The history of Seasonally Dry Tropical Forests in eastern South America: inferences from the genetic structure of the tree Astronium urundeuva (Anacardiaceae)

Today, the Seasonally Dry Tropical Forests (SDTF) of eastern South America occur as large, well-defined nuclei (e.g. Caatinga in the northeast) and as smaller enclaves within other vegetations (e.g. Cerrado and Chaco). In order to infer the way the present SDTF distribution was attained, the genetic structure of Astronium urundeuva, a tree confined to SDTF, was assessed using two chloroplast spacers and nine microsatellite loci. Five haplotypes were identified, whose distribution was spatially structured. The distribution of the two most common and divergent haplotypes suggested former vicariance and progressive divergence due to isolation. More recent range expansions of these two lineages subsequently occurred, leading to a secondary contact at the southern limit of the Caatinga SDTF nucleus. The multilocus-Bayesian approach using microsatellites consistently identified three groups of populations (Northeast, Central and Southwest). Isolation by distance was found in Northeast and Southwest groups whereas admixture was detected in the Central group, located at the transition between Caatinga and Cerrado domains. All together, the results support the existence of range expansions and secondary contact in the Central group. This study provides arguments that favour the existence of a previously more continuous formation of SDTF in eastern South America.     

Tree species distribution in canopy gaps and mature forest in an area of cloud forest of the Ibitipoca Range,south-eastern Brazil

The tree community of both canopy gaps and mature forest was surveyed in a 5 ha plot of cloud forest in the Ibitipoca Range, south-eastern Brazil, aiming at: (a) comparing the tree community structure of canopy gaps with that of three strata of the mature forest, and (b) relating the tree community structure of canopy gaps with environmental and biotic variables. All saplings of canopy trees with 1–5 m of height established in 31 canopy gaps found within the plot were identified and measured. Mature forest trees with dbh 3 cm were sampled in four 40×40 quadrats laid on the four soil sites recognised in the local soil catena. All surveyed trees were identified, measured and distributed into three forest strata: understorey (<5 m of height), sub-canopy (5.1–15 m) and canopy (15.1–30 m). The following variables were obtained for each gap: mode of formation, age, soil site, slope grade, size, canopy openness and abundance of bamboos and lianas. A detrended correspondence analysis indicated that the tree community structure of gaps in all soil sites was more similar to that of the mature forest understorey, suggesting that the bank of immatures plays an important role in rebuilding the forest canopy and that gap phases may be important for understorey shade-tolerant species. There was evidence of gap-dependence for establishment for only one canopy tree species. Both canonical correspondence analysis and correlation analysis demonstrated for a number of tree species that the distribution of their saplings in canopy gaps was significantly correlated with two variables: soil site and canopy openness. The future forest structure at each gap is probably highly influenced by both the present structure of the adjacent mature forest and the gap creation event.     

Cellular recruitment and cytokine generation in a rat model of allergic lung inflammation are differentially modulated by progesterone and estradiol

We evaluated the role of estradiol and progesterone in allergic lung inflammation. Rats were ovariectomized (Ovx) and, 7 days later, were sensitized with ovalbumin (OA) and challenged after 2 wk with inhaled OA; experiments were performed 1 day thereafter. Ovx-allergic rats showed reduced cell recruitment into the bronchoalveolar lavage (BAL) fluid relative to sham-Ovx allergic rats, as was observed in intact allergic rats treated with ICI-182,780. Estradiol increased the number of cells in the BAL of Ovx-allergic rats, whereas progesterone induced an additional reduction. Cells of BAL and bone marrow (BM) of Ovx-allergic rats released elevated amounts of IL-10 and reduced IL-1 and TNF-. BM cells of Ovx-allergic rats released increased amounts of IL-10 and lower amounts of IL-4. Estradiol treatment of Ovx-allergic rats decreased the release of IL-10 but increased that of IL-4 by BM cells. Estradiol also caused an increased release of IL-1 and TNF- by BAL cells. Progesterone significantly increased the release of IL-10, IL-1, and TNF- by BAL cells and augmented that of IL-4 by BM cells. Degranulation of bronchial mast cells from Ovx rats was reduced after in vitro challenge, an effect reverted by estradiol but not by progesterone. We suggest that the serum estradiol-to-progesterone ratio might drive cellular recruitment, modulating the pulmonary allergy and profile of release of anti-inflammatory or inflammatory cytokines. The existence of such dual hormonal effects suggests that the hormone therapy of asthmatic postmenopausal women and of those suffering of premenstrual asthma should take into account the possibility of worsening the pulmonary conditions. asthma; eosinophils     

Recombinant renewable polyclonal antibodies

Only a small fraction of the antibodies in a traditional polyclonal antibody mixture recognize the target of interest, frequently resulting in undesirable polyreactivity. Here, we show that high-quality recombinant polyclonals, in which hundreds of different antibodies are all directed toward a target of interest, can be easily generated in vitro by combining phage and yeast display. We show that, unlike traditional polyclonals, which are limited resources, recombinant polyclonal antibodies can be amplified over one hundred million-fold without losing representation or functionality. Our protocol was tested on 9 different targets to demonstrate how the strategy allows the selective amplification of antibodies directed toward desirable target specific epitopes, such as those found in one protein but not a closely related one, and the elimination of antibodies recognizing common epitopes, without significant loss of diversity. These recombinant renewable polyclonal antibodies are usable in different assays, and can be generated in high throughput. This approach could potentially be used to develop highly specific recombinant renewable antibodies against all human gene products.     

Comparison of different delivery systems of DNA vaccination for the induction of protection against tuberculosis in mice and guinea pigs

The great challenges for researchers working in the field of vaccinology are optimizing DNA vaccines for use in humans or large animals and creating effective single-dose vaccines using appropriated controlled delivery systems. Plasmid DNA encoding the heat-shock protein 65 (hsp65) (DNAhsp65) has been shown to induce protective and therapeutic immune responses in a murine model of tuberculosis (TB). Despite the success of naked DNAhsp65-based vaccine to protect mice against TB, it requires multiple doses of high amounts of DNA for effective immunization. In order to optimize this DNA vaccine and simplify the vaccination schedule, we coencapsulated DNAhsp65 and the adjuvant trehalose dimycolate (TDM) into biodegradable poly (DL-lactide-co-glycolide) (PLGA) microspheres for a single dose administration. Moreover, a single-shot prime-boost vaccine formulation based on a mixture of two different PLGA microspheres, presenting faster and slower release of, respectively, DNAhsp65 and the recombinant hsp65 protein was also developed. These formulations were tested in mice as well as in guinea pigs by comparison with the efficacy and toxicity induced by the naked DNA preparation or BCG. The single-shot prime-boost formulation clearly presented good efficacy and diminished lung pathology in both mice and guinea pigs.     

Spatio-temporal patterns of tree community dynamics in a tropical forest fragment in South-east Brazil

The tree community (dbh > 5 cm) of a fragment of tropical montane semi-deciduous forest in South-east Brazil was repeatedly surveyed over a 19-year period in order to assess spatial and temporal patterns of dynamics. The surveys took place in 1987, 1992, 1996, 2001, and 2006 in a grid of 126 20 × 20 m permanent plots covering almost the entire fragment (5.8 ha). Overall patterns indicated that a self-thinning process has taken place in the fragment since 1992. Community dynamics varied in space and time, with most dynamics highly spatially clustered. With exception of mortality rates, there were no changes in the spatial patterns of community dynamics through time. No relation between edges and dynamics variables was found. Most species with increasing density and basal area were shade-bearers, while most decreasing species were canopy light demanders and pioneers.     

Resorption of endometrial collagen in oophorectomized rats

Uteri of rats that had been either oophorectomized or given a single dose of 17 beta-diethylstilbestrol or progesterone were studied as to the ultrastructural features of collagen resorption by the fibroblasts of the endometrial stroma. Electron microscopy showed several cytoplasmic vesicles within fibroblasts containing collagenous fibrils in various stages of breakdown. These findings suggest that fibroblasts have a collagenolytic action. Hence, this cell type may play a dual role in the metabolism of endometrial collagen - firstly being responsible for its synthesis, and secondly participating in its resorption.