Antimicrobial and cell-penetrating peptides induce lipid vesicle fusion by folding and aggregation

According to their distinct biological functions, membrane-active peptides are generally classified as antimicrobial (AMP), cell-penetrating (CPP), or fusion peptides (FP). The former two classes are known to have some structural and physicochemical similarities, but fusogenic peptides tend to have rather different features and sequences. Nevertheless, we found that many CPPs and some AMPs exhibit a pronounced fusogenic activity, as measured by a lipid mixing assay with vesicles composed of typical eukaryotic lipids. Compared to the HIV fusion peptide (FP23) as a representative standard, all designer-made peptides showed much higher lipid-mixing activities (MSI-103, MAP, transportan, penetratin, Pep1). Native sequences, on the other hand, were less fusogenic (magainin 2, PGLa, gramicidin S), and pre-aggregated ones were inactive (alamethicin, SAP). The peptide structures were characterized by circular dichroism before and after interacting with the lipid vesicles. A striking correlation between the extent of conformational change and the respective fusion activities was found for the series of peptides investigated here. At the same time, the CD data show that lipid mixing can be triggered by any type of conformation acquired upon binding, whether α-helical, β-stranded, or other. These observations suggest that lipid vesicle fusion can simply be driven by the energy released upon membrane binding, peptide folding, and possibly further aggregation. This comparative study of AMPs, CPPs, and FPs emphasizes the multifunctional aspects of membrane-active peptides, and it suggests that the origin of a peptide (native sequence or designer-made) may be more relevant to define its functional range than any given name

Radiodensity evaluation of dental impression materials in comparison to tooth structures

In the most recent decades, several developments have been made on impression materials' composition, but there are very few radiodensity studies in the literature. It is expected that an acceptable degree of radiodensity would enable the detection of small fragments left inside gingival sulcus or root canals. OBJECTIVE: The aim of this study was to determine the radiodensity of different impression materials, and to compare them to human and bovine enamel and dentin. MATERIAL AND METHODS: Twenty-five impression materials, from 5 classes, were studied: addition and condensation silicones, polyether, polysulfides and alginates. Five 1-mm-thick samples of each material and tooth structure were produced. Each sample was evaluated 3 times (N=15), being exposed to x-ray over a phosphor plate of Digora digital system, and radiodensity was obtained by the software Digora for Windows 2.5 Rev 0. An aluminum stepwedge served as a control. Data were subjected to Kruskal-Wallis and Dunn's method (&#945;=0.05). RESULTS: Different materials and respective classes had a different behavior with respect to radiodensity. Polysulfides showed high values of radiodensity, comparable to human enamel (p>0.05), but not to bovine enamel (p<0.05). Human dentin was similar only to a heavy-body addition silicon material, but bovine dentin was similar to several materials. Generally, heavy-body materials showed higher radiodensity than light-body ones (p<0.05). CONCLUSION: Impression materials' radiodensity are influenced by composition, and almost all of them would present a difficult detection against enamel or dentin background in radiographic examinations

Influence of explanting season on in vitro multiplication of the medicinal herb, Tridax procumbens L.

A protocol for complete regeneration of Tridax procumbens, a medicinally important plant, was accomplished through in vitro culturing. From nodal segments explants, high percentage of bud break and multiple shoot formation was induced between July and September on MS medium supplemented with BAP (1 mg L-1). Rooting of the excised shoots from secondary cultures was excellent on halfstrength MS medium having 1 mg L-1 IBA. Micropropagated plants when transplanted on garden soil flowered after 6 - 8 weeks. Explants sampled during December had low percentage of bud break and less shoot number per explant. Epicuticular wax (EW) and cuticular transpiration varied in the leaves collected during July and December; while under in vitro conditions, no marked differences were observed in regards to the 2 parameters. The epicuticular contents correlated with the rate of cuticular transpiration. The adaptive significance of EW during December is discussed

Fitting and cementation

This chapter will emphasise the need to:Try in restorations using a logical sequence to locate issues preventing seating, and adjust for optimum fit, aesthetics, and occlusion.Be aware of materials needing specific surface treatments prior to resin bonding.Collaborate with your nurse and use scrupulous moisture control while adhesive bonding and when using multistage adhesives.Select a conventional cement (e.g. zinc phosphate) for retentive preps with subgingival margins where resin bonding and removal of extruded cement would be difficult.Appreciate the different approaches needed for luting veneers and securing implant crowns (screw-retained and cemented).Arrange follow-up and appropriate supportive periodontal care where this is indicated