Browsing by Author "Robinson, T."

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    Developing Artemisia annua for the extraction of artemisinin to treat multi-drug resistant malaria
    (National Academy of Sciences of Belarus, 2016-09) Arroo, R. R. J.; Atkinson, C. J.; Bentley, S.; Burns, C.; Davies, M. J.; Dungey, N.; Flockhart, I.; Hill, C.; Robinson, T.; Smith, L. M. J.; Woolley, J. G.
    Semi-synthetic derivatives of the sesquiterpene artemisinin have worldwide become the main treatment for P. falciparum malaria. Artemisinin-combination therapies (ACTs), containing artemether or artesunate combined with non-isoprenoid drugs, are recommended as first line treatment by the World Health Organization, particularly in areas where resistance against quinine and quinine analogues has developed. Whereas methods for the total synthesis of artemisinin have been developed, artemisinin extracted from the leaves of Artemisia annua L. (Asteraceae) is still the preferred source for commercial production of antimalarial drugs. The biosynthetic pathway of artemisinin is well-known and a number of genes that regulate artemisinin biosynthesis have been identified. Various attempts have been made to enhance the yield of artemisinin in crops or plant cell cultures through the use of genetic engineering. Another approach has been semi-synthesis of artemisinin via artemisinic acid in genetically engineered yeast. Although genetic engineering holds a great promise for the future, currently the largest improvements in artemisinin yield have been obtained through creation of high-yielding varieties by classical breeding programs combined with modern agricultural production techniques.
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    Enhancement of artemisinin concentration and yield in response to optimization of nitrogen and potassium supply to Artemisia annua.
    (Oxford University Press, 2009-05-30) Davies, M. J.; Atkinson, C. J.; Burns, C.; Woolley, J. G.; Hipps, N. A.; Arroo, R. R. J.; Dungey, N.; Robinson, T.; Brown, P.; Flockhart, I.; Hill, C.; Smith, Lydia; Bentley, S.
    Background and Aims: The resurgence of malaria, particularly in the developing world, is considerable and exacerbated by the development of single-gene multi-drug resistances to chemicals such as chloroquinone. Drug therapies, as recommended by the World Health Organization, now include the use of antimalarial compounds derived from Artemisia annua – in particular, the use of artemisinin-based ingredients. Despite our limited knowledge of its mode of action or biosynthesis there is a need to secure a supply and enhance yields of artemisinin. The present study aims to determine how plant biomass can be enhanced while maximizing artemisinin concentration by understanding the plant's nutritional requirements for nitrogen and potassium. Methods: Experiments were carried out, the first with differing concentrations of nitrogen, at 6, 31, 56, 106, 206 or 306 mg L–1 being applied, while the other differing in potassium concentration (51, 153 or 301 mg L–1). Nutrients were supplied in irrigation water to plants in pots and after a growth period biomass production and leaf artemisinin concentration were measured. These data were used to determine optimal nutrient requirements for artemisinin yield. Key Results: Nitrogen nutrition enhanced plant nitrogen concentration and biomass production successively up to 106 mg N L–1 for biomass and 206 mg N L–1 for leaf nitrogen; further increases in nitrogen had no influence. Artemisinin concentration in dried leaf material, measured by HPLC mass spectroscopy, was maximal at a nitrogen application of 106 mg L–1, but declined at higher concentrations. Increasing potassium application from 51 to 153 mg L–1 increased total plant biomass, but not at higher applications. Potassium application enhanced leaf potassium concentration, but there was no effect on leaf artemisinin concentration or leaf artemisinin yield. Conclusions: Artemisinin concentration declined beyond an optimal point with increasing plant nitrogen concentration. Maximization of artemisinin yield (amount per plant) requires optimization of plant biomass via control of nitrogen nutrition.
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    Screening a diverse collection of Artemisia annua germplasm accessions for the antimalarial compound, artemisinin.
    (Cambridge University Press, 2012) Cockram, J.; Hill, C.; Burns, C.; Flockhart, I.; Robinson, T.; Dungey, N.; Bentley, S.; Arroo, R. R. J.; Woolley, J. G.; Atkinson, C. J.; Davies, M. J.; Greenland, A. J.; Smith, L. M. J.
    The antimalarial drug artemisinin (ART) is commercially extracted from the medicinal plant Artemisia annua L. Here, we report the screening of 70 A. annua plants representing 14 diverse germplasm accessions sourced from around the world, and identify lines containing >2% ART. These extremely high-yielding individuals have been maintained as vegetative clones, and they represent promising germplasm resources for future A. annua breeding programmes.
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    Toward a processual theory of transformation
    (Elsevier, 2018-12-15) Murray, J.B.; Brokalaki, Z.; Bhogal-Nair, Anoop; Cermin, A.; Chelekis, J.; Cocker, H.; Eagar, T.; McAlexander, B.; Patrick, R.; Robinson, T.; Scholz, J.; Thyroff, A.; Zavala, M.
    This paper proposes that popular culture has the potential to be progressive, opening the possibility for social change and the motivation to drive it. Based on a hermeneutic analysis of twelve popular culture cases, a processual theory of transformation is constructed. Processual theories embrace and emphasize a dynamic temporal sequence where one conceptual category sets the stage for the next. They are useful in helping to explain how complex social processes unfold over time. The processual theory presented in this paper is based on four concepts: contradictions, emotions, progressive literacy, and praxis. This theory is useful to the TCR movement in three ways: first, the theory is descriptive, helping TCR researchers understand how society changes over time; second, the theory is prescriptive, enabling TCR researchers to think about potential social change strategies; and finally, the process used in this research serves as a paradigmatic frame for theory development in TCR.