Effects of landfill leachate treatment on hepatopancreas of Armadillidium vulgare (Crustacea, Isopoda).

The major environmental impact of landfills is emission of pollutants via the leachate and gas pathways. The hepatopancreas of the terrestrial isopod Armadillidium vulgare (Isopoda, Crustacea, Latreille 1804) plays an important role in the bioaccumulation of contaminants, such as heavy metals. To evaluate the effects of landfill leachate treatment, 2 different approaches were applied: 1) the detection of accumulation of trace elements (As, Cd, Cr, Cu, Sb, Zn, Pb, Ni, V) in hepatopancreatic cells, and 2) the evaluation of biological effect of contaminants on fresh hepatopancreatic cells by flow-cytometric analyses. The presence of 2 different cell types (herein referred to as "small" [S] cells and "big" [B] cells, in agreement with the literature based on morphological examinations) was detected for the first time by flow cytometry, which also highlighted their different response to stress stimuli. In particular, B cells appeared more sensitive to landfill leachate treatment, being more damaged in the short term, while S cells seemed more adaptive. Furthermore, S cells could represent a pool from which they are able to differentiate into B cells. These findings were also confirmed by principal component analyses, underlining that S SYBR Green I bright cells correlate with specific chemicals (Ca, Cu, Co), confirming their resistance to stress stimuli, and suggesting that the decrease of specific cell types may prime other elements to replace them in a homeostasis-preservation framework.

Structural modifications and adsorption capability of C18-silica/binary solvent interphases studied by EPR and RP-HPLC.

The structure of the octadecyl (C18) chain layer attached to a silica surface in the presence of binary solvents (acetonitrile/water; methanol/water) was investigated by electron paramagnetic resonance (EPR) and reverse-phase high-performance liquid chromatography (RP-HPLC), using 4-hydroxy-2,2,6,6 tetramethylpiperidine-N-oxyl (Tempol) to mimic the behavior of pollutants with medium-low polarity. The computer-aided analysis of the EPR spectra provided structural and dynamical information of the probe and its environments which clarified the modifications of the chain conformations that occur at different solvent compositions. Capacity factors, k', were calculated as a function of the percentage of water/organic solvent (mobile phase), and the retention behavior of the C18-functionalized silica surface (stationary phase) was compared with the results obtained with EPR analysis under static conditions. In particular, EPR analysis showed that, at percentages of ACN equal or higher than 50%, the chain layer assume a quite ordered structure, whereas at percentages lower than 50% the chains tend to collapse and fold on the silica surface. In this latter situation, the hydrophobic net of the C18 chains strongly limits Tempol mobility. In methanol/water mixtures, both EPR and RP-HPLC analysis showed that the probe was adsorbed into a poorly ordered interphase. If the residual silanols at the silica surface were bonded to a sililating agent (endcapping), both EPR and RP-HPLC analysis showed a decreased adsorption of the probe with respect to the non-endcapped silica at the same mobile phase composition.

Time evolution of the aggregation process of peptides involved in neurodegenerative diseases and preventing aggregation effect of phosphorus dendrimers studied by EPR.

A key pathological event of prion and Alzheimer diseases is the formation of prion and amyloid plaques generated by peptide aggregation in the form of fibrils. Dendrimers have revealed their ability to prevent fibril formation and therefore cure neurodegenerative diseases. To provide information about the kinetics and the mechanism of peptide fibril formation and about the ability of the dendrimers to prevent peptide aggregation, we performed a computer-aided EPR analysis of the selected nitroxide spin probe 4-octyl-dimethylammonium,2,2,6,6-tetramethyl-piperidine-1-oxyl bromide (CAT8) in water solutions of the ß-amyloid peptide Aß 1-28 and the prion peptide PrP 185-208, which contain the fibril nucleation sites, in the absence and in the presence of phosphorus dendrimers. After a careful selection of the experimental conditions that allow aggregation to occur and to be monitored by EPR analysis over time, it was found that the Aß 1-28 fibrils formed in 220 min at 0.5 mM peptide, 0.05 mM CAT8, 0.04 mg/mL heparin, and pH = 5. As a consequence, the interacting sites available for cooperative interactions with CAT8 were engaged in the peptide-peptide interactions and a fraction of the probe was extracted in the fluid fibril/water interphase, while another fraction was trapped at the peptide/peptide interphase, showing a decrease in mobility. Conversely, in the presence of the dendrimer (at the selected, after several trials, peptide/dendrimer molar ratio = 50), due to dipole-dipole interactions with peptide monomers, the probe remained at the dendrimer/peptide interphase and the spectral parameters negligibly changed over time. A fraction of probes inserted in PrP 185-208 low-packed aggregates and monitored their fast formation after 90 min. However, the binding organization of the prion peptide negligibly changed upon aggregation in comparison to Aß 1-28. It is proposed that dendrimers mainly interfere in the lag (nucleation) phase of the prion peptide.