Molecular cloning of a cDNA encoding 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase from liver of Sparus aurata: nutritional regulation of enzyme expression.
A cDNA clone encoding full-length 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (6PF-2-K/Fru-2, 6-P2ase) was isolated and sequenced from a Sparus aurata liver cDNA library. The 2527 bp nucleotide sequence of the cDNA contains a 73 bp 5'-untranslated region (5'-UTR), an open reading frame that encodes a 469 amino acid protein and 1041 bp at the 3'-UTR. The deduced amino acid sequence is the first inferred 6PF-2-K/Fru-2, 6-P2ase in fish. The kinase and bisphosphatase domains, where the residues described as crucial for the mechanism of reaction of the bifunctional enzyme are located, present a high degree of homology with other liver isoenzymes. However, within the first 30 amino acids at the N-terminal regulatory domain of the fish enzyme a low homology is found. Nutritional regulation of the 6-phosphofructo-2-kinase activity, together with immunodetectable protein and mRNA levels of 6PF-2-K/Fru-2,6-P2ase, was observed after starvation and refeeding. In contrast to results previously described for rat liver, the decrease in immunodetectable protein and kinase activity caused by starvation was associated in the teleostean fish to a decrease in mRNA levels. (+info)
Sequence and expression of a cDNA encoding the red sea bream androgen receptor.
The cDNA of the androgen receptor (AR) has been isolated from the ovary of red sea bream, Pagrus major, and sequenced. The amino acid sequence of red sea bream AR (rsAR) shows about 45% identity with that of Xenopus, rat, mouse, and human AR. It is shown that rsAR has the ability to trans-activate the responsive gene depending on the presence of androgen. (+info)
Virus susceptibility of the fish cell line SAF-1 derived from gilt-head seabream.
The recently reported SAF-1 cell line from fins of gilt-head seabream was evaluated for susceptibility to lymphocystis disease virus (LDV) and to several salmonid fish viruses, such as infectious haematopoietic necrosis virus (IHNV), viral haemorrhagic septicemia virus (VHSV) and several strains of infectious pancreatic necrosis virus (IPNV). LDV, VHSV and IHNV replicated well in the cultured fin cells as demonstrated by cell lysis and increases in viral titer. The potential use of this cell line to detect viruses from fish marine species is discussed. (+info)
Dietary chromic oxide does not affect the utilization of organic compounds but can alter the utilization of mineral salts in gilthead sea bream Sparus aurata.
This study was conducted to determine whether the level of chromic oxide supplemented to diets containing gelatinized starch as the carbohydrate source affects digestibility, body composition, growth performances, and liver enzyme activities in gilthead sea bream, Sparus aurata. Gilthead sea bream fingerlings were fed diets containing gelatinized corn starch as the carbohydrate source and several levels of chromic oxide (0, 5, 10 and 20 g/kg) for 6 wk. No effect of dietary chromium level was detected on carbon, nitrogen, or dry matter digestibility. Calcium and phosphorus digestibility were higher in fish fed the diet supplemented with 5 g/kg chromic oxide than in fish fed the other supplemented diets. Dietary chromium did not affect dry matter, carbon, nitrogen, protein, or lipid concentrations in fish. However, fish fed 5 g/kg chromic oxide generally had higher levels of calcium, phosphorus, and ash than fish fed the other Cr-containing diets. Chromium concentration was significantly higher in fish fed the diets with 0.5 and 1% chromic oxide than in fish fed the control diet. Chromium supplementation of the diets did not affect the specific growth rate, the food efficiency ratio, the protein efficiency ratio, or, protein or nitrogen retention of the fish. Blood glucose and the activity of several liver enzymes involved in carbohydrate metabolism were unaffected by dietary chromic oxide. Alanine aminotransferase was lower in the fish fed the diet with 10 g/kg of chromic oxide than in unsupplemented controls. Our results indicate that chromic oxide can be used as a neutral marker in fish nutrition studies involving organic compounds, but not mineral salts. (+info)
Molecular phylogenetic evidence for the evolution of specialization in anemonefishes.
Anemonefishes (genera: Amphiprion and Premnas; family Pomacentridae) are a group of 28 species of coral reef fishes that are found in obligate symbiosis with large tropical sea anemones. A phylogenetic hypothesis based on morphological analyses of this group suggests that the ancestral anemonefish was a generalist with similar morphology to other pomacentrids, and that it gave rise to other anemonefish species that were more specialized for living with particular species of host anemones. To test this hypothesis we constructed a molecular phylogeny for the anemonefishes by sequencing 1140 base pairs of the cytochrome b gene and 522 base pairs of the 16S rRNA gene for six species of anemonefishes (representatives of all subgenera and species complexes) and two other pomacentrid species. Three methods of phylogenetic analysis all strongly supported the conclusion that anemonefishes are a monophyletic group. The molecular phylogeny differs from the tree based on morphological data in that the two species of specialized anemonefishes (Premnas biaculeatus and Amphiprion ocellaris) were assigned to a basal position within the clade, and the extreme host generalist (Amphiprion clarkii) to a more derived position. Thus, the initial anemonefish ancestors were probably host specialists and subsequent speciation events led to a combination of generalist and specialist groups. Further phylogenetic studies of additional anemonefish species are required to substantiate this hypothesis. (+info)
Effects of GH, prolactin and cortisol on hepatic heat shock protein 70 expression in a marine teleost Sparus sarba.
Heat shock protein 70 (HSP70) expression was assessed in hepatic tissue of a marine teleost Sparus sarba after exogenous hormone administration. Using a PCR-amplified, homologous HSP70 cDNA clone, as a probe in Northern analysis, we detected a 2.3 kb transcript which was elevated after exposure to a temperature 7 degrees C above the ambient. For our studies on hormonal effects on HSP70 expression, groups of fish were administered recombinant bream GH (rbGH), ovine prolactin (oPRL) or cortisol daily over a 7-day period. Quantification of hepatic HSP70 transcript revealed that the administration of GH and PRL significantly reduced HSP70 mRNA abundance by 42% and 54% from saline-injected fish respectively. Also hepatic HSP70 levels were reduced by 76% and 64% as determined by immunoblotting after rbGH and oPRL treatment respectively. The administration of exogenous cortisol did not alter hepatic HSP70 mRNA or protein levels in S. sarba. The results obtained in this study are the first evidence for hormonal modulation of heat shock protein expression in fish. The significance of these results is discussed within the context of current knowledge on the roles of these hormones in teleostean stress response. (+info)
Sequence and expression of a cDNA encoding the red seabream androgen receptor.
The cDNA of the androgen receptor (AR) has been isolated from the ovary of red seabream, Pagrus major, and sequenced. The amino acid sequence of red seabream AR (rsAR) shows about 45% identity with those of Xenopus, rat, mouse, and human ARS. It is shown that rsAR has the ability to trans-activate the responsive gene depending on the presence of androgen. (+info)
Lunar cycles in diel prey migrations exert a stronger effect on the diving of juveniles than adult Galapagos fur seals.
In our study of the development of diving in Galapagos fur seals, we analysed changes in diving activity and body mass trends over the lunar cycle. Based on previously observed lunar cycles in colony attendance patterns, we hypothesized a greater impact of prey migrations of deep scattering layer organisms on younger fur seals. Using electronic dive recorders, we determined that seals dived less and deeper on moonlit nights than at new moon, and incurred body mass losses. These changes in foraging over the lunar cycle correlate with the suppression of the vertical migration of prey by lunar light. All effects were more pronounced in juveniles than adult females, with greater relative mass loss during full moon, which must (i) negatively affect long-term juvenile growth rates, (ii) lengthen periods of maternal dependence, and (iii) contribute to the lowest reproductive rate reported for seals. This underlines the importance of studying ontogeny in order to understand life histories, and for determining the susceptibility of animal populations to fluctuations in food availability. (+info)