Relative contribution of rainfall and coconut hybrids to the abundance and composition of the Auchenorrhyncha community as potential vectors of phytoplasmas in the state of Sergipe,Brazil

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Role of Guanine Nucleotide Exchange Factor-H1 in Complement-mediated RhoA Activation in Glomerular Epithelial Cells

Visceral glomerular epithelial cells (GEC), also known as podocytes, are vital for the structural and functional integrity of the glomerulus. The actin cytoskeleton plays a central role in maintaining GEC morphology. In a rat model of experimental membranous nephropathy (passive Heymann nephritis (PHN)), complement C5b-9-induced proteinuria was associated with the activation of the actin regulator small GTPase, RhoA. The mechanisms of RhoA activation, however, remained unknown. In this study, we explored the role of the epithelial guanine nucleotide exchange factor, GEF-H1, in complement-induced RhoA activation. Using affinity precipitation to monitor GEF activity, we found that GEF-H1 was activated in glomeruli isolated from rats with PHN. Complement C5b-9 also induced parallel activation of GEF-H1 and RhoA in cultured GEC. In GEC in which GEF-H1 was knocked down, both basal and complement-induced RhoA activity was reduced. On the other hand, GEF-H1 knockdown augmented complement-mediated cytolysis, suggesting a role for GEF-H1 and RhoA in protecting GEC from cell death. The MEK1/2 inhibitor, U0126, and mutation of the ERK-dependent phosphorylation site (T678A) prevented complement-induced GEF-H1 activation, indicating a role for the ERK pathway. Further, complement induced GEF-H1 and microtubule accumulation in the perinuclear region. However, both the perinuclear accumulation and the activation of GEF-H1 were independent of microtubules and myosin-mediated contractility, as shown using drugs that interfere with microtubule dynamics and myosin II activity. In summary, we have identified complement-induced ERK-dependent GEF-H1 activation as the upstream mechanism of RhoA stimulation, and this pathway has a protective role against cell death.     

Evidence of plant–insect interaction in the Early Cretaceous Flora from the Crato Formation,Araripe Basin,Northeast Brazil

The analysis of insect-plant interaction can be provide paleoecological and paleoenvironmental important data for understanding the co-evolution between plants and insects. Since the appearance of the first evidence of leaves damaged by insects, these organisms have evolved together. In the Araripe Basin, the Crato Formation stands out by having abundance and diversity of fossils species of plants and insects. In this work they are documented interaction records in specimens of ferns, gymnosperms and angiosperms, showing a wide variety of types of interactions. Here we analyze 56 fossil specimens from the collections of the Museum of Paleontology and the Laboratory of Paleontology of the Universidade Regional do Cariri. The types of damage identified in this study is insect galls, leaf margin feeding (herbivory), leaf mines, oviposition of insects and skeletonization, which are present in 19 specimens. This analysis in search for evidences of plant–insect interaction contributes with new interaction patterns for the Crato Formation. Although the low sample rate, the new registers for plant-insect association were compared to records from different cretaceous basins. This suggests new possibilities in the studies for ecological relations and coevolutionary plant-insect during the Cretaceous. In addition, a new type of damage is identified in a pteridophyte.     

Cycle and duration of the seminiferous epithelium in puma (Puma concolor)

Puma or sussuarana (Puma concolor) is the second largest feline in the American continent and has an ample latitudinal distribution in very diverse habitats. In relation to its conservation status, the puma is considered an extinction-threatened species. The study of the testis morphology and the spermatogenic process in a species is fundamental for establishing the physiologic patterns that will make possible the selection of the protocols for assisted reproduction. A number of peculiarities associated with the reproductive biology of specific species such as the duration of spermatogenic process can be used to determine the frequency of sperm collection. Nine adult male pumas maintained in captivity were used to determine the relative frequency of stages in the seminiferous epithelium cycle. Three of them received intra-testicular injections of 0.1ml tritiated thymidine to determine the duration of the seminiferous epithelium cycle, and were subjected to biopsy 7 days later. The cycle of the seminiferous epithelium in puma was didactically described into eight stages by the tubular morphology method. The total duration of one seminiferous epithelium cycle in puma was calculated to be 9.89 days, and approximately 44.5 days are required for development of spermatozoon from spermatogonia. The duration of spermiogenesis, prophase and other events of meiosis were 14.08, 15.20 and 1.79 days, respectively. The relative frequency of the pre-meiotic, meiotic and post-meiotic phases were 3.98, 1.79 and 4.12 days, respectively.     

Deciduousness Influences the Understory Community in a Semideciduous Tropical Forest

We investigated how deciduousness of overstory tree species influences the community structure and species composition in the understory. The results suggest that deciduous overstory trees have positive effects on light‐demanding species, and that the processes underlying such effects may involve reduced competition for light or facilitation through increased water availability.     

Aminoarabinose is essential for lipopolysaccharide export and intrinsic antimicrobial peptide resistance in Burkholderia cenocepacia(†)

One common mechanism of resistance against antimicrobial peptides in Gram‐negative bacteria is the addition of 4‐amino‐4‐deoxy‐l ‐arabinose (l ‐Ara4N) to the lipopolysaccharide (LPS) molecule. Burkholderia cenocepacia exhibits extraordinary intrinsic resistance to antimicrobial peptides and other antibiotics. We have previously discovered that unlike other bacteria, B. cenocepacia requires l ‐Ara4N for viability. Here, we describe the isolation of B. cenocepacia suppressor mutants that remain viable despite the deletion of genes required for l ‐Ara4N synthesis and transfer to the LPS. The absence of l ‐Ara4N is the only structural difference in the LPS of the mutants compared with that of the parental strain. The mutants also become highly sensitive to polymyxin B and melittin, two different classes of antimicrobial peptides. The suppressor phenotype resulted from a single amino acid replacement (aspartic acid to histidine) at position 31 of LptG, a protein component of the multi‐protein pathway responsible for the export of the LPS molecule from the inner to the outer membrane. We propose that l ‐Ara4N modification of LPS provides a molecular signature required for LPS export and proper assembly at the outer membrane of B. cenocepacia, and is the most critical determinant for the intrinsic resistance of this bacterium to antimicrobial peptides.