Cytoskeletal turnover and Myosin contractility drive cell autonomous oscillations in a model of Drosophila Dorsal Closure

Oscillatory behaviour in force-generating systems is a pervasive phenomenon in cell biology. In this work, we investigate how oscillations in the actomyosin cytoskeleton drive cell shape changes during the process of Dorsal Closure, a morphogenetic event in Drosophila embryo development whereby epidermal continuity is generated through the pulsatile apical area reduction of cells constituting the amnioserosa (AS) tissue. We present a theoretical model of AS cell dynamics by which the oscillatory behaviour arises due to a coupling between active Myosin-driven forces, actin turnover and cell deformation. Oscillations in our model are cell-autonomous and are modulated by neighbour coupling, and our model accurately reproduces the oscillatory dynamics of AS cells and their amplitude and frequency evolution. A key prediction arising from our model is that the rate of actin turnover and Myosin contractile force must increase during DC in order to reproduce the decrease in amplitude and period of cell area oscillations observed in vivo. This prediction opens up new ways to think about the molecular underpinnings of AS cell oscillations and their link to net tissue contraction and suggests the form of future experimental measurements.Comment: 17 pages, 6 figures; added references, modified and corrected Figs. 1 and 3, corrected typos, expanded discussio

Direct determination of the crystal field parameters of Dy, Er and Yb impurities in the skutterudite compound CeFe4_{4}P12_{12} by Electron Spin Resonance

Despite extensive research on the skutterudites for the last decade, their electric crystalline field ground state is still a matter of controversy. We show that Electron Spin Resonance (ESR) measurements can determine the full set of crystal field parameters (CFPs) for the Th cubic symmetry (Im3) of the Ce$_{1-x}$R$_{x}$Fe$_{4}$P$_{12}$ (R = Dy, Er, Yb, $x\lesssim 0.003$) skutterudite compounds. From the analysis of the ESR data the three CFPs, B4c, B6c and B6t were determined for each of these rare-earths at the Ce$^{3+}$ site. The field and temperature dependence of the measured magnetization for the doped crystals are in excellent agreement with the one predicted by the CFPs Bnm derived from ESR.Comment: 7 pages, 5 figures, to appear in PR

Listeria monocytogenes Inhibits Serotonin Transporter in Human Intestinal Caco-2 Ce

Listeria monocytogenes is a Gram-positive bacterium that can cause a serious infection. Intestinal microorganisms have been demonstrated to contribute to intestinal physiology not only through immunological responses but also by modulating the intestinal serotonergic system. Serotonin (5- HT) is a neuromodulator that is synthesized in the intestinal epithelium and regulates the whole intestinal physiology. The serotonin transporter (SERT), located in enterocytes, controls intestinal 5-HT availability and therefore serotonin’s effects. Infections caused by L. monocytogenes are well described as being due to the invasion of intestinal epithelial cells; however, the effect of L. monocytogenes on the intestinal epithelium remains unknown. The main aim of this work, therefore, was to study the effect of L. monocytogenes on SERT. Caco2/TC7 cell line was used as an enterocyte-like in vitro model, and SERT functional and molecular expression assays were performed. Our results demonstrate that living L. monocytogenes inhibits serotonin uptake by reducing SERT expression at the brush border membrane. However, neither inactivated L. monocytogenes nor soluble metabolites were able to affect SERT. The results also demonstrate that L. monocytogenes yields TLR2 and TLR10 transcriptional changes in intestinal epithelial cells and suggest that TLR10 is potentially involved in the inhibitory effect observed on SERT. Therefore, L. monocytogenes, through TLR10-mediated SERT inhibition, may induce increased intestinal serotonin availability and potentially contributing to intestinal physiological changes and the initiation of the inflammatory response.This work was funded by grants from the Spanish Ministry of Science and Innovation and the European Regional Development Fund (ERDF/FEDER) (BFU2010-18971), Zaragoza University (UZ2014- BIO-03), European Social Found (ESF), and the Aragon Regional Government (B61) and the Foundation for the Study of Inflammatory Bowel Diseases in Aragón (ARAINF 2012/0567). E. Latorre and E. Layunta are PhD student fellows from Aragon Regional Government (B105/11 and B022/13)

Memory decline evolves independently of disease activity in MS

The natural history of cognitive impairment in multiple sclerosis (MS) and its relationship with disease activity is not well known. In this study, we evaluate a prospective cohort of 44 MS patients who were followed every 3 months for 2 years. Cognitive evaluation was done at baseline and by the end of the study using the Brief Repeatable Battery-Neuropsychology. Clinical evaluation included assessment of new relapses and changes in disability (Extended Disability Status Scale (EDSS)) confirmed at 6 months. RESULTS: We found that verbal memory performance deteriorates after 2 years in patients with MS. These changes were observed in stable and active patients both in terms of relapses and disability progression, even at the beginning of the disease, and in patients with or without cognitive impairment at study entry. Attention and executive functions measured with the symbol digit modality test (SDMT) declined after 2 years in patients with confirmed disability progression. Furthermore, SDMT performance correlated with the EDSS change. CONCLUSIONS: Our findings indicate that verbal memory steadily declines in patients with MS from the beginning of the disease and independently of other parameters of disease activity

Neutrino masses in SU(5)×U(1)FSU(5)\times U(1)_F with adjoint flavons

We present a $SU(5)\times U(1)_F$ supersymmetric model for neutrino masses and mixings that implements the seesaw mechanism by means of the heavy SU(2) singlets and triplets states contained in three adjoints of SU(5). We discuss how Abelian $U(1)_F$ symmetries can naturally yield non-hierarchical light neutrinos even when the heavy states are strongly hierarchical, and how it can also ensure that $R$--parity arises as an exact accidental symmetry. By assigning two flavons that break $U(1)_F$ to the adjoint representation of SU(5) and assuming universality for all the fundamental couplings, the coefficients of the effective Yukawa and Majorana mass operators become calculable in terms of group theoretical quantities. There is a single free parameter in the model, however, at leading order the structure of the light neutrinos mass matrix is determined in a parameter independent way.Comment: 16 pages, 9 figures. Included contributions to neutrino masses from the triplet states contained in the three adjoints of SU(5

La transmisión de virus no persistentes estudiada a través del comportamiento de prueba de pulgones

Cinco años de investigación sobre el comportamiento de prueba del pulgón Myzus persicae Sulzer con la ayuda de un monitor electrónico de comportamiento (técnica EPG) han permitido obtener un mejor conocimiento sobre el mecanismo de transmisión no persistente de virus vegetales, empleando como modelo el virus Y de la patata (PVY). Las breves picaduras intracelulares producidas por el pulgón al inicio de la prueba son registradas en el monitor electrónico como breves caídas de potencial (denominadas pds). La presencia y morfología de este patrón de onda pd ha resultado ser clave en el proceso de tranmisión de PVY. Se ha observado que la presencia de al menos una pd es necesaria para la adquisición del virus, y que una mayor frecuencia de pds aumenta la probabilidad de adquisición. Asimismo, se ha comprobado que el proceso de inoculación del virus también tiene lugar durante la pd, más en concreto en su fase inicial III, mientras que la adquisición es un proceso posterior (fase 113). Esta evidencia pone en duda el mecanismo mayoritariamente aceptado de ingestión-egestión, proponiéndose como hipótesis alternativa un mecanismo de ingestión-salivación. Asimismo, la presencia y morfología de la fase 113 de la pd ha proporcionado una explicación satisfactoria al conocido efecto del ayuno previo (que aumenta la eficiencia de transmisión) y a la distinta capacidad vectorial observada en diferentes especies de pulgone

Building Babies - Chapter 16

In contrast to birds, male mammals rarely help to raise the offspring. Of all mammals, only among rodents, carnivores, and primates, males are sometimes intensively engaged in providing infant care (Kleiman and Malcolm 1981). Male caretaking of infants has long been recognized in nonhuman primates (Itani 1959). Given that infant care behavior can have a positive effect on the infant’s development, growth, well-being, or survival, why are male mammals not more frequently involved in “building babies”? We begin the chapter defining a few relevant terms and introducing the theory and hypotheses that have historically addressed the evolution of paternal care. We then review empirical findings on male care among primate taxa, before focusing, in the final section, on our own work on paternal care in South American owl monkeys (Aotus spp.). We conclude the chapter with some suggestions for future studies.Deutsche Forschungsgemeinschaft (HU 1746/2-1) Wenner-Gren Foundation, the L.S.B. Leakey Foundation, the National Geographic Society, the National Science Foundation (BCS-0621020), the University of Pennsylvania Research Foundation, the Zoological Society of San Dieg