Driving forces of the diel distribution of phytoplankton functional groups in a shallow tropical lake (Lake Monte Alegre, Southeast Brazil) / Fatores direcionadores da distribuição nictemeral de grupos funcionais fitoplanctônicos de um lago brasileiro raso e tropical

Phytoplankton vertical and diel dynamics in a small shallow lake (Lake Monte Alegre, Ribeirão Preto, state of São Paulo) were investigated in two climatological periods: July 2001 (cool-dry season) and March 2002 (warm-rainy season). Monte Alegre is a eutrophic reservoir, with a warm polymictic discontinuous circulation pattern. The lake was thermally stratified in both periods, although dissolved oxygen varied less in the cool-dry period. Phytoplankton biomass was higher in the warm-rainy season and the vertical distribution was stratified in both seasons. Flagellate groups (Lm, Y, W1 and W2) and functional groups typical of shallow eutrophic environments (J, X1 and Sn) were important throughout the study period. The lake's thermal pattern strongly influenced the vertical distribution of the phytoplankton community in both periods. Biomass, functional groups and size classes of phytoplankton also were determined by the presence of more efficient herbivores in the lake, especially during the cool-dry period when phytoplankton biomass decreased.

As dinâmicas vertical e nictemeral do fitoplâncton de um lago pequeno e raso (Lago Monte Alegre, Ribeirão Preto, SP) foram investigadas em dois períodos climatológicos: julho/2001 (estação fria-seca) e março/2002 (estação quente-chuvosa). O lago esteve estratificado termicamente nos dois períodos de estudo, porém menores variações do oxigênio dissolvido foram observadas no período frio-seco. Maiores biomassas fitoplanctônicas foram registradas na estação quente-chuvosa e a distribuição vertical esteve estratificada nos dois períodos climatológicos. Grupos de flagelados (Lm, Y, W1 e W2), juntamente com grupos funcionais típicos de ambientes rasos e eutróficos (J, X1 e Sn), foram importantes em todo o estudo. O padrão térmico do lago teve influência na distribuição vertical da comunidade fitoplanctônica nos períodos estudados. Biomassa, grupos funcionais e classes de tamanho do fitoplâncton também foram influenciados pela presença de herbívoros mais eficientes, principalmente durante o período frio-seco, quando ocorreram menores biomassas do fitoplâncton.

Multistep carcinogenesis and genital papillomavirus infection: implications for diagnosis and vaccines

Activated cellular oncogenes (myc and ras, for example) and inactivated anti-oncogenes (p53 or Rb) participate in multistep carcinogenesis. In addition, some high risk human papillomaviruses (HPV) are also involved in uterine cervix carcinomas. Typification of HPV is important for clinical diagnosis. Unravelling the complexities of the immune system and understanding the biochemistry and molecular genetics of cellular oncogenes and tumor viruses have opened up new possibilities for vaccination