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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 | Year: 2010

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.


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.
PLoS ONE | Year: 2012

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.


Banuelos C.,National Polytechnic Institute of Mexico | Banuelos C.,Institute Ciencia y Tecnologia Del Distrito Federal | Garcia-Rivera G.,National Polytechnic Institute of Mexico | Lopez-Reyes I.,Institute Ciencia y Tecnologia Del Distrito Federal | And 6 more authors.
Journal of Biomedicine and Biotechnology | Year: 2012

EhADH112 is an Entamoeba histolytica Bro1 domain-containing protein, structurally related to mammalian ALIX and yeast BRO1, both involved in the Endosomal Sorting Complexes Required for Transport (ESCRT)-mediated multivesicular bodies (MVB) biogenesis. Here, we investigated an alternative role for EhADH112 in the MVB protein trafficking pathway by overexpressing 166 amino acids of its N-terminal Bro1 domain in trophozoites. Trophozoites displayed diminished phagocytosis rates and accumulated exogenous Bro1 at cytoplasmic vesicles which aggregated into aberrant complexes at late stages of phagocytosis, probably preventing EhADH112 function. Additionally, the existence of a putative E. histolytica ESCRT-III subunit (EhVps32) presumably interacting with EhADH112, led us to perform pull-down experiments with GST-EhVps32 and [ 35S]-labeled EhADH112 or EhADH112 derivatives, confirming EhVps32 binding to EhADH112 through its Bro1 domain. Our overall results define EhADH112 as a novel member of ESCRT-accessory proteins transiently present at cellular surface and endosomal compartments, probably contributing to MVB formation during phagocytosis. Copyright 2012 Cecilia Bauelos et al.


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 | Year: 2011

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.


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 | Year: 2011

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.


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 | Year: 2013

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.


Gonzalez-Reyes L.,Institute Ciencia y Tecnologia Del Distrito Federal | Gonzalez-Reyes L.,Metropolitan Autonomous University | Hernandez-Perez I.,Institute Ciencia y Tecnologia Del Distrito Federal | Diaz-Barriga Arceo L.,Metropolitan Autonomous University | Manzo-Robledo A.,National Polytechnic Institute of Mexico
Materials Science Forum | Year: 2011

Nanocristalline TiO2 obtained by a facile and environment-friendly sonochemical method was subjected to thermal treatment in the temperature range of 400-900 °C in order to produce variable anatase-rutile phases ratio. The relationship between the optical bandgap and the electrochemical behavior was studied. All the stages of phase transformation of the as-prepared sample such as: nucleation, growth and coarsening were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that phase transformation mechanism stems from the redistribution of energy in the system and a critical particle size. On the other hand, the samples were characterized by UV-vis spectroscopy for the bandgap studies. The optical band gap of as-prepared sample increases to 3.31 eV with respect to 3.20 eV for bulk-anatase. This expansion could be attributed to quantum size effect. The i-E characteristics of samples with variable anatase-rutile ratio were obtained using cyclic voltammetry technique in a 0.5 M H2SO4 solution at room temperature. The foremost charge magnitude was obtained when anatase had a critical size of 17 nm. Analyzing both particle size for anatase and rutile, we observed that when rutile is the dominating phase and its size difference larger in 35% than anatase, the current reaches its minimum values. Based on electrochemical results, the optimal particle size and content phases control are important in order to obtain an increase in the electrochemical performance in the Hydrogen Evolution Reaction (HER) zone. © (2011) Trans Tech Publications, Switzerland.


Calixto-Galvez M.,CINVESTAV | Romero-Diaz M.,CINVESTAV | Romero-Diaz M.,Institute Ciencia y Tecnologia del Distrito Federal | Garcia-Munoz A.,CINVESTAV | And 5 more authors.
International Journal for Parasitology | Year: 2011

Transcription initiation is the most regulated stage for the control of gene expression. This event requires that a complex of proteins called transcription factors bind to DNA through cis-regulatory elements located in the gene promoters. However, little is known about transcription regulation in Entamoeba histolytica, the protozoan parasite responsible for human amoebiasis. Some genes encoding for proteins involved in the parasite pathogenicity contain specific upstream regulatory elements (URE1-URE5) in their promoters. Here, we identified the protein that specifically binds to the URE1 sequence (EhURE1BP). This protein contains five SNase domains and one Tudor motif, and has 21% identity and 36% similarity to the multifunctional eukaryotic protein known as the protein containing Tudor and staphyloccocal nuclease-like domains (TSN). To obtain antibodies against EhURE1BP, the recombinant protein was expressed and immunised in rabbits. Western blot and immunofluorescence assays showed that EhURE1BP is located in both nuclei and cytoplasm. Electrophoretic mobility shift assays and supershift assays demonstrated that EhURE1PB specifically binds to URE1 and that the C-terminus that includes the Tudor motif contains the DNA-binding domain of this protein. Results suggest that this TSN-like protein is the transcription factor that activates the transcription of some pathogenicity-related genes of E. histolytica. © 2011.


PubMed | Institute Ciencia y Tecnologia del Distrito Federal
Type: | Journal: Neuroscience | Year: 2012

Recent studies suggest that the main olfactory bulb (OB) represents a functional circadian pacemaker. In many altricial mammals, during pre-visual stages of development the olfactory system plays a vital role in their survival. One remarkable example is the European rabbit; the newborns are normally raised in a dark nursery burrow, and the lactating female briefly visits her young approximately once every 24 h. Under these conditions, newborn rabbits depend on the circadian system to anticipate the arrival of the lactating doe as well as on pheromonal cues on the mothers ventrum to locate nipples and suckle efficiently. To investigate the development of the rabbits circadian system, we characterized the 24-h pattern of expression of clock genes in the OB and suprachiasmatic nucleus (SCN) of pre-visual week-old rabbits and compared this with the pattern of expression in visual juvenile rabbits several weeks after weaning. We report for the first time that Per1, Cry1, and Bmal1 are expressed in the OB of newborn and juvenile rabbits. In addition, the diurnal pattern of clock gene expression develops earlier in the OB than in the SCN of newborn rabbits. Given the early maturation of the molecular clockwork and the biological relevance of this structure during development, it is possible that the OB plays an important role in temporal regulation during pre-visual life in rabbits.

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