Anti-malarial efficacy of pyronaridine and artesunate in combination in vitro and in vivo

Abstract: Pyronaridine is a Mannich base anti-malarial with demonstrated efficacy against drug resistant Plasmodium falciparum, P. vivax, P. ovale and P. malariae. However, resistance to pyronaridine can develop quickly when it is used alone but can be considerably delayed when it is administered with artesunate in rodent malaria models. The aim of this study was to evaluate the efficacy of pyronaridine in combination with artesunate against P. falciparum in vitro and in rodent malaria models in vivo to support its clinical application. Pyronaridine showed consistently high levels of in vitro activity against a panel of six P. falciparum drug-sensitive and resistant strains (Geometric Mean IC50 = 2.24 nM, 95% CI = 1.20–3.27). In vitro interactions between pyronaridine and artesunate showed a slight antagonistic trend, but in vivo compared to pyronaridine and artesunate administered alone, the 3:1 ratio of the combination, reduced the ED90 of artesunate by ∼15.6-fold in a pyronaridine-resistant P. berghei line and by ∼200-fold in an artesunate-resistant line of P. berghei. Complete cure rates were achieved with doses of the combination above or equal to 8 mg/kg per day against P. chabaudi AS. These results indicate that the combination had an enhanced effect over monotherapy and lower daily doses of artesunate could be used to obtain a curative effect. The data suggest that the combination of pyronaridine and artesunate should have potential in areas of multi-drug resistant malaria.

Journal Acta Tropica 105 (2008) 222–228

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Assumptions about Ecological Scale and Nature Knowing Best Hiding in Environmental Decisions

Abstract: Assumptions about nature are embedded in people’s preferences for environmental policy and management. The people we interviewed justified preservationist policies using four assumptions about nature knowing best: nature is balanced, evolution is progressive, technology is suspect, and the Creation is perfect. They justified interventionist policies using three assumptions about nature: it is dynamic, inefficient, and robust. Unstated assumptions about temporal, spatial, and organizational scales further confuse discussions about nature. These findings confirm and extend findings from previous research. Data for our study were derived from interviews with people actively involved in negotiating the fate of forest ecosystems in southwest Virginia: landowners, forest advisors, scientists, state and federal foresters, loggers, and leaders in non-governmental environmental organizations. We argue that differing assumptions about nature constrain people’s vision of what environmental conditions can and should exist, thereby constraining the future that can be negotiated. We recommend promoting ecological literacy and a biocultural approach to ecological science.

Journal Conservation Ecology 6(2): 12

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Discrimination of the Commercial Seeds of Forage Crops using Ribosomal Intergenic Spacer Analysis

Abstract: The precise identification of plant species and their sub-types, and the ability to discriminate between them, are just some of the major advances that have resulted from the application of molecular biology to plant science. Of particular note in this regard is the successful application of molecular techniques to the analysis of plant DNA, which has now made the genotyping of plant materials a routine and much simplified practice. The complete genetic identification of organisms necessarily involves the determination of the genomic DNA sequence, while this is both a costly and time consuming procedure, thus yielding a major concern in most fields of biological science. As an alternative to the sequencing, a series of methodologies has been developed for the genetic identification, such as restriction fragment length polymorphism (RFLP) (Southern 1975), random amplified polymorphic DNA (RAPD) (Williams et al. 1990), amplification fragment length polymorphism (AFLP) (Vos et al. 1995) and simple sequence repeats (SSR) (Akkaya et al. 1992). It is significant, however, that each of these techniques is reliant on the stability and specificity of the genomes of the specific organisms under study, and at the same time their efficiency is dependent upon the degree of variability of corresponding genomic regions between species. Polymerase chain reaction (PCR) based methods have been extensively employed for plant genotyping in particular, due to their simplicity, rapidity and reliability (Breton et al. 2004, García-Beneytez et al. 2002). For PCR analyses, precise primer sets are usually designed to amplify selected sequences from specific organism(s). There are several limitations of the use of these standard molecular methodologies for plant identification. One such constraint is the difficulty in designing DNA markers that are specific for those plant species, such as most cultivated forage crops, that have been grown and maintained as a heterogeneous population due to their breeding habit including self-incompatibility (Baumann et al. 2000). In these cases, the design of the specific PCR primers or the identification of specific DNA sequences in their genotypes is extremely difficult, both theoretically as well as practically. In spite of this difficulty, the reliable management owing to the traceability of seed products has been a critical element in both plant breeding and in the commercial handling of plant seeds (Auer 2003, McIntosh et al. 2005). In our previous report (Ikeda et al. 2005), we showed that microbial communities among certain agronomic products could be stably detected using ribosomal intergenic spacer analysis (RISA). RISA is a DNA fingerprinting tech- nique that can identify microbial diversity by providing a unique signature for each agronomic product. In our present study, we report the potential usefulness of RISA for the discrimination of commercial seeds for forage crops and present this as an example of the traceability of agronomic products which have high levels of genetic heterogeneity.

Journal Breeding Science 56 : 185–188 (2006)

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Interspecific variation in primary seed dispersal in a tropical forest

Abstract: We investigated the relationships of seed size, dispersal mode and other species characteristics to interspecific variation in mean primary seed dispersal distances, mean annual seed production per unit basal area, and clumping of seed deposition among 41 tropical tree species on Barro Colorado Island, Panama. A hierarchical Bayesian model incorporating interannual variation in seed production was used to estimate seed dispersal, seed production, and clumping of seed rain for each species from 19 years of data for 188 seed traps on a 50-ha plot in which all adult trees were censused every 5 years. Seed dispersal was modelled as a two-dimensional Student’s T distribution with the degrees of freedom parameter fixed at 3, interannual variation in seed production per basal area was modelled as a lognormal, and the clumping of seed rain around its expected value was modelled as a negative binomial distribution. There was wide variation in seed dispersal distances among species sharing the same mode of seed dispersal. Seed dispersal mode did not explain significant variation in seed dispersal distances, but did explain significant variation in clumping: animal-dispersed species showed higher clumping of seed deposition. Among nine wind-dispersed species, the combination of diaspore terminal velocity, tree height and wind speed in the season of peak dispersal explained 40% of variation in dispersal distances. Among 31 animal-dispersed species, 20% of interspecific variation in dispersal distances was explained by seed mass (a negative effect) and tree height (a positive effect). Among all species, seed mass, tree height and dispersal syndrome explained 28% of the variation in mean dispersal distance and seed mass alone explained 45% of the variation in estimated seed production per basal area. Synthesis. There is wide variation in patterns of primary seed rain among tropical tree species. Substantial proportions of interspecific variation in seed production, seed dispersal distances, and clumping of seed deposition are explained by relatively easily measured plant traits, especially dispersal mode, seed mass, and tree height. This provides hope for trait-based generalization and modelling of seed dispersal in tropical forests.

Journal of Ecology 2008, 96, 653–667

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Temperature and Carbon Dioxide Effects on Nutritive Value of Rhizoma Peanut Herbage

Abstract: Studies assessing the impact of climate change have focused on plant production, but forage nutritive value, especially of legumes, has often been overlooked. The objective of this study was to determine the effect of increasing temperature and atmospheric CO2 concentration on chemical composition and digestibility of rhizoma peanut (RP, Arachis glabrata Benth.) leaf and stem. In vitro digestible organic matter (IVDOM), neutral and acid detergent fiber (NDF and ADF), and lignin concentrations were determined for plants grown in all combinations of two CO2 (360 and 700 mol mol 1) and four temperature environments (baseline, or ambient temperature in the greenhouse, B; B 1.5; B 3.0; and B 4.5 C). Forage was sampled every 6 to 8 wk during two growing seasons. Neither increasing CO2 nor temperature affected leaf IVDOM, but stem IVDOM declined from 562 (B) to 552 g kg 1 (B 4.5) with increasing temperature in Year 1 and from 577 to 511 g kg 1 in Year 2. Stem NDF increased with increasing temperature from 556 to 561 g kg 1 in Year 1 and from 519 to 526 g kg 1 in Year 2. Stem ADF (412 to 418 g kg 1) and lignin (80 to 93 g kg 1) increased linearly as temperature increased in 1 of 2 yr. Lignin as a proportion of NDF or ADF (lignin/NDF or lignin/ADF) accounted for a large proportion of the variation in stem IVDOM. The RP nutritive value decreases with increasing air temperature, but it is relatively unaffected by atmospheric CO2 concentrations in the range studied.

Journal Crop Science 45:316–321 (2005)

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