PI3K/Akt inhibition modulates multidrug resistance and activates NF-κB in murine lymphoma cell lines García, Mariana Gabriela; Alaniz, Laura Daniela; Cordo Russo, Rosalia Ines; Alvarez, Elida Ester; Hajos, Silvia Elvira Upregulation of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway has been described in some tumors related to multidrug resistance (MDR). The aim of this work was to analyze the relationship between PI3K/Akt, MDR and NF-kappaB in murine lymphoma cell lines resistant to vincristine (LBR-V160) and doxorubicin (LBR-D160) as well as in the sensitive line (LBR-). PI3K/Akt activity, analyzed by phosphatidylinositol trisphosphate production and phosphorylated Akt (p-Akt) expression, was higher in the resistant cell lines than in the sensitive one and inhibition with wortmannin or LY294002 improved apoptosis in the resistant cell lines. Vincristine but not doxorubicin increased p-Akt expression whereas co-treatment with PI3K inhibitors and vincristine increased apoptosis in the three cell lines. Wortmannin and LY294002 inhibited P-glycoprotein (Pgp) function and also increased NF-kappaB activity. We concluded that the PI3K/Akt pathway is involved in MDR in lymphoma cell lines and PI3K/Akt inhibition correlates down-regulation of NF-kappaB activity and inhibition Pgp function.

Carbon steel passivity examined in alkaline solutions: the effect of chloride and nitrite ions Valcarce, María Beatriz; Vazquez, Marcela Vivian The effect of chloride and nitrite ions on the passivity of steel in alkaline solutions was investigated. Four nitrite dosages were tested, resulting in various nitrite/chloride ratios. The behavior of steel was evaluated on electrodes aged during 1 and 90 days, measuring electrochemical parameters such as the corrosion, pitting and repassivation potentials, the corrosion current density, the weight loss and performing electrochemical impedance spectra. The presence of 0.8 mol l-1 of chloride induced pitting only under polarization and when the chloride/hydroxyl ratio was not less than one. Nitrite ions behave as effective inhibitors of pit propagation for all the concentrations tested (0.2-0.8 mol l-1). A nitrite/chloride ratio of 0.25 induces complete surface repassivation. Nevertheless, at open circuit potential, the high alkalinity guarantees passivation even in the presence of chlorides. In the event that the passive layer is damaged and pitting can be initiated, nitrite ions are effective in inhibiting pit propagation. © 2008 Elsevier Ltd. All rights reserved.

An anilioid snake from the Upper Cretaceous of northern Patagonia Gomez, Raul Orencio; Baez, Ana Maria; Rougier, Guillermo W. We report the first record of anilioids from southern South America, a region where they do not live today. The fossils come from the Allen Formation (Late Campanian Early Maastrichtian) at Bajo Trapalcó and Bajo de Santa Rosa localities, Río Negro province, Argentina. The remains consist of several vertebrae, most of which belong to the mid posterior precloacal region of the column. Comparisons to other extant and extinct anilioid taxa indicate that these remains represent a new taxon, Australophis anilioides gen. et sp. nov. Australophis is morphologically closer to Palaeocene Hoffstetterella from Brazil and extant South American Anilius than to any other snake. These taxa might be closely related, in which case they would represent a lineage distinct from that including Cylindrophis and uropeltids. The two lineages must have diverged by the Late Cretaceous.

Entomofauna asociada al molle (Schinus areira L.) en la Quebrada de Humahuaca, Jujuy, Argentina; Entomofauna associated to the Peppertree (Schinus areira L.) in Quebrada de Humahuaca, Jujuy, Argentina Neder, Lilia Estela; Zamar, María Inés; Ortiz, Felix; Montero, Teresa Eleonor; Linares, Mario Alfredo; Hamity, Verónica Cecilia; Quispe, Rosa del Valle El molle, Schinus areira (Anacardiaceae), es una especie importante para los pobladores por sus múltiples aplicaciones. La falta de conocimiento sobre factores bióticos que pudieran incidir en la sanidad de este recurso motivó la realización del presente trabajo, cuyos objetivos fueron: identificar y evaluar la presencia, rol trófico y abundancia de los insectos asociados a S. areira en la Quebrada de Humahuca, Jujuy. Se realizaron 8 muestreos estacionales en cinco localidades de la Quebrada de Humahuaca. Cada muestra aleatoria consistió de 10 ramas de 20 cm, provenientes de 10 plantas de S. areira, llevándose un registro de la presencia y abundancia de las especies, en relación al estado fenológico del molle. Se recolectaron 679 ejemplares: Hemiptera (396), Lepidoptera (122), Thysanoptera (104), Hymenoptera (34), Diptera (13), Coleoptera (9) y Neuroptera (1). Las especies más relevantes en términos de abundancia, distribución y grado de daño que ocasionan al follaje de la planta fueron: Calophya schini Tuthill (Hemiptera), especie cecidógena de hojas, y la defoliadora Tolype guentheri (Lepidoptera). Las antófilas estuvieron representadas por Thysanoptera: Thrips tabaci, Frankliniella australis, F. gemina, F. occidentalis y F. valdiviana. Los frutos son atacados por Megastigmus sp. (Hymenoptera) y Lithraeus sp. (Coleoptera). Entre las benéficas se destaca el parasitoide de T. guentheri: Horismenus sp., (Hymenoptera). Entre los predadores de trips, pulgones y cochinillas se registraron especies de Anthocoridae (Hemiptera), Hyperaspis sp. (Coleoptera: Coccinellidae) y Hemerobiidae (Neuroptera).; The Pepper tree, Schinus areira (Anacardiaceae), is a valuable species to native inhabitants because of its multiple applications. The lack of knowledge on biotic factors that could affect the health of this resource motivated the present study. The objectives were: to identi fy and evaluate the presence, trophic role and abundance of the insects associated with S. areira in Quebrada de Humahuaca, Jujuy. Eight seasonal samples were carried out at five localities in Quebrada de Humahuaca. Each random sample consisted of 10 twenty-cm-long S. areira branches from 10 plants, recording the presence and abundance of each species in relation to the molle phenological stages. Six hundred and seventy nine specimens were collected: Hemiptera (396), Lepidoptera (122), Thysanoptera (104), Hymenoptera (34), Diptera (13), Coleoptera (9) and Neuroptera (1). The most relevant species in terms of abundance of specimens, distribution and degree of damage caused to foliage of the plant were: Calophya schini (Hemiptera), a cecidogenous species found on leaves, and the defoliating species Tolype guentheri (Lepidoptera). Anthophilous species were represented by Thysanoptera, such as Thrips tabaci, Frankliniella australis, F. gemina, F. occidentalis and F. valdiviana. Fruits were attacked by Megastigmus sp. (Hymenoptera) and Lithraeus sp. (Coleoptera). Among beneficial species, the parasitoid Horismenus sp. (Hymenoptera) of T. guentheri was observed. Among predators of thrips, aphids and scale insects, specimens of Anthocoridae (Hemiptera), Hyperaspis sp. (Coleoptera: Coccinellidae) and Hemerobiidae (Neuroptera) were recorded.

A Class of Inexact Variable Metric Proximal Point Algorithms Parente, Lisandro Armando; Lotito, Pablo Andres; Solodov, M. V. For the problem of solving maximal monotone inclusions, we present a rather general class of algorithms, which contains hybrid inexact proximal point methods as a special case and allows for the use of a variable metric in subproblems. The global convergence and local linear rate of convergence are established under standard assumptions. We demonstrate the advantage of variable metric implementation in the case of solving systems of smooth monotone equations by the proximal Newton method.

Age-related lung cell response to urban Buenos Aires air particle soluble fraction Ostachuk, Agustin Ignacio; Evelson, Pablo Andrés; Martin, Susana; Dawidowski, Laura Elena; Yakisich, J. Sebastián; Tasat, Deborah Ruth Exposure to particulate matter (PM) may alter lung homeostasis inducing changes in fluid balance and host defense. Bioavailability of soluble PM compounds like polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and transition metals has been shown to play a key role in lung injury. We have previously characterized the size, shape, and chemical components of urban air particles from Buenos Aires (UAP-BA) and their biological impact on lungs. Herein, we evaluate the possible toxic effect of UAP-BA-soluble fraction (UAP-BAsf) on pulmonary cells obtained from young (1-2 months old) and aged (9-12 months old) Wistar rats using phagocytosis, oxidant-antioxidant generation, and apoptosis as endpoints. UAP-BA were collected in downtown BA and residual oil fly ash (ROFA), employed as a positive control, was collected from Boston Edison Co., Mystic Power Plant, Mystic, CT, USA. Both particle-soluble fractions (sf) were employed at concentrations ranging from 0 to 100 microg/mL. UAP-BAsf and ROFAsf even at the lowest dose assayed (10 microg/mL) showed in both lung cell populations the ability to stimulate phagocytosis and increase superoxide anion (O(2)(-)) generation. Both types of air particles caused a marked intracellular oxidant stress in aged pulmonary cells that may contribute to subsequent cell activation and production of proinflammatory mediators, leading to cell dysfunction. These data suggest that the impact of UAP-BAsf on phagocytosis, oxidant radical generation, and apoptosis is clearly dependent on the maturational state of the animal and might have different mechanisms of action.

Sympatry inference and network analysis in biogeography Dos Santos, Daniel Andrés; Fernandez, Hugo Rafael; Cuezzo, Maria Gabriela; Dominguez, Eduardo A new approach for biogeography to find patterns of sympatry, based on network analysis, is proposed. Biogeographic analysis focuses basically on sympatry patterns of species. Sympatry is a network (= relational) datum, but it has never been analyzed before using relational tools such as Network Analysis. Our approach to biogeographic analysis consists of two parts: first the sympatry inference and second the network analysis method (NAM). The sympatry inference method was designed to propose sympatry hypothesis, constructing a basal sympatry network based on punctual data, independent of a priori distributional area determination. In this way, two or more species are considered sympatric when there is interpenetration and relative proximity among their records of occurrence. In nature, groups of species presenting within-group sympatry and between-group allopatry constitute natural units (units of co-occurrence). These allopatric units are usually connected by intermediary species. The network analysis method (NAM) that we propose here is based on the identification and removal of intermediary species to segregate units of co-occurrence, using the betweenness measure and the clustering coefficient. The species ranges of the units of co-occurrence obtained are transferred to a map, being considered as candidates to areas of endemism. The new approach was implemented on three different real complex data sets (one of them a classic example previously used in biogeography) resulting in (1) independence of predefined spatial units; (2) definition of co-occurrence patterns from the sympatry network structure, not from species range similarities; (3) higher stability in results despite scale changes; (4) identification of candidates to areas of endemism supported by strictly endemic species; (5) identification of intermediary species with particular biological attributes. Copyright © Society of Systematic Biologists.

The cactus-specialist bees of the genus brachyglossula Hedicke (Hymenoptera: Colletidae): Notes on host associations and description of a new species Roig Alsina, Arturo Hernan; Schlumpberger, Boris O. The pollen-collecting behavior of three species of the South American Andean bee genus Brachyglossula is reported. Species studied are B. martinezi Trucco Alemn, B. communis Trucco Alemn, and B. ancasti Roig Alsina and Schlumpberger, new species. The new species, which is comparatively described and illustrated, inhabits the isolated mountain range of Sierra de Ancasti, in the province of Catamarca, Argentina. Observation of the bees in the field, and pollen counts from scopal loads strongly support specialization of these bees on the Cactaceae. Members of both major cactus subfamilies, the Opuntioideae and the Cactoideae, are frequently visited and represented in the pollen loads.

QTL detection for milk production traits in goats using a longitudinal model Roldán, D.L.; Rabasa, Alicia Elvira; Saldaño, S.; Holgado, F.; Poli, M. A.; Cantet, Rodolfo Juan Carlos Summary Eight paternal half-sib families were used to identify chromosomal regions associated with variation in the lactation curves of dairy goats. DNA samples from 162 animals were amplified by PCR for 37 microsatellite markers, from Capra hircus autosomes CHI3, CHI6, CHI14 and CHI20. Milk samples were collected during 6 years, and there were 897 records for milk yield (MY) and 814 for fat (FP) and protein percentage (PP). The analysis was conducted in two stages. First, a random regression model with several fixed effects was fitted to describe the lactation function, using a scale (α) plus four shape parameters: β and γ, both associated with a decrease in the slope of the curve, and δ and φ that are related to the increase in slope. Predictions of α, β, γ, δ and φ were regressed using an interval mapping model, and F-tests were used to test for quantitative trait loci (QTL) effects. Significant (p < 0.05) QTLs were found for: (i) MY: CHI6 at 70-80 cM for all parameters; CHI14 at 14 cM for δ and φ; (ii) FP: CHI14, at 63 cM was associated with β; CHI20, at 72 cM, showed association with α; (iii) PP: chromosomal regions associated with β were found at 59 cM in CHI3 and at 55 cM in CHI20 with α and γ. Analyses using more families and more animals will be useful to confirm or to reject these findings. © 2008 Blackwell Verlag, Berlin.

Effects of natural phenolic compounds from a desert dominant shrub Larrea divaricata Cav. on toxicity and survival in mice; Efectos de los compuestos fenólicos naturales de un arbusto dominante del desierto, Larrea divaricata Cav. sobre la toxicidad y sobrevida en ratones Ríos, Juan Manuel; Mangione, Antonio Marcelo; Gianello, Jose Carlos Los herbívoros generalistas pueden evitar la intoxicación ingiriendo pequeñas cantidades de una mezcla de metabolitos secundarios de plantas. Sin embargo, un solo compuesto, uno altamente tóxico o el más abundante en la mezcla es el que podría causar la intoxicación. La sobrevida y la toxicidad en ratones Rockland machos fueron evaluadas para determinar si los efectos tóxicos de la resina fenólica de jarilla (Larrea divaricata Cav.) se debe a su compuesto mayoritario, el ácido nordihidroguaiarético (ANDG) o a la concentración total de compuestos fenólicos en esta resina. Este objetivo fue logrado mediante la exposición de ratones a la alimentación voluntaria de alimento para rata tratado con resina y mediante el gavage oral de ratones con las siguientes dosis y compuestos: Resina-100 mg (n = 7), ANDG-15 mg (n = 8), ANDG-100 mg (n = 10) y Control (n = 6). Nuestra hipótesis fue que los efectos tóxicos de Larrea divaricata son atribuibles al ANDG solamente. La ingesta voluntaria de resina por ratones tuvo un efecto tóxico pronunciado, evidenciado en una pérdida en masa corporal y una reducción significativa de la ingesta de alimento. Ratones expuestos a gavage con Resina-100 mg, ANDG-100 mg y ANDG-15 mg mostraron una reducción significativa de la sobrevida comparada con ratones bajo las condiciones Control. Animales expuestos a ANDG-15 mg tuvieron una mayor sobrevida comparado con animales expuestos a ANDG-100 mg y una sobrevida equivalente a los animales expuestos a Resina-100 mg (que contiene a su vez 15 mg de ANDG). No se detectaron diferencias significativas en la detoxificación medida como conjugados de ácido glucurónico en orina entre los tratamientos de gavage. Dado que 15 mg de ANDG fueron suficientes para producir el mismo efecto que la resina total, sugerimos que el ANDG es el constituyente principal de la resina de Larrea divaricata responsable del efecto tóxico de esta planta.; It is known that generalist herbivores may circumvent intoxication by ingesting small quantities from a mixture of plant secondary metabolites. However a single chemical, a highly toxic one or the most abundant in the mixture could cause toxicity. Survivorship and toxicity in Rockland male mice were measured to determine if the toxic effects of the phenolic resin of creosote bush (Larrea divaricata Cav.) is due to its major constituent, the nordihydroguaiaretic acid (NDGA) or to the total concentration of phenolic compounds in this resin. This objective was accomplished by exposing mice to voluntary feeding on resin-treated rat chow and by oral gavaging of mice with the following doses and compounds: Resin-100 mg (n = 7), NDGA-15 mg (n = 8), and NDGA-100 mg (n = 10) and Control (n = 6). Our hypothesis was that NDGA is responsible for the toxicity of Larrea divaricata's phenolic resin. Voluntary resin intake by mice had a pronounced toxic effect, producing body mass loss and significant reduction of food intake. Mice gavaged with Resin-100 mg, NDGA-100 mg, and NDGA-15 mg showed a significant reduction in survival probability compared to mice under Control conditions. Animáis exposed to NDGA-15 mg had a higher survivorship compared to the NDGA-100 mg animáis, and equivalent survivorship to the Resin-100 mg (containing 15 mg of NDGA) animáis. No significant differences in detoxification, measured as glucuronic acid conjugates in urine, were detected among gavage treatments. Therefore, given that just 15 mg of NDGA were enough to produce the same effect as the whole resin, we suggest that NDGA is the main constituent of Larrea divaricata's resin responsible for the toxic effect of the phenolic resin of this plant.

Prognostic value of Bcl-2 in breast cancer patients treated with neoadjuvant anthracycline based chemotherapy Vargas Roig, Laura Maria; Cuello Carrión, Fernando Darío; Fernández-Escobar, Nicolás; Daguerre, Pedro; Leuzzi, Marcela; Ibarra, Jorge; Gago, Francisco E.; Nadin, Silvina Beatriz; Ciocca, Daniel Ramon We have analyzed the predictive/prognostic value of Bcl-2 protein in breast cancer patients treated with neoadjuvant chemotherapy. One hundred and ten patients were submitted to two different chemotherapeutic regimens: a) 5-fluorouracil, adriamycin or epirubicin, and cyclophosphamide (FAC/FEC) during 2-6 cycles before surgery and 3 or 4 additional cycles of FAC/FEC after surgery (n = 40) and b) doxorubicin (D) 75 mg/m2 or epirubicin (E) 120 mg/m2 during 4 cycles before surgery, and 6 cycles of cyclophosphamide, methotrexate, and 5-fluorouracil (CMF) after surgery (n = 70). Bcl-2 expression, evaluated by immunohistochemistry, did not change significantly after chemotherapy and was not related to clinical/pathological response. In FAC/FEC group, Bcl-2 positive expression after chemotherapy correlated with better disease free survival (DFS) and overall survival (OS) (P = 0.008 and P = 0.001). In D/E group, Bcl-2 also correlated with better DFS and OS (P = 0.03 and P = 0.054) in the post-chemotherapy biopsies. An unusual nuclear localization of Bax was observed in some biopsies, but this localization did not correlate with the tumor response or outcome of the patients. We found that a high Bcl-2 expression had no predictive value but had prognostic value in breast cancer patients treated with neoadjuvant anthracycline based chemotherapy.

Ear tufts in Ferruginous Pygmy-Owl (Glaucidium brasilianum) as alarm response Santillan, Miguel Angel; Sarasola, José Hernán; Dolsan, Marcelo

Eficiencia relativa de distintas técnicas de captura de heterópteros terrestres en un pastizal de montaña Marrero, Hugo Javier; Zalba, Sergio Martín; Carpintero, Diego Leonardo Los insectos habitan múltiples micro-ambientes y tienen nichos tróficos muy variados, razón por la cual existen diversas alternativas para su detección. En este trabajo se testeo el uso de distintas técnicas de captura de heterópteros terrestres sobre un pastizal de montaña, procurando la técnica o la combinación de técnicas que mejor representara la diversidad del grupo y que insumiera el menor esfuerzo, de manera de optimizar acciones de monitoreo. El trabajo se realizó durante las cuatro estaciones del año, sobre cuatro niveles altitudinales en la ladera del Cerro Curamalal (provincia de Buenos Aires) usando trampas de caída, red entomológica, trampa de luz y captura manual. La red entomológica resultó la técnica más eficiente, seguida por las trampas de caída, la captura manual y la trampa de luz. La combinación de captura manual y red entomológica rindieron los mejores resultados en términos de representación de la diversidad de heterópteros en el área de estudio. Se determinó además que la época de primavera-verano y los estratos intermedios de altura concentran la mayor diversidad específica del grupo.; Insects thrive in multiple micro-habitats and correspond to diverse trophic niches which is why there are multiple and diverse alternatives for their sampling. In this study we tested different techniques for capturing terrestrial heteropterans in a mountain grassland searching for the technique or combination of techniques that best represented this group´s biodiversity in the area. Sampling took place during all four seasons at four altitudinal levels on the Curamalal hill (Buenos Aires province) and we compared pit-fall traps, entomological net, light traps, and manual capture. When considering each technique separately, entomological nets rendered the best performance, followed by pit-fall traps, manual capture and light traps. The combination of entomological net and manual capture resulted in the best representation of heteropteran diversity in the study area. Spring and summer and intermediate heights on the hills concentrate the highest species diversity in this group of insects.

Deactivation studies of the SCR of NOx with hydrocarbons on Co-mordenite monolithic catalysts Boix, Alicia Viviana; Aspromonte, Soledad Guadalupe; Miro, Eduardo Ernesto The catalytic reduction of NOx with hydrocarbons (butane or methane) on CoMOR washcoated monolithic catalysts was studied in the presence of steam and excess oxygen. The significant changes observed in the catalytic behavior of CoMOR powder and monoliths depended essentially on the hydrocarbon nature (carbon number) and the concentration of water in the feed. When the reducing agent was methane, a low concentration of water (2%) decreased the NO to N2 conversion. However, when butane was used instead of methane, the maximum NOx conversions increased from 50 to 58% and from 52 to 64% for the CoMOR powder and monolith, respectively. The presence of water inhibited the NO adsorption when the reducing agent was methane but when butane was used, water helped to remove the surface-carbon deposits as indicated by TPO and XPS results. This fact explains the increase observed in the NOx conversion. The characterization with TPR and UV-vis spectroscopy showed that the main Co species present in the selective catalysts were the Co(II) ions exchanged at different sites of the mordenite and highly dispersed CoxOy moieties. More rigorous reaction conditions, i.e. 10% of water, led to the irreversible deactivation with both reductants. The Co3O4 phase was detected in all the deactivated powder and monolithic catalysts. The Co3O4 spinel was formed from the cobalt ion migration, which was promoted in wet atmosphere. In addition, for monolithic catalysts washcoated with CoMOR, the silica binder inhibited the water deactivation effect probably due to the silica-cobalt interaction, as a CoxOySi silicate.

The ATLAS Experiment at the CERN Large Hadron Collider Piegaia, Ricardo Nestor; Aad, G.; Romeo, G.; Sanchis Lozano, M.A; Miyagawa, P.S.; Antonelli, S.; Bendel, M.; Breiler, B.; Castrovillari, F.; Civera, J.V.; Del Prete, T.; Duffin, S.; Fichet, S.; Gaumer, O.; Goodrick, M. J.; Goujdami, D.; Herten, G.; Jeremie, A; Kieft, G.; König, S.; Kirk, J.; Lapin, V.V.; LeGeyt, B.C.; Love, J.; Merola,L.; Raith, B.; Plamondon, M.; Saavedra, A.F.; Schott, M.; Soloviev, I. The ATLAS detector as installed in its experimental cavern at point 1 at CERN is described in this paper. A brief overview of the expected performance of the detector when the Large Hadron Collider begins operation is also presented.

Emulsion Polymerization of Styrene with iso-octyl-3-mercaptopropionate as Chain Transfer Agent Minari, Roque Javier; Vega, Jorge Ruben; Gonzalez Sierra, Manuel; Meira, Gregorio Raul; Gugliotta, Luis Marcelino Four batch and unseeded emulsion polymerizations of styrene were investigated, which included isooctyl 3-mercaptopropionate (iOMP) as chain transfer agent (CTA). This compound was analyzed by 13C NMR and GC/ MS, resulting in a mixture of over 10 isomers. Because of different reactivities of the CTA isomers, the produced polystyrenes presented broad and bimodal molecular weight distributions (MWDs). A mathematical model was adjusted to the measurements, and the measured MWDs were adequately predicted when assuming the CTA as a binary mixture of high but different reactivities.

Universidad, interculturalidad y discurso público: La universidad en un contexto social democrático; University, interculturality and public discourse: The university in a social-democratic context; Université, interculturalité et discours public: L’universite dans un contexte social-démocratique Michelini, Dorando Juan La universidad constituye el lugar privilegiado de la sociedad civil en el que los ciudadanos buscan nuevos conocimientos y se preparan para participar como expertos en la tematización, discusión y resolución de todas aquellas cuestiones teóricas y prácticas relevantes para la sociedad. La educación universitaria tiene que contribuir, por consiguiente, a la formación de docentes e investigadores, tecnólogos y expertos en las diversas esferas del saber, y a la capacitación para la reflexión crítica a través del desarrollo de competencias discursivas, éticas y culturales. En este sentido, los universitarios son -tendrían que ser- personas capacitadas no sólo para aumentar metódica y sistemáticamente el conocimiento, sino también para reflexionar críticamente sobre cuestiones centrales de la convivencia humana en un sistema democrático. Por ello, los universitarios tendrían que ser profesionales y expertos, a la vez que “personas de principios”, conocedoras de su propia cultura y del contexto histórico de aplicación.; The university constitutes the privileged place of civil society in which citizens seek new knowledge and prepare themselves to participate as experts in the discussion and resolution of all theoretical and practical issues relevant to society. University education has to contribute, therefore, to the formation of teachers and researchers, technologists and experts in the diverse spheres of knowledge, and to the training for critical thinking through the development of ethical, cultural and discursive skills. In this regard, university graduates are - should be- people qualified not only to enlarge their knowledge methodically and systematically, but also to reflect critically on central questions of human coexistence in a democratic system. Thus, university graduates would have to be professionals and experts as well as "people of principles", proficient in their own culture and in the historical context of implementation.; L’Université constitue l’endroit privilégié de la société civile où les citoyens cherchent de nouvelles connaissances et se préparent pour participer en tant qu’experts, à la thématisation, la discussion et la résolution de toutes les questions théoriques et pratiques remarquables pour la société. En conséquence, l’éducation universitaire doit contribuer à la formation d´enseignants et de chercheurs, de technologues et d’experts dans les diverses sphères du savoir et à la préparation à la réflexion critique à travers le développement de compétences discursives, éthiques et culturelles. Dans ce sens, les universitaires sont –devraient être- des personnes prêtes, non seulement à accroître méthodiquement et systématiquement la connaissance mais aussi à réfléchir de manière critique sur les questions centrales de la vie en commun dans un système démocratique. Les universitaires devraient être des professionnels et des experts, mais en même temps des «gens de principes», connaisseurs de leur propre culture et du contexte historique d’application.

Factors affecting the use of 13Cα chemical shifts to determine, refine, and validate protein structures Vila, Jorge Alberto; Scheraga, Harold A. Interest centers here on the analysis of two different, but related, phenomena that affect side-chain conformations and consequently 13Cα chemical shifts and their applications to determine, refine, and validate protein structures. The first is whether 13Cα chemical shifts, computed at the DFT level of approximation with charged residues is a better approximation of observed 13Cα chemical shifts than those computed with neutral residues for proteins in solution. Accurate computation of 13Cα chemical shifts requires a proper representation of the charges, which might not take on integral values. For this analysis, the charges for 139 conformations of the protein ubiquitin were determined by explicit consideration of protein binding equilibria, at a given pH, that is, by exploring the 2ξ possible ionization states of the whole molecule, with ξ being the number of ionizable groups. The results of this analysis, as revealed by the shielding/deshielding of the 13Cα nucleus, indicated that: (i) there is a significant difference in the computed 13Cα chemical shifts, between basic and acidic groups, as a function of the degree of charge of the side chain; (ii) this difference is attributed to the distance between the ionizable groups and the 13Cα nucleus, which is shorter for the acidic Asp and Glu groups as compared with that for the basic Lys and Arg groups; and (iii) the use of neutral, rather than charged, basic and acidic groups is a better approximation of the observed 13Cα chemical shifts of a protein in solution. The second is how side-chain flexibility influences computed 13Cα chemical shifts in an additional set of ubiquitin conformations, in which the side chains are generated from an NMR-derived structure with the backbone conformation assumed to be fixed. The 13Cα chemical shift of a given amino acid residue in a protein is determined, mainly, by its own backbone and side-chain torsional angles, independent of the neighboring residues; the conformation of a given residue itself, however, depends on the environment of this residue and, hence, on the whole protein structure. As a consequence, this analysis reveals the role and impact of an accurate side-chain computation in the determination and refinement of protein conformation. The results of this analysis are: (i) a lower error between computed and observed 13Cα chemical shifts (by up to 3.7 ppm), was found for ∼68% and ∼63% of all ionizable residues and all non-Ala/Pro/Gly residues, respectively, in the additional set of conformations, compared with results for the model from which the set was derived; and (ii) all the additional conformations exhibit a lower root-mean-square-deviation (1.97 ppm ≤ rmsd ≤ 2.13 ppm), between computed and observed 13Cα chemical shifts, than the rmsd (2.32 ppm) computed for the starting conformation from which this additional set was derived. As a validation test, an analysis of the additional set of ubiquitin conformations, comparing computed and observed values of both 13Cα chemical shifts and χ1 torsional angles (given by the vicinal coupling constants, 3JN−Cγ and 3JC′−Cγ, is discussed.

Anatomía foliar de Rauvolfia schuelii Speg. (Apocynaceae), en la provincia de Tucumán (Argentina); Leaf anatomy of Rauvolfia schuelii (Apocynaceae), in the Tucumán province, Argentina Debes, Mario Alberto; Luque, Ana Catalina; Arias, Marta Eugenia; Albornoz, Patricia Liliana Mario Alberto Debes, Ana Catalina Luque, Marta Eugenia Arias, Patricia Liliana Albornoz. 2008. “Anatomía foliar de Rauvolfia schuelii (Apocynaceae), en la provincia de Tucumán, Argentina”. Lilloa 45 (1-2). Rauvolfia schuelii Speg. es un arbusto o arbolito de 2-6 m de altura, se distribuye en el noroeste de Argentina, entre los 450-1500 m snm. El objetivo del presente trabajo fue estudiar la anatomía foliar de Rauvolfia schuelii Speg. en la provincia de Tucumán. Se utilizó material fresco y fijado en FAA; se realizaron diafanizados, cortes transversales y longitudinales de lámina y pecíolo mediante técnicas anatómicas convencionales. Los resultados muestran que la hoja es dorsiventral, hipostomática, con cutícula estriada. Se presentan diferentes tipos de estomas: hemiparacítico, paracítico, anisocítico, tetracítico, ciclocítico y actinocítico. El pecíolo en sección transversal es subcircular con coléteres en la base. Las drusas y los haces vasculares bicolaterales se presentan en lámina y pecíolo. Los tubos latifíceros son articulados ramificados y no articulados en toda la lámina. Estos caracteres anatómicos son válidos para la correcta identificación de esta especie.; Rauvolfia schuelii Speg. is a shrub or tree about 2-6 m high. In the northwestern of Argentina it grows between 450-1500 m snm. The aim of this work was to study the leaf anatomy of Rauvolfia schuelii in Tucumán. Conventional anatomical techniques were applied. The leaf is dorsiventral and hypostomatic. There are six types of sto- mata: hemiparacytic, paracytic, anisocytic, tetracytic, cyclocytic and actinocytic. The petiole in transversal section is subcircular with colleters at the base. Druses, colateral vascular bundle and laticiferous tubes in laef and petiole are observed. Results show that leaf anatomical features permit to identify these species.

Coordination of leaf and stem water transport properties in tropical forest trees Meinzer, Frederick C.; Woodruff, David R.; Domec, Jean-Christophe; Goldstein, Guillermo Hernan; Campanello, Paula Inés; Gatti, Maria Genoveva; Villalobos-Vega, Randol Stomatal regulation of transpiration constrains leaf water potential (ΨL) within species-specific ranges that presumably avoid excessive tension and embolism in the stem xylem upstream. However, the hydraulic resistance of leaves can be highly variable over short time scales, uncoupling tension in the xylem of leaves from that in the stems to which they are attached. We evaluated a suite of leaf and stem functional traits governing water relations in individuals of 11 lowland tropical forest tree species to determine the manner in which the traits were coordinated with stem xylem vulnerability to embolism. Stomatal regulation of ΨL was associated with minimum values of water potential in branches (Ψbr) whose functional significance was similar across species. Minimum values of Ψbr coincided with the bulk sapwood tissue osmotic potential at zero turgor derived from pressure-volume curves and with the transition from a linear to exponential increase in xylem embolism with increasing sapwood water deficits. Branch xylem pressure corresponding to 50% loss of hydraulic conductivity (P 50) declined linearly with daily minimum Ψbr in a manner that caused the difference between Ψbr and P 50 to increase from 0.4 MPa in the species with the least negative Ψbr to 1.2 MPa in the species with the most negative Ψbr. Both branch P 50 and minimum Ψbr increased linearly with sapwood capacitance (C) such that the difference between Ψbr and P 50, an estimate of the safety margin for avoiding runaway embolism, decreased with increasing sapwood C. The results implied a trade-off between maximizing water transport and minimizing the risk of xylem embolism, suggesting a prominent role for the buffering effect of C in preserving the integrity of xylem water transport. At the whole-tree level, discharge and recharge of internal C appeared to generate variations in apparent leaf-specific conductance to which stomata respond dynamically.