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Lamarre, S. G., Ditlecadet, D., McKenzie, D. J., Bonnaud, L., & Driedzic, W. R. (2012). Mechanisms of protein degradation in mantle muscle and proposed gill remodeling in starved Sepia officinalis. Am. J. Physiol.-Regul. Integr. Comp. Physiol., 303(4), R427–R437.
Résumé: Lamarre SG, Ditlecadet D, McKenzie DJ, Bonnaud L, Driedzic WR. Mechanisms of protein degradation in mantle muscle and proposed gill remodeling in starved Sepia officinalis. Am J Physiol Regul Integr Comp Physiol 303: R427-R437, 2012. First published May 30, 2012; doi:10.1152/ajpregu.00077.2012.-Cephalopods have relatively high rates of protein synthesis compared to rates of protein degradation, along with minimal carbohydrate and lipid reserves. During food deprivation on board protein is catabolized as a metabolic fuel. The aim of the current study was to assess whether biochemical indices of protein synthesis and proteolytic mechanisms were altered in cuttlefish, Sepia officinalis, starved for 7 days. In mantle muscle, food deprivation is associated with a decrease in protein synthesis, as indicated by a decrease in the total RNA level and dephosphorylation of key signaling molecules, such as the eukaryote binding protein, 4E-BP1 (regulator of translation) and Akt. The ubiquitination-proteasome system (UPS) is activated as shown by an increase in the levels of proteasome beta-subunit mRNA, polyubiquitinated protein, and polyubiquitin mRNA. As well, cathepsin activity levels are increased, suggesting increased proteolysis through the lysosomal pathway. Together, these mechanisms could supply amino acids as metabolic fuels. In gill, the situation is quite different. It appears that during the first stages of starvation, both protein synthesis and protein degradation are enhanced in gill. This is based upon increased phosphorylation of 4E-BP1 and enhanced levels of UPS indicators, especially 20S proteasome activity and polyubiquitin mRNA. It is proposed that an increased protein turnover is related to gill remodeling perhaps to retain essential hemolymph-borne compounds.
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Valls, E., Navarro, J., Barria, C., Coll, M., Fernandez-Borras, J., & Rotllant, G. (2016). Seasonal, ontogenetic and sexual changes in lipid metabolism of the small-spotted catshark (Scyliorhinus canicula) in deep-sea free-living conditions. J. Exp. Mar. Biol. Ecol., 483, 59–63.
Résumé: Marine predators, such as elasmobranchs, exhibit variations in nutritional conditions related to both reproductive traits and food availability in the marine environment throughout the year. The main objective of this study was to examine changes in several blood physiological parameters in a demersal shark, the small-spotted catshark (Scyliorhinus canicula), in the wild in relation to season, sex and maturity stage. For this purpose, 108 individuals at different deKelopmental stages were captured and released alive in the western Mediterranean. Blood was obtained from caudal vessels and plasma lipid fractions (total cholesterol, triglycerides and phospholipids) and a ketone body (3-beta-hydroxybutyrate) were measured. During summer, plasma triglyceride and phospholipid levels were lower in adults than in juveniles (mainly in females, probably related to breeding season and laying eggs). Plasma cholesterol levels also showed higher values in summer, indicating higher physical activities during summer and revealing that lipid fractions are more related to reproduction than to nutrition. Plasma 3-beta-hydroxybutyrate variations showed a different pattern. No differences were found between sex or maturity stage during summer, although the highest values in adult and juvenile males during winter indicates higher physical activity of males. This study, uses an innovative methodology to establish a correlation between lipid fractions and ketone bodies from the blood of wild individuals and changes in sexual and nutritional status. This method was conducted without damage to the target species and provides new information on the physiology of this abundant elasmobranch in the Mediterranean Sea. (C) 2016 Elsevier B.V. All rights reserved.
Mots-Clés: behavior; Cholesterol; dogfish; Elasmobranch; elasmobranchs; fish; Ketone bodies; Phospholipids; Physiological parameter; roles; sharks; Triglycerides
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