Plasmacytoid Dendritic Cells Sequester High Prion Titres at Early Stages of Prion Infection

In most transmissible spongiform encephalopathies prions accumulate in the lymphoreticular system (LRS) long before they are detectable in the central nervous system. While a considerable body of evidence showed that B lymphocytes and follicular dendritic cells play a major role in prion colonization of lymphoid organs, the contribution of various other cell types, including antigen-presenting cells, to the accumulation and the spread of prions in the LRS are not well understood. A comprehensive study to compare prion titers of candidate cell types has not been performed to date, mainly due to limitations in the scope of animal bioassays where prohibitively large numbers of mice would be required to obtain sufficiently accurate data. By taking advantage of quantitative in vitro prion determination and magnetic-activated cell sorting, we studied the kinetics of prion accumulation in various splenic cell types at early stages of prion infection. Robust estimates for infectious titers were obtained by statistical modelling using a generalized linear model. Whilst prions were detectable in B and T lymphocytes and in antigen-presenting cells like dendritic cells and macrophages, highest infectious titers were determined in two cell types that have previously not been associated with prion pathogenesis, plasmacytoid dendritic (pDC) and natural killer (NK) cells. At 30 days after infection, NK cells were more than twice, and pDCs about seven-fold, as infectious as lymphocytes respectively. This result was unexpected since, in accordance to previous reports prion protein, an obligate requirement for prion replication, was undetectable in pDCs. This underscores the importance of prion sequestration and dissemination by antigen-presenting cells which are among the first cells of the immune system to encounter pathogens. We furthermore report the first evidence for a release of prions from lymphocytes and DCs of scrapie-infected mice ex vivo, a process that is associated with a release of exosome-like membrane vesicles.     

Short term hypothyroidism affects ovarian function in the cycling rat

Background  

Rats made hypothyroid with propilthyouracil start showing abnormal cycling on the second cycle after the start of the treatment, with a high proportion of spontaneous pseudopregnancies and reduced fertility.     

The USDA Barley Core Collection: Genetic Diversity,Population Structure,and Potential for Genome-Wide Association Studies

New sources of genetic diversity must be incorporated into plant breeding programs if they are to continue increasing grain yield and quality, and tolerance to abiotic and biotic stresses. Germplasm collections provide a source of genetic and phenotypic diversity, but characterization of these resources is required to increase their utility for breeding programs. We used a barley SNP iSelect platform with 7,842 SNPs to genotype 2,417 barley accessions sampled from the USDA National Small Grains Collection of 33,176 accessions. Most of the accessions in this core collection are categorized as landraces or cultivars/breeding lines and were obtained from more than 100 countries. Both STRUCTURE and principal component analysis identified five major subpopulations within the core collection, mainly differentiated by geographical origin and spike row number (an inflorescence architecture trait). Different patterns of linkage disequilibrium (LD) were found across the barley genome and many regions of high LD contained traits involved in domestication and breeding selection. The genotype data were used to define ‘mini-core’ sets of accessions capturing the majority of the allelic diversity present in the core collection. These ‘mini-core’ sets can be used for evaluating traits that are difficult or expensive to score. Genome-wide association studies (GWAS) of ‘hull cover’, ‘spike row number’, and ‘heading date’ demonstrate the utility of the core collection for locating genetic factors determining important phenotypes. The GWAS results were referenced to a new barley consensus map containing 5,665 SNPs. Our results demonstrate that GWAS and high-density SNP genotyping are effective tools for plant breeders interested in accessing genetic diversity in large germplasm collections.     

Effect of antioxidants on the genetic stability of cryopreserved mint shoot tips by encapsulation–dehydration

The effect of antioxidants applied in one step of a cryopreservation protocol by encapsulation–dehydration on recovery and genetic stability of mint shoot tips has been studied. Glutathione (0.16 or 0.24 mM), ascorbic acid (0.28 or 0.43 mM) and α-tocopherol (vitamin E) were added to the preculture medium (0.3 M sucrose). DNA was extracted from three different types of samples: leaves from shoots, callus at the base of shoots and callus. RAPD and AFLP markers were used to assess the genetic stability. The use of antioxidants did not improve recovery after cryopreservation. One of the genotypes, ‘MEN 198’, showed higher percentage of stable samples than the other one, ‘MEN 186’ (56 vs. 37?%; considering all treatments and types of explant). The use of vitamin E improved the percentage of stable samples with respect to control treatment (no antioxidant) in ‘MEN 186’. No differences in the percentages of stable samples were observed among cryopreserved and non-cryopreserved (treated similarly without immersion in liquid nitrogen) plant material. Recovered shoots of both genotypes showed higher stability (76–80?% stable samples) than callus samples (14–22?%).     

A Distinct Class of Genome Rearrangements Driven by Heterologous Recombination

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<Emphasis Type="Italic">Trichomonas vaginalis</Emphasis> metalloproteinase TvMP50 is a monomeric Aminopeptidase P-like enzyme

Previously, metalloproteinase was isolated and identified from Trichomonas vaginalis, belonging to the aminopeptidase P-like metalloproteinase subfamily A/B, family M24 of clan MG, named TvMP50. The native and recombinant TvMP50 showed proteolytic activity, determined by gelatin zymogram, and a 50 kDa band, suggesting that TvMP50 is a monomeric active enzyme. This was an unexpected finding since other Xaa-Pro aminopeptidases/prolidases are active as a biological unit formed by dimers/tetramers. In this study, the evolutionary history of TvMP50 and the preliminary crystal structure of the recombinant enzyme determined at 3.4 Å resolution is reported. TvMP50 was shown to be a type of putative, eukaryotic, monomeric aminopeptidase P, and the crystallographic coordinates showed a monomer on a “pseudo-homodimer” array on the asymmetric unit that resembles the quaternary structure of the M24B dimeric family and suggests a homodimeric aminopeptidase P-like enzyme as a likely ancestor. Interestingly, TvMP50 had a modified N-terminal region compared with other Xaa-Pro aminopeptidases/prolidases with three-dimensional structures; however, the formation of the standard dimer is structurally unstable in aqueous solution, and a comparably reduced number of hydrogen bridges and lack of saline bridges were found between subunits A/B, which could explain why TvMP50 portrays monomeric functionality. Additionally, we found that the Parabasalia group contains two protein lineages with a “pita bread” fold; the ancestral monomeric group 1 was probably derived from an ancestral dimeric aminopeptidase P-type enzyme, and group 2 has a probable dimeric kind of ancestral eukaryotic prolidase lineage. The implications of such hypotheses are also presented.     

Role of melatonin in the oxidative damage prevention at different times of hepatic regeneration

The process of regenerating liver is the result of a balance between stimulating factors and inhibitors of hepatocyte proliferation. Melatonin and its metabolites have been found to protect tissues against oxidative damage generated by a variety of toxic agents and metabolic processes. Furthermore, studies in liver of rats showed a decrease in the liver mitochondrial hydroxylation of drugs returning to the normal state after the administration of antioxidants. This study was designed to determine, in experimental animals, whether the administration of an antioxidant agent such as melatonin could prevent cells events leading to tissue injury and hepatic dysfunction after partial hepatectomy (PH). Biliary flow (BF), oxidative stress in hepatic tissue and Na⁺/K⁺ATPase activities in whole plasma membrane were determined. PH decreased the Na⁺/K⁺ATPase activity. PH significantly reduced the BF (36%) and promoted oxidative stress with an increase of lipoperoxidation and decrease of glutathione peroxidase and catalase activities. Treatment with melatonin prevented the decrease of BF in rats with hepatectomy and normalized the Na⁺/K⁺ATPase activity. Moreover, melatonin markedly attenuated oxidative stress produced by PH. This may be the results of the higher efficacy of melatonin in scavenging various free radicals and also because of its ability in stimulating the antioxidant enzymes. We suggest that oxidative stress before and during liver regeneration has a crucial role in cholestasis, apoptotic/necrotic hepatocellular damage and the impairment in liver transport function induced by PH and that melatonin could modulate the degree of oxidative stress and through it prevent the alterations in liver function carrier. Copyright © 2012 John Wiley & Sons, Ltd.     

Pyrenean Pastoralists’ Ecological Knowledge: Documentation and Application to Natural Resource Management and Adaptation

Pastoral production systems in the Spanish Pyrenees have changed dramatically in recent decades, leading to the loss of traditional ecological knowledge (TEK). We documented TEK of pastoralists from two valleys in the western Central Pyrenees of Aragón and explored its potential applications to resource management and adaptation. Pyrenean pastoralists possess extensive knowledge of relationships between terrain, climate, vegetation and animal nutrition and behavior. TEK could contribute to sustainable stewardship and facilitate adaptation by informing pasture monitoring; providing traditional practices to manage mountain vegetation; and preserving knowledge of extensive livestock production strategies, such as transhumance. Institutional barriers to applying TEK include weak economic cooperation among stockmen, their dependence on EU subsidies, and lack of voice in regional government decisions about local resources. A more collaborative, place-based stewardship of the Central Pyrenees might begin with direct involvement of pastoralists in designing monitoring of pasture conditions and vegetation type changes.     

Influence measures based on the volume of confidence ellipsoids for GEE

The generalized estimating equations (GEE) derived by Liang and Zeger to analyze longitudinal data have been used in a wide range of medical and biological applications. To make regression a useful and meaningful statistical tool, emphasis should be placed not only on inference or fitting, but also on diagnosing potential data problems. Most of the usual diagnostics for linear regression models have been generalized for GEE. However, global influence measures based on the volume of confidence ellipsoids are not available for GEE analysis. This article presents an extension of these measures that is valid for correlated‐measures regression analysis using GEEs. The proposed measures are illustrated by an analysis of epileptic seizure count data arising from a study of prograbide as an adjuvant therapy for partial seizures and some simulated data sets.