N.m.r. studies of synergistic kappa carrageenan—carob galactomannan gels

¹³C-n.m.r. spectroscopy has been used to investigate the carob galactomannan—kappa carrageenan binary gels. Starting from partially depolymerized carob samples, evidence for interaction and intermolecular binding was found by analysis of the spectra obtained in quantitative conditions and in the absolute intensity mode. From these, a reconstitution of the signals corresponding to C-1, C-4, C-5 and C-6 showed the existence of three kinds of galactomannan chains: the first ones with a low galactose content were strongly connected and as much had completely lost their mobility; but the chains with a high galactose content were still detected and could be divided in two groups according to their mobility.     

Finite element modeling of shell shape in the freshwater turtle Pseudemys concinna reveals a trade‐off between mechanical strength and hydrodynamic efficiency

Aquatic species can experience different selective pressures on morphology in different flow regimes. Species inhabiting lotic regimes often adapt to these conditions by evolving low‐drag (i.e., streamlined) morphologies that reduce the likelihood of dislodgment or displacement. However, hydrodynamic factors are not the only selective pressures influencing organismal morphology and shapes well suited to flow conditions may compromise performance in other roles. We investigated the possibility of morphological trade‐offs in the turtle Pseudemys concinna. Individuals living in lotic environments have flatter, more streamlined shells than those living in lentic environments; however, this flatter shape may also make the shells less capable of resisting predator‐induced loads. We tested the idea that “lotic” shell shapes are weaker than “lentic” shell shapes, concomitantly examining effects of sex. Geometric morphometric data were used to transform an existing finite element shell model into a series of models corresponding to the shapes of individual turtles. Models were assigned identical material properties and loaded under identical conditions, and the stresses produced by a series of eight loads were extracted to describe the strength of the shells. “Lotic” shell shapes produced significantly higher stresses than “lentic” shell shapes, indicating that the former is weaker than the latter. Females had significantly stronger shell shapes than males, although these differences were less consistent than differences between flow regimes. We conclude that, despite the potential for many‐to‐one mapping of shell shape onto strength, P. concinna experiences a trade‐off in shell shape between hydrodynamic and mechanical performance. This trade‐off may be evident in many other turtle species or any other aquatic species that also depend on a shell for defense. However, evolution of body size may provide an avenue of escape from this trade‐off in some cases, as changes in size can drastically affect mechanical performance while having little effect on hydrodynamic performance. J. Morphol. 2011. © 2011 Wiley‐Liss, Inc.     

LC3-associated phagocytosis in myeloid cells,a fireman that restrains inflammation and liver fibrosis,via immunoreceptor inhibitory signaling

ABSTRACT

Control of systemic and hepatic inflammation, in particular originating from monocytes/macrophages, is crucial to prevent liver fibrosis and its progression to end-stage cirrhosis. LC3-associated phagocytosis (LAP) is a non-canonical form of autophagy that shifts the monocyte/macrophage phenotype to an anti-inflammatory phenotype. In a recent study, we uncovered LAP as a protective mechanism against inflammation-driven liver fibrosis and systemic inflammation in the context of cirrhosis. We observed that LAP is enhanced in blood and liver monocytes from patients with liver fibrosis or those who progress to cirrhosis. Combining studies in which LAP was pharmacologically or genetically inactivated, we found that LAP limits inflammation in monocytes from cirrhotic patients, and the hepatic inflammatory profile in mice with chronic liver injury, resulting in anti-fibrogenic effects. Mechanistically, LAP-induced anti-inflammatory and antifibrogenic signaling results from enhanced expression of the Fc immunoreceptor FCGR2A/FcγRIIA and activation of an FCGR2A-mediated PTPN6/SHP-1 anti-inflammatory pathway, leading to increased engulfment of IgG into LC3 ⁺ phagosomes. In patients with cirrhosis progressing to multi-organ failure (acute-on chronic liver failure), LAP is lost in monocytes, and can be restored by targeting FCGR2A-mediated PTPN6/SHP-1 signaling. These data suggest that sustaining LAP may open novel therapeutic perspectives for patients with end-stage liver disease.     

Small-angle x-ray scattering of κ-carrageenan based systems: Sols,gels, and blends with carob galactomannan

Small-angle x-ray scattering using a synchroton x-ray monochromatic radiation was carried out to investigate the structure of different polysaccharides in aqueous medium: carob galactomannan, κ-carrageenan in the sol and in the gel states, and κ-carrageenan-carob galactomannan mixed systems. Experiments performed on a 0.2% carob galactomannan solutions confirmed that this polysaccharide behaved as a neutral polymer in a good solvent. For K-carrageenan in the / state, either in the sodium form or in the cesium form, a maximum in the scattering curve was evidenced. Position and height of this maximum changed with K-carrageenan concentration in close agreement with what is expected for wormlike polyelectrolyte in semidilute solution. In the case of k-carrageenan in the gel state, in the cesium form, scattering curves also exhibited a maximum at an intermediate Q value. The position of this correlation peak did not change with concentration while its intensity increased. This effect was ascribed to a packing of rodlike structures by analogy with a suspension of colloidal elongated particles. This local structure could be viewed as bundles of parallel double helices. Addition of carobgalactomannan in κ-carrageenan gels induced dramatic structural changes. As the galactomannan concentration increased, the correlation peak tended to vanish. In contrast, no change in the cross-sectional radius of gyration was noticed. This phenomenon suggested a screening effect of the galactomannan, resulting in a loss of the correlation between the κ-carrageenan double helices. © 1995 John Wiley & Sons, Inc.     

Exploring the Nicotinic Acetylcholine Receptor-associated Proteome with iTRAQ and Transgenic Mice

Neuronal nicotinic acetylcholine receptors (nAChRs) containing α4 and β2 subunits are the principal receptors in the mammalian central nervous system that bind nicotine with high affinity. These nAChRs are involved in nicotine dependence, mood disorders, neurodegeneration and neuroprotection. However, our understanding of the interactions between α4β2-containing (α4β2¹) nAChRs and other proteins remains limited. In this study, we identified proteins that interact with α4β2¹ nAChRs in a genedose dependent pattern by immunopurifying β2¹ nAChRs from mice that differ in α4 and β2 subunit expression and performing proteomic analysis using isobaric tags for relative and absolute quantitation (iTRAQ). Reduced expression of either the α4 or the β2 subunit results in a correlated decline in the expression of a number of putative interacting proteins. We identified 208 proteins co-immunoprecipitated with these nAChRs. Furthermore, stratified linear regression analysis indicated that levels of 17 proteins was correlated significantly with expression of α4β2 nAChRs, including proteins involved in cytoskeletal rearrangement and calcium signaling. These findings represent the first application of quantitative proteomics to produce a β2¹ nAChR interactome and describe a novel technique used to discover potential targets for pharmacological manipulation of α4β2 nAChRs and their downstream signaling mechanisms.     

A review of dietary stilbenes: sources and bioavailability

Stilbenes are a class of phenolic metabolites found in various edible plants, such as grapevine, berries and peanuts. Their bioactivitiy and their potential benefits for human health have been the subject of several studies. Among all identified stilbenes, resveratrol has been particularly studied and results from literature showed that it presents several biological activities, including antioxidant, anti-inflammatory and antiproliferative effects. Likewise, some researches focused on other stilbenes and highlighted similar biological activity for those compounds. However, stilbenes present a high diversity in their phenolic structures (various chemical substituents and polymerization) which is a determining factor of their absorption and metabolism rates. Consequently, this could affect the effectiveness of stilbenes in vivo. In this context, an evaluation of the bioavailability and metabolism of stilbenes is necessary to move forward with pharmacological and clinical studies. Hence, this review aims to present recently obtained data and results concerning stilbenes sources and bioavailability, as a contribution to the valorization of the role of dietary stilbenes in the human diet.     

The character and use of the Soros Hill Obsidian source,Antiparos (Greece)

This article details the geological and elemental character of the obsidian from the Soros Hill source on the Cycladic island of Antiparos, Greece. EDXRF was used to analyse 40 geological geo-referenced samples. The products are clearly chemically discriminated from those of the other Aegean sources, and those from the Carpathians and central Anatolia. While the obsidian is of excellent tool-making quality, the small size of its nodules seems to have made it a less attractive raw material, attested at only a handful of prehistoric sites in the central Cyclades.     

Seasonal dynamics of a glycan-degrading flavobacterial genus in a tidally mixed coastal temperate habitat

Coastal marine habitats constitute hotspots of primary productivity. In temperate regions, this is due both to massive phytoplankton blooms and dense colonisation by macroalgae that mostly store carbon as glycans, contributing substantially to local and global carbon sequestration. Because they control carbon and energy fluxes, algae-degrading microorganisms are crucial for coastal ecosystem functions. Environmental surveys revealed consistent seasonal dynamics of alga-associated bacterial assemblages, yet resolving what factors regulate the in situ abundance, growth rate and ecological functions of individual taxa remains a challenge. Here, we specifically investigated the seasonal dynamics of abundance and activity for a well-known alga-degrading marine flavobacterial genus in a tidally mixed coastal habitat of the Western English Channel. We show that members of the genus Zobellia are a stable, low-abundance component of healthy macroalgal microbiota and can also colonise particles in the water column. This genus undergoes recurring seasonal variations with higher abundances in winter, significantly associated to biotic and abiotic variables. Zobellia can become a dominant part of bacterial communities on decaying macroalgae, showing a strong activity and high estimated in situ growth rates. These results provide insights into the seasonal dynamics and environmental constraints driving natural populations of alga-degrading bacteria that influence coastal carbon cycling.