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Las células progenitoras son una población diversa caracterizada por mediar el recambio y renovación constante de los diferentes tejidos del cuerpo, de hecho han sido aisladas de diferentes compartimientos tisulares llamados nichos. Su estudio ha permitido entender su comportamiento e interrelación con los elementos de su entorno y eventos que controlan su capacidad de autorenovación, diferenciación y quiescencia; despertando el interés de muchos grupos de investigación a fin de proponer nuevas estrategias terapéuticas para el manejo de múltiples patologías crónicas. Pluripotent stem cells: characteristics and specialized compartments of residence Abstract Stem cells are a diverse population characterized to promote renewal of the different tissues; in fact they have been isolated from different compartments in the body named niches. Their study has allowed understanding their behavior and interaction with the elements of their environment and events that control self-renewal capacity, differentiation and quiescence, taken the interest of several research groups to propose new therapeutic strategies to management of chronic diseases.

The Enhanced Oil Recovery by Chemical methods (CEOR) is carried out through the injection of polymer and/or surfactant solutions. The polymer allows for the increase of the viscosity of the injected water, while the surfactant decreases the interfacial tension between water and crude-oil under reservoir conditions. However, the salinity of the oilfield water sources significantly reduces the ability of synthetic polymer to increase the viscosity and viscoelasticity of the water. Consequently, their use is limited, especially in those oilfields presenting high ionic strength brines. The rheological behavior of surfactant solutions could be considerably enhanced if formed micellar aggregates are in a sufficient number, adequate size, and the interactions among them are sufficiently strong. In this work, the effect of some inorganic salts on the rheological behavior of surfactant solutions in the absence of polymer molecules is studied. To our knowledge, this is the first time commonly anionic surfactants used in CEOR are tested using several cation valences inorganic salts. Results show a trend to increase or induce a shear-thinning behavior of sufficiently concentrated solutions. Solutions exhibiting higher viscosities profiles may display viscoelastic properties that resemble (or even overcome) those of polymeric solutions with similar viscosity profiles. This can be a very promising technique for oil recovery in the absence of traditional polymer molecules under high salinity conditions.

A stainless steel bioreactor was redesigned in order to facilite the production of microbial protein by solid-state fermentation. A double-helix stirrer was built to replace a blade-stirrer. Mixing time was set at 12 min every two hours. An air-manifold was built and installed at the bottom of the reactor. It allowed uniform bubbling in the water reservoir, providing a continuous flow of saturated air through the biomass. The intermittent mixing provided it a uniform substrate with minimun damage to the mycelial biomass. Along with the saturated air, allowed removal of the metabolic heat produced and prevented formation of dead zones in the biomass. A fermentation with Trichoderma reesei QM 9414 on water-treated sugar cane bagasse was carried out to test the operation of the bioreactor. The fermented product reached 7% crude protein at 48 h. A maximum of 10.96% was reached at 96h. This value was much higher than the laboratory value, confirming that the design allows a more efficient fermentation process.