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Saint-Malo, France

Arkoun M.,University of Caen Lower Normandy | Arkoun M.,French National Institute for Agricultural Research | Sarda X.,University of Caen Lower Normandy | Sarda X.,French National Institute for Agricultural Research | And 10 more authors.
Journal of Experimental Botany | Year: 2012

N-fertilizer use efficiencies are affected by their chemical composition and suffer from potential N-losses by volatilization. In a field lysimeter experiment, 15N-labelled fertilizers were used to follow N uptake by Brassica napus L. and assess N-losses by volatilization. Use of urea with NBPT (urease inhibitor) showed the best efficiency with the lowest N losses (8% of N applied compared with 25% with urea alone). Plants receiving ammonium sulphate, had similar yield achieved through a better N mobilization from vegetative tissues to the seeds, despite a lower N uptake resulting from a higher volatilization (43% of applied N). Amounts of 15N in the plant were also higher when plants were fertilized with ammonium nitrate but N-losses reached 23% of applied N. In parallel, hydroponic experiments showed a deleterious effect of ammonium and urea on the growth of oilseed rape. This was alleviated by the nitrate supply, which was preferentially taken up. B. napus was also characterized by a very low potential for urea uptake. BnDUR3 and BnAMT1, encoding urea and ammonium transporters, were up-regulated by urea, suggesting that urea-grown plants suffered from nitrogen deficiency. The results also suggested a role for nitrate as a signal for the expression of BnDUR3, in addition to its role as a major nutrient. Overall, the results of the hydroponic study showed that urea itself does not contribute significantly to the N nutrition of oilseed rape. Moreover, it may contribute indirectly since a better use efficiency for urea fertilizer, which was further increased by the application of a urease inhibitor, was observed in the lysimeter study. © [2012] The Author. Source

Vetvicka V.,University of Louisville | Vashishta A.,Spinal USA | Fuentes M.,Timac Agro International Roullier Group | Baigorri R.,Timac Agro International Roullier Group | And 3 more authors.
Journal of Medicinal Food | Year: 2013

Despite the rather common presence of humic acid (HA), our full knowledge of its biological effect is still lacking. In this article, we first performed a physicochemical characterization of several HAs, and next, we evaluated their ability to affect interleukin-2 secretion, antibody secretion, wound healing (an in vitro model using HaCaT cells), cancer growth (the Lewis lung carcinoma model), and protection against hepatotoxicity. In all tested reactions, HA showed significant stimulation on immune reactions, including suppression of cancer growth and inhibition of lipopolysaccharide-induced hepatotoxicity. These effects were dependent on its chemical properties. The pleiotropic effects of HA observed in this article suggest the possible role of these compounds in human nutrition. © Mary Ann Liebert, Inc. Source

Vetvicka V.,University of Louisville | Garcia-Mina J.M.,Timac Agro International Roullier Group | Garcia-Mina J.M.,University of Navarra | Proctor M.,University of Louisville | Yvin J.-C.,Timac Agro International
Journal of Medicinal Food | Year: 2015

Humic acids (HAs) have a rather pleiotropic presence, however, their biological effects are still unclear. In this study, we focused on possible hepatoprotective effects of either HA alone or in combination with β-glucan. Using a model of experimental hepatotoxicity caused by carbon tetrachloride (CCL4), we showed that both HA and the glucan-HA combination offered significant protection against hepatotoxicity, with the combination offering superior effects. Our biochemical observations were confirmed by histological evaluation. Based on the experimental data, we conclude that whereas HA has significant effects, the synergy with glucan offers superior effects. © Mary Ann Liebert, Inc. and Korean Society of Food Science and Nutrition 2015. Source

Arkoun M.,University of Caen Lower Normandy | Arkoun M.,French National Institute for Agricultural Research | Jannin L.,University of Caen Lower Normandy | Jannin L.,French National Institute for Agricultural Research | And 11 more authors.
Plant and Soil | Year: 2013

Background and aims: Urea is the major nitrogen (N) form supplied as fertilizer in agriculture. However, urease, a nickel-dependent enzyme, allows plants to use external or internally generated urea as a nitrogen source. Since a urease inhibitor is frequently applied in conjunction with urea fertilizer, the N-metabolism of plants may be affected. The aim of this study was to determine physiological and molecular effects of nickel deficiency and a urease inhibitor on urea uptake and assimilation in oilseed rape. Methods: Plants were grown on hydroponic solution with urea as the sole N source under three treatments: plants treated with nickel (+Ni) as a control, without nickel (-Ni) and with nickel and phenylphosphorodiamidate (+Ni+PPD). Urea transport and assimilation were investigated. Results: The results show that Ni-deficiency or PPD supply led to reduced growth and reduced 15N-uptake from urea. This effect was more pronounced in PPD-treated plants, which accumulated high amounts of urea and ammonium. Thus, Ni-deficiency or addition of PPD, limit the availability of N and decreased shoot and root amino acid content. The up-regulation of BnDUR3 in roots indicated that this gene is a component of the stress response to nitrogen-deficiency. A general decline of glutamine synthetase (GS) activity and activation of glutamate dehydrogenase (GDH) and increases in its expression level were observed in control plants. At the same time, in (-N) or (+Ni+PPD) treated plants, no increases in GS or GDH activities and expression level were found. Conclusions: Overall results showed that plants require Ni as a nutrient (while most widely used nutrient solutions are devoid of Ni), whether they are grown with or without a urea supply, and that urease inhibitors may have deleterious effects at least in hydroponic grown oilseed rape. © 2012 Springer Science+Business Media B.V. Source

Vetvicka V.,University of Louisville | Baigorri R.,Timac Agro International Roullier Group | Zamarreno A.M.,Timac Agro International Roullier Group | Garcia-Mina J.M.,Timac Agro International Roullier Group | And 2 more authors.
Journal of Medicinal Food | Year: 2010

Humic acids are compounds resulting from decomposition of organic matter. Despite their common presence, our knowledge of their biological effects is limited, and current findings are controversial. We decided to evaluate the immunological effects of two different types of humic acids, differing in source and biochemical characteristics. Using both components either alone or in combination with the well-established yeast-derived immunomodulator glucan, we measured their effects on both the cellular (phagocytosis and tumor suppression) and humoral (antibody production and cytokine secretion) branches of immune reactions. In summary, our results suggest that humic acids are biologically active immunodulators affecting both the humoral and cellular branches of immune reactions. In addition, the two humic acids studied here are working in synergy in stimulation of the immune reaction, supporting further studies of these natural immunomodulators. © Mary Ann Liebert, Inc. Source

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