Cytological and genome size data analyzed in a phylogenetic frame: Evolutionary implications concerning Sisyrinchium taxa (Iridaceae: Iridoideae)

Abstract Sisyrinchium is the largest genus of Iridaceae in the Americas and has the greatest amount of cytological data available. This study aimed at investigating how genomes evolved in this genus. Chromosome number, genome size and altitude from species of sect. Viperella were analyzed in a phylogenetic context. Meiotic and pollen analyses were performed to assess reproductive success of natural populations, especially from those polyploid taxa. Character optimizations revealed that the common ancestor of sect. Viperella was probably diploid (2n = 2x =18) with two subsequent polyplodization events. Total DNA content (2C) varied considerably across the phylogeny with larger genomes detected mainly in polyploid species. Altitude also varied across the phylogeny, however no significant relationship was found between DNA content changes and altitude in our data set. All taxa presented regular meiosis and pollen viability (> 87%), except for S. sp. nov. aff. alatum (22.70%), suggesting a recent hybrid origin. Chromosome number is mostly constant within this section and polyploidy is the only source of modification. Although 2C varied considerably among the 20 taxa investigated, the diversity observed cannot be attributed only to polyploidy events because large variations of DNA content were also observed among diploids.

Prevalence of common α -thalassemia determinants in south Brazil: importance for the diagnosis of microcytic anemia

Alpha thalassemia has not been systematically investigated in Brazil. In this study, 493 unrelated individuals from the southernmost Brazilian state of Rio Grande do Sul were screened for deletional forms of α-thalassemia. One hundred and one individuals had microcytic anemia (MCV < 80 fL) and a normal hemoglobin pattern (Hb A2 < 3.5 percent and Hb F < 1 percent). The subjects were screened for -α3.7,-α4.2,-α20.5, -SEA and -MED deletions but only the -α3.7 allele was detected. The -α3.7 allele frequency in Brazilians of European and African ancestry was 0.02 and 0.12, respectively, whereas in individuals with microcytosis the frequency was 0.20. The prevalence of α-thalassemia was significantly higher in individuals with microcytosis than in healthy individuals (p = 0.001), regardless of their ethnic origin. There were also significant differences in the hematological parameters of individuals with -α3.7/αα, -α3.7/α3.7 and β-thalassemia trait compared to healthy subjects. These data suggest that α-thalassemia is an important cause of microcytosis and mild anemia in Brazilians.

Brazilian indian/non indian interactions and their effects

A short review was made of the history of the Brazilian population, starting with the Asians who colonized the region 30,000-40,000 years ago, and continuing with evaluations of the European, African, and neo-Asiatic immigration. Social aspects of the contact situation between Brazilian Indians and the surrounding society were briefly considered, as well as quantitative estimates of the amount of Amerindian genes present in neo-Brazilians. Special emphasis, however, was placed in the inverse gene flow (neo-Brazilian genes into Amerindians). In this case, two methods which quantify the degree of such admixture were employed, and the one considered to give better estimates was chosen. Although the correlation obtained between these admixture values and the number of years of more permanent contact with non-Indians yielded a low number (perhaps due to deficiencies in obtaining precise figures concerning years of contact), a clear correlation was found between the admixture estimates obtained in 39 Brazilian Indian tribes or populations and their location in degrees of longitude west. This is probably a reflection of the general neo-Brazilian east-west colonization movement. At present it is difficult to ascertain the degree of biological and cultural homogeneity that will be reached by Brazilian populations in the future. It is hoped, however, that a certain amount of diversity will be maintained, in a climate of mutual respect.

Medidas de associaçäo em estudos epidemiologicos: risco relativo e odds ratio / Measures of association in epidemiological studies: relative risk and odds ratio

Objetivos: Descrever os aspectos essenciais do risco relativo e do odds ratio, incluindo fórmulas para o cálculo de intervalos de confiança. Métodos: Revisäo de diversos livros de epidemiologia, bioestatística e artigos selecionados. Resultados: O risco relativo (RR) é uma medida da força da associaçäo entre um fator de risco e o desfecho em um estudo epidemiológico. E definido como sendo a razäo entre a incidência entre indivíduos expostos e a incidência entre os näo-expostos. E usualmente utilizado em estudos de coorte. O odds ratio é uma estimativa do risco relativo. Possui a mesma interpretaçäo, apesar de ser baseado em uma fórmula diferente. Esta medida é particularmente indicada para estudos de caso-controle. Outras medidas de associaçäo encontradas na literatura epidemiológica e rapidamente definidas neste artigo incluem a razäo de prevalências, o risco atribuível na populaçäo, a reduçäo do risco relativo e o número necessário a tratar. Conclusäo: As medidas de associaçäo baseadas em razöes, como risco relativo e o odds ratio, fornecem dados sobre a força da associaçäo entre o fator em estudo e o desfecho, permitindo que se faça um julgamento sobre uma relaçäo de causalidade. Assim, o risco ralativo e o odds ratio säo medidas de escolha para estudarmos os possíveis determinantes das doenças, sendo freqüentemente utilizadas em estudos de coorte e de caso-controle, respectivamente...