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Wang X.,Center Hospitalier Of Luniversite Of Montreal Crchum Hopital Notre Dame | Wu T.,Center Hospitalier Of Luniversite Of Montreal Crchum Hopital Notre Dame | Wu T.,Zhejiang University | Hu Y.,Center Hospitalier Of Luniversite Of Montreal Crchum Hopital Notre Dame | And 6 more authors.

Pno1 is a protein that plays a role in proteasome and ribosome neogenesis in yeast. So far, its functions in mammalian cells have not been investigated. To understand its function in mammals, we performed in situ hybridization analysis of Pno1 expression in different development stages and generated Pno1 gene knockout (KO) and transgenic (Tg) mice lineages. The results showed early lethality of homozygous Pno1 KO lineage caused, as demonstrated in parallel by ex vivo experiments, by arrest of embryo development before compaction stage. Though, heterozygous (HET) mice with 50% of normal Pno1 mRNA concentration were fertile and showed no obvious anomalies. The lymphoid organs of HET mice were normal in size, weight and cellularity, with normal T and B cell subpopulations. TCR-triggered activation and proliferation of HET T cells were normal. Proteasome activities in HET organs were uncompromised. Tg mice with actin promoter-driven Pno1 expression were also fertile, with no apparent anomalies, although they expressed 2-5-fold higher Pno1 mRNA levels. The lymphoid organs of Tg mice were of normal size, weight and cellularity with normal T and B cell sub-populations. TCR-triggered activation and proliferation of Tg T cells were normal. Tg organs and tissues presented normal proteasome activity as did their wild type counterparts. Tagged Pno1 over-expression in L cells and density gradient fractionation established that Pno1 existed in large complexes with sedimentation rates between 20S and 26S, bigger than mature 26S proteasomes. Pno1 in fractions did not coincide with 40S or 60S ribosome subunits. Our study indicates that Pno1 is essential for cellular functions, but only a small percentage of its normal level is sufficient, and excessive amounts are neither harmful nor useful. The nature of the large complexes it associates with remains to be identified, but it is certain that they are not mature proteasomes or ribosomes. © 2012 Wang et al. Source

Gonzalez-Reyes L.,Institute Ciencia y Tecnologia del Distrito Federal | Gonzalez-Reyes L.,Metropolitan Autonomous University | Hernandez-Perez I.,Metropolitan Autonomous University | Diaz-Barriga Arceo L.,National Polytechnic Institute of Mexico | And 3 more authors.
Materials Science and Engineering B: Solid-State Materials for Advanced Technology

Anatase TiO2 nanocrystalline (6 nm) with BET specific surface area of 300 m2/g and direct bandgap of 3.31 eV were prepared sonochemically and then it was subjected to thermal treatment from 400 to 900 °C for 2 h, in order to produce variable anatase-rutile ratio. Three stages were considered in the samples thermally treated: (i) anatase grains coarsening as a result of heat treatment temperature increasing the structural homogeneity and crystallinity and both phenomena produce a reduction in the specific surface area, (ii) coexistence of two phases (anatase and rutile) separated by a transition region, called an interface, and (iii) process where the rutile grains evolve into a new equilibrium shape without the presence of anatase phase, minimizing the total surface and the grain boundary energies, by mass transport diffusion. In this last stage the rutile phase has the sole function of growth and densification. The structure evolution, morphology and microstructure characteristics were obtained by X-ray diffraction (XRD) and transmission electron microscopy (TEM). All the stages of phase transformation are subject to thermal effects that stem from the redistribution of energy in the system. The UV-vis absorption spectra show that direct and indirect transitions can take place in the same sample simultaneously. This is attributed to the combined effect of samples with variable anatase-rutile ratio and particle size effect. © 2010 Elsevier B.V. All rights reserved. Source

Hernandes-Alejandro M.,CINVESTAV | Calixto-Galvez M.,CINVESTAV | Lopez-Reyes I.,Institute Ciencia y Tecnologia del Distrito Federal | Salas-Casas A.,CINVESTAV | And 4 more authors.
Parasitology Research

It has been described that the pathogenicity of Entamoeba histolytica is influenced by environmental conditions and that transcription profile changes occur during invasion, suggesting that gene expression may be involved in the virulence of this parasite. However, the molecular mechanisms that are implicated in the control of gene expression in this microorganism are poorly understood. Here, we showed that the expression of the EhRabB protein, a small GTPase involved in phagocytosis, is modified through the interaction with red blood cells. By ELISA, Western blot, and immunofluorescence assays, we observed that the expression of EhRabB diminished after 5 min of the interaction of trophozoites with red blood cells, but protein level was recovered at subsequent times. In the EhRabB amino acid sequence, we found two lysine residues that could be target for ubiquitin modification and trigger the degradation of this GTPase at early times of phagocytosis. The analysis of the expression of the EhrabB mRNA showed that the interaction of trophozoites with red blood cells produces a drastic diminishing in its half-life. In addition, promoter assays using the chloramphenicol acetyltransferase reporter gene and electrophoretic mobility shift assays experiments showed that the URE1 motif located in the promoter region of EhrabB is involved in the expression regulation of this gene during phagocytosis. Moreover, the immunolocalization of the URE1-binding protein during phagocytosis indicated that the transcription of the EhrabB gene is determined, at least in part, by the translocation of this transcription factor to nuclei. These results suggested that the expression of particular genes of this parasite is controlled at several stages. © 2013 Springer-Verlag Berlin Heidelberg. Source

Carvajal-Gamez B.I.,Autonomous University of Mexico City | Arroyo R.,CINVESTAV | Camacho-Nuez M.,Autonomous University of Mexico City | Lira R.,Instituto Mexicano del Seguro Social IMSS | And 2 more authors.
Molecular and Biochemical Parasitology

Recently, we found that Trichomonas vaginalis contains a eukaryotic translation initiation factor 5A (TveIF-5A) with unknown function in this parasite. eIF-5A is the only cellular protein dependent of polyamines to form a hypusine residue, an unusual basic amino acid that is post-translationally formed by modification of a single specific lysine residue in an eIF-5A precursor protein. The purpose of this study was to determine the effect of a putrescine analogue, 1,4-diamino-2-butanone (DAB), on tveif-5a mRNA and TveIF-5A protein expression. TveIF-5A protein expression was reduced by inhibition of putrescine biosynthesis, and tveif-5a mRNA levels were reduced ∼90%, as shown by western blot and immunofluorescence assays. Cycloheximide treatment reduced the amount of mature TveIF-5A protein at 4 h and decreased the tveif-5a transcript level at 2 h, according to western blot, RT-PCR and qRT-PCR analyses. Actinomycin D treatment showed that the tveif-5a mRNA had half-life of ∼2.5 h in DAB-treated parasites. The half-life of tveif-5a mRNA was ∼4.5 h under exogenous putrescine conditions. These results suggest that putrescine is required for tveif-5a mRNA stability, and it is necessary for the expression, stability and maturation of TveIF-5A protein. © 2011 Elsevier B.V. All rights reserved. Source

Gonzalez-Reyes L.,Institute Ciencia y Tecnologia del Distrito Federal | Gonzalez-Reyes L.,Metropolitan Autonomous University | Hernandez-Perez I.,Metropolitan Autonomous University | Robles Hernandez F.C.,University of Houston
Chemical Engineering Science

In the present paper TiO2 (anatase) nanoparticles were synthesized by ultrasonic means proving the potential of this method. The synthesized anatase is heat treated at a temperature of 500°C in open air atmosphere to coarse it. The heat treatment times went from 1 to 72h, the temperature/time conditions were selected to prevent phase transformation and to solely coarsen anatase from 6.2 to 28.3nm. The synthesized and heat treated anatase were characterized using Electron Microscopy (Transmission and Scanning), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) method, UV-vis, Raman and Infrared spectroscopy. In the present paper are proposed two algorithms that are capable of determining the BET surface characteristics or the grain size based on the XRD or BET results, respectively. © 2010. Source

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