Caspase-Dependent Inhibition of Mousepox Replication by gzmB

Background

Ectromelia virus is a natural mouse pathogen, causing mousepox. The cytotoxic T (Tc) cell granule serine-protease, granzyme B, is important for its control, but the underlying mechanism is unknown. Using ex vivo virus immune Tc cells, we have previously shown that granzyme B is able to activate several independent pro-apoptotic pathways, including those mediated by Bid/Bak/Bax and caspases-3/-7, in target cells pulsed with Tc cell determinants.

Methods and Findings

Here we analysed the physiological relevance of those pro-apoptotic pathways in ectromelia infection, by incubating ectromelia-immune ex vivo Tc cells from granzyme A deficient (GzmB⁺ Tc cells) or granzyme A and granzyme B deficient (GzmA×B^−/− Tc cell) mice with ectromelia-infected target cells. We found that gzmB-induced apoptosis was totally blocked in ectromelia infected or peptide pulsed cells lacking caspases-3/-7. However ectromelia inhibited only partially apoptosis in cells deficient for Bid/Bak/Bax and not at all when both pathways were operative suggesting that the virus is able to interfere with apoptosis induced by gzmB in case not all pathways are activated. Importantly, inhibition of viral replication in vitro, as seen with wild type cells, was not affected by the lack of Bid/Bak/Bax but was significantly reduced in caspase-3/-7-deficient cells. Both caspase dependent processes were strictly dependent on gzmB, since Tc cells, lacking both gzms, neither induced apoptosis nor reduced viral titers.

Significance

Out findings present the first evidence on the biological importance of the independent gzmB-inducible pro-apoptotic pathways in a physiological relevant virus infection model.     

Recent Rapid Rise of a Permethrin Knock Down Resistance Allele in Aedes aegypti in México

Background

Aedes aegypti, the ‘yellow fever mosquito’, is the primary vector to humans of dengue and yellow fever flaviviruses (DENV, YFV), and is a known vector of the chikungunya alphavirus (CV). Because vaccines are not yet available for DENV or CV or are inadequately distributed in developing countries (YFV), management of Ae. aegypti remains the primary option to prevent and control outbreaks of the diseases caused by these arboviruses. Permethrin is one of the most widely used active ingredients in insecticides for suppression of adult Ae. aegypti. In 2007, we documented a replacement mutation in codon 1,016 of the voltage-gated sodium channel gene (para) of Ae. aegypti that encodes an isoleucine rather than a valine and confers resistance to permethrin. Ile1,016 segregates as a recessive allele conferring knockdown resistance to homozygous mosquitoes at 5–10 µg of permethrin in bottle bioassays.

Methods and Findings

A total of 81 field collections containing 3,951 Ae. aegypti were made throughout México from 1996 to 2009. These mosquitoes were analyzed for the frequency of the Ile1,016 mutation using a melting-curve PCR assay. Dramatic increases in frequencies of Ile1,016 were recorded from the late 1990''s to 2006–2009 in several states including Nuevo León in the north, Veracruz on the central Atlantic coast, and Yucatán, Quintana Roo and Chiapas in the south. From 1996 to 2000, the overall frequency of Ile1,016 was 0.04% (95% confidence interval (CI95) = 0.12%; n = 1,359 mosquitoes examined). The earliest detection of Ile1,016 was in Nuevo Laredo on the U.S. border in 1997. By 2003–2004 the overall frequency of Ile1,016 had increased ∼100-fold to 2.7% (±0.80% CI95; n = 808). When checked again in 2006, the frequency had increased slightly to 3.9% (±1.15% CI95; n = 473). This was followed in 2007–2009 by a sudden jump in Ile1,016 frequency to 33.2% (±1.99% CI95; n = 1,074 mosquitoes). There was spatial heterogeneity in Ile1,016 frequencies among 2007–2008 collections, which ranged from 45.7% (±2.00% CI95) in the state of Veracruz to 51.2% (±4.36% CI95) in the Yucatán peninsula and 14.5% (±2.23% CI95) in and around Tapachula in the state of Chiapas. Spatial heterogeneity was also evident at smaller geographic scales. For example within the city of Chetumal, Quintana Roo, Ile1,016 frequencies varied from 38.3%–88.3%. A linear regression analysis based on seven collections from 2007 revealed that the frequency of Ile1,016 homozygotes accurately predicted knockdown rate for mosquitoes exposed to permethrin in a bioassay (R² = 0.98).

Conclusions

We have recorded a dramatic increase in the frequency of the Ile1,016 mutation in the voltage-gated sodium channel gene of Ae. aegypti in México from 1996 to 2009. This may be related to heavy use of permethrin-based insecticides in mosquito control programs. Spatial heterogeneity in Ile1,016 frequencies in 2007 and 2008 collections may reflect differences in selection pressure or in the initial frequency of Ile1,016. The rapid recent increase in Ile1,016 is predicted by a simple model of positive directional selection on a recessive allele. Unfortunately this model also predicts rapid fixation of Ile1,016 unless there is negative fitness associated with Ile1,016 in the absence of permethrin. If so, then spatial refugia of susceptible Ae. aegypti or rotational schedules of different classes of adulticides could be established to slow or prevent fixation of Ile1,016.     

Contamination of tissue allografts from a deceased donor through haematic dissemination: a case study

Infection is one of the most dangerous complications that can be seen when implanting bone or tendon allografts from a deceased donor. The most common germs isolated are found among the cutaneous florae, but sometimes they may be present in the bloodstream as a result of severe injuries suffered before the time of the decease. We present a case of contamination of allografts in a musculoskeletal tissue donor deceased after an accident, whose allografts were contaminated by gastrointestinal microorganisms, probably disseminated through the donor’s blood.     

Conservation of oceanic island floras: Present and future global challenges

Current threats to the planet's biodiversity are unprecedented, and they particularly imperil insular floras. In this investigation, we use the threat factors identified by the Millennium Ecosystem Assessment as the main drivers of biodiversity loss on islands to define and rank 13 current, continuing threats to the plant diversity of nine focal archipelagos where volcanic origin (or in the Seychelles a prolonged isolation after a continental origin) has produced a high degree of endemicity and fragility in the face of habitat alteration. We also conduct a global endangerment assessment based on the numbers of insular endemic plants in the endangered (EN) and critically endangered (CR) IUCN categories for 53 island groups with an estimated 9951 endemic plant species, providing a representative sample of the world's insular systems and their floristic richness. Our analyses indicate that isolation does not significantly influence endangerment, but plant endemics from very small islands are more often critically endangered. We estimate that between 3500 and 6800 of the estimated 70,000 insular endemic plant species worldwide might be highly threatened (CR+EN) and between ca. 2000 and 2800 of them in critical danger of extinction (CR). Based on these analyses, and on a worldwide literature review of the biological threat factors considered, we identify challenging questions for conservation research, asking (i) what are the most urgent priorities for the conservation of insular species and floras, and (ii) with the knowledge and assets available, how can we improve the impact of conservation science and practice on the preservation of island biodiversity? Our analysis indicates that the synergistic action of many threat factors can induce major ecological disturbances, leading to multiple extinctions. We review weaknesses and strengths in conservation research and management in the nine focal archipelagos, and highlight the urgent need for conservation scientists to share knowledge and expertise, identify and discuss common challenges, and formulate multi-disciplinary conservation objectives for insular plant endemics worldwide. To our knowledge, this is the most up-to-date and comprehensive survey yet to review the threat factors to native plants on oceanic islands and define priority research questions.     

The INTERPRET Decision-Support System version 3.0 for evaluation of Magnetic Resonance Spectroscopy data from human brain tumours and other abnormal brain masses

Background  

Proton Magnetic Resonance (MR) Spectroscopy (MRS) is a widely available technique for those clinical centres equipped with MR scanners. Unlike the rest of MR-based techniques, MRS yields not images but spectra of metabolites in the tissues. In pathological situations, the MRS profile changes and this has been particularly described for brain tumours. However, radiologists are frequently not familiar to the interpretation of MRS data and for this reason, the usefulness of decision-support systems (DSS) in MRS data analysis has been explored.     

SpectraClassifier 1.0: a user friendly,automated MRS-based classifier-development system

Background  

SpectraClassifier (SC) is a Java solution for designing and implementing Magnetic Resonance Spectroscopy (MRS)-based classifiers. The main goal of SC is to allow users with minimum background knowledge of multivariate statistics to perform a fully automated pattern recognition analysis. SC incorporates feature selection (greedy stepwise approach, either forward or backward), and feature extraction (PCA). Fisher Linear Discriminant Analysis is the method of choice for classification. Classifier evaluation is performed through various methods: display of the confusion matrix of the training and testing datasets; K-fold cross-validation, leave-one-out and bootstrapping as well as Receiver Operating Characteristic (ROC) curves.     

Community impacts of anthropogenic disturbance: natural enemies exploit multiple routes in pursuit of invading herbivore hosts

Background  

Biological invasions provide a window on the process of community assembly. In particular, tracking natural enemy recruitment to invading hosts can reveal the relative roles of co-evolution (including local adaptation) and ecological sorting. We use molecular data to examine colonisation of northern Europe by the parasitoid Megastigmus stigmatizans following invasions of its herbivorous oak gallwasp hosts from the Balkans. Local host adaptation predicts that invading gallwasp populations will have been tracked primarily by sympatric Balkan populations of M. stigmatizans (Host Pursuit Hypothesis). Alternatively, ecological sorting allows parasitoid recruitment from geographically distinct populations with no recent experience of the invading hosts (Host Shift Hypothesis). Finally, we test for long-term persistence of parasitoids introduced via human trade of their hosts' galls (Introduction Hypothesis).     

Protein oligomerization mediated by the transmembrane carboxyl terminal domain of Bcl-XL

Bcl-XL is a pro-survival member of the Bcl-2 family that can be found in the outer mitochondrial membrane and in soluble cytosolic homodimers. Bcl-XL can bind pro-apoptotic members of this family preventing them from activating the execution phase of apoptosis. Bcl-XL has been shown to homodimerize in different ways, although most binding and structural assays have been carried out in the absence of its carboxyl terminal transmembrane domain. We show here that this domain can by itself direct protein oligomerization, which could be related to its previously reported role in mitochondrial morphology alterations and apoptosis inhibition.     

Natural alcohol exposure: is ethanol the main substrate for alcohol dehydrogenases in animals?

Alcohol dehydrogenase (ADH) activity is widely distributed in all phyla. In animals, three non-homologous NAD(P)(+)-dependent ADH protein families are reported. These arose independently throughout evolution and possess different structures and mechanisms of reaction: type I (medium-chain) ADHs are zinc-containing enzymes and comprise the most studied group in vertebrates; type II (short-chain) ADHs lack metal cofactor and have been extensively studied in Drosophila; and type III ADHs are iron-dependent/-activated enzymes that were initially identified only in microorganisms. The presence of these different ADHs in animals has been assumed to be a consequence of chronic exposure to ethanol. By far the most common natural source of ethanol is fermentation of fruit sugars by yeast, and available data support that this fruit trait evolved in concert with the characteristics of their frugivorous seed dispersers. Therefore, if the presence of ADHs in animals evolved as an adaptive response to dietary ethanol exposure, then it can be expected that the enzymogenesis of these enzymes began after the appearance of angiosperms with fleshy fruits, because substrate availability must precede enzyme selection. In this work, available evidence supporting this possibility is discussed. Phylogenetic analyses reveal that type II ADHs suffered several duplications, all of these restricted to flies (order Diptera). Induction of type II Adh by ethanol exposure, a positive correlation between ADH activity and ethanol resistance, and the fact that flies and type II Adh diversification occurred in concert with angiosperm diversification, strongly suggest that type II ADHs were recruited to allow larval flies to exploit new restricted niches with high ethanol content. In contrast, phyletic distribution of types I and III ADHs in animals showed that these appeared before angiosperms and land plants, independently of ethanol availability. Because these enzymes are not induced by ethanol exposure and possess a high affinity and/or catalytic efficiency for non-ethanol endogenous substrates, it can be concluded that the participation of types I and III ADHs in ethanol metabolism can be considered as incidental, and not adaptive.