We found that the sex-ratio of an amphigenic strain of Sciara ocellaris varied widely from progenies with few males to progenies containing a larger proportion of males, with single-sex progenies being rare. The sex-ratio distributions were dependent on the temperature at which the stocks of flies were raised, with the sex-ratio distributions being symmetrical (i.e. about 50% males) at 18°C and 20°C while at the higher temperatures of 24°C and 28°C the distributions were skewed toward a high proportion of females with the mean proportion of males decreasing to about 30-37% per progeny. Temperature-shift experiments showed that high temperatures were effective only during the last stages of female pupal development plus a period after adult emergence, stages corresponding to oocyte maturation. When imagine females were exposed to temperatures as low as 12°C the sex-ratio distributions of their progeny were skewed toward a high proportion of males per progeny. No differential fecundity was involved in these progeny sex-ratio modifications. Egg-to-adult survival was lower at 18°C and 28°C but no correlations with skewing in the sex ratio distributions were observed, indicating that modifications in progeny sex-ratio did not involve the differential survival of a particular sex.

We have determined the deleterious effects of singlet oxygen (1O2), generated by thermal decomposition of the water-soluble endoperoxide 3,3'-(1,4-naphthylidene)dipropionate (NDPO2), on plasmid DNA. By following the electrophoretic mobility of DNA on agarose gels, we detected single and double strand breaks induced by treatment with NDPO2. The vector employed was a mammalian shuttle vector and the mutagenic consequences of these damages were investigated, using as mutation target the supF suppressor tRNA gene. A high increase of the mutation frequency, over the background, was observed in plasmids transfected in bacteria or after passage through mammalian cells. Trapping agents and quencher effects and other controls confirm the involvement of 1O2 in DNA damage and mutagenicity. These findings indicate that 1O2 can induce DNA lesions which are repaired by an error-prone process in prokaryotic and eukaryotic cells.

In order to characterize the molecular nature of singlet oxygen (1O2) induced mutations in mammalian cells, a SV40-based shuttle vector (pi SVPC13) was treated with singlet oxygen arising from the thermal decomposition of the water-soluble endoperoxide of 3,3'-(1,4-naphthylidene) dipropionate (NDPO2). After the passage of damaged plasmid through monkey COS7 cells, the vector was shuffled into E. coli cells, allowing the screening of supF mutants. The mutation spectrum analysis shows that single and multiple base substitutions arose in 82.5% of the mutants, the others being rearrangements. The distribution of mutations within the supF gene is not random and some hotspots are evident. Most of the point mutations (98.4%) involve G:C base pairs and G:C to T:A transversion was the most frequent mutation (50.8%), followed by G:C to C:G transversion (32.8%). These results indicate that mutagenesis in mammalian cells, mediated by 1O2-induced DNA damage, is targeted selectively at guanine residues.

Language is one field of science education research that has received a lot of attention lately. This is revealed by an increase in the number of papers that deal with this subject (Carlsen, 2007). One of the topics related to language in science education that still need to be further explored is reading and writing in science. Here, some questions that can represent border knowledge are: How school science texts can be characterized? Is there any relation between these texts and their reading comprehension? Possible answers to these questions have dealt with the linguistic features of science texts (

The purpose of this article is to assess the knowledge, application of knowledge, and attitudes associated with the reading of different genres of expository science texts. We assigned approximately half of a sample consisting of 220 students 14-15 years of age, chosen at random, to read an excerpt from a popular scientific text, and the other half to read an excerpt from a textbook addressing the same topic. Readers took knowledge and application tests immediately after the reading and again 15 days later. Students also took knowledge and reading proficiency pre-tests, and attitude tests related to the selected texts. Overall, girls scored higher than boys and readers of the popular scientific text scored higher than their colleagues who read the textbook excerpt. We noted interaction between 'reader gender' and 'genre of the text read' in terms of longterm learning based on the reading. Attitude regarding the text read appears as an important factor in explaining behavior of boys who read the popular scientific text. Surprisingly, knowledge and application test scores were not statistically different among girls with different degrees of reading proficiency who read the textbook excerpt. In addition, on the application tests, among the boys who read the popular scientific text, good readers scored lower than their colleagues who read the textbook excerpt. In our opinion, this study can serve to show that 'reading in science education' is not a trivial matter and we feel that the subject merits more in-depth investigation.

Resumo: Neste trabalho, apresentamos parte do perfil de 24 professores de 1º ao 5º ano envolvidos num projeto de formação continuada, que tinha o objetivo de promover a alfabetização científica. Por meio da análise de respostas a um questionário e de entrevistas, verificamos objetivos conferidos à Ciência escolar, além de atribuição de importância e grau de confiança para ensinar esta em relação a outras disciplinas escolares. Constatamos que esses docentes conferem grande destaque à disciplina de Língua Portuguesa, indicam predominantemente que o ensino de Ciências deve objetivar a educação ambiental e o ensino-aprendizagem de conceitos, bem como parecem estar relativamente seguros quanto às suas práticas. Nossa conclusão é que, em seu atual estágio de desenvolvimento profissional, esses docentes não explicitam o que a ideia de alfabetização científica possa implicar para os seus objetivos na educação em ciências, nem como conciliar essa ideia com o alto peso que é dado ao ensino de Língua Portuguesa.Palavras-chave: Formação de professores. Ensino Fundamental. Alfabetização científica. Ensino de Ciências. Abstract:Here we present a partial profile of 24 science teachers enrolled in a project that explicit aimed at promoting science literacy. The teachers' answers to a questionnaire, complemented with interviews, enabled us to verify some elements related to teachers' objectives and importance attributed to school science and also the level of confidence these teachers declare to have to teach science in relation to other school topics. We verified that teachers rank the teaching of the mother language as more important than the teaching of science and indicate, as objectives for school science, the environmental education and the learning of concepts. Our most important remark is that, in their stage of professional development, these teachers can neither clearly explicit the implications the idea of science literacy can have to their school science objectives, nor conciliate this with the high value that it is attributed to the teaching of the mother language.

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O ensino-aprendizagem do conceito Célula é um desafio para professores e pesquisadores que ensinam ciências. [...]