Genetic diversity and relatedness within and between species of the genus Oligoryzomys (Rodentia; Sigmodontinae)

A RAPD analysis on six species of the rodent genus Oligoryzomys trapped in a wide area (ranging from 01° N to 32° S) of Brazilian territory was performed in order to determine the levels of genetic variability within and between its populations and species. One-hundred and ninety-three animals were collected in 13 different sites (corresponding to 17 samples) located at Pampas, Atlantic Rain Forest, Cerrado, and Amazon domains. Oligoryzomys sp., O. nigripes (8 populations), O. flavescens (4 populations), O. moojeni, O. stramineus, and O. fornesi were the taxa analyzed. Of the 20 primers tested, 4 generated a total of 75 polymorphic products simultaneously amplified in 151 specimens. Various diversity estimators analyzed showed considerable differences between species and populations, indicating a great genetic variation occurring in the Oligoryzomys taxa investigated. A cluster analysis was made using Nei's standard genetic distances, however, it did not correlate the genetic heterogeneity of the species and populations with the geographical areas.

Foram realizadas análises com RAPD em seis espécies de roedores do gênero Oligoryzomys capturados em uma ampla área (estendendo-se de 01° N a 32° S) do território brasileiro com o objetivo de determinar os níveis de variabilidade genética dentro e entre as populações e espécies. Cento e noventa e três animais foram coletados em 13 locais diferentes (correspondendo a 17 amostras) localizados nos Pampas, Floresta Atlântica, Cerrado e Amazônia. Oligoryzomys sp., O. nigripes (8 populações), O. flavescens (4 populações), O. moojeni, O. stramineus e O. fornesi foram as espécies analisadas. Vinte primers foram testados, sendo que quatro deles geraram um total de 75 produtos polimórficos amplificados simultaneamente em 151 exemplares. Várias estimativas de diversidade apresentaram diferenças consideráveis entre as espécies e as populações, indicando uma grande variação genética entre os taxa de Oligoryzomys investigados. As análises de agrupamento utilizando a distância genética de Nei, entretanto, não correlacionaram a heterogeneidade genética das espécies e populações com as áreas geográficas.

Association of apolipoprotein E polymorphism with plasma lipids and Alzheimer's disease in a Southern Brazilian population

Apolipoprotein E (protein: apo E; gene: APOE) plays an important role in the multifactorial etiology of both Alzheimer's disease (AD) and lipid level concentrations. The polymerase chain reaction (PCR) was used to investigate the APOE gene polymorphism in 446 unrelated Caucasians, among them 23 AD patients, and 100 Afro-Brazilians living in Porto Alegre, Brazil. The frequencies of the APOE*2, APOE*3 and APOE*4 alleles were 0.075, 0.810 and 0.115 in Caucasians and 0.075, 0.700 and 0.225 in Afro-Brazilians, respectively (c2 = 8.72, P = 0.013). A highly significant association was observed between the APOE*4 allele and AD in this population-based sample. The APOE*4 frequency in AD patients (39 percent) was about four times higher than in the general Caucasian population (11.5 percent). The influence of each of the three common APOE alleles on lipid traits was evaluated by the use of the average excess statistic. The E*2 allele is associated with lower levels of triglycerides and of total and non-HDL cholesterol in both men and women. Conversely, the E*4 allele is associated with higher levels of these traits in women only. The effect of APOE alleles was of greater magnitude in women.

Genetics, surnames, grandparents' nationalities, and ethnic admixture in Southern Brazil: do the patterns of variation coincide?

A total of 2,708 individuals from the European-derived population of Rio Grande do Sul, divided into seven mesoregions, and of 226 individuals of similar origin from Santa Catarina were studied. Seventeen protein genetic systems, as well as grandparents' nationalities, individuals' surnames, and interethnic admixture were investigated. The alleles which presented the highest and lowest differences were GLO1*2 (16 per cent) and PGD*A (2 per cent), respectively, but in general no significant genetic differences were found among mesoregions. The values observed were generally those expected for individuals of European descent, with the largest difference being a lower prevalence (34-39per cent) of P*1. Significant heterogeneity among mesoregions was observed for the other variables considered, and was consistent with historical records. The Amerindian contribution to the gene pool of European-derived subjects in Rio Grande do Sul was estimated to be as high as 11 per cent. Based on the four data sets, the most general finding was a tendency for a northeast-southwest separation of the populations studied. Seven significant phenotype associations between systems were observed at the 5 per cent level (three at the 0.1 per cent level). Of the latter, the two most interesting (since they were also observed in other studies) were MNSs/Duffy and Rh/ACP.