Identification of a major rif transcript common to gametocytes and sporozoites of Plasmodium falciparum

Background: The Plasmodium falciparum parasite is transmitted in its sexual gametocyte stage from man to mosquito and as asexual sporozoites from mosquito to man. Developing gametocytes sequester preferentially in the bone marrow, but mature stage gametocytes are released to the bloodstream. Sexual stage parasite surface proteins are of interest as candidate target antigens for transmission blocking vaccines.Methods: In this study, the transcript profiles of rif and var genes, known to encode surface antigens in asexual blood stage parasites, were investigated at different stages of 3D7/NF54 gametocytogenesis and in sporozoites.Results: Gametocytes exhibited a rif transcript profile unlinked to the rif and var transcript profile of the asexual progenitors. At stage V, mature gametocytes produced high levels of a single rif gene, PF13_0006, which also dominated the rif transcript profile of sporozoites. All var genes appeared to be silenced in sporozoites.Conclusions: The most prominent variant surface antigen transcribed in both gametocytes and sporozoites of 3D7/NF54 is a single variant of the RIFIN protein family. This discovery may lead to the identification of the parasites binding ligands responsible for the adhesion during sexual stages and potentially to novel vaccine candidates

Ecological influences on the behaviour and fertility of malaria parasites

BACKGROUND: Sexual reproduction in the mosquito is essential for the transmission of malaria parasites and a major target for transmission-blocking interventions. Male gametes need to locate and fertilize females in the challenging environment of the mosquito blood meal, but remarkably little is known about the ecology and behaviour of male gametes. METHODS: Here, a series of experiments explores how some aspects of the chemical and physical environment experienced during mating impacts upon the production, motility, and fertility of male gametes. RESULTS AND CONCLUSIONS: Specifically, the data confirm that: (a) rates of male gametogenesis vary when induced by the family of compounds (tryptophan metabolites) thought to trigger gamete differentiation in nature; and (b) complex relationships between gametogenesis and mating success exist across parasite species. In addition, the data reveal that (c) microparticles of the same size as red blood cells negatively affect mating success; and (d) instead of swimming in random directions, male gametes may be attracted by female gametes. Understanding the mating ecology of malaria parasites, may offer novel approaches for blocking transmission and explain adaptation to different species of mosquito vectors

FoxO and Stress Responses in the Cnidarian Hydra vulgaris

Background: In the face of changing environmental conditions, the mechanisms underlying stress responses in diverse organisms are of increasing interest. In vertebrates, Drosophila, and Caenorhabditis elegans, FoxO transcription factors mediate cellular responses to stress, including oxidative stress and dietary restriction. Although FoxO genes have been identified in early-arising animal lineages including sponges and cnidarians, little is known about their roles in these organisms. Methods/Principal Findings: We have examined the regulation of FoxO activity in members of the well-studied cnidarian genus Hydra. We find that Hydra FoxO is expressed at high levels in cells of the interstitial lineage, a cell lineage that includes multipotent stem cells that give rise to neurons, stinging cells, secretory cells and gametes. Using transgenic Hydra that express a FoxO-GFP fusion protein in cells of the interstitial lineage, we have determined that heat shock causes localization of the fusion protein to the nucleus. Our results also provide evidence that, as in bilaterian animals, Hydra FoxO activity is regulated by both Akt and JNK kinases. Conclusions: These findings imply that basic mechanisms of FoxO regulation arose before the evolution of bilaterians an

Human Aspects of Information Ergonomics

The need for information within a real-time operational environment, e.g. a trans-portation system, is related to predefined tasks and emerging events as well as the resulting activities and communication processes. Human operators have to per-form such tasks and react to such events taking place in their environment. The