Overexpression of the carbohydrate binding module from Solanum lycopersicum expansin 1 (Sl-EXP1) modifies tomato fruit firmness and Botrytis cinerea susceptibility.

Firmness, one of the major determinants of postharvest quality and shelf life of fruits is determined by the mechanical resistance imposed by the plant cell wall. Expansins (EXP) are involved in the non-hydrolytic metabolic disassembly of plant cell walls, particularly in processes where relaxation of the wall is necessary, such as fruit development and ripening. As many carbohydrate-associated proteins, expansins have a putative catalytic domain and a carbohydrate-binding module (CBM). Several strategies have been pursued to control the loss of fruit firmness during storage. Most of the approaches have been to suppress the expression of key enzymes involved in the cell wall metabolism, but this is the first time that a CBM was overexpressed in a fruit aimed to control cell wall degradation and fruit softening. We report the constitutive overexpression of the CBM of Solanum lycopersicum expansin 1 (CBM-SlExp1) in the cell wall of tomato plants, and its effects on plant and fruit phenotype. Overexpression of CBM-SlExp1 increased the mechanical resistance of leaves, whereas it did not modify plant growth and general phenotype. However, transgenic plants showed delayed softening and firmer fruits. In addition, fruits were less susceptible to Botrytis cinerea infection, and the "in vitro" growth of the fungus on media containing AIR from the pericarp of transgenic fruits was lower than controls. The possibility of overexpressing a CBM of a fruit-specific expansin to control cell wall degradation and fruit softening is discussed.

Morphological, rheological and mechanical characterization of polypropylene nanocomposite blends.

In the present work, the effectiveness of styrene/ethylene-butylene/styrene rubbers grafted with maleic anhydride (MA) and a metallocene polyethylene (mPE) as toughening materials in binary and ternary blends with polypropylene and its nanocomposite as continuous phases was evaluated in terms of transmission electron microscopy (TEM), scanning electron microscopy (SEM), oscillatory shear flow and dynamic mechanical thermal analysis (DMA). The flexural modulus and heat distortion temperature values were determined as well. A metallocene polyethylene and a polyamide-6 were used as dispersed phases in these binary and ternary blends produced via melt blending in a corotating twin-screw extruder. Results showed that the compatibilized blends prepared without clay are tougher than those prepared with the nanocomposite of PP as the matrix phase and no significant changes in shear viscosity, melt elasticity, flexural or storage moduli and heat distortion temperature values were observed between them. However, the binary blend with a nanocomposite of PP as matrix and metallocene polyethylene phase exhibited better toughness, lower shear viscosity, flexural modulus, and heat distortion temperature values than that prepared with polyamide-6 as dispersed phase. These results are related to the degree of clay dispersion in the PP and to the type of morphology developed in the different blends.

Adhesion and proliferation of cells on new polymers modified biomaterials.

Up to today, several techniques have been used to maintain cells in culture for studying many aspects of cell biology and physiology. More often, cell culture is dependent on proper anchorage of cells to the growth surface. Poly-l-lysine is commonly used as adhesive molecule. In this study, we present, as an alternative to poly-l-lysine, new polymer film substrates, realized by electropolymerization of different monomers on fluorine-doped tin oxide (FTO) surfaces since electropolymerization is a good method to coat selectively metallic or semiconducting electrodes with polymer films. So, the adhesion, proliferation and morphology of rat neuronal cell lines were investigated on polymer treated surfaces. Several amine-based biocompatible polymers were tested: polyethyleneimine (PEI), polypropyleneimine (PPI), polypyrrole (PPy) and poly(p-phenylenediamine) (PPPD). These polymer films were coated on FTO surfaces by electrochemical oxidation. After 8 h in a culture medium, a high percentage of cells was found to be attached to PEI and PPI compared to the other polymers and to the reference surfaces (glass and FTO uncovered). After 24 and 72 h in the culture medium, cells were found to proliferate faster on PEI and PPI than on other polymers and reference surfaces. Consequently, cells have a greater fold expansion on PEI and PPI than on PPPD, PPy or glass and FTO uncoated. From these results, we deduce that PEI and PPI can be useful as coating surface to cultivate neuronal cells.

Induction of humoral immune response to Salmonella typhimurium in mouse Peyer's patches.

The mechanisms of immune response generation and regulation at the intestinal level are not well known, mainly due to the lack of suitable and reproducible methods to measure local immune responses. The Cunningham direct and indirect hemolytic plaque assay for the quantification of antibody producing cells against Salmonella in Peyer's patches of mice orally infected with Salmonella typhimurium was used. After infection IgM and IgG producing cells were determined on days 6, 9, 12 and 19. Specific antibody producing cells appeared after bacterial invasion of Peyer's patches, nine days after infection. At this time, there were more antibody producing cells in the distal part of the intestine, which correlated with a higher infection of these Peyer's patches as detected by bacterial culture. After day nine, the number of plaque forming cells was similar in both parts of the intestine. The peak of response was on day 12 and diminished on day 19. The number of IgM and IgG producing cells was similar in all days analyzed. Histological analysis of Peyer's patches of infected mice showed inflammation with disorganization and tumefaction.