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Heterochromatin protein (HP)1γ is not only in the nucleus but also in the cytoplasm interacting with actin in both cell compartments

CONICET Digital - Mié, 31/01/2018 - 21:00

Heterochromatin protein (HP)1γ is not only in the nucleus but also in the cytoplasm interacting with actin in both cell compartments Charó, Nancy Lorena; Galigniana, Natalia Maricel; Piwien Pilipuk, Graciela Confocal and electron microscopy images, and WB analysis of cellular fractions revealed that HP1γ is in the nucleus but also in the cytoplasm of C2C12 myoblasts, myotubes, skeletal and cardiac muscles, N2a, HeLa and HEK293T cells. Signal specificity was tested with different antibodies and by HP1γ knockdown. Leptomycin B treatment of myoblasts increased nuclear HP1γ suggesting that its nuclear export is Crm-1-dependent. HP1γ exhibited a filamentous pattern of staining partially co-localizing with actin in the cytoplasm of myotubes and myofibrils. Immunoelectron microscopic analysis showed high-density immunogold particles that correspond to HP1γ localized to the Z-disk and A-band of the sarcomere of skeletal muscle. HP1γ partially co-localized with actin in C2C12 myotubes and murine myofibrils. Importantly, actin co-immunoprecipitated with HP1γ in the nuclear and cytosolic fractions of myoblasts. Actin co-immunoprecipitated with HP1γ in myoblasts incubated in the absence or presence of the actin depolymerizing agent cytochalasin D, suggesting that HP1γ may interact with G-and F-actin. In the cytoplasm, HP1γ was associated to the perinuclear actin cap that controls nuclear shape and position. In the nucleus, re-ChIP assays showed that HP1γ-actin associates to the promoter and transcribed regions of the house keeping gene GAPDH, suggesting that HP1γ may function as a scaffold protein for the recruitment of actin to control gene expression. When HP1γ was knocked-down, myoblasts were unable to differentiate or originated thin myotubes. In summary, HP1γ is present in the nucleus and the cytoplasm interacting with actin, a protein complex that may exert different functions depending on its subcellular localization.

Reciprocal interactions between a facilitator, natives, and exotics in tropical alpine plant communities

CONICET Digital - Mié, 31/01/2018 - 21:00

Reciprocal interactions between a facilitator, natives, and exotics in tropical alpine plant communities Llambí, Luis D.; Hupp, Nicole; Sáez, Agustín; Callaway, Ragan Facilitation by nurse plants has received considerable attention, but the feedback effects of beneficiaries on the benefactor fitness remain comparatively unexplored. In particular, to our knowledge there have been no studies of feedback effects of exotic species on nurse plants. Furthermore, there have been few studies of how exotic plants interact with native beneficiaries, potentially generating indirect effects on the nurse. Here, through spatial association analyses, we estimate the reciprocal interactions between the cushion nurse-plant Arenaria musciformis, native beneficiaries, and the dominant exotic Rumex acetosella (a fast growing heliophile species) in a tropical alpine ecosystem of the Venezuelan Andes, locally known as páramos. We recorded the density of natives and the exotic within Arenaria cushions and in paired open areas at three sites and calculated Relative Interaction Indices (RII) to explore the effects of the cushion. Then, we analyzed the feedback effects of Rumex and the natives on the density of flowers produced by Arenaria. Finally, we analyzed how Rumex abundance is related to the abundance of native species inside and outside cushions. RIIs indicated a facilitative effect of cushions on the abundance of native plants, but no effect on Rumex. We found a negative relationship between the density of natives and cushion flower density, but no such relationship for Rumex. However, at high densities, Rumex was negatively correlated with the abundance of the natives both inside and outside of cushions. Our results suggest the possibility of complex reciprocal interactions between nurses, natives and exotics, and that native and exotic plants can differ in their feedback effects on nurse cushions. Native plants appeared to be facilitated by cushions and then develop a parasitic relationship with their nurses. In contrast, the exotic Rumex had a neutral interaction with the nurse, but competitive effects on the native beneficiary community, which could indirectly modulate the feedback effects of natives on the nurse. These results highlight the importance of analyzing direct and indirect reciprocal interactions and the impacts of exotic invaders for understanding alpine community assembly.

Structural and electronic properties of Al-doped ZnO semiconductor nanopowders: Interplay between XRD and PALS experiments and first-principles/DFT modeling

CONICET Digital - Mié, 31/01/2018 - 21:00

Structural and electronic properties of Al-doped ZnO semiconductor nanopowders: Interplay between XRD and PALS experiments and first-principles/DFT modeling Damonte, Laura Cristina; Darriba, German Nicolas; Rentería, Mario A combined experimental and novel theoretical ab initio structural and electronic study was performed in order to characterize ZnO semiconductor nanopowders doped with Al atoms. For this, powder mixtures of ZnO and metallic Al in adequate proportions yielding different contents of Al (5, 10, and 30 at. %) were prepared by mechanical milling. The systems were characterized by X-ray diffraction and positron annihilation lifetime spectroscopy measurements. Additionally, combining two first-principles methods based on the Density Functional Theory (DFT) we calculated the final equilibrium structures for different concentrations of Al dopants and Zn vacancies in ZnO, predicting afterwards the characteristic positron annihilation lifetimes at these equilibrium structures. In addition to the structural relaxations, the ab initio predictions of the electronic properties in the studied systems help us to understand deeper the origin and characteristics of different positrons traps. This experimental and ab initio/DFT combined study allows to verify the dopant incorporation into the ZnO wurtzite structure and to extract the maximum information from the experimental data, giving an insight into the different defect complexes and their influence in the structural and electrical properties.

Pattern formation mechanisms in sphere-forming diblock copolymer thin films

CONICET Digital - Dom, 28/01/2018 - 21:00

Pattern formation mechanisms in sphere-forming diblock copolymer thin films Gomez, Leopoldo Raimundo; García, Nicolás A.; Register, Richard A.; Vega, Daniel Alberto The order–disorder transition of a sphere-forming block copolymer thin film was numerically stud-ied through a Cahn–Hilliard model. Simulations show that the fundamental mechanisms of patternformation are spinodal decomposition and nucleation and growth. The range of validity of each re-laxation process is controlled by the spinodal and order–disorder temperatures. The initial stagesof spinodal decomposition are well approximated by a linear analysis of the evolution equation ofthe system. In the metastable region, the critical size for nucleation diverges upon approaching theorder–disorder transition, and reduces to the size of a single domain as the spinodal is approached.Grain boundaries and topological defects inhibit the formation of superheated phases above the order–disorder temperature. The numerical results are in good qualitative agreement with experimental dataon sphere-forming diblock copolymer thin films.

Algal Community Structure of the Yalour Mausoleum, Cemetery of La Plata, Buenos Aires, Argentina

CONICET Digital - Dom, 28/01/2018 - 21:00

Algal Community Structure of the Yalour Mausoleum, Cemetery of La Plata, Buenos Aires, Argentina Gómez de Saravia, Sandra Gabriela; Rastelli, Silvia Elena; Lofeudo, Rosana; Rosato, Vilma Gabriela Biologicla communities that form biofilms on buildings and monuments can not only discolour the surface, but also produce physical and chemical alterations [1] Althought the type of organisms that colonize the facades of cement constructions is diverse, the analyzes carried out "In situ" reveal that algaeare one of the initial and main colonizers [2]. The algae cancause bichemical deterioration , since they produce, like fungi, metabolites of a predominantly organic nature. The Cemetery of La Plata, founded by Benoit in 1887, hsa inits interior mausoleums and notable monuments of various styles worthy of patrimonial protection. One of them is the Yalour mausoleum that is uniformly covered by a black patina, with conspicuous spots of lighter shade. Various chemicals with biocidal activity are commonly added to interior and exterior to provide protection of algal growth. In order to select compounds that prevent and control biofilm formation , it is necessary to know what organisms generate it, how they are structured and what physiologyical activity they present.For this reason,the aim of this work wsa to characterize, from hrbioloogicla point of view, the biofilm developed on the mausoleum.