Use of statistical tools in the study of the conditions of predation of Duddingtonia flagrans versus Panagrellus sp

The objective of the present work was to study the conditions of predation of Duddingtonia flagrans conidia versus Panagrellus sp using response surface methodology. Conidia of D. flagrans (AC001) isolate were transferred into water-agar (WA) culture media at different pHs and different concentrations defined according to Central Composite Design (CCD). Five different concentrations of D. flagrans conidia: (1292, 500, 1000, 1500 and 1707) were used. For 2%WA media were used the following pHs were used: 6.29, 6.5, 7.0, 7.5 and 7.71. The response of the design corresponded to the number of larvae (transformed to square root scale) observed at the end of the experiment (10 days). At the tenth day, the non predated larvae were recovered in the Petri dishes. The results showed that 2%WA media at pH 7.0 contributed to improve the predatory activity of conidia of D. flagrans, and therefore this tool may be used in future studies under laboratory and natural conditions.     

Synergistic control of CO2 emissions by fish and nutrients in a humic tropical lake

Using experimental mesocosms, we tested the strength of bottom–up controls by nutrients and top–down controls by an omnivorous fish (Hyphessobrycon bifasciatus; family Characidae), and the interaction between them on the CO₂ partial pressure (pCO₂) in the surface waters of a tropical humic lake (Lake Cabiúnas, Brazil). The experiment included the addition of nutrients and fish to the mesocosms in a factorial design. Overall, persistent CO₂ emissions to the atmosphere, supported by an intense net heterotrophy, were observed in all treatments and replicates over the 6-week study period. The CO₂ efflux (average ± standard error) integrated over the experiment was similar among the control mesocosms and those receiving only fish or only nutrients (309 ± 2, 303 ± 16, and 297 ± 17 mmol CO₂ m⁻² day⁻¹, respectively). However, the addition of nutrients in the presence of fish resulted in a high algal biomass and daytime net autotrophy, reducing the CO₂ emissions by 35% (by 193 ± 7 mmol CO₂ m⁻² day⁻¹). These results indicate that high CO₂ emissions persist following the eutrophication of humic waters, but that the magnitude of these emissions might depend on the structure of the food web. In conclusion, fish and nutrients may act in a synergistic manner to modulate persistent CO₂ emissions from tropical humic lakes.     

Comparative incidence of cancer in HIV-AIDS patients and transplant recipients

BackgroundStudies have found a relationship between decreased immunity and increased incidence of cancer.MethodsA systematic review of observational studies evaluating the incidence of cancer in both organ recipients and people with HIV/AIDS compared with the general population. Eligible studies were searched up to March 2011 in the following databases: Pubmed, Embase, Scielo, Cancerlit and Google scholar. In this study, the standardized incidence ratios (SIR) of cancer in people with HIV/AIDS and of organ transplant recipients were compared with those found among the general population.ResultsTwenty-five studies of transplant and HIV-associated cancer risk, involving 866 776 people with HIV/AIDS or organ recipients and 21 260 new cases of cancer, were included. The risk for the development of new cancer cases was higher among people with HIV/AIDS (SIR = 4, IC95% 3.78–4.24) and who received organs (SIR = 3.28, IC95% 3.06–3.52) when compared with the general population.ConclusionSimilar SIR in both immunocompromised populations suggests that the weakened immune system is responsible for the increased risk of new cases of cancer among these groups. Research investments are needed to develop effective cancer prevention strategies in these populations.     

Neutrophil paralysis in Plasmodium vivax malaria

Background

The activation of innate immune responses by Plasmodium vivax results in activation of effector cells and an excessive production of pro-inflammatory cytokines that may culminate in deleterious effects. Here, we examined the activation and function of neutrophils during acute episodes of malaria.

Materials and Methods

Blood samples were collected from P. vivax-infected patients at admission (day 0) and 30–45 days after treatment with chloroquine and primaquine. Expression of activation markers and cytokine levels produced by highly purified monocytes and neutrophils were measured by the Cytometric Bead Assay. Phagocytic activity, superoxide production, chemotaxis and the presence of G protein-coupled receptor (GRK2) were also evaluated in neutrophils from malaria patients.

Principal Findings

Both monocytes and neutrophils from P. vivax-infected patients were highly activated. While monocytes were found to be the main source of cytokines in response to TLR ligands, neutrophils showed enhanced phagocytic activity and superoxide production. Interestingly, neutrophils from the malaria patients expressed high levels of GRK2, low levels of CXCR2, and displayed impaired chemotaxis towards IL-8 (CXCL8).

Conclusion

Activated neutrophils from malaria patients are a poor source of pro-inflammatory cytokines and display reduced chemotactic activity, suggesting a possible mechanism for an enhanced susceptibility to secondary bacterial infection during malaria.     

Caloric restriction modifies both innate and adaptive immunity in the mouse small intestine

Although caloric restriction (CR) apparently has beneficial effects on the immune system, its effects on the immunological function of the intestinal mucosa are little known. The present study explored the effect of CR on the innate and adaptive intestinal immunity of mice. Balb/c mice were either fed ad libitum (control) or on alternate days fed ad libitum and fasted (caloric restriction). After 4 months, an evaluation was made of IgA levels in the ileum, the gene expression for IgA and its receptor (pIgR), as well as the expression of two antimicrobial enzymes (lysozyme and phospholipase A2) and several cytokines of the intestinal mucosa. CR increased the gene expression of lysozyme and phospholipase A2. The levels of IgA were diminished in the ileum, which apparently was a consequence of the reduced transport of IgA by pIgR. In ileum, CR increased the gene expression for most cytokines, both pro- and anti-inflammatory. Hence, CR differentially modified the expression of innate and adaptive immunity mediators in the intestine.     

Mapping the interactions between a RUN domain from DENND5/Rab6IP1 and sorting nexin 1

Eukaryotic cells have developed a diverse repertoire of Rab GTPases to regulate vesicle trafficking pathways. Together with their effector proteins, Rabs mediate various aspects of vesicle formation, tethering, docking and fusion, but details of the biological roles elicited by effectors are largely unknown. Human Rab6 is involved in the trafficking of vesicles at the level of Golgi via interactions with numerous effector proteins. We have previously determined the crystal structure of Rab6 in complex with DENND5, alternatively called Rab6IP1, which comprises two RUN domains (RUN1 and RUN2) separated by a PLAT domain. The structure of Rab6/RUN1-PLAT (Rab6/R1P) revealed the molecular basis for Golgi recruitment of DENND5 via the RUN1 domain, but the functional role of the RUN2 domain has not been well characterized. Here we show that a soluble DENND5 construct encompassing the RUN2 domain binds to the N-terminal region of sorting nexin 1 by surface plasmon resonance analyses.     

Sensitive genome-wide screen for low secondary enzymatic activities: the YjbQ family shows thiamin phosphate synthase activity

Contemporary enzymes are highly efficient and selective catalysts. However, due to the intrinsically very reactive nature of active sites, gratuitous secondary reactions are practically unavoidable. Consequently, even the smallest cell, with its limited enzymatic repertoire, has the potential to carry out numerous additional, very likely inefficient, secondary reactions. If selectively advantageous, secondary reactions could be the basis for the evolution of new fully functional enzymes. Here, we investigated if Escherichia coli has cryptic enzymatic activities related to thiamin biosynthesis. We selected this pathway because this vitamin is essential, but the cell's requirements are very small. Therefore, enzymes with very low activity could complement the auxotrophy of strains deleted of some bona fide thiamin biosynthetic genes. By overexpressing the E. coli's protein repertoire, we selected yjbQ, a gene that complemented a strain deleted of the thiamin phosphate synthase (TPS)-coding gene thiE. In vitro studies confirmed TPS activity, and by directed evolution experiments, this activity was enhanced. Structurally oriented mutagenesis allowed us to identify the putative active site. Remote orthologs of YjbQ from Thermotoga, Sulfolobus, and Pyrococcus were cloned and also showed thiamin auxotrophy complementation, indicating that the cryptic TPS activity is a property of this protein family. Interestingly, the thiE- and yjbQ-coded TPSs are analog enzymes with no structural similarity, reflecting distinct evolutionary origin. These results support the hypothesis that the enzymatic repertoire of a cell such as E. coli has the potential to perform vast amounts of alternative reactions, which could be exploited to evolve novel or more efficient catalysts.     

Obtaining and selection of hexokinases-less strains of <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> for production of ethanol and fructose from sucrose

Saccharomyces cerevisiae hexokinase-less strains were produced to study the production of ethanol and fructose from sucrose. These strains do not have the hexokinases A and B. Twenty-three double-mutant strains were produced, and then, three were selected for presenting a smaller growth in yeast extract–peptone–fructose. In fermentations with a medium containing sucrose (180.3 g L⁻¹) and with cell recycles, simulating industrial conditions, the capacity of these mutant yeasts in inverting sucrose and fermenting only glucose was well characterized. Besides that, we could also see their great tolerance to the stresses of fermentative recycles, where fructose production (until 90 g L⁻¹) and ethanol production (until 42.3 g L⁻¹) occurred in cycles of 12 h, in which hexokinase-less yeasts performed high growth (51.2% of wet biomass) and viability rates (77% of viable cells) after nine consecutive cycles.