Background: African trypanosomes are capable of both pyrimidine biosynthesis and salvage of preformed pyrimidines from the host, but it is unknown whether either process is essential to the parasite. Methodology/Principal Findings: Pyrimidine requirements for growth were investigated using strictly pyrimidine-free media, with or without single added pyrimidine sources. Growth rates of wild-type bloodstream form Trypanosoma brucei brucei were unchanged in pyrimidine-free medium. The essentiality of the de novo pyrimidine biosynthesis pathway was studied by knocking out the PYR6-5 locus that produces a fusion product of orotate phosphoribosyltransferase (OPRT) and Orotidine Monophosphate Decarboxylase (OMPDCase). The pyrimidine auxotroph was dependent on a suitable extracellular pyrimidine source. Pyrimidine starvation was rapidly lethal and non-reversible, causing incomplete DNA content in new cells. The phenotype could be rescued by addition of uracil; supplementation with uridine, 29deoxyuridine, and cytidine allowed a diminished growth rate and density. PYR6-52/ 2 trypanosomes were more sensitive to pyrimidine antimetabolites and displayed increased uracil transport rates and uridine phosphorylase activity. Pyrimidine auxotrophs were able to infect mice although the infection developed much more slowly than infection with the parental, prototrophic trypanosome line. Conclusions/Significance: Pyrimidine salvage was not an essential function for bloodstream T. b. brucei. However, trypanosomes lacking de novo pyrimidine biosynthesis are completely dependent on an extracellular pyrimidine source, strongly preferring uracil, and display reduced infectivity. As T. brucei are able to salvage sufficient pyrimidines from the host environment, the py

African trypanosomes are capable of both pyrimidine biosynthesis and salvage of preformed pyrimidines from the host. However, uptake of pyrimidines in bloodstream form trypanosomes has not been investigated, making it difficult to judge the relative importance of salvage and synthesis or to design a pyrimidine-based chemotherapy. Detailed characterization of pyrimidine transport activities in bloodstream form Trypanosoma brucei brucei found that these cells express a high-affinity uracil transporter (designated TbU3) that is clearly distinct from the procyclic pyrimidine transporters. This transporter had low affinity for uridine and 2′deoxyuridine and was the sole pyrimidine transporter expressed in these cells. In addition, thymidine was taken up inefficiently through a P1-type nucleoside transporter. Of importance, the anticancer drug 5-fluorouracil was an excellent substrate for TbU3, and several 5-fluoropyrimidine analogs were investigated for uptake and trypanocidal activity; 5F-orotic acid, 5F-2′deoxyuridine displayed activity in the low micromolar range. The metabolism and mode of action of these analogs was determined using metabolomic assessments of T. brucei clonal lines adapted to high levels of these pyrimidine analogs, and of the sensitive parental strains. The analysis showed that 5-fluorouracil is incorporated into a large number of metabolites but likely exerts toxicity through incorporation into RNA. 5F-2′dUrd and 5F-2′dCtd are not incorporated into nucleic acids but act as prodrugs by inhibiting thymidylate synthase as 5F-dUMP. We present the most complete model of pyrimidine salvage in T. brucei to date, supported by genome-wide profiling of the predicted pyrimidine biosynthesis and conversion enzymes.

Given the pressing need for new antiprotozoal drugs without cross-resistance with current (failing) chemotherapy, we have explored 3-tridecylpyridinium alkaloids (3TPAs), derivatives of viscosamine, as antiparasitic agents. We have developed a simple synthetic route toward viscosamine and related cyclic and linear monomers and oligomers. Evaluation for cytotoxicity on the protozoan parasites Trypanosoma brucei, Leishmania spp., and Plasmodium falciparum revealed several 3TPAs with antiprotozoal activity in the nanomolar range. Their promising selectivity index in vitro prompted us to study the dynamics of cytotoxicity on trypanosomes in more detail. Parasites were killed relatively slowly at therapeutically safe concentrations, in a process that did not target the cell cycle. Clearance of T. brucei cultures was observed at drug concentrations of 1–10 μM.

Few studies have systematically addressed evolutionary changes in olfactory neuron assemblies, either by genetic drift or as an

adaptation to specific odor environments. We have studied the sense of olfaction in 2 congeneric scarab beetles, Pachnoda

interrupta Olivier and Pachnoda marginata Drury (Coleoptera: Scarabaeidae: Cetoniinae), which are both opportunistic

polyphages, feeding mainly on fruit and flowers. The 2 species occur in dissimilar habitats: P. interrupta is found in dry

savannah, and P. marginata in tropical parts of equatorial Africa. To study how these species may have adapted their sense of

olfaction to their odor environments, we utilized single-unit electrophysiology on olfactory sensilla with a wide selection of

food-related compounds. Despite the differences in habitat, we found that the species shared most of the physiological types

of olfactory receptor neurons (ORNs) encountered, although their proportions frequently varied between the species. The high

degree of conservation in olfaction between the species implies that a similar sensory strategy is efficient for food search in

both habitats. However, shifts in proportions of receptor neuron classes, and slight shifts in response profiles and/or presence

of some ORN classes unique to either species, may reflect adaptation to a different set of hosts.

Key words: comparative study, electrophysiology, olfaction, polyphagous herbivore, single sensillum recordings

Few studies have addressed how olfactory systems may be adapted to different odour environments. I have performed the largest study to date, comparing olfactory receptor neurons in the two congeneric species of scarab beetle, P. marginata and P. interrupta. Both species are fruit- and flower-eaters but geographically separated (equatorial versus sub-Saharan Africa, resp.). They have similar lamellate antennae covered mostly with numerous olfactory sensilla placodea (plate sensilla) and a lesser number of other types, mainly sensilla coeloconica (grooved peg), and smooth peg sensilla of unknown function. By means of single sensillum recordings with tungsten microelectrodes I screened a great number of olfactory sensilla with a large array of odorants. I compared 456 sensilla placodea, containing 212 responding cells, over the whole antennae in both species. The olfactory systems of these two species displayed an amazing degree of conservation, with 20 identified olfactory neuron classes, all except two of which were found in both species with no detectable difference in response profiles. The exceptions were two olfactory receptor neuron classes: methyl benzoate and gamma-nonalactone, which were only found in Pachnoda marginata. In general, the two species showed an almost total overlap in their receptor neuron assemblies. One aim of the study was also to test whether the arrangement of neurons within sensilla was conserved between the species, but this could not be tested as very few combinations of characterized neurons were encountered during the study.

Key words: olfaction, electrophysiology, scarab beetles, Pachnoda marginata, Pachnoda interrupta, single sensillum recording, olfactory receptor neurons

The sorghum chafer, Pachnoda interrupta Olivier

(Coleoptera: Scarabaeidae: Cetoniinae), is a key pest on

sorghum, Sorghum bicolor (L.) Moench (Poaceae), in

Ethiopia. At present there is a lack of efficient control

methods. Trapping shows promise for reduction of the pest

population, but would benefit from the development of

attractive lures. To find attractants that could be used for

control of P. interrupta, either by mass trapping or by

monitoring as part of integrated pest management, we

screened headspace collections of sorghum and the highly

attractive weed Abutilon figarianum Webb (Malvaceae) for

antennal activity using gas chromatograph-coupled electroantennographic

detection (GC-EAD). Compounds active in

GC-EAD were identified by combined gas chromatography

and mass spectrometry (GC-MS).

The present study was performed to evaluate the anti-schistosomal activity of the medicinal plant ginger Zingiber officinale. Mice were individually infected with 100 Schistosoma mansoni cercariae. Four weeks post-infection, mice were orally treated with 1200 mg/kg of ginger for ten consecutive days. After the last dose all animals were sacrificed to evaluate the efficacy of ginger in treatment of the infection. The results obtained showed moderate reduction of 16.5% in the worm burden compared with control infected animals. The liver egg count showed a marked reduction of 53.8%. Ginger treatment showed a significant reduction in the size of liver granuloma where a percentage reduction of 66.35 was observed. Ginger treatment was slightly reflected on the liver function at such rate of infection, where an improvement in serum arginase activity was recorded, while no appreciable improvement in hepatic ALT and AST activities, albumin and creatinine contents. In conclusion Z. officinale displayed some degree of anti-schistosomal activity through reducing of the S. mansoni eggs output and the liver granuloma size.