Aggregation of liposomes induced by calcium: A structural and kinetic study

In this work, the calcium-induced aggregation of phosphatidylserine liposomes is probed by means of the analysis of the kinetics of such process as well as the aggregate morphology. This novel characterization of liposome aggregation involves the use of static and dynamic light-scattering techniques to obtain kinetic exponents and fractal dimensions. For salt concentrations larger than 5 mM, a diffusion-limited aggregation regime is observed and the Brownian kernel properly describes the time evolution of the diffusion coefficient. For slow kinetics, a slightly modified multiple contact kernel is required. In any case, a time evolution model based on the numerical resolution of Smoluchowski's equation is proposed in order to establish a theoretical description for the aggregating system. Such a model provides an alternative procedure to determine the dimerization constant, which might supply valuable information about interaction mechanisms between phospholipid vesicles.

MMPBSA decomposition of the binding energy throughout a molecular dynamics simulation of Amyloid-Beta (Aß10-35) aggregation

Recent experiments with amyloid-beta (Aß) peptides indicate that the formation of toxic oligomers may be an important contribution to the onset of Alzheimer's disease. The toxicity of Aß oligomers depend on their structure, which is governed by assembly dynamics. However, a detailed knowledge of the structure of at the atomic level has not been achieved yet due to limitations of current experimental techniques. In this study, replica exchange molecular dynamics simulations are used to identify the expected diversity of dimer conformations of Aß10-35 monomers. The most representative dimer conformation has been used to track the dimer formation process between both monomers. The process has been characterized by means of the evolution of the decomposition of the binding free energy, which provides an energetic profile of the interaction. Dimers undergo a process of reorganization driven basically by inter-chain hydrophobic and hydrophilic interactions and also solvation/desolvation processes.

Deficit in memory consolidation (abnormal forgetting rate) in childhood temporal lobe epilepsy. Pre and postoperative long-term observation.

Deficits in memory consolidation have been reported in adult patients with epilepsy but, not to our knowledge, in children. We report the long-term follow-up (9 y. o. to 18 y. o.) of a boy who suffered from temporal lobe epilepsy and underwent a left temporal lobectomy with amygdalo-hippocampal resection at the age of 10. He showed an abnormal forgetting rate when trying to encode new information and a significant deficit for retrieving remote episodic memories (when compared with his twin brother), both consistent with a consolidation disorder. His memory condition slightly improved after cessation of the epilepsy, nevertheless did not normalize. No standard memory assessment could pinpoint his memory problem, hence an adapted methodology was needed. We discuss the nature of the memory deficit, its possible causes and its clinical implications.

Temporal changes in mosquito abundance (Culex pipiens), avian malaria prevalence and lineage composition

Background: Knowledge on the temporal dynamics of host/vector/parasite interactions is a pre-requisite to further address relevant questions in the fields of epidemiology and evolutionary ecology of infectious diseases. In studies of avian malaria, the natural history of Plasmodium parasites with their natural mosquito vectors, however, is mostly unknown. Methods: Using artificial water containers placed in the field, we monitored the relative abundance of parous females of Culex pipiens mosquitoes during two years (2010-2011), in a population in western Switzerland. Additionally, we used molecular tools to examine changes in avian malaria prevalence and Plasmodium lineage composition in female C. pipiens caught throughout one field season (April-August) in 2011. Results: C. pipiens relative abundance varied both between years and months, and was associated with temperature fluctuations. Total Plasmodium prevalence was high and increased from spring to summer months (13.1-20.3%). The Plasmodium community was composed of seven different lineages including P. relictum (SGS1, GRW11 and PADOM02 lineages), P. vaughani (lineage SYAT05) and other Plasmodium spp. (AFTRU5, PADOM1, COLL1). The most prevalent lineages, P. vaughani (lineage SYAT05) and P. relictum (lineage SGS1), were consistently found between years, although they had antagonistic dominance patterns during the season survey. Conclusions: Our results suggest that the time window of analysis is critical in evaluating changes in the community of avian malaria lineages infecting mosquitoes. The potential determinants of the observed changes as well as their implications for future prospects on avian malaria are discussed.

CHO cell engineering to prevent polypeptide aggregation and improve therapeutic protein secretion.

The ability to efficiently produce recombinant proteins in a secreted form is highly desirable and cultured mammalian cells such as CHO cells have become the preferred host as they secrete proteins with human-like post-translational modifications. However, attempts to express high levels of particular proteins in CHO cells may consistently result in low yields, even for non-engineered proteins such as immunoglobulins. In this study, we identified the responsible faulty step at the stage of translational arrest, translocation and early processing for such a "difficult-to-express" immunoglobulin, resulting in improper cleavage of the light chain and its precipitation in an insoluble cellular fraction unable to contribute to immunoglobulin assembly. We further show that proper processing and secretion were restored by over-expressing human signal receptor protein SRP14 and other components of the secretion pathway. This allowed the expression of the difficult-to-express protein to high yields, and it also increased the production of an easy-to-express protein. Our results demonstrate that components of the secretory and processing pathways can be limiting, and that engineering of the secretory pathway may be used to improve the secretion efficiency of therapeutic proteins from CHO cells.

Variabilidad temporal de algunas propiedades químicas en un suelo sometido a distintas sucesiones de cultivo

El presente trabajo ha sido realizado en la Finca Experimental "La Poveda" en Arganda del Rey (Madrid), con las siguientes coordenadas geográficas: latitud 40º19' N; longitud 3º19' W Gr; y altitud 550 m. El objetivo principal consiste en el estudio de la variabilidad temporal de algunas propiedades químicas en un suelo sometido a distintas sucesiones de cultivo. Para el estudio de la variabilidad temporal de las características químicas el muestreo se realizó en los meses de febrero y septiembre de 1993 y febrero y septiembre de 1994. La materia orgánica del sistema Prado/Veza-Avena presenta el menor coeficiente de variación con respecto a los sistemas monocultivo de Cebada y Veza-Avena/Girasol. El menor contenido de materia orgánica a lo largo del tiempo lo presenta el sistema Cebada/Cebada. Los sistemas Prado/Veza-Avena y Veza-Avena/Girasol presentaron contenidos de materia orgánica 42,86% y 40,54% superiores al del sistema Cebada/Cebada.

Temporal quantification of MAPK induced expression in single yeast cells.

The quantification of gene expression at the single cell level uncovers novel regulatory mechanisms obscured in measurements performed at the population level. Two methods based on microscopy and flow cytometry are presented to demonstrate how such data can be acquired. The expression of a fluorescent reporter induced upon activation of the high osmolarity glycerol MAPK pathway in yeast is used as an example. The specific advantages of each method are highlighted. Flow cytometry measures a large number of cells (10,000) and provides a direct measure of the dynamics of protein expression independent of the slow maturation kinetics of the fluorescent protein. Imaging of living cells by microscopy is by contrast limited to the measurement of the matured form of the reporter in fewer cells. However, the data sets generated by this technique can be extremely rich thanks to the combinations of multiple reporters and to the spatial and temporal information obtained from individual cells. The combination of these two measurement methods can deliver new insights on the regulation of protein expression by signaling pathways.

Seguiment temporal de la reserva marina de les Illes Medes. Informe anual. Any 1997

L'objectiu que marca la Llei 19/1990, de 10 de desembre del Parlament de Catalunya és la conservació de la fauna i flora dels fons marins de les illes Medes. I l¿objectiu dels treballs de seguiment que, des del 1990, ve efectuant l¿equip del Departament d¿Ecologia en la Reserva Marina de les Illes Medes per encàrrec delDepartament d¿Agricultura, Ramaderia i Pesca (primer de la seva Direcció General de Pesca Marítima, i des del 1996 de la Direcció General de Medi Natural) és avaluar els resultats de la dita conservació.

Seguiment temporal de la reserva marina de les Illes Medes. Informe anual. Any 1999

Aquesta Memòria constitueix la novena entrega, corresponent als resultatsobtinguts al llarg de 1999, dels treballs de seguiment que, des del 1990, ve efectuantl'equip del Departament d'Ecologia de la Universitat de Barcelona en laReserva Marina de les Illes Medes, en compliment dels imperatius que marca la Llei19/1990, de 10 de desembre del Parlament de Catalunya. L'objectiu d'aquesta Lleiés la conservació de la fauna i flora dels fons marins de les illes Medes, i el seu Plad'Usos estableix l'obligatorietat de realitzar estudis científics de monitorització que guiïn i avalin l'adequació de la gestió.

Seguiment temporal de l'àrea marina protegida de les Illes Medes. Informe anual. Any 2000

Aquesta Memòria constitueix la desena remesa, corresponent als resultats obtinguts en 2000, dels treballs de seguiment que, des del 1990, ve efectuant l'equip del Departament d'Ecologia en la Reserva Marina de les Illes Medes per encàrrec del Departament d'Agricultura, Ramaderia i Pesca (de 1990 a 1998) i del Departament de Medi Ambient (des de 1999) en compliment dels imperatius que marca la Llei 19/1990, de 10 de desembre del Parlament de Catalunya. L'objectiu de dita Llei és la conservació de la fauna i flora dels fons marins de les illes Medes, i el seu Pla d'Usos estableix l'obligatorietat de realitzar estudis científics de monitoritzacióque guiïn i avalin l'adequació de la gestió.

Seguiment temporal de l'àrea marina protegida de les Illes Medes. Informe anual. Any 2001

Aquesta Memòria constitueix la onzena remesa, corresponent als resultats obtinguts en 2001, dels treballs de seguiment que, des del 1990, ve efectuant l'equip del Departament d'Ecologia en la Reserva Marina de les Illes Medes per encàrrec del Departament d'Agricultura, Ramaderia i Pesca (de 1990 a 1998) i del Departament de Medi Ambient (des de 1999) en compliment dels imperatius que marca la Llei 19/1990, de 10 de desembre del Parlament de Catalunya. L'objectiu de dita Llei és la conservació de la fauna i flora dels fons marins de les illes Medes, i el seu Pla d'Usos estableix l'obligatorietat de realitzar estudis científics de monitorització que guiïn i avalin l'adequació de la gestió.