Valors típics de pH i DP del suport de tela en la pintura de cavallet

Ja fa varies decades que els conservadors-restauradors de paper van comenc;ar a tenir en compteel pH de les obres que tractaven, ja que es va veure que I'acidesa incidia molt directament en comde rapid I'objecte es debilitava mecimicament. De fet, trobem tant aviat com el 1936, una patenten registrada per OJ. Schierholtz per desacidificar el paper d'empaperar parets (Porck, 1996).La tela d'un quadre, essent un teixit fet a base de fibres vegetals compastes majoritariament perceHulosa, com les fibres del paper, és lógicament també facilment degradable si I'ambient ñes acid(te un baix pH).Sorprenentment, pero, I'acidesa de la tela deis quadres, tot i que en ocasions puntuals ha estatanalitzada (Bajocchi, 2009; Young, 1999), encara no és un parametre que es miri de forma rutinariai per tant, fins recentment, no se sabia quins eren els valors de pH més típics que pot tenir unquadre.Aquest estudi és una primera recopilació sistematica d'aquest t ipus d' in formació per a partir d'aquícrear un banc de dades que vagi recollint aquest t ipus d'informació sobre el majar nombre possiblede quadres.Si I'acidesa present en la tela ens indica com de rapid es degradara aquesta en el futur, la mesura delgrau de polimerització de la tela (DP), ens indica si la tela té una al ta o baixa resistencia mecanica enel moment actual. Així doncs, aquests dos parametres ens aporten informació molt úti l sobre I'estatde conserva ció del suportoAquesta recerca pretén respondre a les preguntes de quins són els valors de pH i DP que típicamentpodem trabar en la tela deis quadres, així com analitzar la relació entre aquests dos parametres i també la relació entre la data de producció deis quadres i els valors de pH i DP.

Valors típics de pH i DP del suport de tela en la pintura de cavallet

Ja fa varies decades que els conservadors-restauradors de paper van comenc;ar a tenir en compteel pH de les obres que tractaven, ja que es va veure que I'acidesa incidia molt directament en comde rapid I'objecte es debilitava mecimicament. De fet, trobem tant aviat com el 1936, una patenten registrada per OJ. Schierholtz per desacidificar el paper d'empaperar parets (Porck, 1996).La tela d'un quadre, essent un teixit fet a base de fibres vegetals compastes majoritariament perceHulosa, com les fibres del paper, és lógicament també facilment degradable si I'ambient ñes acid(te un baix pH).Sorprenentment, pero, I'acidesa de la tela deis quadres, tot i que en ocasions puntuals ha estatanalitzada (Bajocchi, 2009; Young, 1999), encara no és un parametre que es miri de forma rutinariai per tant, fins recentment, no se sabia quins eren els valors de pH més típics que pot tenir unquadre.Aquest estudi és una primera recopilació sistematica d'aquest t ipus d' in formació per a partir d'aquícrear un banc de dades que vagi recollint aquest t ipus d'informació sobre el majar nombre possiblede quadres.Si I'acidesa present en la tela ens indica com de rapid es degradara aquesta en el futur, la mesura delgrau de polimerització de la tela (DP), ens indica si la tela té una al ta o baixa resistencia mecanica enel moment actual. Així doncs, aquests dos parametres ens aporten informació molt úti l sobre I'estatde conserva ció del suportoAquesta recerca pretén respondre a les preguntes de quins són els valors de pH i DP que típicamentpodem trabar en la tela deis quadres, així com analitzar la relació entre aquests dos parametres i també la relació entre la data de producció deis quadres i els valors de pH i DP.

Determinacion de la configuracion E-Z de los acidos Fumarico y Maleico. Un experimento orientado a incentivar el desarrollo de la investigacion cientifica en alumnos de Pregrado

In this work we intend to eliminate the idea that laboratory exercises seem like cookbooks. That is, exercises shall be presented as a problematic situation. Based on observation and experimentation, the students should determine the E-Z configuration of maleic and fumaric acids. The basis of this laboratory exercise is the acid-catalyzed isomerization of maleic acid to fumaric acid. Students are given the starting material, reagents and the experimental procedure. They are told that the starting material is a dicarboxylic acid containing a C=C double bond of formula C4H4O4. Students determine melting points, solubilities, acidity and chromatographic patterns for both the starting material and the product, so that a configuration of each acid can be proposed. This type of experiment yields excellent results, because the students are left to deduce that maleic acid is less stable than fumaric acid. Additionally, they conclude that maleic acid is the "Z" isomer and fumaric acid is the "E" isomer. Finally, this laboratory exercise allows the students to develop simultaneously their critical-thinking skills with the respective laboratory techniques and not to see chemistry as recipes to be followed.

Evaluación de la reactividad de sulfuros de hierro y residuos mineros: una metodología basada en la aplicación de la voltamperometría cíclica

The mining industry around the world produces an important amount of wastes, which by their high toxic metal and iron sulfide content present a serious environmental problem. Iron sulfide oxidation under weathering conditions provokes the main environmental problem of the mining industry, the generation of Acid Rock Drainage (ARD). Up to now the prediction methodologies do not allow the study of important factors that influence the generation of ARD, producing in some cases erroneous or uncertain conclusions. This paper shows the utilization of cyclic voltammetry using carbon paste electrodes (CPE-Mineral) as an alternative tool in the study of the oxidation capacity of iron sulfides and mining wastes. This electrochemical technique constitutes a novel methodology to establish and understand the factors involved during generation of ARD. Results of several studies including selected sulfide samples and sulfide mining wastes have been described in order to show the capacity of this methodology as a complementary tool in the prediction of the generation of ARD.

Effect of reducing and replacing pork fat on the physicochemical, instrumental and sensory characteristics throughout storage time of small caliber non-acid fermented sausages with reduced sodium content

The effect of pork fat reduction (from 44% to 20% final fat content) and its partial substitution by sunflower oil (3% addition) on the physicochemical, instrumental and sensory properties throughout storage time of small caliber non-acid fermented sausages (fuet type) with reduced sodium content (with partial substitution of NaCl by KCl and K-lactate) and without direct addition of nitrate and nitrite (natural nitrate source used instead), was studied. Results showed that sausages with reduced fat (10% initial fat content) and with acceptable sensory characteristics can be obtained by adding to the shoulder lean (8% fat content) during the grinding, either 3.3% backfat (3% fat content) or 3% sunflower oil, both previously finely comminuted with lean. Furthermore, sunflower oil showed to be suitable for partial pork backfat substitution in very lean fermented sausages, conferring desirable sensory properties similar to those of sausages with standard fat content. The sensory quality of the sausages was maintained after three-month cold storage in modified atmosphere.

Estudio teórico de la isomerización del ácido maleico en ácido fumárico: un enfoque basado en el concepto de superficie de energía potencial

A comparative study based on potential energy surfaces (PES) of 2-butanedioic and hypothetic 2-butanedioic/HCl acids is useful for understanding the maleic acid isomerization. The PES enables locating conformers of minimum energy, intermediates of reactions and transition states. From contour diagrams, a set of possible reaction paths are depicted interconnecting the proposed structures. The study was carried out in absentia and in the presence of the catalyst (HCl), using an solvatation model provided by the Gaussian software package. Clearly, the effect of HCl is given by new reaction paths with lower energetic barriers in relation to the reaction without catalyzing.

Registrador portátil de odorantes basado en la modulación de temperatura de un sensor mos comercial

A simple, portable and low-cost system for odor detection was developed using a single MOS commercial sensor and a microcontroller. The temperature modulation technique was implemented applying a DC signal pulse to the sensor heater by a bipolar transistor. Two odorant profiles, ethanol and acetic acid vapors, were obtained and distinguished based on their amplitude versus time responses. Response for acetic acid was not reported by the sensor manufacturer. An ethanol vapor calibration curve was also obtained. Experimental data showed a potential behavior according to the theoretical equation of the MOS sensors. Values of logK=0.457 and α=-0.213 for a 95% confidence level were obtained.

Actividad insecticida sobre Spodoptera frugiperda (Lepidóptera: Noctuidae) de los compuestos aislados de la parte aérea de Piper septuplinervium (Miq.) c. dc. y las inflorescencias de Piper subtomentosum Trel. & Yunck. (Piperaceae)

The bioassay-guided purification of ethanolic extracts from inflorescences of Piper subtomentosum Trel. & Yunck and aerial part of Piper septuplinervium (Miq. ) C. DC. led to isolation of five flavonoids, uvangoletin (1), galangin (2), chrysin (5), 5-hydroxy-4',7-dimethoxy-flavone (6), pinostrobin (7); one amide, N-p-coumaroil-tyramine (4); one acylglycerol, monopalmitin (3); one derivative of acid, protocatechuic acid (8); and glycosydated sterol, daucosterol (9). Their structures were elucidated on the basis of spectroscopy and spectrometry data and by comparison with data reported in the literature. The isolated compounds were tested against Spodoptera frugiperda. The results showed galangin and protocatechuic acid to be the most active (LC 50 13.63 and 17.16 ppm, respectively).

DERIVATIZACIÓN Y CARACTERIZACIÓN ESPECTROSCÓPICA DE UN BIOPOLÍMERO A BASE DE L -LISINA CON ANÁLOGOS DE LA D-BIOTINA: CO -POLI(L-LISINA)-GRAFT -(ε-N-[X-D -BIOTINIL]-L-LISINA)

We report the single-step derivatization reaction of a biopolymer based onL -lysine with D -biotin analogs:Co -poly(L -lysine)-graft-(ε-N -[X-D-biotinyl]-L -lysine) (PLL-X-Biotin). The valeric acid carboxylate of D -biotin is activated to an NHS ester for direct modification of amine groups in proteins and other macromolecules. NHS esters react by nucleophilic attack of an amine in the carbonyl group, releasing the NHS group, and forming a stable amide linkage. NHS-X-Biotin is the simplest biotinylation reagent commercially available. In contrast withD -biotin, it has a longer spacer arm off the valeric acid side chain allowing better binding potential for avidin or streptavidin probes. Derivatization of poly(L -lysine) (PLL) with NHS-X-Biotin led to a copolymer PLL-X-Biotin. UV-Visible, IR-FT and 1H NMR characteristics derived from synthesis are briefly discussed.

Seeds of species from the ‘caatinga’: proteins, oils and fatty acid contents

The seeds of 14 species from the ‘caatinga’, a dry forest ecosystem of the semiarid region of northeast Brazil, were analysed for total protein and total lipid contents, as well as fatty acid distribution. The seeds of Argemone mexicana L., an introduced and naturalized species in Brazil, commonly found in ‘caatingas’ and other vegetation, were also analysed. The protein contents ranged from 123 g.kg-1 to 551 g.kg-1, higher contents being found in species of Leguminosae, but also in Jatropha mollissima (Pohl) Baill. (Euphorbiaceae, 409 g.kg-1). Oil contents ranged from 10 g.kg-1 to 400 g.kg-1. The contents of protein and oil were found to be inversely proportional in the seeds of most species, the figures for proteins being generally higher than those of oils. Most species presented either oleic or linoleic as predominant fatty acids. Cardiospermum cf. corindum L. presented eicosenoic acid as the predominant fatty acid.

Cholesterol changes the fatty acid composition of rat enterocytes

The effect of free cholesterol on the fatty acid composition and growth of rat fetal enterocytes was investigated in the absence and presence of 10% (v/v) fetal calf serum. Cholesterol caused a significant reduction of cell number after 6 and 12 h in culture. The fatty acid composition of enterocytes cultured in the presence of serum was also changed by the presence of 20 µM cholesterol. The fatty acid profile was determined by HPLC using fluorescence detection (325 nm excitation and 395 nm emission). Cholesterol (20 µM) increased the proportion (given in percentage of the total fatty acids) of the following fatty acids in cultured cells: lauric (by 42%), oleic (by 34%), linoleic (by 44%) and gamma-linolenic (by 20%) acids and reduced the proportion of palmitic (by 12%), stearic (by 20%), arachidonic (by 21%) and docosahexaenoic (by 44%) acids. In addition to modifying the content of individual fatty acids, cholesterol increased the polyunsaturated/saturated fatty acid ratio from 0.48 to 0.67 and the unsaturation index from 67.12 to 75.30. This is the first evidence that cholesterol modifies fatty acid composition possibly via de novo fatty acid synthesis and desaturation.

Effect of bullfrog (Rana catesbeiana) oil administered by gavage on the fatty acid composition and oxidative stress of mouse liver

The aim of the present study was to investigate the effects of daily intragastric administration of bullfrog oil (oleic, linoleic and palmitoleic acid-rich oil), corresponding to 0.4% of body weight for four weeks, on fatty acid composition and oxidative stress (lipid peroxidation and catalase activity) in mouse liver. The activities of aspartate aminotransferase (AST), alkaline phosphatase (ALP), alanine aminotransferase (ALT), and gamma-glutamyltransferase (GGT), biomarkers of tissue injury, were determined in liver homogenates and serum. The proportions of 18:2n-6, 20:4n-6, 20:5n-3, and 22:6n-3 (polyunsaturated fatty acids, from 37 to 60%) in the total fatty acid content were increased in the liver of the bullfrog oil-treated group (P < 0.05) compared to control. At the same time, a significant decrease in the relative abundance of 14:0, 16:0, and 18:0 (saturated fatty acids, from 49 to 25%) was observed. The hepatic content of thiobarbituric acid reactive substances (TBARS) was increased from 2.3 ± 0.2 to 12.3 ± 0.3 nmol TBA-MDA/mg protein and catalase activity was increased from 840 ± 32 to 1110 ± 45 µmol reduced H2O2 min-1 mg protein-1 in the treated group. Bullfrog oil administration increased AST and ALP activities in the liver (from 234.10 ± 0.12 to 342.84 ± 0.13 and 9.38 ± 0.60 to 20.06 ± 0.27 U/g, respectively) and in serum (from 95.41 ± 6.13 to 120.32 ± 3.15 and 234.75 ± 11.5 to 254.41 ± 2.73 U/l, respectively), suggesting that this treatment induced tissue damage. ALT activity was increased from 287.28 ± 0.29 to 315.98 ± 0.34 U/g in the liver but remained unchanged in serum, whereas the GGT activity was not affected by bullfrog oil treatment. Therefore, despite the interesting modulation of fatty acids by bullfrog oil, a possible therapeutic use requires care since some adverse effects were observed in liver.

Investigations on the production of long chain fatty acids in Choanephora cucurbitarum (Berk.

The fatty acid composition of the total cellular lipids of Choanephora cucurbitarum incubated for 96 hrs on either glucose-ammonium sulfate or malt-weast extract media was determined. The major fatty acids were palmitic, palmitoleic, stearic and linoleic acids. The saturated fatty acid possessing the longest acyl chain was stearate (C 18:0). The presence of glutamic acid (2.0 x 10-1% or 1.36 x la-2M) in either of the above growth media resulted in increase in percent of 1f-linolenic acid, decrease in percent of linoleic ~iCid and appearance of a new series of fatty acid> C ~8 e.g. C ",,,,'V' C2k:O, C26,O. The addition of glutamic acid had no effect on the lipid yield but slightly decreased the degree of unsaturation. Compounds which duplicated the effect of glutamic acid were acetate, malate, citrate, succinate, 0( -ketoglutarate, prOline, -y -aminobutyric acid and glucose (3%) but not aspartic acid or alanine. ~o correlation was found between glutamic acid pool concentration and the presence in the growth medium of those compounds which stimulate long chain fatty acid production. Four hours of incubation with 27 JJ 1-1 glutamate supported the production of long chain fatty acids. This stimulation is inhibited if 272 .u M isophthalic acid is added with 27 AJ M glutamate. But, long chain fatty acids were detected when 27 JJ M eX -ketoglutarate is also present in the incubation mixture. Five hours of incubation with 100 ,Mg/ml of cycloheximide resulted in over 9CY/o inhibition of cytoplasmic :protein synthesise Glutamate (27 .uM) enhanced the synthesis of long chain fatty acids under these conditions. These findings are discussed in an attempt to provide a plausible explanation COmmon to compounds that support the production of long chain fatty acids.

Évaluation de l’utilité des technologies destinées à l’évaluation de la résistance physiologique aux antiplaquettaires en laboratoire.

Introduction : L’effet biologique variable de l’aspirine a été attribué à un état de résistance pharmacologique. L’incidence de cette « résistance » varie selon la population ou la technologie étudiée. Méthodes : Nous avons déterminé la performance de 5 techniques évaluant l’effet de l’aspirine chez des sujets sains, non fumeurs et ne prenant aucune médication pouvant interférer avec la fonction plaquettaire. Des spécimens de sang et d’urine ont été obtenus avant et après 8-10 jours de prise de 80 mg d’aspirine. Résultats: Chez 45 sujets de 19-59 ans, la sensibilité (SE), la spécificité (SP), et la valeur optimale de coupure (CO) pour détecter l’effet de l’aspirine sont : agrégométrie par transmission optique induite avec 1,6 mM d’acide arachidonique (ATO-AA) - SE 100%, SP 95,9%, CO 20%; ATO-ADP 10 μM - SE 84,4%, SP 77,7%, CO 70%; VerifyNow® Aspirin - SE 100%, SP 95,6%, CO 550 ARU; agrégation en tube - SE 82,2%, SP 86,7%, CO 55%; TEG® - SE 82,9%, SP 75,8%, CO 90%; et le dosage de 11-dehydrothromboxane B2 urinaire - SE 62,2%, SP 82,2%, CO 60 pg/ml. Conclusions: La résistance à l’aspirine chez les sujets sains définie par ATO-AA et VerifyNow® Aspirin est rare. Puisque les autres techniques étudiées discriminent de façon sous optimale l’effet de l’aspirine, leur utilité dans la définition de la résistance pharmacologique à l’aspirine semble marginale. Ces résultats suggèrent qu’une proportion de la variabilité de l’incidence rapportée de “résistance à l’aspirine” est artefactuelle et reliée aux limitations technologiques de certaines analyses.

Caractérisation de la voie de signalisation AMPK/ACC dans le foie et l’intestin du Psammomys obesus, un modèle animal de résistance à l’insuline et de diabète de type 2

L’expansion des maladies métaboliques dans les sociétés modernes exige plus d’activités de recherche afin d’augmenter notre compréhension des mécanismes et l’identification de nouvelles cibles d’interventions cliniques. L’obésité, la résistance à l’insuline (RI) et la dyslipidémie, en particulier sont tous des facteurs de risque associés à la pathogenèse du diabète de type 2 (DT2) et des maladies cardiovasculaires. Ainsi, la dyslipidémie postprandiale, notamment la surproduction des lipoprotéines hépatiques et intestinales, contribue d’une façon significative à l’hypertriglycéridémie. Quoique plusieurs études cliniques et fondamentales chez l’homme et les modèles animaux aient mis en évidence les rôles importants joués par le foie et l’intestin dans la dyslipidémie, les mécanismes moléculaires en cause ne sont pas bien élucidés. L’une des voies principales régulant le métabolisme lipidique est la voie de la protéine kinase AMPK. L’épuisement de l’ATP intracellulaire entraîne une activation de l’AMPK qui va œuvrer pour rétablir l’équilibre énergétique en stimulant des voies génératrices d’ATP et en inhibant des voies anaboliques consommatrices d’ATP. Les effets positifs de l’activation de l’AMPK comprennent l’augmentation de la sensibilité à l’insuline dans les tissus périphériques, la réduction de l’hyperglycémie et la réduction de la lipogenèse, d’où son importance dans les interventions cliniques pour la correction des dérangements métaboliques. Il est à souligner que le rôle de l’AMPK dans le foie et l’intestin semble plus complexe et mal compris. Ainsi, la voie de signalisation de l’AMPK n’est pas bien élucidée dans les situations pathologiques telles que le DT2, la RI et l’obésité. Dans le présent projet, notre objectif consiste à caractériser le rôle de cette voie de signalisation dans la lipogenèse hépatique et dans le métabolisme des lipides dans l’intestin chez le Psammomys obesus, un modèle animal d’obésité, de RI et de DT2. À cette fin, 3 groupes d’animaux sont étudiés (i.e. contrôle, RI et DT2). En caractérisant la voie de signalisation de l’AMPK/ACC dans le foie, nous avons constaté une augmentation de l’expression génique des enzymes clés de la lipogenèse (ACC, FAS, SCD-1 et mGPAT) et des facteurs de transcription (ChREBP, SREBP-1) qui modulent leur niveau d’expression. Nos analyses détaillées ont révélé, par la suite, une nette augmentation de l’expression de l’isoforme cytosolique de l’ACC, ACC1 (impliqué dans la lipogenèse de novo) concomitante avec une invariabilité de l’expression de l’isoforme mitochondrial ACC2 (impliqué dans la régulation négative de la β-oxydation). En dépit d’un état adaptatif caractérisé par une expression protéique et une phosphorylation (activation) élevées de l’AMPKα, l’activité de la kinase qui phosphoryle et inhibe l’ACC reste très élevée chez les animaux RI et DT2. Au niveau de l’intestin grêle des animaux RI et DT2, nous avons démontré que l’augmentation de la lipogenèse intestinale est principalement associée avec une diminution de la voie de signalisation de l’AMPK (i.e. expression protéique et phosphorylation/activation réduites des deux isoformes AMPKα1 et AMPKα2). La principale conséquence de la diminution de l’activité AMPK est la réduction de la phosphorylation de l’ACC. Étant donné que le niveau d’expression totale d’ACC reste inchangé, nos résultats suggèrent donc une augmentation de l’activité des deux isoformes ACC1 et ACC2. En parallèle, nous avons observé une réduction de l’expression protéique et génique de la CPT1 [enzyme clé de la β-oxydation des acides gras (AG)]. L’ensemble de ces résultats suggère une inhibition de l’oxydation des AG concomitante avec une stimulation de la lipogenèse de novo. Enfin, nous avons démontré que l’intestin grêle est un organe sensible à l’action de l’insuline et que le développement de la résistance à l’insuline pourrait altérer les deux voies de signalisation (i.e. Akt/GSK3 et p38MAPK) essentielles dans plusieurs processus métaboliques. En conclusion, nos résultats indiquent que l’augmentation de la lipogenèse qui contribue pour une grande partie à la dyslipidémie dans la résistance à l’insuline et le diabète serait due, en partie, à des défauts de signalisation par l’AMPK. Nos observations illustrent donc le rôle crucial du système AMPK au niveau hépatique et intestinal, ce qui valide l’approche thérapeutique consistant à activer l’AMPK pour traiter les maladies métaboliques.