Gypsy endogenous retrovirus maintains potential infectivity in several species of Drosophilids

Background  

Sequences homologous to the gypsy retroelement from Drosophila melanogaster are widely distributed among drosophilids. The structure of gypsy includes an open reading frame resembling the retroviral gene env, which is responsible for the infectious properties of retroviruses.     

Fragment-based discovery of hepatitis C virus NS5b RNA polymerase inhibitors

Non-nucleoside inhibitors of HCV NS5b RNA polymerase were discovered by a fragment-based lead discovery approach, beginning with crystallographic fragment screening. The NS5b binding affinity and biochemical activity of fragment hits and inhibitors was determined by surface plasmon resonance (Biacore) and an enzyme inhibition assay, respectively. Crystallographic fragment screening hits with 1–10 mM binding affinity (K_D) were iteratively optimized to give leads with 200 nM biochemical activity and low μM cellular activity in a Replicon assay.     

Genotoxicity and mutagenicity of iron and copper in mice

The toxicity of trace metals is still incompletely understood. We have previously shown that a single oral dose of iron or copper induces genotoxic effects in mice in vivo, as detected by single cell gel electrophoresis (comet assay). Here, we report the effect of these metals on subchronic exposure. Mice were gavaged for six consecutive days with either water, 33.2 mg/kg iron, or 8.5 mg/kg copper. On the 7th day, the neutral and alkaline comet assays in whole blood and the bone marrow micronucleus (MN) test were used as genotoxicity and mutagenicity endpoints, respectively. Particle induced X-ray emission was used to determine liver levels of the metals. Females showed a slightly lower DNA damage background, but there was no significant difference between genders for any endpoint. Iron and copper were genotoxic and mutagenic. While copper was more genotoxic in the neutral version, iron was more genotoxic in the alkaline version of the comet assay. Copper induced the highest mutagenicity as evaluated by the MN test. Iron was not mutagenic to male mice. Iron is thought to induce more oxidative lesions than copper, which are primarily detected in the alkaline comet assay. Treatment with iron, but not with copper, induced a significant increase in the hepatic level of the respective metal, reflecting different excretion strategies.     

Imidazolidines as new anti-Trypanosoma cruzi agents: biological evaluation and structure-activity relationships

Imidazolidine derivatives were studied as anti-Trypanosoma cruzi agents. Imidazolines can be considered as ethylenediamine/carbonyl precursors and therefore interfere with the biosynthesis of polyamines into the parasite. Some of the derivatives were found to have high and selective activity against the proliferative stages of the parasite, with IC(50) values against the epimastigote form in the low micromolar range as the reference drug Nifurtimox. The imidazolidines demonstrated to be stable after five days of incubation in buffer glucose, pH 7, indicating that diamines were not obtained in these conditions. But it was found that two of the studied diamine precursors were as active as the parent compounds. Probably, the imidazolidines affect the mitochondrial integrity according to the excreted end-products found in the NMR studies. The QSAR studies indicated that the bioactivities are correlated with the lipophilicities. In conclusion, we have described a new and relevant bioactivity for imidazolidines. The results support further in vivo studies of some of these imidazolidine derivatives.     

Brain oxidative stress in a triple-transgenic mouse model of Alzheimer disease

Alzheimer disease (AD) is a neurodegenerative disease which is characterized by the presence of extracellular senile plaques mainly composed of amyloid-beta peptide (Abeta), intracellular neurofibrillary tangles, and selective synaptic and neuronal loss. AD brains revealed elevated levels of oxidative stress markers which have been implicated in Abeta-induced toxicity. In the present work we addressed the hypothesis that oxidative stress occurs early in the development of AD and evaluated the extension of the oxidative stress and the levels of antioxidants in an in vivo model of AD, the triple-transgenic mouse, which develops plaques, tangles, and cognitive impairments and thus mimics AD progression in humans. We have shown that in this model, levels of antioxidants, namely, reduced glutathione and vitamin E, are decreased and the extent of lipid peroxidation is increased. We have also observed increased activity of the antioxidant enzymes glutathione peroxidase and superoxide dismutase. These alterations are evident during the Abeta oligomerization period, before the appearance of Abeta plaques and neurofibrillary tangles, supporting the view that oxidative stress occurs early in the development of the disease.     

Variability in the behavioural responses of three generalist herbivores to the most abundant coumarin in Daphne laureola leaves

We evaluated the responses of three generalist herbivores (Lepidoptera: Noctuidae) to the most abundant coumarin in young leaves of spurge-laurel, Daphne laureola L. (Thymelaeaceae), a perennial shrub consistently fed upon by several noctuid species. Pseudenargia ulicis Staud and Noctua janthe Borkhausen are natural herbivores of the species in southeastern Spain, whereas Spodoptera littoralis Boisduval is a model species frequently used to address the antifeedant role of secondary compounds. Discrimination between control and coumarin-coated D. laureola leaves was investigated by short-term choice experiments. We found species-specific behavioural responses to the treatment: P. ulicis preferred the control leaves, whereas S. littoralis did not discriminate between leaf treatments, although it clearly avoided coumarin when incorporated into an artificial diet, and N. janthe preferred the coumarin-coated leaves. Furthermore, N. janthe larvae reduced consumption when the proportion of treated leaves ingested increased and consumption of S. littoralis larvae was also reduced in coumarin-containing diet under no-choice conditions. Our results highlight that different herbivore species feeding simultaneously on the same host plant respond differently to a single chemical defence compound, likely constraining a directional response of the plant to selection.     

A comparison of national approaches to setting ecological status boundaries in phytobenthos assessment for the European Water Framework Directive: results of an intercalibration exercise

The European Union (EU)’s Water Framework Directive (WFD) requires that all Member States participate in intercalibration exercises in order to ensure that ecological status concepts and assessment levels are consistent across the EU. This paper describes one such exercise, performed by the countries in the Central/Baltic Geographical Intercalibration Group stretching from Ireland in the west to Estonia in the east and from the southern parts of Scandinavia to the northern regions of Spain and Italy (but excluding alpine regions, which were intercalibrated separately). In this exercise, methods used to measure ecological status of rivers using benthic diatoms were compared. Ecological status is estimated as the ratio between the observed value of a biological element and the value expected in the absence of significant human impact. Approaches to defining the ‘reference sites’, from which these ‘expected’ values were derived, varied from country to country. Minimum criteria were established as part of the exercise but there was still considerable variation between national reference values, reflecting typological differences that could not be resolved during the exercise. A simple multimetric index was developed to compare boundary values using two widely used diatom metrics. Boundary values for high/good status and good/moderate status set by each participant were converted to their equivalent values of this intercalibration metric using linear regression. Variation of ±0.05 EQR units around the median value was considered to be acceptable and the exercise provided a means for those Member States who fell significantly above or below this line to review their approaches and, if necessary, adjust their boundaries. Handling editor: J. Padisak     

Enhancement of insecticidal activity of Bacillus thuringiensis Cry1A toxins by fragments of a toxin-binding cadherin correlates with oligomer formation

Cry1A toxins produced by Bacillus thuringiensis bind a cadherin receptor that mediates toxicity in different lepidopteran insect larvae. Insect cadherin receptors are modular proteins composed of three domains, the ectodomain formed by 9-12 cadherin repeats (CR), the transmembrane domain and the intracellular domain. Cry1A toxins interact with three regions of the Manduca sexta cadherin receptor that are located in CR7, CR11 and CR12 cadherin repeats. Binding of Cry1A toxin to cadherin induces oligomerization of the toxin, which is essential for membrane insertion. Also, it has been reported that cadherin fragments containing the CR12 region enhanced the insecticidal activity of Cry1Ab toxin to M. sexta and other lepidopteran larvae. Here we report that cadherin fragments corresponding to CR7 and CR11 regions also enhanced the activity of Cry1Ac and Cry1Ab toxin to M. sexta larvae, although not as efficient as the CR12 fragment. A single point mutation in the CR12 region (I1422R) affected Cry1Ac and Cry1Ab binding to the cadherin fragments and did not enhance the activity of Cry1Ab or Cry1Ac toxin in bioassays. Analysis of Cry1Ab in vitro oligomer formation in the presence of wild type and mutated cadherin fragments showed a correlation between enhancement of Cry1A toxin activity in bioassays and in vitro Cry1Ab-oligomer formation. Our data shows that formation of Cry1A toxin oligomer is in part responsible for the enhancement of Cry1A toxicity by cadherin fragments that is observed in vivo.