The human prion octarepeat fragment prevents and reverses the inhibitory action of copper in the P2X4 receptor without modifying the zinc action

Human prion protein fragments (PrP60-67 or PrP59-91) prevented and reversed the inhibition elicited by 5 micro m copper on the P2X4 receptor expressed in Xenopus laevis oocytes. A 60-s pre-application of 5 micro m copper caused a 69.2 +/- 2.6% inhibition of the 10 micro m adenosine triphosphate (ATP)-evoked currents, an effect that was prevented by mixing 5 micro m copper with 0.01-10 micro m of the PrP fragments 1-min prior to application. This interaction was selective, as PrP59-91 did not alter the facilitatory action of zinc. The EC50 of PrP60-67 and PrP59-91 for the reduction of the copper inhibition were 4.6 +/- 1 and 1.3 +/- 0.4 micro m, respectively. A synthetic PrP59-91 variant in which all four His were replaced by Ala was inactive. However, the replacement of Trp in each of the four putative copper-binding domains by Ala slightly decreased its potency. Furthermore, the application of 10 micro m PrP59-91 reversed the copper-evoked inhibition, restoring the ATP concentration curve to the same level as the non-inhibited state. Fragment 139-157 of betaA4 amyloid precursor protein also prevented the action of copper; its EC50 was 1.6 +/- 0.1 micro m; the metal chelator penicillamine was equipotent with PrP60-67, but carnosine was significantly less potent. Our findings highlight the role of PrP in copper homeostasis and hint at its possible role as a modulator of synapses regulated by this trace metal.     

Neutrophils as a novel source of eosinophil cationic protein in IgE-mediated processes

The production of eosinophil cationic protein (ECP) in IgE-mediated diseases has been associated mainly with eosinophils, although no IgE-dependent ECP release has been observed in these cells. Because there is increasing evidence of neutrophil participation in allergic processes, we have examined whether human neutrophils from allergic patients were able to produce ECP by an IgE-dependent mechanism. After challenge with specific Ags to which the patients were sensitized, ECP release was detected in the culture medium. Furthermore, intracellular protein was detected by flow cytometry, immunofluorescence staining, and Western blotting. Expression at both mRNA and de novo protein synthesis were detected, respectively, by RT-PCR and radiolabeling with (35)S. Ag effect was mimicked by cell treatment with anti-IgE Abs or Abs against FcepsilonRI and galectin-3 (FcepsilonRI>galectin-3), but not against FcepsilonRII. These observations represent a novel view of neutrophils as possible source of ECP in IgE-dependent diseases.     

Amyloid β serves as an NGF‐like neurotrophic factor or acts as a NGF antagonist depending on its concentration

In the nervous system, both the shape and connectivity of neurons are strongly influenced by soluble, extracellular factors. Indeed, we recently demonstrated that after binding to p75^NTR, the common neurotrophin receptor, nerve growth factor (NGF) controls the morphology and connectivity of cultured mouse hippocampal neurons by encouraging the production of fewer yet longer dendrites, and by augmenting GABAergic connectivity. These effects of NGF are mediated by the differential expression of Enhancer‐of‐split 1/5 homologs and neurogenin 3. Amyloid β (Aβ), a pathogenic agent in Alzheimer’s disease (AD) is known to bind to p75^NTR, hence we studied its influence on cultured hippocampal neurons. At 800 nM, Aβ(1–40) prevents NGF‐induced activation of NF‐κB and consequently, it depresses the expression of Enhancer‐of‐split 1. Thus, at this concentration, the effect of Aβ on neurons is antagonistic to those provoked by NGF and accordingly, neurons sprout more yet shorter dendrites and their GABAergic input decreases. In contrast, at lower concentration, 20 nM, the amyloid induces cellular effects similar to those induced by NGF, both in terms of gene expression, neuronal morphology, and GABAergic connectivity. Our results demonstrate that Aβ may act as a neurotrophic factor that mimics the activity of NGF. However, at higher concentrations, the amyloid behaves as an antagonist of NGF, contributing to the advent of AD.     

Spatio-temporal expression of MMP-2, MMP-9 and tissue kallikrein in uteroplacental units of the pregnant guinea-pig (Cavia porcellus)

Background  

In humans trophoblast invasion and vascular remodeling are critical to determine the fate of pregnancy. Since guinea-pigs share with women an extensive migration of the trophoblasts through the decidua and uterine arteries, and a haemomonochorial placenta, this species was used to evaluate the spatio-temporal expression of three enzymes that have been associated to trophoblast invasion, MMP-2, MMP-9 and tissue kallikrein (K1).     

Domestication patterns in common bean (Phaseolus vulgaris L.) and the origin of the Mesoamerican and Andean cultivated races

Chloroplast DNA polymorphisms were studied by PCR sequencing and PCR-restriction fragment length polymorphism in 165 accessions of domesticated landraces of common bean from Latin America and the USA, 23 accessions of weedy beans, and 134 accessions of wild beans covering the entire geographic range of wild Phaseolus vulgaris. Fourteen chloroplast haplotypes were identified in wild beans, only five of which occur also in domesticated beans. The chloroplast data agree with those obtained from analyses based on morphology and isozymes and with other DNA polymorphisms in supporting independent domestications of common bean in Mesoamerica and the Andean region and in demonstrating a founder effect associated with domestication in each region. Andean landraces have been classified into three different racial groups, but all share the same chloroplast haplotype. This suggests that common bean was domesticated once only in South America and that the races diverged post-domestication. The haplotype found in Andean domesticated beans is confined to the southern part of the range of wild beans, so Andean beans were probably domesticated somewhere within this area. Mesoamerican landraces have been classified into four racial groups. Our limited samples of Races Jalisco and Guatemala differ from the more widespread and commercially important Races Mesoamerica and Durango in types and/or frequencies of haplotypes. All four Mesoamerican races share their haplotypes with local wild beans in parts of their ranges. Independent domestications of at least some of the races in Mesoamerica and/or conversion of some locally adapted wild beans to cultigens by hybridization with introduced domesticated beans, followed by introgression of the domestication syndrome seem the most plausible explanations of the chloroplast and other molecular data.     

Larger aboveground neighbourhood scales maximise similarity but do not eliminate discrepancies with belowground plant diversity in a Mediterranean shrubland

Plant and Soil - An unresolved question in plant ecology is whether diversity of the aboveground and belowground compartments of a plant community is similar at different neighbourhood scales. We...     

Genetic diversity and patterns of population structure in Creole goats from the Americas

Biodiversity studies are more efficient when large numbers of breeds belonging to several countries are involved, as they allow for an in‐depth analysis of the within‐ and between‐breed components of genetic diversity. A set of 21 microsatellites was used to investigate the genetic composition of 24 Creole goat breeds (910 animals) from 10 countries to estimate levels of genetic variability, infer population structure and understand genetic relationships among populations across the American continent. Three commercial transboundary breeds were included in the analyses to investigate admixture with Creole goats. Overall, the genetic diversity of Creole populations (mean number of alleles = 5.82 ± 1.14, observed heterozygosity = 0.585 ± 0.074) was moderate and slightly lower than what was detected in other studies with breeds from other regions. The Bayesian clustering analysis without prior information on source populations identified 22 breed clusters. Three groups comprised more than one population, namely from Brazil (Azul and Graúna; Moxotó and Repartida) and Argentina (Long and shorthair Chilluda, Pampeana Colorada and Angora‐type goat). Substructure was found in Criolla Paraguaya. When prior information on sample origin was considered, 92% of the individuals were assigned to the source population (threshold q ≥ 0.700). Creole breeds are well‐differentiated entities (mean coefficient of genetic differentiation = 0.111 ± 0.048, with the exception of isolated island populations). Dilution from admixture with commercial transboundary breeds appears to be negligible. Significant levels of inbreeding were detected (inbreeding coefficient > 0 in most Creole goat populations, P < 0.05). Our results provide a broad perspective on the extant genetic diversity of Creole goats, however further studies are needed to understand whether the observed geographical patterns of population structure may reflect the mode of goat colonization in the Americas.