Caracterización fenotípica y genotípica de la resistencia a imipenem en Pseudomonas aeruginosa aisladas en un hospital de Buenos Aires; Phenotypic and genotypic characterization of imipenem-resistant Pseudomonas aeruginosa isolated in Buenos Aires Cejas, Daniela; Almuzara, Marisa; Santella, Gisela Natalia; Tuduri, A.; Palombarani, Susana; Figueroa, S.; Gutkind, Gabriel Osvaldo; Radice, Marcela Alejandra En el presente estudio, que tuvo por objeto analizar los mecanismos involucrados en la resistencia a carbapenemes, se incluyeron 129 aislamientos de Pseudomonas aeruginosa recuperados durante el año 2006 en el Hospital “Eva Perón” de la Provincia de Buenos Aires. La caracterización fenotípica y genotípica de la resistencia permitió reconocer la presencia de metalo-β-lactamasas (MBL) en el 14% de esos aislamientos. En todos ellos se identificó la presencia de la enzima IMP-13; sin embargo, algunos aislamientos resultaron sensibles a carbapenemes de acuerdo con los puntos de corte establecidos por el CLSI e incluso con las sugerencias de la Subcomisión de Antimicrobianos de SADEBAC, AAM. El ensayo de detección fenotípica de MBL de sinergia con doble disco resultó útil en este estudio. Sólo aquellos aislamientos productores de IMP-13 que a su vez presentaron alteraciones en las proteínas de membrana externa resultaron completamente resistentes a imipenem. Los aislamientos productores de MBL correspondieron a varios tipos clonales, lo cual sugiere no sólo la diseminación de una cepa resistente, sino también la diseminación horizontal de este mecanismo de resistencia entre clones diferentes.; From 129 P. aeruginosa isolated at a health care centre located in Buenos Aires (Hospital “Eva Perón”), 14% produced IMP-13. Although 18 isolates were metallo-β-lactamases (MBL) producers, only those isolates that displayed altered outer membrane protein profiles correlated with the resistant category according to CLSI or even Subcomisión de Antimicrobianos, SADEBAC, AAM. Phenotypic screening of metallo-β-lactamases proved to be appropriate for detecting MBL producing isolates. IMP-13 producing isolates corresponded to at least five different clonal types, which not only suggests the dissemination of the resistant strain but also of the resistant marker.

Impacto del alumbrado público en la atracción de insectos en áreas subtropicales Mattivi, María de Los Rosarios; Cabello, Alberto José; Kirschbaum, Carlos Federico Este trabajo es una extensión, en cuanto a resultados se refiere, del artículo publicado en la Revista Luminotecnia nº83 “El Alumbrado Público y la Polución Lumínica en un Poblado Rural”. A partir de experimentos en desarrollo, se infiere el impacto ambiental de la Polución Lumínica por parte del Alumbrado Público en la población de insectos en ciudades y zonas rurales situadas en una región de clima subtropical. Se busca cuantificar los efectos en la atracción de insectos por parte de los distintos tipos de lámparas de uso frecuente en alumbrado Público.

Parasites of the Brazilian sandperch Pinguipes brasilianus Cuvier: A tool for stock discrimination in the Argentine Sea Timi, Juan Tomas; Lanfranchi, Ana Laura; Etchegoin, Jorge Alejandro; Cremonte, Florencia The use of parasites as biological tags allowed the identification of three stocks of Brazilian sandperch Pinguipes brasilianus in the Argentine Sea. A total of 156 specimens caught during spring 2006, off the coasts of Buenos Aires Province (38°27′ S; 57°90′ W, n = 54), San Matías Gulf (42°S; 65°10′ W, n = 52) and Nuevo Gulf (42°09′ S; 64°05′ W, n = 50), were examined for parasites and 21 species were found, including monogeneans, digeneans, cestodes, nematodes, acanthocephalans and crustaceans. Diet analyses showed that Brazilian sandperch feed mainly on benthic macroinvertebrates, with differences in relative importance of main items between zones. Univariate analysis on parasite population descriptors, as well as a discriminant analysis, allowed the identification of discrete stocks in each zone, although a higher degree of similarity was observed between both Patagonian Gulfs. Northern samples were characterized by higher values of prevalence and abundance of Grillotia sp., Corynosoma australe and Scolex polymorphus. On the other hand, Trifur tortuosus and Opecoelidae gen. sp. were important in determining the position of Patagonian samples and were specially related to those from Nuevo Gulf, whereas none of the species was clearly related only to fish from San Matías Gulf. The size of the hosts is likely to influence the similarity among zones, with larger fish as better tools to discriminate stocks, probably because they harbour 'mature' assemblages shaped longer by differential environmental conditions and diet in each zone. Parasite species characteristic of sandperch from Buenos Aires Province, which display very low specificity among fish species in this area, have been previously identified as biological tags for other host species in these region, confirming their value as tags for stock delineation.

Palaeosalinity variations in the Early Cretaceous of the Neuquén Basin, Argentina: Evidence from oxygen isotopes and palaeoecological analysis Lazo, Dario Gustavo; Aguirre-Urreta, Maria Beatriz; Price, Gregory D.; Rawson, Peter F.; Ruffell, Alastair H.; Ogle, N. The Neuquén Basin is a stratigraphically- and economically-important Early Cretaceous depocentre located in west-central Argentina. The Early Valanginian to Early Barremian succession (upper Vaca Muerta, Mulichinco and Agrio Formations) contains a rich fossil record, with abundant bivalves and ammonoids. Palaeosalinities are determined systematically throughout the succession, based on an oxygen isotope analysis of unaltered oyster shells from two localities in Neuquén province. A total of 188 oyster samples from 52 stratigraphic levels were processed. A total of 52 mean values of δ18O isotope are used to calculate palaeosalinities, assuming an estimated water temperature of 25 °C. The observed range of palaeosalinities, between the maximum and the minimum, is 19, which is in conflict with published accounts of this being a fully marine succession. The isotopic data are combined with independent faunal evidence to evaluate palaeosalinity variation both laterally and temporally. Significant fluctuations in water salinity are indicated, with a clear tendency to increase from brachyhaline to euhaline and near hyperhaline conditions through time. The fluctuations were probably due to dilution from normal marine water, caused primarily by variations in rainfall and continental runoff. In addition, the presence of a volcanic island arc along the western margin of the basin may have at least partially isolated the basin from the marine waters of the Pacific Ocean. Also, a gulf-shaped basin may have inhibited hydrodynamic exchange with the ocean while enhancing retention of continental waters.

Determination of Size Distributions of Concentrated Polymer Particles Embedded in a Solid Polymer Matrix Soulé, Ezequiel Rodolfo; Elicabe, Guillermo Enrique In this work we present the results obtained from the size characterization of polymer particles embedded in a solid polymer matrix using Static Light Scattering (SLS) and Scanning Electron Microscopy (SEM). The analyzed samples are the result of the solution polymerization of isobornyl methacrylate (IBoMA) in polyisobutylene (PIB) at complete conversion. Induced by polymerization, the system undergoes phase separation. As a result, spherical micron sized particles rich in PIB are formed. At the end of the polymerization, the particles become trapped in a solid polymer matrix rich in Poly‐IBoMA. Size, concentration, and refractive index, make the resulting particle system scatter light under the Rayleigh‐Debye‐Gans (RDG) regime with interparticle interference. For Light Scattering (LS) characterization the samples are measured with a Flat Cell Static Light Scattering (FCSLS) apparatus, in which the reaction takes place. The resulting SLS spectra are analyzed using the Percus‐Yevick approximation to model the interference effects. The local monodisperse approximation is used to consider polydispersity in the particle sizes. The estimated particle size distributions agree well with the measurements from SEM. In this work a concentrated particle system that naturally scatters light according to the RDG regime has been fully characterized in terms of its particle size distribution. This work, against the opinion of other authors, shows the feasibility of measuring still particles using a one dimensional array of light detectors.

Controlling the N - And S -representability of the second-order reduced density matrix: The doublet-state case Alcoba, Diego Ricardo; Valdemoro, C; Tel, L. M.; Perez Romero, E. A purification procedure that simultaneously corrects the N - and S -representability main defects of a second-order reduced density matrix (2RDM), second-order hole reduced density matrix (2HRDM), and second-order G matrix is presented here. In this purifying procedure, the generalized unitarily invariant second-order matrix decomposition for the 2RDM and the 2HRDM as well as for the G matrix is combined with the S -representability conditions. In particular, here we will focus our attention on the RDMs corresponding to doublet states. We will thus explicitly give the S -representability conditions that a two-body correlation matrix has to satisfy when an N -electron system is in a doublet spin-state in the spin-component of maximum projection. Furthermore, as a consequence of the G -matrix spin properties (which directly affect the S -representability of the 2RDM), we show that a different contracting form for the 2RDM is possible. The numerical results presented in this work confirm the efficiency of our purifying procedure. © 2008 The American Physical Society.

Correlation between thermal parameters, structures, dendritic spacing and corrosion behavior of Zn-Al alloys with columnar to equiaxed transition Ares, Alicia Esther; Gassa, Liliana Mabel; Gueijman, Sergio Fabian; Schvezov, Carlos Enrique The columnar to equiaxed transition (CET) has been examined for many years and the significance of CET has been treated in several articles. Experimental observations in different alloy systems have shown that the position of the transition is dependent on parameters like cooling rate, velocity of the liquidus and solidus fronts, local solidification time, temperature gradients and recalescence. The dendritic structure in alloys results in microsegregation of solute species which affects significantly the mechanical properties of the material. The main parameters characterizing the microstructure and the length range of microsegregation is the spacing which is classified as primary, secondary and tertiary. Properties like mechanical resistance and ductility are influenced by the dimensions and continuity of the primary branches, while the secondary and tertiary branches permit the isolation of interdendritic phases which can deteriorate the mechanical behavior of the material. Since the morphology and dimensions of the dendritic structure is related to the solidification parameters mentioned above, for each type of alloy it is essential to correlate dimensions and solidification conditions in order to control the structure. The objective of the present research consists on studying the influence of solidification thermal parameters with the type of structure (columnar, equiaxial or with the CET); and with grain size and dendritic spacing (primary and secondary) in Zn-Al (ZA) alloys (Zn-4 wt%Al, Zn-16 wt%Al and Zn-27 wt%Al, weight percent). Also, correlate the thermal parameters, type of structure, grain size and dendritic spacing with the corrosion resistance of these alloys. © 2007 Elsevier B.V. All rights reserved.

Novel aromatic ring-hydroxylating dioxygenase genes from coastal marine sediments of Patagonia Lozada, Mariana; Riva Mercadal, Juan Pablo; Guerrero, Leandro Demián; Di Marzio, Walter Dario; Ferrero, Marcela Alejandra; Dionisi, Hebe Monica Polycyclic aromatic hydrocarbons (PAHs), widespread pollutants in the marine environment, can produce adverse effects in marine organisms and can be transferred to humans through seafood. Our knowledge of PAH-degrading bacterial populations in the marine environment is still very limited, and mainly originates from studies of cultured bacteria. In this work, genes coding catabolic enzymes from PAH-biodegradation pathways were characterized in coastal sediments of Patagonia with different levels of PAH contamination.Genes encoding for the catalytic alpha subunit of aromatic ring-hydroxylating dioxygenases (ARHDs) were amplified from intertidal sediment samples using two different primer sets. Products were cloned and screened by restriction fragment length polymorphism analysis. Clones representing each restriction pattern were selected in each library for sequencing. A total of 500 clones were screened in 9 gene libraries, and 193 clones were sequenced. Libraries contained one to five different ARHD gene types, and this number was correlated with the number of PAHs found in the samples above the quantification limit (r = 0.834, p < 0.05). Overall, eight different ARHD gene types were detected in the sediments. In five of them, their deduced amino acid sequences formed deeply rooted branches with previously described ARHD peptide sequences, exhibiting less than 70% identity to them. They contain consensus sequences of the Rieske type [2Fe-2S] cluster binding site, suggesting that these gene fragments encode for ARHDs. On the other hand, three gene types were closely related to previously described ARHDs: archetypical nahAc-like genes, phnAc-like genes as identified in Alcaligenes faecalis AFK2, and phnA1-like genes from marine PAH-degraders from the genus Cycloclasticus.Conclusion: These results show the presence of hitherto unidentified ARHD genes in this sub-Antarctic marine environment exposed to anthropogenic contamination. This information can be used to study the geographical distribution and ecological significance of bacterial populations carrying these genes, and to design molecular assays to monitor the progress and effectiveness of remediation technologies.

Aspectos gramaticales del español (morfosintácticos y léxico-semánticos) en la formación del traductor Albano, Hilda Rosa; Giammatteo, Graciela Mabel En este trabajo se parte del debate acerca de la pertinencia de las cuestiones gramaticales en la formación del traductor y se defiende una posición que sostiene que el aprendizaje de la gramática del español es esencial para lograr que el trabajo del traductor resulte plenamente eficaz. Asimismo se propone un enfoque léxico-sintáctico de la gramática, que se ejemplifica con un aspecto central nuclear: la incidencia del verbo en la organización sintáctico-semántica de la oración y en la selección de los modificadores que lo acompañan.

Short-time transport properties in dense suspensions: From neutral to charge-stabilized colloidal spheres Banchio, Adolfo Javier; Nägele, Gerhard We present a detailed study of short-time dynamic properties in concentrated suspensions ofcharge-stabilized and of neutral colloidal spheres. The particles in many of these systems are subjectto significant many-body hydrodynamic interactions. A recently developed accelerated Stokesiandynamics (ASD) simulation method is used to calculate hydrodynamic functions,wave-number-dependent collective diffusion coefficients, self-diffusion and sedimentationcoefficients, and high-frequency limiting viscosities. The dynamic properties are discussed independence on the particle concentration and salt content. Our ASD simulation results are comparedwith existing theoretical predictions, notably those of the renormalized density fluctuation expansionmethod of Beenakker and Mazur [Physica A 126, 349 (1984)], and earlier simulation data on hardspheres. The range of applicability and the accuracy of various theoretical expressions for short-timeproperties are explored through comparison with the simulation data. We analyze, in particular, thevalidity of generalized Stokes?Einstein relations relating short-time diffusion properties to thehigh-frequency limiting viscosity, and we point to the distinctly different behavior of de-ionizedcharge-stabilized systems in comparison to hard spheres.

Une nouvelle espèce du genre Neostenotus d'Argentine (Heteroptera, Miridae, Mirini) Chérot, Frédéric; Carpintero, Diego Leonardo Une nouvelle espèce, Neostenotus querandi n. sp., est décrite de Buenos-Aires, Argentine.

Heat shock factor 1 represses estrogen-dependent transcription through association with MTA1 Khaleque, M. A.; Bharti, A.; Gong, J.; Gray, P. J.; Sachdev, V.; Ciocca, Daniel Ramon; Stati, Arturo Oscar; Fanelli, Mariel Andrea; Calderwood, S. K. Heat shock factor 1 (HSF1), the transcriptional activator of the heat shock genes, is increasingly implicated in cancer. We have shown that HSF1 binds to the corepressor metastasis-associated protein 1 (MTA1) in vitro and in human breast carcinoma samples. HSF1-MTA1 complex formation was strongly induced by the transforming ligand heregulin and complexes incorporated a number of additional proteins including histone deacetylases (HDAC1 and 2) and Mi2α, all components of the NuRD corepressor complex. These complexes were induced to assemble on the chromatin of MCF7 breast carcinoma cells and associated with the promoters of estrogen-responsive genes. Such HSF1 complexes participate in repression of estrogen-dependent transcription in breast carcinoma cells treated with heregulin and this effect was inhibited by MTA1 knockdown. Repression of estrogen-dependent transcription may contribute to the role of HSF1 in cancer.

Residue decomposition and fate of nitrogen-15 in a wheat crop under different previous crops and tillage systems Alvarez, Carina Rosa; Alvarez, Roberto; Sarquis, Alejandra Nitrogen (N) management may be improved by a thorough understanding of the nutrient dynamics during previous-crop residue decomposition and its impact on fertilizer N fate in the soil-plant system. An experiment was conducted in the Argentine Pampas to evaluate the effect of maize and soybean as previouscrops and plow-till and no-till methods on N dynamics and 15N-labeled fertilizer uptake during a wheat growing season. Maize and soybean residues released N under both tillage treatments, but N release was faster from soybean residues and when residues were buried by tillage. Net immobilization of N on decomposing residues was not detected. A regression model that accounted for 92% of remaining N variability included time, previous crop, and tillage treatment as independent variables. The rapid residue decomposition with N release was attributed to the high temperatures of the agroecosystem. The recovery of 15N-labeled fertilizer in the wheat crop, soil organic matter, and decomposing residues was not statistically different between previous crop treatments or tillage systems. Crop uptake of fertilizer N averaged 52% across treatments. Forty percent of fertilizer N was removed in grains. Immobilization of labeled N on soil organic matter was substantial, averaging 34% of the 15N-labeled fertilizer retained, but was very small on decomposing residues, averaging 0.2-3.0%. Fertilizer N not accounted for at harvest in the soil-plant system was 12% and was ascribed to losses. Previous crop or tillage system had no impact on wheat yield, but when soybean was the previous crop, N content of grain and straw+roots increased. Discussion is presented on the potential availability of N retained in wheat straw, roots, and soil organic matter for future crops.

Accumulation and Elimination of Cr in Gills and Eggs by the freshwater crab Zilchiopsis collastinensis after experimental exposure Gagneten, Ana María; Imof, Alba; Gervasio, Susana Graciela Cr accumulation and elimination were studied in the freshwater crab Zilchiopsis collastinensis (Crustacea, Decapoda) exposed to 3 (T1) and 6 (T2) mg CrVI/L using 1000-L tanks with dechlorinated water and artificial sediment. The objectives of this study were to analyze the Cr-accumulating capacity of Z. collastinensis males and females in gills and eggs, as well as to relate this capacity with crab weight, and to determine the Bioconcentration Factor (BCF) in relation to water and sediment. Significant differences in Cr concentration were found between the control and T1 and T2 (p = 0.018 and p = 0.001), and between T1 and T2 (p = 0.025). Significant differences in Cr concentration were found among all treatments in gills (p < 0.0001) and eggs (p = 0.0247), and when comparing Cr concentration between gills and eggs (p= 0.0046), but not between females and males (p = 0.6035). The tissues/water and tissues/sediment BCF values increased with Cr concentration, but was always higher in relation to water than to sediment. No relationship was found between crab weight and Cr concentration (r = -0.025). The obtained results constitute a great contribution to the knowledge of Cr accumulation in freshwater crabs. We propose Z. collastinensis as biomonitor of aquatic systems contaminated with Cr.

Notas sobre los colectivos artísticos en América Latina: años 70 y 80 Longoni, Ana En esta apretada síntesis señalo algunas modalidades que adoptó la acción colectiva en el arte latinoamericano y distintos modos en que fue pensada su politicidad, siempre vinculada a estrategias de intervención en el espacio público. Podría remitirme a una profusa tradición de colectivos artísticos en Latinoamérica, remontándome a principios del siglo XX a los primeros agrupamientos fuertemente imbricados con proyectos políticos de corte emancipador, particularmente el movimiento anarquista. Es en la larga década de los sesenta, época en la que se entrecruzan horizontes de transformación de signo revolucionario o modernizador, cuando la idea del trabajo de creación y actuación colectiva se inscribe en una plataforma radicalmente alternativa de articulación del arte y la política. Entonces eclosionaron en varios países del continente potentes movimientos que irrumpieron en la escena artística implicando un quiebre definitivo con las concepciones instituidas del arte, el artista y el público. En muchas de sus manifestaciones es radicalmente puesta en cuestión la noción de autoría individual, asumiendo una firma colectiva e incluso promoviendo al espectador como activo partícipe del acto creador. Es en la larga década de los sesenta, época en la que se entrecruzan horizontes de transformación de signo revolucionario o modernizador, cuando la idea del trabajo de creación y actuación colectiva se inscribe en una plataforma radicalmente alternativa de articulación del arte y la política. Entonces eclosionaron en varios países del continente potentes movimientos que irrumpieron en la escena artística implicando un quiebre definitivo con las concepciones instituidas del arte, el artista y el público. En muchas de sus manifestaciones es radicalmente puesta en cuestión la noción de autoría individual, asumiendo una firma colectiva e incluso promoviendo al espectador como activo partícipe del acto creador.

Bioevaluation of 32P patch designed for the treatment of skin diseases Salgueiro, María Jimena; Duran, Hebe Alicia; Palmieri, Mónica Alejandra; Pirchio, Rosana; Medina, Vanina Araceli; Ughetti, Ricardo; Croci, Máximo; Nicolini, Jorge; Zubillaga, Marcela Beatriz Objective: The objective of this study was to design and evaluate a 32P patch for the treatment of skin diseases. Materials and Methods: The patch was prepared from chromic phosphate 32P and silicone. Bioelimination and biodistribution in healthy and treated animals, and the therapeutic efficacy of two treatment schemes (single dose and fractionated dose) in an animal model of skin cancer were studied. Results: Based on the bioelimination and biodistribution studies, no leakage of 32P from the patch was observed. The treated tumors reduced their mean diameter compared to controls. The single-dose therapeutic scheme showed a higher number of complete and partial remissions compared to the fractionated scheme. These results were confirmed by histopathological analysis of the samples. Conclusion: The 32P patch was designed and produced according to specifications for the treatment of superficial lesions of the skin. Although the 32P patch is an open source, it behaves like a sealed one for use in brachytherapy treatments.

Polygalacturonase activity and expression of related genes during ripening of strawberry cultivars with contrasting fruit firmness Villarreal, Natalia Marina; Rosli, Hernan Guillermo; Martinez, Gustavo Adolfo; Civello, Pedro Marcos Fleshy fruits soften during ripening mainly as a consequence of the catabolism of cell wall components. In strawberry (Fragaria × ananassa Duch), the depolymerization and solubilization of pectins increase during ripening and contribute to fruit softening. In the present paper, we report the cloning and expression analysis of two polygalacturonase (PG) putative cDNAs: FaPG1 and T-PG. The former seems to be the same sequence of previously reported PG in strawberry, while T-PG cDNA has a deletion of 85 bp that cause a frame shift and would produce an inactive protein. Measurement of total PG activity and expression of FaPG1 and T-PG were performed in strawberry cultivars with contrasting softening rates. The softest cultivar (Toyonaka) showed the higher total PG activity in all ripening stages analyzed. The analysis by RT-PCR revealed that both genes express in the three cultivars, though the expression pattern was different. In the firmer cultivars (Selva and Camarosa) the expression of T-PG was considerably higher than the expression of FaPG1, while the opposite occurred in the softest cultivar (Toyonaka). Therefore, the higher PG activity detected in Toyonaka correlates with the enhanced expression of FaPG1 gene, while the low PG activity found in the firm cultivars correlates with a higher expression of T-PG, a gene that could encode a truncated protein without PG activity. The influence of auxins on both the expression of PG genes and the total PG activity during strawberry fruit ripening was also analyzed.

Differential structure of the Thompson components of selfadjoint operators Fongi, Guillermina; Maestripieri, Alejandra Laura Different equivalence relations are defined in the set L(H)s of self- adjoint operators of a Hilbert space H in order to extend a very well known relation in the cone of positive operators. As in the positive case, for a G L(H)s the equivalence class Ca admits a differential structure, which is compatible with a complete metric defined on Ca. This metric coincides with the Thompson metric when a is positive.

Southern Hemisphere Early Cretaceous (Valanginian-Early Barremian) carbon and oxygen isotope curves from the Neuquén Basin, Argentina Aguirre-Urreta, Maria Beatriz; Price, Gregory D.; Ruffell, Alastair H.; Lazo, Dario Gustavo; Kalin, Robert M.; Ogle, Neil; Rawson, Peter F. The first carbon and oxygen isotope curves for the Valanginian to Early Barremian (Early Cretaceous) interval obtained from outcrops in the Southern Hemisphere are presented. They were obtained from well-dated (by ammonites) sediments from the Neuquén Basin, Argentina. Measurements were acquired by the innovative method of analysing fossil oyster laminae. The occurrence of the well-established mid-Valanginian positive carbon isotope excursion is documented, while less well-marked positive events may also correlate with peaks identified in the well-known successions of SE France. The mid-Valanginian positive carbon isotope event in the Neuquén Basin is possibly associated with organic-rich sediments. A similar relationship is seen in the European Alps and in oceanic cores in some areas of the world.

Functional entry of dengue virus into Aedes albopictus mosquito cells is dependent on clathrin-mediated endocytosis Acosta, Eliana Gisela; Castilla, Viviana; Damonte, Elsa Beatriz Entry of dengue virus 2 (DENV-2) into Aedes albopictus mosquito C6/36 cells was analysed using biochemical and molecular inhibitors, together with confocal and electron microscopy observations. Treatment with monodansylcadaverine, chlorpromazine, sucrose and ammonium chloride inhibited DENV-2 virus yield and protein expression, whereas nystatin, a blocker of caveolae-mediated endocytosis, did not have any effect. Using confocal microscopy, co-localization of DENV-2 E glycoprotein and the marker protein transferrin was observed at the periphery of the cytoplasm. To support the requirement of clathrin function for DENV-2 entry, overexpression of a dominant-negative mutant of Eps15 in C6/36 cells was shown to impair virus entry. The disruption of actin microfilaments by cytochalasin D also significantly affected DENV-2 replication. In contrast, microtubule disruption by colchicine treatment did not impair DENV-2 infectivity, suggesting that DENV-2 does not require transport from early to late endosomes for successful infection of mosquito cells. Furthermore, using transmission electron microscopy, DENV-2 particles of approximately 44-52 nm were found attached within electron-dense invaginations of the plasma membrane and in coated vesicles that resembled those of clathrin-coated pits and vesicles, respectively. Together, these results demonstrate for the first time that DENV-2 enters insect cells by receptor-mediated, clathrin-dependent endocytosis, requiring traffic through an acidic pH compartment for subsequent uncoating and completion of a productive infection.