921 resultados para Nansha Islands


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Aplicación de técnicas dendroecológicas para el estudio de avenidas torrenciales.

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Precise mapping of DNA methylation patterns in CpG islands has become essential for understanding diverse biological processes such as the regulation of imprinted genes, X chromosome inactivation, and tumor suppressor gene silencing in human cancer. We describe a new method, MSP (methylation-specific PCR), which can rapidly assess the methylation status of virtually any group of CpG sites within a CpG island, independent of the use of methylation-sensitive restriction enzymes. This assay entails initial modification of DNA by sodium bisulfite, converting all unmethylated, but not methylated, cytosines to uracil, and subsequent amplification with primers specific for methylated versus unmethylated DNA. MSP requires only small quantities of DNA, is sensitive to 0.1% methylated alleles of a given CpG island locus, and can be performed on DNA extracted from paraffin-embedded samples. MSP eliminates the false positive results inherent to previous PCR-based approaches which relied on differential restriction enzyme cleavage to distinguish methylated from unmethylated DNA. In this study, we demonstrate the use of MSP to identify promoter region hypermethylation changes associated with transcriptional inactivation in four important tumor suppressor genes (p16, p15, E-cadherin, and von Hippel-Lindau) in human cancer.

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Woody Sonchus and five related genera (Babcockia, Taeckholmia, Sventenia, Lactucosonchus, and Prenanthes) of the Macaronesian islands have been regarded as an outstanding example of adaptive radiation in angiosperms. Internal transcribed spacer region of the nuclear rDNA (ITS) sequences were used to demonstrate that, despite the extensive morphological and ecological diversity of the plants, the entire alliance in insular Macaronesia has a common origin. The sequence data place Lactucosonchus as sister group to the remainder of the alliance and also indicate that four related genera are in turn sister groups to subg. Dendrosonchus and Taeckholmia. This implies that the woody members of Sonchus were derived from an ancestor similar to allied genera now present on the Canary Islands. It is also evident that the alliance probably occurred in the Canary Islands during the late Miocene or early Pliocene. A rapid radiation of major lineages in the alliance is consistent with an unresolved polytomy near the base and low ITS sequence divergence. Increase of woodiness is concordant with other insular endemics and refutes the relictural nature of woody Sonchus in the Macaronesian islands.

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We describe a procedure for preferential isolation of DNA fragments with G+C-rich portions. Such fragments occur in known genes within or adjacent to CpG islands. Since about 56% of human genes are associated with CpG islands, isolation of these fragments permits detection and probing of many genes within much larger segments of DNA, such as cosmids or yeast artificial chromosomes, which have not been sequenced. Cloned DNA fragments digested with four restriction endonucleases were subjected to denaturing gradient gel electrophoresis. Long G+C-rich sections in fragments inhibit strand dissociation after the fragments reach retardation level in the gradient; such fragments are retained in the gel after most others disappear. Nucleotide sequences of the retained fragments show that about half of these fragments appear to be derived from CpG islands. Northern analysis indicated the presence of RNA complementary to most of the retained fragments. A heuristic approach to the relation between base sequence and the kinetics of strand dissociation of partly melted molecules appears to account for retention and nonretention. The expectation that CpG island fragments will be enriched among fragments retained in a denaturing gradient is supported by rate estimates based on melting theory applied to known sequences. This method, designated SPM for segregation of partly melted molecules, is expected to provide a means for convenient and efficient isolation of genes from unsequenced DNA.

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Some islands in the Gulf of California support very high densities of spiders. Spider density is negatively correlated with island size; many small islands support 50-200 spiders per m3 of cactus. Energy for these spiders comes primarily from the ocean and not from in situ productivity by land plants. We explicitly connect the marine and terrestrial systems to show that insular food webs represent one endpoint of the marine web. We describe two conduits for marine energy entering these islands: shore drift and seabird colonies. Both conduits are related to island area, having a much stronger effect on smaller islands. This asymmetric effect helps to explain the exceptionally high spider densities on small islands. Although productivity sets the maximal potential densities, predation (by scorpions) limits realized spider abundance. Thus, prey availability and predation act in concert to set insular spider abundance.

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The Marshall Islands, a small island developing nation, has a significant solid waste problem. The atoll environment of the Majuro, the capital of the Marshall Islands, is one of scarce land and overpopulation. Increasing Western influences has been a major factor in this solid waste problem. This problem has created health issues and is an impediment to the development of a tourism industry, which is essential to the development of economic opportunities. Responsibility for solid waste management in Majuro is divided between several governmental and non-governmental agencies. This system is dysfunctional as there is little or no cooperation between the agencies. Although many consultants have developed recommendations, no action has been taken. Developing an action plan to consolidate solid waste management under one authority is important to solving of this solid waste problem. This project proposes legislation creating a solid waste management authority that will have the power to regulate all aspects of solid waste and help implement education and awareness to the people of the Marshall Islands.

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Se presenta un bosquejo acerca de un documento de excepcional valor histórico para la ornitología balear: el manuscrito de Las Aves de las Islas Baleares (1943), redactado en inglés por el ornitólogo británico Philip Winchester Munn durante su exilio lisboeta.