Associations of DNA polymorphisms in growth hormone and its transcriptional regulators with growth and carcass traits in two populations of Brangus bulls

Sequence polymorphisms in the growth hormone (GH) gene and its transcriptional regulators, Pit-1 and Prop-1, were evaluated for associations with growth and carcass traits in two populations of Brangus bulls Chihuahuan Desert Rangeland Research Center (CDRRC, N = 248 from 14 sires) and a cooperating breeding program (COOP, N = 186 from 34 sires). Polymorphisms were SNP mutations in intron 4 (C/T) and exon V (C/G) in GH, A/G in exon VI in Pit-1, and A/G in exon III in Prop-1. In the COOP population, bulls of Pit-1 GG genotype had a significantly greater percentage of intramuscular fat than bulls of the AA or AG genotype, and bulls of the Prop-1 AA genotype had significantly greater scrotal circumference than bulls of AG or GG genotypes at ~365 days of age. Also, heterozygous genotypes for the two GH polymorphisms appeared advantageous for traits of muscularity and adiposity in the COOP population. The heterozygous genotype of GH intron 4 SNP was associated with advantages in weight gain, scrotal circumference, and fat thickness in the CDRRC population. The two GH polymorphisms accounted for ³27.7% of the variation in these traits in the CDRRC population; however, R2 was <5% in the COOP population. Based on haplotype analyses the two GH SNPs appeared to be in phase; the haplotype analyses also paralleled with the genotype analyses. Polymorphisms in GH and its transcriptional regulators appear to be predictors of growth and carcass traits in Brangus bulls, particularly those with heterozygous GH genotypes

Medicion de los anticuerpos contra el virus de la inmunodeficiencia humana: estudio internacional en colaboración para evaluar los sueros de referencia de la OMS

Two preparations of human sera, one reactive against human immunodeficiency virus (HIV) and the other unreactive, were evaluated as potential international reference reagents (IRR) in an international collaborative study. Twenty-one laboratories participated and tested these and five other human sera which were found to range from highly reactive to unreactive. The proposed "positive" IRR was found to react strongly in all immunoassays and gave all the expected bands in immunoblot systems using HTLV-III, LAV-I or similar virus strains as antigens. The "unreactive" serum was judged to be negative by ELISA and immunoblots. The end-points determined by ELISAs varied considerably between laboratories, even between those using the same commercial kit. This variation was reduced somewhat when the reactivities of the samples were expressed relative to the proposed IRR