Shape and size variation on the wing of <Emphasis Type="Italic">Drosophila mediopunctata</Emphasis>: influence of chromosome inversions and genotype-environment interaction

The second chromosome of Drosophila mediopunctata is highly polymorphic for inversions. Previous work reported a significant interaction between these inversions and collecting date on wing size, suggesting the presence of genotype-environment interaction. We performed experiments in the laboratory to test for the joint effects of temperature and chromosome inversions on size and shape of the wing in D. mediopunctata. Size was measured as the centroid size, and shape was analyzed using the generalized least squares Procrustes superimposition followed by discriminant analysis and canonical variates analysis of partial warps and uniform components scores. Our findings show that wing size and shape are influenced by temperature, sex, and karyotype. We also found evidence suggestive of an interaction between the effects of karyotype and temperature on wing shape, indicating the existence of genotype-environment interaction for this trait in D. mediopunctata. In addition, the association between wing size and chromosome inversions is in agreement with previous results indicating that these inversions might be accumulating alleles adapted to different temperatures. However, no significant interaction between temperature and karyotype for size was found--in spite of the significant presence of temperature-genotype (cross) interaction. We suggest that other ecological factors--such as larval crowding--or seasonal variation of genetic content within inversions may explain the previous results.     

Adaptations in phytoplankton life strategies to imposed change in a shallow urban tropical eutrophic reservoir,Garças Reservoir,over 8 years

This study aimed at evaluating the phytoplankton adaptive strategies of phytoplankton in a shallow urban eutrophic tropical reservoir, Garças Reservoir, over temporal and vertical scales. Samples were taken monthly for eight consecutive years (1997–2004) at a fixed set of depths in the water column. At the beginning, the reservoir was eutrophic with 20% of its surface covered by water hyacinth Eichhornia crassipes (phase I). Then, in phase II, water hyacinth grew to cover up to 40–70% of the surface. In phase III it was mechanically removed. After macrophyte removal the limnology changed, drastically. This removal modified nutrient dynamics, drastically reduced water transparency, and increased both primary production and phytoplankton biomass, the latter impeding light penetration. Phytoplankton life strategies during water hyacinth dominance (phase II) responded promptly to this environmental disturbance in conditions of low dissolved oxygen (DO) and soluble reactive phosphorus (SRP) and high free CO₂ values. After macrophyte removal, a permanent cyanobacterial monoculture was established. Phase I was dominated basically by Sphaerocavum brasiliense, mainly during the stratified months, represented by non-flagellate colonies, the M functional group, S-strategists, and greater biomass of species with high maximal axial linear dimension (MLD) and cell volumes. Phase II was dominated by Cryptomonas curvata, C. erosa, C. marssonii, Trachelomonas sculpta, T. volvocinopsis, T. kelloggii, T. hispida, Peridinium spp., Aphanocapsa spp., and Aphanothece spp., and was represented by unicellular flagellate species, Y, W2, K, L_O functional groups, and C-strategists, greater biomass of species with intermediate MLD and cell volumes. Phase III was dominated by Microcystis aeruginosa, M. panniformis, Cylindrospermopsis raciborskii, Planktothrix agardhii, and Aphanizomenon gracile, represented by non-flagellate colonies, M, S, H1, S functional groups, and S and R-strategists, greater biomass of species with high MLD and cell volumes (>50 μm and >10⁴ μm³, respectively).     

S-nitrosylation of syntaxin 1 at Cys(145) is a regulatory switch controlling Munc18-1 binding

Exocytosis is regulated by NO in many cell types, including neurons. In the present study we show that syntaxin 1a is a substrate for S-nitrosylation and that NO disrupts the binding of Munc18-1 to the closed conformation of syntaxin 1a in vitro. In contrast, NO does not inhibit SNARE {SNAP [soluble NSF (N-ethylmaleimide-sensitive fusion protein) attachment protein] receptor} complex formation or binding of Munc18-1 to the SNARE complex. Cys(145) of syntaxin 1a is the target of NO, as a non-nitrosylatable C145S mutant is resistant to NO and novel nitrosomimetic Cys(145) mutants mimic the effect of NO on Munc18-1 binding in vitro. Furthermore, expression of nitrosomimetic syntaxin 1a in living cells affects Munc18-1 localization and alters exocytosis release kinetics and quantal size. Molecular dynamic simulations suggest that NO regulates the syntaxin-Munc18 interaction by local rearrangement of the syntaxin linker and H3c regions. Thus S-nitrosylation of Cys(145) may be a molecular switch to disrupt Munc18-1 binding to the closed conformation of syntaxin 1a, thereby facilitating its engagement with the membrane fusion machinery.     

Killing of <Emphasis Type="Italic">Paracoccidioides brasiliensis</Emphasis> yeast cells by IFN-γ and TNF-α activated murine peritoneal macrophages: evidence of H<Subscript>2</Subscript>O<Subscript>2</Subscript> and NO effector mechanisms

Paracoccidioidomycosis is a deep mycosis, endemic in Latin America, caused by Paracoccidioides brasiliensis. Macrophage activation by cytokines is the major effector mechanism against this fungus. This work aimed at a better understanding of the interaction between yeast cells-murine peritoneal macrophages and the cytokine signals required for the effective killing of high virulence yeast-form of P. brasiliensis. In addition, the killing effector mechanisms dependent on the generation of reactive oxygen or nitrogen intermediates were investigated. Cell preincubation with IFN-gamma or TNF-alpha, at adequate doses, resulted in effective yeast killing as demonstrated in short-term (4-h) assays. Both, IFN-gamma and TNF-alpha activation were associated with higher levels of H(2)O(2) and NO when compared to nonactivation. Treatment with catalase (CAT), a H(2)O(2 )scavenger, and N(G)-monomethyl-L: -arginine (L: -NMMA), a nitric oxide synthase inhibitor, reverted the killing effect of activated cells. Taken together, these results suggest that both oxygen and L: -arginine-nitric oxide pathways play a role in the killing of highly virulent P. brasiliensis.     

Fungicidal activity of human monocyte-derived multinucleated giant cells induced in vitro by Paracoccidioides brasiliensis antigen

Multinucleated giant cells (MGC) are characteristic cells in granulomatous disorders such as paracoccidioidomycosis (PCM) and also are formed in vitro from peripheral blood mononuclear cells by several stimuli. In this study, the authors investigated in vitro formation of MGC derived from monocytes of healthy individuals, stimulated with Paracoccidioides brasiliensis antigen (PbAg), compared with other stimuli such as IFN-gamma and supernatant of Con-A-stimulated peripheral blood mononuclear cells (CM-ConA). Besides, the fungicidal activity of monocytes and monocyte-derived MGC challenged with P. brasiliensis were compared, at a ratio of one fungus per 50 monocytes. Results demonstrated that PbAg, IFN-gamma, and CM-ConA stimuli were able to induce MGC generation, with fusion indices significantly higher than control cultures. Striking results were observed when MGC induced by PbAg and IFN-gamma presented higher fungicidal activity than monocytes, submitted to the same stimuli, showing a better capacity of these cells to kill P. brasiliensis. In summary, the results suggest that PbAg is able to induce MGC generation, and these cells presented higher fungicidal activity against P. brasiliensis than monocytes.     

Simvastatin inducing PC3 prostate cancer cell necrosis mediated by calcineurin and mitochondrial dysfunction

In the present study we analyzed the mechanisms of simvastatin toxicity for the PC3 human prostate cancer cell line. At 10 μM, simvastatin induced principally apoptosis, which was prevented by mevalonic acid but not by cyclosporin A, the inhibitor of calcineurin and mitochondrial permeability transition (MPT). At 60 μM, simvastatin induced the necrosis of PC3 cells insensitive to mevalonic acid. Cell necrosis was preceded by a threefold increase in cytosolic free Ca²⁺ concentration and a significant decrease in both respiration rate and mitochondrial membrane potential. Both mitochondrial dysfunction and necrosis were sensitive to the compounds cyclosporin A and bongkrekic acid, as well as the calcineurin inhibitor FK506. We have concluded that simvastatin-induced PC3 cells apoptosis is dependent on 3-hydroxy-3-methylglutaryl coenzyme-A reductase inhibition and independent of MPT, whereas necrosis is dependent on mitochondrial dysfunction caused, at least in part, by calcineurin.     

Molecular basis for porcine parvovirus detection in dead fetuses

Reproductive failures are still common grounds for complaint by commercial swine producers. Porcine parvovirus (PPV) is associated with different clinical reproductive signs. The aim of the present study was to investigate PPV fetal infection at swine farms having ongoing reproductive performance problems. The presence of virus in fetal tissues was determined by nested-polymerase chain reaction assay directed to the conserved NS1 gene of PPV in aborted fetuses, mummies and stillborns. Fetuses show a high frequency of PPV infection (96.4%; n = 28). In 60.7% of the fetuses, PPV were detected in all tissue samples (lung, heart, thymus, kidney, and spleen). Viral infection differed among fetal tissues, with a higher frequency in the lung and heart (p < 0.05). Fetuses with up to 99 days of gestational age and from younger sows showed a higher frequency of PPV (p < 0.05). No significant difference in the presence of PPV was detected among the three clinical presentations. The results suggest that PPV remains an important pathogenic agent associated with porcine fetal death.     

Citrus somatic hybridization with potential for improved blight and CTV resistance

Summary The production of five new somatic hybrids with potential for improved disease resistance is reported herein. Protoplast isolation, fusion, and plant regeneration was achieved from Caipira sweet orange (Citrus sinensis L. Osbeck) as an embryogenic parental source and Volkamer lemon (C. volkameriana Pasquale), Cleopatra mandarin (C. reticulata Blanco), and Rough lemon (C. jambhiri Lushington) as non-embryogenic parental sources. Fusion involving Cleopatra mandarin and Rangpur lime (C. limonia L. Osbeck) as embryogenic parental sources with Sour orange (C. aurantium L.) also resulted in somatic hybrid plants. Somatic hybridization was confirmed by leaf morphology evaluation, chromosome counting, and randomly amplified polymorphic DNA (RAPD) analyses. Somatic hybrids may combine complementary characteristics from both parental sources and have potential for tolerance to blight and citrus tristeza virus (CTV).