Fish are often used for screening genotoxicity of water. For such programs, a knowledge of the sensitivity to clastogens, spontaneous micronucleus frequency and cell cycle kinetics of the target tissue is necessary. To investigate the pattern of inter-specific sensitivity to micronucleus induction three species of fish, Tilapia rendalli, Oreochromis niloticus and Cyprinus carpio, were exposed to the clastogens bleomycin (BLM), cyclophosphamide (CP), 5-fluorouracil (5-FU), and mitomycin C (MMC). The binucleate/mononucleate ratio in peripheral erythrocytes exposed to cytochalasin B was also used to evaluate the time-dependent response of micronucleus formation during hematopoesis in the kidney and the micronucleus peak in peripheral erythrocytes. Micronucleus frequencies induced by CP were significantly greater than their respective controls for the three fish species throughout all treatment periods. During the whole evaluation period (30 days) CP was also the most effective clastogen. In general, until the 14th day of evaluation period T. rendalii was the most sensitive species to clastogens. No difference in micronucleus frequencies among species was observed in the 4th evaluation (at the 30th day). A micronucleus peak was observed at the 7th day after treatment. After the 14th day the frequencies were stabilized. The cytochalasin B experiment was carried out to demonstrate that micronuclei induced in the young kidney erythrocyte cells were detected in the circulating blood 2-4 days later.
Este estudo fez uma avaliação da indução de micronúcleos em eritrócitos de sangue periférico de peixes Tilapia rendalli, Oreochromis niloticus e Cyprinus carpio após o tratamento com mitomicina C, ciclofosfamida, 5-fluorouracil e bleomicina. Foram colhidas amostras periódicas de sangue com 2, 7, 14 e 30 dias após o tratamento único. Os tratamentos com citocalasina B tiveram como objetivo analisar as proporções entre células binucleadas/mononucleadas nos diferentes períodos de tratamento, para a comparação com os picos de micronúcleos entre as diferentes espécies, uma vez que o orgão hematopoiético nos peixes é o rim cefálico e o sangue analisado é de origem periférica, o que nos dá uma noção do tempo do ciclo celular dos eritrócitos. A análise das taxas de aumento das freqüências de micronúcleos ao longo do tempo demonstrou que do 2° ao 7°dias elas foram crescentes, decresceram ao 14° dia e mantiveram-se estáveis até ao 30°. Os 4 compostos químicos aumentaram significativamente as freqüências de micronúcleos ao longo de todo o período de tratamento, sendo que a ciclofosfamida e a mitomicina C foram as mais efetivas. A T. rendalli foi a espécie mais sensível a todos os tratamentos, enquanto que C. carpio foi a mais resistente. Entre 2 e 7 dias pós-tratamento observaram-se as maiores induções de micronúcleos. A partir do 14° dia de tratamento as freqüências de micronúcleos tenderam a diminuir e as diferenças entre as espécies não foram significativas
We report the genetic analysis of 192 unrelated individuals of an elite breeding population of Eucalyptus grandis (Hill ex Maiden) with a selected set of six highly polymorphic microsatellite markers developed for species of the genus Eucalyptus. A full characterization of this set of six loci was carried out generating allele frequency distributions that were used to estimate parameters of genetic information content of these loci, including expected heterozygosity, polymorphism information content (PIC), power of exclusion, and probability of identity. The number of detected alleles per locus ranged from 6 to 33, with an average of 19.8 +/- 9.2. The average expected heterozygosity was 0.86 +/- 0.11 and the average PIC was 0.83 +/- 0.16. Using only three loci, it was possible to discriminate all 192 individuals. The overall probability of identity considering all six EMBRA microsatellite markers combined was lower than 1 in 2 billion. An analysis of the sample size necessary to estimate expected heterozygosity with minimum variance indicated that at least 64 individuals have to be genotyped to characterize this parameter with adequate accuracy for most microsatellites in Eucalyptus. The high degree of multiallelism and the clear and simple codominant Mendelian inheritance of the set of microsatellites used provide an extremely powerful system for the unique identification of Eucalyptus individuals for fingerprinting purposes and parentage testing.
Resumo -A coleção de germoplasma de arroz da Embrapa consiste aproximadamente de 10.000 acessos. O objetivo desse trabalho foi estabelecer a Coleção Nuclear (CN) dessa coleção utilizando as informações e dados disponí-veis sobre seus acessos. A estratégia CN foi introduzida no manejo de recursos genéticos vegetais com o principal objetivo de ampliar e sistematizar o uso desses recursos. Uma CN deve ser selecionada procurando reter a variabilidade genética existente na coleção inteira (CI) com um mínimo de redundância. Os acessos da coleção de arroz foram classificados em três estratos: a) variedades tradicionais do Brasil (VT); b) linhagens/ cultivares melhoradas do Brasil (LCM); e c) linhagens/cultivares introduzidas (LCI). As variedades tradicionais foram ainda classificadas segundo o sistema de cultivo (terras altas, várzeas e facultativo). Os três estratos foram representados na Coleção Nuclear, mas ênfase maior foi dada às variedades tradicionais, que constituíram 308 acessos. Os acessos foram alocados para cada sistema de cultivo, proporcionalmente ao produto do logarítmo do número de variedades tradicionais pelo índice de Shannon (medida de diversidade) de cada um deles. A seleção dos acessos foi feita com o auxilio do Sistema de Informação Geográfica (SIG). A CN brasileira de arroz está formada por 550 acessos Termos para indexação: Oryza sativa, SIG, diversidade genética, recursos genéticos, terras altas, várzeas. Constructing a rice core collection for BrazilAbstract -The Rice Germplasm Collection of Embrapa consists of approximately 10,000 accessions. This study aimed to establish a core collection using the currently available information data for those accessions. The strategy Core Collection (CN) was introduced in the management of plant genetic resources with the main purpose of improving the use of these resources. CN should be selected in order to preserve the genetic variability of the whole collection (CI), with minimum redundancy. The accessions within the rice collection were classified into three strata: a) landraces from Brazil (VT); b) breeding materials from Brazil (LCM); and c) introductions (LCI). The landraces were further classified according to crop system (uplands, lowlands and facultative). These three strata were represented in the Core Collection, but more emphasis was considered in representing the landraces, which are represented by 308 accessions. The accessions were allocated, for each crop system, proportionally to the product of the logarithm of the number of landraces by the Shannon Diversity Index (a measure of genetic diversity) within each crop system. Curators and breeders, supported by a Geographical Information System (GIS) made the selection of the accessions. The final Brazilian rice Core Collection consists of 550 accesses.Index terms: Oryza sativa, GIS, genetic diversity, genetic resources, uplands, lowlands. IntroduçãoO arroz (Oryza sativa L.) é cultivado em todos os continentes, sendo um alimento nutritivo na dieta de mais da metade da população mundial. Foi d...
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