DDT induced ethological changes in estuarine fish

Synopsis Experiments were carried out to study the feeding rates of the predator fish Therapon jarbua (Forsk) on mullet juveniles, before and after treatment with DDT. Mullet juveniles treated with a subacute concentration, were refused by the control predators, whereas predators treated with a subacute concentration consumed more mullet juveniles. In the present study crescent perch T. jarbua were exposed to subacute and acute concentrations of DDT, and their behaviour was compared with that of the control predators. There were changes in oriented behaviour and co-ordinated movements, and in feeding, aggression and comfort behaviour of the fish. Inflammation in the gills, and caudal fin serration, were noticed in treated fishes. The findings presented here throw light on fundamental pathways by which pollutants interact with the behaviour of fishes.     

Resource segregation among iliophagous fish in Lake St. Lucia,Zululand

Synopsis Sarotherodon mossambicus, Chanos chanos and 11 species of Mugilidae occur in Lake St. Lucia, Zululand. All are iliophagous and potential competitors. This investigation shows that although their diets overlap, competition is reduced by different feeding mechanisms which apparently result in the available food items being consumed in differing quantities. The diet of C. chanos consists chiefly of microfauna, that of Mugilidae microflora associated with sand grains and that of S. mossambicus, microflora associated with filamentous algae and benthic floc. Potential competition is also reduced because C. chanos reach peak numbers in summer whereas Mugilidae are more abundant in winter.     

Microbiological quality of grey-mullet roe

The Greek grey-mullet roe is produced from the fully developed gonads of the female mullet (Mugil cephalus) couth in lagoons during their reproductive migration. The traditional processing method of the roe includes, air drying, salting, shape formation and covering with multiple layers of natural beeswax for preservation and distribution. Fish Roe brands have been a staple in local diet and is increasingly becoming popular in the international market. As a ready-to-eat food it’s microbial quality should be of concern for the protection of consumers health. In this study, 48 samples of fish roe, just before waxing, were collected from various local processors for microbiological examination by using selective media and incubated under aerobic and anaerobic conditions. The identification of the bacteria was carried out according to the Bergey’s manual. Microscopic examination of Gram stained cells, catalase, oxidase and biochemical tests were performed when necessary to further identify.V. parahaemolyticus, Vibrio spp., Salmonella spp., and Aeromonas hydrophila were detected in one sample (2%). Shigella spp., and Flavobacterium spp. in two samples (4%), Clotriduim perfringens (vegetative forms), E. coli, and spores of Bacillus spp., were detected in three samples (6%), Staphylococcus aureus in four samples (8%). Various Micrococcus spp., and spores of C. perfringens in 16% and 35% of the samples respectively. From the Listeria genus, only the species Listeria innocua, Listeria welshimeri, Listeria seeligeri Listeria ivanovii and Listeria grayi were recovered from 2 to 10% of the samples.Microbiological analyses revealed the presence of a small number of pathogens in grey-mullet roe samples which are in accordance with the findings of similar studies. Traditional processing of the fish roe, seems inadequate to ensure the food safety and even waxing isn’t expected to fully protect them against facultative anaerobes with salt tolerance. Therefore, additional measures should be taken during processing and marketing of fish roe to minimize potential health risks for the consumers.     

Purification and Characterization of Cytochrome P450 Reductase from Liver Microsomes of Feral Leaping Mullet (Liza saliens)

NADPH-cytochrome P450 reductase was purified to electrophoretic homogeneity from detergent-solubilized liver microsomes from the leaping mullet (Liza saliens). The purified reductase was characterized with respect to spectral, electrophoretic, and biocatalytic properties. In addition, effects of pH, ionic strength, and the substrate concentration on the NADPH-dependent cytochrome c reductase activity of the purified fish liver cytochrome P450 reductase were studied. Cytochrome P450 reductase was purified 438-fold with a yield of 17.5% with respect to the initial amount present in the fish liver microsomes. The specific activity of the enzyme was found to be 52.6 μmol cytochrome c reduced per minute per mg protein. The monomer molecular weight of the purified enzyme was calculated to be 77,000 ± 1000 when electrophoresed on polyacrylamide gels under the denaturing conditions in the presence of SDS. The absorption spectrum of fish reductase showed two peaks at 378 and 455 nm. NADPH-dependent cytochrome c reductase activity of the purified Liza saliens liver cytochrome P450 reductase was found to be maximal when pH was between 7.4 and 7.8. The apparent K_m of the purified enzyme was found to be 7.69 μM for cytochrome c when the enzyme activity was measured in 0.3 M potassium phosphate buffer, pH 7.7, at room temperature, and the enzyme was fully saturated by its substrate, cytochrome c, when the substrate concentration was at or above the 70 μM. Furthermore, the purified enzyme was biocatalytically active in reconstituting the 7-ethoxyresorufin O-deethylase activity in the reconstituted system containing purified mullet liver cytochrome P4501A1 and lipid. These results suggested that the purified fish liver cytochrome P450 reductase is similar to its mammalian counterparts with respect to spectral, electrophoretic, and biocatalytic properties. © 1997 John Wiley & Sons, Inc. J Biochem Toxicol 12: 103–113, 1998     

Cloning, sequencing, and characterization of CYP1A1 cDNA from leaping mullet (Liza Saliens) liver and implications for the potential functions of its conserved amino acids

A 2,037 bp CYP1A1 cDNA (GenBank AF072899) was cloned through screening of a lambdaZipLox cDNA library constructed from the liver of a leaping mullet (Liza saliens) fish captured from Izmir Bay on the Aegean coast of Turkey using rainbow trout CYP1A1 cDNA as a probe. This clone has a 130 bp 5'-flanking region, a 1,563 bp open reading frame (ORF) encoding a 521-amino acid protein (58,972 Da), and a 344 bp 3'-untranslated region without a poly (A) tail. Alignment of the deduced amino acids of CYP1A1 cDNAs showed 58% and 69-96% identities with human and 12 other fish species, respectively. Southern blot analysis suggested that this CYP1A1 cDNA was from a single-copy gene. Based on the comparison with CYP1A1 genes reported for fish and mammals, the leaping mullet CYP1A1 gene is probably split into 7 exons. The intron insertion sites were predicted. Alignment of the CYP1A1 cDNA encoded amino acids from 13 fish and 7 mammalian species disclosed differences in highly conserved amino acids between aquatic and land vertebrates. The possible associated secondary structure; conserved motifs and substrate-binding sites were discussed. The phylogenetic relationships of CYP1A1s among 13 fish species were analyzed by a distance method.     

Mechanism of inhibition of purified leaping mullet (Liza saliens) NADPH-cytochrome P450 reductase by toxic metals: aluminum and thallium

Aluminum and thallium may reach life-threatening levels in aquatic systems in the near future because of their extensive use in various industrial fields. It is therefore important to study the mechanism of toxicity of aluminum and thallium on fish enzymes. To this aim, the effects of aluminum and thallium on the activity of purified leaping mullet (Liza saliens) cytochrome P450 reductase, an essential component of the important cytochrome P450 system, have been studied. Results indicated that both metal ions strongly inhibited the NADPH-cytochrome P450 reductase. The IC50 values of AlCl3 and TlCl3 were estimated to be 34 microM and 3 microM, respectively. The Lineweaver-Burk plot and Dixon plot revealed that both metal ions noncompetitively inhibited the purified mullet cytochrome P450 reductase. The K(i) values of Al3+ and Tl3+ were calculated from Dixon plots as 8.9 and 5.6 microM, respectively. The inhibitory effects of Al3+ and Tl3+ on purified cytochrome P450 reductase were partially recovered by 1 mM EDTA. Additionally, tin and magnesium were shown to have no apparent effect on purified mullet cytochrome P450 reductase.     

鲻和鲮鳃丝的扫描电镜比较观察

对鲻（Mugil cephalus）和鲮（Cirrhina molitorella）的鳃丝表面结构进行了扫描电镜比较观察,结果表明,鲻鳃丝杆状部比鲮粗．鲻鳃小片高度比鲮低;两者鳃丝表面分泌孔洞口径和密度不同;鲻和鲮细胞外被不同,鲻细胞外被稀疏,鲮的则致密复杂;鳃小片细胞和鳃丝表皮细胞的表面形态存在差异,文章还描述了鳃丝表皮形态特异的细胞。     

Aldrin Epoxidation in Flathead Mullet (Mugil cephalus): Possible Involvement of CYP1A and CYP3A

The primary objective of this study was to determine specific cytochrome P450 isozyme(s) involved in the metabolism of aldrin to its toxic metabolite dieldrin in flathead mullet (Mugil cephalus) liver microsomes. To identify the cytochrome P450 isozyme responsible for the aldrin metabolism in mullet liver, the effects of mammalian‐specific cytochrome P450 inhibitors and substrates were determined in the epoxidation reaction of aldrin. CYP3A‐related inhibitors, ketoconazole, SKF‐525A, and cimetidine, inhibited the metabolism of aldrin. The contribution of CYP1A to the aldrin metabolism was shown by the inhibition of 7‐ethoxyresorufin‐O‐deethylase activity in the presence of aldrin. The results indicate that CY1A and CYP3A are the cytochrome P450s involved in aldrin epoxidase activity in mullet. In addition, the suitability of aldrin epoxidase activity for monitoring of environmental pollution was also assessed in the fish samples caught from four different locations of the West Black Sea coast of Turkey.     

The use of metabolism to evaluate the toxicity of dodecil benzen sodium sulfonate (LAS-C12) on the Mugil platanus (mullet) according to the temperature and salinity

The effects of watering exposition to different concentrations of LAS-C12 (1, 2.5 and 5 mg l⁻¹) about the Mugil platanus routine metabolism were evaluated. The metabolic rates were estimated through experiments accomplished in each of the twelve possible combinations of three temperatures (25, 20 and 15 °C) and three salinities (35, 20 and 5). The results show that the oxygen consumption increases according to the LAS-C12 concentration in all temperatures and salinities studied. At the highest concentration employed (5 mg l⁻¹), and the salinity 5 in the temperatures 25 and 20 °C, oxygen consumption increases 80% in relation to the control. In general, the pollutant effects on oxygen consumption were more pronounced at the highest temperatures and salinities 5 and 35.     

Induced CYP1A mRNA, protein and catalytic activity in the liver of feral fish, leaping mullet, Liza saliens

In this study, we examined whether levels of P4501A mRNA expression were naturally induced in feral fish, Liza saliens, and whether CYP1A protein levels and associated enzyme activity, EROD, were also increased. Induction of mRNA was measured using a nucleic acid hybridization technique. For the hybridization studies, a new 33-mer oligonucleotide probe 5'-dCTC ATC CAG CTT CCT GTC CTC GCA GTG ATC AAT-3' was designed, which corresponded to the totally conserved amino acid motif of CYP1A protein from positions 291 to 301 among the various fish species. Results of Northern blot analysis revealed that RNA isolated from the liver of mullet collected from the highly contaminated region of Izmir Bay with a dissolved and dispersed petroleum hydrocarbon content of 12.45 microg l(-1) gave a strong hybridization signal, whereas only a weak hybridization signal was detected in the liver RNA of fish caught from the reference site containing less than 1 microg l(-1) of petroleum hydrocarbons. Similarly, fish from the contaminated site had approximately 80 times more EROD activity than the feral fish captured from the reference site. Studies using polyclonal antibodies produced against purified mullet CYP1A also showed the similar trend. In conclusion, feral leaping mullet caught from contaminated water displayed induction of CYP1A at three levels of expression, namely, mRNA, apoprotein and catalytic activity.