Acid phosphatase activity in pre- and post-spawning hake (Merluccius hubbsi)

1. The specific activity of muscle acid phosphatase (E.C. 3.1.3.1.) in pre- and post-spawning hake was investigated. 2. Specific activity values, 0.54 in pre-spawning hakes and 1.64 in post-spawning fish, have been obtained. 3. Using a histochemical test, acid phosphatase has been localized mainly in the connective tissue. The strongest reaction has been observed in post-spawning hake. 4. The increase of the lysosomal activity in the connective tissue may be related to the changes found in the muscle texture associated with spawning.     

Fish protein hydrolysis by a psychrotrophic marine bacterium isolated from the gut of hake (Merluccius hubbsi)

The aims of this study were to identify a psychrotrophic bacterium, strain CR41, producing a cold adapted protease during growth at low temperatures and to evaluate the ability of the cells to hydrolyze hake fish protein. The strain was isolated from the intestinal tract of hake collected from the San Jorge Gulf (Patagonia, Argentina) and it was identified as Pseudoalteromonas. Growth and fish protein hydrolysis were determined using an aerated simple mineral medium plus 10% fish protein concentrate. Proteolytic activity was measured at 7 and 22 degrees C during culture in the concentrate. Protease production started in the exponential growth phase and reached a maximum during stationary phase. Protease activity at 7 degrees C was lower than at 22 degrees C. After 8 h of incubation, the percentage of hydrolyzed protein was 84% at 7 degrees C and 95% at 22 degrees C. Electrophoresis detection showed that degradation of muscle hake proteins was complete at both temperatures, and in gelatin zymograms extracellular activity showed two proteolytic bands with apparent molecular masses of approximately 31.6 and 62 kDa.     

Changes in lipids and biochemical properties of actomyosin from pre- and post-spawned hake (Merluccius hubbsi Marini)

The total lipid contents of muscle, the liver somatic index and the total lipid contents of actomyosin in hakes changed with the gonadal condition of the fish. Non-polar lipids in actomyosin from pre-spawned hake were 145% higher than in actomyosin from post-spawned hake; polar lipids were 30% higher. The relative percentage of phospholipids changed from 32% in pre-spawned hake to 48% in post-spawned hake. The Mg²⁺-ATPase activity in actomyosin increased from the pre-spawned to the post-spawned conditions, and this could be related to a higher phospholipids to neutral lipids ratio in post-spawned hake. Gradual decreases in both Ca²⁺-ATPase activity and myosin: actin ratio during the gonadal development of fish were found, suggesting a partial loss of myosin functionality of the actomyosin complex.     

Sexual differences in the increase of white muscle fibres in Argentine hake, Merluccius hubbsi, from the San Matias Gulf (Argentina)

Growth dynamics of white fibres from axial muscle has been investigated in Argentine hake, Merluccius hubbsi , discriminating between sexes for the first time. The frequency distributions of fibre diameters are remarkably different in both sexes at sizes between 42 and 63·9 cm total length (T.l.). Males have a much lower proportion of newly recruited fibres (0–10 μm) than females; at 52–53·9 cm T.l., females have 4% of fibres in that category and males 0·5%. It appears that, from this size interval onwards, the increase in muscle mass is due only to the increase in diameter of individual fibres, which may exceed 300 μm. The lower recruitment rate of new fibres in males, and its relationship to lower growth rates and smaller final sizes, are discussed, and possible effects of reproductive activity are considered.     

Occurrence of N-acylethanolamine phospholipids in fish brain and spinal cord

N-Acylethanolamine phospholipids were identified in the central nervous system of the fresh water fish, pike (Esox lucius) and carp (Cyprinus carpio), at levels ranging from 0.1 to 0.9% of total phospholipid. The N-acylethanolamine phospholipids of carp brain were isolated and characterized by chemical, biochemical and spectroscopic methods. Two major species, 1,2-diacyl-sn-glycero-3-phospho(N-acyl)ethanolamines (approx. 30%) and 1-O-(1'-alkenyl)-2-acyl-sn-glycero-3-phospho(N-acyl)ethanolamines (approx. 70%) were identified. The N-acyl groups of each species consisted primarily of 16:0 (approx. 60%) but also contained 16:1, 18:0 and 18:1 (approx. 10% each) and a number of trace constituents. The N-acylethanolamine phospholipids had O-acyl and O-alkenyl group compositions similar but not identical to those of the ethanolamine phospholipids of the same tissue. N-Acylethanolamine phospholipids were present in all subcellular fractions of carp brain, except mitochondria.     

Changes in the fatty acid composition of phospholipids in tissues of farmed sea bass (Dicentrarchus labrax) during an annual cycle. Roles of environmental temperature and salinity

We quantified seasonal effects on fatty acid composition of tissue phospholipids in farmed sea bass. Major changes in percent phosphatidylethanolamine and phosphatidylcholine were observed in all tissues between February and March, and the phosphatidylcholine/phosphatidylethanolamine ratio was drastically reduced at this time. Different changes in the fatty acid composition of total phospholipids were observed in all tissues examined. Fish fed all year on the same commercial diet showed a significant correlation between water salinity and percentage of 22:6n-3 in muscle, liver and gill phospholipids, but no correlation was found between percent 22:6n-3 of phospholipids and water temperature. In each tissue, we observed annual variation in the 20:5n-3/20:4n-6 ratio in phospholipids, but maximum and minimum values occurred at different times in each organ. From these results, we conclude that salinity can play a significant role in modulating the activities of enzymes acting on lipid metabolism during their natural circannual cycles.     

Larval anisakids and other helminths in the hake, Merluccius gayi (Guichenot) from Chile

One hundred and twenty hake Merluccius gayi caught off central Chile were examined for helminth parasites. Sixty hake were kept in ice from the catch of a trawler were examined upon arrival at port, while the other 60 hake were dissected on board immediately after collection. Ninety one per cent of hake were infected with one or more species of the following helminths: trypanorhynch plerocerci of Grillotia dollfusi Carvajal, 1971; adult worms of the genus Clestobothrium; larval nematodes of the genera Anisakis and Phocanema; 86% of the total were infected with Anisakis sp. and 42.5% with Phocanema sp. Infection with larval nematodes increased with length of the fish and there was a greater incidence of infection among the females. There was a greater frequency of occurrence of the parasites in the viscera than in the musculature.     

Fatty acid composition of galactolipids and phospholipids in neoplasmatic plant tissues (cecidia) and normal leaf tissue

Insect-elicited modifications of leaf cells that produce leaf galls on higher plants are concurrent with changes at the biochemical level. The neoplasmatic alterations affect the composition and concentration of membrane phospho and galactolipids. In vitro labeling of developing leaf galls from oak [induced by cympids (Hymenoptera) on L.] with [¹⁴C]-acetate and [³H]-oleate was used to study the label distribution in monogalactosyldiacylglyceride, digalactosyldiacylglyceride, phospha-tidylglycerol and phosphatidylinositol in these tissues and in the normal host organs (leaf laminae). The incorporation of both labels was higher into the leaf galactolipids than into gall galactolipids, whereas the incorporation of oleate was slightly increased in the 2 phospholipids in cynipid galls. The degree of acyl chain unsaturation of individual endogenous phosphoglycerides (phosphatidylcholine, phosphatidyletha-nolamine. phosphatidylglycerol, diphosphatidylglycerol, phosphatidylinositol) was, in most cases, higher in the gall tissues. Differences in the endogenous fatty acid composition of plant polar lipids and the molar concentrations of labeled fatty-acid precursors in galacto- and phospholipids are discussed with regard to modifications of the leaf phenotype and cecidogenesis on Quercus palustris L.     

Amino acid composition and endocrine control of vitelline envelope proteins in European sea bass (Dicentrarchus labrax) and gilthead sea bream (Sparus aurata)

The vitelline envelopes of European sea bass and gilthead sea bream are both composed of mainly four proteins with the molecular masses of 90, 52, 48, 45 kDa and 75, 50, 48, 44 kDa, respectively. Each protein has an amino acid composition that is characterized by a high content of proline and glutamic acid and a low content of cysteine, similar to the whole vitelline envelope of both species. The amino acid composition suggests that each protein is distinct but related to the other vitelline envelope proteins. The use of homologous antisera shows that both species have vitelline envelope proteins that are induced by estradiol-17β. As males of both species synthesize these proteins after treatment with estradiol-17β, the origin is not restricted to the ovaries. Vitellogenin of both Eurpoean sea bass and gilthead sea bream has the apparent molecular mass of 170 kDa. © 1995 Wiley-Liss, Inc.     

Fatty acid composition and unsaturated of intracellular membrane phospholipids from rat liver and hepatoma 27]

The fatty acid composition of phospholipids of mitochondria and microsomes from rat liver and hepatoma 27 was investigated. Basing on the fatty acid and phospholipid composition the unsaturation of the lipid bilayer of the intracellular membranes was calculated. The unsaturation of the phospholipids of the hepatoma mitochondria and microsomes was found to be much lower than that of the corresponding rat liver membranes. The lipid bilayer of the rat liver and hepatoma plasma membranes was shown to be more saturated than that of the intracellular membranes.     

Fatty acid composition of platelet phospholipids and plasma lipids in obese Zucker rats

The purpose of this work was to see whether hyperlipaemia observed in genetically obese Zucker rats (fa/fa) was associated with differences in fatty-acid composition of plasma triacylglycerols, plasma phospholipids and of platelet phospholipids, in comparison with the control lean rats (Fa/-). Results showed that plasma triacylglycerols and phospholipids were increased in obese rats. In triacylglycerols, the amount of saturated and monounsaturated fatty acids was highly increased whereas the amount of the n-6 and n-3 polyunsaturated fatty acids was little modified. In plasma phospholipids, saturated and monounsaturated fatty acids were also increased, as were the n-3 fatty acids (except C 18:3 n-3); the n-6 fatty acids were little increased except C 20:3 n-6 which was markedly increased. These results concerning the amounts of fatty acids have their counterpart in their relative proportions of fatty acids. Data thus obtained suggest that conversion of linoleic acid (C 18:2 n-6) into arachidonic acid (C 20:4 n-6) was decreased in obese rats, particularly the delta 5 desaturation step. On the contrary, conversion of linolenic acid (C 18:3 n-3) into higher polyenes seemed increased. Thrombocytosis was not modified in the obese rat, but the volume of the platelets was increased. Platelet phospholipids exhibited the same modifications as plasma phospholipids but with different magnitude. Saturated and monounsaturated fatty acids were little augmented, n-3 fatty acids were more augmented (except C 18:3 n-3 acid which was unchanged); n-6 fatty acids were not modified except C 20:3 n-6 acid which was highly increased.(ABSTRACT TRUNCATED AT 250 WORDS)     

Fatty acid composition of phospholipids from rabbit and crayfish skeletal muscle sarcolemma and sarcoplasmic reticulum membranes]

A comparative analysis of fatty acid composition of lipid components from skeletal muscle sarcolemma and sarcoplasmic reticulum membranes of rabbits and crayfishes Astacus fluviatilis and A. leptodactylus has been made by means of gas-liquid chromatography of methyl esters of fatty acids. There are slight differences between external and internal membranes in fatty acids composition of lipids in the same animal. Considerable differences were found, however, when lipids in corresponding membranes of different species were compared. There are more unsaturated fatty acids in the crayfish than in the rabbit membranes. The most expressive differences in fatty acid composition between the two animals concern the content of linoleic acid type. Polyunsaturated acids in the crayfish are mostly of a 3 type and those in the rabbit of a 6 type. During biochemical evolution the following changes seem to take place, a decrease in the amount of unsaturated fatty acids as well as of polyunsaturated ones of a 3 type and an increase of those of the 6 type. These changes very probably reflect the transition from an aquatic to a terrestrial habitat.     

Cloning of Wap65 in sea bass (Dicentrarchus labrax) and sea bream (Sparus aurata) and expression in sea bass tissues

The complementary DNA encoding WAP65 protein was cloned from the liver of two fish species sea bass (Dicentrarchus labrax) and sea bream (Sparus aurata). Full-length cDNA sequences were obtained from reverse transcribed total RNA, followed by 5′ and 3′ rapid amplification of cDNA end (RACE) experiments. The full-length cDNA sequence of D. labrax is 1709 bp and the coding sequence is flanked by a 67 bp 5′-UTR and a 358 bp 3′-UTR. The full-length cDNA sequence of S. aurata is 1599 bp, and the coding sequence is flanked by a 48 bp 5′-UTR and a 273 bp 3′-UTR. The deduced amino acid putative primary sequences are composed of 427 and 425 amino acid residues for D. labrax and S. aurata, respectively. They display high homologies with previously described fish WAP65 and other hemopexin-like proteins from rabbit (Oryctolagus cuniculus). Expression of Wap65 has proved to be a natural physiological adaptive answer of teleost fish to warm temperature acclimation. In all fish species studied to date, Wap65 was found expressed mainly by the liver, although other tissues seem able to express Wap65 in response to a warm temperature acclimation, in a specie specific manner. Here, we investigate the tissue specific expression of Wap65 in D. labrax and S. aurata in response to a warm temperature acclimation, by RT-PCR analysis.     

Notes on the biology of the Patagonian hake, Merluccius hubbsi (Marini), the southern blue whiting, Micromesistius australis (Norman) and others in the Falkland Islands shelf area

From the examination of samples of fish caught in two commercial surveys on trawling grounds around the Falkland Islands, it is noted that Patagonian hake, Merluccius hubbsi , southern blue whiting, Micromesistius australis , and others occurred in fishable quantities especially to the east of Beauchêne Islands where fishes were larger and more numerous. However 47% of the total catch consisted of southern blue whiting which was 100% infested by a myxosporidian parasite in its musculature rendering it unsuitable for human consumption.     

Fatty acid composition of total lipids and phospholipids of membrane preparations of transport ATPases

The fatty acid composition of total lipids and phospholipids of duck salt gland Na,K-ATPase (outer plasma membrane) and of rabbit skeletal muscle Ca-ATPase (intracellular membrane) was investigated. The bulk of Na,K-ATPase fatty acids is represented by palmitic (16:0), oleic (18:1), stearic (18:0) and arachidonic (20:4) acids. The duck salt gland is characterized by rather a high content of unsaturated fatty acids, especially of arachidonic acid. The unsaturation index of total-lipid fatty acids increases during purification of these preparations in the following order: homogenate greater than microsomal fraction greater than purified enzyme. The fatty acid composition of Na,K-ATPase total lipids and phospholipids reveals certain differences. Phospholipids contain more stearic and liholeic (18:2) acids than total lipids, but the level of arachidonic acid in them is twice as low. Besides, phospholipids were found to contain polyunsaturated docosohexaenic (22:6) acid. The bulk of fatty acids of rabbit skeletal muscle Ca-ATPase total lipids and phospholipids is represented by 16:0, 18:0, 18:1 and 18:2 acids. The content of polyunsaturated fatty acids in this preparation is much lower than in duck salt gland Na,K-ATPase. The fatty acid composition of total lipids and phospholipids in rabbit skeletal muscle Ca-ATPase differ insignificantly. The differences in the fatty acid composition of membrane preparations under study is conditioned mainly by the fractional composition of their lipids.     

Fatty acid and lipid class composition in eyes and brain from teleosts and elasmobranchs

The effect of 17beta-estradiol (E(2)) on osmoregulatory performance was examined in the euryhaline killifish, Fundulus heteroclitus. Fish were injected once with 1, 2 and 5 microg g(-1) E(2) and, 6 h after injection, transferred from 1 ppt seawater (SW) to full strength SW (40 ppt) or from SW to 1 ppt SW. In another set of experiments, fish were injected four times on alternate days with 2 microg g(-1) E(2) and then, 6 h after the last injection, transferred from 1 ppt SW to SW or from SW to 1 ppt SW. Fish were sampled 18 h after transfer (i.e., 24 h post-injection), and plasma osmolality, Na(+) and Cl(-) concentration and gill K(+)-pNPPase activity (a reflection of the sodium pump) were examined. Transfer from 1 ppt SW to SW resulted in significantly increased plasma osmolality, but did not affect gill K(+)-pNPPase activity. A single dose of E(2) (1, 2 and 5 microg g(-1)) prior to transfer from 1 ppt SW to SW increased plasma osmolality and decreased gill K(+)-pNPPase activity in a dose-dependent manner. Prolonged treatment with E(2) increased plasma osmolality and decreased gill K(+)-pNPPase activity in 1 ppt SW-adapted fish. Transfer of fish thus treated from 1 ppt SW to SW increased plasma osmolality and did not alter gill K(+)-pNPPase activity. Transfer from SW to 1 ppt SW had no significant effect on plasma osmolality or gill K(+)-pNPPase activity. Only the highest single dose of E(2) (5 microg g(-1)) prior to transfer from SW to 1 ppt SW decreased gill K(+)-pNPPase activity. Prolonged treatment with 2 microg g(-1) E(2) decreased gill K(+)-pNPPase activity only following transfer from SW to 1 ppt SW. The results substantiate an inhibitory action of E(2) on hypoosmoregulatory capacity in this euryhaline teleost.     

Diet of two large sympatric teleosts, the ling (Genypterus blacodes) and hake (Merluccius australis)

Ling and hake are tertiary consumers, and as a result both may have an important structuring role in marine communities. The diets of 2064 ling and 913 hake from Chatham Rise, New Zealand, were determined from examination of stomach contents. Ling was a benthic generalist, and hake a demersal piscivore. The diet of ling was characterised by benthic crustaceans, mainly Munida gracilis and Metanephrops challengeri, and demersal fishes, mainly Macrourids and scavenged offal from fishing vessels. The diet of hake was characterised by teleost fishes, mainly macrourids and merlucciids. Multivariate analyses using distance-based linear models found the most important predictors of diet variability were depth, fish length, and vessel type (whether the sample was collected from a commercial or research vessel) for ling, and fish length and vessel type for hake. There was no interspecific predation between ling and hake, and resource competition was largely restricted to macrourid prey, although the dominant macrourid species predated by ling and hake were different. Cluster analysis of average diet of intraspecific groups of ling and hake confirmed the persistent diet separation. Although size is a central factor in determining ecological processes, similar sized ling and hake had distinctly different foraging ecology, and therefore could influence the ecosystem in different ways, and be unequally affected by ecosystem fluctuations.     

Melatonin binding sites in the brain of European sea bass (Dicentrarchus labrax)

Characteristics, day-night changes, guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS) modulation, and localization of melatonin binding sites in the brain of a marine teleost, European sea bass Dicentrarchus labrax, were studied by radioreceptor assay using 2-[(125)I]iodomelatonin as a radioligand. The specific binding to the sea bass brain membranes was rapid, stable, saturable and reversible. The radioligand binds to a single class of receptor site with the affinity (Kd) of 9.3 +/-0.6 pM and total binding capacity (Bmax) of 39.08 +/-0.86 fmol/mg protein (mean+/-SEM, n=4) at mid-light under light-dark (LD) cycles of 12:12. Day-night changes were observed neither in the Kd nor in the Bmax under LD 12:12. Treatment with GTPgammaS significantly increased the Kd and decreased the Bmax both at mid-light and mid-dark. The binding sites were highly specific for 2-phenylmelatonin, 2-iodomelatonin, melatonin, and 6-chloromelatonin. Distribution of melatonin binding sites in the sea bass brain was uneven: The Bmax was determined to be highest in mesencephalic optic tectum-tegmentum and hypothalamus, intermediate in telencephalon, cerebellum-vestibulolateral lobe and medulla oblongata-spinal cord, and lowest in olfactory bulbs with the Kd in the low picomolar range. These results indicate that melatonin released from the pineal organ and/or retina plays neuromodulatory roles in the sea bass brain via G protein-coupled melatonin receptors.