Good genes drive female choice for mating partners in the lek-breeding European treefrog.

Investigating the mechanisms underlying female mate choice is important for sexual-selection theory, but also for population-genetic studies, because distinctive breeding strategies affect differently the dynamics of gene diversity within populations. Using field-monitoring, genetic-assignment, and laboratory-rearing methods, we investigated chorus attendance, mating success and offspring fitness in a population of lek-breeding tree-frogs (Hyla arborea) to test whether female choice is driven by good genes or complementary genes. Chorus attendance explained approximately 50% of the variance in male mating success, but did not correlate with offspring fitness. By contrast, offspring body mass and growth rate correlated with male attractiveness, measured as the number of matings obtained per night of calling. Genetic similarity between mating partners did not depart from random, and did not affect offspring fitness. We conclude that females are able to choose good partners under natural settings and obtain benefits from the good genes, rather than compatible genes, their offspring inherit. This heritability of fitness is likely to reduce effective population sizes below values previously estimated.

Strength and cost of an induced immune response are associated with a heritable melanin-based colour trait in female tawny owls.

1. Melanin pigments provide the most widespread source of coloration in vertebrates, but the adaptive function of such traits remains poorly known. 2. In a wild population of tawny owls (Strix aluco), we investigated the relationships between plumage coloration, which varies continuously from dark to pale reddish, and the strength and cost of an induced immune response. 3. The degree of reddishness in tawny owl feather colour was positively correlated with the concentration of phaeomelanin and eumelanin pigments, and plumage coloration was highly heritable (h(2) = 0.93). No carotenoids were detected in the feathers. 4. In mothers, the degree of melanin-based coloration was associated with antibody production against a vaccine, with dark reddish females maintaining a stronger level of antibody for a longer period of time compared to pale reddish females, but at a cost in terms of greater loss of body mass. 5. A cross-fostering experiment showed that, independent of maternal coloration, foster chicks reared by vaccinated mothers were lighter than those reared by nonvaccinated mothers. Hence, even though dark reddish mothers suffered a stronger immune cost than pale reddish mothers, this asymmetric cost was not translated to offspring growth. 6. Our study suggests that different heritable melanin-based colorations are associated with alternative strategies to resist parasite attacks, with dark reddish individuals investing more resources towards the humoral immune response than lightly reddish conspecifics.

BAFF mediates survival of peripheral immature B lymphocytes.

B cell maturation is a very selective process that requires finely tuned differentiation and survival signals. B cell activation factor from the TNF family (BAFF) is a TNF family member that binds to B cells and potentiates B cell receptor (BCR)-mediated proliferation. A role for BAFF in B cell survival was suggested by the observation of reduced peripheral B cell numbers in mice treated with reagents blocking BAFF, and high Bcl-2 levels detected in B cells from BAFF transgenic (Tg) mice. We tested in vitro the survival effect of BAFF on lymphocytes derived from primary and secondary lymphoid organs. BAFF induced survival of a subset of splenic immature B cells, referred to as transitional type 2 (T2) B cells. BAFF treatment allowed T2 B cells to survive and differentiate into mature B cells in response to signals through the BCR. The T2 and the marginal zone (MZ) B cell compartments were particularly enlarged in BAFF Tg mice. Immature transitional B cells are targets for negative selection, a feature thought to promote self-tolerance. These findings support a model in which excessive BAFF-mediated survival of peripheral immature B cells contributes to the emergence and maturation of autoreactive B cells, skewed towards the MZ compartment. This work provides new clues on mechanisms regulating B cell maturation and tolerance.

Education and male-female differences in later-life cognition: international evidence from latin america and the Caribbean.

This study explores the role of early-life education for differences in cognitive functioning between men and women aged 60 and older from seven major urban areas in Latin America and the Caribbean. After documenting statistically significant differences in cognitive functioning between men and women for six of the seven study sites, I assess the extent to which these differences can be explained by prevailing male-female differences in education. I decompose predicted male-female differences in cognitive functioning based on various statistical models for later-life cognition and find robust evidence that male-female differences in education are a major driving force behind cognitive functioning differences between older men and women. This study therefore suggests that early-life differences in educational attainment between boys and girls during childhood have a lasting impact on gender inequity in cognitive functioning at older ages. Increases in educational attainment and the closing of the gender gap in education in many countries in Latin America and the Caribbean may thus result in both higher levels and a more gender-equitable distribution of later-life cognition among the future elderly in those countries.

Triade de la femme sportive [Female athlete triad]

The practitioner, as well as specialist such as gynecologist and endocrinologist, may face in their office women with eating disorders, abnormalities of menstrual cycles and low bone mass, which may be the first hints of the female athlete triad. In these situations, the practitioner may search other findings of these triad by looking at some particular physical findings and by using appropriate questionnaire. In some advanced forms of this triad specific abnormalities of eating disorders (anorexia and boulimia) may be present as well as amenorrhea and osteoporosis, which may disturb the well-being and cause health damages of women practising sport either as amateur or in a elite setting. An appropriate handling of such disorders has to be proposed to these women.

Thymic lineage commitment rather than selection causes genetic variations in size of CD4 and CD8 compartments.

During their development, immature CD4+ CD8+ thymocytes become committed to either the CD4 or CD8 lineage. Subsequent complete maturation of CD4+ and CD8+ cells requires a molecular match of the expressed coreceptor and the MHC specificity of the TCR. The final size of the mature CD4+ and CD8+ thymic compartments is therefore determined by a combination of lineage commitment and TCR-mediated selection. In humans and mice, the relative size of CD4+ and CD8+ peripheral T cell compartments shows marked genetic variability. We show here that genetic variations in thymic lineage commitment, rather than TCR-mediated selection processes, are responsible for the distinct CD4/CD8 ratios observed in common inbred mouse strains. Genetic variations in the regulation of lineage commitment open new ways to analyze this process and to identify the molecules involved.

A limited role for beta-selection during gamma delta T cell development.

T cells belong to two distinct lineages expressing either alpha beta or gamma delta TCR. During alpha beta T cell development, it is clearly established that productive rearrangement at the TCR beta locus in immature precursor cells leads to the expression of a pre-TCR complex. Signaling through the pre-TCR results in the selective proliferation and maturation of TCR beta+ cells, a process that is known as beta-selection. However, the potential role of beta-selection during gamma delta T cell development is controversial. Whereas PCR-RFLP and sequencing techniques have provided evidence for a bias toward in-frame VDJ beta rearrangements in gamma delta cells (consistent with beta-selection), gamma delta cells apparently develop normally in mice that are unable to assemble a pre-TCR complex due to a deficiency in TCR beta or pT alpha genes. In this report, we have directly addressed the physiologic significance of beta-selection during gamma delta cell development in normal mice by quantitating intracellular TCR beta protein in gamma delta cells and correlating its presence with cell cycle status. Our results indicate that beta-selection plays a significant (although limited) role in gamma delta cell development by selectively amplifying a minor subset of gamma delta precursor cells with productively rearranged TCR beta genes.

Breeding rate is associated with pheomelanism in male and with eumelanism in female barn owls

Melanin-based coloration exists in 2 types: black eumelanism and reddish-brown pheomelanism, which both have a strong heritable component. To test whether these 2 types of melanism are associated with alternative adaptations, we carried out a correlative study over 8 years and an experiment in a Swiss population of barn owls, Tyto alba. This species varies in coloration from reddish-brown to white and from lightly to heavily marked with black spots. Based on the fact that plumage coloration and spottiness are male- and female-specific secondary sexual characters, respectively, we examined whether the probability of breeding is associated with the degree of pheomelanism in males and of eumelanism in females. In males, recruited nestlings were significantly less reddish-brown than their nonrecruited nest mates. In females, individuals displaying larger black spots started to breed at a younger age and had a higher survival, and females with experimentally reduced plumage spottiness bred less often than control females. Therefore, in the barn owl, the degree of male pheomelanism is associated with the probability of being recruited in the local population, whereas the degree of female eumelanism correlates with age at sexual maturity, survival probability, and also the probability of skipping reproduction.

Microarray and RNAi Analysis of P450s in Anopheles gambiae Male and Female Steroidogenic Tissues: CYP307A1 Is Required for Ecdysteroid Synthesis.

In insects, the steroid hormone 20-hydroxyecdysone (20E) coordinates major developmental transitions. While the first and the final steps of 20E biosynthesis are characterized, the pathway from 7-dehydrocholesterol to 5β-ketodiol, commonly referred as the "black box", remains hypothetical and whether there are still unidentified enzymes is unknown. The black box would include some oxidative steps, which are believed to be mediated by P450 enzymes. To identify new enzyme(s) involved in steroid synthesis, we analyzed by small-scale microarray the expression of all the genes encoding P450 enzymes of the malaria mosquito Anopheles gambiae in active steroidogenic organs of adults, ovaries from blood-fed females and male reproductive tracts, compared to inactive steroidogenic organs, ovaries from non-blood-fed females. Some genes encoding P450 enzymes were specifically overexpressed in female ovaries after a blood-meal or in male reproductive tracts but only three genes were found to be overexpressed in active steroidogenic organs of both females and males: cyp307a1, cyp4g16 and cyp6n1. Among these genes, only cyp307a1 has an expression pattern similar to other mosquito steroidogenic genes. Moreover, loss-of-function by transient RNAi targeting cyp307a1 disrupted ecdysteroid production demonstrating that this gene is required for ecdysteroid biosynthesis in Anopheles gambiae.

Enhanced visuospatial memory following intracerebroventricular administration of nerve growth factor

The present work assessed the effects of intracerebroventricular injections of rh recombined human nerve growth factor (rh NGF) (5 micrograms/2.5 microl) at postnatal days 12 and 13 upon the development of spatial learning capacities. The treated rats were trained at the age of 22 days to escape onto an invisible platform at a fixed position in space in a Morris navigation task. For half of the subjects, the training position was also cued, a procedure aimed at facilitating escape and at reducing attention to the distant spatial cues. Later, at the age of 6 months, all the rats were trained in a radial-arm maze task. Treatment effects were found in both immature and adult rats. The injection of NGF improved the performance in the Morris navigation task in both training conditions. There was a significant reduction in the escape latency and an increased bias toward the training platform quadrant during probe trials. The most consistent effect was the precocious development of an adult-like spatial memory. In the radial-arm maze, the NGF-treated rats made significantly fewer reentries than vehicle rats and this effect was particularly marked in the treated female rats. Taken together, these experiments reveal that the development and the maintenance of an accurate spatial representation are tightly related to the development of brain structures facilitated by the action of NGF. Moreover, these experiments demonstrate that an acute pharmacological treatment that leads to a transient modification in the choline acetyltransferase activity can induce a behavioral change long after the treatment.

Neuropathological, clinical and molecular pathology in female fragile X premutation carriers with and without FXTAS.

Fragile X-associated tremor/ataxia syndrome (FXTAS) is an adult-onset neurodegenerative disorder associated with premutation alleles of the fragile X mental retardation 1 (FMR1) gene. Approximately 40% of older male premutation carriers, and a smaller proportion of females, are affected by FXTAS; due to the lower penetrance the characterization of the disorder in females is much less detailed. Core clinical features of FXTAS include intention tremor, cerebellar gait ataxia and frequently parkinsonism, autonomic dysfunction and cognitive deficits progressing to dementia in up to 50% of males. In this study, we report the clinical, molecular and neuropathological findings of eight female premutation carriers. Significantly, four of these women had dementia; of the four, three had FXTAS plus dementia. Post-mortem examination showed the presence of intranuclear inclusions in all eight cases, which included one asymptomatic premutation carrier who died from cancer. Among the four subjects with dementia, three had sufficient number of cortical amyloid plaques and neurofibrillary tangles to make Alzheimer's disease a highly likely cause of dementia and a fourth case had dementia with cortical Lewy bodies. Dementia appears to be more common than originally reported in females with FXTAS. Although further studies are required, our observation suggests that in a portion of FXTAS cases there is Alzheimer pathology and perhaps a synergistic effect on the progression of the disease may occur.

Female-biased mortality in experimentally parasitized Alpine Swift Apus melba nestlings

1. Sex-biased mortality in adult vertebrates is often attributed to lower immunocompetence and higher parasite susceptibility of males. Although sex-specific mortality has also been reported during growth, the importance of sex-specific immunocompetence and parasite susceptibility in explaining male-biased mortality remains ambiguous in growing individuals because of potentially confounding sources of mortality such as sexual dimorphism. 2. Here, we investigated sex-specific susceptibility to the blood-sucking louse fly Crataerina melbae and sex differences in cell-mediated immunity in a bird species that is sexually monomorphic both in size and plumage coloration at the nestling stage, the Alpine Swift, Apus melba. 3. For this purpose, we manipulated ectoparasite loads by adding or removing flies to randomly chosen nests in two years, and injected nestlings with mitogenic phytohaemagglutinin (PHA) in another year. 4. There were no significant differences between male and female offspring in immune response towards PHA, parasite load, and parasite-induced decrease in growth rate. Secondary sex ratios were however biased toward males in parasitized broods, and this was explained by a greater mortality of females in parasitized than deparasitized broods. 5. Our findings are in contrast to the widely accepted hypothesis that males suffer a greater cost of parasitism. We discuss alternative hypotheses accounting for female-specific mortality.