Biochemical characterization of a singular mutant of nitrate reductase from Chlamydomonas reinhardii. New evidence for a heteropolymeric enzyme structure

A singular mutant strain from Chlamydomohas reinhardii defective in nitrate reductase has been characterized. Mutant 301 possesses an ammonia-repressible NAD(P)H-cytochrome c reductase with the same charge and size properties as the low molecular weight ammonia-repressible diaphorase present in the wild-type strain 6145c and is also able to reconstitute NAD(P)H-nitrate reductase activity by in vitro complementation with reduced benzyl viologen-nitrate reductase from mutant 305. Furthermore, a heat-labile costitutive molybdenum cofactor which is fuctionally active is also present in mutant 301. Mutant 301 has the two requirements exhibited by the active nitrate reductase complex from fungi, namely, NAD(P)H-cytochrome c reductase activity and molybdenum cofactor, but lacks NAD(P)H-nitrate reductase activity. This fact together with biochemical data presented from other C. reinhardii mutants strongly suggest a heteropolymeric model for the nitrate reductase complex of the alga.     

Using a top predator as a sentinel for environmental contamination with pathogenic bacteria: the Iberian wolf and leptospires

The Iberian wolf (Canis lupus) is the top predator in the Iberianenvironments in which it lives, feeding on a wide range of species, thus encounteringa wide range of disease agents. Therefore, the wolf can serve as sentinel ofenvironmental contamination with pathogens. We investigated the exposure offree-living wolves to 14 serovars of Leptospira interrogans sensulato. Kidney samples from 49 wolves collected from 2010-2013 innorthwestern Spain were analysed by culture, direct immunofluorescence and polymerasechain reaction. Tissue fluids were analysed for antibodies by a microscopicagglutination test. Ten wolves (observed prevalence: 20%, 95% confidence interval =11-33%) showed evidence of contact with leptospires, eight through direct detectionand nine through serology (7 wolves were positive according to both techniques).Titres below the cut-off level were also detected in seven cases. Serovars confirmedwere Canicola (n = 4), Icterohaemorrhagiae (n = 3) and Sejroë, Ballum andGrippotyphosa (n = 1 each), indicating that wolves were infected with serovars forwhich dogs, rodents and ungulates, are the natural hosts and supporting the utilityof the wolf and other large predators as environmental sentinels for pathogens.     

Patterns of habitat use and selection by the capybara (Hydrochoerus hydrochaeris): a landscape-scale analysis

Habitat selection analysis provides useful information on how animals become distributed in response to spatial heterogeneity. Here, we analyze the habitat use and selection of different water bodies (marsh, swamps and round shallow lakes) by capybaras (Hydrochoerus hydrochaeris) and their relation to environmental variables during contrasting climate-hydrological seasons in the Esteros del Iberá (Corrientes, Argentina). We evaluated the intensity of use by capybaras through the total number of individuals (abundance) in each water body, the number and mean size of social groups, and the physical and vegetation characteristics of the environment. The capybaras used marsh and swamps according to availability in both seasons, while they used rounded shallow lakes less than their available would suggest in summer. The use intensity of different rounded shallow lakes estimated based on group size did not show significant differences. In contrast, significant differences were observed when evaluated by the number of individuals in each rounded shallow lake. Different intensity of use was closely associated with environmental and vegetation characteristics. The results show that habitat suitability for capybaras is associated with vegetation cover and “embalsados” in the low-lying area rather than with the morphometry of the rounded shallow lakes. The pattern of habitat selection may depend on forage quality, water availability for thermoregulation and mating, and presence of shelter and resting sites. On the other hand, the present study shows how the size, shape and the abundance of different types of water bodies affect population abundance and density.     

PI3K inhibition in inflammation: Toward tailored therapies for specific diseases

In the past decade, the availability of genetically modified animals has enabled the discovery of interesting roles for phosphatidylinositol 3‐kinase‐γ (PI3Kγ) and ‐δ (PI3Kδ) in different cell types orchestrating innate and adaptive immune responses. Therefore, these PI3K isoforms appear to be attractive drug targets for the treatment of diseases caused by unrestrained immune reactions. Currently, pharmacological targeting of PI3Kγ and/or PI3Kδ represents one of the most promising challenges for companies interested in the development of novel safe treatments for inflammatory diseases. In this review we provide a general outline of PI3Kγ‐ and PI3Kδ‐specific functions in distinct subsets of inflammatory cells. We also discuss the therapeutic impact of novel compounds targeting PI3Kγ, PI3Kδ or both, in mouse models of autoimmune disorders (systemic lupus erythematosus (SLE) and rheumatoid arthritis), respiratory diseases (allergic asthma and chronic obstructive pulmonary disease) and cardiovascular dysfunctions (atherosclerosis and myocardial infarction).     

Effect of artemisinin on oocyst wall formation and sporulation during Eimeria tenella infection

The anticoccidial effect of a product extracted from the natural herb Artemisia annua, artemisinin, which has a potential use as a dietary supplement, has been studied. Commercial artemisinin was administered at 10 and 17 ppm in food and tested against infection with Eimeria tenella. A battery trial to quantify the effect of artemisinin on the reproductive and infective capabilities of E. tenella was carried out. For that purpose flow cytometry was combined with electron microscopy and immunofluorescence techniques in order to study the effect of artemisinin on E. tenella gametogenesis. Significantly reduced oocyst output and lesion scores were found in chickens treated with artemisinin. In addition, evidence to support a lower oocyst sporulation rate was obtained. Though the ultrastructural studies showed normal development of gametogenesis in artemisinin-treated chickens, the oocyst wall formation was significantly altered. This resulted in both death of developing oocysts and reduced sporulation rate. Immunofluorescent studies provided evidence that treatment with artemisinin inhibited sarcoplasmic–endoplasmic reticulum calcium ATPase (SERCA) expression in macrogametes. According to these findings, artemisinin has a deleterious effect on fertilized macrogametes (early zygotes) by inhibiting SERCA. The altered secretion of the wall-forming bodies may be the result of Ca²⁺-dependent ATPase impaired activity which, in turn, is the result of SERCA inhibition.     

Low plant density enhances gene dispersal in the Amazonian understory herb Heliconia acuminata

In theory, conservation genetics predicts that forest fragmentation will reduce gene dispersal, but in practice, genetic and ecological processes are also dependent on other population characteristics. We used Bayesian genetic analyses to characterize parentage and propagule dispersal in Heliconia acuminata L. C. Richard (Heliconiaceae), a common Amazonian understory plant that is pollinated and dispersed by birds. We studied these processes in two continuous forest sites and three 1‐ha fragments in Brazil's Biological Dynamics of Forest Fragments Project. These sites showed variation in the density of H. acuminata. Ten microsatellite markers were used to genotype flowering adults and seedling recruits and to quantify realized pollen and seed dispersal distances, immigration of propagules from outside populations, and reproductive dominance among parents. We tested whether gene dispersal is more dependent on fragmentation or density of reproductive plants. Low plant densities were associated with elevated immigration rates and greater propagule dispersal distances. Reproductive dominance among inside‐plot parents was higher for low‐density than for high‐density populations. Elevated local flower and fruit availability is probably leading to spatially more proximal bird foraging and propagule dispersal in areas with high density of reproductive plants. Nevertheless, genetic diversity, inbreeding coefficients and fine‐scale spatial genetic structure were similar across populations, despite differences in gene dispersal. This result may indicate that the opposing processes of longer dispersal events in low‐density populations vs. higher diversity of contributing parents in high‐density populations balance the resulting genetic outcomes and prevent genetic erosion in small populations and fragments.     

Predicting genetic values: a kernel-based best linear unbiased prediction with genomic data

Genomic data provide a valuable source of information for modeling covariance structures, allowing a more accurate prediction of total genetic values (GVs). We apply the kriging concept, originally developed in the geostatistical context for predictions in the low-dimensional space, to the high-dimensional space spanned by genomic single nucleotide polymorphism (SNP) vectors and study its properties in different gene-action scenarios. Two different kriging methods ["universal kriging" (UK) and "simple kriging" (SK)] are presented. As a novelty, we suggest use of the family of Matérn covariance functions to model the covariance structure of SNP vectors. A genomic best linear unbiased prediction (GBLUP) is applied as a reference method. The three approaches are compared in a whole-genome simulation study considering additive, additive-dominance, and epistatic gene-action models. Predictive performance is measured in terms of correlation between true and predicted GVs and average true GVs of the individuals ranked best by prediction. We show that UK outperforms GBLUP in the presence of dominance and epistatic effects. In a limiting case, it is shown that the genomic covariance structure proposed by VanRaden (2008) can be considered as a covariance function with corresponding quadratic variogram. We also prove theoretically that if a specific linear relationship exists between covariance matrices for two linear mixed models, the GVs resulting from BLUP are linked by a scaling factor. Finally, the relation of kriging to other models is discussed and further options for modeling the covariance structure, which might be more appropriate in the genomic context, are suggested.     

Iron and Proinflammatory Cytokines in Chronic Hepatitis C Virus Infection

Steatohepatitis is a common finding in chronic hepatitis C virus (HCV) infection. As in other forms of steatohepatitis, oxidative damage may play an outstanding role. However, there are conflicting results relative to the role of iron on hepatic lipogenesis. Proinflammatory cytokines up-regulate ferritin expression, probably reflecting a defensive mechanism against increased oxidative stress, capable to open haem ring and release reactive iron. On the contrary, some adipokines, such as adiponectin, are associated with low ferritin levels. The aim of this study is to analyse the relationships of the amount of liver steatosis with serum iron, transferrin and ferritin as well as with proinflammatory cytokines, such as tumour necrosis factor (TNF)-α and interleukin (IL)-6, and adiponectin levels. We included 82 HCV infected patients and assessed the amount of liver fat by histomorphometry and its relationships with serum iron, ferritin and transferrin, adiponectin and TNF-α and IL-6. Liver steatosis was observed in 67 patients out of 82; in the remaining 15 patients, no steatosis at all was found. Patients with steatosis showed significantly higher serum ferritin levels than patients without steatosis (Z?=?2.14; p?=?0.032). When patients were classified in quartiles according to the intensity of steatosis, we observed that both TNF-α (KW?=?10.6; p?=?0.014) and IL-6 (KW?=?15.2; p?=?0.002) were significantly different among the four groups. Patients with more intense steatosis (highest quartile) showed the highest TNF-α and IL-6 values. Patients with severe hepatitis had higher levels of serum iron than patients with mild to moderate hepatitis. Serum iron also showed a correlation with the proportion of fibrosis (ρ?=?0.30; p?=?0.007). Serum iron levels are related with biochemical and histological parameters derived from liver inflammation in HCV-associated liver disease. Serum ferritin is higher among those with intense steatosis and also shows a (non-significant) trend to be associated with the more severe forms of hepatitis.