Enterotypes of the human gut microbiome

Our knowledge of species and functional composition of the human gut microbiome is rapidly increasing, but it is still based on very few cohorts and little is known about variation across the world. By combining 22 newly sequenced faecal metagenomes of individuals from four countries with previously published data sets, here we identify three robust clusters (referred to as enterotypes hereafter) that are not nation or continent specific. We also confirmed the enterotypes in two published, larger cohorts, indicating that intestinal microbiota variation is generally stratified, not continuous. This indicates further the existence of a limited number of well-balanced host-microbial symbiotic states that might respond differently to diet and drug intake. The enterotypes are mostly driven by species composition, but abundant molecular functions are not necessarily provided by abundant species, highlighting the importance of a functional analysis to understand microbial communities. Although individual host properties such as body mass index, age, or gender cannot explain the observed enterotypes, data-driven marker genes or functional modules can be identified for each of these host properties. For example, twelve genes significantly correlate with age and three functional modules with the body mass index, hinting at a diagnostic potential of microbial markers.     

Technique de coloration histologique de tissus inclus dans des polyesters

Summary A simple staining method for sections of tissues embedded in polyester is described. It can easily be performed and is valuable for comparison with ultrathin sections used in electron cytology.     

The site of gating in the ventricular conducting system of rabbit,dog and monkey hearts

Summary The longest action potential durations of the ventricular conducting system were found at about two thirds of the distance along each false tendon in dog and monkey hearts. In the rabbit heart, this area—which corresponds to the gating mechanism—was found in the middle part of the bundle branches; therefore the number of gates is much smaller in the rabbit than in the other 2 species.Acknowledgements. We wish to thank F. Pezziardi and P. Guiraudou for their technical assistance.     

Photoperiodic induction of synchronous flowering near the Equator

In tropical rainforests, 30-65% of tree species grow at densities of less than one individual per hectare. At these low population densities, successful cross-pollination relies on synchronous flowering. In rainforests with low climatic seasonality, photoperiodic control is the only reliable mechanism for inducing synchronous flowering. This poses a problem because there is no variation in day length at the Equator. Here we propose a new mechanism of photoperiodic timekeeping based on the perception of variation in sunrise or sunset time, which explains and predicts the annually repeated, staggered, synchronous and bimodal flowering of many tree species in Amazonian rainforests near the Equator.     

Phase transformation kinetics in metastable titanium alloys

We investigated the phase transformation sequence,kinetics,and microstructural evolutions during heating,isothermal treatment,and continuous cooling of the metastable Ti–B19 alloy.On the basis of these results,we summarized the phase transformation characteristics of this kind of alloys,especially the metastable b-Ti alloy.We also analyzed and discussed the possibility of describing the size,morphology,and distribution of precipitates as well as the possibility of and complications in establishing relationships among the chemical composition,microstructure,processing parameters,and properties of the metastable Ti–B19 alloy.     

Dephosphorylation and activation of Xenopus p34cdc2 protein kinase during the cell cycle

Genetic studies in the fission yeast Schizosaccharomyces pombe have established that a critical element required for the G2----M-phase transition in the cell cycle is encoded by the cdc2+ gene. The product of this gene is a serine/threonine protein kinase, designated p34cdc, that is highly conserved functionally from yeast to man2 and has a relative molecular mass of 34,000 (34 K). Purified maturation-promoting factor (MPF) is a complex of p34cdc2 and a 45K substrate that appears in late G2 phase and is sufficient to drive cells into mitosis. This factor has been identified in all eukaryotic cells, and in vitro histone H1 is the preferred substrate for phosphorylation. The increase in the activity of H1 kinase in M-phase is associated with a large increase in total cell protein phosphorylation which is believed to be a consequence of MPF activation. We show here that the H1 kinase activity of p34cdc2 oscillates during the cell cycle in Xenopus, and maximal activity correlates with the dephosphorylated state of p34cdc2. Direct inactivation of MPF in vitro is accompanied by phosphorylation of p34cdc2 and reduction of its protein kinase activity.     

Isolation and composition of plasma membranes of bovine glomerulus]

Plasma membranes of Beef kidney glomeruli were prepared by ultracentrifugation on a discontinuous sucrose density gradient. They were characterized by specific marker enzyme activities and electron microscopy morphological studies. Amino acid composition revealed a high amount of hydrophobic residues. Carbohydrate amount was found to be as high as 8.9 p. cent of the dry weight.     

The site of gating in the ventricular conducting system of rabbit, dog and monkey hearts

The longest action potential durations of the ventricular conducting system were found at about two thirds of the distance along each false tendon in dog and monkey hearts. In the rabbit heart, this area which corresponds to the gating mechanism - was found in the middle part of the bundle branches; therefore the number of gates is much smaller in the rabbit than in other 2 species.