Nitric oxide system alteration at spinal cord as a result of perinatal asphyxia is involved in behavioral disabilities: hypothermia as preventive treatment Dorfman, Verónica Berta; Rey Funes, Manuel; Bayona, Julio César; Lopez, Ester Maria; Coirini, Hector; Loidl, Cesar Fabian Perinatal asphyxia (PA) is able to induce sequelae such as spinal spasticity. Previously, we demonstrated hypothermia as a neuroprotective treatment against cell degeneration triggered by increased nitric oxide (NO) release. Because spinal motoneurons are implicated in spasticity, our aim was to analyze the involvement of NO system at cervical and lumbar motoneurons after PA as well as the application of hypothermia as treatment. PA was performed by immersion of both uterine horns containing full-term fetuses in a water bath at 37 degrees C for 19 or 20 min (PA19 or PA20) or at 15 degrees C for 20 min (hypothermia during PA-HYP). Some randomly chosen PA20 rats were immediately exposed for 5 min over grain ice (hypothermia after PA-HPA). Full-term vaginally delivered rats were used as control (CTL). We analyzed NO synthase (NOS) activity, expression and localization by nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) reactivity, inducible and neuronal NOS (iNOS and nNOS) by immunohistochemistry, and protein nitrotyrosilation state. We observed an increased NOS activity at cervical spinal cord of 60-day-old PA20 rats, with increased NADPH-d, iNOS, and nitrotyrosine expression in cervical motoneurons and increased NADPH-d in neurons of layer X. Lumbar neurons were not altered. Hypothermia was able to maintain CTL values. Also, we observed decreased forelimb motor potency in the PA20 group, which could be attributed to changes at cervical motoneurons. This study shows that PA can induce spasticity produced by alterations in the NO system of the cervical spinal cord. Moreover, this situation can be prevented by perinatal hypothermia.

Murine abortion is associated with enhanced Hyaluronan expression and abnormal localization at the fetomaternal interface Cordo Russo, Rosalia Ines; García, Mariana Gabriela; Barrientos, Gabriela Laura; Orsal, A. S.; Viola, M.; Moschansky, Petra; Ringel, F.; Passi, A.; Alaniz, Laura Daniela; Hajos, Silvia Elvira; Blois, Sandra M. The remodelling of the endometrial architecture is fundamental to create a suitable environment for the establishment of pregnancy. During this process, substantial alterations in the composition of maternal extracellular matrix play an important role by providing a prosperous medium for implantation as well as modulating trophoblast invasion leading to the formation of a functional placental unit. Hyaluronan is a conspicuous component of the extracellular matrix, particularly in remodelling tissues undergoing regeneration and repair. During gestation, changes in HA deposition and distribution indicate that this molecule may participate in preparation of the endometrial stroma for reception and implantation of the embryo. However, little is known about the role of hyaluronan at the fetomaternal interface, specially regarding its influence in pregnancy outcome. In the present study we show increased decidual hyaluronan levels in spontaneous abortion compared with normal pregnancy mice on gestation day 7.5. Both in normal and pathologic pregnancies, high molecular size hyaluronan was found at the fetomaternal unit. However, hyaluronan metabolism (which results from the activity of hyaluronan synthases and hyaluronidases) seems to be altered in spontaneous abortion as shown by a decrease in Hyal-3 expression as well as by differences in hyaluronan molecular size spectrum. This alteration in hyaluronan metabolism in spontaneous abortion could explain its increased concentration observed in decidua and the abnormal distribution of hyaluronan around the embryo implantation crypt. Thus, increased decidual hyaluronan levels resulting from abnormal deposition and turn over may contribute to the pathogenesis of pregnancy failure.

Involvement of c-Src tyrosine kinase in SHP-1 phosphatase activation by Ang II AT2 receptors in rat fetal tissues Alvarez, Sergio Eduardo; Seguin, Leonardo Roque; Villarreal, Rodrigo Sebastian; Nahmias, Clara; Ciuffo, Gladys Maria Angiotensin II (Ang II) AT2 receptors are abundantly expressed in rat fetal tissues where they probably contribute to development. In the present study we examine the effects of Ang II type 2 receptor stimulation on SHP-1 activation. Ang II (10-7 M) elicits a rapid and transient tyrosine phosphorylation of SHP-1, maximal at 1 min, in a dose-dependent form, blocked by the AT2 antagonist, PD123319. SHP-1 phosphorylation is followed in time by tyrosine dephosphorylation of different proteins, suggesting a sequence of events. Ang II induces association of SHP-1 to AT2 receptors as shown by co-immunoprecipitation, Western blot and binding assays. SHP-1 activity was determined in immunocomplexes obtained with either anti-AT2 or anti-SHP-1 antibodies, after Ang II stimulation (1 min), in correlation with the maximal level of SHP-1 phosphorylation. Interestingly, following receptor stimulation (1 min) c-Src was associated to AT2 or SHP-1 immunocomplexes. Preincubation with the c-Src inhibitor PP2 inhibited SHP-1 activation and c-Src association, thus confirming the participation of c-Src in this pathway. We demonstrated here for the first time the involvement of c-Src in SHP-1 activation via AT2 receptors present in an ex vivo model expressing both receptor subtypes. In this model, AT2 receptors are not constitutively associated to SHP-1 and SHP-1 is not constitutively activated. Thus, we clearly establish that SHP-1 activation, mediated by the AT2 subtype, involves c-Src and precedes protein tyrosine dephosphorylation, in rat fetal membranes.

Mechanochemical activation of a titanium-magnetite mixture: Mössbauer spectroscopy study Cristobal, Adrian Alberto; Aglietti, Esteban Fausto; Porto Lopez, Jose Manuel; Sives, Flavio Rubén; Mercader, Roberto Carlos Mechanochemical activation has become a valuable tool in the design and synthesis of novel materials, due to the increased reactivity of activated solids, and the possibility of synthesizing metastable phases not obtainable by conventional methods. In this work, ac magnetic susceptibility, Mössbauer spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy have been employed to study the structural and thermal evolution of a mechanochemically activated Ti-Fe3O4 mixture, with molar ratio Ti:Fe3O4 of 1:2. Upon activation in a high-energy planetary mill, the mixtures undergoes a redox reaction, in which the Ti reduces the Fe ions of the spinel, resulting in a solid solution of variable composition between magnetite (Fe3O4) and ulvospinel (TiFe2O4). The activation results in changes in the magnetic behavior of the mixture, and loss of crystallinity. Mössbauer spectroscopy and XRD show the progressive disappearance of the original phases, and the formation of Fe0, Fe2O3 and ulvospinel. © 2008 Elsevier Ltd. All rights reserved.

Determinación de la actividad de la oxido nítrico sintetasa endotelial y del factor NF-kB, en piel de pacientes con Pseudoangiomatosis eruptiva; Factor-ĸb expression and endothelial nitric oxide synthase activity in eruptive pseudoangiomatosis lesions Parra, Verónica Ester; Miatello, Roberto Miguel; Renna, Nicolas Federico; Driban, N.; Rivarola, Emilce La pseudoangiomatosis eruptiva se caracteriza por la aparición brusca de múltiples pápulas eritematosas, asintomáticas, rodeadas de un halo blanquecino, con remisión espontánea. Histológicamente se observa dilatación vascular con escaso infiltrado inflamatorio. Su etiología permanece incierta a pesar de ser relacionada con virus o picaduras de insectos. Basados en el compromiso vascular, el objetivo del trabajo fue investigar la actividad de la enzima endotelial oxido nítrico sintetasa (eNOS) y la expresión del factor NF-kB por inmunohistoquimica en un intento de esclarecer su patogenia. Material y métodos: Se estudiaron diez pacientes con diagnóstico clínico de pseudoangiomatosis eruptiva (PAE) que presentaron la dermatosis en forma epidémica. Se realizaron biopsias teñidas con Hematoxilina-Eosina y Tricrómico de Masson. Se efectuó estudio virológico de los pacientes Nª 4, 9 y 10 mediante determinaciones serológicas para echovirus, enterovirus, citomegalovirus, parvovirus B19 y hepatitis A, B y C. En cinco pacientes se obtuvo material para determinación de eNOS y NF-kB. Resultados: Todos los pacientes, 5 hombres y 5 mujeres presentaron pápulas eritematosas rodeadas por un halo blanquecino, especialmente en las extremidades, alrededor de las rodillas. Histológicamente mostraron vasos dilatados y células endoteliales prominentes con un infiltrado discreto perivascular. Todos los estudios serológicos fueron negativos. La actividad de eNOS fue significativamente menor comparada con la piel normal (p= 0,002) y la expresión de NF- ĸB fue fuertemente positiva en los vasos de la dermis papilar y reticular. Conclusiones: Todos los pacientes fueron afectados en verano, por lo que la picadura del mosquito debe ser considerada como un factor etiológico. La baja expresión de eNOS está relacionada con la vasodilatación y la expresión aumentada de NF-ĸB confirma que el proceso es de tipo inflamatorio.; Eruptive pseudoangiomatosis (EPA) is a dermatosis characterized by sparse erythematous papules, with vascular appearance and surrounded by a blanching halo. It has acute onset and spontaneous resolution. Histopathology shows vascular affection. Though it has been related to viral infection and insects bites its aetiology and pathogenesis remains unclear. Based on clinical and histological findings, related to vascular affection, the main objective was to observe changes in endothelial nitric oxide synthase (eNOS) activity and nuclear factor-ĸ B (NF-kB) expression related to inflammatory pathogenesis. Materials and methods: Samples from ten patients with clinical diagnosis of EPA were fixed for light microscopy in formalin solution, embedded in paraffin and stained with haematoxylin and eosin and Masson´s trichrome stain. In three patients serological testing for echovirus, enterovirus, cytomegalovirus, parvovirus A and B, hepatitis C and hepatitis B virus were performed. eNOS activity: in five patients snap-frozen tissue was obtained and homogenized in a buffer containing 250 mM sucrose, 50 mM tris-HCl pH 7.4 and added protease inhibitors: SBTI, aprotinin, PMSF, leupeptin, DTT and EDTA. The activity was evaluated in the supernatant measuring the conversion of L-[3H]-arginine in L-[3H]- citruline and subsequent liquid scintillation counting. 4. Expression of NF-ĸB, a promoter of inflammatory processes activated by redox status was determined by immunohistochemistry. Results: The patients, 5 women and 5 men, had 3 to 6 mm, red papules surrounded by a 2 to 5 mm blanching halo, especially located on the lower extremities, around knees, 5 5 forearms and arms. In two patients the lesions were also on the trunk and face. Histological findings show dilated dermal blood vessels with plump endothelial cells and perivascular lymphohistiocytic infiltrate. All serological tests for virus were negative. eNOS activity in lesions was significant lower when compared with normal skin (p= 0,002). NF-ĸB expression was strongly positive in dermal vessels of the papillary and reticular dermis. Conclusions: As all our patients were affected in summer, mosquito bites must be considered as etiologic factor. eNOS lower expression suggests that probably it has no role in this inflammatory process, but linked to blood stasis. The increased expression of NF-ĸB confirms that the inflammatory process is related to the developing process.

Análisis cromosómico aplicado a la diferenciación de Lotus glaber y L. corniculatus (Fabaceae) Celotto, Adriana Inés; Sanso, Andrea Mariel En la región de la pampa deprimida, debido al déficit de leguminosas nativas de los pastizales naturales, Lotus tenuis Waldst & Kit. y L. corniculatus L. son utilizadas como especies forrajeras por sus buenas cualidades nutritivas y preferencia animal. Se trata de especies de gran interés agronómico, estrechamente relacionadas, con gran similitud fenotípica pero con distintas aptitudes forrajeras, ecológicas y valor económico. Las semillas de estas especies de Lotus no manifiestan características macromorfológicas que permitan diferenciarlas. Tampoco pueden ambas especies identificarse tempranamente en forma concluyente, considerando las  características morfológicas de las plántulas. Nuestra investigación surge como respuesta a la necesidad de diferenciar estas dos especies en el estado de semilla o durante la germinación utilizando metodologías que resulten suficientemente rápidas, confiables, económicas y reproducibles. Para ello, se llevaron a cabo estudios cromosómicos. Se lograron estandarizar las técnicas citogenéticas para estudiar cromosómicamente a L. tenuis (2n = 12) y a L. corniculatus (2n = 24). Los cultivares estudiados resultaron ser homogéneos en relación al número cromosómico aunque se encontraron algunos individuos con números diferentes. El análisis de  muestras provistas por laboratorios privados reveló que se distribuye bajo distintas denominaciones la misma especie. Suele comercializarse  L. corniculatus  bajo la denominación de L. tenuis. El análisis cromosómico, brinda resultados rápidos, confiables y reproducibles para la diferenciación específica entre ambas especies. Las técnicas citogenéticas utilizadas podrían implementarse en laboratorios con un limitado equipamiento y un relativo bajo costo.

Weighting against homoplasy improves phylogenetic analysis of morphological data sets Goloboff, Pablo Augusto; Carpeneter, James M.; Arias Becerra, Joan Salvador; Miranda Esquivel, Daniel Rafael The problem of character weighting in cladistic analysis is revisited. The finding that, in large molecular data sets, removal of third positions (with more homoplasy) decreases the number of well supported groups has been interpreted by some authors as indicating that weighting methods are unjustified. Two arguments against that interpretation are advanced. Characters that collectively determine few well-supported groups may be highly reliable when taken individually (as shown by specific examples), so that inferring greater reliability for sets of characters that lead to an increase in jackknife frequencies may not always be warranted. But even if changes in jackknife frequencies can be used to infer reliability, we demonstrate that jackknife frequencies in large molecular data sets are actually improved when downweighting characters according to their homoplasy but using properly rescaled functions (instead of the very strong standard functions, or the extreme of inclusion ⁄ exclusion); this further weakens the argument that downweighting homoplastic characters is undesirable. Last, we show that downweighting characters according to their homoplasy (using standard homoplasy-weighting methods) on 70 morphological data sets (with 50?170 taxa), produces clear increases in jackknife frequencies. The results obtained under homoplasy weighting also appear more stable than results under equal weights: adding either taxa or characters, when weighting against homoplasy, produced results more similar to original analyses (i.e., with larger numbers of groups that continue being supported after addition of taxa or characters), with similar or lower error rates (i.e., proportion of groups recovered that subsequently turn out to be incorrect). Therefore, the same argument that had been advanced against homoplasy weighting in the case of large molecular data sets is an argument in favor of such weighting in the case of morphological data sets.

Actividad antioxidante de alimentos consumidos en Argentina Nazareno, Mónica Azucena; González, Evangelina A.; Garcia, Marian; Loto, Cecilia; Coria Cayupán, Yanina Soledad En la naturaleza existen muchos grupos de sustancias antioxidantes. Muchos de ellos son de origen vegetal y están ampliamente difundidos en alimentos por lo que son aportados a nuestro organismo a través de la dieta. Numerosos estudios indican que el consumo de frutas y verduras esta relacionado con menores incidencias de enfermedades cardiovasculares y algunos tipos de cáncer, sugiriendo que una dieta rica en estos alimentos ejerce efectos benéficos para la salud y éstos son asociados a la acción de sus componentes antioxidantes

Validation of WEQ, RWEQ and WEPS wind erosion for different arable land management systems in the Argentinean Pampas Buschiazzo, Daniel Eduardo; Zobeck, Ted M. Wind erosion is an important soil degradation process in the semi-arid Pampas of Argentina, but no attempts have been made to predict the process in this region. One limitation for the use of event-based wind erosion prediction models is the lack of reliable climatic data to initiate these models. As an effort to apply wind erosion models, we compared field wind erosion measurements carried out during 4 years in a bare soil reference plot (RP) and during 3 years in the same soil with different tillage conditions: conventional (CT) and no-till (NT). Wind erosion was predicted with: (1) subroutines for single storm event versions of the wind erosion prediction system (WEPS) and the revised wind erosion equation (RWEQ), for which the climatic data of each single storm were used, and (2) the wind erosion equation (WEQ) for full rotation periods, for which long-term climatic records (1961-2004) were used. Wind erosion field measurements were carried out with BSNE samplers in 1-ha plots. Regression of predicted soil erosion rates from WEPS (y = 0·5192x + 0·0589, R2 = 0·89) and RWEQ (y = 0·5691x - 7·071, R2 = 0·90) predictions with field measurements of soil erosion rates obtained in RP (54·51 kg m-1 on average) were highly significant, but both models underestimated wind erosion by 40-45 percent. Predictions of wind erosion made with RWEQ were highly sensitive to variations in the soil crusting factor (SCF), varying from 60·5 t m-1 when predictions for a single storm were made using the SCF default data to 0·699 t m-1 when SCF was deduced from visual field observations. The WEQ predictions agreed adequately with measured erosion for 16 rotation periods either when using a climatic C factor value of 92, corresponding to the 1961-2004 period (y=0·9422x - 1·9248, R2=0·96) or a C factor value of 80, corresponding to the moister 1985-2004 period (y=0·7612x - 1·5543, R2=0·96). Neither WEPS nor RWEQ predicted the low amounts measured in CT and NT (3·86 kg m-1 on average) for storms lasting approximately 24 hours. High plant or residue soil coverage as well as high oriented surface roughness eliminated erosion according to WEPS and RWEQ. These results indicated that WEQ can be used as a reliable prediction model for long-term predictions of wind erosion in the semi-arid Pampas, even when run with limited available climatic data for this region.

Thermodynamics of non-reactive gases dissolved in water at ambient temperature (T≤333 K): an update Alvarez, Jorge L.; Fernandez Prini, Roberto The thermodynamics of dissolution of non-reactive gases in water under ambient conditions is of importance for the description of the properties of small hydrophobic solutes, and they are also of interest for environmental assessments. The review published in 1977 by Wilhelm, Battino and Wilcock (Chem. Rev. 77:219-262, 1977) constitutes a milestone in this field. However, a number of new data have been published since then, including both solubility and calorimetric determinations. We have analyzed the new data for 27 binary systems reported in the literature at the time of writing this article. Whenever solubility and calorimetric data both exist they have been fitted together. There are, however, systems for which only one type of new thermodynamic information is available; these systems were also analyzed using procedures that are described in this work.

Dissecting CNBP, a Zinc-Finger Protein Required for Neural Crest Development, in Its Structural and Functional Domains Armas, Pablo; Agüero, Tristán Horacio; Borgognone, Mariana; Aybar, Manuel Javier; Calcaterra, Nora Beatriz Cellular nucleic-acid-binding protein (CNBP) plays an essential role in forebrain and craniofacial development by controlling cell proliferation and survival to mediate neural crest expansion. CNBP binds to single-stranded nucleic acids and displays nucleic acid chaperone activity in vitro. The CNBP family shows a conserved modular organization of seven Zn knuckles and an arginine-glycine-glycine (RGG) box between the first and second Zn knuckles. The participation of these structural motifs in CNBP biochemical activities has still not been addressed. Here, we describe the generation of CNBP mutants that dissect the protein into regions with structurally and functionally distinct properties. Mutagenesis approaches were followed to generate: (i) an amino acid replacement that disrupted the fifth Zn knuckle; (ii) N-terminal deletions that removed the first Zn knuckle and the RGG box, or the RGG box alone; and (iii) a C-terminal deletion that eliminated the three last Zn knuckles. Mutant proteins were overexpressed in Escherichia coli, purified, and used to analyze their biochemical features in vitro, or overexpressed in Xenopus laevis embryos to study their function in vivo during neural crest cell development. We found that the Zn knuckles are required, but not individually essential, for CNBP biochemical activities, whereas the RGG box is essential for RNA-protein binding and nucleic acid chaperone activity. Removal of the RGG box allowed CNBP to preserve a weak single-stranded-DNA-binding capability. A mutant mimicking the natural N-terminal proteolytic CNBP form behaved as the RGG-deleted mutant. By gain-of-function and loss-of-function experiments in Xenopus embryos, we confirmed the participation of CNBP in neural crest development, and we demonstrated that the CNBP mutants lacking the N-terminal region or the RGG box alone may act as dominant negatives in vivo. Based on these data, we speculate about the existence of a specific proteolytic mechanism for the regulation of CNBP biochemical activities during neural crest development.

Influence of hydrothermal aging on the catalytic activity of sulfated zirconia Busto, Mariana; Shimizu, Kiyoyuki; Vera, Carlos Roman; Grau, Javier Mario; Pieck, Carlos Luis; D'amato, Miguel Angel; Causa, Maria Teresa Beatriz; Tovar, Manuel The use of reflux aged zirconia gel in the synthesis of sulfated zirconia catalysts for isomerization of short paraffins and isomerization-cracking of long paraffins was assessed. It was found that reflux aging greatly improved zirconia textural properties. The growth of the monoclinic phase was greatly suppressed and the initial area and sintering resistance were increased. The specific surface area of reflux aged material with no sulfate was almost 75 m2 g-1 after calcination at 800 °C. Sulfate promotion of aged materials further increased the tetragonal/monoclinic ratio and the area of sulfated catalysts was 220 m2 g-1 after calcination at 600 °C. Impregnation of reflux aged materials with sulfate produced materials which had very low activity in isomerization of n-butane. The effect of aging was explained in terms of a dissolution-precipitation process that eliminated specific sites of the gel that were responsible for much of the activity of the final catalyst. In the case of the hydroisomerization-cracking of long paraffins the effect was less deletereous partly due to the higher reactivity of this feedstock.

In vivo 5-flourouracil-induced apoptosis on murine thymocytes: Involvement of FAS, Bax and Caspase3 Aquino Esperanza, Jose A.; Aguirre, María Victoria; Aispuru, Gualberto R.; Lettieri, Carolina N.; Juaristi, Julian Antonio; Alvarez, Mirta Alba; Brandan, Nora Cristina Apoptosis is a highly regulated and programmed cell breakdown process characterized by numerous changes. It was reported as the major mechanism of anticancer drug-induced cells death. Unfortunately, many of these drugs are non-specific and cause severe side effects. The effects of 5-flourouracil (5-FU) on the apoptotic events in normal murine thymus were evaluated using an in vivo model. A single dose of 5-FU (150 mg/kg ip) was injected to CF-1 mice. A multiparametric analysis of thymic weight, cellularity, viability, architectural organization, apoptosis, DNA fragmentation, and the expression of several apoptotic proteins was evaluated in 10 days time-course study post-5-FU dosing. Total organ weights, thymocyte counts, and cell viabilities diminished drastically from the second day. The thymus architecture assessed through electron scanning microscopy revealed deep alterations and the lost of cell-cell contact between the first and the third days. DNA fragmentation and apoptotic indexes (May Grünwald Giemsa staining, double flourescent dyes, and TdT-mediated dUTP nick-end labeling assay) revealed that cell death was maximal on the second day (three times over control). Furthermore, the pro-apoptotic proteins FAS and Bax were strongly up-regulated during the first 2 days. The aforementioned morphological and biochemical changes were also accompanied within the same period by caspase 3 activation. This study revealed that in vivo apoptosis in normal thymus after 5-FU administration is related to FAS, Bax, and Caspase 3 co-expressions under the current experimental conditions, these findings, therefore, contribute to a new insight into the molecular mechanisms involved during 5-FU administration upon the thymus and the possible events committed in the lymphophenia associated with chemotherapy. © 2008 Springer Science+Business Media B.V.

Role of Polyphosphates in Microbial Adaptation to Extreme Environments Seufferheld, Manfredo Jose; Alvarez, Hector Manuel; Farias, Maria Eugenia Anthropomorphically, an extreme environment is one in which physical conditions are not conducive for human life. In this review, extreme environments are defined as habitats that experience steady or fluctuating exposure to one or more environmental factors, such as salinity, osmolarity, desiccation, UV radiation, barometric pressure, pH, and temperature. Microorganisms that colonize extreme environments are called extremophiles, and they are categorized into subgroups according to the specific environmental characteristics of their habitats (for a review, see reference 78).

Exact solutions for coupled free vibrations of tapered shear-flexible thin-walled composite beams Piovan, Marcelo Tulio; Filipich, Carlos Pedro; Cortínez, Víctor Hugo In this paper, analytical solutions for the free vibration analysis of tapered thin-walled laminated-composite beams with both closed and open cross-sections are developed. The present study is based on a recently developed model that incorporates in a full form the shear flexibility. The model considers shear flexibility due to bending as well as warping related to non-uniform torsion. The theory is briefly reviewed with the aim to present the equilibrium equations, the related boundary conditions and the constitutive equations. The stacking sequences in the panels of the cross-sections are selected in order to behave according to certain elastic coupling features. Typical laminations for a box-beam such as circumferentially uniform stiffness (CUS) or circumferentially asymmetric stiffness (CAS) configurations are adopted. For open cross-sections, special laminations behaving elastically like the CAS and CUS configurations of closed sections are also taken into account. The exact values (i.e. with arbitrary precision) of frequencies are obtained by means of a generalized power series methodology. A recurrence scheme is introduced with the aim to simplify the algebraic manipulation by shrinking the number of unknown variables. A parametric analysis for different taper ratios, slenderness ratios and stacking sequences is performed. Numerical examples are also carried out focusing attention in the validation of the present theory with respect to 2D FEM computational approaches, as well as to serve as quality test and convergence test of former finite elements schemes.

Oxygen cathode based on a layer-by-layer self-assembled laccase and osmium redox mediator Szamocki, R.; Flexer, Victoria; Levin, Laura Noemí; Forchiasin, F.; Calvo, Ernesto Julio Trametes trogii laccase has been studied as biocatalyst for the oxygen electro-reduction in three different systems: (i) soluble laccase was studied in solution; (ii) an enzyme monolayer was tethered to a gold surface by dithiobis N-succinimidyl propionate (DTSP), with a soluble osmium pyridine-bipyridine redox mediator in both cases. The third case (iii) consisted in the sequential immobilization of laccase and the osmium complex derivatized poly(allylamine) self-assembled layer-by-layer (LbL) on mercaptopropane sulfonate modified gold to produce an all integrated and
wired enzymatic oxygen cathode. The polycation was the same osmium complex covalently bound to poly-(ally-lamine) backbone (PAH-Os), the polyanion was the enzyme adsorbed from a solution of a suitable pH so that the protein carries a net negative charge. The adsorption of laccase was studied by monitoring the mass uptake with a quartz crystal microbalance and the oxygen reduction electrocatalysis was studied by linear scan voltammetry. While for the three cases, oxygen electrocatalysis mediated by the osmium complex was observed, for tethered laccase direct electron transfer in the absence of redox mediator was also apparent but no electrocatalysis for the oxygen reduction was recorded in the absence of mediator in solution. For the fully integrated LbL self-assembled laccase and redox mediator (case iii) a catalytic reduction of oxygen could be recorded a different oxygen partial pressures and different electrolyte pH. The tolerance of the reaction to methanol and chloride was also investigated.

Estanislao Zeballos y la segregación porteña de 1852 Sanchez, Santiago Javier Entre 1852 y 1861 el territorio argentino estuvo dividido en el Estado de Buenos Aires y la Confederación Argentina. Por entonces, la identidad nacional era aún débil. Cada provincia poseía su propia identidad local, y existía una rivalidad intensa entre Buenos Aires y el interior. Esto cambiaría a partir de 1861, con la creación de la República Argentina.

Ethos y discurso científico-académico: Los marcadores de evidencialidad como estrategia de cortesía Estrada, Andrea Maria Dentro de los estudios sobre la modalidad epistémica, existen numerosos trabajos sobre el discurso académico desde el fundacional de Chafe (1986) hasta los de Hyland (1998, 2000) referidos a la utilización de determinados recursos que aumentan la fuerza de las aserciones – intensificadores o boosters– y los que indican la falta de compromiso explícito o completo del autor respecto de la verdad de sus postulados, atenuadores o hedges (Hyland 1998). En este sentido, los recursos de evidencialidad resultan de vital importancia en el discurso académico, puesto que dan cuenta no solo del modo en que el investigador incorpora sus ideas a las ya existentes, sino que también le permiten anticiparse a las posibles objeciones de sus pares, persuadiéndolos de la corrección, originalidad y relevancia de su aporte. En este trabajo me propongo ejemplificar discurso académico escrito el modo en que los evidenciales encuentro (Estrada 2004 y 2005) y en todo caso (García Negroni 2002 y Estrada 2006) son utilizados en la construcción del ethos (Amossy 1999) discursivo: por un lado, como marca de postura epistemológica que atenúa o refuerza el grado de compromiso del locutor con respecto a la verdad de los enunciados y, por el otro, como estrategia de cortesía (Bravo 1999, 2001, 2002) mediante la cual el escritor de texto científico intenta obtener la anuencia de sus colegas y transformar su aporte en un hecho científico original.; Among the studies on epistemic modality, there is a great number of papers on academic discourse, from Chafe’s foundational one (1986) to those of Hyland’s (1998, 2000) dealing with the use of either certain resources that strenghten assertions –boosters–, or others that show the autor’s lack of explicit or full commitment towards the truth of his premises – hedges (Hyland, 1998). In this sense, evidentiality resources are vital to academic discourse, for they not only convey the way in which the researcher adds his own ideas to pre-existing ones, but they also allow him to anticipate possible objections made by his peers, persuading them about the rightfulness, originality and relevance of his contribution. In this paper, my aim is to explore academic discourse in order to provide examples of the way in which evidentiality resources encuentro (Estrada 2004 and 2005) and en todo caso (García Negroni 2002 and Estrada 2006) are used in the construction of discursive ethos (Amossy 1999). On the one hand, these evidentials act as a mark of epistemological stance that hedges or reinforces the degree on the speaker’s commitment regarding the truth of his utterances; on the other hand, as a courtesy strategy (Bravo 1999, 2001 y 2002) by which the author of a scientific text intends to seek his colleagues’ agreement, thus turning his contribution into an original scientific fact.

El cráneo más completo de Eurygenium latirostris Ameghino, 1895 (Mammalia, Notoungulata), un Notohippidae del Deseadense (Oligoceno tardío) de la Patagonia, Argentina Marani, Hernán Ariel; Dozo, Maria Teresa La familia Notohippidae Ameghino 1895 comprende a notoungulados que se registran desde el Eoceno Inferior (Bond y López, 1993) al Mioceno inferior de América del Sur (Reig, 1981; Cifelli, 1985, 1993; Bond, 1986; Shockey, 1999) y que a lo largo de su evolución desarrollaron formas con dentición hipsodonte, convergente con la de los équidos norteamericanos, por lo que se los considera como uno de los grupos de pastadores sudamericanos más antiguo (Bond, 1986).

Substitution of human for horse urine disproves an accusation of doping Diaz, Silvina; Kienast, Mariana Eva; Villegas Castagnasso, Egle Etel; Peña Malavera, Andrea Natalia; Manganare, Marcos Matías; Posik, Diego Manuel; Peral Garcia, Pilar; Giovambattista, Guillermo In order to detect switching and/or manipulation of samples, the owner of a stallion asked our lab to perform a DNA test on a positive doping urine sample. The objective was to compare the urine DNA profile versus blood and hair DNA profiles from the same stallion. At first, 10 microsatellite markers were investigated to determine the horse identity. No results were obtained when horse specific markers were typed in the urine sample. In order to confirm the species origin of this sample we analyzed the mitochondrial cytochrome b gene. This analysis from blood and hair samples produced reproducible and clear PCR-RFLP patterns and DNA sequence match with those expected for horse, while the urine sample results were coincident with human. These results allowed us to exclude the urine sample from the questioned stallion and determine its human species origin, confirming the manipulation of urine sample.