNA encoding the subunit of thyrotropin (TSH) was isolated from a goldfish (Carassius auratus) pituitary gland cDNA library. By comparing the sequence with other teleost TSHs, a signal peptide of 19 amino acids and a mature hormone of 131 amino acids were predicted for goldfish TSH subunits. The resulting putative mature hormone of 131 amino acids had well-conserved cysteine positions and a putative N-linked glycosylation site; homology was 51–67% with TSHs from other teleosts, 38–43% with tetrapod TSHs, but only 27 and 29% with goldfish GTH-I and -II, respectively. We also examined the effects of thyroid hormones (TH) and thiourea (TU, an inhibitor of TH production) treatments on TSH and GTH subunit gene expressions in the goldfish pituitary gland. After thyroxine (T₄) treatment, circulating T₄ concentration increased and TSH mRNA level decreased. Supressing the amount of circulating T₄ and triiodothyronine (T₃) by TU treatment increased the TSH mRNA level. Moreover, T₄ replacement therapy (simultaneous treatment of both TU and T₄) caused a high level of circulating T₄ and a low level of circulating T₃, and a decrease in the TSH mRNA level. Thus, changing levels of circulating TH exert a negative feedback on the level of TSH subunit mRNA in goldfish in vivo. On the other hand, GTH subunit mRNA levels were not affected by changes in the levels of circulating TH.     

Bioaccumulation of hexachlorocyclohexane,dichlorodiphenyltrichloroethane, and estradiol-17β in catfish and carp during the pre-monsoon season in India

This investigation was performed to monitor hexachlorocyclohexane isomers (HCHs), dichlorodiphenyltrichloroethane (DDT, and its metabolites, refered to as DDTs), plasma levels of estradiol-17β (E2), and the gonadosomatic index (GSI) between sampling sites of unpolluted ponds of Gujartal, Jaunpur (control site) and the polluted rivers Gomti (Jaunpur) and Ganga (Varanasi), which affect the reproductive physiology of some edible catfish and carp during the pre-monsoon season. HCHs and DDTs were measured by gas liquid chromatography (GLC) and hormones by radioimmunoassay (RIA). The results indicated that the level of HCHs and DDTs was very high in both the catfish and the carp captured from the polluted rivers compared with the fish captured from the control site. The GSI and E2 values were lower in both groups of fish when compared to the fish from the control site. The results also indicate that catfish showed greater bioaccumulation of HCHs and DDTs than carp, above the permissible limit, as compared to the fish from the control site. In conclusion, fish from the Gomti and Ganga rivers were highly polluted when compared with fish from the control site, as was evident from high levels of tissue bioaccumulation of HCHs and DDTs and decreased levels of plasma E2, inhibiting the reproductive physiology of these species at the receptor level. The levels exceeded the maximum residue limits (MRL) as recommended by Codex, hence it is suggested that the fish should be avoided for food purposes.     

Habitat and prey selection of common minke,sei, and Bryde’s whales in mesoscale during summer in the subarctic and transition regions of the western North Pacific

This study represents the first quantitative analysis of the characteristics of the distribution areas and stomach contents of common minke whale Balaenoptera acutorostrata, sei whale B. borealis, and Bryde’s whale B. edeni in relation to oceanographic and prey environments in mid summer in the western North Pacific. Common minke whales were distributed within subarctic regions and the northernmost region of the transitional domain, coinciding with the main habitat of their preferred prey, Pacific saury Cololabis saira. Sei whales were mainly found in the northernmost part of the transition zone and showed prey preference for Japanese anchovy Engraulis japonica, which was significantly more abundant in the main distribution area of the whale than in its adjacent areas. “Hot spots” of Bryde’s whales were found in several regions of the transition zone between the subarctic boundary and the Kuroshio front. This whale species preferred Japanese anchovy as prey, for which the distribution density was significantly higher in the main distribution area of the whale than in the adjacent areas. These results indicate that the summer distributions of Pacific saury and Japanese anchovy greatly influence the distributions of these whale species, suggesting that the whales’ habitat selection is closely related to their prey selection.     

Numerical simulation of circulation in the Laizhou Bay

IntroductionAs part of the Bei Dou Fisheries Research and Managements project(1997- 2 0 0 0 ) ,the Institute of MarineResearch participated in a collaborative study with the Yellow Seas Fisheries Institute on approaches to thedevelopment of theoretical models as tools for assessing the carrying capacity of bivalve production.The In-stitute of Marine Research has in recent years engaged in relatively extensive activity on numerical modellingof coastal oceans. To demonstrate some of the po…     

What are the drivers of the occurrence of illegal fishing and conservation barriers of sturgeons in the Caspian Sea?

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How wild is the ocean? Assessing the intensity of anthropogenic marine activities in British Columbia,Canada

• 1. The intensity of marine activities in the exclusive economic zone (EEZ) of British Columbia, Canada, was quantified.
• 2. Humans use the ocean for a multitude of purposes, many of which have a direct impact on marine life and habitat. Yet such uses are seldom assessed in an integrated fashion.
• 3. Using a GIS approach, spatial information for 39 marine activities was mapped, including commercial and recreational fishing areas, transportation and infrastructure uses, and terrestrial activities along the coast of British Columbia.
• 4. A relative scale was used to rank both the impact of marine activities and the extent of stressors beyond the location of occurrence. Limited information on the latter led to the application of three ranges of buffer distances to the data (0–1 km, 0–5 km, and 0–25 km).
• 5. The most conservative estimate (?1 km buffers) indicates at least 83% of the continental shelf and slope of British Columbia is currently being used by humans. The largest buffer assumption shows 98% of the continental shelf and slope being affected by stressors from anthropogenic activities.
• 6. This analysis provides a baseline for assessing future changes in the state of British Columbia's marine environment, and could assist in identifying areas of conservation potential.

Copyright © 2007 John Wiley & Sons, Ltd.     

Studies on activity, distribution, and zymogram of protease, α-amylase, and lipase in the paddlefish Polyodon spathula

A series of biochemical determination and electrophoretic observations have been conducted to analyze the activities and characteristics of protease, α-amylase, and lipase of paddlefish Polyodon spathula. The results obtained have been compared with those of bighead carp (Aristichthys nobilis) and hybrid sturgeon (Huso dauricus ♀?×?Acipenser schrenki Brandt ♂), in order to increase available knowledge of the physiological characteristics of this sturgeon species and to gain information with regard to its nutrition. Further, a comparative study of enzymatic activity, distribution, and characterization between commercial feed-reared paddlefish (CG) and natural live food-reared (NG) paddlefish was conducted. Results showed that higher proteolytic activity was observed in the pH range 2.5-3.0 and at a pH of 7.0 for paddlefish. Levels of acid protease activity of paddlefish were similar to that of hybrid sturgeon, and significantly higher than that of bighead carp. The inhibition assay of paddlefish showed that the rate of inhibition of tosyl-phenylalanine chloromethyl ketone was approximately 2.6-fold that of tosyl-lysine chloromethyl ketone. There was no significant difference observed for acid protease activity between PG and CG groups, whereas the activity of alkaline protease, α-amylase, and lipase in the PG group were significantly lower than those in the CG group. The substrate sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis further showed that there were certain types of enzymes, especially α-amylase, with similar molecular mass in the paddlefish and hybrid sturgeon. It can be inferred that acid digestion was main mechanism for protein hydrolysis in paddlefish, as reported for other fishes with a stomach. This indicates that the paddlefish requires higher alkaline protease, α-amylase, and lipase activity to digest natural live food.     

Investigation of the Protective Effect of β-carotene in the Prevention of Lipid and Protein Oxidation in Carp Meat during Different Storage Times

ABSTRACT

This study was aimed to investigate the effects of dietary β-carotene supplement for 42 days on lipid and protein oxidation biomarkers in carp meat at different times of storage. Seventy-five fish were divided into three groups: group 1 as control group was fed with basic diet; groups 2 and 3 received 50 and 100 mg kg^?1 diet β-carotene, respectively. Based on the present study results, muscle malondialdehyde concentrations were significantly lower following β-carotene consumption at 0, 24, 72, and 96 h after harvest in group 3 compared to the control group (p < 0/05). Muscle protein carbonyl contents showed a significant decrease following β-carotene supplementation at 0, 48, and 96 h after harvest in group 3 compared to the control group. Ferric reducing antioxidant power values were significantly increased following β-carotene supplementation at 72 and 96 h after harvest in group 3 compared to the control group. The results indicated that β-carotene supplementation with a dose of 100 mg kg^?1 diet is largely effective to improve the oxidative status of carp meat by reducing lipid and protein oxidation.     

Hypothermal effects on expression of regucalcin,a calcium-binding protein,in the livers of seawater- and fresh water–acclimated milkfish,Chanos chanos

Fish Physiology and Biochemistry - Regucalcin (RGN) is a calcium-binding protein mainly expressed in the liver. It functions in regulating activities of several calcium-dependent enzymes related to...     

Toxicity of wild juvenile “komonfugu” Takifugu flavipterus in the Bay of Sanriku Coast,Tohoku Area,Northern Japan

To clarify the mechanism of tetrodotoxin (TTX) accumulation in pufferfish, we compared the toxicity of two sets of wild juvenile “komonfugu” Takifugu flavipterus. The first set was sampled from Onisawa Fishing Port (FP) located in Okirai Bay, the Pacific Coast of Sanriku, Tohoku Area, Northern Japan. The second set was collected from the Onisawa FP and reared in an outdoor laboratory tank supplied with different seawater (Yoshihama Bay). The fish were sampled regularly and on the same days. The amount of TTX (mouse unit (MU)/fish) in the fish at Onisawa FP increased until 20 days and thereafter it did not change, while the amount of TTX in the fish in the laboratory tank remained low, and the TTX concentration (MU/g fish) decreased. Next, we compared the toxicity of wild juvenile T. flavipterus collected from Okirai Bay (Onisawa FP and Okirai FP) and Yoshihama Bay (Yoshihama FP). Large differences in TTX levels were observed among the fish from the three FPs. The amounts and concentrations of TTX in the fish at Onisawa FP were higher than those in the fish from the other two FPs. These results indicate that a large variation in toxic activity exists in the juvenile T. flavipterus in the bay of the Sanriku Coast.

     

Does reintroduction stabilize the population of the critically endangered gharial (Gavialis gangeticus,Gavialidae) in Chitwan National Park,Nepal?

• 1 Despite conservation programmes (India 1975, Nepal 1978) gharial populations (Gavialis gangeticus) have declined over their entire distribution range. Information about the current status and main threats is needed to implement effective conservation measures.
• 2 This study presents a survey (2003/2004) of the largest Nepalese gharial population in the Chitwan National Park that has benefited from regular re‐introduction of young gharials since 1981.
• 3 Population size estimates fluctuate between 34 (2003) and 38 (2004). The reintroduction programme, although of limited success, has helped to maintain the gharial population.
• 4 Gharials bask preferentially in large sand banks, and these sites must be protected.
• 5 The main threats are from a dam that causes fish depletion and flushes gharials from the protected area, sand mining and grazing that destroy basking sites, fishing that causes food shortage, drift nets that kill gharial, and water pollution.
• 6 Improvement in the survival of reintroduced gharials is needed. Strict protection of preferred basking sites and prohibition of fishing in the main settling zones are the principal conservation measures while in the long term, education and participatory management by local people are also necessary. Copyright © 2010 John Wiley & Sons, Ltd.

     

Changes in the distribution of Atlantic cod (Gadus morhua) in the southern Gulf of St Lawrence — effects of environmental change or change in environmental preferences?

Density-independent redistribution in response to changing temperature conditions and density-dependent redistribution in response to changing temperature preferences are two contrasting hypotheses to explain changes in the distribution of cod populations. I tested these hypotheses using survey data on the distribution of cod during the feeding season in the southern Gulf of St Lawrence. These tests used indices of cod distribution as the dependent variable and indices of cod abundance and bottom temperature as explanatory variables. Both hypotheses were often supported in univariate tests that ignored confounding between the two explanatory variables. Tests that accounted for this confounding indicated an effect of cod abundance on distribution for ages 4–8⁺ years, and 3⁺, but provided no support for an effect of environmental conditions on distribution except for age 3. Variation in the temperature distribution of cod was consistent with an effect of abundance on interannual variation in distribution and with no effect of environment except for age 3 cod. Age 3 cod were consistently under-represented in areas of very cold bottom water but older cod were not. As predicted by bioenergetic considerations, cod tended to occupy colder water at high levels of abundance, suggesting a mechanism for density-dependent shifts in distribution. Shifts in cod distribution during the feeding season in the southern Gulf appear to be more closely linked to density-dependent changes in environmental preferences than to density-independent responses to changing environmental conditions.     

Limiting nutrients of oyster pond seawaters in the Marennes-Oléron region for Haslea ostrearia: applications to the mass production of the diatom in mesocosm experiments

Bioassays were carried out with the `blue diatom' Haslea ostrearia Simonsen, which is responsible for oyster greening during the fattening period of Crassostrea gigas Thunberg in oyster ponds. Samples of seawater were taken from two oyster ponds: one without oysters and the other with 20 oysters per m[sup2 ], maximal density allowed by the French AFNOR norm for `refinement'. The aims were to clarify the nutrient requirements of this diatom, also to elucidate the eventual influence of C. gigas at this density on the seawater fertility and to envisage the mass production of this diatom by pond fertilization. Examination of cell numeric densities at the end of bioassays allows us to conclude that silicate was the first limiting nutrient, closely followed by phosphate. Chlorophyll a concentrations led to different conclusions: phosphate was the first limiting factor, but after the seawater storage period in ponds, seawater quality evolved to a deficiency of nitrogen. Silicate addition increased cell division rate, and silicate depletion increased chl a synthesis for this species. Examination of nutrient assimilation ratios confirms that H. ostrearia requires a large amount of silicon. From these results, it was possible to prepare a N + P + Si simplified medium which has been tested in laboratory and field mesocosm conditions. In both conditions, similar results were observed: a significant increase in H. ostrearia cell concentrations and consequently an evolution up to the greening stage. Applications of this work are numerous; the principal permits us to envisage the production of this species in 25-m³ ponds, with the aim of allowing constant production of the greening phenomenon.     

Do active‐dispersing insects dominate the invertebrate fauna of rock pools in the wet–dry tropics,Kimberley, Australia?

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Does urea reabsorption occur via the glucose pathway in the kidney of the freshwater rainbow trout?

This study tested the hypothesis that the renal reabsorption of urea occurs via the glucose transport pathway in the freshwater rainbow trout (Oncorhynchus mykiss). The relationship between glucose transport and urea transport was examined by experimentally elevating the rate of renal glucose reabsorption via infusion of the fish with exogenous glucose, and by inactivating the glucose transporters via the administration of phlorizin. Under all treatments, urea was reabsorbed against a concentration gradient, with plasma levels of urea being higher than urine levels. Glucose was almost completely reabsorbed (88%) whereas urea was reabsorbed less efficiently (47%) but to a greater extent than water (22%). Glucose and urea reabsorption were both found to be correlated with Na⁺ and Cl^– reabsorption, though the latter were 20 fold and 200–300 fold higher than glucose and urea transport rates, respectively. Glucose infusions greatly increased glucose reabsorption but urea reabsorption was unaffected. Phlorizin treatment completely blocked glucose reabsorption, but urea reabsorption was again unaffected. We conclude that there is no relationship between glucose and urea handling in the trout kidney, thus disproving the hypothesis.