Aerial and underwater carbon metabolism of a Zostera noltii seagrass bed in the Banc d’Arguin, Mauritania

Community respiration and primary production were measured in a dense intertidal Zostera noltii bed on the Banc d’Arguin, Mauritania (West Africa) under aerial and submerged conditions. Metabolism was studied in situ in dark and transparent benthic chambers. CO₂ fluxes in the air were measured over a series of short-term incubations (3 min) using an infrared gas analyzer. Dissolved inorganic carbon fluxes were calculated from concentration changes during one-hour underwater incubations. Air and underwater irradiance levels were measured every minute throughout the experiments. Carbon respiration was lower in the air (2.2 mmol m⁻² h⁻¹) than underwater (5.0 mmol m⁻² h⁻¹); similarly, a production-irradiance model fitted to the data indicated that gross maximal photosynthetic rate was markedly lower during emergence (6.0 mmol C m⁻² h⁻¹) than under water (42.7 mmol C m⁻² h⁻¹). The δ¹³C values observed in shoots indicated a decrease in atmospheric CO₂ contribution, compared to dissolved inorganic carbon, in Z. noltii metabolism along a depth gradient within a single location. As the seagrass bed remains under a thin layer of water at low tide at the studied site, the large difference in primary production can be mainly attributed to photosynthesis inhibition by high pH and oxygen concentration, as well as to the negative feedback of self-shading by seagrass leaves during emersion. The observed differences in respiration can be explained by the oxygen deficit at night during low tide near the sediment surface, a deficit that is consistent with the abundance of anoxia-tolerant species.     

Time to exhaustion and time spent at a high percentage of VO2max in severe intensity domain in children and adults

The aim of the study was to compare time spent at a high percentage of VO2max (>90% of VO2max) (ts90%), time to achieve 90% of VO2max (ta90%), and time to exhaustion (TTE) for exercise in the severe intensity domain in children and adults. Fifteen prepubertal boys (10.3 ± 0.9 years) and 15 men (23.5 ± 3.6 years) performed a maximal graded exercise to determine VO2max, maximal aerobic power (MAP) and power at ventilatory threshold (PVTh). Then, they performed 4 constant load exercises in a random order at PVTh plus 50 and 75% of the difference between MAP and PVTh (PΔ50 and PΔ75) and 100 and 110% of MAP (P100 and P110). VO2max was continuously monitored. The P110 test was used to determine maximal accumulated oxygen deficit (MAOD). No significant difference was found in ta90% between children and adults. ts90% and TTE were not significantly different between children and adults for the exercises at PΔ50 and PΔ75. However, ts90% and TTE during P100 (p < 0.05 and p < 0.01, respectively) and P110 (p < 0.001) exercises were significantly shorter in children. Children had a significantly lower MAOD than adults (34.3 ± 9.4 ml · kg vs. 53.6 ± 11.1 ml · kg). A positive relationship (p < 0.05) was obtained between MAOD and TTE values during the P100 test in children. This study showed that only for intensities at, or higher than MAP, lower ts90% in children was linked to a reduced TTE, compared to adults. Shorter TTE in children can partly be explained by a lower anaerobic capacity (MAOD). These results give precious information about exercise intensity ranges that could be used in children's training sessions. Moreover, they highlight the implication of both aerobic and anaerobic processes in endurance performances in both populations.     

Differential mortalities of dengue-infected Aedes aegypti: preliminary results

Two ecotypes of Aedes aegypti, Ae. ae. aegypti and Ae. ae. formosus, were experimentally infected with a dengue 2 virus to test (1) the inheritance of susceptibility, and (2) the impact of infection on survival and reproduction. Ae. ae. aegypti, the main vector involved in dengue epidemics, displayed higher mortalities than Ae. ae. formosus, the ancestral form, which is a forest-dwelling, less anthropophilic species confined to Africa. Differential mortalities were observed between females with disseminated infection and females without disseminated infection. Ae. ae. formosus females with disseminated infection showed an increase in survival rate and reproduction success. These results are discussed in the light of changes in resource allocation that may occur in infected females.     

Distinct roles for Sir2 and RNAi in centromeric heterochromatin nucleation,spreading and maintenance

Epigenetically regulated heterochromatin domains govern essential cellular activities. A key feature of heterochromatin domains is the presence of hypoacetylated nucleosomes, which are methylated on lysine 9 of histone H3 (H3K9me). Here, we investigate the requirements for establishment, spreading and maintenance of heterochromatin using fission yeast centromeres as a paradigm. We show that establishment of heterochromatin on centromeric repeats is initiated at modular ‘nucleation sites’ by RNA interference (RNAi), ensuring the mitotic stability of centromere‐bearing minichromosomes. We demonstrate that the histone deacetylases Sir2 and Clr3 and the chromodomain protein Swi6^HP1 are required for H3K9me spreading from nucleation sites, thus allowing formation of extended heterochromatin domains. We discovered that RNAi and Sir2 along with Swi6^HP1 operate in two independent pathways to maintain heterochromatin. Finally, we demonstrate that tethering of Sir2 is pivotal to the maintenance of heterochromatin at an ectopic locus in the absence of RNAi. These analyses reveal that Sir2, together with RNAi, are sufficient to ensure heterochromatin integrity and provide evidence for sequential establishment, spreading and maintenance steps in the assembly of centromeric heterochromatin.     

A nuclear DNA barcode for eastern North American oaks and application to a study of hybridization in an Arboretum setting

DNA barcoding has proved difficult in a number of woody plant genera, including the ecologically important oak genus Quercus. In this study, we utilized restrictionsite‐associated DNA sequencing (RAD‐seq) to develop an economical single nucleotide polymorphism (SNP) DNA barcoding system that suffices to distinguish eight common, sympatric eastern North American white oak species. Two de novo clustering pipelines, PyRAD and Stacks, were used in combination with postclustering bioinformatic tools to generate a list of 291 potential SNPs, 80 of which were included in a barcoding toolkit that is easily implemented using MassARRAY mass spectrometry technology. As a proof‐of‐concept, we used the genotyping toolkit to infer potential hybridization between North American white oaks transplanted outside of their native range (Q. michauxii, Q. montana, Q muehlenbergii/Q. prinoides, and Q. stellata) into a horticultural collection surrounded by natural forests of locally native trees (Q. alba and Q. macrocarpa) in the living collection at The Morton Arboretum (Lisle, IL, USA). Phylogenetic and clustering analyses suggested low rates of hybridization between cultivated and native species, with the exception of one Q. michauxii mother tree, the acorns of which exhibited high admixture from either Q. alba or Q. stellata and Q. macrocarpa, and a hybrid between Q. stellata that appears to have backcrossed almost exclusively to Q. alba. Together, RAD‐seq and MassARRAY technologies allow for efficient development and implementation of a multispecies barcode for one of the more challenging forest tree genera.     

Nerve growth factor receptor TrkA signaling in breast cancer cells involves Ku70 to prevent apoptosis

The nerve growth factor (NGF)-tyrosine kinase receptor TrkA plays a critical role in various neuronal and non-neuronal cell types by regulating cell survival, differentiation, and proliferation. In breast cancer cells, TrkA stimulation results in the activation of cellular growth, but downstream signaling largely remains to be described. Here we used a proteomics-based approach to identify partners involved in TrkA signaling in breast cancer cells. Wild type and modified TrkA chimeric constructs with green fluorescent protein were transfected in MCF-7 cells, and co-immunoprecipitated proteins were separated by SDS-PAGE before nano-LC-MS/MS analysis. Several TrkA putative signaling partners were identified among which was the DNA repair protein Ku70, which is increasingly reported for its role in cell survival and carcinogenesis. Physiological interaction of Ku70 with endogenous TrkA was induced upon NGF stimulation in non-transfected cells, and co-localization was observed with confocal microscopy. Mass spectrometry analysis and Western blotting of phosphotyrosine immunoprecipitates demonstrated the induction of Ku70 tyrosine phosphorylation upon NGF stimulation. Interestingly no interaction between TrkA and Ku70 was detected in PC12 cells in the absence or presence of NGF, suggesting that it is not involved in the initiation of neuronal differentiation. In breast cancer cells, RNA interference indicated that whereas Ku70 depletion had no direct effect on cell survival, it induced a strong potentiation of apoptosis in TrkA-overexpressing cells. In conclusion, TrkA signaling appears to be proapoptotic in the absence of Ku70, and this protein might therefore play a role in the long time reported ambivalence of tyrosine kinase receptors that can exhibit both anti- and eventually proapoptotic activities.     

Mitochondrial DNA variation of modern Tuscans supports the near eastern origin of Etruscans

The origin of the Etruscan people has been a source of major controversy for the past 2,500 years, and several hypotheses have been proposed to explain their language and sophisticated culture, including an Aegean/Anatolian origin. To address this issue, we analyzed the mitochondrial DNA (mtDNA) of 322 subjects from three well-defined areas of Tuscany and compared their sequence variation with that of 55 western Eurasian populations. Interpopulation comparisons reveal that the modern population of Murlo, a small town of Etruscan origin, is characterized by an unusually high frequency (17.5%) of Near Eastern mtDNA haplogroups. Each of these haplogroups is represented by different haplotypes, thus dismissing the possibility that the genetic allocation of the Murlo people is due to drift. Other Tuscan populations do not show the same striking feature; however, overall, ~5% of mtDNA haplotypes in Tuscany are shared exclusively between Tuscans and Near Easterners and occupy terminal positions in the phylogeny. These findings support a direct and rather recent genetic input from the Near East--a scenario in agreement with the Lydian origin of Etruscans. Such a genetic contribution has been extensively diluted by admixture, but it appears that there are still locations in Tuscany, such as Murlo, where traces of its arrival are easily detectable.     

Reproducibility in Echocardiographic Assessment of Diastolic Function in a Population Based Study (The STANISLAS Cohort Study)

Introduction

There is limited evidence regarding intra-observer and inter-observer variations in echocardiographic measurements of diastolic function. This study aimed to assess this reproducibly within a population-based cohort study.

Methods

Sixty subjects in sinus rhythm were randomly selected among 4^th visit participants of the STANISLAS Cohort (Lorraine region, France). This 4^th examination systematically included M-mode, 2-dimensional, DTI and pulsed-wave Doppler echocardiograms. Reproducibility of variables was studied by intra-class correlation coefficients (ICC) and Bland Altman plots.

Results

Our population was on average middle-aged (50 ± 14y), overweight (BMI = 26 ± 6kg/m²) and non-smoking (87%) with a quarter of the participants having self-declared hypertension or treated with anti-hypertensive medication(s). Intra-observer ICC were > 0.90 for all analyzed parameters except for left ventricular ejection fraction (LVEF) which was 0.89 (0.81–0.93). The mean relative intra-observer differences were small and limits of agreement of relative differences were narrow for all considered parameters (<5% and <15% respectively). Inter-observer ICC were > 0.90 for all analyzed parameters except for LVEF (ICC = 0.87) and both mitral and pulmonary A wave duration (0.83 and 0.73 respectively). The mean relative inter-observer differences were <5% for all parameters except for pulmonary A wave duration (mean difference = 6.5%). Limits of agreement of relative differences were narrow (<15%), except for mitral A wave duration and velocity (both <20%) as well as left ventricular mass and pulmonary A wave duration (both <30%). Intra-observer agreements with regard to the presence and severity of diastolic dysfunction were excellent (Kappa = 0.93 (0.83–1.00) and 0.88 (0.75–0.99), respectively).

Conclusion

In this validation study within the STANISLAS cohort, diastolic function echocardiographic parameters were found to be highly reproducible. Diastolic dysfunction consequently appears as a highly effective clinical and research tool.     

Kinetic study of antitumor lymphocyte cytotoxicity in rats bearing progressive or regressive syngeneic colonic tumors

In order to perform a kinetic study of the antitumor lymphocyte-mediated cytotoxicity in syngeneic BDIX rats bearing progressive (TRb) or regressive (TSb) colonic tumors, the 51Cr release assay was adapted to this experimental model. Two groups of 72 rats were inoculated with TRb or TSb cells. Results failed to show any clear and univocal evolution of lymphocyte cytotoxicities against TRb or TSb cells. On the other hand these cytotoxicities were roughly at the same level than natural cytotoxicity (normal rats), and were always higher against TSb than TRb cells.