Transcription factors involved in retinogenesis are co-opted by the circadian clock following photoreceptor differentiation

The circadian clock is known to regulate a wide range of physiological and cellular processes, yet remarkably little is known about its role during embryo development. Zebrafish offer a unique opportunity to explore this issue, not only because a great deal is known about key developmental events in this species, but also because the clock starts on the very first day of development. In this study, we identified numerous rhythmic genes in zebrafish larvae, including the key transcriptional regulators neurod and cdx1b, which are involved in neuronal and intestinal differentiation, respectively. Rhythmic expression of neurod and several additional transcription factors was only observed in the developing retina. Surprisingly, these rhythms in expression commenced at a stage of development after these transcription factors are known to have played their essential role in photoreceptor differentiation. Furthermore, this circadian regulation was maintained in adult retina. Thus, once mature photoreceptors are formed, multiple retinal transcription factors fall under circadian clock control, at which point they appear to play a new and important role in regulating rhythmic elements in the phototransduction pathway

Revistas e jornais de música

A Biblioteca Pública de Braga, para assinalar o dia 1 de Outubro, Dia Mundial da Música, organizou em 2003 uma exposição das revistas e jornais de música que integram as suas colecções. Pôde, assim, dar-se a conhecer aos curiosos e estudiosos da música o acervo que nessa área se encontra arquivado nesta biblioteca, constituído sobretudo graças à sua qualidade de beneficiária do Depósito Legal. Tal iniciativa pretendeu ainda sublinhar a reconhecida importância deste tipo de publicações para o conhecimento da vida musical, dos compositores aos intérpretes, da evolução dos géneros à variação dos gostos. Da pesquisa efectuada para o efeito nas colecções da BPB resultou uma selecção de mais de uma centena de títulos, reunidos no presente catálogo, e cujo ano de início de publicação se inscreve entre 1792 e 2001

Os periódicos e a emancipação feminina

M de Março. M de Mulher, expressão retirada das páginas da revista A Teia (1/1997), foi a designação escolhida para as comemorações do dia 8 de Março, Dia Internacional da Mulher, levadas a efeito, neste ano de 2002, pela Biblioteca Pública de Braga, com a adesão da Escola de Direito e do Departamento de Estudos Ingleses e Norte-Americanos.Para assinalar esse dia, a Biblioteca Pública preparou a exposição bibliográfica .. Os periódicos e a emancipação feminina», que poderá dar uma perspectiva do processo de afirmação da mulher, no qual aquele tipo de publicações desempenhou papel relevante

Circadian Clock Synchronization of the Cell Cycle in Zebrafish Occurs through a Gating Mechanism Rather Than a Period-phase Locking Process

Studies from a number of model systems have shown that the circadian clock controls expression of key cell cycle checkpoints, thus providing permissive or inhibitory windows in which specific cell cycle events can occur. However, a major question remains: Is the clock actually regulating the cell cycle through such a gating mechanism or, alternatively, is there a coupling process that controls the speed of cell cycle progression? Using our light-responsive zebrafish cell lines, we address this issue directly by synchronizing the cell cycle in culture simply by changing the entraining light-dark (LD) cycle in the incubator without the need for pharmacological intervention. Our results show that the cell cycle rapidly reentrains to a shifted LD cycle within 36 h, with changes in p21 expression and subsequent S phase timing occurring within the first few hours of resetting. Reentrainment of mitosis appears to lag S phase resetting by 1 circadian cycle. The range of entrainment of the zebrafish clock to differing LD cycles is large, from 16 to 32 hour periods. We exploited this feature to explore cell cycle entrainment at both the population and single cell levels. At the population level, cell cycle length is shortened or lengthened under corresponding T-cycles, suggesting that a 1:1 coupling mechanism is capable of either speeding up or slowing down the cell cycle. However, analysis at the single cell level reveals that this, in fact, is not true and that a gating mechanism is the fundamental method of timed cell cycle regulation in zebrafish. Cell cycle length at the single cell level is virtually unaltered with varying T-cycles

Testing the robustness of controllers for self-adaptive systems

Self-Adaptive systems are software-intensive systems endowed with the ability to respond to a variety of changes that may occur in their environment, goals, or the system itself, by adapting their structure and behavior at run-time in an autonomous way. Controllers are complex components incorporated in self-adaptive systems, which are crucial to their function since they are in charge of adapting the target system by executing actions through effectors, based on information monitored by probes. However, although controllers are becoming critical in many application domains, so far very little has been done to assess their robustness. In this paper, we propose an approach for evaluating the robustness of controllers for self-adaptive software systems, aiming to identify faults in their design. Our proposal considers the stateful nature of the controller, and identifies a set of robustness tests, which includes the provision of mutated inputs to the interfaces between the controller and the target system (i.e., probes). The feasibility of the approach is evaluated on Rainbow, a framework for architecture-based self-adaptation, and in the context of the Znn.com case study

Malaria parasites regulate the duration of the intra-erythrocytic cycle via serpentine receptor 10 and coordinate development with host daily rhythms

Malaria parasites complete their intra-erythrocytic developmental cycle (IDC) in multiples of 24 h suggesting a circadian basis, but the mechanism controlling this periodicity is unknown. Combining in vivo and in vitro approaches utilizing rodent and human malaria parasites, we reveal that: (i) 57% of Plasmodium chabaudi genes exhibit daily rhythms in transcription; (ii) 58% of these genes lose transcriptional rhythmicity when the IDC is out-of-synchrony with host rhythms; (iii) 6% of Plasmodium falciparum genes show 24 h rhythms in expression under free-running conditions; (iv) Serpentine receptor 10 (SR10) has a 24 h transcriptional rhythm and disrupting it in rodent malaria parasites shortens the IDC by 2-3 h; (v) Multiple processes including DNA replication, and the ubiquitin and proteasome pathways, are affected by loss of coordination with host rhythms and by disruption of SR10. Our results reveal malaria parasites are at least partly responsible for scheduling the IDC and coordinating their development with host daily rhythms

Distribuição espacial de hymenoptera parasitoides em uma reserva florestal na amazônia central, manaus, am, Brasil

Parasitoids are of great importance to forest ecosystems due to their ecological role in the regulation of the population of other insects. The species richness and abundance of parasitoids in the forest canopy and understory, both on the borders and in the interior of a tropical forest reserve in Central Amazonia were investigated. For a12-month period, specimen collections were made every 15days from suspended traps placed in the forest canopy and in the understory strata, both on the border and in the interior of forest areas. A total of 12,835Hymenoptera parasitoids from 23families were acquired. Braconidae, Diapriidae, Mymaridae, Eulophidae, and Scelionidae were the most represented in the area and strata samples. The results indicate that there were no significant differences in the species richness or abundance of Hymenoptera between the forest borders and the inner forest. The data does show that the presence of Hymenoptera is significantly greater in the understory in both the border and interior areas than in the canopy (vertical stratification). Aphelinidae and Ceraphronidae were significantly associated with the inner forest, while the other seven families with the border of the reserve. The abundance of Hymenoptera parasitoids presented seasonal variations during the year related to the rainy and dry seasons