Interaction of Bacillus thuringiensis svar. israelensis Cry toxins with binding sites from Aedes aegypti (Diptera: Culicidae) larvae midgut

This work shows in vitro processing of Bacillus thuringiensis svar. isralensis Cry toxins and the capacity of the active fragments to bind the midgut microvilli of Aedes aegypti larvae. Processing of Cry11Aa, Cry4Aa and Cry4Ba yielded double fragments of 38-30, 45-20 and 45-18 kDa, respectively. Competition assays showed that all active (125)I-Cry toxins are able to specifically bind to brush border membrane fractions and they might share a common class of binding sites. The values of IC(50) suggested that toxins do not display high affinity for the receptors from brush border membrane fractions, while dissociation assays showed that binding was irreversible, indicating the insertion of toxins in the cell membrane.     

Evaluation of demineralised,freeze-dried,irradiated bone allografts in the treatment of osseous defects in the oral cavity

Demineralised, freeze-dried bone allografts (DFDBA) have been used extensively by dentists in the treatment of periodontal and periapical osseous defects resulting from inflammatory diseases. Their use in India however, is limited by the availability of quality allografts and the high cost of imported alternatives. A study was conducted to assess the osteogenic potential of DFDBA prepared for the first time in India by the Tata Memorial Hospital (TMH) Tissue Bank. The DFDBA was used in the treatment of osseous defects after removal of periapical lesions associated with devitalised teeth in 10 healthy patients. At the 6-month recall visit all the patients showed a remarkable decrease in the grades of mobility, and 9 out of the 10 patients showed radiographic evidence of complete healing of the osseous defects with evidence of normal bony trabaeculae. These findings indicate that the indigenously prepared DFDBA is a cost effective, biocompatible material with osteogenic potential that can be used effectively in treating osseous defects of periapical lesions associated with non vital teeth.     

Competition between Hardwood Hammocks and Mangroves

A bstract The boundaries between mangroves and freshwater hammocks in coastal ecotones of South Florida are sharp. Further, previous studies indicate that there is a discontinuity in plant predawn water potentials, with woody plants either showing predawn water potentials reflecting exposure to saline water or exposure to freshwater. This abrupt concurrent change in community type and plant water status suggests that there might be feedback dynamics between vegetation and salinity. A model examining the salinity of the aerated zone of soil overlying a saline body of water, known as the vadose layer, as a function of precipitation, evaporation and plant water uptake is presented here. The model predicts that mixtures of saline and freshwater vegetative species represent unstable states. Depending on the initial vegetation composition, subsequent vegetative change will lead either to patches of mangrove coverage having a high salinity vadose zone or to freshwater hammock coverage having a low salinity vadose zone. Complete or nearly complete coverage by either freshwater or saltwater vegetation represents two stable steady-state points. This model can explain many of the previous observations of vegetation patterns in coastal South Florida as well as observations on the dynamics of vegetation shifts caused by sea level rise and climate change.     

Sequence-independent characterization of viruses based on the pattern of viral small RNAs produced by the host

Virus surveillance in vector insects is potentially of great benefit to public health. Large-scale sequencing of small and long RNAs has previously been used to detect viruses, but without any formal comparison of different strategies. Furthermore, the identification of viral sequences largely depends on similarity searches against reference databases. Here, we developed a sequence-independent strategy based on virus-derived small RNAs produced by the host response, such as the RNA interference pathway. In insects, we compared sequences of small and long RNAs, demonstrating that viral sequences are enriched in the small RNA fraction. We also noted that the small RNA size profile is a unique signature for each virus and can be used to identify novel viral sequences without known relatives in reference databases. Using this strategy, we characterized six novel viruses in the viromes of laboratory fruit flies and wild populations of two insect vectors: mosquitoes and sandflies. We also show that the small RNA profile could be used to infer viral tropism for ovaries among other aspects of virus biology. Additionally, our results suggest that virus detection utilizing small RNAs can also be applied to vertebrates, although not as efficiently as to plants and insects.     

Evaluation of light-emitting diodes as attractant for sandflies (Diptera: Psychodidae: Phlebotominae) in northeastern Brazil

Hoover Pugedo light traps were modified for use with green and blue-light-emitting diodes to trap phlebotomine sandflies in northeastern Brazil. A total of 2,267 specimens belonging to eight genera and 15 species were sampled. The predominant species were Nyssomyia whitmani(34.41%) and Micropygomyia echinatopharynx(17.25%).The green LED trap prevailed over the blue and control lights; however, no statistically significant difference could be detected among the three light sources. Even without statistical significance, we suggest using LEDs as an attractant for the capture of sandflies because of several advantages over the conventional method with incandescent lamps.     

How well does presence‐only‐based species distribution modelling predict assemblage diversity? A case study of the Tenerife flora

Prediction error is considered an important problem in species distribution models. To address this issue, we here examined the accuracy of overlays of presence‐only‐based models for many individual species in representing patterns of assemblage diversity. For this purpose, we used a database of 977 160 records of seed plant occurrences on an intensively surveyed, species‐rich island (Tenerife, Canary Islands) for modelling the distribution of all its 841 native plant species individually. The modelling was done using Maxent, one of the best‐performing presence‐only modelling techniques, using various thresholds to convert the estimated suitability values into predicted presence or absence. Distribution models for each individual species were overlaid to predict species richness and composition, which were then compared to the observed values for well‐surveyed grid cells. We found high levels of compositional error, when the best performing suitability threshold for predicting species richness was applied. Our best prediction had a mean species richness error of 24% and a mean compositional error of 60% relative to the observed values for the well‐surveyed cells; >50% of all species were included erroneously in >25% of the well‐surveyed cells. Hence, large quantities of data are not necessarily enough to obtain reliable predictions of assemblage diversity, limiting the usefulness of this methodology in conservation planning.