Structural and dynamical surface properties of phosphatidylethanolamine containing membranes.

The hydration of solid dimyristoylphosphatidylethanolamine (DMPE) produces a negligible shift in the asymmetric stretching frequency of the phosphate groups in contrast to dimyristoylphosphatidylcholine (DMPC). This suggests that the hydration of DMPE is not a consequence of the disruption of the solid lattice of the phosphate groups as occurs in DMPC. The strong lateral interactions between NH(3) and PO(2)(-) groups present in the solid PEs remain when the lipids are fully hydrated and seem to be a limiting factor for the hydration of the phosphate group hindering the reorientation of the polar heads. The lower mobility is reflected in a higher energy to translocate the phosphoethanolamine (P-N) dipoles in an electrical field. This energy is decreased in the presence of increasing ratios of PCs of saturated chains in phosphoethanolamine monolayer. The association of PC and PE in the membrane affecting the reorientation of the P-N groups is dependent of the chain-chain interaction. The dipole potentials of PCs and PEs mixtures show different behaviors according to the saturation of the acyl chain. This was correlated with the area in monolayers and the hydration of the P-N groups. In spite of the low hydration, DMPE is still able to adsorb fully hydrated proteins, although in a lower rate than DMPC at the same surface pressure. This indicates that PE interfaces possess an excess of surface free energy to drive protein interaction. The relation of this free energy with the low water content is discussed.

Effects of mud-pack treatment on plasma cytokine and soluble adhesion molecule levels in healthy volunteers.

BACKGROUND: The suggested hypothesis of a direct anti-inflammatory property of mud-pack treatment has led us to speculate that its action on the cytokine network might counteract the heat-stress-related effects on platelet and endothelial cell function often reported following hot-spring baths. Therefore, the present study was designed to investigate the effects of a cycle of 12 daily mud-pack treatments on bio-humoral markers of inflammation, as well as on markers of in vivo platelet and/or endothelial cell activation, in plasma samples obtained from healthy volunteers. METHODS: Blood samples were obtained before (T(0)), at the end of the first treatment (T(1)) and after a cycle of 12 daily mud-pack treatments (T(2)). Plasma cytokines (TNF-alpha IL-1beta, and IL-6) and adhesion molecules (sP-selectin, sE-selectin and sVCAM) levels, as well as hematocrit and complete and differential blood cell counts were determined at every time point. RESULTS: Plasma sP-selectin levels were not modified during treatment, as were not sE-selectin or sVCAM. Similarly, IL-1beta and TNF-alpha levels were unchanged through a 12 daily mud-pack treatment. Conversely, plasma IL-6 levels were significantly lowered at the end of a 20-min 47 degrees C mud-pack treatment (p<0.01). CONCLUSIONS: The lack of effects on in vivo platelet and/or endothelial cell activation suggests that hot mud-pack treatment might be used as a relatively safe procedure in patients with atherothrombotic disorders.

n-3 PUFA supplementation, monocyte PCA expression and interleukin-6 production.

n-3 polyunsaturated fatty acids (PUFA) can affect several monocyte functions and the biochemistry of blood cells, thus possibly influencing the initiation of thrombosis, inflammatory disease and atherosclerosis. In this study, we have investigated the effect of dietary supplementation with n-3 PUFA ethyl esters on procoagulant activity (PCA) and interleukin-6 (IL-6) production by human mononuclear cells. Nine healthy volunteers received 4 g/d of n-3 PUFA ethyl esters (4 x 1 g capsules with at least 85% eicosapentaenoic + docosahexaenoic acid ethyl esters) for 18 weeks. Before and at the end of the treatment, mononuclear cells were obtained from peripheral citrated blood by Ficoll-Hypaque density gradient centrifugation. Cellular suspensions (10(7) cells/ml) were incubated at 37 degrees C for 4 h in the absence and presence of lipopolysaccharide (10 micrograms/ml); PCA was determined by one-stage clotting assay and IL-6 concentrations were assayed in supernatants by specific ELISA. After 18-week treatment, both unstimulated and stimulated monocyte PCA were significantly reduced by 66% and 63%, respectively (P < 0.01). Similarly, a significant inhibitory effect by n-3 PUFA treatment on basal and LPS-stimulated IL-6 monocyte production was observed (50% and 46%, respectively, P < 0.05). These data indicate that 18-week n-3 PUFA supplementation may influence monocyte activities, which play a specific role in atherosclerosis and its thrombotic complications.

Investigation of intra-domain and inter-domain interactions of glutathione transferase P1-1 by limited chymotryptic cleavage.

Limited proteolysis of glutathione transferase P1-1 (GSTP1-1) by chymotrypsin performed at 20 degrees and 30 degrees C mainly generates two complementary peptides of 17 kDa and 6 kDa molecular mass with concomitant loss of catalytic capacity. Sequence analysis of these peptides showed that the peptide bond between Tyr47 and Gly48 was cleaved. The analysis of the recently resolved three-dimensional structure of GSTP1-1 [Reinemer, P., Dirr, H. W., Ladenstein, R., Huber, R., Lo Bello, M., Federici, G. & Parker, M. W. (1992) J. Mol. Biol. 227, 214-226] suggests that the proteolytically cleaved bond results located in a portion of the polypeptide chain lining the G-site which has been demonstrated to be part of an exposed and flexible region of the N-terminal domain (structural elements alpha B1 and alpha B2) [Aceto, A., Caccuri, A. M., Sacchetta, P., Bucciarelli, T., Dragani, B., Rosato, N., Federici, G. & Di Ilio, C. (1992) Biochem. J. 285, 241-245]. The fragments which are generated by proteolysis at 20 degrees C, remain linked by noncovalent interaction in a complex (nicked GSTP1-1) which is dissociated by incubation at higher temperatures. As shown by circular dichroic analysis, although inactive, nicked GSTP1-1 retains an overall secondary structure closely resembling that of the parent enzyme. However, the fluorescence data of the nicked GSTP1-1 indicate that the Trp38, which is near the chymotrypsin-cleavable bond, becomes exposed in a more polar environment. This indicates that, in the nicked enzyme, the polypeptide portion containing the structural elements alpha B1 and alpha B2 has more freedom of fluctuation. The fact that this polypeptide chain portion contains two essential amino acid residues of the G-site (Trp38 and Lys42) might account for the loss of ability to bind glutathione by the nicked enzyme which is consequently catalytically inactive. Proteolysis performed at 30 degrees C generated a homodimeric 17-kDa fragment. The structural analysis of this fragment suggests that the GSTP1-1 alpha C helix, which is located in the domain I and is thought to be involved in the inter-domain interaction, could exert a critical role in maintaining the native folding of domain II.

Effect of selenium on the contractile force of isolated and perfused guinea-pig heart.

Sodium selenite showed a negative inotropic effect on isolated and perfused guinea-pig heart. The effect was dose-dependent and was not reversed by a higher calcium concentration or by washing. Electronic microscopy revealed mitochondrial alterations. Pyruvate and lactate 2 X 10(-3)M seemed able to reverse the negative inotropic effect and mitochondrial alterations induced by sodium selenite.