Effect of gallic acid and catechin on Lactobacillus hilgardii 5w growth and metabolism of organic compounds Alberto, Maria Rosa; Farias, Marta Elena; Manca, Maria Cristina The effects of different concentrations of (+)-catechin and gallic acid on the growth and metabolism of Lactobacillus hilgardii in different media were evaluated. These phenolic compounds at concentrations normally present in wine not only stimulated the growth rate but also resulted in greater cell densities during the stationary phase of growth in both media. During the first hours of growth both phenolic compounds activated the rate of glucose and fructose utilization and only catechin increased the malic acid consumption rate. Gallic acid and catechin were consumed from the beginning of L. hilgardii growth. All cited effects Were increased when the cells were precultivated in the presence of phenolic compounds, especially in the FT80 medium. As stimulating agents of L. hilgardii 5w growth, gallic acid and catechin could increase the risk of spoilage lactic acid bacteria in wine.

A method to obtain monosporic cultures of arbuscular mycorrhizal fungi Fracchia, Sebastian; Menendez, Ana Bernardina; Godeas, Alicia Margarita; Ocampo, J. A. We describe here a simple technique for obtaining monosporic cultures of AM fungi. Gigaspora rosea, Gi. sp., Glomus mosseae and G. sp. were used. One surface-sterilized spore was transferred to a 5-cm diameter Petri dish with 10 ml of 10 mM MES buffer, plus 0.04 g of Gel-Gro. The contents of a vermiculite-perlite (1/1, v/v) dish with 2-week-old clover seedlings were transferred onto the Gel-Gro medium with the germinated spore. All plants inoculated with single germinated spores developed mycorrhizas. With this system, non-destructive observation of development of hyphae, formation of fan-like structures, hyphal contact and penetration of AM fungi into the plant root was possible.

Temporal and spatial patterns of annelid populations in intertidal sediments of the Quequén Grande estuary (Argentina) López Gappa, Juan José; Tablado, Alejandro; Fonalleras, M.C.; Adami, Mariana Laura Temporal and spatial patterns of polychaete and oligochaete populations inhabiting intertidal sediments of the Quequén Grande estuary (Buenos Aires Province, Argentina) were analysed monthly during a yearly period. Local sediments are poorly selected, very fine sands, with a high percentage of mud. Two sites, located at both banks of the estuary were studied: (1) Site N, with a comparatively steep slope and percentage of mud increasing with sediment depth; (2) Site Q, with a gentle slope and percentage of mud increasing towards the sediment surface. The assemblage of annelids was characterised by a very low specific richness, being composed just by 4 species: The polychaetes Laeonereis acuta, Boccardiella ligerica and Capitella sp., and the tubificid oligochaete Ilyodrilus cf. frantzi. Density of the nereid L. acuta reached a peak in late summer and a minimum in spring. The population of Capitella sp. also showed maximum densities in summer, but collapsed during early fall, disappearing completely from the study area. Densities of I. cf. frantzi were highly variable in time and space. Three of the 4 species showed maximum densities at site Q, where mud content was highest at the sediment surface. At this sampling site, most of the L. acura population occurred within the upper 8 cm of the substrate. On the contrary, at site N, where mud and organic matter content increased with depth, this species was more abundant at subsurface layers (8-16 cm) than at the sediment surface.

An ab initio exploratory study of side chain conformations for selected backbone conformations of N-acetyl-L-glutamine-N-methylamide Tarditi, Ana Maria; Klipfel, Meghan W.; Rodriguez, Ana Maria; Suvire, Fernando Daniel; Chasse, Gregory A.; Farkas, Ödön; Perczel, AAndrás; Enriz, Ricardo Daniel The backbone potential energy surface (PES) (Ramachandran map) of N-acetyl-L-glutamine-N-methylamide has been studied at a,a side-chain orientation. Side-chain PESs at selected backbone conformations (γL and βL) were also studied. Side-chain-backbone interactions were analyzed in terms of energy and geometry.

Congenital goiter with hypothyroidism caused by a 5′ splice site mutation in the thyroglobulin gene Targovnik, Hector Manuel; Rivolta, Carina Marcela; Mendive, Fernando M.; Moya, Christian M.; Vono, Jussara; Medeiros Neto, Geraldo In this work we have extended our initial molecular studies of a consanguineous family with two affected goitrous siblings (H.S.N. and Ac.S.N.) with defective thyroglobulin (Tg) synthesis and secretion because of a homozygotic deletion of a fragment of 138 nucleotides (nt) in the central region of the Tg mRNA, identified previously in H.S.N. In order to identify the intron/exon boundaries and to analyze the regions responsible for pre-mRNA processing corresponding to a 138 nt deletion, we performed a screening of a human genomic library. The intron/exon junction sequences were determined from one positive clone by sequencing both strands of the DNA template. The results showed that the deletion mapped between positions 5549 and 5686 of the Tg mRNA and corresponded to exon 30. The positions of the exon limits differed by three nucleotides from the previously reported data obtained from direct sequencing of the deleted reverse transcriptase-polymerase chain reaction fragment from H.S.N. These variations are because the intron/exon junctions in this region were not available at the time when the deletion was first described. The deletion does not affect the reading frame of the resulting mRNA and is potentially fully translatable into a Tg polypeptide chain that is shortened by 46 residues. The same 138 nt deletion was observed in reverse transcriptase-polymerase chain reaction studies performed in the thyroid tissues from Ac.S.N. Genomic DNA analysis showed that a G to T transversion was observed at position +1 in the donor site of intron 30. Both affected patients (H.S.N. and Ac.S.N.) are homozygous for the mutation whereas the normal sister (At.S.N.) had a normal allele pattern. The functional consequences of the deletion are related to structural changes in the protein molecule that either could modify the normal routing of the translation product through the membrane system of the cell or could impair the coupling reaction. Probably the mutant Tg polypeptide might be functionally active in the production of thyroid hormone, because in the presence of a normal iodine ingestion (∼150 μg/day), Ac.S.N. was able to maintain normal serum levels of total triiodothyronine (T3) associated with relatively low serum total thyroxine (T4) with normal somatic development without signs of brain damage.

Curing of epoxy-urethane copolymers in a heated mold: Effect of the curing conditions on the phase-separation process Stefani, Pablo Marcelo; Moschiar, Stella Maris; Aranguren, Mirta Ines; Marieta, C.; Mondragon, I. The curing process of an epoxy-urethane copolymer in a heated mold was studied. The epoxy resin (DGEBA, Araldyt GY9527; Ciba Geigy), was coreacted with a urethane prepolymer (PU, Desmocap 12; Bayer) through an amine that acted as crosslinking agent (mixture of cycloaliphatic amines; Distraltec). The study focused on the effect of the curing condition and PU concentration on time-temperature profiles measured in the mold and the consequent final morphologies obtained. As the PU concentration increases, the maximum temperature reached in the mold decreases as a result of the dilution effect of the elastomer on reaction heat, whereas the Tg of the piece also decreases. Phase separation is a function of conversion and temperature reached in the curing part and was analyzed using experimental data and a mathematical model that predicts temperature and conversion throughout the thickness of the mold. Scanning electron microscopy and atomic force microscopy were used to determine the characteristics of the dispersed phase for the different formulations and conditions of curing. It was shown that the size of the dispersed phase increased with the initial PU concentration, whereas there were practically no differences in the separated phase as a function of position or temperature of curing (in the range of 70 to 100°C studied). The superposition of the phase diagrams with the conversion-temperature trajectories during cure provided an explanation of the morphologies generated.

Static and dynamic analyses of anisotropic plates with corner points Grossi, Ricardo Oscar; Lebedev, L. The present paper also deals with the application of the Ritz method to the determination of the natural frequencies of a rectangular anisotropic plate with a free corner formed by the intersection of two free edges. The resulting algorithm permits the analysis of anisotropic, orthotropic and isotropic materials. Accurate values can be obtained by incrementing the number of orthogonal polynomials, and the entire algorithm can be implemented on a personal computer. The software constitutes a useful tool in design work because of the great number of vibrating anisotropic plate problems that can be solved.

Varying c and particle horizons Chimento, Luis Pascual; Jakubi, Alejandro S.; Pavón, Diego We explore what restrictions may impose the second law of thermodynamics on varying speed of light theories. We find that the attractor scenario solving the flatness problem is consistent with the generalized second law at late time.

A variability analysis of low-latitude unidentified gamma-ray sources Torres, Diego F.; Romero, Gustavo Esteban; Combi, Jorge Ariel; Benaglia, Paula; Andernach, H.; Punsly, Brian We present a study of 40 low-latitude unidentified 3EG gamma-ray sources which were found to be not positionally coincident with any known class of potential gamma-ray emitters in the Galaxy (Romero et al. 1999). We have performed a variability analysis which reveals that many of these 40 sources are variable. These sources have, in addition, a steep mean value of the gamma-ray spectral index, < Γ > = 2.41 ± 0.2, which, combined with the high level of variability, seems to rule out a pulsar origin. The positional coincidences with uncatalogued candidates to supernova remnants were also studied. Only 7 sources in the sample are spatially coincident with these candidates, a result that is shown to be consistent with the expected level of pure chance association. A complementary search for weak radio counterparts was also conducted and the results are presented as an extensive table containing all significant point-like radio sources within the 40 EGRET fields. We argue that in order to produce the high variability, steep gamma-ray spectra, and absence of strong radio counterparts observed in some of the gamma-ray sources of our sample, a new class of objects should be postulated, and we analyze a viable candidate

Deficiencia de hierro en mujeres embarazadas y sus recién nacidos Buys, Maria Celia; Guerra, Lidia Noemi; Martin, Beatriz Lilia; Torrejón, Irma del Rosario; Miranda, Carmen E.; Sodero, Susana Introducción. La anemia ferropénica en embarazadas es frecuente y hemoglobinas (Hb) menores de 11 g%, se diagnostican como anemia. Indicadores como: ferritina sérica (Ferr) y saturación de transferrina (Sat%) miden reservas de hierro. Objetivos. Detectar anemia o deficiencia de hierro en embarazadas y recién nacidos (RN), correlacionar sus reservas de hierro, con el propósito de un oportuno diagnóstico y suplementación. Población. Se estudiaron 52 embarazadas normales de término y sus recién nacidos. Material y métodos. Se analizaron: hemoglobina (Hb), hierro sérico (Fe) y capacidad total de transporte de hierro por la transferrina (TIBC) por métodos colorimétricos y ferritina (Ferr) analizada por radioinmunoensayo (IRMA). El porcentaje de saturación surge de la relación Fe/TIBC. Se diagnosticó como anemia (valor ajustado a 1.200 m sobre el nivel del mar): Hb< 12,2 g% en madres y Hb< 16,8 g% en neonatos. Para el hierro, los puntos de corte fueron: para saturación<15% y Ferr< 15 ng/ml. Se denominó “deficiencia severa de hierro”, cuando Sat% y Ferr estaban por debajo del punto de corte y “deficiencia moderada”, al valor de Ferr< 15 o Sat%< 15. Resultados. El 67% de las madres tenía anemia: 57% deficiencia severa, 29% deficiencia moderada y 14%, no ferropénica. Del 33% de madres no anémicas, 24% tenían deficiencia severa (anemia latente) y 76%, deficiencia moderada. El 46% de neonatos tenía anemia. La deficiencia de hierro fue moderada: 4% en anémicos y 11% en no anémicos. Conclusiones. La anemia en embarazadas estudiadas es frecuente (67%), presentando el 14% de ellas anemia no ferropénica. El 100% de madres no anémicas presentaba deficiencia de hierro. El 46% de los neonatos tenía anemia pero sus reservas de hierro eran adecuadas en la mayoría.; Introduction. Ferropenic anemia with hemoglobin values below 11 g% is frequently found during pregnancy. Iron storage was measured by means of indicators such as serum ferritin and transferrin saturation. Objective. Early anemia detection and/or iron deficiency in pregnant women and their newborns. Correlation between iron storage in both, leading to early diagnosis and prevention. Material & methods. Hemoglobin (Hb), serum iron (Fe), and total iron binding capacity (TIBC) were determined by the colorimetric method. The saturation percentage was obtained through the relationship between Fe/TIBC. Ferritin (Ferr) was measured with an immunoradiometric assay (IRMA). Cut-offs for abnormal values of hemoglobin (adjusted to 1.200 m above sea level) were <12.2 g% for the mothers and <16.8% for the newborns. Cut-offs for ferritin values were 15 ng/ml and 15% for transferrin saturation values. Anemia was severe when both of these parameters of iron status were below normality and moderate when only one of them was below normal. Results. Anemic values were present in 67% of mothers. Fifty seven percent of them were severe, whereas 29% were moderate. In 14% the anemia was non-iron related. In the non anemic group (47%), 24% had a severe iron deficiency (latent anemia) and in 76% it was moderate. Forty seven per cent of the newborn were anemic. The iron deficiency was moderate in 4% of the anemic children, and in 11% of the non-anemic ones. Conclusion. An anemic condition was found in 67% of the pregnant women included in this study. Only in 14% the anemia was not related to a ferropenic condition. All the non-anemic mothers proved to be iron deficient. Forty six per cent of the neonates had anemia though their Fe reserves were adequate in most of them.

Electrical conductances of Tetrabutylammonium and Decamethylferrocenium Hexafluorophosphate in organic solvents Goldfarb, Darío L.; Longinotti, María Paula; Corti, Horacio Roberto The electrical conductances of tetrabutylammonium hexafluorophosphate in acetone and of decamethylferrocenium hexafluorophosphate in acetone, acetonitrile 1,2-dichloroethane, and dichloromethane have been measured at 25°C. The Walden product of the Bu4N+ cation and the PF-6 anion in acetone and other solvents is discussed in relation to the dielectric friction. The electric conductance at infinite dilution and the association constant of decamethylferrocenium hexafluorophosphate were determined in the four solvents investigated. The association constant of this electrolyte increases with decreasing reduced temperature, as expected in the framework of the association theory, within the primitive model of electrolytes.

Normal spatial learning and improved spatial working memory in mice (mus musculus) lacking dopamine d4 receptors Falzone, Tomas Luis; Avale, Maria Elena; Gelman, Diego Matias; Rubinstein, Marcelo Dopamine terminals in the hippocampus and prefrontal cortex modulate cognitive processes such as spatial learning and working memory. Because dopamine D4 receptors are expressed in these brain areas we have analyzed mutant mice lacking this receptor subtype (Drd4-/-). Wild-type and Drd4-/- mice were challenged in two spatial learning paradigms: the Morris water maze and an alternation T-maze. Drd4-/- mice showed normal place learning ability to find a hidden platform based on spatial extra-maze cues. In addition, Drd4-/- mice were able to find a new platform location with the same learning plasticity as wild type-mice. Spatial working memory assessed on a T maze showed that Drd4-/- mice were more efficient than wild-type mice in acquiring the maximum plateau of correct alternation scores. These results provide further evidence that the functional consequence of lacking D4 receptors is more evident in behaviors dependent on the integrity of the prefrontal cortex.

Peptide and protein folding Chasse, Gregory Adam; Rodriguez, Ana Maria; Mak, Melody L.; Deretey, E.; Perczel, András; Sosa, Carlos P.; Enriz, Ricardo Daniel; Csizmadia, Imre Gyula Ab initio peptide folding, and its role in the reductionistic approach towards the understanding of protein folding are discussed from the points of view of past, present and possible future developments. It is believed that after the initial holistic approach, we are now at a new epoch, which will be dominated by reductionism. New quantitative mathematical models will be the result of the reductionistic approach that will lead toward a new, more sophisticated holistic era.

Morphometric diversity of the pulmonate limpet Siphonaria lessoni in different coastal environments Tablado, Alejandro; López Gappa, Juan José Siphonaria lessoni (Blainville, 1824) is the most abundant marine gastropod in the rocky intertidal zone of Buenos Aires Province, Argentina. The morphology of this species was studied in 6 sites near the city of Quequén, differing in intertidal height and degree of exposure to wave action and pollution. Shell length, width, height, and the distance from apex to posterior shell margin were measured, as well as the dry weight of both the shell and limpet body. A data matrix of 600 individuals (100 limpets per site) by 6 variables was analyzed by Principal Component Analysis (PCA) and Discriminant Analysis (DA) in order to compare size and shape differences among sites. As expected, axis I of the PCA explained a very high percentage (87.7%) of total variance, and can be interpreted as a size factor. Axis II, which summarised 6.9 %, may be regarded as expressing shell shape. Limpets not exposed to wave action within Quequén Harbour showed the highest values in all variables, whereas individuals living within the Brachidontes rodriguezi (d'Orbigny, 1846) community were very small and highly variable. Limpets heavily exposed to sewage at mid intertidal levels had a subcentral shell apex and were relatively very low. Classification of individuals by DA showed that the most characteristic morphology corresponded to limpets living at mid intertidal level close to a sewage outfall, or within Quequén Harbour (94 and 97 % correct reallocations, respectively). The influence of different physical and biotic factors on the morphology of Siphonaria lessoni is discussed.

Simulation of granular compacts in two dimensions Vidales, Ana Maria; Kenkre, Vasudev M.; Hurd, Elizabeth A. Simulations of granular packings in 2-D by throwing disks in a rectangular die are performed. Different size distributions as bimodal, uniform and gaussian are used. Once the array of particles is done, a relaxation process is carried on using a large-amplitude, low-frequency vertical shaking. This relaxation is performed a number N of times. Then, we measure the density of the package, contact distribution, coordination number distribution, entropy and also the disks size distribution vs. height. The dependence of all these magnitudes on the number N of "shakings" used to relax the packing and on the size distribution parameters are explored and discussed.

The D2 receptor is critical in mediating opiate motivation only in opiate-dependent and withdrawn mice Dockstader, Colleen L.; Rubinstein, Marcelo; Grandy, David K.; Low, Malcolm J.; Van Kooy, Derek Der According to the dual systems model for opiate reward, dopamine mediates opiate motivation when an animal is in a deprived motivational state (i.e. opiate-dependent and in withdrawal) and not when an animal is in a nondeprived state (i.e. previously drug-naive). To determine the role of the D2 dopamine receptor subtype in mediating opiate motivation, we examined the behaviour of N5 congenic D2 receptor knockout mice and their wild-type siblings in opiate-naive and opiate-dependent and withdrawn place conditioning paradigms. Opiate-naive D2 receptor knockout mice demonstrated acquisition of morphine-conditioned place preference but failed to acquire place preference when conditioned in the deprived state. We propose that D2 receptor function is critical in mediating the motivational effects of opiates only when the animal is in an opiate-dependent and withdrawn motivational state. These findings also underscore the important influence of the genetic background to a given phenotype, as evidenced by the observation that increasing the allelic contribution from the 129/SvJ strain abolishes morphine place preference in C57BL/6 wild-type mice.

Curing kinetics of epoxy-urethane copolymers Stefani, Pablo Marcelo; Moschiar, Stella Maris; Aranguren, Mirta Ines The cure of the epoxy resin diglycidyl ether of bisphenol A (Araldyt GY9527) with a mixture of cycloaliphatic amines (Distraltec) was studied, and the focus was on the effect of the copolymerization with a commercial polyurethane (PU) elastomer (Desmocap 12). A simplified phenomenological model was proposed to represent the copolymerization reaction. It considered the effect of the temperature and the concentration of the elastomer on the reaction rate, and it was simple enough to be included in models of processing conditions. A nonlinear regression analysis of the experimental conversion data obtained from differential scanning calorimetry was utilized to find the best fitting parameters to Kamal's equation for the chemically controlled part of the reaction (short times) under isothermal and constant heating-rate conditions. The Rabinowitch approach together with the Addam–Gibbs theory was utilized to introduce the effect of diffusion control at the end of the reaction on the overall constant for the reaction rate. The Di Benedetto equation was used to predict the conversion at which vitrification takes place for each run. Experimental results for conversions higher than this critical conversion were utilized to obtain information about the diffusion kinetic constant using a nonlinear regression analysis as previously. The overall model obtained was used to calculate a calorimetric conversion and reaction rate as functions of time, which was in excellent agreement with the experimental results. The addition of PU elastomers affected the values of the activation energies of the chemically and diffusion controlled parts of the reaction, as well as the final conversion reached by the epoxy–amine system. The proposed model allowed prediction of all the observed features using parameters that were independent of the temperature of the curing reaction.

Perfect fluid cosmologies with varying light speed Chimento, Luis Pascual; Jakubi, Alejandro S. We have found exact constant solutions for the cosmological density parameter using a generalization of general relativity that incorporates a cosmic time-variation of the velocity of light in vacuum and the Newtonian gravitation constant. We have determined the conditions when these solutions are attractors for an expanding universe and solved the problems of the Standard Big Bang model for perfect fluids.

Protective role of medroxyprogesterone acetate on N-methyl-N-nitrosourea-induced lymphomas in BALB/c female mice Pazos, Patricia; Lanari, Claudia Lee Malvina; Molinolo, Alfredo In a previous paper we reported the occurrence of a high incidence of lymphomas in N-methyl-N-nitrosourea (MNU)-treated mice, in the course of an experiment of combined chemical-hormonal carcinogenesis in mammary gland, in which we used medroxyprogesterone acetate (MPA) and MNU in different treatment protocols. In this report we have analyzed the action of MPA in the leukemogenic effects of MNU, by specifically selecting for the analysis experimental groups in which only few mammary carcinomas had developed. A high incidence of lymphomas (65%, median latency: 176 days) was registered in MNU-treated mice, and the administration of MPA was associated with a significant reduction in the incidence of lymphomas (P<0.001) in all protocols.

Determination of the pore size distribution of correlated mesoporous networks López, Raúl Horacio; Vidales, Ana Maria; Zgrablich, Giorgio In the present work we study how the adsorption desorption hysteresis loop of a mesoporous disordered medium represented by a 3-dimensional Dual Site-Bond Model (DSBM) is affected by percolation. Site and bond distributions are assumed to be gaussians. The behavior of the threshold pressure for the evaporation processe suggests a method to determine the site and bond distributions from experimental adsorption-desorption hysteresis curves. Traditional methods developed for non-correlated networks are tested and evaluated against our simulation results showing the discrepancy mainly for highly correlated networks. Results of the prediction capability of our method are shown.