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Objetivo: Determinar los niveles de altura y densidad osea alcanzada en alvéolos pos - texodoncia, 15 dias y tres meses despues de ser injertados con un sustituto óseo experimental. Materiales y Métodos: Se distribuyeron aleatoriamente 37 alvéolos postexodoncia en dos grupos, uno experimental (n=21) y otro control (n=16). En el grupo expe- rimental se utilizó un material compuesto por ß-Fosfato tricalcico y quitosano, en el grupo control se empleó un producto co- mercial compuesto por una mezcla bifásica de hidroxiapatita (HA) y fosfato tricalcico (TCP). Se realizaron tomografías a los 15 días y 3 meses postquirúrgicos determi - nando niveles óseos (altura y anchura en la zona injertada); también se determinó la densidad ósea utilizando unidades Houns- field. La información obtenida se procesó con la aplicación STATA versión 13. Se calcularon frecuencias para el sexo, tipo de alvéolo y tipo de injerto utilizado, y para las variables numéricas de edad, densidad ósea, altura ósea, grosor crestal, se establecieron promedios y desviación estándar. El nivel de confianza se estableció en 95% y el nivel de significancia en 5%. Resultados: Al comparar la densidad y altura ósea en los dos grupos no se encon- traron diferencias estadísticamente signifi - cativas, pero si al comparar el ancho en la zona de la cresta ( p <0.05). Conclusiones: El biocompuesto cerámico con quitosano mostró ser útil en preservar niveles óseos en los alvéolos postexodoncia y presentó diferencias estadísticamente significas en el ancho del reborde

Aim: Determine bone density and height reached fifteen (15) days and three (3) months after being grafted an sockets with a synthetic bone substitute and compared with experimental ceramic biocomposite. Materials and Methods: Thirty-seven sockets (37) selected randomly were gra - fted in clinics of the University of Valle, sixteen sockets (16) for control group and twenty (21) for the experimental group. CT scans were performed at 15 days and 3 months post-surgery determining bone levels: vertical height and width in the gra - fted area; bone density is also determined by analyzing Hounsfield units. The infor - mation obtained was processed with the STATA version 13 application frequencies for gender, type of socket and type of graft used, and for numeric variables of age, bone density, bone height, thickness crestal, averages were established and deviation were calculated standard. The confidence level was set at 95% and the significance level of 5%. Results: Bone density and height, no statis - tically significant differences between the intervention group (group 1) and control (group 2). For peak thickness statistically significant differences ( p <0.05). The va - riation or change between start and end of follow within each group found that there is no statistically significant difference. Conclusions: The ceramic biocomposite with chitosan and graft tricalcium phospha - te and hydroxyapatite no statistically significant differences in density and height in the scans at 15 and 90 days. The bone width showed statistically significant differences

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La agricultura es la base fundamental para la sostenibilidad de la seguridad alimentaria en el planeta, ya que representa la principal fuente de alimento y hace parte de la economía de los países en desarrollo. Sin embargo en la actualidad la demanda de alimento es mayor y existe la necesidad de agilizar el crecimiento vegetal para suplir las necesidades de la población y disminuir los índices de desnutrición y hambre, pero para ello se utilizan prácticas agrícolas como la aplicación de fertilizantes químicos que afectan significativamente el medio ambiente y los ecosistemas del suelo. En busca de encontrar soluciones, en los últimos años se han desarrollado estrategias alternativas para reemplazar los fertilizantes. Los microorganismos han demostrado cumplir funciones que mantienen el equilibrio del suelo y apoyan el crecimiento vegetal mediante diversos mecanismos, entre ellos la solubilización de fosfatos, por el cual se logra liberar el ion fosfato accesible para la planta. Este elemento se encuentra limitado en el suelo y es un nutriente vital después del nitrógeno para el desarrollo de la planta. El género Bacillus se ha destacado como un potencial solubilizador de fosfato y puede ser utilizado como biofertilizante que va a permitir obtener un producto agrícola de calidad y sin generar consecuencias al ambiente.

Agriculture is the fundamental basis for the sustainability of food security on the planet, since it represents the main source of food and is part of the economy of developing countries. At the present time, however, the demand for food is greater and there is the need to speed up plant growth to meet the needs of the population and to reduce rates of malnutrition and hunger, but this is used for agricultural practices as the application of chemical fertilizers which significantly affect the environment and the ecosystems of the soil. In hopes of finding solutions, alternative strategies to replace fertilizers have been developed in recent years. The microorganisms have demonstrated compliance functions that keep the balance of the soil and support plant growth through a variety of mechanisms, including the solubilization of phosphates, which can succeed in freeing the phosphate ion accessible for the plant. This item is limited in the soil and is a vital nutrient after the nitrogen for the growth of the plant. The genus Bacillus has been highlighted as a potential solubilizer phosphate and can be used as biofertilizer that will enable them to obtain a quality agricultural product, without generating consequences to the environment.

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Pseudomonas syringae pv. phaseolicola synthesizes a non-host-specific toxin, phaseolotoxin, and also synthesizes a phaseolotoxin-resistant ornithine carbamoyltransferase (ROCT) to protect itself from its own toxin. ROCT is encoded by argK, which is expressed coordinately with phaseolotoxin synthesis at 18 degrees C. To investigate the regulatory mechanisms of this system, null mutants were constructed for argK, argF (encoding the phaseolotoxin-sensitive OCTase [SOCT]), and amtA (encoding an amidinotransferase involved in phaseolotoxin synthesis). The argF mutant did not exhibit arginine auxotrophy when grown in M9 medium at 28 degrees C, because under this condition SOCT was replaced by ROCT. This loss of thermoregulation of argK was apparently caused by accumulation of carbamoylphosphate, one of the substrates of SOCT. Carbamoylphosphate, which has a structure similar to that of the inorganic moiety of phaseolotoxin, was used in induction assays with wild-type P. syringae pv. phaseolicola and was shown to be able to induce argK expression in M9 medium at 28 degrees C. These results indicate that argK expression is independent of temperature and is regulated directly by a compound resembling the inorganic moiety of phaseolotoxin.

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The formation of carbamyl phosphate (CAP) in dilute solutions of cyanate (NCO-) and orthophosphate (Pi) was measured both in the absence and in the presence of a precipitated matrix of calcium phosphate (Pi.Ca). The second-order rate constant and the free energy of CAP synthesis were not modified by the presence of the solid matrix, indicating that synthesis occurs in the homogeneous Pi-containing solution. The elimination reaction of CAP to form NCO- and Pi followed first-order kinetics and the rate constant was the same whether or not calcium phosphate was present. Elimination was not complete, and the steady level of remaining CAP was that expected from the free energy of synthesis. The formation of pyrophosphate (PPi) was detected in CAP-containing medium only in the presence of calcium, showing a close correlation with the amount of precipitated Pi.Ca. Phosphorolysis of CAP followed a sigmoidal time course, compatible with adsorption of CAP to the solid matrix as a prelude to transphosphorylation. Addition of 5'-AMP and of short linear polyphosphates inhibited phosphorolysis of CAP. It is proposed that the presence of a solid phosphate matrix and the relative concentrations of cyano compounds, as well as those of nucleotides and inorganic polyphosphates, could have played a crucial role in the conservation of chemical energy of CAP and in its use in prebiotic phosphorylation reactions.

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In this paper it is shown that the adsorption of 5'-adenosine monophosphate (5'-AMP) onto precipitated calcium phosphate exhibits a sigmoidal profile as revealed by isotherms at 45 degrees C. This result indicates a cooperative behavior in the adsorption of 5'-AMP. The relationship between adsorption capacity and surface area of the sedimented matrix may be interpreted as an indication that there is a monolayer of the absorbed nucleotide on the solid surface. The pH dependence of adsorption suggests that the negatively charged phosphoryl group of 5'-AMP interacts with a positively charged site (possibly Ca2+) on the matrix surface. The adsorption of the nucleotide is markedly decreased at pH values above 8.0. The Dixon-like plot of the effect of pH suggests an inhibitory role of hydroxyl ions in the adsorption of 5'-AMP. At pH 7.5, other anions such as pyrophosphate, tripolyphosphate and carbamyl phosphate also inhibit the adsorption of the nucleotide, probably by interacting with its adsorption site. We suggest that these phosphorylated molecules could have played a role in chemical evolution by modulating the amount of nucleotides adsorbed onto mineral surfaces. The significance of these phenomena in chemical evolution is discussed.

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