Do hyraxes benefit from human presence in Serengeti?

Understanding the factors affecting a species’ population size is crucial for conservation initiatives. Hyraxes are small, gregarious animals, predominantly found on kopjes (rock outcrops) and thus form metapopulation communities. In Tanzania, two species of hyraxes inhabit Serengeti National Park, the rock hyrax Procavia capensis johnstoni and bush hyrax Heterohyrax brucei. This study focuses on the factors that affect hyrax population size, including factors such as human presence, habitat type, kopje size and kopje height. We found that larger and taller kopjes tended to have more hyraxes than smaller ones, while kopjes in wooded grassland had more hyraxes than kopjes in grassland. Human presence often affects species negatively, but in the case of hyraxes, we found that kopjes with human presence had larger populations than kopjes without humans. We discuss possible explanations for this and suggest that human presence is related to fewer predators and higher food availability.     

A phenomics-based strategy identifies loci on APOC1, BRAP, and PLCG1 associated with metabolic syndrome phenotype domains

Despite evidence of the clustering of metabolic syndrome components, current approaches for identifying unifying genetic mechanisms typically evaluate clinical categories that do not provide adequate etiological information. Here, we used data from 19,486 European American and 6,287 African American Candidate Gene Association Resource Consortium participants to identify loci associated with the clustering of metabolic phenotypes. Six phenotype domains (atherogenic dyslipidemia, vascular dysfunction, vascular inflammation, pro-thrombotic state, central obesity, and elevated plasma glucose) encompassing 19 quantitative traits were examined. Principal components analysis was used to reduce the dimension of each domain such that >55% of the trait variance was represented within each domain. We then applied a statistically efficient and computational feasible multivariate approach that related eight principal components from the six domains to 250,000 imputed SNPs using an additive genetic model and including demographic covariates. In European Americans, we identified 606 genome-wide significant SNPs representing 19 loci. Many of these loci were associated with only one trait domain, were consistent with results in African Americans, and overlapped with published findings, for instance central obesity and FTO. However, our approach, which is applicable to any set of interval scale traits that is heritable and exhibits evidence of phenotypic clustering, identified three new loci in or near APOC1, BRAP, and PLCG1, which were associated with multiple phenotype domains. These pleiotropic loci may help characterize metabolic dysregulation and identify targets for intervention.     

Investigation of genetic risk factors for chronic adult diseases for association with preterm birth

Preterm birth (PTB) is the leading cause of infant mortality. PTB pathophysiology overlaps with those of adult cardiovascular, immune and metabolic disorders (CIMD), with mechanisms including inflammation, immunotolerance, thrombosis, and nutrient metabolism. Whereas many genetic factors for CIMD have been identified, progress in PTB has lagged. We hypothesized that highly validated genetic risk factors for CIMD may also be associated with PTB. We conducted case–control study of four female cohorts with spontaneous PTB (n = 673) versus term (n = 1119). Of 35 SNPs genotyped, there were 13 statistically significant associations (P < 0.05), which were more than expected (binomial test; P = 0.02). In US White (307 cases/342 controls), the G allele of HLA-DQA1 (A/G) rs9272346 was protective for PTB in the initial discovery cohort (P = 0.02; OR = 0.65; 95 % CI 0.46, 0.94). This protective association replicated (P = 0.02; OR = 0.85; 95 % CI 0.75, 0.97) nominally in the Danish Cohort (883 cases, 959 controls), but lost significance upon multiple testing correction. We observed more statistically significant associations than expected, suggesting that chance is an unlikely explanation for one or more of the associations. Particularly, a protective association of the G allele of HLA-DQA1 was found in two independent cohorts, and in previous studies, this same allele was found to protect against type-1-diabetes (meta-analysis P value 5.52 × 10^–219). Previous investigations have implicated HLA phenotypic variation in recurrent fetal loss and in chronic chorioamnionitis. Given the limited sample size in his study, we suggest larger studies to further investigate possible HLA genetic involvement in PTB.     

Multiple angiopoietin recombinant proteins activate the Tie1 receptor tyrosine kinase and promote its interaction with Tie2

The Tie1 receptor tyrosine kinase was isolated over a decade ago, but so far no ligand has been found to activate this receptor. Here, we have examined the potential of angiopoietins, ligands for the related Tie2 receptor, to mediate Tie1 activation. We show that a soluble Ang1 chimeric protein, COMP-Ang1, stimulates Tie1 phosphorylation in endothelial cells with similar kinetics and angiopoietin dose dependence when compared with Tie2. The phosphorylation of overexpressed Tie1 was weakly induced by COMP-Ang1 also in transfected cells that do not express Tie2. When cotransfected, Tie2 formed heteromeric complexes with Tie1, enhanced Tie1 activation, and induced phosphorylation of a kinase-inactive Tie1 in a ligand-dependent manner. Tie1 phosphorylation was also induced by native Ang1 and Ang4, although less efficiently than with COMP-Ang1. In conclusion, we show that Tie1 phosphorylation is induced by multiple angiopoietin proteins and that the activation is amplified via Tie2. These results should be important in dissecting the signal transduction pathways and biological functions of Tie1.     

Role of adenosine in regulating the heterogeneity of skeletal muscle blood flow during exercise in humans.

Evidence from both animal and human studies suggests that adenosine plays a role in the regulation of exercise hyperemia in skeletal muscle. We tested whether adenosine also plays a role in the regulation of blood flow (BF) distribution and heterogeneity among and within quadriceps femoris (QF) muscles during exercise, measured using positron emission tomography. In six healthy young women, BF was measured at rest and then during three incremental low and moderate intermittent isometric one-legged knee-extension exercise intensities without and with theophylline-induced nonselective adenosine receptor blockade. BF heterogeneity within muscles was calculated from 16-mm(3) voxels in BF images and heterogeneity among the muscles from the mean values of the four QF compartments. Mean BF in the whole QF and its four parts increased, and heterogeneity decreased with workload both without and with theophylline (P < 0.001). Adenosine receptor blockade did not have any effect on mean bulk BF or BF heterogeneity among the QF muscles, yet blockade increased within-muscle BF heterogeneity in all four QF muscles (P = 0.03). Taken together, these results show that BF becomes less heterogeneous with increasing exercise intensity in the QF muscle group. Adenosine seems to play a role in muscle BF heterogeneity even in the absence of changes in bulk BF at low and moderate one-leg intermittent isometric exercise intensities.     

Postlabelling HPLC analysis of lipophilic DNA adducts from human lung

A new modification of the 32P postlabelling method was described for the analysis of lipophilic DNA in human tissues. To isolate these DNA adducts the method applied nuclease P1 enrichment before labelling and butanol extraction after labelling, followed by high performance liquid chromatography HPLC separation and flow through radioactivity detection. These enrichment methods are known to work for many adducts of polycyclic aromatic hydrocarbons PAHs . In human peripheral lung tissue fro m smokers the apparent level of the DNA adducts observed was 25-244 adducts per 108 nucelotides; in two alleged non smokers the level of adducts was 17 and 109 adducts per 108 nucleotides. When the same samples were analysed by thin layer chromatography TLC , as in the conventional postlabelling assay, the recovery was 5 of that of the HPLC method. Nevertheless, the results from the two methods correlated. In TLC the adducts were lost because they did not remain in the origin in D1 of the TLC development. There was no large difference in recovery between the two techniques for the PAH-DNA adduct standards used. The present results are underestimates of the true adduct levels because there is no way to correct for labelling efficiency and recovery of unknown adducts. Yet they give a lower estimate of the level of lipophilic DNA adducts in human lung tissue.     

Evaluation of antifungal,phosphate solubilisation,and siderophore and chitinase release activities of endophytic fungi from <Emphasis Type="Italic">Pistacia vera</Emphasis>

Fungal endophytes use different strategies to protect host plants from abiotic and biotic stress. In this study, we isolated endophytic fungi from Pistacia vera and characterised their antifungal activity against Aspergillus flavus, Rhizoctonia solani and Sclerotinia sclerotiorum, and their release of some factors that can alter plant growth capability. Trichoderma harzianum TH 5-1-2, T. harzianum TH 10-2-2 and T. atroviride TA 2-2-1 exhibited the highest growth inhibition percentages in dual culture assays against A. flavus, R. solani and S. sclerotiorum, respectively. Among the fungal endophyte cultures, ethyl acetate extracts of T. harzianum TH 10-2-2, T. harzianum TH 5-1-2 and T. atroviride TA 2-2-1 exhibited the highest growth inhibition of S. sclerotiorum, R. solani and A. flavus, respectively. Phosphate solubilisation was induced by Byssochlamys nivea BN 1-1-1 in culture. Large amounts of siderophore production were observed with Quambalaria cyanescens QC 11-3-2 and Epicoccum nigrum EN1, but Trichoderma spp. also produced siderophore in lower amounts. Trichoderma harzianum TH 5-1-2 produced the highest chitinase activity (2.92 U/mL). In general, among the endophytes isolated, Trichoderma spp. appear to have the most promise for promoting healthy growth of P. vera.     

Positive involvemetn of ppGpp in derepression of the nif operon in Klebsiella pneumoniae

Summary The kinetics of derepression of the enzyme nitrogenase were investigated, after exhaustion of a limiting amount of ammonium from the culture medium, in a prototrophic stringent-relaxed pair of Klebsiella pneumoniae strains and in their F relA ⁺-F relA derivatives. The results indicate that ppGpp (guanosine 3–5 diphosphate) increases the nitrogen fixation capability of K. pneumoniae by at least three different mechanisms. (1) It prevents exhaustion of the ATP pool when nitrogen starvation is imposed. (2) The translational defects in relaxed mutants are suppressed by ppGpp during nif derepression. (3) The synthesis of nitrogenase components is at least five times higher in the presence of ppGpp than in its absence. This latter conclusion was based on experimental results obtained when following the incorporation of (³⁵S)-methionine into nitrogenase components after pulse labelling at various time intervals during nif derepression. The nitrogenase components were separated by solid phase radioimmunoassay as well as by two-dimensional gel electrophoresis.