Overfeeding, Autonomic Regulation and Metabolic Consequences

The autonomic nervous system plays an important role in the regulation of body processes in health and disease. Overfeeding and obesity (a disproportional increase of the fat mass of the body) are often accompanied by alterations in both sympathetic and parasympathetic autonomic functions. The overfeeding-induced changes in autonomic outflow occur with typical symptoms such as adiposity and hyperinsulinemia. There might be a causal relationship between autonomic disturbances and the consequences of overfeeding and obesity. Therefore studies were designed to investigate autonomic functioning in experimentally and genetically hyperphagic rats. Special emphasis was given to the processes that are involved in the regulation of peripheral energy substrate homeostasis. The data revealed that overfeeding is accompanied by increased parasympathetic outflow. Typical indices of vagal activity (such as the cephalic insulin release during food ingestion) were increased in all our rat models for hyperphagia. Overfeeding was also accompanied by increased sympathetic tone, reflected by enhanced baseline plasma norepinephrine (NE) levels in both VMH-lesioned animals and rats rendered obese by hyperalimentation. Plasma levels of NE during exercise were, however, reduced in these two groups of animals. This diminished increase in the exercise-induced NE outflow could be normalized by prior food deprivation. It was concluded from these experiments that overfeeding is associated with increased parasympathetic and sympathetic tone. In models for hyperphagia that display a continuously elevated nutrient intake such as the VMH-lesioned and the overfed rat, this increased sympathetic tone was accompanied by a diminished NE response to exercise. This attenuated outflow of NE was directly related to the size of the fat reserves, indicating that the feedback mechanism from the periphery to the central nervous system is altered in the overfed state.

Zirconium ion mediated formation of liposome multilayers

Phospholipid vesicles have attracted considerable interest as a platform for a variety of biomolecular binding assays, especially in the area of membrane protein sensing. The development of liposome-based biosensors widely relies on the availability of simple and efficient protocols for their surface immobilization. We present a novel approach toward the creation of three-dimensional phospholipid vesicle constructs using multivalent zirconium ions as linkers between the liposomes. Such three-dimensional sensing platforms are likely to play a key role in the development of biosensing devices with increased loading capacity and sensitivity. After demonstrating the affinity of Zr(4+) toward the phospholipids, we formed vesicle multilayers by sequential injections of solutions containing either liposomes or ZrOCl(2). In situ adlayer characterization was carried out by optical waveguide lightmode spectroscopy (OWLS) and quartz crystal microbalance with dissipation (QCM-D) measurements while imaging was performed by atomic force microscopy (AFM) and fluorescence microscopy. Multilayers were successfully constructed, and as demonstrated in a model fluorescence-based biomolecular binding assay, the sensor's loading capacity was increased. Furthermore, we observed that lipid exchange between the vesicles is promoted in the presence of Zr(4+) and that addition of a phosphate-containing buffer leads to adlayer loosening and creation of lipidic tubular structures. The approach presented here could be applied to the study of membrane proteins in a highly sensitive manner due to the increased surface area or to produce functional coatings for controlled drug release and host response

Strongyloïdiase: corticothérapie et dermite linéaire prurigineuse

L’infection à Strongyloides stercoralis est une helminthiase endémique des pays tropicaux et subtropicaux. Des cas de transmission sporadique surviennent également dans certaines régions du bassin méditerranéen. Une fois acquise, cette parasitose peut persister durant plusieurs décennies en phase latente de façon a- ou pauci-symptomatique. En cas d’immuno-suppression, un syndrome d’hyperinfestation (HS) ou une strongyloïdiase disséminée (DS) peuvent se développer et engendrer des complications sévères, parfois fatales. Le dermatologue doit être attentif aux manifestations cutanées provo-quées par ce nématode. Aussi, afin d’éviter le risque de HS/DS, chaque patient ayant séjourné en zone d’endémie devrait bénéficier d’un dépis-tage avant toute prescription de corticothérapie systémique ou autre trai-tement immunosuppresseur. Pour illustrer les lésions cutanées caractéris-tiques de cette pathologie, nous présentons deux cas de strongyloïdiase chez des patients traités par corticothérapie

From nanodroplets to continuous films: how the morphology of polyelectrolyte multilayers depends on the dielectric permittivity and the surface charge of the supporting substrate

Using atomic force microscopy, we investigated how the morphology of layer-by-layer deposited polyelectrolyte multilayers is influenced by the physical properties of the supporting substrate. The surface coverage of the assembly and its topography were found to be dependent on the dielectric permittivity of the substrate and the strength of the electrostatic interactions between polyanions and polycations. For poly(allylamine hydrochloride)/poly(styrene sulfonate) (PAH/PSS), a strongly interacting polyelectrolyte couple, no dependency of the surface morphology on the physical properties of the underlying substrate was observed. In contrast, the weakly interacting pair poly(L-lysine)/hyaluronic acid (PLL/HA) formed rapidly continuous, flat layers on substrates of low dielectric permittivity and inhomogeneous droplet-films on substrates of high dielectric permittivity. Variations in the dielectric permittivity account for changes in the image charges that are induced in the substrate. These changes influence the balance between repulsive electrostatic forces (and image forces) and attractive van der Waals interactions, and thus cause the differences in surface morphology. Differences in surface charge did not influence the morphology of the polyelectrolyte multilayers, but higher surface charge resulted in more polymeric material adsorbed on the surface. A comparison between (PLL/HA) multilayers with and without an initial layer of poly(ethyleneimine) (PEI) supports this hypothesis