Accurate masses and radii of normal stars: modern results and applications

This paper presents and discusses a critical compilation of accurate, fundamental determinations of stellar masses and radii. We have identified 95 detached binary systems containing 190 stars (94 eclipsing systems, and alpha Centauri) that satisfy our criterion that the mass and radius of both stars be known to 3% or better. To these we add interstellar reddening, effective temperature, metal abundance, rotational velocity and apsidal motion determinations when available, and we compute a number of other physical parameters, notably luminosity and distance. We discuss the use of this information for testing models of stellar evolution. The amount and quality of the data also allow us to analyse the tidal evolution of the systems in considerable depth, testing prescriptions of rotational synchronisation and orbital circularisation in greater detail than possible before. The new data also enable us to derive empirical calibrations of M and R for single (post-) main-sequence stars above 0.6 M(Sun). Simple, polynomial functions of T(eff), log g and [Fe/H] yield M and R with errors of 6% and 3%, respectively. Excellent agreement is found with independent determinations for host stars of transiting extrasolar planets, and good agreement with determinations of M and R from stellar models as constrained by trigonometric parallaxes and spectroscopic values of T(eff) and [Fe/H]. Finally, we list a set of 23 interferometric binaries with masses known to better than 3%, but without fundamental radius determinations (except alpha Aur). We discuss the prospects for improving these and other stellar parameters in the near future.Comment: 56 pages including figures and tables. To appear in The Astronomy and Astrophysics Review. Ascii versions of the tables will appear in the online version of the articl

An Integration of Genome-Wide Association Study and Gene Expression Profiling to Prioritize the Discovery of Novel Susceptibility Loci for Osteoporosis-Related Traits

Osteoporosis is a complex disorder and commonly leads to fractures in elderly persons. Genome-wide association studies (GWAS) have become an unbiased approach to identify variations in the genome that potentially affect health. However, the genetic variants identified so far only explain a small proportion of the heritability for complex traits. Due to the modest genetic effect size and inadequate power, true association signals may not be revealed based on a stringent genome-wide significance threshold. Here, we take advantage of SNP and transcript arrays and integrate GWAS and expression signature profiling relevant to the skeletal system in cellular and animal models to prioritize the discovery of novel candidate genes for osteoporosis-related traits, including bone mineral density (BMD) at the lumbar spine (LS) and femoral neck (FN), as well as geometric indices of the hip (femoral neck-shaft angle, NSA; femoral neck length, NL; and narrow-neck width, NW). A two-stage meta-analysis of GWAS from 7,633 Caucasian women and 3,657 men, revealed three novel loci associated with osteoporosis-related traits, including chromosome 1p13.2 (RAP1A, p = 3.6×10−8), 2q11.2 (TBC1D8), and 18q11.2 (OSBPL1A), and confirmed a previously reported region near TNFRSF11B/OPG gene. We also prioritized 16 suggestive genome-wide significant candidate genes based on their potential involvement in skeletal metabolism. Among them, 3 candidate genes were associated with BMD in women. Notably, 2 out of these 3 genes (GPR177, p = 2.6×10−13; SOX6, p = 6.4×10−10) associated with BMD in women have been successfully replicated in a large-scale meta-analysis of BMD, but none of the non-prioritized candidates (associated with BMD) did. Our results support the concept of our prioritization strategy. In the absence of direct biological support for identified genes, we highlighted the efficiency of subsequent functional characterization using publicly available expression profiling relevant to the skeletal system in cellular or whole animal models to prioritize candidate genes for further functional validation

Immunolocalization an quantification of noncollagenous bone matrix proteins in methylmethacrylate-embedded adult human bone in combination with histomorphometry

The noncollagenous proteins (NCPs) in the bone matrix comprise growth factors with distinct cellular effects and a series of proteins with less clear biological actions. In order to understand the role of these proteins in bone metabolism and in bone diseases, it is crucial to determine their localization and quantity in normal and pathological bone. We have developed an immunohistochemical method to detect osteopontin, osteocalcin, bone sialoprotein, osteonectin, decorin, biglycan, and the growth factors transforming growth factor-β, insulin-like growth factor-I, and bone morphogenetic protein-2 both in bone matrix and in bone cells of adult human bone embedded in methylmethacrylate. Immunohistochemistry and standard bone histomorphometry in adjacent sections allows the localization of the proteins to metabolically active sites in bone. The protocol works with several fixatives and with bone specimens obtained and embedded to over 20 years ago. Most importantly, we developed a procedure to specifically stain the mineralized matrix green in combination with a red staining of the NCPs. Using digital image analysis it is possible to quantify the relative amounts of NCPs (μm2 NCP area/μm2 mineralized matrix area). Within one biopsy of normal bone cut at four different heights (at a distance of 100 μm), two adjacent sections were stained either for osteopontin or osteonectin. Thirty trabecular and 20 cortical microscopic fields were measured, and the NCP: mineralized matrix ratio was calculated, Stepwise analysis of the standard error of the mean of the NCP: mineralized matrix ratios showed that measuring about 50 microscopic fields is sufficient to obtain representative data with a small confidence interval. In conclusion, the present procedure enables to quantify NCPs and to relate their presence to metabolically active sites in bone. The quantification provides the opportunity to monitor differences in distribution (e.g., cortical vs. trabecular) and differences between normal and pathological conditions and to assess changes in matrix composition during treatment. This can be done by reanalyzing bone biopsies obtained in the past, e.g., during clinical trials. Therefore, the present technique will be a valuable tool for the study of noncollagenous bone matrix proteins in human bone.</p