During DNA replication, the genetic information of a cell is copied. Subsequently, identical genetic information is segregated reliably to the two daughter cells through cell division. Meanwhile, DNA replication is intrinsically linked to the process of chromatin duplication, which is required for regulating gene expression and establishing cell identities. Understanding how chromatin is established, maintained or changed during DNA replication represents a fundamental question in biology. Recently, we developed a method to directly visualize chromatin components at individual replication forks undergoing DNA replication. This method builds upon the existing chromatin fiber technique and combines it with cell type-specific chromatin labeling and superresolution microscopy. In this method, a short pulse of nucleoside analog labels replicative regions in the cells of interest. Chromatin fibers are subsequently isolated and attached to a glass slide, after which a laminar flow of lysis buffer extends the lysed chromatin fibers parallel with the direction of the flow. Fibers are then immunostained for different chromatin-associated proteins and mounted for visualization using superresolution microscopy. Replication foci, or 'bubbles,' are identified by the presence of the incorporated nucleoside analog. For researchers experienced in molecular biology and superresolution microscopy, this protocol typically takes 2-3 d from sample preparation to data acquisition, with an additional day for data processing and quantification.

The synaptonemal complex (SC) is a tripartite protein scaffold that forms between homologous chromosomes during meiosis. Although the SC is essential for stable homologue pairing and crossover recombination in diverse eukaryotes, it is unknown how individual components assemble into the highly conserved SC structure. Here we report the biochemical identification of two new SC components, SYP-5 and SYP-6, in Caenorhabditis elegans. SYP-5 and SYP-6 are paralogous to each other and play redundant roles in synapsis, providing an explanation for why these genes have evaded previous genetic screens. Superresolution microscopy reveals that they localize between the chromosome axes and span the width of the SC in a head-to-head manner, similar to the orientation of other known transverse filament proteins. Using genetic redundancy and structure-function analyses to truncate C-terminal tails of SYP-5/6, we provide evidence supporting the role of SC in both limiting and promoting crossover formation.

Here we describe novel spherical structures that are induced by cold shock on the lampbrush chromosomes (LBCs) of Xenopus laevis oocytes. We call these structures cold bodies or C-bodies. C-bodies are distributed symmetrically on homologous LBCs, with a pattern similar to that of 5S rDNA. Neither active transcription nor translation is necessary for their formation. Similar protrusions occur on the edges of some nucleoli. Endogenous LBCs as well as those derived from injected sperm form C-bodies under cold shock conditions. The function of C-bodies is unknown.

The lampbrush chromosomes (LBCs) in oocytes of the Mexican axolotl (Ambystoma mexicanum) were identified some time ago by their relative lengths and predicted centromeres, but they have never been associated completely with the mitotic karyotype, linkage maps or genome assembly. We identified 9 of the axolotl LBCs using RNAseq to identify actively transcribed genes and 13 BAC (bacterial artificial clone) probes containing pieces of active genes. Using read coverage analysis to find candidate centromere sequences, we developed a centromere probe that localizes to all 14 centromeres. Measurements of relative LBC arm lengths and polymerase III localization patterns enabled us to identify all LBCs. This study presents a relatively simple and reliable way to identify each axolotl LBC cytologically and to anchor chromosome-length sequences (from the axolotl genome assembly) to the physical LBCs by immunostaining and fluorescence in situ hybridization. Our data will facilitate a more detailed transcription analysis of individual LBC loops.

In the seconds following their formation in core-collapse supernovae, "proto"-magnetars drive neutrino-heated magneto-centrifugal winds. Using a suite of two-dimensional axisymmetric MHD simulations, we show that relatively slowly rotating magnetars with initial spin periods of P-*0 = 50-500 ms spin down rapidly during the neutrino Kelvin-Helmholtz cooling epoch. These initial spin periods are representative of those inferred for normal Galactic pulsars, and much slower than those invoked for gamma-ray bursts and super-luminous supernovae. Since the flow is non-relativistic at early times, and because the Alfven radius is much larger than the proto-magnetar radius, spindown is millions of times more efficient than the typically-used dipole formula. Quasi-periodic plasmoid ejections from the closed zone enhance spindown. For polar magnetic field strengths B-0 greater than or similar to 5 x 10(14) G, the spindown timescale can be shorter than than the Kelvin-Helmholtz timescale. For B-0 greater than or similar to 10(15) G, it is of order seconds in early phases. We compute the spin evolution for cooling proto-magnetars as a function of B-0, P-*0, and mass (M). Proto-magnetars born with B-0 greater than similar or equal to 1.3 x 10(15)G(P-*0/400ms)(-1.4)(M/1.4M(circle dot))(2.2) spin down to periods >1 s in just the first few seconds of evolution, well before the end of the cooling epoch and the onset of classic dipole spindown. Spindown is more efficient for lower M and for larger P-*0. We discuss the implications for observed magnetars, including the discrepancy between their characteristic ages and supernova remnant ages. Finally, we speculate on the origin of 1E 161348-5055 in the remnant RCW 103, and the potential for other ultra-slowly rotating magnetars.

Several external hardware upgrades have been developed for the APOGEE Spectrographs as part of the Sloan Digital Sky Survey-V (SDSS-V) to improve their radial velocity (RV) precision from a floor of 100-200 m/sec to approx. 30 m/sec. The upgrades include: (1) Back Pressure Regulator (BPR) systems to stabilize the internal instrument LN2 tank boil-off pressure, lessening induced movement of the APOGEE optical bench; (2) Fabry-Perot Interferometer (FPI) calibration sources to improve wavelength calibration; and (3), the use of octagonal core fiber segments in the fiber train to improve radial scrambling. We discuss the fabrication, commissioning, and early performance of these upgrades.

The correlation between black hole masses and stellar velocity dispersions provides an efficient method to determine the masses of black holes in active galaxies. We obtained optical spectra of a Compact-Steep-Spectrum (CSS) galaxy 4C+29.70, using the Canada-France-Hawaii Telescope (CFHT) equipped with OSIS, in 2003 August 6. Several stellar absorption features, such as Mg I (5175 angstrom), Ca E band (5269 angstrom) and Na D (5890 angstrom), were detected in the spectra. The stellar velocity dispersion, sigma, of the host galaxy, measured from absorption features is approximate to 250 km s(-1). If 4C +29.70 follows the M-BH-sigma relation established for nearby galaxies, then its central black hole has a mass of approximate to 3.3 x 10(8) M-circle dot. In combination with the black hole masses of seven GPS galaxies in Snellen et al. (2003), we find that the average black hole mass of these eight young radio sources is smaller than that of the Bettoni et al. (2003) sample of extended radio galaxies. This may indicate that young radio sources are likely at the early evolutionary stage of radio galaxies, at which the central black holes may still undergo rapid growth. However, this needs further investigations. (C) 2009 WILEY-VCH Verlag GmbH & Co, KGaA, Weinheim

Minor mergers are thought to be important for the buildup and structural evolution of massive elliptical galaxies. In this work, we report the discovery of a system of four shell features in NGC 4889, one of the brightest members of the Coma cluster, using optical images taken with the Hubble Space Telescope and the Sloan Digital Sky Survey. The shells are well aligned with the major axis of the host and are likely to have been formed by the accretion of a small satellite galaxy. We have performed a detailed two-dimensional photometric decomposition of NGC 4889 and of the many overlapping nearby galaxies in its vicinity. This comprehensive model allows us not only to firmly detect the low-surface brightness shells, but, crucially, also to accurately measure their luminosities and colors. The shells are bluer than the underlying stars at the same radius in the main galaxy. We make use of the colors of the shells and the color-magnitude relation of the Coma cluster to infer the luminosity (or mass) of the progenitor galaxy. The shells in NGC 4889 appear to have been produced by the minor merger of a moderate-luminosity (M-I approximate to -18.7 mag) disk (S0 or spiral) galaxy with a luminosity (mass) ratio of similar to 90:1 with respect to the primary galaxy. The novel methodology presented in this work can be exploited to decode the fossil record imprinted in the photometric substructure of other nearby early-type galaxies.

Materials discovery enables both realization and understanding of new, exotic, physical phenomena. An emerging approach to the discovery of novel phases is high-pressure synthesis within diamond anvil cells, thereby enabling insitu monitoring of phase formation. Now, the discovery via high-pressure synthesis of the first intermetallic compound in the Cu-Pb system, Cu3Pb is reported. Cu3Pb is notably the first structurally characterized mid- to late-first-row transition-metal plumbide. The structure of Cu3Pb can be envisioned as a direct mixture of the two elemental lattices. From this new framework, we gain insight into the structure as a function of pressure and hypothesize that the high-pressure polymorph of lead is a possible prerequisite for the formation of Cu3Pb. Crucially, electronic structure computations reveal band crossings near the Fermi level, suggesting that chemically doped Cu3Pb could be a topologically nontrivial material.