Diversity and abundance of phlebotomine of the genus Lutzomyia (Diptera: Psychodidae) in areas of forest in the northeast of Manacapuru, Amazonas State, Brazil

The genus Lutzomyia has great importance in the New World, with some species implicated in the transmission of causal agents of leishmaniases, bartonellosis and arboviruses. From April 2003 to June 2004 an investigation was undertaken on the richness and abundance of the sand fly fauna in the northeast area of Manacapuru county, Amazonas State. The captures were carried out, with 16 light traps CDC, in areas of forest known as terra firme along the highway Manuel Urbano. In the period of 13 months we collected a total of 10,446 sandfly specimens, 3,908 males (38%) and 6,465 females (62%), distributed in 43 species belonging to the genus Lutzomyia, 10 subgenera and six species groups. These results evidenced a diversified and abundant sand fly fauna, with some species not yet reported for Manaus county, close to the study area.     

Conservation of pBuM–2 satellite DNA sequences among geographically isolated Drosophila gouveai populations from Brazil

In this study, we have compared 34 repetition units of pBuM-2 satellite DNA of individuals from six isolated populations of Drosophila gouveai, a cactophilic member of Drosophila buzzatii cluster (repleta group). In contrast to the results of previous morphological and molecular data, which suggest differentiation among the D. gouveai populations, the sequences and the cluster analysis of pBuM-2 monomers showed that this repetitive element is highly conserved among the six D. gouveai populations (97.8% similarity), indicating a slow rate of evolution of pBuM-2 sequences at the population level. Probably, some homogenization mechanisms of tandem sequences, such as unequal crossing or gene conversion, have maintained the sequence similarity of pBuM-2 among D. gouveai populations. Alternatively, such a result may be associated with a functional role of pBuM-2 sequences, although it is not understood at present.     

Response surface methodology as an approach to determine the optimal activities of xylose reductase and xylitol dehydrogenase enzymes from Candida Mogii

A central composite experimental design leading to a set of 16 experiments with different combinations of pH and temperature was performed to attain the optimal activities of xylose reductase (XR) and xylitol dehydrogenase (XDH) enzymes from Candida mogii cell extract. Under optimized conditions (pH 6.5 and 38°C), the XR and XDH activities were found to be 0.48 U/ml and 0.22 U/ml, respectively, resulting in an XR to XDH ratio of 2.2. Stability, cofactor specificity and kinetic parameters of the enzyme XR were also evaluated. XR activity remained stable for 3 h under 4 and 38°C and for 4 months of storage at −18°C. Studies on cofactor specificity showed that only NADPH-dependent XR was obtained under the cultivation conditions employed. The XR present in C. mogii extracts showed a superior K _m value for xylose when compared with other yeast strains. Besides, this parameter was not modified after enzyme extraction by aqueous two-phase system.     

Calpain-mediated proteolysis of talin regulates adhesion dynamics

Dynamic regulation of adhesion complexes is required for cell migration and has therefore emerged as a key issue in the study of cell motility. Recent progress has been made in defining some of the molecular mechanisms by which adhesion disassembly is regulated, including the contributions of adhesion adaptor proteins and tyrosine kinases. However, little is known about the potential contribution of proteolytic mechanisms to the regulation of adhesion complex dynamics. Here, we show that proteolysis of talin by the intracellular calcium-dependent protease calpain is critical for focal adhesion disassembly. We have generated a single point mutation in talin that renders it resistant to proteolysis by calpain. Quantification of adhesion assembly and disassembly rates demonstrates that calpain-mediated talin proteolysis is a rate-limiting step during adhesion turnover. Furthermore, we demonstrate that disassembly of other adhesion components, including paxillin, vinculin and zyxin, is also dependent on the ability of calpain to cleave talin, suggesting a general role for talin proteolysis in regulating adhesion turnover. Together, these findings identify calpain-mediated proteolysis of talin as a mechanism by which adhesion dynamics are regulated.     

Forecasting airborne pollen concentrations: Development of local models

People's sensitivity to allergies may representone of the most important health factors of thenext century to which attention must be paid inorder to reduce the incidence of social costsand improve the quality of life.Taking into consideration the earnest requestsof the medical-scientific communityEmilia-Romagna ARPA (Regional Agency for thePrevention of the Environment) moved theattention from the monitoring to a short andmedium term prediction of the concentration ofallergenic pollens in the air in order toachieve a more effective therapeutic action.Our main objectives are to improve seasonalforecasts and to interpret anomalous years.A neural network model for grass pollenforecasting has been implemented. Inputvariables were meteorological situations, i.e.,daily temperature (max., min. and average) andrainfall, in addition to combinations ofindividual variables and their thresholds. Theoutput was daily pollen concentration.The model was able to understand and predictanomalous years. We demonstrate that therelationships between pollen concentrations andmeteorological situations are independent fromsite. This means that such models canunderstand the differences in differentareas.     

Excitatory glutamate is essential for development and maintenance of the piloneural mechanoreceptor

The piloneural collar in mammalian hairy skin comprises an intricate pattern of circumferential and longitudinal sensory afferents that innervate primary and secondary pelage hairs. The longitudinal afferents tightly associate with terminal Schwann cell processes to form encapsulated lanceolate nerve endings of rapidly adapting mechanoreceptors. The molecular basis for piloneural development, maintenance and function is poorly understood. Here, we show that Nefh-expressing glutamatergic neurons represent a major population of longitudinal and circumferential sensory afferents innervating the piloneural collar. Our findings using a VGLUT2 conditional-null mouse model indicate that glutamate is essential for innervation, patterning and differentiation of NMDAR(+) terminal Schwann cells during piloneural collar development. Similarly, treatment of adult mice with a selective NMDAR antagonist severely perturbed piloneural collar structure and reduced excitability of these mechanosensory neurons. Collectively, these results show that DRG-derived glutamate is essential for the proper development, maintenance and sensory function of the piloneural mechanoreceptor.     

Comparative cytogenetics of three economically important Piper L. species from the Brazilian Amazon

The species Piper hispidinervum, Piper aduncum, and Piper affinis hispidinervum have essential oils with high levels of safrole, dillapiole, and sarisan, respectively. Safrole is important for pharmaceutical and chemical industries, while dillapiole and sarisan are promising compounds to control insects and fungi. These species are very similar morphologically and their taxonomy is controversial. Divergent hypotheses consider P. aduncum and P. hispidinervum either as a single species or as distinct taxa, while P. affinis hispidinervum is inferred to be a natural hybrid or a chemotype of P. hispidinervum. Delimiting the taxonomic boundaries would be helpful for germplasm conservation and breeding programs. This study aimed to undertake a detailed analysis of P. aduncum, P. hispidinervum, and P. affinis hispidinervum karyotype and rDNA sites. Genomic in situ hybridization (GISH) was used to establish genomic homology among species and to test the natural hybridization hypothesis for origin of P. affinis hispidinervum. Karyotype traits were similar for all three species: 2n = 26 small chromosomes, predominantly metacentric. All three species exhibited CMA+ bands on the secondary constriction of chromosome pair 4. A size-heteromorphic 35S rDNA site was co-localized with the CMA+ band. A 5S rDNA site was located in the proximal region of chromosome pair 7. The patterns of genomic hybridization revealed that the repetitive DNA fraction of the species is highly similar in terms of proportion of genome, sequence type, and distribution. Our findings did not allow us to differentiate the three species and point to the importance of deeper genomic studies to elucidate the taxonomic controversy.

     

Inhibition of net nitrification activity in a Mediterranean woodland: possible role of chemicals produced by Arbutus unedo

Nitrification is a key biological process for the control of soil NO₃ ^? availability and N losses from terrestrial ecosystems. The study investigates the causes for the absence of net nitrification activity in the soil of a Mediterranean monospecific woodland of Arbutus unedo, focusing in particular on the possible role of chemicals produced by this plant. The mineral N pool, net rates of mineralization and nitrification were measured in the soil top 10 cm over 18 months. Raw extracts of leaves and roots of Arbutus unedo and soil underneath Arbutus plant canopy were purified using chromatographic techniques and the structure of chemicals was defined using spectroscopic and spectrometric methods. Leaf extracts (raw, aqueous and organic fractions) were tested for their toxicity on net nitrification, using a test soil. Field and laboratory incubations showed soil NO₃ ^? concentration below the detection limit over the whole study period, despite the significant NH₄ ⁺ availability. Toxicity tests indicated that more than 400 μg of extract g^?1 dry soil were needed to have more than 50% reduction of net NO₃ ^? production. Gallocatechin and catechin were among the most abundant chemicals in the extracts of leaves, roots and soil. Their soil concentration was significantly higher than the annual calculated input via leaf litter, and it was in the range of toxic concentrations, as deduced from the dose-response curve of the toxicity test. Data support the hypothesis that plant produced chemicals might be involved in the limited net nitrate production in this Mediterranean woodland.