Sensitivity of methods for estimating breeding values using genetic markers to the number of QTL and distribution of QTL variance

The objective of this simulation study was to compare the effect of the number of QTL and distribution of QTL variance on the accuracy of breeding values estimated with genomewide markers (MEBV). Three distinct methods were used to calculate MEBV: a Bayesian Method (BM), Least Angle Regression (LARS) and Partial Least Square Regression (PLSR). The accuracy of MEBV calculated with BM and LARS decreased when the number of simulated QTL increased. The accuracy decreased more when QTL had different variance values than when all QTL had an equal variance. The accuracy of MEBV calculated with PLSR was affected neither by the number of QTL nor by the distribution of QTL variance. Additional simulations and analyses showed that these conclusions were not affected by the number of individuals in the training population, by the number of markers and by the heritability of the trait. Results of this study show that the effect of the number of QTL and distribution of QTL variance on the accuracy of MEBV depends on the method that is used to calculate MEBV.     

Effect of exogenous circulating anti-bPL antibodies on bovine placental lactogen measurements in foetal samples

Background  

The involvement of placental lactogen (PL) in the regulation of foetal growth has been investigated in different species by in vivo immunomodulation techniques. However, when circulating antibodies are present together with the hormone, the procedure for hormonal measurement becomes considerably complex. The aim of this study was the immunoneutralization of bovine placental lactogen (bPL) concentrations in bovine foetal circulation by direct infusion of rabbit anti-bPL purified immunoglobulins (IgG) via a foetal catheter (in vivo study). The ability of a RIA based on guinea pig anti-bPL antiserum, for the measurement of bPL concentrations in samples containing exogenous rabbit anti-bPL immunoglobulins, was also analyzed in in vitro and in vivo conditions.     

Excluding blood donors at high risk of HIV infection in a west African city.

OBJECTIVE--To examine the potential impact of deferral of blood donors at high risk of HIV infection in a west African city where blood is screened for HIV antibodies but no other special measures are taken to protect the blood supply. DESIGN--Cross sectional study. SETTING--National Blood Transfusion Centre and Project RETRO-CI, an international collaborative AIDS research project, Abidjan, Côte d''Ivoire. SUBJECTS--1257 male first time blood donors. INTERVENTIONS--Blood donors were interviewed about demographic and behavioural characteristics and tested for HIV antibodies by enzyme immunoassay and, if positive, synthetic peptide based tests. MAIN OUTCOME MEASURES--HIV antibody status in relation to presence of behavioural risk factors; calculation of sensitivity, specificity, and predictive values of specific criteria for excluding HIV infected donors. RESULTS--The overall prevalence of HIV infection was 11.4%. The most important risk factors for HIV positivity were prostitute contact and being aged 30-39 years. For identifying seropositive donors individual criteria had sensitivity, specificity, and positive predictive values ranging from 15% to 98%, 38% to 91%, and 17% to 30% respectively. Prostitute contact in the past five years would have excluded 31% of all donors and 73% of HIV infected donors. 27% of those excluded would have been HIV positive. CONCLUSIONS--The widespread assumption that donor deferral is not feasible in sub-Saharan Africa needs reassessment. In Abidjan this approach was well accepted and potentially effective. Donor deferral requires evaluation as a strategy for improving blood safety in resource poor areas with high rates of HIV infection.     

Contribution of tuberculosis to slim disease in Africa.

OBJECTIVES--To assess the contribution of tuberculosis to the aetiology of the HIV wasting syndrome (slim) in Africa, a condition usually considered an enteropathy. METHODS--Clinical examination and representative necropsy study of adult patients positive for HIV. SETTING--Hospital medical wards in Abidjan, Ivory Coast. SUBJECTS--Adults positive for HIV. MAIN OUTCOME MEASURES--CD4 T lymphocyte counts before death, clinical and anthropometric data, and gross and microscopic pathology. RESULTS--Necropsy was done on 212 HIV positive adults. Tuberculosis was found in 41 of 93 with the clinical HIV wasting syndrome and in 32 of 119 without (odds ratio 2.1, 95% confidence interval 1.2 to 4.0). A significant association existed between the prevalence of tuberculosis at necropsy and the degree of cadaveric wasting (no wasting 25% (15/59); moderate wasting 40% (23/58); skeletal wasting 44% (42/95); P = 0.02). Wasting was also associated with a history of chronic diarrhoea, but no association existed between diarrhoea and tuberculosis. Median CD4 T lymphocyte counts were lowest in wasted patients irrespective of findings at necropsy and in those with chronic diarrhoea (< 60 x 10(6)/l). CONCLUSION--Wasting and chronic diarrhoea are late stage manifestations of HIV disease in Africa. The importance of tuberculosis as a contributing factor in the pathogenesis of the slim syndrome has been underestimated. In nearly half of patients dying with severe wasting, tuberculosis was the dominant pathological finding.     

The cost of ant attendance and melezitose secretion in the black bean aphid Aphis fabae

1. The aphid Aphis fabae (Scopoli) is facultatively tended by Lasius niger (Linnaeus) ants. Previously, we found that A. fabae colonies can be made up of several clones, and that clones display significant differences in the composition of their honeydew sugars, especially in the amount of the ant attractant sugar melezitose that they produce. 2. These clonal differences could greatly impact the strength of the mutualistic interaction with ants as well as the aphids' fitness. 3. Hence, the aim of this study was to compare the fitness of different A. fabae clones that differed in their melezitose secretion, and whether or not they were tended by ants. 4. Individual fitness indices, colony growth, and alate production of single‐clone aphid colonies were analysed. 5. The results demonstrate that the fitness consequences of ant attendance critically depend on an interaction between levels of melezitose production. In particular, we show that high‐melezitose secreting clones produce fewer alates and hence might have a lower dispersal ability in the presence of ants. 6. Furthermore, these data confirm previous evidence that ant attendance is costly and results in the production of fewer apterae.     

Long-term cleaning patterns of the sharknose goby (Elacatinus evelynae)

Coral Reefs - Cleaning interactions, which involve a cleaner removing ectoparasites and other material from the body of a heterospecific (client), are iconic symbiotic interactions observed on...