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Steven J.T. Jackson,Keith W. Singletary,Laura L. Murphy,Richard C. Venema,Andrew J. Young 한국식품영양과학회 2016 Journal of medicinal food Vol.19 No.1
Phytonutrients have rapidly emerged as natural food chemicals possessing multifaceted biological actions thatmay support beneficial health outcomes. Among the vast array of phytonutrients currently being studied, sulforaphane, curcumin, quercetin, and resveratrol have been frequently reported to stimulate the expression of endogenous detoxification enzymes and may thereby facilitate the neutralization of otherwise harmful environmental agents. Some of these same phytonutrients, however, have also been implicated in disrupting normal cell proliferation and hence may possess toxic properties in and of themselves. In this study, we characterize the respective minimum threshold concentrations of the aforementioned phytonutrients in Hepa1c1c7 cells that stimulate NAD(P)H:quinone oxidoreductase (NQO1), a key enzyme in the hepatic neutralization of menadione, other biological oxidants, and some environmental carcinogens. Moreover, our findings demonstrate that relatively low concentrations of either sulforaphane or curcumin significantly (P < .05) increase NQO1 protein expression and activity without triggering G2/M cell cycle arrest or mitotic catastrophe. The minimal quercetin concentration inducing NQO1, however, was 100-fold higher than that which disrupted mitosis. Also, while resveratrol modestly stimulated NQO1, the minimally effective resveratrol concentration concomitantly induced evidence of cellular apoptosis. Taken together, these findings indicate that only particular phytonutrients are likely efficacious in upregulating NQO1 activity without also leading to hepatic cytotoxicity.
Characteristics of perchlorate formation via photodissociation of aqueous chlorite
Kang, Namgoo,Anderson, Todd A.,Rao, Balaji,Jackson, W. Andrew CSIRO Publishing 2009 Environmental chemistry Vol.6 No.1
<P> Environmental context. Perchlorate, a well-known thyroid disruptor with both man-made and natural sources represents a major environmental problem in the United States but little information is available concerning the source of natural perchlorate. Previous research has demonstrated that perchlorate can be produced from exposure of some chlorine compounds to ultraviolet radiation, but no information was available how quickly or comparatively how much perchlorate was formed. The results of the present study can be used to evaluate the potential impact of ultraviolet processes on the overall occurrence of perchlorate in the environment. Abstract. The present study provides new and important information on perchlorate (ClO4-) formation through ultraviolet (UV) photodissociation of unbuffered chlorite (ClO2-) solutions from the standpoint of kinetics under three different wavelength regimes having maximum emissions, λe,max, at 235.7, 300 and 350 nm. ClO4- production rates and yields were in general found to be inversely related, with higher yields and lower rates at higher wavelengths, and vice versa. A simple kinetic model for ClO4- production as a function of the ClO2- first-order decay constant and starting concentration was fitted to the experimental data, resulting in the calculation of a rate constant, k2, which is a function of light-source characteristics. Further, a conceptual scheme for ClO4- formation via photochemical reactions between oxychlorine species was proposed based on the experimental results and available literature. The present study is a further step towards understanding the formation of ClO4- from the photolysis of its precursors. </P>
Marinova, Margarita M.,Mckay, Christopher P.,Pollard, Wayne H.,Heldmann, Jennifer L.,Davila, Alfonso F.,Andersen, Dale T.,Jackson, W. Andrew,Lacelle, Denis,Paulsen, Gale,Zacny, Kris Cambridge University Press 2013 Antarctic science Vol.25 No.4
<B>Abstract</B><P>We report on 475 measurements of depth to ice-cemented ground in four high-elevation valleys of the Quartermain Mountains, McMurdo Dry Valleys, Antarctica. These valleys have pervasive ice-cemented ground, and the depth to ice-cemented ground and the ice composition may be indicators of climate change. In University Valley, the measured depth to ice-cemented ground ranges from 0-98 cm. There is an overall trend of increasing depth to ice-cemented ground with distance from a small glacier at the head of the valley, with a slope of 32 cm depth per kilometre along the valley floor. For Farnell Valley, the depth to ice-cemented ground is roughly constant (<I>c.</I> 30 cm) in the upper and central parts of the valley, but increases sharply as the valley descends into Beacon Valley. The two valleys north of University Valley also have extensive ice-cemented ground, with depths of 20-40 cm, but exhibit no clear patterns of ice depth with location. For all valleys there is a tendency for the variability in depth to ice-cemented ground at a site to increase with increasing depth to ice. Snow recurrence, solar insolation, and surface albedo may all be factors that cause site to site variations in these valleys.</P>