Managing LTL properties in Event-B refinement

Refinement in Event-B supports the development of systems via proof based step-wise refinement of events. This refinement approach ensures safety properties are preserved, but additional reasoning is required in order to establish liveness and fairness properties. In this paper we present results which allow a closer integration of two formal methods, Event-B and linear temporal logic. In particular we show how a class of temporal logic properties can carry through a refinement chain of machines. Refinement steps can include introduction of new events, event renaming and event splitting. We also identify a general liveness property that holds for the events of the initial system of a refinement chain. The approach will aid developers in enabling them to verify linear temporal logic properties at early stages of a development, knowing they will be preserved at later stages. We illustrate the results via a simple case study

Untersuchungen zur Genexpressionshemmung durch Doppelstrang-RNA-Interferenz in Larven 3 von Lucilia cuprina

Ziel der vorliegenden Arbeit war, die Methodik der RNA-Interferenz (RNAi) auf ein nicht-embryonales Stadium der Goldfliege Lucilia cuprina zu übertragen und damit die Möglichkeit von RNAi als ein molekulares Werkzeug der Target-Identifizierung im Ektoparasiten zu untersuchen. Die Arbeit beinhaltet einen Versuch der Genexpressionshemmung mittels RNAi durch Injektion doppelsträngiger, spezifischer RNA (dsRNA) in L3-Larven von L. cuprina.The objective of this thesis was to investigate RNA-interference (RNAi) as a possible molecular tool of target identification in a non-embryonic stage of an ectoparasite, the Australian blowfly Lucilia cuprina. The thesis describes the RNA-interference induced gene silencing by injection of specific double stranded RNA (dsRNA) into L3-larvae of L. cuprina

The novel isoxazoline ectoparasiticide fluralaner: Selective inhibition of arthropod γ-aminobutyric acid- and l-glutamate-gated chloride channels and insecticidal/acaricidal activity

AbstractIsoxazolines are a novel class of parasiticides that are potent inhibitors of γ-aminobutyric acid (GABA)-gated chloride channels (GABACls) and l-glutamate-gated chloride channels (GluCls). In this study, the effects of the isoxazoline drug fluralaner on insect and acarid GABACl (RDL) and GluCl and its parasiticidal potency were investigated. We report the identification and cDNA cloning of Rhipicephalus (R.) microplus RDL and GluCl genes, and their functional expression in Xenopus laevis oocytes. The generation of six clonal HEK293 cell lines expressing Rhipicephalus microplus RDL and GluCl, Ctenocephalides felis RDL-A285 and RDL-S285, as well as Drosophila melanogaster RDLCl-A302 and RDL-S302, combined with the development of a membrane potential fluorescence dye assay allowed the comparison of ion channel inhibition by fluralaner with that of established insecticides addressing RDL and GluCl as targets. In these assays fluralaner was several orders of magnitude more potent than picrotoxinin and dieldrin, and performed 5-236 fold better than fipronil on the arthropod RDLs, while a rat GABACl remained unaffected. Comparative studies showed that R. microplus RDL is 52-fold more sensitive than R. microplus GluCl to fluralaner inhibition, confirming that the GABA-gated chloride channel is the primary target of this new parasiticide. In agreement with the superior RDL on-target activity, fluralaner outperformed dieldrin and fipronil in insecticidal screens on cat fleas (Ctenocephalides felis), yellow fever mosquito larvae (Aedes aegypti) and sheep blowfly larvae (Lucilia cuprina), as well as in acaricidal screens on cattle tick (R. microplus) adult females, brown dog tick (Rhipicephalus sanguineus) adult females and Ornithodoros moubata nymphs. These findings highlight the potential of fluralaner as a novel ectoparasiticide

A quantitative evaluation of the extent of fluralaner uptake by ticks (Ixodes ricinus, Ixodes scapularis) in fluralaner (Bravecto TM ) treated vs. untreated dogs using the parameters tick weight and coxal index

Background Fluralaner is a new antiparasitic drug that was recently introduced as Bravecto TM chewable tablets for the treatment of tick and flea infestations in dogs. Most marketed tick products exert their effect via topical application and contact exposure to the parasite. In contrast, Bravecto TM delivers its acaricidal activity through systemic exposure. Tick exposure to fluralaner occurs after attachment to orally treated dogs, which induces a tick-killing effect within 12 h. The fast onset of killing lasts over the entire treatment interval (12 weeks) and suggests that only marginal uptake by ticks is required to induce efficacy. Three laboratory studies were conducted to quantify the extent of uptake by comparison of ticks’ weight and coxal index obtained from Bravecto TM -treated and negative-control dogs. Methods Three studies were conducted using experimental tick infestation with either Ixodes ricinus or Ixodes scapularis after oral administration of fluralaner to dogs. All studies included a treated (Bravecto TM chewable tablets, MSD Animal Health) and a negative control group. Each study had a similar design for assessing vitality and weighing of ticks collected from dogs of both groups. Additionally, in one study the coxal index (I. ricinus) was calculated as a ratio of tick’s ventral coxal gap and dorsal width of scutum. Tick weight data and coxal indices from Bravecto TM -treated and negative-control groups were compared via statistical analysis. Results Ticks collected from Bravecto TM -treated dogs weighed significantly less (p ≤ 0.0108) than ticks collected from negative-control dogs, and their coxal index was also significantly lower (p < 0.0001). The difference in tick weights was demonstrated irrespective of the tick species investigated (I. ricinus, I. scapularis). At some assessments the mean tick weights of Bravecto TM -treated dogs were significantly lower than those of unfed pre-infestation (baseline) ticks. The demonstrated tick-killing efficacy was in the range of 94.6 – 100 %. Conclusions Tick weights and coxal indices confirm that a minimal uptake results in a sufficient exposure of ticks to fluralaner (Bravecto TM ) and consequently in a potent acaricidal effect

Two Distinctly HLA-Associated Contiguous Linear Epitopes Uniquely Expressed Within the Islet Antigen 2 Molecule Are Major Autoantibody Epitopes of the Diabetes-Specific Tyrosine Phosphatase-Like Protein Autoantigens

AbstractThe related tyrosine phosphatase-like proteins islet Ag (IA)-2 and IA-2β are autoantigens of type 1 diabetes in humans. Autoantibodies are predominantly against IA-2, and IA-2-specific epitopes are major autoantibody targets. We used the close homology of IA-2 and IA-2β to design chimeras and mutants to identify humoral IA-2-specific epitopes. Two major IA-2 epitopes that are absent from the related autoantigens IA-2β and IA-2Δ 13 splice variant ICA512.bdc were found contiguous to each other within IA-2 juxtamembrane amino acids 611–620 (epitope JM1) and 621–630 (epitope JM2). JM1 and JM2 are recognized by sera from 67% of patients with IA-2 Abs, and relatives of patients with type 1 diabetes having Abs to either JM epitope had a &gt;50% risk for developing type 1 diabetes within 6 years, even in the absence of diabetes-associated HLA genotypes. Remarkably, the presence of Abs to one of these two epitopes was mutually exclusive of the other; JM2 Abs and not JM1 Abs were found in relatives with HLA DR3/4, DR4/13, or DR1/4 genotypes; and the binding of autoantibodies to the JM2 epitope, but not the JM1 epitope, markedly affected proteolysis of IA-2. This is a unique demonstration of HLA-associated B cell responses to epitopes within a single autoantigen in humans and is consistent with modification of Ag processing by specific Ab-influencing peptide presentation by HLA molecules

Prognostic, therapeutic, and mechanistic implications of a mouse model of leukemia evoked by Shp2 (PTPN11) mutations

SummaryThe SH2-containing tyrosine phosphatase Shp2 (PTPN11) is required for growth factor and cytokine signaling. Germline Shp2 mutations cause Noonan Syndrome (NS), which is associated with increased risk of juvenile myelomonocytic leukemia (JMML). Somatic Shp2 mutations occur in sporadic JMML and other leukemias. We found that Shp2 mutants associated with sporadic leukemias transform murine bone marrow cells, whereas NS mutants are less potent in this assay. Transformation requires multiple domains within Shp2 and the Shp2 binding protein Gab2, and is associated with hyperactivation of the Erk, Akt, and Stat5 pathways. Mutant Shp2-transduced BM causes a fatal JMML-like disorder or, less commonly, lymphoproliferation. Shp2 mutants also cause myeloproliferation in Drosophila. Mek or Tor inhibitors potently inhibit transformation, suggesting new approaches to JMML therapy

From 'One Namibia, One Nation' towards 'Unity in Diversity? Shifting representations of culture and nationhood in Namibian Independence Day celebrations, 1990-2010

In 2010 Namibia celebrated its twentieth anniversary of independence from South African rule. The main celebrations in the country’s capital Windhoek became the stage for an impressively orchestrated demonstration of maturing nationhood, symbolically embracing postcolonial policy concepts such as ‘national reconciliation’, ‘unity’ and ‘diversity’. At the same time, nation building in post-apartheid Namibia is characterised by a high degree of social and political fragmentation that manifests itself in cultural and/or ethnic discourses of belonging. Taking the highly significant independence jubilee as our vantage point, we map out a shift of cultural representations of the nation in Independence Day celebrations since 1990, embodied by the two prominent slogans of ‘One Namibia, one Nation’ and ‘Unity in Diversity’. As we will argue, the difficult and at times highly fragile postcolonial disposition made it necessary for the SWAPO government, as primary nation builder, to accommodate the demands of regions and local communities in its policy frameworks. This negotiation of local identifications and national belonging in turn shaped, and continues to shape, the performative dimension of Independence Day celebrations in Namibia.Web of Scienc