49 research outputs found
Genotype-specific responses in Atlantic salmon (Salmo salar) subject to dietary fish oil replacement by vegetable oil: a liver transcriptomic analysis
<p>Abstract</p> <p>Background</p> <p>Expansion of aquaculture is seriously limited by reductions in fish oil (FO) supply for aquafeeds. Terrestrial alternatives such as vegetable oils (VO) have been investigated and recently a strategy combining genetic selection with changes in diet formulations has been proposed to meet growing demands for aquaculture products. This study investigates the influence of genotype on transcriptomic responses to sustainable feeds in Atlantic salmon.</p> <p>Results</p> <p>A microarray analysis was performed to investigate the liver transcriptome of two family groups selected according to their estimated breeding values (EBVs) for flesh lipid content, 'Lean' or 'Fat', fed diets containing either FO or a VO blend. Diet principally affected metabolism genes, mainly of lipid and carbohydrate, followed by immune response genes. Genotype had a much lower impact on metabolism-related genes and affected mostly signalling pathways. Replacement of dietary FO by VO caused an up-regulation of long-chain polyunsaturated fatty acid biosynthesis, but there was a clear genotype effect as fatty acyl elongase (elovl2) was only up-regulated and desaturases (Δ5 fad and Δ6 fad) showed a higher magnitude of response in Lean fish, which was reflected in liver fatty acid composition. Fatty acid synthase (FAS) was also up-regulated by VO and the effect was independent of genotype. Genetic background of the fish clearly affected regulation of lipid metabolism, as PPARα and PPARβ were down-regulated by the VO diet only in Lean fish, while in Fat salmon SREBP-1 expression was up-regulated by VO. In addition, all three genes had a lower expression in the Lean family group than in the Fat, when fed VO. Differences in muscle adiposity between family groups may have been caused by higher levels of hepatic fatty acid and glycerophospholipid synthesis in the Fat fish, as indicated by the expression of FAS, 1-acyl-sn-glycerol-3-phosphate acyltransferase and lipid phosphate phosphohydrolase 2.</p> <p>Conclusions</p> <p>This study has identified metabolic pathways and key regulators that may respond differently to alternative plant-based feeds depending on genotype. Further studies are required but data suggest that it will be possible to identify families better adapted to alternative diet formulations that might be appropriate for future genetic selection programmes.</p
Intracellular Phospholipase A1 and Acyltransferase, Which Are Involved in Caenorhabditis elegans Stem Cell Divisions, Determine the sn-1 Fatty Acyl Chain of Phosphatidylinositol
Phosphatidylinositol (PI) is unique in the abundance of stearic acid at the sn-1 position. This fatty acid is thought to be incorporated through fatty acid remodeling. Here, we identified a phospholipase and acyltransferases involved in the fatty acid remodeling at the sn-1 position of PI and provide a link between the sn-1 fatty acid of PI and asymmetric cell division
Self-oscillation
Physicists are very familiar with forced and parametric resonance, but
usually not with self-oscillation, a property of certain dynamical systems that
gives rise to a great variety of vibrations, both useful and destructive. In a
self-oscillator, the driving force is controlled by the oscillation itself so
that it acts in phase with the velocity, causing a negative damping that feeds
energy into the vibration: no external rate needs to be adjusted to the
resonant frequency. The famous collapse of the Tacoma Narrows bridge in 1940,
often attributed by introductory physics texts to forced resonance, was
actually a self-oscillation, as was the swaying of the London Millennium
Footbridge in 2000. Clocks are self-oscillators, as are bowed and wind musical
instruments. The heart is a "relaxation oscillator," i.e., a non-sinusoidal
self-oscillator whose period is determined by sudden, nonlinear switching at
thresholds. We review the general criterion that determines whether a linear
system can self-oscillate. We then describe the limiting cycles of the simplest
nonlinear self-oscillators, as well as the ability of two or more coupled
self-oscillators to become spontaneously synchronized ("entrained"). We
characterize the operation of motors as self-oscillation and prove a theorem
about their limit efficiency, of which Carnot's theorem for heat engines
appears as a special case. We briefly discuss how self-oscillation applies to
servomechanisms, Cepheid variable stars, lasers, and the macroeconomic business
cycle, among other applications. Our emphasis throughout is on the energetics
of self-oscillation, often neglected by the literature on nonlinear dynamical
systems.Comment: 68 pages, 33 figures. v4: Typos fixed and other minor adjustments. To
appear in Physics Report
Genetic counselling in multiple sclerosis: risks to sibs and children of affected individuals.
Genetic factors are recognized as having important roles in both the overall etiology and the familial aggregation of multiple sclerosis (MS), leading to increased requests for genetic counselling. This paper is designed to provide familial risk data in a practical format for use during genetic counselling for MS. Depending on the amount of genetic sharing among family members, the relative risk of MS compared with that for the general population can range from 1 (adopted sibs and children of the MS proband, with whom they share no genetic material) to 190 (monozygotic co-twins of MS patients, with whom they share 100% of their genetic material). When counselling full sibs of MS patients, risks can be better calculated if information is available on the age of MS onset in the patient and whether or not one parent has MS
Genetic counselling in multiple sclerosis: risks to sibs and children of affected individuals.
Genetic factors are recognized as having important roles in both the overall etiology and the familial aggregation of multiple sclerosis (MS), leading to increased requests for genetic counselling. This paper is designed to provide familial risk data in a practical format for use during genetic counselling for MS. Depending on the amount of genetic sharing among family members, the relative risk of MS compared with that for the general population can range from 1 (adopted sibs and children of the MS proband, with whom they share no genetic material) to 190 (monozygotic co-twins of MS patients, with whom they share 100% of their genetic material). When counselling full sibs of MS patients, risks can be better calculated if information is available on the age of MS onset in the patient and whether or not one parent has MS