• David Lloyd

      Articles written in Journal of Biosciences

    • Hydrogen peroxide is a product of oxygen consumption byTrichomonas vaginalis

      Alan Chapman David J Linstead David Lloyd

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      The amitochondriate sexually-transmitted human parasitic protozoanTrichomonas vaginalis (Bushby strain) grown anaerobically on complex medium containing cysteine and ascorbic acid consumed O2 avidly (6.9 μM min−1 per 106 organisms) with an apparentKm value of 5.1 μM O2 : O2 uptake was inhibited by O2 > 120 μM. Spectrophotometric assays in the presence of microperoxidase (419-407 nm) indicated that H2O2 was produced and that inhibition by high O2 concentrations was again evident. Hydrogenosomes oxidizing pyruvate in the presence of ADP and succinate showed similar patterns of O2 consumption, H2O2 production (33.5 pmol min−1 per mg protein), and O2 inhibition. Cytosolic NADH oxidase gave no detectable H2O2, whereas the cytosolic NADPH oxidase produced H2O2 at a rate (43 pmol min−1 per mg protein) greater than that of hydrogenosomes. These results are discussed in relation to the oxidative stress experienced by the pathogen in its natural habitat.

    • Biological time is fractal: Early events reverberate over a life time

      David Lloyd

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    • Alfred Russel Wallace deserves better

      David Lloyd Julian Wimpenny Alfred Venables

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      During 2009, while we were celebrating Charles Darwin and his The origin of species, sadly, little was said about the critical contribution of Alfred Russel Wallace (1823–1913) to the development of the theory of evolution. Like Darwin, he was a truly remarkable nineteenth century intellect and polymath and, according to a recent book by Roy Davies (The Darwin conspiracy: origins of a scientific crime), he has a stronger claim to the Theory of Evolution by Natural Selection than has Darwin. Here we present a critical comparison between the contributions of the two scientists. Sometimes referred to as ‘The other beetle-hunter’ and largely neglected for many decades, Wallace had a far greater experience of collecting and investigating animals and plants from their native habitats than had Darwin. He was furthermore much more than a pioneer biogeographer and evolutionary theorist, and also made contributions to anthropology, ethnography, geology, land reform and social issues. However, being a more modest, self-deprecating man than Darwin, and lacking the latter’s establishment connections, Wallace’s contribution to the theory of evolution was not given the recognition it deserved and he was undoubtedly shabbily treated at the time. It is time that Wallace’s relationship with Darwin is reconsidered in preparation for 2013, the centenary of Wallace’s death, and he should be recognized as at least an equal in the Wallace–Darwin theory of evolution.

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