Composition lipidique membranaire durant la préparation de spermatozoïdes à la fécondation

The final modifications that the spermatozoa undergo correspond with the destabilization of their plasma membrane. This indispensable step facilitates the fusion of membranes and primes the signal transduction during fertilization. This destabilization is composed of a series of changes and modulation of the lipids in membranes such as cholestérol, phospholipids and glycolipids. Several differences exist in the lipid composition of the plasma, acrosome, nuclear and mitochondrial membranes of spermatozoa. The principal membrane phospholipids are phosphatidyl choline, phosphatidyl ethanolamine and sphingomyelin. Plasma membrane of sperm is also rich in polyunsaturated fatty acids (PUFA) linked to phospholipids. Such as C₁₈∶2n?6, C₂₀∶4n?6 and large amounts of docosahexaenoic acid (C₂₂∶6n?6). The amount of membrane lipids in human sperm varies considerably between patients. This variation, could influence certain functional properties of the sperm cells such as their ability to undergo capacitation, the acrosome reaction and the fusion between sperm and oocyte membranes. The lipid composition of the human sperm cell can be altered during the process of freezing-thawing. A significant decrease in phospholipids (phosphatidyl choline, phosphatidyl ethanolamine), and PUFA in particular docosahexaenoic acid and arachidonic acid was observed. Human spermatozoa have a molar cholestérol/phopholipid ratio ≤1.0, and reduces during capacitation due to loss of cholestérol. In addition, the decrease in the levels of cholestérol and the methylation of phospholipids is involved in the modification of membrane fluidity and in the maturation of the sperm plasma membrane receptors. Therefore it seems that the methylation is important for the fusion between sperm and oocyte membranes. Intrinsic sperm phospholipase A2 also plays a role in the destabilization of the plasma membrane by producing of lysophospholipid. Therefore this enzyme and free fatty acids are believed to play a role in the acrosome reaction, an indispensable event facilitating the fusion between sperm and oocyte membranes.     

Evidence of land‐sea transfer of the zoonotic pathogen Campylobacter to a wildlife marine sentinel species

Environmental pollution often accompanies the expansion and urbanization of human populations where sewage and wastewaters commonly have an impact on the marine environments. Here, we explored the potential for faecal bacterial pathogens, of anthropic origin, to spread to marine wildlife in coastal areas. The common zoonotic bacterium Campylobacter was isolated from grey seals (Halichoerus grypus), an important sentinel species for environmental pollution, and compared to isolates from wild birds, agricultural sources and clinical samples to characterize possible transmission routes. Campylobacter jejuni was present in half of all grey seal pups sampled (24/50 dead and 46/90 live pups) in the breeding colony on the Isle of May (Scotland), where it was frequently associated with histological evidence of disease. Returning yearling animals (19/19) were negative for C. jejuni suggesting clearance of infection while away from the localized colony infection source. The genomes of 90 isolates from seals were sequenced and characterized using a whole‐genome multilocus sequence typing (MLST) approach and compared to 192 published genomes from multiple sources using population genetic approaches and a probabilistic genetic attribution model to infer the source of infection from MLST data. The strong genotype‐host association has enabled the application of source attribution models in epidemiological studies of human campylobacteriosis, and here assignment analyses consistently grouped seal isolates with those from human clinical samples. These findings are consistent with either a common infection source or direct transmission of human campylobacter to grey seals, raising concerns about the spread of human pathogens to wildlife marine sentinel species in coastal areas.     

Selectivity Parameters and Size at First Maturity in Deep-Water Shrimps, Aristaeomorpha foliacea (Risso, 1827) and Aristeus antennatus (Risso, 1816), from the North-Western Ionian Sea (Mediterranean Sea)

Selectivity experiments were carried out during trawling targeting deep-water shrimps Aristaeomorpha foliacea (Risso, 1827) and Aristeus antennatus (Risso, 1816) (Crustacea, Decapoda, Aristeidae) in the North-Western Ionian Sea (Eastern-Central Mediterranean). Different criteria were employed to analyse maturity; however, the proportion at 50% of retained, mated and mature specimens was always used to indicate the size, expressed as Carapace Length (CL, mm), at first capture (CL_c), mating (CL_sp) and at first maturity (CL_m), respectively. In order to estimate the size at 50% maturity (CL_m) for females of both species, three criteria were adopted. In particular, CL_m was computed for the mature females not considering the presence of spermatophores, for the mature females with spermatophores and for the mature females intersected by the decreasing proportion with size of females without spermatophores. Three diamond stretched mesh codends of 40, 50 and 60 mm were tested using a cover of 20 mm. The 40-mm stretched mesh size (European Union legal size in the Mediterranean) was not selective for the sampled population of each species. The size at first capture (CL_c), calculated in both species for the two sexes combined, increased significantly with mesh size. Even for the mesh size of 60 mm, the size at first capture was still smaller than the sizes at 50% maturity, whatever the criterion adopted. Since the differences between the size at first maturity and the sizes at first capture are greater in A. foliacea than A. antennatus, the former species appears in this respect to be more vulnerable to trawling than the latter.     

Bergmann's and Rensch's rules and the spur‐thighed tortoise (Testudo graeca)

Body size is an ecologically important variable in animals. The geographical size variation of most snakes and some lizards counters Bergmann's rule in that, among related taxa, the larger ones live at warmer latitudes. However, exceptions notwithstanding, and despite being ectothermic, turtles as a group tend to obey Bergmann's rule. We examined this idea in Testudo graeca, ranging from Morocco to Romania and to Iran with disputed systematics, both at the global scale (using literature) and within the focal area of Israel (using museum specimens). Both globally and locally, carapace length correlated with latitude, in accordance with Bergmann's rule. The scant data on reproduction fully support the hypothesis that Bergmann's rule enables larger clutches where the climate would limit repeated clutches. The sexual size dimorphism (SSD) was approached using two methodologies: (1) ‘conventional’, using globally literature data and locally museum samples and (2) ‘innovated’, using photographs of copulating tortoises from Israel and Turkey. By each methodology, SSD emerged as being male biased in the larger‐bodied populations and female biased in the smaller‐bodied populations, obeying Rensch's rule. Some observations support the hypothesis that the evolution of large males serves intermale combating. Finally, Rensch's rule was found to apply separately within Anatolia and within the Levant, possibly indicating that these populations are separate.     

Quantifying bacterial evolution in the wild: A birthday problem for Campylobacter lineages

Measuring molecular evolution in bacteria typically requires estimation of the rate at which nucleotide changes accumulate in strains sampled at different times that share a common ancestor. This approach has been useful for dating ecological and evolutionary events that coincide with the emergence of important lineages, such as outbreak strains and obligate human pathogens. However, in multi-host (niche) transmission scenarios, where the pathogen is essentially an opportunistic environmental organism, sampling is often sporadic and rarely reflects the overall population, particularly when concentrated on clinical isolates. This means that approaches that assume recent common ancestry are not applicable. Here we present a new approach to estimate the molecular clock rate in Campylobacter that draws on the popular probability conundrum known as the ‘birthday problem’. Using large genomic datasets and comparative genomic approaches, we use isolate pairs that share recent common ancestry to estimate the rate of nucleotide change for the population. Identifying synonymous and non-synonymous nucleotide changes, both within and outside of recombined regions of the genome, we quantify clock-like diversification to estimate synonymous rates of nucleotide change for the common pathogenic bacteria Campylobacter coli (2.4 x 10⁻⁶ s/s/y) and Campylobacter jejuni (3.4 x 10⁻⁶ s/s/y). Finally, using estimated total rates of nucleotide change, we infer the number of effective lineages within the sample time frame–analogous to a shared birthday–and assess the rate of turnover of lineages in our sample set over short evolutionary timescales. This provides a generalizable approach to calibrating rates in populations of environmental bacteria and shows that multiple lineages are maintained, implying that large-scale clonal sweeps may take hundreds of years or more in these species.     

Ethnic minorities and brothers in arms: competition and homophily in the military

Although the solidarity of brothers in arms is an important feature of the military, when it comes to ethnic minorities there is a pivotal paradox. On the one hand the military aims at drawing boundaries between soldiers and civilians by blurring existing ethnic and racial divisions inside the military. On the other hand the military is a highly national institution which prides itself on conservative values. Can these contradictions work? And how soldiers understand them? This paper examines the construction of ethnic boundaries in inter-group relations by focusing on the tension between ethnic hierarchy and competition versus homophily – the preference for maintaining ties with persons who are similar. Through participant observation and in-depth interviews with Dutch soldiers before and during deployment in Bosnia and Kosovo I ask when each strategy is put into work and why.     

Early Life Factors and Inter-Country Heterogeneity in BMI Growth Trajectories of European Children: The IDEFICS Study

Background

Starting from birth, this explorative study aimed to investigate between-country differences in body mass index (BMI) trajectories and whether early life factors explain these differences.

Methods

The sample included 7,644 children from seven European countries (Belgium, Cyprus, Germany, Hungary, Italy, Spain, Sweden) participating in the multi-centre IDEFICS study. Information on early life factors and in total 53,409 repeated measurements of height and weight from 0 to <12 years of age were collected during the baseline (2007/2008) and follow-up examination (2009/2010) supplemented by records of routine child health visits. Country-specific BMI growth curves were estimated using fractional polynomial mixed effects models. Several covariates focussing on early life factors were added to the models to investigate their role in the between-countries differences.

Results

Large between-country differences were observed with Italian children showing significantly higher mean BMI values at all ages ≥ 3 years compared to the other countries. For instance, at age 11 years mean BMI values in Italian boys and girls were 22.3 [21.9;22.8; 99% confidence interval] and 22.0 [21.5;22.4], respectively, compared to a range of 18.4 [18.1;18.8] to 20.3 [19.8;20.7] in boys and 18.2 [17.8;18.6] to 20.3 [19.8;20.7] in girls in the other countries. After adjustment for early life factors, differences between country-specific BMI curves became smaller. Maternal BMI was the factor being most strongly associated with BMI growth (p<0.01 in all countries) with associations increasing during childhood. Gestational weight gain (GWG) was weakly associated with BMI at birth in all countries. In some countries, positive associations between BMI growth and children not being breastfed, mothers’ smoking during pregnancy and low educational level of parents were found.

Conclusion

Early life factors seem to explain only some of the inter-country variation in growth. Maternal BMI showed the strongest association with children’s BMI growth.