993 resultados para 04071035 CTD-52
Resumo:
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Resumo:
Contiene resumenes bibliograficos de documentos sobre poblacion y temas relacionados que se producen en America Latina y el Caribe, publicados entre 1978-1981.
Resumo:
Background: Natural polyploidy has played an important role during the speciation and evolution of vertebrates, including anurans, with more than 55 described cases. The species of the Phyllomedusa burmeisteri group are mostly characterized by having 26 chromosomes, but a karyotype with 52 chromosomes was described in P. tetraploidea. This species was found in sintopy with P. distincta in two localities of São Paulo State (Brazil), where triploid animals also occur, as consequence of natural hybridisation. We analyse the chromosomes of P. distincta, P. tetraploidea, and their triploid hybrids, to enlighten the origin of polyploidy and to obtain some evidence on diploidisation of tetraploid karyotype.Results: Phyllomedusa distincta was 2n = 2x = 26, whereas P. tetraploidea was 2n = 4x = 52, and the hybrid individuals was 2n = 3x = 39. In meiotic phases, bivalents were observed in the diploid males, whereas both bivalents and tetravalents were observed in the tetraploid males. Univalents, bivalents or trivalents; metaphase II cells carrying variable number of chromosomes; and spermatids were detected in the testis preparations of the triploid males, indicating that the triploids were not completely sterile. In natural and experimental conditions, the triploids cross with the parental species, producing abnormal egg clutches and tadpoles with malformations. The embryos and tadpoles exhibited intraindividual karyotype variability and all of the metaphases contained abnormal constitutions. Multiple NORs, detected by Ag-impregnation and FISH with an rDNA probe, were observed on chromosome 1 in the three karyotypic forms; and, additionally, on chromosome 9 in the diploids, mostly on chromosome 8 in the tetraploids, and on both chromosome 8 and 9 in the triploids. Nevertheless, NOR-bearing chromosome 9 was detected in the tetraploids, and chromosome 9 carried active or inactive NORs in the triploids. C-banding, base-specific fluorochrome stainings with CMA3 and DAPI, FISH with a telomeric probe, and BrdU incorporation in DNA showed nearly equivalent patterns in the karyotypes of P. distincta, P. tetraploidea, and the triploid hybrids.Conclusions: All the used cytogenetic techniques have provided strong evidence that the process of diploidisation, an essential step for stabilising the selective advantages produced by polyploidisation, is under way in distinct quartets of the tetraploid karyotype. © 2013 Gruber et al.; licensee BioMed Central Ltd.
Resumo:
Foreign Investment in Latin America and the Caribbean Increased in 2006 Investment and Corporate Strategies of Korea and Portugal in Latin America and the Caribbean Op ed by ECLAC's Executive Secretary, José Luis Machinea: The Challenge of Attracting Quality Foreign Direct Investment Highlights.Towards the 10th Regional Conference on Women in Latin America and the Caribbean Indicators The Risks and Opportunities of Bioenergy Recent titles Calendar of events
Resumo:
Crecen flujos de inversión extranjera hacia AméricaLatina y el Caribe en 2006 Inversiones y estrategias empresariales de Corea y Portugal en América Latinay el Caribe Columna de opinión del Secretario Ejecutivo de la CEPAL, José Luis Machinea: El desafío de captar inversión extranjera directa de calidad Precisiones.Hacia la Décima ConferenciaRegional sobre la Mujer de América Latina y el Caribe Indicadores Oportunidades y riesgosde la bioenergía Publicaciones recientes y calendario de eventos
