Moderate Heat Challenge Increased Yolk Steroid Hormones and Shaped Offspring Growth and Behavior in Chickens

Background

Environmental challenges might affect the maternal organism and indirectly affect the later ontogeny of the progeny. We investigated the cross-generation impact of a moderate heat challenge in chickens. We hypothesized that a warm temperature–within the thermotolerance range- would affect the hormonal environment provided to embryos by mothers, and in turn, affect the morphology and behavioral phenotype of offspring.

Methodology/Principal Findings

Laying hens were raised under a standard thermal condition at 21°C (controls) or 30°C (experimental) for 5 consecutive weeks. A significant increase was observed in the internal temperature of hens exposed to the warm treatment; however plasma corticosterone levels remained unaffected. The laying rate was not affected, but experimental hens laid lighter eggs than the controls during the treatment. As expected, the maternal thermal environment affected yolk hormone contents. Eggs laid by the experimental hens showed significantly higher concentrations of yolk progesterone, testosterone, and estradiol. All chicks were raised under standard thermal conditions. The quality of hatchlings, growth, feeding behavior and emotional reactivity of chicks were analyzed. Offspring of experimental hens (C30 chicks) were lighter but obtained better morphological quality scores at hatching than the controls (C21 chicks). C30 chicks expressed lesser distress calls when exposed to a novel food. Unlike C21 chicks, C30 chicks expressed no preference for energetic food.

Conclusion/Significance

Our findings suggest that moderate heat challenge triggers maternal effects and modulate the developmental trajectory of offspring in a way that may be adaptive. This suggests that the impact of heat challenges on captive or wild populations might have a cross-generation effect.     

Conserving the small milkwort, <Emphasis Type="Italic">Comesperma polygaloides</Emphasis>, a vulnerable subshrub in a fragmented landscape

The conservation of remnant grassland vegetation on the Victorian volcanic plain (VVP) is crucial for the persistence of local biodiversity. Recent habitat loss has restricted the grassland to only a small percentage of its former range. Along with grassland habitats, species that occur on the VVP are in decline and many are legally protected. Comesperma polygaloides is a grassland species of the VVP that also occurs outside of the region in woodland habitats. We use 12 neutral microsatellite loci and two chloroplast regions to understand genotypic patterns of C. polygaloides in southeastern Australia. We found separate genetic clusters but they do not follow geographic boundaries. There are fewer alleles (2.96) and effective alleles (2.01) than expected from 12 microsatellite markers compared to other species. Even with the low number of alleles per locus there was a moderate level of genetic diversity detected (I = 0.69; H_o = 0.43; H_e = 0.40). Populations of the VVP could not be differentiated from populations elsewhere using neutral markers or chloroplast analyses. The genetic structure discovered was not consistent with the level of fragmentation observed. There may be several reasons for the observed lack of genetic structure: the species is more common than perceived, plants are long-lived and can reproduce clonally, and the bioregion is relatively young, geologically. Results indicate that restoration projects and long-term viability of C. polygaloides will be improved by composite seed sourcing, alleviating the risk of insufficient genetic diversity posed by an over-emphasis on local provenancing.     

Conformational sampling with implicit solvent models: application to the PHF6 peptide in tau protein

Implicit solvent models approximate the effects of solvent through a potential of mean force and therefore make solvated simulations computationally efficient. Yet despite their computational efficiency, the inherent approximations made by implicit solvent models can sometimes lead to inaccurate results. To test the accuracy of a number of popular implicit solvent models, we determined whether implicit solvent simulations can reproduce the set of potential energy minima obtained from explicit solvent simulations. For these studies, we focus on a six-residue amino-acid sequence, referred to as the paired helical filament 6 (PHF6), which may play an important role in the formation of intracellular aggregates in patients with Alzheimer's disease. Several implicit solvent models form the basis of this work--two based on the generalized Born formalism, and one based on a Gaussian solvent-exclusion model. All three implicit solvent models generate minima that are in good agreement with minima obtained from simulations with explicit solvent. Moreover, free-energy profiles generated with each implicit solvent model agree with free-energy profiles obtained with explicit solvent. For the Gaussian solvent-exclusion model, we demonstrate that a straightforward ranking of the relative stability of each minimum suggests that the most stable structure is extended, a result in excellent agreement with the free-energy profiles. Overall, our data demonstrate that for some peptides like PHF6, implicit solvent can accurately reproduce the set of local energy minimum arising from quenched dynamics simulations with explicit solvent. More importantly, all solvent models predict that PHF6 forms extended beta-structures in solution, a finding consistent with the notion that PHF6 initiates neurofibrillary tangle formation in patients with Alzheimer's disease.     

Oligodendrocyte ablation affects the coordinated interaction between granule and Purkinje neurons during cerebellum development

Oligodendrocytes (OLs) are the glial cells of the central nervous system (CNS) classically known to be devoted to the formation of myelin sheaths around most axons of the vertebrate brain. We have addressed the role of these cells during cerebellar development, by ablating OLs in vivo. Previous analyses had indicated that OL ablation during the first six postnatal days results into a striking cerebellar phenotype, whose major features are a strong reduction of granule neurons and aberrant Purkinje cells development. These two cell types are highly interconnected during cerebellar development through the production of molecules that help their proliferation, differentiation and maintenance. In this article, we present data showing that OL ablation has major effects on the physiology of Purkinje (PC) and granule cells (GC). In particular, OL ablation results into a reduction of sonic hedgehog (Shh), Brain Derived Neurotrophic Factor (BDNF), and Reelin (Rln) expression. These results indicate that absence of OLs profoundly alters the normal cerebellar developmental program.     

Internal and External Cues of Meal Cessation: The French Paradox Redux?

Objective: Our objective was to investigate whether people who use internal cues of satiation when eating a meal are likely to weigh less than people who instead rely on external cues. In addition to exploring the role that internal and external cues play in meal cessation, this study raises an overlooked explanation of the French paradox. Research Methods and Procedures: A demographically‐matched student sample of 133 Parisians and 145 Chicagoans completed a brief survey on meal cessation that asked the extent to which they agreed with statements associated with internal cessation cues and statements with external cessation cues. Their answers to these were compared across BMI levels and across countries. Results: Normal‐weight people indicated that they were more likely to be influenced by internal cues of meal cessation (p = 0.043), while overweight people indicated that they were more influenced by external cues (p = 0.005). Similarly, while the French were influenced by internal cues of meal cessation (p < 0.001), Americans were more influenced by external cues (p < 0.001). Discussion: This research revisits Schachter's externality hypothesis and suggests that one's over‐reliance on external cues may prove useful in offering a partial explanation of why BMI might vary across people and potentially across cultures. Relying on internal cues for meal cessation, rather than on external cues, may improve eating patterns over the long term.     

Wood addition in the hatchery and river environments affects post‐release performance of overwintering brown trout

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