Body mass and clutch size may modulate prolactin and corticosterone levels in eiders

Altered body condition, increased incubation costs, and egg loss are important proximate factors modulating bird parental behavior, since they inform the adult about its remaining chances of survival or about the expected current reproductive success. Hormonal changes should reflect internal or external stimuli, since corticosterone levels (inducing nest abandonment) are known to increase while body condition deteriorates, and prolactin levels (stimulating incubation) decrease following egg predation. However, in a capital incubator that based its investment on available body reserves and naturally lost about half of its body mass during incubation, corticosterone should be maintained at a low threshold to avoid protein mobilization for energy supply. This study focused on the regulation of corticosterone and prolactin release in such birds during incubation, when facing egg manipulation (control, reduced, or increased) or a stressful event. Blood samples were taken before and after clutch manipulation and at hatching. Corticosterone levels were determined before and after 30 min of captivity. Female eiders exhibited a high hypothalamic-pituitary-adrenal sensitivity, plasma concentration of corticosterone being increased by four- to fivefold following 30 min of captivity. The adrenocortical response was not modified by body mass loss but was higher in birds for which clutch size was increased. In the same way, females did not show different prolactin levels among the experimental groups. However, when incubation started, prolactin levels were correlated to body mass, suggesting that nest attendance is programmed in relation to the female initial body condition. Moreover, due to an artifactual impact of bird manipulation, increased baseline corticosterone was associated with a prolactin decrease in the control group. These data suggest that, in eiders, body mass and clutch size modification can modulate prolactin and corticosterone levels, which cross-regulate each other in order to finely control incubation behavior.     

Dissociation of inositol-requiring enzyme (IRE1α)-mediated c-Jun N-terminal kinase activation from hepatic insulin resistance in conditional X-box-binding protein-1 (XBP1) knock-out mice

Hepatic insulin resistance has been attributed to both increased endoplasmic reticulum (ER) stress and accumulation of intracellular lipids, specifically diacylglycerol (DAG). The ER stress response protein, X-box-binding protein-1 (XBP1), was recently shown to regulate hepatic lipogenesis, suggesting that hepatic insulin resistance in models of ER stress may result from defective lipid storage, as opposed to ER-specific stress signals. Studies were designed to dissociate liver lipid accumulation and activation of ER stress signaling pathways, which would allow us to delineate the individual contributions of ER stress and hepatic lipid content to the pathogenesis of hepatic insulin resistance. Conditional XBP1 knock-out (XBP1Δ) and control mice were fed fructose chow for 1 week. Determinants of whole-body energy balance, weight, and composition were determined. Hepatic lipids including triglyceride, DAGs, and ceramide were measured, alongside markers of ER stress. Whole-body and tissue-specific insulin sensitivity were determined by hyperinsulinemic-euglycemic clamp studies. Hepatic ER stress signaling was increased in fructose chow-fed XBP1Δ mice as reflected by increased phosphorylated eIF2α, HSPA5 mRNA, and a 2-fold increase in hepatic JNK activity. Despite JNK activation, XBP1Δ displayed increased hepatic insulin sensitivity during hyperinsulinemic-euglycemic clamp studies, which was associated with increased insulin-stimulated IRS2 tyrosine phosphorylation, reduced hepatic DAG content, and reduced PKCε activity. These studies demonstrate that ER stress and IRE1α-mediated JNK activation can be disassociated from hepatic insulin resistance and support the hypothesis that hepatic insulin resistance in models of ER stress may be secondary to ER stress modulation of hepatic lipogenesis.     

The structure of the extracellular domain of the jumping translocation breakpoint protein reveals a variation of the midkine fold

Jumping Translocation Breakpoint (JTB) is an orphan receptor that is conserved from nematodes to humans and whose gene expression in humans is strikingly upregulated in diverse types of cancers. Translocations occur frequently at the hJTB genomic locus, leading to multiple copies of a truncated JTB gene, which potentially encodes a soluble secreted ectodomain. In addition, JTB and its orthologs likely represent a unique and ancient protein family since homologs could not be identified by direct sequence comparison. In the present study, we have determined the NMR solution structure of the N-terminal ectodomain of human JTB, showing that its fold architecture is a new variant of a three-β-strand antiparallel β-meander. The JTB structure has a distant relationship to the midkine/pleiotrophin fold, particularly in the conservation of distinctive disulfide bridge patterns. The structure of this newly characterized small cysteine-rich domain suggests potential involvement of JTB in interactions with proteins or extracellular matrix and may help to uncover the elusive biological functions of this protein.     

New insights into tau-microtubules interaction revealed by isothermal titration calorimetry

Microtubule dynamic instability is tightly regulated by coordinated action of stabilizing and destabilizing microtubule associated proteins. Among the stabilizing proteins, tau plays a pivotal role in both physiological and pathological processes. Nevertheless, the detailed mechanism of tau-tubulin interaction is still subject to controversy. In this report, we studied for the first time tau binding to tubulin by a direct thermodynamic method in the absence of any tubulin polymerization cofactors that could influence this process. Isothermal titration calorimetry enabled us to evidence two types of tau-tubulin binding modes: one corresponding to a high affinity binding site with a tau:tubulin stoichiometry of 0.2 and the other one to a low affinity binding site with a stoichiometry of 0.8. The same stoichiometries were obtained at all temperatures tested (10-37°C), indicating that the mechanism of interaction does not depend on the type of tubulin polymer triggered upon tau binding. These findings allowed us to get new insights into the topology of tau on microtubules.     

Coenzyme based synthesis of silver nanocrystals

In this work we have carried out systematic studies to identify the critical role of a coenzyme (β-NADPH) to synthesize silver nanoparticle. Interestingly, both roles of reducing and stabilizing agents are played by β-NADPH. Nanoparticles obtained by this route exhibit a good crystallinity, a narrow size distribution and excellent stability in aqueous solution. The most advantageous points of this single-step environmentally friendly approach are that it takes place at nearly room temperature (20°C), overcomes many limitations encountered in other biological methods (such as the restricted concentration of AgNO(3), maintenance and manipulation of microorganisms, preparing extracts and contamination from residual reactants), bypasses the use of surfactants or capping agents and does not necessitate pH adjustment. The nano-Ag were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), dynamic light scattering (DLS), zeta potential, UV-vis, and energy-dispersive X-ray spectroscopy (EDX). DLS, TEM and XRD measurements showed the formation of nano-Ag with an average diameter of 20.77±0.67nm. XRD studies confirmed the nanocrystalline nature of the silver particles. Zeta potential measurements revealed that the particles are surrounded with negatively charged groups (-41±5mV) making them stable in an aqueous medium. The EDX spectrum of the silver nanoparticles confirmed the presence of elemental silver signal in high percentage. In addition to the easy and ecofriendly method of synthesis, β-NADPH can be regenerated by enzymatic means through glucose 6-phosphate dehydrogenase, potentially making the synthesis more cost effective.     

Cryopreserved Plasmodium vivax and cord blood reticulocytes can be used for invasion and short term culture

The establishment of a Plasmodium vivaxin vitro culture system is critical for the development of new vaccine, drugs and diagnostic tests. Although short-term cultures have been successfully set up, their reproducibility in laboratories without direct access to P. vivax-infected patients has been limited by the need for fresh parasite isolates. We explored the possibility of using parasite isolates and reticulocytes, both cryopreserved, to perform invasion and initiate short-term culture. Invasion results obtained with both cryopreserved isolates and reticulocytes were similar to those obtained with fresh samples. This method should be easily replicated in laboratories outside endemic areas and will substantially contribute to the development of a continuous P. vivax culture. In addition, this model could be used for testing vaccine candidates as well as for studying invasion-specific molecular mechanisms.     

Phenotypic divergence between seasnake (Emydocephalus annulatus) populations from adjacent bays of the New Caledonian Lagoon

Populations of widespread species often differ in phenotypic traits, although rarely in such a dramatic fashion as revealed by research on turtle‐headed seasnakes (Emydocephalus annulatus). These snakes are highly philopatric, with mark–recapture studies showing that the interchange of individuals rarely occurs even between two adjacent bays (separated by < 1.2 km) in Noumea, New Caledonia. Data on > 500 field‐captured snakes from these two bays reveal significant differences between these two locations in snake morphology (mean body length, relative tail length, head shape), colour, ecology (body condition, growth rate, incidence of algal fouling), behaviour (antipredator tactics), and locomotor performance. For some traits, the disparity was very marked (e.g. mean swimming speeds differed by > 30%). The causal bases for these phenotypic divergences may involve founder effects, local adaptation, and phenotypic plasticity. The spatial divergence in phenotypic traits offers a cautionary tale both for researchers (sampling of only a few populations may fail to provide a valid overview of the morphology, performance, and behaviour of a species) and managers (loss of local populations may eliminate distinctive genetic variation). © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ??, ??–??.     

Ultrasound evidence of early fetal growth restriction after maternal malaria infection

Background

Intermittent preventive treatment (IPT), the main strategy to prevent malaria and reduce anaemia and low birthweight, focuses on the second half of pregnancy. However, intrauterine growth restriction may occur earlier in pregnancy. The aim of this study was to measure the effects of malaria in the first half of pregnancy by comparing the fetal biparietal diameter (BPD) of infected and uninfected women whose pregnancies had been accurately dated by crown rump length (CRL) before 14 weeks of gestation.

Methodology/Principal Findings

In 3,779 women living on the Thai-Myanmar border who delivered a normal singleton live born baby between 2001–10 and who had gestational age estimated by CRL measurement <14 weeks, the observed and expected BPD z-scores (<24 weeks) in pregnancies that were (n = 336) and were not (n = 3,443) complicated by malaria between the two scans were compared. The mean (standard deviation) fetal BPD z-scores in women with Plasmodium (P) falciparum and/or P.vivax malaria infections were significantly lower than in non-infected pregnancies; −0.57 (1.13) versus −0.10 (1.17), p<0.001. Even a single or an asymptomatic malaria episode resulted in a significantly lower z-score. Fetal female sex (p<0.001) and low body mass index (p = 0.01) were also independently associated with a smaller BPD in multivariate analysis.

Conclusions/Significance

Despite early treatment in all positive women, one or more (a)symptomatic P.falciparum or P.vivax malaria infections in the first half of pregnancy result in a smaller than expected mid-trimester fetal head diameter. Strategies to prevent malaria in pregnancy should include early pregnancy.