Timeline: Neurospora: a model of model microbes

In the 1940s, studies with Neurospora pioneered the use of microorganisms in genetic analysis and provided the foundations for biochemical genetics and molecular biology. What has happened since this orange mould was used to show that genes control metabolic reactions? How did it come to be the fungal counterpart of Drosophila? We describe its continued use during the heyday of research with Escherichia coli and yeast, and its emergence as a biological model for higher fungi.     

The role of mathematical modelling in the control of the 2001 FMD epidemic in the UK

Mathematical models played an important role in guiding the development of the control policies in the 2001 foot-and-mouth disease epidemic in the UK. The variety of approaches that helped to guide the policy can sometimes be confusing. Here, the different modelling exercises that were developed over the course of the epidemic are reviewed, describing the difficulties in interpreting the available data and the appropriateness of the various assumptions.     

Membrane redistribution of the Escherichia coli MinD protein induced by MinE

Escherichia coli cells contain potential division sites at midcell and adjacent to the cell poles. Selection of the correct division site at midcell is controlled by three proteins: MinC, MinD, and MinE. It has previously been shown (D. Raskin and P. de Boer, Cell 91:685-694, 1997) that MinE-Gfp localizes to the midcell site in an MinD-dependent manner. We use here Gfp-MinD to show that MinD associates with the membrane around the entire periphery of the cell in the absence of the other Min proteins and that MinE is capable of altering the membrane distribution pattern of Gfp-MinD. Studies with the isolated N-terminal and C-terminal MinE domains indicated different roles for the two MinE domains in the redistribution of membrane-associated MinD.     

Dexfenfluramine and norfenfluramine: comparison of mechanism of action in feeding and brain Fos-ir studies

Dexfenfluramine (dF) and dexnorfenfluramine (dNF), its metabolite, are anorectic agents that release serotonin (5-HT) and may have a direct postsynaptic action. The effects on the anorectic effects of dF and dNF of either acute (p-chlorophenylalanine, PCPA) or chronic (5,7-dihydroxytryptamine, 5,7-DHT) brain 5-HT depletions were studied in rats and compared with the actions of a 5-HT uptake inhibitor (fluoxetine) and 5-HT(1B/2C) receptor agonists [1-(3-trifluoromethyl-phenyl)-piperazine and 1-(3-chlorophenyl) piperazine]. The anorexia caused by these agonists was enhanced in rats with 5,7-DHT lesions, possibly a result of receptor supersensitivity. In contrast, fluoxetine anorexia was somewhat reduced in one study and was unchanged in a second. Both dF and dNF anorexias were enhanced in rats with 5,7-DHT lesions. In contrast, the anorectic effects of either dF or dNF were unchanged in PCPA-treated rats relative to controls. Compared with controls, 5, 7-DHT-lesion rats showed greatly increased dF- and dNF-induced Fos-like immunoreactivity (ir) in the paraventricular (PVN) and supraoptic (SON) hypothalamic nuclei, and in the median preoptic area (MnPO), but were similar to controls in most other areas. PCPA pretreatment increased dF- and dNF-induced Fos-ir in the PVN, SON, and MnPO. In controls, equianorectic doses of dF and dNF induced Fos-ir in similar brain regions, but dNF produced relatively larger effects than dF in SON, PVN, and MnPO. The data are discussed in terms of multiple pathways in the anorectic actions of dF and dNF.     

Identification of fumonisin B1 as an inhibitor of argininosuccinate synthetase using fumonisin affinity chromatography and in vitro kinetic studies

Fumonisin B1, a fungal mycotoxin that grows on corn and other agricultural products, alters sphingolipid metabolism by inhibiting ceramide synthase. The precise mechanism of fumonisin B1 toxicity has not been completely elucidated; however, a central feature in the cytotoxicity is alteration of sphingolipid metabolism through interruption of de novo ceramide synthesis. An affinity column consisting of fumonisin B1 covalently bound to an HPLC column matrix was used to isolate a rat liver protein that consistently bound to the column. The protein was identified as argininosuccinate synthetase by protein sequencing. The enzyme-catalyzed formation of argininosuccinic acid from citrulline and aspartate by recombinant human and rat liver argininosuccinate synthetase was inhibited by fumonisin B1. Fumonisin B1 showed mixed inhibition against citrulline, aspartate, and ATP to the enzyme. Fumonisin B1 had a Ki' of approximately 6 mM with the recombinant human argininosuccinate synthase and a Ki' of 35 mM with a crude preparation of enzyme prepared from rat liver. Neither tricarballylic acid nor hydrolyzed fumonisin B1 inhibited recombinant human argininosuccinate synthetase. This is the first demonstration of fumonisin B1 inhibition of argininosuccinate synthethase, a urea cycle enzyme, which adds to the list of enzymes that are inhibited in vitro by fumonisin B1 (ceramide synthase, protein serine/threonine phosphatase). The extent of the inhibition of argininosuccinate synthetase in cells, and the possible role of this enzyme inhibition in the cellular toxicity of FB1, remains to be established.     

Configurations of polyunsaturated sesterterpenoids from the diatom, Haslea ostrearia

The partial configurations of C25 isoprenoid alkenes isolated from the diatom Haslea ostrearia Gaillon (Simonsen) have been established. A combination of NMR spectroscopy studies of the alkenes with chiral shift reagents in conjunction with soluble silver beta-diketonate complexes and enantioselective gas chromatography of oxidation products of the alkenes was used. Unexpected differences in highly branched isoprenoid isomer configurations were observed between different laboratory cultures of the alga.     

Design,parallel synthesis,and crystal structures of biphenyl antithrombotics as selective inhibitors of tissue factor FVIIa complex. Part 1: Exploration of S2 pocket pharmacophores

Factor VIIa (FVIIa), a serine protease enzyme, coupled with tissue factor (TF) plays an important role in a number of thrombosis-related disorders. Inhibition of TF·FVIIa occurs early in the coagulation cascade and might provide some safety advantages over other related enzymes. We report here a novel series of substituted biphenyl derivatives that are highly potent and selective TF·FVIIa inhibitors. Parallel synthesis coupled with structure-based drug design allowed us to explore the S2 pocket of the enzyme active site. A number of compounds with IC₅₀ value of <10 nM were synthesized. The X-ray crystal structures of some of these compounds complexed with TF·FVIIa were determined and results were applied to design the next round of inhibitors. All the potent inhibitors were tested for inhibition against a panel of related enzymes and selectivity of 17,600 over thrombin, 450 over trypsin, 685 over FXa, and 76 over plasmin was achieved. Two groups, vinyl 36b and 2-furan 36ab, were identified as the optimum binding substituents on the phenyl ring in the S2 pocket. Compounds with these two substituents are the most potent compounds in this series with good selectivity over related serine proteases. These compounds will be further explored for structure–activity relationship.     

A Few Bad Apples: A Model of Disease Influenced Agent Behaviour in a Heterogeneous Contact Environment

For diseases that infect humans or livestock, transmission dynamics are at least partially dependent on human activity and therefore human behaviour. However, the impact of human behaviour on disease transmission is relatively understudied, especially in the context of heterogeneous contact structures such as described by a social network. Here, we use a strategic game, coupled with a simple disease model, to investigate how strategic agent choices impact the spread of disease over a contact network. Using beliefs that are based on disease status and that build up over time, agents choose actions that stochastically determine disease spread on the network. An agent’s disease status is therefore a function of both his own and his neighbours actions. The effect of disease on agents is modelled by a heterogeneous payoff structure. We find that the combination of network shape and distribution of payoffs has a non-trivial impact on disease prevalence, even if the mean payoff remains the same. An important scenario occurs when a small percentage (called noncooperators) have little incentive to avoid disease. For diseases that are easily acquired when taking a risk, then even when good behavior can lead to disease eradication, a small increase in the percentage of noncooperators (less than 5%) can yield a large (up to 25%) increase in prevalence.     

Combination of Insecticide Treated Nets and Indoor Residual Spraying in Northern Tanzania Provides Additional Reduction in Vector Population Density and Malaria Transmission Rates Compared to Insecticide Treated Nets Alone: A Randomised Control Trial

Indoor residual spraying (IRS) combined with insecticide treated nets (ITN) has been implemented together in several sub-Saharan countries with inconclusive evidence that the combined intervention provides added benefit. The impact on malaria transmission was evaluated in a cluster randomised trial comparing two rounds of IRS with bendiocarb plus universal coverage ITNs, with ITNs alone in northern Tanzania. From April 2011 to December 2012, eight houses in 20 clusters per study arm were sampled monthly for one night with CDC light trap collections. Anopheles gambiae s.l. were identified to species using real time PCR Taq Man and tested for the presence of Plasmodium falciparum circumsporozoite protein. ITN and IRS coverage was estimated from household surveys. IRS coverage was more than 85% in two rounds of spraying in January and April 2012. Household coverage with at least one ITN per house was 94.7% after the universal coverage net campaign in the baseline year and the proportion of household with all sleeping places covered by LLIN was 50.1% decreasing to 39.1% by the end of the intervention year. An.gambiae s.s. comprised 80% and An.arabiensis 18.3% of the anopheline collection in the baseline year. Mean An.gambiae s.l. density in the ITN+IRS arm was reduced by 84% (95%CI: 56%-94%, p = 0.001) relative to the ITN arm. In the stratum of clusters categorised as high anopheline density at baseline EIR was lower in the ITN+IRS arm compared to the ITN arm (0.5 versus 5.4 per house per month, Incidence Rate Ratio: 0.10, 95%CI: 0.01–0.66, p-value for interaction <0.001). This trial provides conclusive evidence that combining carbamate IRS and ITNs produces major reduction in Anopheles density and entomological inoculation rate compared to ITN alone in an area of moderate coverage of LLIN and high pyrethroid resistance in An.gambiae s.s.