RESUMO
The aim of the present experiment was to measure the protease activities in ice-stored and super-chilled Atlantic salmon (Salmo salar) fillets, and the effect on texture. Pre-rigour fillets of Atlantic salmon were either super-chilled to a core temperature of -1.5°C or directly chilled on ice prior to 144h of ice storage. A significantly higher calpain activity was detected in the super-chilled fillets at 6h post-treatment compared to the ice-stored fillets and followed by a significant decrease below its initial level, while the calpastatin activity was significantly lower for the super-chilled fillets at all time points. The cathepsin B+L and B activities increased significantly with time post-treatment; however, no significant differences were observed at any time points between the two treatments. For the ice stored fillets, the cathepsin L activity decreased significantly from 6 to 24h post-treatment and thereafter increased significantly to 144h post-treatment. There was also a significantly lower cathepsin L activity in the super-chilled fillets at 0h post-treatment. No significant difference in breaking force was detected; however, a significant difference in maximum compression (Fmax) was detected at 24h post-treatment with lower Fmax in the super-chilled fillets. This experiment showed that super-chilling had a significant effect on the protease activities and the ATP degradation in salmon fillets. The observed difference in Fmax may be a result of these observed differences, and may indicate a softening of the super-chilled salmon muscle at 24h post-treatment.
Assuntos
Proteínas de Ligação ao Cálcio/química , Calpaína/química , Salmo salar/genética , Alimentos Marinhos/análise , Animais , Manipulação de Alimentos , Conservação de Alimentos , Gelo , TemperaturaRESUMO
If osmotic stress and reduced seawater tolerance are predisposing factors for infectious pancreatic necrosis (IPN) outbreaks in farmed Atlantic salmon, increased survival by enhancing access to energy would be expected. The aim of the present study was, therefore, to increase energy access in 1-year old Atlantic salmon after sea transfer by increasing the level of dietary fat, by exchanging some of the dietary oil with more easily oxidized medium chain triacylglycerols, or by dietary supplementation of potentially energy enhancing additives such as clofibrate and tetradecylthioacetic acid (TTA). A natural outbreak of IPN occurred 8 weeks after sea transfer, and a significant dietary effect explaining 76% of the variation in mortality was observed. Relative percentage survival for the fish fed TTA in sea water was 70% when compared with the unsupplemented control, reducing mortality from 7.8 to 2.3%. Muscle fat content and plasma chloride were related to IPN mortality, suggesting that reduced hypoosmoregulatory capacity might be a predisposing factor to the onset of an IPN outbreak. Based on the observation of a threefold increase in white muscle mitochondrial fatty acid oxidizing activity by TTA, it is suggested that TTA has resulted in a re-allocation of dietary fatty acids from storage to energy producing oxidation.
Assuntos
Infecções por Birnaviridae/veterinária , Surtos de Doenças/veterinária , Doenças dos Peixes/epidemiologia , Doenças dos Peixes/metabolismo , Vírus da Necrose Pancreática Infecciosa , Salmo salar/metabolismo , Tecido Adiposo , Ração Animal , Fenômenos Fisiológicos da Nutrição Animal , Animais , Infecções por Birnaviridae/metabolismo , Infecções por Birnaviridae/mortalidade , Infecções por Birnaviridae/prevenção & controle , Composição Corporal , Cloretos/sangue , Clofibrato/farmacologia , Dieta/veterinária , Suplementos Nutricionais , Ácidos Graxos/farmacologia , Água Doce , Mitocôndrias/metabolismo , Músculo Esquelético , Oxirredução , Água do Mar , Sulfetos/farmacologiaRESUMO
The transmission of the yeast 2 micrometers DNA plasmid has been examined in heterokaryons formed between a haploid donor cell containing the plasmid and a haploid recipient cell lacking the plasmid. Strains lacking the plasmid were mated to donor strains and cytoductants, haploid exconjugants arising from heterokaryons, were selected. The cytoductants bearing the genotype of the recipient cells were then tested for the presence of 2 micrometers DNA. The frequency with which the recipient received plasmid copies varied between 0 and 46%. This frequency depended on the recipient strain but was not highly dependent on whether or not the donor strain carried a kar1 mutation. Exceptional cytoductants, which had acquired a chromosome from the mating partner, were examined and found to have a much greater probability of acquiring plasmid DNA than cytoductants in general. This correlation supports the contention that plasmid copies are associated with the nucleus. In one mating the donor strain contained nearly equal amounts of two physically distinct plasmid types. Of the cytoductants bearing the recipient genotype which had acquired the plasmid during mating, most contained only one of the two plasmid types present in the donor. Analysis of this result using a Poisson distribution indicates that the average number of plasmid copies transmitted between nuclei of a heterokaryon is 0.2.