The evolution of hippocampus volume and brain size in relation to food hoarding in birds

Food‐hoarding birds frequently use spatial memory to relocate their caches, thus they may evolve a larger hippocampus in their brain than non‐hoarder species. However, previous studies testing for such interspecific relationships provided conflicting results. In addition, food hoarding may be a cognitively complex task involving elaboration of a variety of brain regions, even outside of the hippocampus. Hence, specialization to food hoarding may also result in the enlargement of the overall brain. In a phylogenetic analysis of distantly related birds, we studied the interspecific association between food hoarding and the size of different brain regions, each reflecting different resolutions. After adjusting for allometric effects, the relative volume of the hippocampus and the relative size of the entire brain were each positively related to the degree of food‐hoarding specialization, even after controlling for migration and brood parasitism. We also found some significant evidence for the relative volume of the telencephalon being associated with food hoarding, but this relationship was dependent on the approach we used. Hence, neural adaptation to food hoarding may favour the evolution of different brain structures.     

Conformational characterization of oligomeric intermediates and aggregates in β-lactoglobulin heat aggregation

In one of the first studies of isolated intermediates in protein aggregation, we have used circular dichroism and fluorescence spectroscopy to characterize metastable oligomers that are formed in the early steps of beta-lactoglobulin heat aggregation. The intermediates show typical molten globule characteristics (secondary structure content similar to the native and less tight packing of the side chains), in agreement with the belief that partly folded states play a key role in protein aggregation. The far-UV CD signal bears strong resemblance to that of a known folding intermediate. Cryo-transmission electron microscopy of the aggregates reveals spherical particles with a diameter of about 50 nm and an internal threadlike structure. Isolated oligomers as well as larger aggregates bind the dye thioflavin T, usually a signature of the amyloid superstructures found in many protein aggregates. This result suggests that the structural motif recognized by thioflavin T can be formed in small oligomers.     

Cladosporium fulvum overcomes Cf-2-mediated resistance by producing truncated AVR2 elicitor proteins

The Cf-2 gene of tomato confers resistance to strains of the biotrophic pathogenic fungus Cladosporium fulvum carrying avirulence gene Avr2. To allow dissection of the biochemical mechanism of perception of AVR2 by Cf-2, we set out to clone the Avr2 gene. Here, we report the functional cloning of Avr2 cDNA, based on the induction of a hypersensitive response (HR) by the encoded AVR2 protein in Cf2 tomato plants. Analysis of strains of C. fulvum that are virulent on Cf2 tomato lines revealed various independent frameshift mutations in the Avr2 open reading frame (ORF) and a point mutation resulting in a premature stop codon. All modifications result in the production of truncated AVR2 proteins. Interestingly, an additional modification involves the insertion of a LINE-like element, Cfl1, in the Avr2 ORF. Cfl1 is the first LINE-like element identified in C. fulvum and provides the first example of loss of avirulence of a plant pathogen caused by insertion of a retrotransposable element in an Avr gene. Rcr3 represents an additional plant protein that is specifically required for Cf-2-mediated resistance. Analysis of two different rcr3 mutant Cf2 tomato plants revealed that their ability to respond to AVR2 with a HR correlates with their degree of resistance to AVR2-producing strains of C. fulvum. These data support a role for Rcr3 in the perception of AVR2 by Cf-2.     

Synthesis and biological evaluation of disubstituted N6-cyclopentyladenine analogues: the search for a neutral antagonist with high affinity for the adenosine A1 receptor

Novel 3,8- and 8,9-disubstituted N(6)-cyclopentyladenine derivatives were synthesised in moderate overall yield from 6-chloropurine. The derivatives were made in an attempt to find a new neutral antagonist with high affinity for adenosine A(1) receptors. N(6)-Cyclopentyl-9-methyladenine (N-0840) was used as a lead compound. Binding affinities of the new analogues were determined for human adenosine A(1) and A(3) receptors. Their intrinsic activity was assessed in [35S]GTPgammaS binding experiments. Elongation of the 9-methyl of N-0840 to a 9-propyl substituent was very well tolerated. A 9-benzyl group, on the other hand, caused a decrease in adenosine A(1) receptor affinity. Next, the 8-position was examined in detail, and affinity was increased with appropriate substitution. Most derivatives were A(1)-selective and 20 of the new compounds (6-9, 15-21, 23-26, 28, 31, 33, 35, and 36) had higher adenosine A(1) receptor affinity than the reference substance, N-0840. Compound 31 (N(6)-cyclopentyl-8-(N-methylisopropylamino)-9-methyladenine, LUF 5608) had the highest adenosine A(1) receptor affinity, 7.7 nM. In the [35S]GTPgammaS binding experiments, derivatives 5, 14, 22, 23, 25, 26, 33 and 34 did not significantly change basal [35S]GTPgammaS binding, thus behaving as neutral antagonists. Moreover, four of these compounds (23, 25, 26, and 33) displayed a 4- to 10-fold increased adenosine A(1) receptor affinity (75-206 nM) compared to N-0840 (852 nM). In summary, we synthesised a range of N-0840 analogues with higher affinity for adenosine A(1) receptors. In addition, four new derivatives, LUF 5666 (23), LUF 5668 (25), LUF 5669 (26) and LUF 5674 (33), behaved as neutral antagonists when tested in [35S]GTPgammaS binding studies. Thus, these compounds have improved characteristics as neutral adenosine A(1) receptor antagonists.     

Sex-role reversal in vertebrates: behavioural and endocrinological accounts

Sex-role reversal occurs when females compete more intensely than males for access to mates. In this paper, we survey the occurrence of sex-role reversal in vertebrates: we focus on behavioural aspects of sex-role reversal and we examine possible endocrinological correlates of this phenomenon. The best documented cases among vertebrates of sex-role reversal occur in fish and birds. In nearly all sex-role reversed species or populations, females have higher potential reproductive rates than males. Some species in which females were previously thought to be the predominant competitors for mates (for instance seahorses and a dendrobatid frog), appear not to be sex-role reversed according to recent studies. The endocrinology of sex-role reversal has been studied in only a few species and therefore remains poorly understood. In birds, which probably have been studied the most in this respect, steroid hormones appear to follow the typical ancestral conditions (for instance no reversal of testosterone levels) in sex-role reversed species, whereas prolactin, a principal regulator of the onset and maintenance of incubation, departs from the usual avian pattern in that it is higher in males than in females. The study of sex-role reversed behaviour offers unique opportunities not only to test sexual selection theory, but also to enhance our understanding of the neuroendocrine mechanisms mediating behavioural sex differences.     

Acetyl substitution patterns of amylose and amylopectin populations in cowpea starch modified with acetic anhydride and vinyl acetate

To study the effect of reagent type on the distribution pattern of acetyl groups in acetylated cowpea starch, amylose and amylopectin populations were isolated from the starch granules after modification to a low degree of substitution (DS < 0.1) with acetic anhydride and vinyl acetate, respectively. Slowly reacting reagent vinyl acetate resulted in higher DS values for the amylopectin populations when compared to the rapidly reacting reagent acetic anhydride. The two reagents had similar effects on the acetylation level of amylose, suggesting that the amorphous regions of granules were easily accessible for both reagents. The acetyl substitution patterns were analyzed by enzymatic degradation followed by characterization of the obtained fragments using chromatographic and mass spectrometric techniques. The distributions of acetyl groups along the amylose and amylopectin chains were more clustered for modification with vinyl acetate as compared with modification with acetic anhydride. Between the two acetylation types, pronounced differences in the acetyl substitution patterns were observed for the large fragments obtained after -amylase digestion; only slight differences were exhibited for the small fragments obtained by exhaustive enzymatic digestion of amylose and amylopectin populations.     

Inequalities in Alcohol-Related Mortality in 17 European Countries: A Retrospective Analysis of Mortality Registers

Background

Socioeconomic inequalities in alcohol-related mortality have been documented in several European countries, but it is unknown whether the magnitude of these inequalities differs between countries and whether these inequalities increase or decrease over time.

Methods and Findings

We collected and harmonized data on mortality from four alcohol-related causes (alcoholic psychosis, dependence, and abuse; alcoholic cardiomyopathy; alcoholic liver cirrhosis; and accidental poisoning by alcohol) by age, sex, education level, and occupational class in 20 European populations from 17 different countries, both for a recent period and for previous points in time, using data from mortality registers. Mortality was age-standardized using the European Standard Population, and measures for both relative and absolute inequality between low and high socioeconomic groups (as measured by educational level and occupational class) were calculated.Rates of alcohol-related mortality are higher in lower educational and occupational groups in all countries. Both relative and absolute inequalities are largest in Eastern Europe, and Finland and Denmark also have very large absolute inequalities in alcohol-related mortality. For example, for educational inequality among Finnish men, the relative index of inequality is 3.6 (95% CI 3.3–4.0) and the slope index of inequality is 112.5 (95% CI 106.2–118.8) deaths per 100,000 person-years. Over time, the relative inequality in alcohol-related mortality has increased in many countries, but the main change is a strong rise of absolute inequality in several countries in Eastern Europe (Hungary, Lithuania, Estonia) and Northern Europe (Finland, Denmark) because of a rapid rise in alcohol-related mortality in lower socioeconomic groups. In some of these countries, alcohol-related causes now account for 10% or more of the socioeconomic inequality in total mortality.Because our study relies on routinely collected underlying causes of death, it is likely that our results underestimate the true extent of the problem.

Conclusions

Alcohol-related conditions play an important role in generating inequalities in total mortality in many European countries. Countering increases in alcohol-related mortality in lower socioeconomic groups is essential for reducing inequalities in mortality. Studies of why such increases have not occurred in countries like France, Switzerland, Spain, and Italy can help in developing evidence-based policies in other European countries.     

A role for female ornamentation in the facultatively polygynous mating system of collared flycatchers

In a polygynous mating system, females settling with alreadymated males often experience low mating success due to the reducedparental contribution of the male. However, there are numerousfactors that may still make it advantageous for some femalesto choose this mating status. Facultative polygyny is believedto be dominated by male advertisement and female choice. Althoughquality differences and competition among females are increasinglyrecognized as important determinants of polygynous settlementpatterns, the importance of signals of female quality in thismating system is largely unknown. Here we examined the relationshipof the white wing patch size (WPS) of female collared flycatchers,a phenotypically plastic and age-dependent ornament, with socialmating status, while controlling for settlement date and age.At the population level, monogamous, primary, and secondaryfemales did not differ in WPS. However, the primary female ofindividual males was more ornamented than the secondary female,and this difference declined with increasing distance betweenprimary and secondary nests. Secondary female ornamentationincreased, whereas that of the primary female did not changewith nest distance. These results suggest a subtle role forfemale ornamentation at polygynous mating. Future studies shouldtherefore take into account mating status when assessing thecosts and benefits of female signals. Moreover, patterns inquality-indicating female traits may contribute to the explanationof differences in reproductive success among females of differentmating status.     

Simultaneous treatment with an aromatase inhibitor and an anti-androgen decreases the likelihood of dawn song in free-living male great tits, Parus major

Gonadal steroids, most importantly testosterone (T), are considered to be a major factor in the expression of adult song behavior in temperate-zone songbirds. The action of T within specific brain regions involved in the regulation of song may occur either directly, or through its androgenic or estrogenic metabolites. In the present study, we tested steroid-dependence of great tit dawn song by blocking both known pathways of T action by simultaneous implantation of flutamide, an anti-androgen, and ATD, an aromatase inhibitor. By our knowledge, this is the first study investigating the effects of androgen inhibitors on dawn song in free-living birds. Male great tits were implanted during their mate's egg laying stage, being the time of maximal male song activity at dawn. Treatment with ATD and flutamide significantly increased plasma T levels, probably because feedback mechanisms on T secretion were inhibited. The treatment decreased the likelihood of showing dawn song, which is in line with the hypothesis that sex steroids are involved in the endocrine control of song behavior. In males that did show dawn song, we found no evidence for a treatment effect on song quality. Although the implants were present for the larger part of the breeding season, males were able to maintain control of a territory and mate and to complete their brood cycle as successful as control males.     

Testosterone, testes size, and mating success in birds: a comparative study

Reproductive behaviors of vertebrates are often underpinned by temporal patterns of hormone secretion. We investigated interspecific patterns of circulating testosterone in male birds to test the hypothesis that testosterone plays a crucial role in sexual selection as determined by degree of polygyny and extra-pair paternity. We predicted that the evolution of increased levels of polygyny and extra-pair paternity would have resulted in the evolution of increased levels of testosterone to allow males more efficiently to compete for mates. This hypothesis was tested in comparative analyses of 116 species of birds using Generalized Least Squares Models. We assessed the importance of latitudinal distribution, because this can confound the relationship between testosterone and mating success. There were weak positive phylogenetic correlations between measures of testosterone and estimates of mating success at the social level, but this association appeared to be confounded by latitudinal distribution, a significant correlate of testosterone titers. However, we found a significantly positive relationship between peak and residual peak testosterone (which is the peak testosterone level that is controlled for the baseline level) and extra-pair paternity independent of latitude. These results suggest that selection pressures arising from social and sexual mating differently affected testosterone levels with the former being mediated by factors associated with latitudinal distribution. An analysis of residual testes size revealed a positive association between peak and residual testosterone and testes size relative to body size. In a path analysis, we show that relative testis size primarily evolved in association with intense sperm competition and thus high sperm production, and these mechanisms had a secondary impact on blood testosterone levels at a phylogenetic scale. Our results suggest that sperm competition has played an important role in the evolution of reproductive mechanisms in birds.