Faint dwarfs as a test of DM models: WDM vs. CDM

We use high resolution Hydro$+$N-Body cosmological simulations to compare the assembly and evolution of a small field dwarf (stellar mass ~ 10$^{6-7}$ M$\odot$, total mass 10$^{10}$ M$\odot$ in $\Lambda$ dominated CDM and 2keV WDM cosmologies. We find that star formation (SF) in the WDM model is reduced and delayed by 1-2 Gyr relative to the CDM model, independently of the details of SF and feedback. Independent of the DM model, but proportionally to the SF efficiency, gas outflows lower the central mass density through `dynamical heating', such that all realizations have circular velocities $<$ 20kms at 500$~$pc, in agreement with local kinematic constraints. As a result of dynamical heating, older stars are less centrally concentrated than younger stars, similar to stellar population gradients observed in nearby dwarf galaxies. Introducing an important diagnostic of SF and feedback models, we translate our simulations into artificial color-magnitude diagrams and star formation histories in order to directly compare to available observations. The simulated galaxies formed most of their stars in many $\sim$10 Myr long bursts. The CDM galaxy has a global SFH, HI abundance and Fe/H and alpha-elements distribution well matched to current observations of dwarf galaxies. These results highlight the importance of directly including `baryon physics' in simulations when 1) comparing predictions of galaxy formation models with the kinematics and number density of local dwarf galaxies and 2) differentiating between CDM and non-standard models with different DM or power spectra.Comment: 13 pages including Appendix on Color Magnitude Diagrams. Accepted by MNRAS. Added one plot and details on ChaNGa implementation. Reduced number of citations after editorial reques

Mechanical loading of stem cells for improvement of transplantation outcome in a model of acute myocardial infarction: The role of loading history

Stem cell therapy for tissue repair is a rapidly evolving field and the factors that dictate the physiological responsiveness of stem cells remain under intense investigation. In this study we hypothesized that the mechanical loading history of muscle-derived stem cells (MDSCs) would significantly impact MDSC survival, host tissue angiogenesis, and myocardial function after MDSC transplantation into acutely infarcted myocardium. Mice with acute myocardial infarction by permanent left coronary artery ligation were injected with either nonstimulated (NS) or mechanically stimulated (MS) MDSCs. Mechanical stimulation consisted of stretching the cells with equibiaxial stretch with a magnitude of 10% and frequency of 0.5Hz. MS cell-transplanted hearts showed improved cardiac contractility, increased numbers of host CD31+ cells, and decreased fibrosis, in the peri-infarct region, compared to the hearts treated with NS MDSCs. MS MDSCs displayed higher vascular endothelial growth factor expression than NS cells in vitro. These findings highlight an important role for cyclic mechanical loading preconditioning of donor MDSCs in optimizing MDSC transplantation for myocardial repair. © 2012, Mary Ann Liebert, Inc

Lineage-specific gene radiations underlie the evolution of novel betalain pigmentation in Caryophyllales.

Betalain pigments are unique to the Caryophyllales and structurally and biosynthetically distinct from anthocyanins. Two key enzymes within the betalain synthesis pathway have been identified: 4,5-dioxygenase (DODA) that catalyzes the formation of betalamic acid and CYP76AD1, a cytochrome P450 gene that catalyzes the formation of cyclo-DOPA. We performed phylogenetic analyses to reveal the evolutionary history of the DODA and CYP76AD1 lineages and in the context of an ancestral reconstruction of pigment states we explored the evolution of these genes in relation to the complex evolution of pigments in Caryophylalles. Duplications within the CYP76AD1 and DODA lineages arose just before the origin of betalain pigmentation in the core Caryophyllales. The duplications gave rise to DODA-α and CYP76AD1-α isoforms that appear specific to betalain synthesis. Both betalain-specific isoforms were then lost or downregulated in the anthocyanic Molluginaceae and Caryophyllaceae. Our findings suggest a single origin of the betalain synthesis pathway, with neofunctionalization following gene duplications in the CYP76AD1 and DODA lineages. Loss of DODA-α and CYP76AD1-α in anthocyanic taxa suggests that betalain pigmentation has been lost twice in Caryophyllales, and exclusion of betalain pigments from anthocyanic taxa is mediated through gene loss or downregulation. [Correction added after online publication 13 May 2015: in the last two paragraphs of the Summary the gene name CYP761A was changed to CYP76AD1.].S.C. was supported by a grant to IRRI from the Bill and Melinda Gates Foundation and UKAID. This work was supported by a National Science Foundation award (grant numbers DEB 1354048 and DEB 1352907) to S.F.B., M.J.M. and S.A.S., and a NERC Independent Research Fellowship to S.F.B. The 1000 Plants (1KP) initiative, led by G.K.S.W., is funded by the Alberta Ministry of Enterprise and Advanced Education, Alberta Innovates Technology Futures (AITF), Innovates Centre of Research Excellence (iCORE), Musea Ventures and BGI-Shenzhen.This is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.1111/nph.1344

Overview of Phobos/Deimos Regolith Ion Sample Mission (PRISM) Concept

Far more definitive information on composition is required to resolve the question of origin for the Martian moons Phobos and Deimos. Current infrared spectra of the objects are inconclusive due to the lack of strong diagnostic features.Definitive compositional measurements of Phobos could be obtained using in-situ X-ray, gamma-ray, or neutronspectroscopy or collecting and returning samples to Earth for analysis. We have proposed, in lieu of those methods, toderive Phobos and Deimos compositional data from secondary ion mass spectrometry (SIMS) measurements by calibratingthe instrument to elemental abundance measurements made for known samples in the laboratory. We describe thePhobos/Deimos Regolith Ion Sample Mission (PRISM) concept here. PRISM utilizes a high-resolution TOF plasma composition analyzer to make SIMS measurements by observing the sputtered species from various locations of the moons' surfaces. In general, the SIMS technique and ion mass spectrometers complement and expand quadrupole mass spectrometer measurements by collecting ions that have been energized to higher energies, 50-100 eV, and making measurements at very low densities and pressures. Furthermore, because the TOF technique accepts all masses all the time,it obtains continuous measurements and does not require stepping through masses. The instrument would draw less than10 W and weigh less than 5 kg. The spacecraft, nominally a radiation-hardened 12U CubeSat, would use a low-thrust SolarElectric Propulsion system to send it on a two-year journey to Mars, where it would co-orbit with Deimos and then Phobo

The Cul3–KLHL21 E3 ubiquitin ligase targets Aurora B to midzone microtubules in anaphase and is required for cytokinesis

Selective ubiquitination of Aurora B by different Cul3 adaptors targets it at the correct time to the correct place during mitosis

International meta-analysis of PTSD genome-wide association studies identifies sex- and ancestry-specific genetic risk loci.

The risk of posttraumatic stress disorder (PTSD) following trauma is heritable, but robust common variants have yet to be identified. In a multi-ethnic cohort including over 30,000 PTSD cases and 170,000 controls we conduct a genome-wide association study of PTSD. We demonstrate SNP-based heritability estimates of 5-20%, varying by sex. Three genome-wide significant loci are identified, 2 in European and 1 in African-ancestry analyses. Analyses stratified by sex implicate 3 additional loci in men. Along with other novel genes and non-coding RNAs, a Parkinson's disease gene involved in dopamine regulation, PARK2, is associated with PTSD. Finally, we demonstrate that polygenic risk for PTSD is significantly predictive of re-experiencing symptoms in the Million Veteran Program dataset, although specific loci did not replicate. These results demonstrate the role of genetic variation in the biology of risk for PTSD and highlight the necessity of conducting sex-stratified analyses and expanding GWAS beyond European ancestry populations