Expression of recombinant SnRK1 in E. coli. Characterization of adenine nucleotide binding to the SnRK1.1/AKINßγ-ß3 complex.

The SnRK1 complexes in plants belong to the family of AMPK/SNF1 kinases, which have been associated with the control of energy balance, in addition to being involved in the regulation of other aspects of plant growth and development. Analysis of complex formation indicates that increased activity is achieved when the catalytic subunit is phosphorylated and bound to regulatory subunits. SnRK1.1 subunit activity is higher than that of SnRK1.2, which also exhibits reduced activation due to the regulatory subunits. The catalytic phosphomimetic subunits (T175/176D) do not exhibit high activity levels, which indicate that the amino acid change does not produce the same effect as phosphorylation. Based on the mammalian AMPK X-ray structure, the plant SnRK1.1/AKINßγ-ß3 was modeled by homology modeling and Molecular Dynamics simulations (MD). The model predicted an intimate and extensive contact between a hydrophobic region of AKINßγ and the ß3 subunit. While the AKINßγ prediction retains the 4 CBS domain organization of the mammalian enzyme, significant differences are found in the putative nucleotide binding pockets. Docking and MD studies identified two sites between CBS 3 and 4 which may bind adenine nucleotides, but only one appears to be functional, as judging from the predicted binding energies. The recombinant AKINßγ-ßs complexes were found to bind adenine nucleotides with dissociation constant (Kd) in the range of the AMP low affinity site in AMPK. The saturation binding data was consistent with a one-site model, in agreement with the in silico calculations. As has been suggested previously, the effect of AMP was found to slow down dephosphorylation but did not influence activity.

Spatio-temporal dynamics of a cell signal pathway with negative feedbacks: the MAPK/ERK pathway.

We studied the spatio-temporal dynamics of a cell signal cascade with negative feedback that quantitatively emulates the regulative process that occurs in the Mitogen Activated Protein Kinase/Extracellular Regulated Kinase (MAPK/ERK) pathway. The model consists of a set of six coupled reaction-diffusion equations that describes the dynamics of the six-module pathway. In the basic module the active form of the protein transmits the signal to the next pathway's module. As suggested by experiments, the model considers that the fifth module's kinase down-regulates the first and third modules. The feedback parameter is defined as, µ(r)( j)= k(kin)5/k(kin)(j), (j = 1, 3). We analysed the pathway's dynamics for µ(r)( j) = 0.10, 1.0, and 10 in the kinetic regimes: i) saturation of both kinases and phosphatases, ii) saturation of the phosphatases and iii) saturation of the kinases. For a regulated pathway the Total Activated Protein Profiles (TAPPs) as a function of time develop a maximum during the transient stage in the three kinetic regimes. These maxima become higher and their positions shift to longer times downstream. This scenario also applies to the TAPP's regulatory kinase that sums up its inhibitory action to that of the phosphatases leading to a maximum. Nevertheless, when µ(r)(j)= 1.0 , the TAPPs develop two maxima, with the second maximum being almost imperceptible. These results are in qualitative agreement with experimental data obtained from NIH 3T3 mouse fibroblasts. In addition, analyses of the stationary states as a function of position indicate that in the kinetic regime i) which is of physiological interest, signal transduction occurs with a relatively large propagation length for the three values of the regulative parameter. However, for µ(r)(j)= 0.10 , the sixth module concentration profile is transmitted with approximately 45% of its full value. The results obtained for µ(r)(j) = 10 , indicate that the first five concentration profiles are small with a short propagation length; nonetheless, the last concentration profile, c6, attains more than 90% of its full value with a relatively large propagation length as an indication of signal transduction. Signal transduction also occurred favourably in the kinetic regimes ii) and iii), but the signal was longer-ranged in the regime ii).

Impact of energy intake, physical activity, and population-wide weight loss on cardiovascular disease and diabetes mortality in Cuba, 1980-2005.

Cuba's economic crisis of 1989-2000 resulted in reduced energy intake, increased physical activity, and sustained population-wide weight loss. The authors evaluated the possible association of these factors with mortality trends. Data on per capita daily energy intake, physical activity, weight loss, and smoking were systematically retrieved from national and local surveys. National vital statistics from 1980-2005 were used to assess trends in mortality from diabetes, coronary heart disease, stroke, cancer, and all causes. The crisis reduced per capita daily energy intake from 2,899 calories to 1,863 calories. During the crisis period, the proportion of physically active adults increased from 30% to 67%, and a 1.5-unit shift in the body mass index distribution was observed, along with a change in the distribution of body mass index categories. The prevalence of obesity declined from 14% to 7%, the prevalence of overweight increased 1%, and the prevalence of normal weight increased 4%. During 1997-2002, there were declines in deaths attributed to diabetes (51%), coronary heart disease (35%), stroke (20%), and all causes (18%). An outbreak of neuropathy and a modest increase in the all-cause death rate among the elderly were also observed. These results suggest that population-wide measures designed to reduce energy stores, without affecting nutritional sufficiency, may lead to declines in diabetes and cardiovascular disease prevalence and mortality.

Tratamiento químico de lodos catódicos producidos por Inti Raymi S.A. para la separación de oro y plata

Con el objetivo de disminuir costos en el proceso del tratamiento de lodos catodicos para la obtencion del dore, hasta la obtencion de oro y plata de calidad 90, la Empresa Minera Inti Raymi, finacio el presente proyecto para el estudio de un posible tratamiento quimico que podria implementarse para separar oro y plata de los lodos catodicos en la misma planta. Para esto, inicialmente, se realizaron pruebas de lixiviacion con acido sulfurico 2M, con el que se pudo extraer 62.8 de cobre, 75.7 de hierro, 54.8 de niquel y otras impurezas. Luego se realizaron pruebas de lixiviacion con soluciones de acido nitrico en el rango de concentraciones de 0.8M a 10M, de donde se establecio que las mejores extracciones se obtenian con 1.3M y 7.2M. Considerando estos resultados obtenidos se sometieron los lodos a un proceso de lixiviacion en tres etapas, la primera con acido sulfurico 2M, la segunda con acido nitrico 7.2M. Se obtuvo un lodo concentrado en oro con la siguiente composicion: Au=72.5, Ag=6.9, Cu=0.8 y otros=19, que luego de fundido dio dore de composicion Au=91.9,Ag=6.7 y otros=1.4 El porcentaje de recuperacion para el oro fue de 99.8. La Plata extraida se precipito con cloruro de sodio, se fundio con harina y se obtuvo fundido de plata de composicion: Ag=99.3 y otros=0.7, con 96 de recuperacion total.Para determinar si ademas del oro y la plata existian otros metales de interes,parte de la muestra de lodo utilizado para este trabajo se sometio a analisis por fluerescencia de rayos X, los resultados dieron que exsisten, al nivel de trazas, Ti, V, e Y.Se adecuaron y optimizaron metodos de analisis potenciometricos para oro y plata en lodos catodicos, los valores de las desviaciones estandar obtenidos fueron de 0.01 para el oro y 0.05 para la plata. Se realizo un diseño preliminar para la implementacion del proceso desarrollado, los resultados muestran que es posible ahorrar alrededor de 0.49 $us por onza bruta de oro.

Apendicitis neonatal perforada secundaria a enterocolitis necrosante / Perforated neonatal appendicitis secondary to necrotizing enterocolitis

La apendicitis aguda es una entidad rara en el recién nacido. Presentamos el caso de un recién nacido prematuro de 900g, cuya sintomatología inicial fue drenaje biliar por sonda orogástrica, distensión abdominal y plastrón en fosa iliaca derecha; se diagnosticó enterocolitis necrosante y se realizó laparotomía encontrando apéndice cecal perforado. En vista de que no hay un cuadro clínico específico y la mayor mortalidad ocurre en la apendicitis perforada la sospecha clínica y la intervención quirúrgica temprana es obligatoria