Conflict outcome in male green swordtail fish dyads (Xiphophorus helleri): Interaction of body size, prior dominance/subordination experience and prior residency

The relative contribution of asymmetries in prior experience, size, and prior residency to the determination of dyadic dominance between unacquainted individuals was examined using pairs of green swordtail fish, Xiphophorus helleri. Four types of encounters were staged between an intruder and a smaller resident: (1) both had experienced prior victory; (2) both had experienced prior defeat; (3) the intruder had experienced prior victory and the resident prior defeat; and (4) the intruder had experienced prior defeat and the resident prior victory. In a fifth condition in which two intruders met, one was a prior subordinate and the other a prior dominant smaller in size than its opponent. In all these encounters, the superiority in lateral surface of one fish varied between 0 to 30% over that of its opponent. Results showed that (1) when size differences between contestants were within the range of 0-10% and there was an asymmetry in prior social experience, conflicts were essentially resolved according to prior experience with prior winners systematically defeating prior losers; (2) prior residency of 3 hours was an advantage only when both opponents had experienced prior defeat before meeting and when size asymmetries were small (e.g. <20%). It was not an advantage between prior winners or between a prior winner and a prior loser; (3) when large size asymmetries existed (e.g. 20-30%), size uniquely determined dominance outcome and nullified other advantages or disadvantages due to prior social experience and prior residency; and (4) at intermediate levels of size asymmetries (e.g. 10-20%), size partially cancelled any advantage due to a prior victory, and gradually beacme the most important factor in accounting for victories

Outcome of dyadic conflict in male green swordtail fish, Xiphophorus helleri: effects of body size and prior dominance

The relative contribution of prior experience and of size asymmetries to the determination of dyadic dominance between unfamiliar individuals was examined using pairs of green swordtail fish, Xiphophorus helleri. Three experiments were conducted to assess the extent to which superiority in size could override potential handicaps resulting from prior experience. These results indicated that prior experience accounted for dyadic dominance when the size advantage of a previously subordinate over a previously dominant opponent was less than 25 mm2. However, as the lateral surface of the subordinate fish increased, neither previous experience nor size differences clearly accounted for the outcome of dyadic conflict. Even when the size advantage of subordinate opponents was in the 126-150 mm2 range, size differences did not adequately explain the outcome. In conflicts between large previously subordinate and smaller dominant fish, there was evidence for an inverse linear relation between the effects of size and the likelihood of establishing dyadic dominance. In general, males with prior experience as subordinates had to be at least 40% larger than a previously dominant fish to win a significant proportion of conflicts. These results indicate that prior agonistic experience and body size effects can be additive when at the advantage of one opponent. These factors can also cancel each other out when in opposition, at least when size differences are not extreme. The results also confirm the main effect of both factors as well as their interaction in the determination of conflict outcomes for X. helleri

Diversity and evolution of bodyguard manipulation.

International audienc

Pre-Clinical Evaluation of a Novel Nanoemulsion-Based Hepatitis B Mucosal Vaccine

Hepatitis B virus infection remains an important global health concern despite the availability of safe and effective prophylactic vaccines. Limitations to these vaccines include requirement for refrigeration and three immunizations thereby restricting use in the developing world. A new nasal hepatitis B vaccine composed of recombinant hepatitis B surface antigen (HBsAg) in a novel nanoemulsion (NE) adjuvant (HBsAg-NE) could be effective with fewer administrations.Physical characterization indicated that HBsAg-NE consists of uniform lipid droplets (349+/-17 nm) associated with HBsAg through electrostatic and hydrophobic interactions. Immunogenicity of HBsAg-NE vaccine was evaluated in mice, rats and guinea pigs. Animals immunized intranasally developed robust and sustained systemic IgG, mucosal IgA and strong antigen-specific cellular immune responses. Serum IgG reached > or = 10(6) titers and was comparable to intramuscular vaccination with alum-adjuvanted vaccine (HBsAg-Alu). Normalization showed that HBsAg-NE vaccination correlates with a protective immunity equivalent or greater than 1000 IU/ml. Th1 polarized immune response was indicated by IFN-gamma and TNF-alpha cytokine production and elevated levels of IgG(2) subclass of HBsAg-specific antibodies. The vaccine retains full immunogenicity for a year at 4 degrees C, 6 months at 25 degrees C and 6 weeks at 40 degrees C. Comprehensive pre-clinical toxicology evaluation demonstrated that HBsAg-NE vaccine is safe and well tolerated in multiple animal models.Our results suggest that needle-free nasal immunization with HBsAg-NE could be a safe and effective hepatitis B vaccine, or provide an alternative booster administration for the parenteral hepatitis B vaccines. This vaccine induces a Th1 associated cellular immunity and also may provide therapeutic benefit to patients with chronic hepatitis B infection who lack cellular immune responses to adequately control viral replication. Long-term stability of this vaccine formulation at elevated temperatures suggests a direct advantage in the field, since potential excursions from cold chain maintenance could be tolerated without a loss in therapeutic efficacy

Biomass offsets little or none of permafrost carbon release from soils, streams, and wildfire : an expert assessment

As the permafrost region warms, its large organic carbon pool will be increasingly vulnerable to decomposition, combustion, and hydrologic export. Models predict that some portion of this release will be offset by increased production of Arctic and boreal biomass; however, the lack of robust estimates of net carbon balance increases the risk of further overshooting international emissions targets. Precise empirical or model-based assessments of the critical factors driving carbon balance are unlikely in the near future, so to address this gap, we present estimates from 98 permafrost-region experts of the response of biomass, wildfire, and hydrologic carbon flux to climate change. Results suggest that contrary to model projections, total permafrost-region biomass could decrease due to water stress and disturbance, factors that are not adequately incorporated in current models. Assessments indicate that end-of-the-century organic carbon release from Arctic rivers and collapsing coastlines could increase by 75% while carbon loss via burning could increase four-fold. Experts identified water balance, shifts in vegetation community, and permafrost degradation as the key sources of uncertainty in predicting future system response. In combination with previous findings, results suggest the permafrost region will become a carbon source to the atmosphere by 2100 regardless of warming scenario but that 65%-85% of permafrost carbon release can still be avoided if human emissions are actively reduced.Peer reviewe

Mendelian Randomization Analysis Identifies Blood Tyrosine Levels as a Biomarker of Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a complex disease associated with premature mortality. Its diagnosis is challenging, and the identification of biomarkers causally influenced by NAFLD may be clinically useful. We aimed at identifying blood metabolites causally impacted by NAFLD using two-sample Mendelian randomization (MR) with validation in a population-based biobank. Our instrument for genetically predicted NAFLD included all independent genetic variants from a recent genome-wide association study. The outcomes included 123 blood metabolites from 24,925 individuals. After correction for multiple testing, a positive effect of NAFLD on plasma tyrosine levels but not on other metabolites was identified. This association was consistent across MR methods and was robust to outliers and pleiotropy. In observational analyses performed in the Estonian Biobank (10,809 individuals including 359 patients with NAFLD), after multivariable adjustment, tyrosine levels were positively associated with the presence of NAFLD (odds ratio per 1 SD increment = 1.23 [95% confidence interval = 1.12–1.36], p = 2.19 × 10−5). In a small proof-of-concept study on bariatric surgery patients, blood tyrosine levels were higher in patients with NAFLD than without. This study revealed a potentially causal effect of NAFLD on blood tyrosine levels, suggesting it may represent a new biomarker of NAFLD