A specificity-enhanced time-resolved fluoroimmunoassay for zeranol employing the dry reagent all-in-one-well principle

A simple dry chemistry time-resolved fluorescence immunoassay (TR-FIA) method was developed for the measurement of zeranol in bovine urine samples. The samples were purified by immunoaffinity chromatography and a specificity-enhanced zeranol antibody was employed in the immunoassay. This resulted in a highly selective method, which had only negligible reactivity with Fusarium spp, toxins. The all-in-one-well dry chemistry concept made the assay very simple to use because all the assay-specific reagents were already present in the reaction wells in dry form. Only the addition of diluted sample extract was required to perform the competitive one-step TR-FIA and the results were available in less than 1 h. The analytical limit of detection (mean + 3s) for the immunoassay was 0.16 ng ml(-1) (n=12) and the functional limit of detection for the whole method, estimated by the analysis of zeranol-free samples, was 1.3 ng ml(-1) (n=20). The recovery of zeranol at the level of 2 ng ml(-1) was 99% (n=18) and the within-assay variation ranged between 4.5 and 9.0%.

Comparison of two polyclonal antibodies for the detection of 19-nortestosterone in bovine bile by ELISA

19-Nortestosterone (beta-NT) is banned for use as a growth promoter in food animals within the European Union. For regulatory control purposes, urine and bile samples are routinely screened by immunoassay. The aim of the present study was to compare the ability of two immunoassays, using two rabbit polyclonal antibodies raised against two different NT derivatives, to detect NT residues in bovine bile. One antiserum cross-reacted with both alpha-NT and beta-NT (alpha/beta-NT), whereas the other was specific for alpha-NT. Bile samples from 266 slaughtered cattle were deconjugated and analyzed using both antibodies, with all screening positives (>2 ng ml(-1)) confirmed by high resolution gas chromatography mass spectrometry. The alpha/beta-NT and alpha-NT antibody-based ELISAs screened 39 and 44 samples positive, respectively, with NT confirmed in 22 and 39, respectively. The alpha/beta-NT antibody-based ELISA produced a false-negative rate of 44% compared to 0% for the alpha-NT antibody-based ELISA. Supplementary investigations concluded that a matrix effect was a major cause of the marked differences in false-negative rates. This result underlines the necessity to validate immunoassays in the sample matrix.

Common variants at the MHC locus and at chromosome 16q24.1 predispose to Barrett's esophagus

Barrett's esophagus is an increasingly common disease that is strongly associated with reflux of stomach acid and usually a hiatus hernia, and it strongly predisposes to esophageal adenocarcinoma (EAC), a tumor with a very poor prognosis. We report the first genome-wide association study on Barrett's esophagus, comprising 1,852 UK cases and 5,172 UK controls in the discovery stage and 5,986 cases and 12,825 controls in the replication stage. Variants at two loci were associated with disease risk: chromosome 6p21, rs9257809 (P(combined) = 4.09 × 10(-9); odds ratio (OR) = 1.21, 95% confidence interval (CI) =1.13-1.28), within the major histocompatibility complex locus, and chromosome 16q24, rs9936833 (P(combined) = 2.74 × 10(-10); OR = 1.14, 95% CI = 1.10-1.19), for which the closest protein-coding gene is FOXF1, which is implicated in esophageal development and structure. We found evidence that many common variants of small effect contribute to genetic susceptibility to Barrett's esophagus and that SNP alleles predisposing to obesity also increase risk for Barrett's esophagus.

Defining the role of common variation in the genomic and biological architecture of adult human height

Using genome-wide data from 253,288 individuals, we identified 697 variants at genome-wide significance that together explained one-fifth of the heritability for adult height. By testing different numbers of variants in independent studies, we show that the most strongly associated 1/42,000, 1/43,700 and 1/49,500 SNPs explained 1/421%, 1/424% and 1/429% of phenotypic variance. Furthermore, all common variants together captured 60% of heritability. The 697 variants clustered in 423 loci were enriched for genes, pathways and tissue types known to be involved in growth and together implicated genes and pathways not highlighted in earlier efforts, such as signaling by fibroblast growth factors, WNT/I 2-catenin and chondroitin sulfate-related genes. We identified several genes and pathways not previously connected with human skeletal growth, including mTOR, osteoglycin and binding of hyaluronic acid. Our results indicate a genetic architecture for human height that is characterized by a very large but finite number (thousands) of causal variants.