Protein expression has been compared in human substantia nigra specimens from Parkinson's disease (PD) patients and from controls, and 44 proteins expressed in this midbrain region were identified by peptide mass fingerprinting. Among them, nine showed changes in their abundance. L and M neurofilament chains are less abundant in PD specimens, whereas peroxiredoxin II, mitochondrial complex III, ATP synthase D chain, complexin I, profilin, L-type calcium channel delta-subunit, and fatty-acid binding protein are significantly more present in PD samples than in controls. Besides the consolidated view of oxidative stress involvement in PD pathogenesis, suggested by overexpression of mitochondrial and reactive oxygen species (ROS)-scavenging proteins, these results indicate a possible potentiation mechanism of afferent signals to substantia nigra following degeneration of dopaminergic neurons.

MR-labeling of cells may be carried out by adding a Gd-based contrast agent to the incubation media. The amount of gadolinium internalized in HTC and C6 cells upon incubation with Gd-DTPA-BMA is circa one order of magnitude higher than those found with Gd-DTPA, Gd-DOTA and Gd-HPDO3A, respectively. The comparison of relaxometric and mass spectrometry determinations allows us to establish that only a minor fraction of intact Gd-DTPA-BMA is internalized into the cells. Moreover the binding/uptake behavior shown by Gd-DTPA-BMA resembles that found when GdCl 3 is added to the incubation medium. We suggest that the lower stability of Gd-DTPA-BMA is responsible for a shift in the dissociation equilibrium that results in the net transfer of Gd 3þ ions on the cell membrane followed by a slower internalization process. The transmetallation process is mediated by components of the incubation media, among which a dominant role is represented by phosphate anions. The uptake of Gd 3þ ions is clearly reflected in the drastic decrease of cell viability observed for cells labeled with Gd-DTPA-BMA.

At present, the so-called "substantial equivalence" is the only widely accepted criterion for deciding whether or not a transgenic food is, from an alimentary point of view, to be considered totally correspondent to the "traditional" one from which it derives. Although never exactly defined, it deals with a comparison between the chemical composition of the two foods. A more in-depth analysis can be performed by one of the most suitable methods that allows for the simultaneous screening of many components without prior identification, the analysis of the proteome. As a model for testing this kind of approach, we compared protein expression of two types of tomato plants, having the same genetic background, except for a virus resistance trait introduced by genetic engineering. When proteins extracted from seedlings of the two types were analyzed by two-dimensional electrophoresis, no significant differences, either qualitative or quantitative, were detected, indicating that in this case the expression of major proteins was unmodified by the genetic manipulation. Fifteen proteins were identified by peptide mass fingerprinting.

Rat hepatocytes in culture take up [ 14 C]-agmatine by both a high-affinity transport system [K M 0.03 mm; V max 30 pmol´min´(mg protein) 21 ] and a low-affinity system. The high-affinity system also transports putrescine, but not cationic amino acids such as arginine, and the polyamines spermidine and spermine. The rate of agmatine uptake is increased in cells deprived of polyamines with difluoromethylornithine. Of the agmatine taken up, 10% is transformed into polyamines and 50% is transformed into 4-guanidinobutyrate, as demonstrated by HPLC and MS. Inhibition by aminoguanidine and pargyline shows that this is due to diamine oxidase and an aldehyde dehydrogenase. 14 C-4-aminobutyrate is also accumulated in the presence of an inhibitor of 4-aminobutyrate transaminase.

Apolipoprotein A-I (ApoA-I), a major component of HDL, binds haptoglobin, a plasma protein transporting to liver or macrophages free Hb for preventing hydroxyl radical production. This work aimed to assess whether haptoglobin protects ApoA-I against this radical. Human ApoA-I structure, as analyzed by electrophoresis and MS, was found severely altered by hydroxyl radicals in vitro. Lower alteration of ApoA-I was found when HDL was oxidized in the presence of haptoglobin. ApoA-I oxidation was limited also when the complex of haptoglobin with both high-density lipoprotein and Hb, immobilized on resin beads, was exposed to hydroxyl radicals. ApoA-I function to stimulate cholesterol esterification was assayed in vitro by using ApoA-I-containing liposomes. Decreased stimulation was observed when liposomes oxidized without haptoglobin were used. Conversely, after oxidative stress in the presence of haptoglobin (0.5 microM monomer), the liposome activity did not change. Plasma of carrageenan-treated mice was analyzed by ELISA for the levels of haptoglobin and ApoA-I, and used to isolate HDL for MS analysis. Hydroxyproline-containing fragments of ApoA-I were found associated with low levels of haptoglobin (18 microM monomer), whereas they were not detected when the haptoglobin level increased (34-70 microM monomer). Therefore haptoglobin, when circulating at enhanced levels with free Hb during the acute phase of inflammation, might protect ApoA-I structure and function against hydroxyl radicals.