Intraguild predation and cannibalism between the predatory mites Neoseiulus neobaraki and N. paspalivorus, natural enemies of the coconut mite Aceria guerreronis

Neoseiulus neobaraki and N. paspalivorus are amongst the most common phytoseiid predators of coconut mite, Aceria guerreronis, found in the spatial niche beneath coconut fruit bracts. Both predators may occur on the same coconut palms in Benin and Tanzania and are therefore likely to interact with each other. Here, we assessed cannibalism and intraguild predation (IGP) of the two predators in the absence and presence of their primary prey A. guerreronis. In the absence of the shared extraguild prey, A. guerreronis, N. neobaraki killed 19 larvae of N. paspalivorus per day and produced 0.36?eggs/female/day, while the latter species killed only 7 larvae of the former and produced 0.35?eggs/female/day. Presence of A. guerreronis only slightly decreased IGP by N. neobaraki but strongly decreased IGP by N. paspalivorus, which consumed 4-7 times less IG prey than N. neobaraki. Resulting predator offspring to IG prey ratios were, however, 4-5 times higher in N. paspalivorus than N. neobaraki. Overall, provision of A. guerreronis increased oviposition in both species. In the cannibalism tests, in the absence of A. guerreronis, N. neobaraki and N. paspalivorus consumed 1.8 and 1.2 conspecific larvae and produced almost no eggs. In the presence of abundant herbivorous prey, cannibalism dramatically decreased but oviposition increased in both N. neobaraki and N. paspalivorus. In summary, we conclude that (1) N. neobaraki is a much stronger intraguild predator than N. paspalivorus, (2) cannibalism is very limited in both species, and (3) both IGP and cannibalism are reduced in the presence of the common herbivorous prey with the exception of IGP by N. neobaraki, which remained at high levels despite presence of herbivorous prey. We discuss the implications of cannibalism and IGP on the population dynamics of A. guerreronis and the predators in view of their geographic and within-palm distribution patterns.     

Sequence-specific base pair mimics are efficient topoisomerase IB inhibitors

Topoisomerase IB controls DNA topology by cleaving DNA transiently. This property is used by inhibitors, such as camptothecin, that stabilize, by inhibiting the religation step, the cleavage complex, in which the enzyme is covalently attached to the 3'-phosphate of the cleaved DNA strand. These drugs are used in clinics as antitumor agents. Because three-dimensional structural studies have shown that camptothecin derivatives act as base pair mimics and intercalate between two base pairs in the ternary DNA-topoisomerase-inhibitor complex, we hypothesized that base pairs mimics could act like campthotecin and inhibit the religation reaction after the formation of the topoisomerase I-DNA cleavage complex. We show here that three base pair mimics, nucleobases analogues of the aminophenyl-thiazole family, once targeted specifically to a DNA sequence were potent topoisomerase IB inhibitors. The targeting was achieved through covalent linkage to a sequence-specific DNA ligand, a triplex-forming oligonucleotide, and was necessary to position and keep the nucleobase analogue in the cleavage complex. In the absence of triplex formation, only a weak binding to the DNA and topoisomerase I-mediated DNA cleavage was observed. The three compounds were equally active once conjugated, implying that the intercalation of the nucleobase upon triplex formation is the essential feature for the inhibition activity.     

On diminutives and plurals in Moroccan Arabic

In Moroccan Arabic, like in many other Afroasiatic languages, certain nouns may have more than one plural form. For instance, t ^? es ^? wera ‘photo’ has plurals t ^? s ^? awer and t ^? s ^? werat. However, their diminutive systematically resorts to -at suffixation in the plural. The aim of this study is twofold. First, it presents an interface approach which aims to determine the structural location of number and capture the empirical contrast between broken and sound plurals. It is argued that the sound plurals are associated with the standard Num projection, whereas the broken plurals are associated lower in the structure with the n projection. Second, it provides a templatic analysis of the diminutive formation, showing that the diminutive and the internal plural markers compete for the same templatic position. External evidence for the analysis is drawn from the phenomenon of emphasis spread. The nP is presented as the maximal domain of emphasis spread in nouns.     

Clinical Efficacy of Simulated Vitreoretinal Surgery to Prepare Surgeons for the Upcoming Intervention in the Operating Room

Purpose

To evaluate the efficacy of the virtual reality training simulator Eyesi to prepare surgeons for performing pars plana vitrectomies and its potential to predict the surgeons’ performance.

Methods

In a preparation phase, four participating vitreoretinal surgeons performed repeated simulator training with predefined tasks. If a surgeon was assigned to perform a vitrectomy for the management of complex retinal detachment after a surgical break of at least 60 hours it was randomly decided whether a warmup training on the simulator was required (n = 9) or not (n = 12). Performance at the simulator was measured using the built-in scoring metrics. The surgical performance was determined by two blinded observers who analyzed the video-recorded interventions. One of them repeated the analysis to check for intra-observer consistency. The surgical performance of the interventions with and without simulator training was compared. In addition, for the surgeries with simulator training, the simulator performance was compared to the performance in the operating room.

Results

Comparing each surgeon’s performance with and without warmup trainingshowed a significant effect of warmup training onto the final outcome in the operating room. For the surgeries that were preceeded by the warmup procedure, the performance at the simulator was compared with the operating room performance. We found that there is a significant relation. The governing factor of low scores in the simulator were iatrogenic retinal holes, bleedings and lens damage. Surgeons who caused minor damage in the simulation also performed well in the operating room.

Conclusions

Despite the large variation of conditions, the effect of a warmup training as well as a relation between the performance at the simulator and in the operating room was found with statistical significance. Simulator training is able to serve as a warmup to increase the average performance.     

Antarctic strict anaerobic microbiota from <Emphasis Type="Italic">Deschampsia antarctica</Emphasis> vascular plants rhizosphere reveals high ecology and biotechnology relevance

The Antarctic soil microbial community has a crucial role in the growth and stabilization of higher organisms, such as vascular plants. Analysis of the soil microbiota composition in that extreme environmental condition is crucial to understand the ecological importance and biotechnological potential. We evaluated the efficiency of isolation and abundance of strict anaerobes in the vascular plant Deschampsia antarctica rhizosphere collected in the Antarctic’s Admiralty Bay and associated biodiversity to metabolic perspective and enzymatic activity. Using anaerobic cultivation methods, we identified and isolated a range of microbial taxa whose abundance was associated with Plant Growth-Promoting Bacteria (PGPB) and presences were exclusively endemic to the Antarctic continent. Firmicutes was the most abundant phylum (73 %), with the genus Clostridium found as the most isolated taxa. Here, we describe two soil treatments (oxygen gradient and heat shock) and 27 physicochemical culture conditions were able to increase the diversity of anaerobic bacteria isolates. Heat shock treatment allowed to isolate a high percentage of new species (63.63 %), as well as isolation of species with high enzymatic activity (80.77 %), which would have potential industry application. Our findings contribute to the understanding of the role of anaerobic microbes regarding ecology, evolutionary, and biotechnological features essential to the Antarctic ecosystem.     

Crystal structure of the retinoblastoma protein N domain provides insight into tumor suppression, ligand interaction, and holoprotein architecture

The retinoblastoma susceptibility protein, Rb, has a key role in regulating cell-cycle progression via interactions involving the central "pocket" and C-terminal regions. While the N-terminal domain of Rb is dispensable for this function, it is nonetheless strongly conserved and harbors missense mutations found in hereditary retinoblastoma, indicating that disruption of its function is oncogenic. The crystal structure of the Rb N-terminal domain (RbN), reveals a globular entity formed by two rigidly connected cyclin-like folds. The similarity of RbN to the A and B boxes of the Rb pocket domain suggests that Rb evolved through domain duplication. Structural and functional analysis provides insight into oncogenicity of mutations in RbN and identifies a unique phosphorylation-regulated site of protein interaction. Additionally, this analysis suggests a coherent conformation for the Rb holoprotein in which RbN and pocket domains directly interact, and which can be modulated through ligand binding and possibly Rb phosphorylation.     

Inhibition of the ubiquitin-proteasome system induces stress granule formation

The inhibition of the ubiquitin-dependent proteasome system (UPS) via specific drugs is one type of approach used to combat cancer. Although it has been suggested that UPS inhibition prevents the rapid decay of AU-rich element (ARE)-containing messages, very little is known about the cellular mechanisms leading to this effect. Here we establish a link between the inhibition of UPS activity, the formation of cytoplasmic stress granules (SGs), and mRNA metabolism. The assembly of the SGs requires the phosphorylation of the translation initiation factor eIF2alpha by a mechanism involving the stress kinase GCN2. On prolonged UPS inhibition and despite the maintenance of eIF2alpha phosphorylation, SGs disassemble and translation recovers in an Hsp72 protein-dependent manner. The formation of these SGs coincides with the disassembly of processing bodies (PBs), known as mRNA decay entities. As soon as the SGs assemble, they recruit ARE-containing messages such as p21(cip1) mRNA, which are stabilized under these conditions. Hence, our findings suggest that SGs could be considered as one of the players that mediate the early response of the cell to proteasome inhibitors by interfering temporarily with mRNA decay pathways.     

Optimization of novel combi-molecules: identification of balanced and mixed bcr-abl/DNA targeting properties

Steps toward the identification of combi-molecules with strong abl tyrosine kinase (TK) inhibitory property and significant DNA damaging potential are described. The optimized combi-molecule 13a was shown to induce approximately twofold stronger abl TK inhibitory activity than Gleevec and high levels of DNA damage in chronic myelogenous leukemic cells.