Decreased lesion formation in CCR2-/- mice reveals a role for chemokines in the initiation of atherosclerosis

Chemokines are proinflammatory cytokines that function in leukocyte chemoattraction and activation and have recently been shown to block the HIV-1 infection of target cells through interactions with chemokine receptors. In addition to their function in viral disease, chemokines have been implicated in the pathogenesis of atherosclerosis. Expression of the CC chemokine monocyte chemoattractant protein-1 (MCP-1) is upregulated in human atherosclerotic plaques, in arteries of primates on a hypercholesterolaemic diet; and in vascular endothelial and smooth muscle cells exposed to minimally modified lipids. To determine whether MCP-1 is causally related to the development of atherosclerosis, we generated mice that lack CCR2, the receptor for MCP-1 (ref. 7), and crossed them with apolipoprotein (apo) E-null mice which develop severe atherosclerosis. Here we show that the selective absence of CCR2 decreases lesion formation markedly in apoE-/- mice but has no effect on plasma lipid or lipoprotein concentrations. These data reveal a role for MCP-1 in the development of early atherosclerotic lesions and suggest that upregulation of this chemokine by minimally oxidized lipids is an important link between hyperlipidaemia and fatty streak formation.     

Modification of sticholysin II hemolytic activity by free radicals

Sticholysin II is a highly hemolytic toxin present in the caribbean sea anemone Stichodactyla helianthus. Pre-incubation of St II with 2,2'-azobis(2-amidinopropane), a source of peroxyl radicals in air saturated solution, readily reduces its hemolytic activity. Analysis of the amino acids present in the protein after its modification shows that only tryptophan groups are significantly modified by the free radicals. According to this, the loss of hemolytic activity correlates with the loss of the protein intrinsic fluorescence. The results indicate that, at high toxin concentrations, nearly a tryptophan residue and 0.2 toxin molecules are inactivated by each radical introduced into the system. Association of St II to multilamellar liposomes (egg yolk phosphatidyl choline:sphingomyelin 1:1) increases the toxin intrinsic fluorescence, indicating a more hydrophobic average environment of the five tryptophan groups of the protein. In agreement with this, incorporation of St II to the liposomes reduces the rate of fluorescence loss during its modification by free radicals, particularly at long incubation times. These results are explained in terms of two populations of tryptophans that are quenched at different rates by acrylamide and whose rates of inactivation by free radicals are also different.     

Amphiphilic alpha-helices are important structural motifs in the alpha and beta peptides that constitute the bacteriocin lactococcin G--enhancement of helix formation upon alpha-beta interaction

Lactococcin G (LcnG) is an antimicrobial substance (bacteriocin) consisting of two peptides, LcnG-alpha and LcnG-beta. The structures of intact LcnG-alpha and LcnG-beta as well as various fragments of these peptides were studied by circular dichroism (CD) under several conditions. All peptides had a non-structured conformation in aqueous solutions. In the presence of trifluoroethanol, dodecylphosphocholine micelles and (negatively charged) dioleoylglycerophosphoglycerol (Ole2GroPGro) liposomes, varying amounts of alpha-helical structure were induced. Comparisons of the various fragments showed that helicity was concentrated in those parts of LcnG-alpha and LcnG-beta that would become amphiphilic if an alpha-helical structure was adopted. In the presence of zwitterionic dioleoylglycerophosphocholine (Ole2GroPCho) liposomes, the peptides were much less (if at all) structured, suggesting that the excess of positive charge on the antimicrobial peptides needs to be compensated by an excess of negative charge on the membrane. The structuring of LcnG-alpha and LcnG-beta in the presence of Ole2GroPGro liposomes was considerably enhanced when both peptides were presented simultaneously to the membranes. Consecutive addition of the two peptides to Ole2GroPGro liposomes did not give this additional structuring, indicating that the individual LcnG-alpha and LcnG-beta peptides associate with the membrane in a virtually irreversible manner that makes them inaccessible for interaction with the complementary peptide. The results suggest that upon arrival at and interaction with the target membrane, LcnG-alpha and LcnG-beta form a complex that consists of approximately 50% amphiphilic alpha-helices.     

Cigarette smoking as a determinant of high-grade carotid artery stenosis in Hispanic, black, and white patients with stroke or transient ischemic attack

The effect of chitin, poly-beta-(1 --> 4)-N-acetyl-glucosamine, and chitosan, a polymer of glucosamine obtained by the deacetylation of chitin, on growth and nutrient digestibility was studied in grass shrimp, Penaeus monodon. Shrimp were fed for 8 wk diets containing no supplement (control) or 2, 5 or 10 g/100 g chitin or chitosan. Each diet was fed to triplicate groups of shrimp with a mean initial body weight of 0.45 +/- 0.05 g. Significantly higher body weight gains were observed in shrimp fed the 5% chitin diet than in those fed the 10% chitin or the control diet. The weight gain of shrimp decreased as dietary chitosan supplementation level increased (r = 0. 87, P < 0.05). Feed efficiencies (FE) and protein efficiency ratios (PER) followed the same pattern. Lower protein and lipid digestibilities and lower body protein and lipid contents were observed in shrimp fed all chitosan-containing diets than in controls (P < 0.05). Carbohydrate digestibility was lower in shrimp fed the 10% chitosan diet than in those fed the control diet. Lower protein and lipid digestibilities, body lipid content and blood cholesterol concentration were observed in shrimp fed the 10% chitin diet compared with controls (P < 0.05). Higher weight gains, body lipid contents and blood cholesterol concentrations were observed in shrimp fed the 2 and 5% chitin diets than in those fed the chitosan diets. Shrimp fed the 5% chitin diet had higher protein and lipid digestibilities and higher body protein content than those fed the 5% chitosan diet (P < 0.05). These data suggest that dietary chitin, supplemented at 5%, enhances P. monodon growth, whereas chitosan depresses shrimp growth, regardless of the supplementation level.     

Experience in conducting course exams on assignments in test form

Analysis of the results of examinations in oral surgery making use of tests in 319 fourth-year students showed that such a method of assessing students' knowledge is highly objective.