http://hdl.handle.net/10451/3511 Thu, 20 Jun 2013 01:53:05 GMT 2013-06-20T01:53:05Z http://hdl.handle.net/10451/8522 Title: Screening of the inhibitory effect of xenobiotics on alcohol metabolism using S9 rat liver fractions Authors: Dias, Catarina; Testa, Bernard; Soveral, Graça; Dias, Mário; Constantino, Luís Abstract: The purpose of this work was to develop and optimize a simple and suitable method to detect the potential inhibitory effect of drugs and medicines on alcohol dehydrogenase (ADH) activity in order to evaluate the possible interactions between medicines and alcohol metabolism. Commonly used medicines that are often involved in court litigations related with driving under the influence of alcohol were selected. Alprazolam, flunitrazepam and tramadol were tested as drugs with no known effect on ADH activity. Cimetidine, reported previously as having inhibitory effect on ADH, and 4-methylpyrazole (4-MP), a well known ADH inhibitor, were tested as positive controls. Apart from 4-MP, tramadol was identified as having the higher inhibitory effect with an IC50 of 44.7 x 10-3 mM, followed by cimetidine (IC50 of 122.9 x 10-3 mM). Alprazolam and flunitrazepam also reduced liver ADH activity but to a smaller extent (inhibition of 11.8 ± 5.0% for alprazolam 1.0 mM and 34.5 ± 7.1% for flunitrazepam 0.04 mM). Apart from cimetidine, this is the first report describing the inhibitory effect of these drugs on ethanol metabolism. The results also show the suitability of the method to screen for inhibitory effect of drugs on ethanol metabolism helping to identify drugs for which further study is justified. Sun, 01 Jan 2012 00:00:00 GMT http://hdl.handle.net/10451/8522 2012-01-01T00:00:00Z http://hdl.handle.net/10451/8039 Title: Conjugated linoleic acid reduces permeability and fluidity of adipose plasma membranes from obese Zucker rats Authors: Martins, Ana Paula; Lopes, Paula A.; Martins, Susana V.; Madeira, Ana; Santos, Nuno C.; Prates, José A. M.; Moura, Teresa F.; Soveral, Graça Abstract: Conjugated linoleic acid (CLA) is a dietary fatty acid frequently used as a body fat reducing agent whose effects upon cell membranes and cellular function remain unknown. Obese Zucker rats were fed atherogenic diets containing saturated fats of vegetable or animal origin with or without 1% CLA, as a mixture of cis(c)9,trans(t)11 and t10,c12 isomers. Plasma membrane vesicles obtained from visceral adi- pose tissue were used to assess the effectiveness of dietary fat and CLA membrane incorporation and its outcome on fluidity and permeability to water and glycerol. A significant decrease in adipose membrane fluidity was correlated with the changes observed in permeability, which seem to be caused by the incor- poration of the t10,c12 CLA isomer into membrane phospholipids. These results indicate that CLA supple- mentation in obese Zucker rats fed saturated and cholesterol rich diets reduces the fluidity and permeability of adipose membranes, therefore not supporting CLA as a body fat reducing agent through membrane fluidification in obese fat consumers. Description: NOTICE: this is the author’s version of a work that was accepted for publication in Biochemical and Biophysical Research Communications. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Biochemical and Biophysical Research Communications. July 2010; 398 (2): 199-204. Fri, 01 Jan 2010 00:00:00 GMT http://hdl.handle.net/10451/8039 2010-01-01T00:00:00Z http://hdl.handle.net/10451/8038 Title: Effect of dietary conjugated linoleic acid isomers on water and glycerol permeability of kidney membranes Authors: Soveral, Graça; Martins, Ana Paula; Martins, Susana V.; Lopes, Paula A.; Alfaia, Cristina M.; Prates, José A. M.; Moura, Teresa F. Abstract: Conjugated linoleic acid (CLA) refers to a group of positional and geometrical isomers of linoleic acid in which the double bonds are conjugated. Dietary CLA has been associated with various health benefits although details of its molecular mode of action remain elusive. The effect of CLA supplemented to palm oil-based diets in Wistar rats, as a mixture of both or isolated c9,t11 and t10,c12 isomers, was examined on water and glycerol membrane permeability of kidney proximal tubule. Although water permeability was unaltered, an increase in glycerol permeability was obtained for the group supplemented with CLA mixture, even though the activation energy for glycerol permeation remained high. This effect was correlated with an increased CLA isomeric membrane incorporation for the same dietary group. These results suggest that diet supplementation with CLA mixture, in contrast to its individual isomers, may enhance membrane fluidity subsequently raising kidney glycerol reabsorption. Description: NOTICE: this is the author’s version of a work that was accepted for publication in Biochemical and Biophysical Research Communications. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Biochemical and Biophysical Research Communications. May 2009; 383(1): 108-112. Thu, 01 Jan 2009 00:00:00 GMT http://hdl.handle.net/10451/8038 2009-01-01T00:00:00Z http://hdl.handle.net/10451/3903 Title: Effect of ethanol on fluxes of water and protons across the plasma membrane of Saccharomyces cerevisiae Authors: Madeira, Ana; Leitão, Luís; Soveral, Graça; Dias, Patrícia; Prista, Catarina; Moura, Teresa; Loureiro-Dias, Maria C. Abstract: Plasma membrane integrity, ability to transport substrates and maintenance of homeostasis represent obligatory requirements for efficient ethanol production by Saccharomyces cerevisiae. The effect of ethanol on water diffusion through the bilayer and on mediated water movements was evaluated by stopped flow spectro- scopy. Ethanol stimulated water diffusion and inhibited mediated water transport. In a strain overexpressing AQY1, the activation energy for water transport increased progressively (from 5.9 to 12.7 kcal mol􏰁1) for increasing ethanol concentrations (up to 12%v/v), indicating that mediated water transport lost importance as compared with water diffusion through the bilayer. The effect of ethanol on proton movements (inward by passive diffusion and outward through the PMA1 H1-ATPase) was evaluated by measuring the rate of extracellular alcalinization and acidification of unbuffered cell suspensions at different tem- peratures. Above 10% ethanol, H1 diffusion was strongly increased at 30 1C, but no effect was observed at 20 1C up to 12%, indicating the existence of a threshold above which ethanol has a marked effect. On H1 extrusion, ethanol had no effect at 20 1C, but induced a monotonous decrease at higher temperatures. Our results support the view that above a threshold of ethanol concentration, the membrane structure is disrupted, becoming very leaky to H1. Description: The definitive version is available at http://onlinelibrary.wiley.com/doi/10.1111/j.1567-1364.2010.00607.x/pdf. A versão definitiva está disponível em http://onlinelibrary.wiley.com/doi/10.1111/j.1567-1364.2010.00607.x/pdf Fri, 01 Jan 2010 00:00:00 GMT http://hdl.handle.net/10451/3903 2010-01-01T00:00:00Z