Pattern of epithelial cell cycling in hydra

We have investigated the spatial pattern of epithelial cell cycling in a mutant strain of Hydra magnipapillata (sf-1). This strain has temperature sensitive interstitial stem cells and thus polyps containing only epithelial cells can be obtained by growth at the restrictive temperature. Epithelial animals were pulse labeled with the thymidine analog 5′-bromo-2′-deoxyuridine (Brdu) and stained with anti-Brdu antibody to visualize S phase cells. Our results indicate that Brdu-labeled cells are broadly and fairly evenly distributed along the body column. Feeding stimulates a rapid decrease and then an increase in labeled cells in gastric tissue; labeled cells in the head are not affected. Starvation leads to a twofold decrease in labeled cells in the gastric region; the density of labeled cells in head tissue remains similar to that in well-fed animals. During bud formation the number of labeled epithelial cells increases significantly in the evaginating bud. During head regeneration the number of labeled cells declines sharply during the first 12 hr and then increases to a density typical of head tissue by 24–36 hr of regeneration. The results indicate the release of signals by feeding and regeneration which inhibit mitosis. By contrast head tissue and developing buds express signals stimulating mitosis. Thus changes in epithelial cell cycling in hydra are closely correlated with morphogenetic events as well as with feeding stimuli

Differences in protein mobility between pioneer versus follower growth cones

Navigating growth cones need to integrate, process and respond to guidance signals, requiring dynamic information transfer within and between different compartments. Studies have shown that, faced with different navigation challenges, growth cones display dynamic changes in growth kinetics and morphologies. However, it remains unknown whether these are paralleled by differences in their internal molecular dynamics. To examine whether there are protein mobility differences during guidance, we developed multiphoton fluorescence recovery after photobleaching methods to determine molecular diffusion rates in pathfinding growth cones in vivo. Actively navigating growth cones (leaders) have consistently longer recovery times than growth cones that are fasciculated and less actively navigating (followers). Pharmacological perturbations of the cytoskeleton point to actin as the primary modulator of diffusion in differently behaving growth cones. This approach provides a powerful means to quantify mobility of specific proteins in neurons in vivo and reveals that diffusion is important during axon navigation

Possible changes of state and relevant timescales for a neutron star in LS I +61{\deg}303

The properties of the short, energetic bursts recently observed from the gamma-ray binary LS I +61{\deg}303, are typical of those showed by high magnetic field neutron stars, and thus provide a strong indication in favor of a neutron star being the compact object in the system. Here, we discuss the transitions among the states accessible to a neutron star in a system like LS I +61{\deg}303, such as the ejector, propeller and accretor phases, depending on the NS spin period, magnetic field and rate of mass captured. We show how the observed bolometric luminosity (>= few x 1E35 erg/s), and its broad-band spectral distribution, indicate that the compact object is most probably close to the transition between working as an ejector all along its orbit, and being powered by the propeller effect when it is close to the orbit periastron, in a so-called flip-flop state. By assessing the torques acting onto the compact object in the various states, we follow the spin evolution of the system, evaluating the time spent by the system in each of them. Even taking into account the constraint set by the observed gamma-ray luminosity, we found that the total age of the system is compatible with being ~5-10 kyr, comparable to the typical spin-down ages of high-field neutron stars. The results obtained are discussed in the context of the various evolutionary stages expected for a neutron star with a high mass companion.Comment: 12 pages, 6 figures. Accepted for publication in Ap

Cold heteromolecular dipolar collisions

We present the first experimental observation of cold collisions between two different species of neutral polar molecules, each prepared in a single internal quantum state. Combining for the first time the techniques of Stark deceleration, magnetic trapping, and cryogenic buffer gas cooling allows the enhancement of molecular interaction time by 10$^5$. This has enabled an absolute measurement of the total trap loss cross sections between OH and ND$_3$ at a mean collision energy of 3.6 cm$^{-1}$ (5 K). Due to the dipolar interaction, the total cross section increases upon application of an external polarizing electric field. Cross sections computed from \emph{ab initio} potential energy surfaces are in excellent agreement with the measured value at zero external electric field. The theory presented here represents the first such analysis of collisions between a $^2\Pi$ radical and a closed-shell polyatomic molecule.Comment: 7 pages, 5 figure

Monarch: Self-expression through wearable kinetic textiles

Monarch is a wearable and muscle-activated kinetic textile. It consists of textile forms attached to the shoulders that expand and contract in response to the movement of the wearer's muscles. By physically extending natural body language, Monarch explores how wearable technologies can be used as a form of personal expression, as well as how and when they can begin to feel like a visceral extension of self

Second Human Case of Cache Valley Virus Disease

We document the second known case of Cache Valley virus disease in a human. Cache Valley virus disease is rarely diagnosed in North America, in part because laboratories rarely test for it. Its true incidence, effect on public health, and full clinical spectrum remain to be determined

Live Imaging at the Onset of Cortical Neurogenesis Reveals Differential Appearance of the Neuronal Phenotype in Apical versus Basal Progenitor Progeny

The neurons of the mammalian brain are generated by progenitors dividing either at the apical surface of the ventricular zone (neuroepithelial and radial glial cells, collectively referred to as apical progenitors) or at its basal side (basal progenitors, also called intermediate progenitors). For apical progenitors, the orientation of the cleavage plane relative to their apical-basal axis is thought to be of critical importance for the fate of the daughter cells. For basal progenitors, the relationship between cell polarity, cleavage plane orientation and the fate of daughter cells is unknown. Here, we have investigated these issues at the very onset of cortical neurogenesis. To directly observe the generation of neurons from apical and basal progenitors, we established a novel transgenic mouse line in which membrane GFP is expressed from the beta-III-tubulin promoter, an early pan-neuronal marker, and crossed this line with a previously described knock-in line in which nuclear GFP is expressed from the Tis21 promoter, a pan-neurogenic progenitor marker. Mitotic Tis21-positive basal progenitors nearly always divided symmetrically, generating two neurons, but, in contrast to symmetrically dividing apical progenitors, lacked apical-basal polarity and showed a nearly randomized cleavage plane orientation. Moreover, the appearance of beta-III-tubulin–driven GFP fluorescence in basal progenitor-derived neurons, in contrast to that in apical progenitor-derived neurons, was so rapid that it suggested the initiation of the neuronal phenotype already in the progenitor. Our observations imply that (i) the loss of apical-basal polarity restricts neuronal progenitors to the symmetric mode of cell division, and that (ii) basal progenitors initiate the expression of neuronal phenotype already before mitosis, in contrast to apical progenitors