Oocyte-somatic cells interactions, lessons from evolution

BACKGROUND: Despite the known importance of somatic cells for oocyte developmental competence acquisition, the overall mechanisms underlying the acquisition of full developmental competence are far from being understood, especially in non-mammalian species. The present work aimed at identifying key molecular signals from somatic origin that would be shared by vertebrates. RESULTS: Using a parallel transcriptomic analysis in 4 vertebrate species - a teleost fish, an amphibian, and two mammals - at similar key steps of developmental competence acquisition, we identified a large number of species-specific differentially expressed genes and a surprisingly high number of orthologous genes exhibiting similar expression profiles in the 3 tetrapods and in the 4 vertebrates. Among the evolutionary conserved players participating in developmental competence acquisition are genes involved in key processes such as cellular energy metabolism, cell-to-cell communications, and meiosis control. In addition, we report many novel molecular actors from somatic origin that have never been studied in the vertebrate ovary. Interestingly, a significant number of these new players actively participate in Drosophila oogenesis. CONCLUSIONS: Our study provides a comprehensive overview of evolutionary-conserved mechanisms from somatic origin participating in oocyte developmental competence acquisition in 4 vertebrates. Together our results indicate that despite major differences in ovarian follicular structure, some of the key players from somatic origin involved in oocyte developmental competence acquisition would be shared, not only by vertebrates, but also by metazoans. The conservation of these mechanisms during vertebrate evolution further emphasizes the important contribution of the somatic compartment to oocyte quality and paves the way for future investigations aiming at better understanding what makes a good egg

A PARAMETRIC ANALYSIS FOR THE DAFALIAS-KALIAKIN BOUNDING SURFACE VISCOPLASTIC MODEL-BASED ON THE DIFLUPRESS LD TEST

In order to predict delayed settlements of heavy structures, the authors decided to use the elasto-viscoplastic model of Dafalias-Kaliakin. To identify the parameters of the constitutive equations, they use above all the data of a new in-situ test, the Diflupress L.D. designed to approach the creep behavior of soil. In a first section, the principle of the model is presented. Then, the important parameters of the model are identified, mostly from in-situ test data since the laboratory tests data are not numerous and reliable. Finally, a study of sensitivity on the parameters which influence the viscoplastic response of the model is made

The current environmental levels of endocrine disruptors (mercury, cadmium, organochlorine pesticides and PCBs) in a Belgian adult population and their predictors of exposure

A human biomonitoring study was carried out measuring the levels of endocrine disruptors in 252 participants (18-76 years old) recruited between February and May 2015 from the general population of Liege Province (Belgium). In this study, we reported the recent levels of cadmium and mercury in urine, some organochlorine pesticides and polychlorinated biphenyls (PCBs) in serum, and their relations to demographic characteristics, lifestyle behaviors and dietary habits. The median urinary levels of mercury and cadmium were 0.81 µg/l and <0.5µg/l respectively. The mercury levels were higher in participants having at least 3 dental amalgams, and consuming sea fish more than once a week. Although our mercury levels in most participants were lower than some health-based guidelines, they were higher than in our neighboring countries where ban or restrictions on the dental amalgams use were implemented. Urinary cadmium levels in current smokers were significantly higher than former or never smokers, as well as non-smokers for passively exposed vs non-exposed ones. Median PCB-153 and -180 serum levels were 53.8 and 41.1 ng/g lipid respectively, but PCB-138 was below the limit of quantification of 0.15 µg/l in 49% of the samples. Among the organochlorine pesticides, 4,4’-dichlorodiphenyldichloroethylene (4,4’-DDE), beta-hexachlorohexane and hexachlorobenzene were positively detected respectively in 48%, 49% and 37% of the serum samples. Eventhough, a dramatic decrease in organochlorines levels was observed, at least 1 pesticide or PCB was detected in 96% of our population, and more than 50% of our samples were contaminated by 4 or more organochlorines. Age, body mass index, and breastfeeding duration were the most predictive determinants of pesticide or PCB serum concentrations, but not dietary habits

Acidification is not involved in the early inhibition of Staphylococcus aureus growth by Lactococcus lactis in milk

Seventy-five Lactococcus lactis strains were screened for their inhibitory effect on Staphylococcus aureus growth in milk. Most lactococcal strains had a strong antagonistic effect. Characterization of this effect showed that acidification was not involved in the inhibition observed within the first 24 h of mixed culture. Alternate effects such as bacteriocin- or hydrogen peroxide-production were eliminated. These results question some generally accepted ideas and show that even low acidifying L. lactis strains, widely used in raw milk soft cheeses, can efficiently inhibit S. aureus growth even with initial contamination levels as high as 103 cfum

Nutritional Regulation of Mammary Gland Development and Milk Synthesis in Animal Models and Dairy Species

International audienceIn mammals, milk is essential for the growth, development, and health. Milk quantity and quality are dependent on mammary development, strongly influenced by nutrition. This review provides an overview of the data on nutritional regulations of mammary development and gene expression involved in milk component synthesis. Mammary development is described related to rodents, rabbits, and pigs, common models in mammary biology. Molecular mechanisms of the nutritional regulation of milk synthesis are reported in ruminants regarding the importance of ruminant milk in human health. The effects of dietary quantitative and qualitative alterations are described considering the dietary composition and in regard to the periods of nutritional susceptibly. During lactation, the effects of lipid supplementation and feed restriction or deprivation are discussed regarding gene expression involved in milk biosynthesis, in ruminants. Moreover, nutrigenomic studies underline the role of the mammary structure and the potential influence of microRNAs. Knowledge from three lactating and three dairy livestock species contribute to understanding the variety of phenotypes reported in this review and highlight (1) the importance of critical physiological stages, such as puberty gestation and early lactation and (2) the relative importance of the various nutrients besides the total energetic value and their interaction

Interactions between Staphylococcus aureus and lactic acid bacteria: An old story with new perspectives

 Staphylococcus aureus is a Gram positive opportunistic pathogen and a major concern for both animal and human health worldwide. In some contexts where Lactic Acid Bacteria (LAB) are the normal dominant microbiota, such as in fermented food or in the vaginal ecosystem, S. aureus sometimes colonises, persists, expresses virulence factors and produces food poisoning or urogenital infections, respectively. Studies on the interactions between LAB and S. aureus began a few decades ago and were pursued to shed light on the inhibitory capabilities that LAB might have on S. aureus growth and/or enterotoxin production in fermented foodstuffs. These early studies had the aim of developing methods to prevent staphylococcal food poisoning, thus improving food safety. More recently, the concept of vaginal probiotic LAB has emerged as a promising way to prevent urogenital infections, S. aureus being one of the potential pathogens targeted. This review provides an up-to-date look at the current hypotheses of the mechanisms involved in the inhibition of S. aureus by LAB in both the vaginal ecosystem and in fermented food ecosystems. We also emphasise that post-genomic approaches can now be envisioned in order to study these diverse and complex interactions at the molecular level. Further works in this field will open up new avenues for methods of biocontrol by LAB and/or for biotechnological uses of LAB-compounds to fight against the long-standing, yet incumbent menace of staphylococcal infection

Mécanismes moléculaires de pathogénicité

Mécanismes moléculaires de pathogénicit

Operant conditioning of the visual smooth pursuit in young infants

International audienceSmooth pursuit is a complex behaviour which is not considered as totally functional at birth. The lack of maturation of the visuo-motor systems is generally invoked to explain this phenomenon. However, if this oculomotor response is an operant behaviour, an alternate explanation may be found in the absence of previous confrontation with the environmental contingencies. A first group of young infants were placed in situations in which their oculomotor responses could produce an auditory stimulus. In such situations, young infants are able to improve their pursuit. Music was randomly delivered to a second group. No music was delivered to a third group. For the last two groups no augmentation of the proportion of slow movements was observed. Our main conclusion is that visual tracking has the properties of an operant behaviour and may be enhanced at birth. These results will be discussed within the frameworks of the behavioural discrepancy and of the maturationist hypotheses of the ocular motor control

Transcriptomic Response of Lactococcus lactis in Mixed Culture with Staphylococcus aureus▿ †

The mechanisms of interaction between Lactococcus lactis and the food pathogen Staphylococcus aureus are of crucial importance, as one major role of lactic acid bacteria (LAB) in fermented foods is to inhibit undesirable and pathogenic flora. It was never questioned if the presence of a pathogen can actively modify the gene expression patterns of LAB in a shared environment. In this study, transcriptome and biochemical analyses were combined to assess the dynamic response of L. lactis in a mixed culture with S. aureus. The presence of S. aureus hardly affected the growth of L. lactis but dramatically modified its gene expression profile. The main effect was related to earlier carbon limitation and a concomitantly lower growth rate in the mixed culture due to the consumption of glucose by both species. More specific responses involved diverse cellular functions. Genes associated with amino acid metabolism, ion transport, oxygen response, menaquinone metabolism, and cell surface and phage expression were differentially expressed in the mixed culture. This study led to new insights into possible mechanisms of interaction between L. lactis and S. aureus. Moreover, new and unexpected effects of L. lactis on the virulence of S. aureus were discovered, as described elsewhere (S. Even, C. Charlier, S. Nouaille, N. L. Ben Zakour, M. Cretenet, F. J. Cousin, M. Gautier, M. Cocaign-Bousquet, P. Loubière, and Y. Le Loir, Appl. Environ. Microbiol. 75:4459-4472, 2009)

Gene expression in bovine and mouse cumulus cells in relation with oocyte maturation

International audienc