Place-exchange mechanism of Pt (111) oxidation/reduction as observed by synchrotron X-ray scattering

Structural changes in the Pt(111) single crystal surface associated with incipient electrochemical oxidation/reduction were studied by {ital in}{ital situ} synchrotron x-ray reflectivity. It was shown that lifting of Pt atoms of the surface layer occurs, substantiating the long-standing hypothesis of a place-exchange mechanism for solution/metal interface oxidation. It was also shown that, for a charge transfer of {approx_lt}1.7 e{sup -}/Pt atom, the initially flat surface structure could be recovered by electrochemical reduction. In constrast, the surface was irreversibly roughened for amounts of charge transfer exceeding {approx}1.7 e{sup -}/Pt, but the roughening involved only the atoms in the top layer of the original flat surface. A detailed mechanism is proposed for the place-exchange mechanism and the subsequent roughening of the electrode surface

P16-49. Broad types of cytokines secreted by Gag-specific T cells from HIV infected patients on HAART

International audiencen.

Signaling via interleukin-4, receptor alpha chain is required for successful vaccination against schistosomiasis in BALB/c mice

Radiation-attenuated (RA) schistosome larvae are potent stimulators of innate immune responses at the skin site of exposure (pinna) that are likely to be important factors in the development of Th1-mediated protective immunity. In addition to causing an influx of neutrophils, macrophages, and dendritic cells (DCs) into the dermis, RA larvae induced a cascade of chemokine and cytokine secretion following in vitro culture of pinna biopsy samples. While macrophage inflammatory protein 1 and interleukin-1 (IL-1) were produced transiently within the first few days, the Th1-promoting cytokines IL-12 and IL-18 were secreted at high levels until at least day 14. Assay of C3H/HeJ mice confirmed that IL-12 secretion was not due to lipopolysaccharide contaminants binding Toll-like receptor 4. Significantly, IL-12 p40 secretion was sustained in pinnae from vaccinated mice but not in those from nonprotected infected mice. In contrast, IL-10 was produced from both vaccinated and infected mice. This cytokine regulates IL-12-associated dermal inflammation, since in vaccinated IL-10/ mice, pinna thickness was greatly increased concurrent with elevated levels of IL-12 p40. A significant number of IL-12 p40 cells were detected as emigrants from in vitro-cultured pinnae, and most were within a population of rare large granular cells that were Ia, consistent with their being antigen-presenting cells. Labeling of IL-12 cells for CD11c, CD205, CD8, CD11b, and F4/80 indicated that the majority were myeloid DCs, although a proportion were CD11c F4/80, suggesting that macrophages were an additional source of IL-12 in the skin

Potential role of the EPEC Translocated intimin receptor (Tir) in host apoptotic events

Apoptosis, or programmed cell death, is a well-ordered process that allows damaged or diseased cells to be removed from an organism without severe inflammatory reactions. Multiple factors, including microbial infection, can induce programmed death and trigger reactions in both host and microbial cellular pathways. Whereas an ultimate outcome is host cell death, these apoptotic triggering mechanisms may also facilitate microbial spread and prolong infection. To gain a better understanding of the complex events of host cell response to microbial infection, we investigated the molecular role of the microorganism Enteropathogenic Escherichia coli (EPEC) in programmed cell death. We report that wild type strain of EPEC, E2348/69, induced apoptosis in cultured PtK2 and Caco-2 cells, and in contrast, infections by the intracellularly localized Listeria monocytogenes did not. Fractionation and concentration of EPEC-secreted proteins demonstrated that soluble protein factors expressed by the bacteria were capable of inducing the apoptotic events in the absence of organism attachment, suggesting adherence is not required to induce host cell death. Among the known EPEC proteins secreted via the Type III secretion (TTS) system, we identified the translocated intimin receptor (Tir) in the apoptosis-inducing protein sample. In addition, host cell ectopic expression of an EPEC GFP-Tir showed mitochondrial localization of the protein and produced apoptotic effects in transfected cells. Taken together, these results suggest a potential EPEC Tirmediated role in the apoptotic signaling cascade of infected host cells

P16-29. HIV Nef-specific T cells: Th1/CTL, Th2 and Th17 responses

International audiencen.

X-ray reflectivity studies of the metal/solution interphase

We have designed an electrochemical cell that permits x-ray scattering studies in a transmission geometry under in-situ electrochemical control and have performed x-ray specular reflectivity studies of several metal/solution interphases as a function of electrochemical potential. For the copper/solution interphase, we found that the reflectivity changes upon oxidation and reduction, indicating a phase transition between copper and copper oxide at the interphase. We also found that the thickness of the pure copper and the roughness of the interfaces exhibited electrochemical irreversibility that is consistent with the potentials for the oxidation waves in the anodic sweep and the reduction waves in the cathodic sweep of the voltammogram. A standard Fresnel expression for the x-ray specular reflectivity was applied in the data analysis, and a smoothly varying Lorentzian interface profile was used for the individual rough interfaces. Furthermore, an incoherent average was used to include the effect of correlated roughness between a pair of interfaces. Preliminary results are also presented for the silver/solution and platinum/solution interphases. 14 refs., 9 figs., 2 tabs

Are Elevated Levels of IGF-1 Caused by Coronary Arteriesoclerosis?: Molecular and Clinical Analysis

The importance of insulin-like growth factor-1 (IGF-1) in coronary artery disease (CAD) due to wide range of its biological effects and its therapeutic potential, has already been described. Our aim was to evaluate possible influence of IGF-1 serum level changes on coronary atherosclerosis. In case of existence of such association our further aim was to verify and explain this phenomenon by examination of promoter P1 of IGF-1gene and receptor gene for IGF-1. The study was performed in 101 consecutive patients undergo for routine coronary angiography. Quantitative and qualitative assessment of coronary atherosclerosis was performed respectively by estimation of the number of culprit lesions in coronary arteries and by Gensini score calculation. IGF-1, IGFBP3 and plasma lipoproteins were measured in all patients. In addition, we evaluated DNA from 101 patients, isolated from blood cells, which was amplified by using PCR with sophisticated primers for P1 promoter of IGF-1 gene and IGF-1 receptor gene, then analyzed utilizing SSCP technique and automatically sequenced. We observed significant increase of serum IGF-1 levels in patients with “3 vessel disease” and with high score in Gensini scale when compared to those without any narrowing lesions in coronary arteries and 0 Gensini score (in group with 3 vessel disease 215.0 ± 71.3 versuss 176.7 ± 34.2 ng/ml p = 0.04 and with high Gensini score 231.4 ± 59.3 versus 181.0 ± 37.8 ng/ml p = 0.01).We found different genotypes for five P1 promoter polymorphisms of IGF-1 gene (RS35767, RS5742612, RS228837, RS11829693, RS17879774). There were no significant associations between the observed single nucleotide polymorphism (SNP) and coronary atherosclerosis nor with levels of circulating IGF-1. We found no structural polymorphism in receptor gene for IGF-1 nor in its extracellular domain(exon 2–4) nor in internal domain (exon 16–21). The effect of increased IGF-1 serum level in our study was probably independent from structural polymorphism in promoter P1 for IGF-1 or in receptor gene for IGF-1