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Antileishmanial and antitrypanosomal activity of the cutaneous secretion of Siphonops annulatus
No full textAbstract\ud
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Background\ud
Among the tropical parasitic diseases, those caused by protozoans are considered a challenge to public health, being represented by leishmaniasis and Chagas disease. In view of the low effectiveness and toxicity of the current therapy, animal venoms such as amphibian secretions have been used as a promising source of new drug prototypes. The present work aimed to achieve bioguided fractionation of metabolites present in a cutaneous secretion of the caecilian Siphonops annulatus (Amphibia: Gymnophiona: Siphonopidae) with antileishmanial and antitrypanosomal activity.\ud
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Methods\ud
Through liquid-liquid partition and chromatographic techniques, the secretion was fractionated using bioguided assays. The 50% inhibitory concentration (IC50) of the main fraction (SaFr1) was studied against Leishmania (L.) infantum promastigotes and intracellular amastigotes, trypomastigotes of Trypanosoma cruzi and mammalian cells; viability was detected by the colorimetric MTT assay. By using a spectrofluorimetric assay with the probe SYTOX® Green and transmission electron microscopy (TEM), we also investigated the potential damage caused by SaFr1 in the plasma membrane and mitochondria of Leishmania.\ud
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Results\ud
The bioguided assay enabled isolation of a highly purified fraction (SaFr1) with an IC50 of 0.065 μg/mL against promastigotes and 2.75 μg/mL against trypomastigotes. Due to its high toxicity to peritoneal macrophages, SaFr1 showed no selectivity towards the intracellular forms of Leishmania. Ultrastructural studies with Leishmania demonstrated severe mitochondrial damage and the formation of large cytoplasmic vacuoles, leading to the parasite’s death within a few hours. Nevertheless, it caused no alteration in the plasma membrane permeability as detected by the fluorescent probe and TEM.\ud
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Conclusions\ud
The present study demonstrated for the first time the antiparasitic activity of the skin secretion of the caecilian S. annulatus against Leishmania and T. cruzi, confirming that skin secretions of these amphibians, similarly to those of anurans and salamanders, are also potential tools for the development of new drug candidates against neglected diseases.The authors would like to thank the State of São Paulo Research Foundation\ud
(FAPESP) for its funding of this research (grant n. 2008/09260-7) and for the\ud
scholarship for EGP (2009/12236-3). Thanks are also due to the National\ud
Council for Scientific and Technological Development (CNPq) for giving a\ud
scientific production award to AGT, CJ and MMA
Phylogenetic and syntenic data support a single horizontal transference to a Trypanosoma ancestor of a prokaryotic proline racemase implicated in parasite evasion from host defences
No full textAbstract\ud
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Background\ud
Proline racemase (PRAC) enzymes of Trypanosoma cruzi (TcPRAC), the agent of Chagas disease, and Trypanosoma vivax (TvPRAC), the agent of livestock trypanosomosis, have been implicated in the B-cells polyclonal activation contributing to immunosuppression and the evasion of host defences. The similarity to prokaryotic PRAC and the absence in Trypanosoma brucei and Trypanosoma congolense have raised many questions about the origin, evolution, and functions of trypanosome PRAC (TryPRAC) enzymes.\ud
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Findings\ud
We identified TryPRAC homologs as single copy genes per haploid genome in 12 of 15 Trypanosoma species, including T. cruzi and T. cruzi marinkellei, T. dionisii, T. erneyi, T. rangeli, T. conorhini and T. lewisi, all parasites of mammals. Polymorphisms in TcPRAC genes matched T. cruzi genotypes: TcI-TcIV and Tcbat have unique genes, while the hybrids TcV and TcVI contain TcPRACA and TcPRACB from parental TcII and TcIII, respectively. PRAC homologs were identified in trypanosomes from anurans, snakes, crocodiles, lizards, and birds. Most trypanosomes have intact PRAC genes. T. rangeli possesses only pseudogenes, maybe in the process of being lost. T. brucei, T. congolense and their allied species, except the more distantly related T. vivax, have completely lost PRAC genes.\ud
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Conclusions\ud
The genealogy of TryPRAC homologs supports an evolutionary history congruent with the Trypanosoma phylogeny. This finding, together with the synteny of PRAC loci, the relationships with prokaryotic PRAC inferred by taxon-rich phylogenetic analysis, and the absence in trypanosomatids of any other genera or in bodonids or euglenids suggest that a common ancestor of Trypanosoma gained PRAC gene by a single and ancient horizontal gene transfer (HGT) from a Firmicutes bacterium more closely related to Gemella and other species of Bacilli than to Clostridium as previously suggested. Our broad phylogenetic study allowed investigation of TryPRAC evolution over long and short timescales. TryPRAC genes diverged to become species-specific and genotype-specific for T. cruzi and T. rangeli, with resulting genealogies congruent with those obtained using vertically inherited genes. The inventory of TryPRAC genes described here is the first step toward the understanding of the roles of PRAC enzymes in trypanosomes differing in life cycles, virulence, and infection and immune evasion strategies.U.S. National Institutes of Health (NIH)U.S. National Science Foundation (NSF)SENACYT (Secretaría Nacional de Ciencia, Tecnología e Innovación)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP (grant #2013/14622-3, São Paulo Research Foundation)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Universidade de São Paulo (USP
Biogeographic history and cryptic diversity of saxicolous Tropiduridae lizards endemic to the semiarid Caatinga
No full textAbstract\ud
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Background\ud
Phylogeographic research has advanced in South America, with increasing efforts on taxa from the dry diagonal biomes. However, the diversification of endemic fauna from the semiarid Caatinga biome in northeastern Brazil is still poorly known. Here we targeted saxicolous lizards of the Tropidurus semitaeniatus species group to better understand the evolutionary history of these endemic taxa and the Caatinga. We estimated a time-calibrated phylogeny for the species group based on two mitochondrial and two nuclear genes and jointly estimated the species limits and species tree within the group. We also devoted a denser phylogeographic sampling of the T. semitaeniatus complex to explore migration patterns, and the spatiotemporal diffusion history to verify a possible role of the São Francisco River as a promoter of differentiation in this saxicolous group of lizards.\ud
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Results\ud
Phylogenetic analysis detected high cryptic genetic diversity, occurrence of unique microendemic lineages associated with older highlands, and a speciation history that took place during the Pliocene-Pleistocene transition. Species delimitation detected five evolutionary entities within the T. semitaeniatus species group, albeit with low support. Thus, additional data are needed for a more accurate definition of species limits and interspecific relationships within this group. Spatiotemporal analyses reconstructed the geographic origin of the T. semitaeniatus species complex to be located north of the present-day course of the São Francisco River, followed by dispersal that expanded its distribution towards the northwest and south. Gene flow estimates showed higher migration rates into the lineages located north of the São Francisco River.\ud
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Conclusions\ud
The phylogenetic and population structures are intrinsically associated with stable rock surfaces and landscape rearrangements, such as the establishment of drainage basins located to the northern and southern distribution ranges. The T. semitaeniatus complex preserved high genetic diversity during range expansion, possibly as a result of frequent long-distance dispersal events. Our results indicate that both the current course of the São Francisco River and its paleo-courses had an important role in promoting diversification of the Caatinga endemic T. semitaeniatus species group.We thank Fundação de Amparo à Pesquisa do Estado de São Paulo, FAPESP,\ud
(grants 11/50146-6, 03/10335-8, and the Dimensions of Biodiversity Program\ud
[FAPESP (BIOTA, 2013/50297-0), NSF (DOB 1343578), and NASA], and\ud
Conselho Nacional de Desenvolvimento Científico e Tecnológico, CNPq, for\ud
funding this study; Instituto Chico Mendes de Conservação da\ud
Biodiversidade, ICMBio, for collecting permits granted (permanent license\ud
#10126-1); S. Baroni, M. Concistré, and M. Miceno for technical assistance,\ud
and A. Camacho, A. Carnaval, A. Magalhães, C. Nisa, C. M. Carvalho, D.\ud
Borges-Nojosa, D. Loebmann, D. Passos, D. Pavan, D. Vrcibradick, E. Dias,\ud
E. M. X. Freire, E. Santos, F. F. Curcio, G. Skuk, H. B. A. Pinto, H. Zaher, I. Prates,\ud
J. Cassimiro, J. Roscito, L. Carvalho, M. A. Freitas, , M. A. Sena, M. Teixeira Jr.,\ud
R. Amaro, R. Damasceno, R. Recoder, U. Gonçalves, and W. Vieira for help\ud
in the field or tissues samples. FPW thanks the Science Without Borders\ud
Program from CNPq (Fellowship and grant #374307/2012-1), Fundação de\ud
Amparo à Pesquisa do Estado do Amazonas (FAPEAM; PAPE/2013), and\ud
Guarino R. Colli for support at Universidade de Brasília during the\ud
development of this study. RNL is thankful to CNPq (PDJ 50069/2014-6)
Atividades investigativas para o ensino médio por meio do uso de um material didático manipulável
No full textNeste trabalho objetivamos apresentar e discutir sobre um conjunto de atividades didáticas de Matemática para alunos do ensino médio, por meio da utilização de um material didático manipulável (MDM) e da abordagem metodológica de investigação matemática. As atividades foram elaboradas para serem utilizadas com um material dídático manipulável denominado de Tábua Quadriculada Geoplanar. Seguindo uma abordagem qualitativa de investigação, um conjunto dessas atividades, sobre análise combinatória, foi aplicado a alunos do ensino médio em uma escola pública brasileira. Desta aplicação observamos que o material e a abordagem utilizados foram importantes para auxiliar na resolução das atividades, na percepção dos erros cometidos e principalmente na compreensão dos conceitos matemáticos focados. Por fim, com o trabalho apresentado pretendemos também contribuir com proposta de utilização de MDM neste nível de ensino, por meio de abordagens alternativas, tal como a investigação matemática.FAPESP (Fundação de amparo à Pesquisa do Estado de São Paulo/Brasil) (processo 2010/05424-5)PIC/SMA (Programa de Iniciação Científica do Departamento de Matemática do ICMC/USP)Programa de Educação Tutorial em Economia Solidária da UFSCa
Automatic generation of a lexical resource to support semantic role labeling in portuguese
No full textThis paper reports an approach to automatically generate a lexical resource to support incremental semantic role labeling annotation in Portuguese. The data come from the corpus Propbank-Br (Propbank of Brazilian Portuguese) and from the lexical resource of English Propbank, as both share the same structure. In order to enable the strategy, we\ud
added extra annotation to Propbank-Br. This approach is part of a previous decision to invert the process of implementing a Propbank project, by first annotating a core corpus and only then generating a lexical resource to enable further annotation tasks. The reasoning behind such inversion is to explore the task empirically before distributing the annotation task and to provide simultaneously: 1) a first training corpus for SRL in Brazilian Portuguese and 2) annotated examples to composse a lexical resource to support SRL. The main contribution of this paper is to point out to what extent linguistic effort may be reduced, thereby speeding up the construction of a lexical resource to support SRL for less resourced languages. The corpus Propbank-Br, with the extra annotation described herein, is publicly available.Samsung Eletrônica da Amazônia LtdaFAPESPCAPES (process number 151/2013
