Relación entre el nivel de grasa e ingestión y la excreción urinaria de nitrógeno y energía, en gazapos en crecimiento-cebo

Se determinó la excreción urinaria de nitrógeno (NU, %) y de energía (EU, kcal/100g), en la última semana de vida, de 36 conejos alimentados, desde el destete (a los 28 d) hasta el sacrificio a los dos meses de edad, con tres piensos conteniendo 0, 3 y 6 % de grasa añadida (G0, G3 y G6); y administrados a dos niveles de ingestión: ad libitum (IL) y restringido (IR) al 70 % de IL. El NU y la EU estuvieron influidos positivamente tanto por el nivel de ingestión (P<0,001) como por el % de grasa ingerida (P<0,05). En estos resultados puede estar involucrado el metabolismo tan elevado de las lipoproteínas transportadoras de lípidos, implicadas en el metabolismo de las grasas, ya sean de origen alimentario o de la lipogénesis de novo. La relación entre la EU y el NU aporta valores muy superiores a los que podría corresponder a las materias orgánicas nitrogenadas, por lo que se podría pensar, como posible causa, en la intervención de materia orgánica no nitrogenada. Asimismo, la cuantificación de la EM del pienso se ve afectada por el incremento del valor calórico de la orina, con el nivel de ingestión y/o el 6 % de grasa añadida. Con ello se evidencia la desigualdad entre ED y EM de la grasa en las raciones que las incluya. Asimismo, el hecho de que la movilización grasa —bien sea de origen alimentario o de la lipogénesis— altere la excreción nitrogenada y/o energética a través de la orina, pone de manifiesto la importancia de su consideración, especialmente cuando dicha pérdida puede afectar a los rendimientos de algunas producciones animales.Energy (EU, kcal/100g) and nitrogen (NU, %) urinary excretion were determined, during the week prior to slaughter, in an experiment carried out with 36 rabbits fed from weaning (28 d of age) to two months of age. Three diets were utilized consisting of: 0 %, 3 % and 6 % fat (G0, G3 and G6); and two levels of intake: ad libitum (IL) and restricted to 70 % of IL (IR). Both NU and EU were incremented by level of feed intake (P < 0.001) and fat level (P < 0.05) in the diet. These increment can be explained by the high metabolism of the remnant lipoprotein particles lipids transporters implied in the metabolism of the fats. The relationship between the EU and the NU contributes with high values to those that it could correspond to the nitrogen organic matters (NOM), that would be thought as a possible cause to the intervention of non NOM. Likewise, dietary metabolizable energy (ME) was affected by the increased caloric content in the urine, in the fattening diets, mainly in the IL. Fat metabolism affected urinary excretion of N, thus suggesting that when fat is added to the diet, this effect should be taken into consideration

Impact of receptor clustering on ligand binding

<p>Abstract</p> <p>Background</p> <p>Cellular response to changes in the concentration of different chemical species in the extracellular medium is induced by ligand binding to dedicated transmembrane receptors. Receptor density, distribution, and clustering may be key spatial features that influence effective and proper physical and biochemical cellular responses to many regulatory signals. Classical equations describing this kind of binding kinetics assume the distributions of interacting species to be homogeneous, neglecting by doing so the impact of clustering. As there is experimental evidence that receptors tend to group in clusters inside membrane domains, we investigated the effects of receptor clustering on cellular receptor ligand binding.</p> <p>Results</p> <p>We implemented a model of receptor binding using a Monte-Carlo algorithm to simulate ligand diffusion and binding. In some simple cases, analytic solutions for binding equilibrium of ligand on clusters of receptors are provided, and supported by simulation results. Our simulations show that the so-called "apparent" affinity of the ligand for the receptor decreases with clustering although the microscopic affinity remains constant.</p> <p>Conclusions</p> <p>Changing membrane receptors clustering could be a simple mechanism that allows cells to change and adapt its affinity/sensitivity toward a given stimulus.</p

Cholesterol Depletion in Adipocytes Causes Caveolae Collapse Concomitant with Proteosomal Degradation of Cavin-2 in a Switch-Like Fashion

Caveolae, little caves of cell surfaces, are enriched in cholesterol, a certain level of which is required for their structural integrity. Here we show in adipocytes that cavin-2, a peripheral membrane protein and one of 3 cavin isoforms present in caveolae from non-muscle tissue, is degraded upon cholesterol depletion in a rapid fashion resulting in collapse of caveolae. We exposed 3T3-L1 adipocytes to the cholesterol depleting agent methyl-β-cyclodextrin, which results in a sudden and extensive degradation of cavin-2 by the proteasome and a concomitant movement of cavin-1 from the plasma membrane to the cytosol along with loss of caveolae. The recovery of cavin-2 at the plasma membrane is cholesterol-dependent and is required for the return of cavin-1 from the cytosol to the cell surface and caveolae restoration. Expression of shRNA directed against cavin-2 also results in a cytosolic distribution of cavin-1 and loss of caveolae. Taken together, these data demonstrate that cavin-2 functions as a cholesterol responsive component of caveolae that is required for cavin-1 localization to the plasma membrane, and caveolae structural integrity

IGF1R Signaling in Ewing Sarcoma Is Shaped by Clathrin-/Caveolin-Dependent Endocytosis

Receptor endocytosis is critical for cell signaling. IGF1R mediates an autocrine loop that is de-regulated in Ewing Sarcoma (ES) cells. Here we study the impact of IGF1R internalization, mediated by clathrin and caveolin-1 (CAV1), in ES signaling. We used clathrin and CAV1-siRNA to interfere in clathrin- and caveolin-dependent endocytosis. Chlorpromazine (CPMZ) and methyl-beta-cyclo-dextrin (MCD) were also used in order to inhibit clathrin- and caveolin-dependent endocytosis, respectively. We analyzed IGF1R internalization and co-localization with clathrin and CAV1 upon ligand binding, as well as the status of the IGF1R pathway, cellular proliferation, and the apoptosis of interfered and inhibited ES cells. We performed a high-throughput tyrosine kinase phosphorylation assay to analyze the effects of combining the IGF1R tyrosine kinase inhibitor AEW541 (AEW) with CPMZ or MCD on the intracellular phospho-proteome. We observed that IGF1R is internalized upon ligand binding in ES cells and that this process is dependent on clathrin or CAV1. The blockage of receptor internalization inhibited AKT and MAPK phosphorylation, reducing the proliferative rate of ES cells and increasing the levels of apoptosis. Combination of AEW with CPMZ or MCD largely enhanced these effects. CAV1 and clathrin endocytosis controls IGF1R internalization and signaling and has a profound impact on ES IGF1R-promoted survival signaling. We propose the combination of tyrosine-kinase inhibitors with endocytosis inhibitors as a new therapeutic approach to achieve a stronger degree of receptor inhibition in this, or other neoplasms dependent on IGF1R signaling

Early antecedents of childhood impulsivity: The role of parent-child interaction, cognitive competence, and temperament

This prospective longitudinal investigation examined early mother-child interaction as a predictor of children's later self-control capabilities. Multimethod assessments of mother-child relationships, primarily focused on observed relationship qualities in the home, were conducted during the first 2 years and related to children's later impulse control capabilities. Child cognitive competence and temperament assessed during the 2nd year were also related to later impulsivity. Follow-up assessments of children's impulsivity were conducted at age 6 ( N= 79), using a variety of laboratory measures. Findings indicated that responsive, cognitively stimulating parenttoddler interactions in the 2nd year modestly predicted later measures of cognitive nonimpulsivity and ability to delay gratification. Security of mother-infant attachment predicted the same outcomes, but only for boys and not for girls. Child cognitive competence in the 2nd year also consistently predicted children's later impulse control capabilities, although this was not true for measures of child temperament. Overall, the findings support a multidimensional and developmental conceptualization of the early antecedents of childhood impulsivity .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44580/1/10802_2004_Article_BF00916568.pd

In situ Raman analysis of reduced-graphene oxide-based electroactive nanofluids

This study investigates the effect of an applied stationary voltage on the vibrational properties of 1 M HSO and HSO-based reduced-graphene oxide (rGO) nanofluids, commonly used as electrolytes in electrochemical cells. Our findings indicate that the energy of the symmetric stretching vibrations of HSO remains unaffected by the electric field. However, a slight deviation toward lower energy and an enhancement of Raman intensity are observed in the asymmetric stretching vibration of HSO due to the applied voltage. Furthermore, the addition of rGO to the base fluid produces a significant redshift in the symmetric stretching bands, indicating that the presence of rGO produces important changes at the macroscopic level in the base fluid. Synchronous and asynchronous maps further uncover the positive correlations between the D and G bands as well as between rGO and the base fluid bands. Specifically, the asynchronous map revealed complex dynamics between the rGO and HSO bands and only positive correlations between HSO bands. These results demonstrate the potential of Raman spectroscopy as a non-invasive technique to systematically study the influence of electric fields on the vibrational properties of fluids and nanofluids, which can ultimately lead to the development of significantly more efficient electrochemical cells

Anàlisi dels crèdits de síntesi a l'ESO : el món del cinema

Este documento no está publicadoEsta carpeta es fruto de un grupo de trabajo en el IES Lluís de Requesens de Molins de Rei (Barcelona) y consta de tres volúmenes: el primero es la memoria del trabajo llevado a cabo por el grupo de trabajo, el segundo es el material utilizado en las sesiones con los alumnos y el tercer volumen es el trabajo realizado por los alumnos. Las actividades recogidas en el segundo volumen tratan los temas de: las tareas cinematográficas, el guión cinematográfico, la expresión corporal en escena, los géneros cinematográficos, la cámara y sus posibilidades, el estudio de la programación fílmica televisiva, las primeras máquinas de cine, la localización de escenarios naturales, la banda sonora, el doblaje, la maqueta del decorado y el cartel de la película.CataluñaES