The Evolution of Compact Binary Star Systems

We review the formation and evolution of compact binary stars consisting of white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Binary NSs and BHs are thought to be the primary astrophysical sources of gravitational waves (GWs) within the frequency band of ground-based detectors, while compact binaries of WDs are important sources of GWs at lower frequencies to be covered by space interferometers (LISA). Major uncertainties in the current understanding of properties of NSs and BHs most relevant to the GW studies are discussed, including the treatment of the natal kicks which compact stellar remnants acquire during the core collapse of massive stars and the common envelope phase of binary evolution. We discuss the coalescence rates of binary NSs and BHs and prospects for their detections, the formation and evolution of binary WDs and their observational manifestations. Special attention is given to AM CVn-stars -- compact binaries in which the Roche lobe is filled by another WD or a low-mass partially degenerate helium-star, as these stars are thought to be the best LISA verification binary GW sources.Comment: 105 pages, 18 figure

Conserved determinants of lentiviral genome dimerization

Abstract Background Retroviruses selectively package two copies of their unspliced genomes by what appears to be a dimerization-dependent RNA packaging mechanism. Dimerization of human immunodeficiency virus Type-1 (HIV-1) genomes is initiated by “kissing” interactions between GC-rich palindromic loop residues of a conserved hairpin (DIS), and is indirectly promoted by long-range base pairing between residues overlapping the gag start codon (AUG) and an upstream Unique 5′ element (U5). The DIS and U5:AUG structures are phylogenetically conserved among divergent retroviruses, suggesting conserved functions. However, some studies suggest that the DIS of HIV-2 does not participate in dimerization, and that U5:AUG pairing inhibits, rather than promotes, genome dimerization. We prepared RNAs corresponding to native and mutant forms of the 5′ leaders of HIV-1 (NL4-3 strain), HIV-2 (ROD strain), and two divergent strains of simian immunodeficiency virus (SIV; cpz-TAN1 and -US strains), and probed for potential roles of the DIS and U5:AUG base pairing on intrinsic and NC-dependent dimerization by mutagenesis, gel electrophoresis, and NMR spectroscopy. Results Dimeric forms of the native HIV-2 and SIV leaders were only detectable using running buffers that contained Mg2+, indicating that these dimers are more labile than that of the HIV-1 leader. Mutations designed to promote U5:AUG base pairing promoted dimerization of the HIV-2 and SIV RNAs, whereas mutations that prevented U5:AUG pairing inhibited dimerization. Chimeric HIV-2 and SIV leader RNAs containing the dimer-promoting loop of HIV-1 (DIS) exhibited HIV-1 leader-like dimerization properties, whereas an HIV-1NL4-3 mutant containing the SIVcpzTAN1 DIS loop behaved like the SIVcpzTAN1 leader. The cognate NC proteins exhibited varying abilities to promote dimerization of the retroviral leader RNAs, but none were able to convert labile dimers to non-labile dimers. Conclusions The finding that U5:AUG formation promotes dimerization of the full-length HIV-1, HIV-2, SIVcpzUS, and SIVcpzTAN1 5′ leaders suggests that these retroviruses utilize a common RNA structural switch mechanism to modulate function. Differences in native and NC-dependent dimerization propensity and lability are due to variations in the compositions of the DIS loop residues rather than other sequences within the leader RNAs. Although NC is a well-known RNA chaperone, its role in dimerization has the hallmarks of a classical riboswitch.http://deepblue.lib.umich.edu/bitstream/2027.42/113284/1/12977_2015_Article_209.pd

Consensus guidelines for the use and interpretation of angiogenesis assays

The formation of new blood vessels, or angiogenesis, is a complex process that plays important roles in growth and development, tissue and organ regeneration, as well as numerous pathological conditions. Angiogenesis undergoes multiple discrete steps that can be individually evaluated and quantified by a large number of bioassays. These independent assessments hold advantages but also have limitations. This article describes in vivo, ex vivo, and in vitro bioassays that are available for the evaluation of angiogenesis and highlights critical aspects that are relevant for their execution and proper interpretation. As such, this collaborative work is the first edition of consensus guidelines on angiogenesis bioassays to serve for current and future reference

Decreasing NF-κB Expression Enhances Odontoblastic Differentiation and Collagen Expression in Dental Pulp Stem Cells Exposed to Inflammatory Cytokines

Inflammatory response in the dental pulp can alter the collagen matrix formation by dental pulp stem cells and lead to a delay or poor healing of the pulp. This inflammatory response is mediated by cytokines, including interleukin-1β and tumor necrosis factor-α. In this study, it is hypothesized that suppressing the actions of these inflammatory cytokines by knocking down the activity of transcription factor Nuclear Factor–κB will lead to dental pulp stem cell differentiation into odontoblasts and the production of collagen. Here, the role of Nuclear Factor–κB signaling and its reduction was examined during odontogenic behavior in the presence of these cytokines. The results showed a significant increase in Nuclear Factor–κB gene expression and p65 protein expression by interleukin-1β and tumor necrosis factor-α. Nuclear Factor–κB activation in the presence of these cytokines decreased significantly in a dose-dependent manner by a Nuclear Factor–κB inhibitor (MG132) and p65 siRNA. Down-regulation of Nuclear Factor–κB activity also enhanced the gene expression of the odontoblastic markers (dentin sialophosphoprotein, Nestin, and alkaline phosphatase) and displayed an odontoblastic cell morphology indicating the promotion of odontogenic differentiation of dental pulp stem cells. Finally, dental pulp stem cells exposed to reduced Nuclear Factor–κB activity resulted in a significant increase in collagen (I)-α1 expression in the presence of these cytokines. In conclusion, a decrease in Nuclear Factor-κB in dental pulp stem cells in the presence of inflammatory cytokines enhanced odontoblastic differentiation and collagen matrix formation.The open access fee for this work was funded through the Texas A&M University Open Access to Knowledge (OAK) Fund