Browsing by Author "Torrealba, C"

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    Incidence of BRCA1 and BRCA2 mutations in 54 Chilean families with breast/ovarian cancer, genotype-phenotype correlations
    (2006) Gallardo, M; Silva, A; Rubio, L; Alvarez, C; Torrealba, C; Salinas, M; Tapia, T; Faundez, P; Palma, L; Riccio, M; Paredes, H; Rodriguez, M; Cruz, A; Rousseau, C; King, M; Camus, M; Alvarez, M; Carvallo, P
    Our aim was to analyze the incidence of mutations in BRCA1 and BRCA2 genes in 54 families with breast/ovarian cancer. Families were selected from three Institutions following the standard criteria for hereditary breast/ovarian cancer. PCR amplification of all exons was performed, followed by SSCP, heteroduplex, PTT and sequencing analysis. We identified eight truncation mutations, three in the BRCA1 gene and five in the BRCA2 gene. Three of these mutations have not been reported previously by other groups: 308insA in one family, 3936 C > T in two families, for BRCA1, and 4970insTG in one family for BRCA2. In addition two families having Ashkenazi Jewish ancestors present the well known mutations 185delAG and 6174delT. Interestingly, 5 out of 11 families have mutations recurrent in Spanish families. Among the 54 families selected, seven have breast and ovary cancer cases, and only two presented a mutation in BRCA1 or BRCA2 genes. Other cancers as prostate and stomach are frequent among relatives carrying the mutation. Five cases of very early onset (< 31 years old) breast cancer were detected. The frequencies of BRCA1 (0.074) and BRCA2 (0.13) mutations in our families is low but similar to the incidence found in other populations, like in Spain. Since is widely known that risk factors that modulate the development of breast cancer such as lifestyle risk factors, geographic location, country of origin and socioeconomic status, besides a familial history of breast cancer our findings suggest that the history of colonization and immigrations is very relevant when studying hereditary factors associated to breast cancer.
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    Litterfall dynamics and nitrogen use efficiency in two evergreen temperate rainforests of southern Chile
    (2003) Pérez, CA; Armesto, JJ; Torrealba, C; Carmona, MR
    In unpolluted regions, where inorganic nitrogen (N) inputs from the atmosphere are minimal, such as remote locations in southern South America, litterfall dynamics and N use efficiency of tree species should be coupled to the internal N cycle of forest ecosystems. This hypothesis was examined in two evergreen temperate forests in southern Chile (42degrees30'S), a mixed broad-leaved forest (MBF) and a conifer forest (CF). Although these forests grow under the same climate and on the same parental material, they differ greatly in floristic structure and canopy dynamics (slower in the CF). In both forests, biomass, N flux, and C/N ratios of fine litterfall were measured monthly from May 1995 to March 1999. There was a continuous litter flux over the annual cycle in both forests, with a peak during autumn in the CF. In the MBF, litterfall decreased during spring. In both forests, the C/N ratios of litterfall varied over the annual cycle with a maximum in autumn. Annual litterfall biomass flux (Mean +/- SD = 3.3 +/- 0.5 vs 2.0 +/- 0.5 Mg ha(-1)) and N return (34.8 +/- 16 vs 9.1 +/- 2.8 kg N ha(-1)) were higher in the MBF than in the CF. At the ecosystem level, litterfall C/N was lower in the MBF (mean C/N ratio = 60.1 +/- 15, n = 3 years) suggesting decreased N use efficiency compared with CF (mean C/N ratio = 103 +/- 19.6, n = 3 years). At the species level, subordinated (subcanopy) tree species in the MBF had significantly lower C/N ratios (<50) of litterfall than the dominant trees in the CF and MBF (>85). The litterfall C/N ratio and percentage N retranslocated were significantly correlated and were lower in the MBF. The higher net N mineralization in soils of the MBF is related to a lower N use efficiency at the ecosystem and species level.