The importance of temperature and moisture to the egg-laying behaviour of a pest slug, Deroceras reticulatum

Oviposition behaviour is important when modelling the population dynamics of many invertebrates. The numbers of eggs laid are frequently used to describe fecundity, but this measure may differ significantly from realised fecundity. Oviposition has been shown to be important when describing the dynamics of slug populations, which are important agricultural pests. The numbers of eggs laid by Deroceras reticulatum and their viability were measured across a range of 16 temperature (4, 10, 15 and 23 degrees C) by moisture (33%, 42%, 53% and 58% by dry soil weight) experimental combinations. A fitted quadratic response surface model was used to estimate how D. reticulatum adjusted its egg laying to the surrounding temperature and moisture conditions, with most eggs being laid at a combination of 53% soil moisture and 18 degrees C. The number and proportion of viable eggs also covaried with temperature and moisture, suggesting that D. reticulatum may alter their investment in reproduction to maximise their fitness. We have shown that the number of viable eggs differs from the total number of eggs laid by D. reticulatum. Changes in egg viability with temperature and moisture may also be seen in other species and should be considered when modelling populations of egg-laying invertebrates.

ONeSAMP: a program to estimate effective population size using approximate Bayesian computation

The estimation of effective population size from one sample of genotypes has been problematic because most estimators have been proven imprecise or biased. We developed a web-based program, ONeSAMP that uses approximate Bayesian computation to estimate effective population size from a sample of microsatellite genotypes. ONeSAMP requires an input file of sampled individuals' microsatellite genotypes along with information about several sampling and biological parameters. ONeSAMP provides an estimate of effective population size, along with 95% credible limits. We illustrate the use of ONeSAMP with an example data set from a re-introduced population of ibex Capra ibex.

Efficient and cost-effective experimental determination of kinetic constants and data: the success of a Bayesian systematic approach to drug transport, receptor binding, continuous culture and cell transport kinetics

Details about the parameters of kinetic systems are crucial for progress in both medical and industrial research, including drug development, clinical diagnosis and biotechnology applications. Such details must be collected by a series of kinetic experiments and investigations. The correct design of the experiment is essential to collecting data suitable for analysis, modelling and deriving the correct information. We have developed a systematic and iterative Bayesian method and sets of rules for the design of enzyme kinetic experiments. Our method selects the optimum design to collect data suitable for accurate modelling and analysis and minimises the error in the parameters estimated. The rules select features of the design such as the substrate range and the number of measurements. We show here that this method can be directly applied to the study of other important kinetic systems, including drug transport, receptor binding, microbial culture and cell transport kinetics. It is possible to reduce the errors in the estimated parameters and, most importantly, increase the efficiency and cost-effectiveness by reducing the necessary amount of experiments and data points measured. (C) 2003 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Cultural techniques for improvement in biocontrol potential of fungal antagonists for biological control of Armillaria root rot of strawberry plants under glasshouse conditions

Several in vitro and in vivo experiments were conducted to develop an effective technique for culturing potential fungal antagonists (isolates of Trichoderma harzianum, Dactylium dendroides, Chaetomium olivaceum and one unidentified fungus) selected for activity against Armillaria mellea. The antagonists were inoculated onto (1) live spawn of the oyster mu shroom (Pleurotus ostreatus), (2) extra-moistened or sucrose-enriched mushroom composts containing living or autoclaved mycelia of P. ostreatus or Agaricus bisporus (button mushroom), (3) pasteurized compost with or without A. bisporus mycelium, wheat bran, wheat germ and (4) spent mushroom composts with living mycelia of A. bisporus, P. ostreatus or Lentinus edodes (the Shiitake mushroom). In one experiment, a representative antagonist (isolate Th2 of T. harzianum) was grown together with the A. bisporus mycelium, while in another one, the antagonist was first grown on wheat germ or wheat bran and then on mushroom compost with living mycelium of A. bisporus. Some of the carrier substrates were then added to the roots of potted strawberry plants in the glasshouse to evaluate their effectiveness against the disease. The antagonists failed to grow on the spawn of P. ostreatus even after reinoculations and prolonged incubation. Providing extra moisture or sucrose enrichment also did not improve the growth of Th2 on mushroom composts in the presence of living mycelia of A. bisporus or P. ostreatus. The antagonist, however, grew rapidly and extensively on mushroom compost with autoclaved mycelia, and also on wheat germ and wheat bran. Colonization of the substrates by the antagonist was positively correlated with its effectiveness in the glasshouse studies. Whereas only 33.3% of the inoculated control plants survived in one experiment monitored for 560 days, 100% survival was achieved when Th2 was applied on wheat germ or wheat bran. Growth of the antagonist alone on pasteurized or sterilized compost (without A. bisporus mycelia) and simultaneous growth of the antagonist and mushroom on pasteurized compost did not improve survival over the inoculated controls, but growth over mushroom compost with the living mycelium resulted in 50% survival rate. C. olivaceum isolate Co was the most effective, resulting in overall survival rate of 83.3% compared with only 8.3% for the inoculated and 100% for the uninoculated (healthy) controls. This antagonist gave the highest survival rate of 100% on spent mushroom compost with L. edodes. T harzianum isolate Th23, with 75% survival rate, was the most effective on spent mushroom compost with P. ostreatus, while D. dendroides isolate SP resulted in equal survival rates of 50% on all the three mushroom composts.

Comparative evaluation of a new effective population size estimator based on approximate Bayesian computation

We describe and evaluate a new estimator of the effective population size (N-e), a critical parameter in evolutionary and conservation biology. This new "SummStat" N-e. estimator is based upon the use of summary statistics in an approximate Bayesian computation framework to infer N-e. Simulations of a Wright-Fisher population with known N-e show that the SummStat estimator is useful across a realistic range of individuals and loci sampled, generations between samples, and N-e values. We also address the paucity of information about the relative performance of N-e estimators by comparing the SUMMStat estimator to two recently developed likelihood-based estimators and a traditional moment-based estimator. The SummStat estimator is the least biased of the four estimators compared. In 32 of 36 parameter combinations investigated rising initial allele frequencies drawn from a Dirichlet distribution, it has the lowest bias. The relative mean square error (RMSE) of the SummStat estimator was generally intermediate to the others. All of the estimators had RMSE > 1 when small samples (n = 20, five loci) were collected a generation apart. In contrast, when samples were separated by three or more generations and Ne less than or equal to 50, the SummStat and likelihood-based estimators all had greatly reduced RMSE. Under the conditions simulated, SummStat confidence intervals were more conservative than the likelihood-based estimators and more likely to include true N-e. The greatest strength of the SummStat estimator is its flexible structure. This flexibility allows it to incorporate any, potentially informative summary statistic from Population genetic data.

Mutant alleles at the rugosus loci in pea affect seed moisture sorption isotherms and the relations between seed longevity and moisture content

Pea (Pisum sativum L.) mutant near-isogenic lines (RRrbrb, rrRbRb, rrrbrb) with lower starch but higher lipid contents, brought about by lesions in the starch biosynthetic pathway, had seed moisture sorption isotherms displaced below that of the wild type (RRRbRb). The negative logarithmic relationship between seed longevity and seed storage moisture content (%, f.wt basis), determined in hermetic storage at 65 °C, also differed: longevity in the mutant near-isogenic lines was poorer and less sensitive to moisture content than in the wild type (i.e. CW was lower). The low-moisture-content limit (mc) to this relation also differed, being lower in the mutant near-isogenic lines (5.4–5.9%) than in the wild type (6.1%). In contrast, all four near-isogenic lines showed no difference (P >0.25) in the negative semi-logarithmic relationship between equilibrium relative humidity (ERH) and seed longevity. It is concluded that the effect of these alleles at the r and rb loci on seed longevity was largely indirect; a consequence of their effect on seed composition and hence on moisture sorption isotherms. However, this explanation could not be invoked at moisture contents below mc where differences in longevity remained substantial (RRRbRb double that of rrrbrb). Hence, these mutant alleles affected seed longevity directly at very low moisture contents.

Mapping antimalarial pharmacophores as a useful tool for the rapid discovery of drugs effective in vivo: design, construction, characterization, and pharmacology of metaquine

Resistant strains of Plasmodium falciparum and the unavailability of useful antimalarial vaccines reinforce the need to develop new efficacious antimalarials. This study details a pharmacophore model that has been used to identify a potent, soluble, orally bioavailable antimalarial bisquinoline, metaquine (N,N'-bis(7-chloroquinolin-4-yl)benzene-1,3-diamine) (dihydrochloride), which is active against Plasmodium berghei in vivo (oral ID50 of 25 mu mol/kg) and multidrug-resistant Plasmodium falciparum K1 in vitro (0.17 mu M). Metaquine shows strong affinity for the putative antimalarial receptor, heme at pH 7.4 in aqueous DMSO. Both crystallographic analyses and quantum mechanical calculations (HF/6-31+G*) reveal important regions of protonation and bonding thought to persist at parasitic vacuolar pH concordant with our receptor model. Formation of drug-heme adduct in solution was confirmed using high-resolution positive ion electrospray mass spectrometry. Metaquine showed strong binding with the receptor in a 1: 1 ratio (log K = 5.7 +/- 0.1) that was predicted by molecular mechanics calculations. This study illustrates a rational multidisciplinary approach for the development of new 4-aminoquinoline antimalarials, with efficacy superior to chloroquine, based on the use of a pharmacophore model.

6,6 '-bis (5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-benzo[1,2,4]triazin-3-yl) [2,2 ']bipyridine, an effective extracting agent for the separation of americium(III) and curium(III) from the lanthanides

The extraction of americium(III), curium(III), and the lanthanides(III) from nitric acid by 6,6'- bis (5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-benzo[1,2,4]triazin-3-yl)-[2,2'] bipyridine (CyMe4-BTBP) has been studied. Since the extraction kinetics were slow, N,N'-dimethyl-N,N'-dioctyl-2-(2-hexyloxy-ethyl)malonamide (DMDOHEMA) was added as a phase transfer reagent. With a mixture of 0.01 M CyMe4-BTBP + 0.25 M DMDOHEMA in n -octanol, extraction equilibrium was reached within 5 min of mixing. At a nitric acid concentration of 1 M, an americium(III) distribution ratio of approx. 10 was achieved. Americium(III)/lanthanide(III) separation factors between 50 (dysprosium) and 1500 (lanthanum) were obtained. Whereas americium(III) and curium(III) were extracted as disolvates, the stoichiometries of the lanthanide(III) complexes were not identified unambiguously, owing to the presence of DMDOHEMA. In the absence of DMDOHEMA, both americium(III) and europium(III) were extracted as disolvates. Back-extraction with 0.1 M nitric acid was thermodynamically possible but rather slow. Using a buffered glycolate solution of pH=4, an americium(III) distribution ratio of 0.01 was obtained within 5 min of mixing. There was no evidence of degradation of the extractant, for example, the extraction performance of CyMe4-BTBP during hydrolylsis with 1 M nitric acid did not change over a two month contact.

Condensation and moisture transport in cold roofs: effect of roof underlay

Cold pitched roofs, with their form of construction situating insulation on a horizontal ceiling, are intrinsically vulnerable to condensation. This study reports the results derived from using a simulation package (Heat, Air and Moisture modelling tool, or HAM-Tools) to investigate the risk of condensation in cold pitched roofs in housing fitted with a vapour-permeable underlay (VPU) of known characteristics. In order to visualize the effect of the VPUs on moisture transfer, several scenarios were modelled, and compared with the results from a conventional bituminous felt with high resistance (200 MNs/g, Sd = 40 m). The results indicate that ventilation is essential in the roof to reduce condensation. However, a sensitivity analysis proved that reducing the overall tightness of the ceiling and using lower-resistance VPUs would help in controlling condensation formation in the roof. To a large extent, the proposed characteristic performance of the VPU as predicted by manufacturers and some researchers may only be realistic if gaps in the ceiling are sealed completely during construction, which may be practically difficult given current construction practice.