Études stratigraphique,sédimentologique et paléomagnétique des travertins de Kocabaş, Bassin de Denizli,Anatolie, Turquie,contenant des restes fossiles quaternaires

Stratigraphic, sedimentological and paleomagnetic studies were conducted on the travertine from Denizli Basin, near Kocabas village, in the Denizli region in Turkey, following the paleontological discovery in 2002. The stratigraphic and sedimentological studies show at least two main cycles of mass travertine, separated by a fluvial deposit and overlain by a fluvio-lacustrine deposit. These travertines must have formed in environments with strong hydrodynamics (streams or waterfalls) and are preferentially located at breaks of slopes. The paleomagnetic study shows that all the quarry travertine presents reverse magnetic polarity. On the other hand, the detrital fluvio-lacustrine deposit above the travertine presents normal geomagnetic polarity, except at the top, where it is reversed. Given the presence of an archaic Homo erectus skull and Villafranchian paleontological remains in the upper travertine unit, the whole travertine dates from the upper Matuyama, and is more recent than the Olduvai event (1.78 Ma). The normal polarity recorded in the upper fluvio-lacustrine deposit could correspond to the Cobb Mountain excursion, dated to 1.22 Ma.     

Loss of function of MULTICOPY SUPPRESSOR OF IRA 1 produces nonviable parthenogenetic embryos in Arabidopsis

In sexually reproducing species, fertilization brings together in the zygote the genomes of the female and male gametes. In several animal species, female gametes are able to initiate embryogenesis in the absence of fertilization, a process referred to as parthenogenesis. Parthenogenesis has been engineered in mice by tampering with expression of loci under epigenetic controls [1]. In plants, embryo development in the absence of fertilization has been reported in cases in which meiosis is bypassed leading to apomictic development, and parthenogenetic development from a reduced egg cell has been only reported in rare accidental cases [2]. We report that single mutations in the gene MULTICOPY SUPPRESSOR OF IRA 1 (MSI1) are able to initiate parthenogenetic development of the embryo in Arabidopsis thaliana from eggs cells produced by meiosis. The WD40 repeat protein MSI1 is part of the evolutionarily conserved Polycomb group (PcG) chromatin-remodeling complexes [3] and is homologous to the Retinoblastoma binding proteins P55 in Drosophila and RbAp48 in mammals [4]. Nonviable haploid parthenogenetic msi1 embryos express molecular markers and polarity similar to diploid wild-type (wt) embryos produced by fertilization, indicating a maternal contribution to early patterning of the Arabidopsis embryo.     

Datation des travertins de Kocabaş par la méthode des nucléides cosmogéniques Al/Be

The archaic Homo erectus Kocaba? skullcap was discovered at Kocaba?, Denizli, Turkey in travertine formations over- and underlain by conglomerate formations. These units dated by the ²⁶Al/¹⁰Be cosmogenic nuclide method constrained the skullcap age between 1.0 and 1.6 Ma.     

Visualizing Compaction of Polysomes in Bacteria

During protein synthesis, many translating ribosomes are bound together with an mRNA molecule to form polysomes (or polyribosomes). While the spatial organization of bacterial polysomes has been well studied in vitro, little is known about how they cluster when cellular conditions are highly constrained. To better understand this, we used electron tomography, template matching, and three-dimensional modeling to analyze the supramolecular network of ribosomes after induction of translational pauses. In Escherichia coli, we overexpressed an mRNA carrying a polyproline motif known to induce pausing during translation. When working with a strain lacking transfer-messenger RNA, the principle actor in the “trans-translation” rescuing system, the cells survived the hijacking of the translation machinery but this resulted in a sharp modification of the ribosomal network. The results of our experiments demonstrate that single ribosomes are replaced with large amounts of compacted polysomes. These polysomes are highly organized, principally forming hairpins and dimers of hairpins that stack together. We propose that these spatial arrangements help maintain translation efficiency when the rescue systems are absent or overwhelmed.     

A Biased Competition Theory of Cytotoxic T Lymphocyte Interaction with Tumor Nodules

The dynamics of the interaction between Cytotoxic T Lymphocytes (CTL) and tumor cells has been addressed in depth, in particular using numerical simulations. However, stochastic mathematical models that take into account the competitive interaction between CTL and tumors undergoing immunoediting, a process of tumor cell escape from immunesurveillance, are presently missing. Here, we introduce a stochastic dynamical particle interaction model based on experimentally measured parameters that allows to describe CTL function during immunoediting. The model describes the competitive interaction between CTL and melanoma cell nodules and allows temporal and two-dimensional spatial progression. The model is designed to provide probabilistic estimates of tumor eradication through numerical simulations in which tunable parameters influencing CTL efficacy against a tumor nodule undergoing immunoediting are tested. Our model shows that the rate of CTL/tumor nodule productive collisions during the initial time of interaction determines the success of CTL in tumor eradication. It allows efficient cytotoxic function before the tumor cells acquire a substantial resistance to CTL attack, due to mutations stochastically occurring during cell division. Interestingly, a bias in CTL motility inducing a progressive attraction towards a few scout CTL, which have detected the nodule enhances early productive collisions and tumor eradication. Taken together, our results are compatible with a biased competition theory of CTL function in which CTL efficacy against a tumor nodule undergoing immunoediting is strongly dependent on guidance of CTL trajectories by scout siblings. They highlight unprecedented aspects of immune cell behavior that might inspire new CTL-based therapeutic strategies against tumors.     

Control of reproduction by Polycomb Group complexes in animals and plants

In both mammals and plants, Polycomb Repressive Complexes 2 (PRC2) are conserved and appear to be involved in the transition between vegetative or somatic and reproductive state in plants and mammals. In plants at least three different PRC2 control temporal aspects of development, and mutations in PcG cause heterochronies. Such heterochronic mutations affect the transition to flowering. During gametogenesis the Fertilization-Independent Endosperm-MEDEA-PRC2 (FIE-MEA PRC2) complex controls gametogenesis in synergy with a Retinoblastoma-dependent pathway. Several genes of the FIE-MEA pathway are imprinted as shown by their uniparental allele expression in the endosperm, the interface controlling maternal nutrition of the embryo in the seed. Imprinting is also a major feature for genes expressed in the placenta in mammals. Recent data have shown that imprinting in both placenta and endosperm likely share similar mechanisms involving cooperation between the PRC2 complexes and DNA methylation.     

Identification of new members of Fertilisation Independent Seed Polycomb Group pathway involved in the control of seed development in Arabidopsis thaliana

In higher plants, double fertilisation initiates seed development. One sperm cell fuses with the egg cell and gives rise to the embryo, the second sperm cell fuses with the central cell and gives rise to the endosperm. The endosperm develops as a syncytium with the gradual organisation of domains along an anteroposterior axis defined by the position of the embryo at the anterior pole and by the attachment to the placenta at the posterior pole. We report that ontogenesis of the posterior pole in Arabidopsis thaliana involves oriented migration of nuclei in the syncytium. We show that this migration is impaired in mutants of the three founding members of the FERTILIZATION INDEPENDENT SEED (FIS) class, MEDEA (MEA), FIS2 and FERTILIZATION INDEPENDENT ENDOSPERM (FIE). A screen based on a green fluorescent protein (GFP) reporter line allowed us to identify two new loci in the FIS pathway, medicis and borgia. We have cloned the MEDICIS gene and show that it encodes the Arabidopsis homologue of the yeast WD40 domain protein MULTICOPY SUPRESSOR OF IRA (MSI1). The mutations at the new fis loci cause the same cellular defects in endosperm development as other fis mutations, including parthenogenetic development, absence of cellularisation, ectopic development of posterior structures and overexpression of the GFP marker.     

Physical activity-related energy expenditure with the RT3 and TriTrac accelerometers in overweight adults

Objective: The objective was to evaluate two accelerometers, the RT3 and the TriTrac‐R3D for their ability to produce estimates of physical activity‐related energy expenditure (PAEE) in overweight/obese adults. Research Methods and Procedures: PAEE estimates from both accelerometers were obtained in two experiments. In Experiment 1, 13 overweight/obese subjects (BMI 34.2 ± 6.4 kg/m²) were monitored over 2 weeks in everyday life, PAEE being simultaneously measured by the doubly labeled water method (DLW). In Experiment 2, 8 overweight/obese subjects (BMI 34.3 ± 5.0 kg/m²) and 10 normal‐weight subjects (BMI 20.8 ± 2.1 kg/m²) were monitored during a treadmill walking protocol, PAEE being simultaneously measured by indirect calorimetry. Results: In Experiment 1, there was no significant difference between methods in mean PAEE (DLW: 704 ± 223 kcal/d, RT3: 656 ± 140 kcal/d, TriTrac‐R3D 624 ± 419 kcal/d). The relative difference between methods (accelerometer vs. DLW) was ?17.1% ± 16.7% for the RT3 and ?20.0 ± 44.6% for the TriTrac‐R3D. Correlation for PAEE between RT3 and DLW was higher than between TriTrac‐R3D and DLW (r = 0.67, p < 0.05 and r = 0.36, p = 0.25, respectively). The 95% confidence interval (CI) (kcal/d) of the mean difference between methods was large, amounting to ?385 to 145 for the RT3 and ?887 to 590 for the TriTrac‐R3D. In Experiment 2, both accelerometers were sensitive to the changes in treadmill speed, with no significant difference in mean PAEE between methods in overweight/obese subjects. Conclusions: Although both accelerometers did not provide accurate estimates of PAEE at individual levels, the data suggest that RT3 has the potential to assess PAEE at group levels in overweight/obese subjects.