Identification of Novel Loci Associated with Gastrointestinal Parasite Resistance in a Red Maasai x Dorper Backcross Population

Gastrointestinal (GI) parasitic infection is the main health constraint for small ruminant production, causing loss of weight and/or death. Red Maasai sheep have adapted to a tropical environment where extreme parasite exposure is a constant, especially with highly pathogenic Haemonchus contortus. This breed has been reported to be resistant to gastrointestinal parasite infection, hence it is considered an invaluable resource to study associations between host genetics and resistance. The aim of this study was to identify polymorphisms strongly associated with host resistance in a double backcross population derived from Red Maasai and Dorper sheep using a SNP-based GWAS analysis. The animals that were genotyped represented the most resistant and susceptible individuals based on the tails of phenotypic distribution (10% each) for average faecal egg counts (AVFEC). AVFEC, packed cell volume (AVPCV), and live weight (AVLWT) were adjusted for fixed effects and co-variables, and an association analysis was run using EMMAX. Revised significance levels were calculated using 100,000 permutation tests. The top five significant SNP markers with - log10 p-values >3.794 were observed on five different chromosomes for AVFEC, and BLUPPf90/PostGSf90 results confirmed EMMAX significant regions for this trait. One of these regions included a cluster of significant SNP on chromosome (Chr) 6 not in linkage disequilibrium to each other. This genomic location contains annotated genes involved in cytokine signalling, haemostasis and mucus biosynthesis. Only one association detected on Chr 7 was significant for both AVPCV and AVLWT. The results generated here reveal candidate immune variants for genes involved in differential response to infection and provide additional SNP marker information that has potential to aid selection of resistance to gastrointestinal parasites in sheep of a similar genetic background to the double backcross population.     

The effects of pH, buffers, and fatty acid concentration on the incorporation of radioactive arachidonate into endogenous neuronal nuclear lipids

Using neuronal nuclei (N1) isolated from cerebral cortices of 15-day-old rabbits the incorporation of [3H]arachidonate into N1 lipids was followed in vitro. Arachidonate was principally incorporated into triacylglycerol and phosphatidylinositol. When low concentrations (32 mM) of Tris-HC1 (pH 7.4) were used, rates of total arachidonate incorporation were small and phosphatidylinositol received the bulk (greater than 84%) of the arachidonate. When the concentration of Tris-HC1 (pH 7.4) or, in certain cases, the concentration of arachidonate was increased, there was a rise in total arachidonate incorporation into N1, with an increasing proportion of radioactivity entering triacylglycerol until it was the predominantly labelled lipid. Using other buffers (phosphate, imidazole, HEPES, pH 7.4), the shift from phosphatidylinositol to triacylglycerol as principal labelled lipid, with buffer concentration, was not as marked as with Tris-HC1 (pH 7.4). When the buffer concentration was maintained at 107 mM and the pH was lowered to 6.5, the three amine-containing buffers showed a sizeable decline in arachidonate incorporation into N1 lipids and a corresponding decrease in triacylglycerol labelling. The proportion of the total radioactivity in N1 phosphatidylinositol rose as the pH declined. Of the buffers used, Tris-HC1 showed the greatest changes over the pH range. Based upon pK values for the amine buffers, it is suggested that an increased proportion of the protonated amine may be inhibitory to arachidonate incorporation in N1. Studies of acyl-CoA synthetase in N1 indicated this enzyme as the site of the inhibition.     

Quantitative Assay for Genus-Specific Leptospiral Antigen and Antibody

Hemagglutination and hemagglutination inhibition techniques have been developed as quantitative assays for the genus-specific antigen of Leptospira and for its antibody.     

Trophic control of lung development by sympathetic neurons: effects of neonatal sympathectomy with 6-hydroxydopamine

The onset of peripheral sympathetic neuronal function is thought to provide trophic regulatory signals for development of adrenergic target tissues. In the current study, we examined the effects on lung development of neonatal sympathectomy with 6-hydroxydopamine. The completeness of the lesion and effectiveness in reducing sympathetic input to the tissue were confirmed by direct measurement of norepinephrine levels and turnover. Despite the denervation, no evidence of beta-receptor up-regulation was found; in fact, receptor binding sites tended to be reduced throughout development. The cyclic AMP response to isoproterenol challenge was initially suppressed in the lesioned animals, but became supersensitive even in the face of reduced receptor binding capabilities. Evidence was also obtained for ontogenetic abnormalities in the ornithine decarboxylase/polyamine system, which is partially controlled by beta-adrenergic input and which regulates macromolecule synthesis in replicating and differentiating cells. Eventually, the alterations were reflected in aberrant developmental patterns of DNA, RNA and protein in the lung. These results indicate that sympathetic neurons influence the biochemical development of the lung and may serve to program permanently the relationships among receptor sites, receptor coupling to cellular function, and control of cell maturation.