Polymorphism at the Apical Membrane Antigen 1 Gene (AMA1) of the Malaria Parasite Plasmodium falciparum in a Vietnamese Population

The patterns of molecular evolution of the most diverse region of the apical membrane antigen 1 (AMA1) gene in Plasmodium falciparum from a Vietnamese subpopulation (Bao Loc) were investigated. Within the Bao Loc population, the sequenced gene region showed relatively high allelic and nucleotide diversity (0.985 and 0.02694, respectively). Further, the level of population recombination was substantial, resulting in a significant decay of linkage disequilibrium along the gene region. The results suggest that AMA1 is a useful genetic marker for studying the relationships between adaptation of parasite populations (to the human host immune system) and malaria epidemiology.     

Septin 11 Restricts InlB-mediated Invasion by Listeria

Septins are filament-forming GTPases implicated in several cellular functions, including cytokinesis. We previously showed that SEPT2, SEPT9, and SEPT11 colocalize with several bacteria entering into mammalian non-phagocytic cells, and SEPT2 was identified as essential for this process. Here, we investigated the function of SEPT11, an interacting partner of SEPT9 whose function is still poorly understood. In uninfected HeLa cells, SEPT11 depletion by siRNA increased cell size but surprisingly did not affect actin filament formation or the colocalization of SEPT9 with actin filaments. SEPT11 depletion increased Listeria invasion, and incubating SEPT11-depleted cells with beads coated with the Listeria surface protein InlB also led to increased entry as compared with control cells. Strikingly, as shown by fluorescence resonance energy transfer, the InlB-mediated stimulation of Met signaling remained intact in SEPT11-depleted cells. Taken together, our results show that SEPT11 is not required for the bacterial entry process and rather restricts its efficacy. Because SEPT2 is essential for the InlB-mediated entry of Listeria, but SEPT11 is not, our findings distinguish the roles of different mammalian septins.Septins were discovered in the budding yeast Saccharomyces cerevisiae (1) where they organize into a ring at the mother-bud neck during cell division (2). Septins are GTPases of 30-65 kDa found in most eukaryotes, except plants, sharing an essential role in cytokinesis (3, 4). Fourteen septins have been identified in humans and classified on the basis of sequence identity into four distinct groups (3, 5). Septins from different groups polymerize into hetero-oligomeric protein complexes and filaments and may associate with cellular membranes, actin filaments, and microtubules (6, 7). Septins are increasingly regarded as novel cytoskeletal elements (8), but their role in post-mitotic events remains poorly understood.The crystal structure of the SEPT2-SEPT6-SEPT7 complex recently highlighted that septins, as opposed to actin and microtubules, form non-polar filaments (9). In the SEPT7-SEPT6-SEPT2-SEPT2-SEPT6-SEPT7 complex, SEPT2 has a central role in filament formation (9), whereas SEPT6 is thought to be replaceable with other SEPT6 group members, including SEPT11 (3). Widely expressed in mammalian tissues (10), SEPT11 may also be a substitute for SEPT6 in other mammalian septin complexes such as SEPT7-SEPT9-SEPT11 (10) or SEPT5-SEPT7-SEPT11 (11). Because other septins homologous to SEPT11 might compensate for its deficiency (12), the degree to which SEPT11 is required for septin filament structure and function is not yet known. Listeria monocytogenes is an invasive bacterium that enters into most mammalian cells in vitro through the interaction of the bacterial surface protein InlB with its host cellular receptor Met, the hepatocyte growth factor receptor (13). We originally identified SEPT9 associated with phagosomes containing latex beads coated with InlB (14). Given the association of septins with the cytoskeleton, and the importance of the cytoskeleton in bacterial invasion, we have started investigating septin function during infection of invasive bacteria in non-phagocytic cells. We have discovered that SEPT9, and its interacting partners SEPT2 and SEPT11, are recruited as 0.6-μm collars next to actin at the site of entry of invasive bacteria (15). Although functional studies using siRNA³ have revealed an essential role for SEPT2 in regulating bacterial entry, the role of SEPT11 has not yet been investigated. We thus addressed SEPT11 function in the context of Listeria infection.     

Microscopic Observation Drug Susceptibility Assay (MODS) for Early Diagnosis of Tuberculosis in Children

MODS is a novel liquid culture based technique that has been shown to be effective and rapid for early diagnosis of tuberculosis (TB). We evaluated the MODS assay for diagnosis of TB in children in Viet Nam. 217 consecutive samples including sputum (n = 132), gastric fluid (n = 50), CSF (n = 32) and pleural fluid (n = 3) collected from 96 children with suspected TB, were tested by smear, MODS and MGIT. When test results were aggregated by patient, the sensitivity and specificity of smear, MGIT and MODS against “clinical diagnosis” (confirmed and probable groups) as the gold standard were 28.2% and 100%, 42.3% and 100%, 39.7% and 94.4%, respectively. The sensitivity of MGIT and MODS was not significantly different in this analysis (P = 0.5), but MGIT was more sensitive than MODS when analysed on the sample level using a marginal model (P = 0.03). The median time to detection of MODS and MGIT were 8 days and 13 days, respectively, and the time to detection was significantly shorter for MODS in samples where both tests were positive (P<0.001). An analysis of time-dependent sensitivity showed that the detection rates were significantly higher for MODS than for MGIT by day 7 or day 14 (P<0.001 and P = 0.04), respectively. MODS is a rapid and sensitive alternative method for the isolation of M.tuberculosis from children.     

CSPG is a secreted factor that stimulates neural stem cell survival possibly by enhanced EGFR signaling

Understanding how autocrine/paracrine factors regulate neural stem cell (NSC) survival and growth is fundamental to the utilization of these cells for therapeutic applications and as cellular models for the brain. In vitro, NSCs can be propagated along with neural progenitors (NPs) as neurospheres (nsphs). The nsph conditioned medium (nsph-CM) contains cell-secreted factors that can regulate NSC behavior. However, the identity and exact function of these factors within the nsph-CM has remained elusive. We analyzed the nsph-CM by mass spectrometry and identified DSD-1-proteoglycan, a chondroitin sulfate proteoglycan (CSPG), apolipoprotein E (ApoE) and cystatin C as components of the nsph-CM. Using clonal assays we show that CSPG and ApoE are responsible for the ability of the nsph-CM to stimulate nsph formation whereas cystatin C is not involved. Clonal nsphs generated in the presence of CSPG show more than four-fold increase in NSCs. Thus CSPG specifically enhances the survival of NSCs. CSPG also stimulates the survival of embryonic stem cell (ESC)-derived NSCs, and thus may be involved in the developmental transition of ESCs to NSCs. In addition to its role in NSC survival, CSPG maintains the three dimensional structure of nsphs. Lastly, CSPG's effects on NSC survival may be mediated by enhanced signaling via EGFR, JAK/STAT3 and PI3K/Akt pathways.     

A single amino acid alteration (101L) introduced into murine PrP dramatically alters incubation time of transmissible spongiform encephalopathy

A mutation equivalent to P102L in the human PrP gene, associated with Gerstmann-Straussler syndrome (GSS), has been introduced into the murine PrP gene by gene targeting. Mice homozygous for this mutation (101LL) showed no spontaneous transmissible spongiform encephalopathy (TSE) disease, but had incubation times dramatically different from wild-type mice following inoculation with different TSE sources. Inoculation with GSS produced disease in 101LL mice in 288 days. Disease was transmitted from these mice to both wild-type (226 days) and 101LL mice (148 days). In contrast, 101LL mice infected with ME7 had prolonged incubation times (338 days) compared with wild-type mice (161 days). The 101L mutation does not, therefore, produce any spontaneous genetic disease in mice but significantly alters the incubation time of TSE infection. Additionally, a rapid TSE transmission was demonstrated despite extremely low levels of disease-associated PrP.     

Study of the Insects Associated with the Floodwater Mosquito Ochlerotatus Albifasciatus (Diptera: Culicidae) and their Possible Predators in Buenos Aires Province,Argentina

Insects associated with the floodwater mosquito Ochlerotatus albifasciatus(Diptera: Culicidae) were studied from intermittent puddles in temperate Argentina in an attempt to detect the main predators. Forty-one taxa occurred in the puddles from spring to fall. Coleoptera and Diptera were dominant and diverse. Ephemeroptera and Odonata were scarce in numbers and species, and Heteroptera occurred in low numbers of species and high abundance of individuals. The main predators of immature O. albifasciatus were detected on the basis of relative abundance (ISA index), ecological dominant groups, and species association (I index). Liodessus sp. and Rhantus signatus signatus(Coleoptera: Dytiscidae) were the most abundant predators in the puddles and Liodessus sp., Lancetes marginatus(Dytiscidae) and Psorophora ciliata(Culicidae) were the most frequent. Liodessus sp. and O. albifasciatus were the best associated species in all seasons. Liodessus sp. was indistinctly associated with all larval instars and pupae, while R. signatus signatus, L. marginatus and Psorophora ciliata were more associated with the pupal stage of the mosquito. Desmopachria concolor(Coleoptera: Dytiscidae), Tropisternus lateralis limbatus and Tropisternus setiger(Coleoptera: Hydrophilidae) were other potential predators inhabiting the puddles, but their relevance was minor.     

Welfarism versus 'free enterprise': considerations of power and justice in the Philippine healthcare system

The just distribution of benefits and burdens of healthcare, at least in the contemporary Philippine context, is an issue that gravitates towards two opposing doctrines of welfarism and 'free enterprise.' Supported largely by popular opinion, welfarism maintains that social welfare and healthcare are primarily the responsibility of the government. Free enterprise (FE) doctrine, on the other hand, maintains that social welfare is basically a market function and that healthcare should be a private industry that operates under competitive conditions with minimal government control. I will examine the ethical implications of these two doctrines as they inform healthcare programmes by business and government, namely: (a) the Devolution of Health Services and (b) the Philippine Health Maintenance Organization (HMO). I will argue that these doctrines and the health programmes they inform are deficient in following respects: (1) equitable access to healthcare, (2) individual needs for premium healthcare, (3) optimal utilisation of health resources, and (4) the equitable assignment of burdens that healthcare entails. These respects, as considerations of justice, are consistent with an operational definition of 'power' proposed here as 'access to and control of resources.'     

IQPNNI: moving fast through tree space and stopping in time

An efficient tree reconstruction method (IQPNNI) is introduced to reconstruct a phylogenetic tree based on DNA or amino acid sequence data. Our approach combines various fast algorithms to generate a list of potential candidate trees. The key ingredient is the definition of so-called important quartets (IQs), which allow the computation of an intermediate tree in O(n(2)) time for n sequences. The resulting tree is then further optimized by applying the nearest neighbor interchange (NNI) operation. Subsequently a random fraction of the sequences is deleted from the best tree found so far. The deleted sequences are then re-inserted in the smaller tree using the important quartet puzzling (IQP) algorithm. These steps are repeated several times and the best tree, with respect to the likelihood criterion, is considered as the inferred phylogenetic tree. Moreover, we suggest a rule which indicates when to stop the search. Simulations show that IQPNNI gives a slightly better accuracy than other programs tested. Moreover, we applied the approach to 218 small subunit rRNA sequences and 500 rbcL sequences. We found trees with higher likelihood compared to the results by others. A program to reconstruct DNA or amino acid based phylogenetic trees is available online (http://www.bi.uni-duesseldorf.de/software/iqpnni).