Biology

1. The evolution of strategies of resource acquisition and allocation is often considered to be closely dependent on the degree of environmental variability. Within this framework, female insects that experience stochastic fluctuations in the availability of their egg-laying sites in time or space can be expected to be fully synovigenic (i.e. they start maturing eggs after a delay once reaching adulthood), which allows them to tailor their reproductive investment to variations in the resource. Proovigenic females (that have most of their eggs already mature at the onset of their adult life, which corresponds to a capital breeding strategy), on the contrary, should have an advantage when the availability of the egg-laying sites is predictable. There is, however, a dearth of empirical studies testing these predictions.

Insects comprise relevant biological models for investigating nutrient acquisition and allocation processes in the context of life-history ecology and evolution. However, empirical investigations are still partly limited by the lack of availability of simple methods for simultaneously estimating the four major energetic components (i.e. lipids, free sugars, glycogen and proteins) in the same individual. In the present work, we validate a fast, reproducible and cheap method for overcoming this problem that uses different solvents successively. First, proteins are solubilized in a phosphate-lysis buffer and then quantified according to the classical Bradford assay procedure. In a second step, a chloroform-methanol mixture is added to the aqueous phase, which allows assay of the total lipid fraction, as well as the free sugars and glycogen in the same insect homogenate. In addition, a micro-separation procedure is adapted to partition the total lipids into neutral (mainly stored lipids) and polar (mainly structural lipids) components. Although these assays are conducted sequentially in the same individual, the sensitivity of our method remains high: the estimated amount of each energetic compartment does not differ from that obtained with former, partial methods. Our method should thus largely improve our knowledge about nutrient acquisition and allocation among insects not only in laboratory-reared individuals, but also in animals caught in the wild. Descriptions and recommendations are given at each step of the protocol to adapt the procedure to various insect species. Finally, to prevent misinterpretation of data generated in accordance with this protocol, the limits of our method are discussed in the light of life-history studies. To assess nutrient contents of individuals, most ecological studies rely on the colourimetric methods first proposed by van Handel. These assays were initially developed to quantify both glycogen and free sugars in one individual (van Handel, 1985a) and lipids in another individual . More recently, these methods have been modified to simultaneously estimate, in the same individual, the three main categories

Background: Although identified in several bird species, the biological role of the avian homolog of mammalian uncoupling proteins (avUCP) remains extensively debated. In the present study, the functional properties of isolated mitochondria were examined in physiological or pharmacological situations that induce large changes in avUCP expression in duckling skeletal muscle.

The trisomy of human chromosome 21 (Hsa21), which causes Down syndrome (DS), is the most common viable human aneuploidy. In contrast to trisomy, the complete monosomy (M21) of Hsa21 is lethal, and only partial monosomy or mosaic monosomy of Hsa21 is seen. Both conditions lead to variable physiological abnormalities with constant intellectual disability, locomotor deficits, and altered muscle tone. To search for dosage-sensitive genes involved in DS and M21 phenotypes, we created two new mouse models: the Ts3Yah carrying a tandem duplication and the Ms3Yah carrying a deletion of the Hspa13-App interval syntenic with 21q11.2-q21.3. Here we report that the trisomy and the monosomy of this region alter locomotion, muscle strength, mass, and energetic balance. The expression profiling of skeletal muscles revealed global changes in the regulation of genes implicated in energetic metabolism, mitochondrial activity, and biogenesis. These genes are downregulated in Ts3Yah mice and upregulated in Ms3Yah mice. The shift in skeletal muscle metabolism correlates with a change in mitochondrial proliferation without an alteration in the respiratory function. However, the reactive oxygen species (ROS) production from mitochondrial complex I decreased in Ms3Yah mice, while the membrane permeability of Ts3Yah mitochondria slightly increased. Thus, we demonstrated how the Hspa13-App interval controls metabolic and mitochondrial phenotypes in muscles certainly as a consequence of change in dose of Gabpa, Nrip1, and Atp5j. Our results indicate that the copy PLOS Genetics | and the "Centre Europeen de Recherche en Biomedecine", the "Fondation Jerome Lejeune", and the European commission (AnEUploidy project LSHG-CT-2006-037627 to YH, MD and SEA). The number variation in the Hspa13-App region has a peripheral impact on locomotor activity by altering muscle function.