Interaction of flavonoids with bovine serum albumin: a fluorescence quenching study

The interaction between four flavonoids (catechin, epicatechin, rutin and quercetin) and bovine serum albumin (BSA) was investigated using tryptophan fluorescence quenching. Quenching constants were determined using the Stern-Volmer equation to provide a measure of the binding affinity between the flavonoids and BSA. The binding affinity was found to be strongest for quercetin, and ranked in the order quercetin>rutin>epicatechin=catechin. The pH in the range of 5 to 7.4 does not affect significantly (p<0.05) the association of rutin, epicatechin and catechin with BSA, but quercetin exhibited a stronger affinity at pH 7.4 than at lower pH (p<0.05). Quercetin has a total quenching effect on BSA tryptophan fluorescence at a molar ratio of 10:1 and rutin at approximately 25:1. However, epicatechin and catechin did not fully quench tryptophan fluorescence over the concentration range studied. Furthermore, the data suggested that the association between flavonoids and BSA did not change molecular conformation of BSA and that hydrogen bonding, ionic and hydrophobic interaction are equally important driving forces for protein-flavonoid association.

Strategy instruction in listening for lower-intermediate learners of French

Second language listening has historically proved to be a difficult skill. Strategy instruction studies have sought to bring about improvements in subjects’ listening but with mixed results. This lack of success might be due to the nature of listening strategy theory and its influence on conceptualizations of listening strategy instruction. The current study, based on an initial descriptive investigation of a specific population of learners, measured the effects of strategy instruction on both the listening performance and self-efficacy of 68 lower-intermediate learners of French in England, against a comparison group. Moreover, the effects of high- and low-scaffolded interventions were compared. Results suggest that the program improved listening proficiency and learners’ confidence about listening. Implications for pedagogy and strategy theory are discussed.

Rates of production of acetate, propionate, and butyrate in the rumen of lactating dairy cows given normal and low-roughage diets

Five lactating dairy cows with a permanent cannula in the rumen were given ( kg DM/d) a normal diet (7.8 concentrates, 5.1 hay) or a low-roughage (LR) diet (11.5 concentrates, 1.2 hay) in two meals daily in a two-period crossover design. Milk fat (g/kg) was severely reduced on diet LR. To measure rates of production of individual volatile fatty acids (VFA) in the rumen, 0.5 mCi 1-C-14-acetic acid, 2-C-14-propionic acid, or 1-C-14-n-butyric acid were infused into the rumen for 22 h at intervals of 2 to 6 d; rumen samples were taken over the last 12 h. To measure rumen volume, we infused Cr-EDTA into the rumen continuously, and polyethylene glycol was injected 2 h before the morning feed. Results were very variable, so volumes measured by rumen emptying were used instead. Net production of propionic acid more than doubled on LR, but acetate and butyrate production was only numerically lower. Net production rates pooled across both diets were significantly related to concentrations for each VFA. Molar proportions of net production were only slightly higher than molar proportions of concentrations for acetate and propionate but were lower for butyrate. The net energy value (MJ/d) of production of the three VFA increased from 89.5 on normal to 109.1 on LR, equivalent to 55 and 64% of digestible energy, respectively. Fully interchanging, three-pool models of VFA C fluxes are presented. It is concluded that net production rates of VFA can be measured in non-steady states without the need to measure rumen volumes.

Oestrogenic activity of benzyl salicylate, benzyl benzoate and butylphenylmethylpropional (Lilial) in MCF7 human breast cancer cells in vitro

Benzyl salicylate, benzyl benzoate and butylphenylmethylpropional (Lilial) are added to bodycare cosmetics used around the human breast. We report here that all three compounds possess oestrogenic activity in assays using the oestrogen-responsive MCF7 human breast cancer cell line. At 3 000 000-fold molar excess, they were able to partially displace [H-3]oestradiol from recombinant human oestrogen receptors ER alpha and ER beta, and from cytosolic ER of MCF7 cells. At concentrations in the range of 5 x 10(-5) to 5 x 10(-4) M, they were able to increase the expression of a stably integrated oestrogen-responsive reporter gene (ERE-CAT) and of the endogenous oestrogen-responsive pS2 gene in MCF7 cells, albeit to a lesser extent than with 10(-8) M 17 beta-oestradiol. They increased the proliferation of oestrogen-dependent MCF7 cells over 7 days, which could be inhibited by the antioestrogen fulvestrant, suggesting an ER-mediated mechanism. Although the extent of stimulation of proliferation over 7 days was lower with these compounds than with 10(-8) M 17 beta-oestradiol, given a longer time period of 35 days the extent of proliferation with 10(-4) M benzyl salicylate, benzyl benzoate or butylphenylmethylpropional increased to the same magnitude as observed with 10(-8) M 17 beta-oestradiol over 14 days. This demonstrates that benzyl salicylate, benzyl benzoate and butylphenylmethylpropional are further chemical components of cosmetic products which give oestrogenic responses in a human breast cancer cell line in culture. Further research is now needed to investigate whether oestrogenic responses are detectable using in vivo models and the extent to which these compounds might be absorbed through human skin and might enter human breast tissues. Copyright (C) 2009 John Wiley & Sons, Ltd.

Comparative study of oestrogenic properties of eight phytoestrogens in MCF7 human breast cancer cells

Previous studies have compared the oestrogenic properties of phytoestrogens in a wide variety of disparate assays. Since not all phytoestrogens have been tested in each assay, this makes inter-study comparisons and ranking oestrogenic potency difficult. In this report, we have compared the oestrogen agonist and antagonist activity of eight phytoestrogens (genistein, daidzein, equol, miroestrol, deoxymiroestrol, 8-prenylnaringenin, coumestrol and resveratrol) in a range of assays all based within the same receptor and cellular context of the MCF7 human breast cancer cell line. The relative binding of each phytoestrogen to oestrogen receptor (ER) of MCF7 cytosol was calculated from the molar excess needed for 50 % inhibition of [H-3]oestradiol binding (IC50), and was in the order coumestrol (35x)/8-prenylnaringenin (45 x)/deoxymiroestrol (50 x) > miroestrol (260x) > genistein (1000x) > equol (4000x) > daidzein (not achieved: 40 % inhibition at 10(4)-fold molar excess) > resveratrol (not achieved: 10 % inhibition at 10(5)-fold molar excess). For cell-based assays, the rank order of potency (estimated in terms of the concentration needed to achieve a response equivalent to 50 % of that found with 17 beta-oestradiol (IC50)) remained very similar for all the assays whether measuring ligand ability to induce a stably transfected oestrogen-responsive ERE-CAT reporter gene, cell growth in terms of proliferation rate after 7 days or cell growth in terms of saturation density after 14 days. The IC50 values for these three assays in order were for 17 beta-oestradiol (1 x 10-(11) M, 1 x 10-(11) M, 2 x 10(-11) M), and in rank order of potency for the phytoestrogens, deoxymiroestrol (1 x 10(-10) M, 3 x 10(-11) M, 2 x 10(-11) M) > miroestrol (3 x 10(-10) M, 2 x 10(-11) M, 8 x 10(-11) M) > 8-prenylnaringenin (1 x 10(-9) M, 3 x 10(-10) M, 3 x 10(-10) M) > cournestrol (3 x 10(-8) M, 2 x 10(-8) M, 3 x 10(-8) M) > genistein (4 x 10(-8) M, 2 x 10(-8) M, 1 x 10(-8) M)/equol (1 x 10(-7) M, 3 x 10(-8) M, 2 x 10(-8) M) > daidzein (3 x 10(-7) M, 2 x 10(-7) M, 4 x 10(-8) M) > resveratrol (4 x 10(-6) M, not achieved, not achieved). Despite using the same receptor context of the MCF7 cells, this rank order differed from that determined from receptor binding. The most marked difference was for cournestrol and 8-prenylnaringenin which both displayed a relatively potent ability to displace [3H]oestradiol from cytosolic ER compared with their much lower activity in the cell-based assays. Albeit at varying concentrations, seven of the eight phytoestrogens (all except resveratrol) gave similar maximal responses to that given by 17 beta-oestradiol in cell-based assays which makes them full oestrogen agonists. We found no evidence for any oestrogen antagonist action of any of these phytoestrogens at concentrations of up to 10(-6) M on either reporter gene induction or on stimulation of cell growth. (c) 2005 Elsevier Ltd. All rights reserved.

Oestrogenic activity of p-hydroxybenzoic acid (common metabolite of paraben esters) and methylparaben in human breast cancer cell lines

This paper addresses the question of whether p-hydroxybenzoic acid, the common metabolite of parabens, possesses oestrogenic activity in human breast cancer cell lines. The alkyl esters of p-hydroxybenzoic acid (parabens) are used widely as preservatives in consumer products to which the human population is exposed and have been shown previously to possess oestrogenic activity and to be present in human breast tumour tissue, which is an oestrogen-responsive tissue. Recent work has shown p-hydroxybenzoic acid to give an oestrogenic response in the rodent uterotrophic assay. We report here that p-hydroxybenzoic acid possesses oestrogenic activity in a panel of assays in human breast cancer cell lines. p-Hydroxybenzoic acid was able to displace [H-3]oestradiol from cytosolic oestrogen receptor of MCF7 human breast cancer cells by 54% at 5 x 10(6)-fold molar excess and by 99% at 10(7)-fold molar excess. It was able to increase the expression of a stably integrated oestrogen responsive reporter gene (ERE-CAT) at a concentration of 5 x 10(-4) M in MCF7 cells after 24 h and 7 days, which could be inhibited by the anti-oestrogen ICI 182 780 (Faslodex, fulvestrant). Proliferation of two human breast cancer cell lines (MCF7, ZR-75-1) could be increased by 10(-5) M p-hydroxybenzoic acid. Following on from previous studies showing a decrease in oestrogenic activity of parabens with shortening of the linear alkyl chain length, this study has compared the oestrogenic activity of p-hydroxybenzoic acid where the alkyl grouping is no longer present with methylparaben, which has the shortest alkyl group. Intrinsic oestrogenic activity of p-hydroxybenzoic acid was similar to that of methylparaben in terms of relative binding to the oestrogen receptor but its oestrogenic activity on gene expression and cell proliferation was lower than that of methylparaben. It can be concluded that removal of the ester group from parabens does not abrogate its oestrogenic activity and that p-hydroxybenzoic acid can give oestrogenic responses in human breast cancer cells. Copyright (C) 2005 John Wiley & Sons, Ltd.

Factors controlling the distribution of ozone in the West African lower troposphere during the AMMA (African Monsoon Multidisciplinary Analysis) wet season campaign

Ozone and its precursors were measured on board the Facility for Airborne Atmospheric Measurements (FAAM) BAe 146 Atmospheric Research Aircraft during the monsoon season 2006 as part of the African Monsoon Multidisciplinary Analysis (AMMA) campaign. One of the main features observed in the west African boundary layer is the increase of the ozone mixing ratios from 25 ppbv over the forested area (south of 12 degrees N) up to 40 ppbv over the Sahelian area. We employ a two-dimensional ( latitudinal versus vertical) meteorological model coupled with an O-3-NOx-VOC chemistry scheme to simulate the distribution of trace gases over West Africa during the monsoon season and to analyse the processes involved in the establishment of such a gradient. Including an additional source of NO over the Sahelian region to account for NO emitted by soils we simulate a mean NOx concentration of 0.7 ppbv at 16 degrees N versus 0.3 ppbv over the vegetated region further south in reasonable agreement with the observations. As a consequence, ozone is photochemically produced with a rate of 0.25 ppbv h(-1) over the vegetated region whilst it reaches up to 0.75 ppbv h(-1) at 16 degrees N. We find that the modelled gradient is due to a combination of enhanced deposition to vegetation, which decreases the ozone levels by up to 11 pbbv, and the aforementioned enhanced photochemical production north of 12 degrees N. The peroxy radicals required for this enhanced production in the north come from the oxidation of background CO and CH4 as well as from VOCs. Sensitivity studies reveal that both the background CH4 and partially oxidised VOCs, produced from the oxidation of isoprene emitted from the vegetation in the south, contribute around 5-6 ppbv to the ozone gradient. These results suggest that the northward transport of trace gases by the monsoon flux, especially during nighttime, can have a significant, though secondary, role in determining the ozone gradient in the boundary layer. Convection, anthropogenic emissions and NO produced from lightning do not contribute to the establishment of the discussed ozone gradient.

Exaggerated postprandial lipaemia and lower post-heparin lipoprotein lipase activity in middle-aged men

An exaggerated postprandial lipaemic response is thought to play a central role in the development of an atherogenic lipoprotein phenotype, a recognized lipid risk factor for coronary heart disease. A small number of limited studies have compared postprandial lipaemia in subjects of varying age, but have not investigated mechanisms underlying age-associated changes in postprandial lipaemia. In order to test the hypothesis that impaired lipaemia in older subjects is associated with loss of insulin sensitivity, the present study compared the postprandial lipaemic and hormone responses for 9 h following a standard mixed meal in normolipidaemic healthy young and middle-aged men. Lipoprotein lipase (LPL) and hepatic lipase (HL) activities were determined in post-heparin plasma 9 h postprandially and on another occasion under fasting conditions. Postprandial plasma glucose (P < 0.02), retinyl ester (indirect marker for chylomicron particles; P < 0.005) and triacylglycerol (TAG)-rich lipoprotein (density < 1.006 g/ml fraction of plasma) TAG (P < 0.05) and retinyl ester (P < 0.005) responses were higher in middle-aged men, whereas plasma insulin responses were lower in this group (P < 0.001). Fasting and 9 h postprandial LPL and HL activities were also significantly lower in the middle-aged men compared with the young men (P < 0.006). In conclusion, the higher incremental postprandial TAG response in middle-aged men than young men was attributed to the accumulation of dietary-derived TAG-rich lipoproteins (density < 1.006 g/ml fraction of plasma) and occurred in the absence of marked differences in fasting TAG levels between the two groups. Fasting and postprandial LPL and HL activities were markedly lower in middle-aged men, but lack of statistical associations between measures of insulin response and post-heparin lipase activities, as well as between insulin and measures of postprandial lipaemia, suggest that this lower activity cannot be attributed to lack of sensitivity of lipases to activation by insulin. Alternatively, post-heparin lipase activities may not be good markers for the insulin-sensitive component of lipase that is activated postprandially.

A lower bound on the size of k-neighborhood in generalized cubes

The determination of the minimum size of a k-neighborhood (i.e., a neighborhood of a set of k nodes) in a given graph is essential in the analysis of diagnosability and fault tolerance of multicomputer systems. The generalized cubes include the hypercube and most hypercube variants as special cases. In this paper, we present a lower bound on the size of a k-neighborhood in n-dimensional generalized cubes, where 2n + 1 <= k <= 3n - 2. This lower bound is tight in that it is met by the n-dimensional hypercube. Our result is an extension of two previously known results. (c) 2005 Elsevier Inc. All rights reserved.