Feo - Transport of ferrous iron into bacteria

Bacteria commonly utilise a unique type of transporter, called Feo, to specifically acquire the ferrous (Fe2+) form of iron from their environment. Enterobacterial Feo systems are composed of three proteins: FeoA, a small, soluble SH3-domain protein probably located in the cytosol; FeoB, a large protein with a cytosolic N-terminal G-protein domain and a C-terminal integral inner-membrane domain containing two 'Gate' motifs which likely functions as the Fe2+ permease; and FeoC, a small protein apparently functioning as an [Fe-S]-dependent transcriptional repressor. We provide a review of the current literature combined with a bioinformatic assessment of bacterial Feo systems showing how they exhibit common features, as well as differences in organisation and composition which probably reflect variations in mechanisms employed and function.

The regulation of sweet cherry fruit abscission by polar auxin transport

Inconsistency of cropping is an important problem for UK sweet cherry production. Premature fruit abscission in Prunus can reduce yields severely, however, the environmental cues and hormonal signals that trigger abscission have not been identified. Auxin (IAA) is known to delay abscission by reducing the sensitivity of cells in the abscission zone to ethylene, a promoter of abscission. Therefore, the capacity for polar auxin transport (PAT) through sweet cherry pedicels was examined in relation to fruit abscission. Cherry ‘spurs’ (short shoots) with similar leaf areas and different fruit numbers were phloem-girdled to restrict assimilate movement. Abscission from spurs with many fruit (eight or more) occurred within 14 days of girdling, whereas abscission from spurs with few (two) fruit was minimal. The pedicels’ capacity for PAT in spurs with different fruit numbers was determined 1, 3 and 9 days after girdling (DAG). Fruit were analysed for endogenous IAA concentration 3, 5, 7 and 9 DAG. PAT inhibitors 2,3,5-triiodobenzoic acid or 1-N-naphthylphtalamic acid were applied to pedicels of fruit not expected to abscise, i.e. on spurs with few fruit. The effect of these inhibitors on fruit abscission was determined 14 DAG. The proportion of the transported [3H]-IAA was lower from the outset in pedicels from spurs with many fruit. By 9 DAG, symptoms of fruit abscission were apparent and 40% less [3H] -IAA was transported through pedicels on spurs with many fruit. Fruit endogenous IAA concentrations were similar in the two groups of spurs. Application of PAT inhibitors shortly after girdling increased fruit abscission by 30%. The results suggest that although a decline in PAT is not the only cause of fruit abscission, the maintenance of PAT contributes to fruit retention.

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.

Influence of gut morphology on passive transport of freshwater bryozoans by waterfowl in Donana (southwestern Spain)

Waterbirds have been proposed as important vectors for the passive dispersal of those aquatic invertebrates and plants that lack a capacity for active dispersal between isolated water bodies. We analysed the frequency of internal transport of bryozoan propagules (statoblasts) by waterbirds in Donana, Spain, by examining their presence in the intestines and ceca of dead birds and analysing the role of different aspects of gut characteristics in explaining variation in the presence/absence and abundance of statoblasts. Of the 228 samples examined, 7.9% presented intact statoblasts of Plumatella fungosa (Pallas, 1768), Plumatella emarginata Allman, 1844, and two unidentified Plumatella species. For a given bird species, individuals with heavier gizzards and shorter ceca had a lower incidence and abundance of statoblasts in the lower gut. Grit mass and intestine length were unrelated to the presence or abundance of statoblasts. Our results suggest that waterbirds frequently transport bryozoans on a local scale, with lighter gizzards and longer ceca favouring such transport. Lighter gizzards are likely to destroy fewer propagules before they reach the lower gut. Species and individuals with longer ceca are particularly good candidates for long-distance dispersal of bryozoans, given the longer passage time of propagules that enter the ceca.

Efficient and cost-effective experimental determination of kinetic constants and data: the success of a Bayesian systematic approach to drug transport, receptor binding, continuous culture and cell transport kinetics

Details about the parameters of kinetic systems are crucial for progress in both medical and industrial research, including drug development, clinical diagnosis and biotechnology applications. Such details must be collected by a series of kinetic experiments and investigations. The correct design of the experiment is essential to collecting data suitable for analysis, modelling and deriving the correct information. We have developed a systematic and iterative Bayesian method and sets of rules for the design of enzyme kinetic experiments. Our method selects the optimum design to collect data suitable for accurate modelling and analysis and minimises the error in the parameters estimated. The rules select features of the design such as the substrate range and the number of measurements. We show here that this method can be directly applied to the study of other important kinetic systems, including drug transport, receptor binding, microbial culture and cell transport kinetics. It is possible to reduce the errors in the estimated parameters and, most importantly, increase the efficiency and cost-effectiveness by reducing the necessary amount of experiments and data points measured. (C) 2003 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

A novel method for the transport and analysis of genetic material from polyps and zooxanthellae of scleractinian corals

We have developed a new simple method for transport, storage, and analysis of genetic material from the corals Agaricia agaricites, Dendrogyra cylindrica, Eusmilia ancora, Meandrina meandrites, Montastrea annularis, Porites astreoides, Porites furcata, Porites porites, and Siderastrea siderea at room temperature. All species yielded sufficient DNA from a single FTA(R) card (19 mug-43 ng) for subsequent PCR amplification of both coral and zooxanthellar DNA. The D1 and D2 variable region of the large Subunit rRNA gene (LSUrDNA) was amplified from the DNA of P. furcata and S. siderea by PCR. Electrophoresis yielded two major DNA bands: an 800-base pair (bp) DNA, which represented the coral ribosomal RNA (rRNA) gene, and a 600-bp DNA, which represented the zooxanthellar srRNA gene. Extraction of DNA from the bands yielded between 290 mug total DNA (S. siderea coral DNA) and 9 mug total DNA (P. furcata zooxanthellar DNA). The ability to transport and store genetic material from scleractinian corals without resort to laboratory facilities in the field allows for the molecular Study of a far wider range and variety of coral sites than have been studied to date. (C) 2003 Elsevier Science B.V. All rights reserved.

Identification of stimulatory and inhibitory inputs to the hypothalamic-pituitary-adrenal axis during hypoglycaemia or transport in ewes

This study used the novel approach of statistical modelling to investigate the control of hypothalamic-pituitary-adrenal (HPA) axis and quantify temporal relationships between hormones. Two experimental paradigms were chosen, insulin-induced hypoglycaemia and 2 h transport, to assess differences in control between noncognitive and cognitive stimuli. Vasopressin and corticotropin-releasing hormone (CRH) were measured in hypophysial portal plasma, and adrenocorticotropin hormone (ACTH) and cortisol in jugular plasma of conscious sheep, and deconvolution analysis was used to calculate secretory rates, before modelling. During hypoglycaemia, the relationship between plasma glucose and vasopressin or CRH was best described by log(10) transforming variables (i.e. a positive power-curve relationship). A negative-feedback relationship with log(10) cortisol concentration 2 h previously was detected. Analysis of the 'transport' stimulus suggested that the strength of the perceived stimulus decreased over time after accounting for cortisol facilitation and negative-feedback. The time course of vasopressin and CRH responses to each stimulus were different However, at the pituitary level, the data suggested that log(10) ACTH secretion rate was related to log(10) vasopressin and CRH concentrations with very similar regression coefficients and an identical ratio of actions (2.3 : 1) for both stimuli. Similar magnitude negative-feedback effects of log(10) cortisol at -110 min (hypoglycaemia) or -40 min (transport) were detected, and both models contained a stimulatory relationship with cortisol at 0 min (facilitation). At adrenal gland level, cortisol secretory rates were related to simultaneously measured untransformed ACTH concentration but the regression coefficient for the hypoglycaemia model was 2.5-fold greater than for transport. No individual sustained maximum cortisol secretion for longer than 20 min during hypoglycaemia and 40 min during transport. These unique models demonstrate that corticosteroid negative-feedback is a significant control mechanism at both the pituitary and hypothalamus. The amplitude of HPA response may be related to stimulus intensity and corticosteroid negative-feedback, while duration depended on feedback alone.

Condensation and moisture transport in cold roofs: effect of roof underlay

Cold pitched roofs, with their form of construction situating insulation on a horizontal ceiling, are intrinsically vulnerable to condensation. This study reports the results derived from using a simulation package (Heat, Air and Moisture modelling tool, or HAM-Tools) to investigate the risk of condensation in cold pitched roofs in housing fitted with a vapour-permeable underlay (VPU) of known characteristics. In order to visualize the effect of the VPUs on moisture transfer, several scenarios were modelled, and compared with the results from a conventional bituminous felt with high resistance (200 MNs/g, Sd = 40 m). The results indicate that ventilation is essential in the roof to reduce condensation. However, a sensitivity analysis proved that reducing the overall tightness of the ceiling and using lower-resistance VPUs would help in controlling condensation formation in the roof. To a large extent, the proposed characteristic performance of the VPU as predicted by manufacturers and some researchers may only be realistic if gaps in the ceiling are sealed completely during construction, which may be practically difficult given current construction practice.

Inhibition of cellular proliferation by the genistein metabolite 5,7,3',4'-tetrahydroxyisoflavone is mediated by DNA damage and activation of the ATR signalling pathway

The cellular actions of genistein, and its in vivo metabolites, are believed to mediate the decreased risk of breast cancer associated with high soy consumption. The genistein metabolite, 5,7,3',4'-tetrahydroxyisoflavone (THIF), induced G2-M cell cycle arrest in T47D tumorigenic breast epithelial cells via a mechanism involving the activation of ataxia telangiectasia and Rad3-related kinase (ATR) via its phosphorylation at Ser(428). This activation of ATR appeared to result from THIF-induced increases in intracellular oxidative stress, a depletion of cellular GSH and an increase in DNA strand breakage. THIF treatment also led to an inhibition of cdc2, which was accompanied by the phosphorylation of both p53 (Ser(15)) and Chk1 (Ser(296)) and the de-activation of cdc25C phosphatase. We suggest the anti-proliferative actions of THIF may be mediated by initial oxidative DNA damage, activation of ATR and downstream regulation of the p53 and Chk1 pathways leading to cell cycle arrest in G2-M. This may represent one mechanism by which genistein exerts its cellular activity in vivo. (c) 2007 Elsevier Inc. All rights reserved.