Tuning the 4f-state occupancy of cerium in highly correlated CeSi/ Fe multilayers: a study by x-ray absorption spectroscopy

Spectra of x-ray absorption and magnetic circular dichroism were measured at M4,5(3d) and L2,3(2p) edges of Ce in multilayers [Ce(1-x)Six/Fe]xn, with x between 0.1 and 0.65. The study uncovers the highly correlated nature of this layered system. An alpha-phase like electronic configuration of Ce is observed, with ordered magnetic moments on the 4f and 5d electrons induced by the interaction with Fe. Increasing the Si content reduces the strength of the hy-bridization between the 4f and conduction-band states which is reflected in a growing occupation and magnetic polarization of the 4f states. Variations of the shape and intensity of the L2,3-edge dichroism spectra, discussed in a simple phenomenological model, show the importance of the exchange interaction between the Ce-4f and 5d electrons, spin polarized by the interaction with Fe at the interfaces, for the electronic structure of Ce at high Si concentration and low temperature. A model of the band structure of rare-earth transition-metal compounds permits to argue that magnetic order on the Ce 4f electrons in the multilayers is due to different mechanisms: to hybridization of the Ce-4f with the Fe-3d states at low Si concentration and to intra-atomic 4f-5d exchange at high Si concentration. This is at variance with magnetic order in the intermetallics CeSi2-delta and CeSi which results from interaction between the localized 4f magnetic moments mediated by the Si-derived (s,p) conduction electrons, in competition with the Kondo effect.Comment: 31 pages, 9 figures, submitted to Phys. Rev.

An asymptotic form of the reciprocity theorem with applications in x-ray scattering

The emission of electromagnetic waves from a source within or near a non-trivial medium (with or without boundaries, crystalline or amorphous, with inhomogeneities, absorption and so on) is sometimes studied using the reciprocity principle. This is a variation of the method of Green's functions. If one is only interested in the asymptotic radiation fields the generality of these methods may actually be a shortcoming: obtaining expressions valid for the uninteresting near fields is not just a wasted effort but may be prohibitively difficult. In this work we obtain a modified form the reciprocity principle which gives the asymptotic radiation field directly. The method may be used to obtain the radiation from a prescribed source, and also to study scattering problems. To illustrate the power of the method we study a few pedagogical examples and then, as a more challenging application we tackle two related problems. We calculate the specular reflection of x rays by a rough surface and by a smoothly graded surface taking polarization effects into account. In conventional treatments of reflection x rays are treated as scalar waves, polarization effects are neglected. This is a good approximation at grazing incidence but becomes increasingly questionable for soft x rays and UV at higher incidence angles. PACs: 61.10.Dp, 61.10.Kw, 03.50.DeComment: 19 pages, 4 figure

CD209 in inflammatory bowel disease: a case-control study in the Spanish population

<p>Abstract</p> <p>Background</p> <p>The etiology of Ulcerative Colitis (UC) and Crohn's Disease (CD), considered together as Inflammatory Bowel Diseases (IBD), involves environmental and genetic factors. Although some genes are already known, the genetics underlying these diseases is complex and new candidates are continuously emerging. The <it>CD209 </it>gene is located in a region linked previously to IBD and a <it>CD209 </it>functional polymorphism (rs4804803) has been associated to other inflammatory conditions. Our aim was to study the potential involvement of this <it>CD209 </it>variant in IBD susceptibility.</p> <p>Methods</p> <p>We performed a case-control study with 515 CD patients, 497 UC patients and 731 healthy controls, all of them white Spaniards. Samples were typed for the <it>CD209 </it>single nucleotide polymorphism (SNP) rs4804803 by TaqMan technology. Frequency comparisons were performed using χ²tests.</p> <p>Results</p> <p>No association between <it>CD209 </it>and UC or CD was observed initially. However, stratification of UC patients by <it>HLA-DR3 </it>status, a strong protective allele, showed that carriage of the <it>CD209</it>_G allele could increase susceptibility in the subgroup of <it>HLA-DR3</it>-positive individuals (p = 0.03 OR = 1.77 95% CI 1.04–3.02, <it>vs. </it>controls).</p> <p>Conclusion</p> <p>A functional variant in the <it>CD209 </it>gene, rs4804803, does not seem to be influencing Crohn's disease susceptibility. However, it could be involved in the etiology or pathology of Ulcerative Colitis in <it>HLA-DR3</it>-positive individuals but further studies are necessary.</p

Quantification of HLA class I molecules on renal cell carcinoma using Edman degradation

<p>Abstract</p> <p>Background</p> <p>Unimpaired HLA class I antigen presentation is a prerequisite for the recognition of tumor cells by cytotoxic T lymphocytes and thus essential for the success of anticancer immunotherapeutic concepts. Several approaches have been taken in the immunotherapy of metastatic renal cell carcinoma (RCC), however of limited success. HLA loss or down-regulation have often been reported and might interfere with immunotherapeutic approaches aimed at the recognition of HLA-presented peptides.</p> <p>Methods</p> <p>We employed a quantitative method of molecular analysis for the comparison of HLA amounts on primary tumor, normal kidney and metastases of RCC, using Edman degradation. We analyzed a series of 47 RCC samples including corresponding renal parenchyma, local lymph node metastases and distant metastases.</p> <p>Results</p> <p>Results of quantitative Edman degradation revealed significantly higher HLA yields on primary tumor and metastases compared to normal kidney tissue. This effect was shown not to result from infiltrating immune cells, since tumor-infiltrating lymphocytes had no influence on the overall HLA recovery from tumor tissue. Unexpectedly, we found a higher amount of HLA class I molecules on distant metastases compared to local lymph node metastases.</p> <p>Conclusion</p> <p>Edman degradation allows the direct quantitative comparison of HLA class I protein expression by tumor or normal tissue and metastases of RCC patients. Our results raise hopes for improving the success and effectiveness of future immunotherapeutic concepts for metastatic RCC.</p

Is Aboriginal Food Less Allergenic? Comparing IgE-Reactivity of Eggs from Modern and Ancient Chicken Breeds in a Cohort of Allergic Children

BACKGROUND: Hen's egg allergy ranks among the most frequent primary food allergies in children. We aimed to investigate sensitization profiles of egg allergic patients and compare in vitro IgE reactivities of eggs from ancient chicken breeds (Araucana and Maran) with those from conventional laying hen hybrids. METHODOLOGY: Egg allergic children (n = 25) were subjected to skin prick test, double blind placebo controlled food challenge, and sensitization profiles to Gal d 1-5 were determined by allergen microarray. IgE binding and biological activity of eggs from different chicken breeds were investigated by immunoblot, ELISA, and mediator release assays. PRINCIPAL FINDINGS: We found that Gal d 1 and Gal d 2 are generally major egg allergens, whereas Gal d 3-5 displayed high sensitization prevalence only in patients reacting to both, egg white and yolk. It seems that the onset of egg allergy is mediated by egg white allergens expanding to yolk sensitization in later stages of disease. Of note, egg white/yolk weight ratios were reduced in eggs from Auraucana and Maran chicken. As determined in IgE immunoblots and mass analysis, eggs from ancient chicken breeds did not differ in their protein composition. Similar IgE-binding was observed for all egg white preparations, while an elevated allergenicity was detected in egg yolk from Araucana chicken. CONCLUSION/SIGNIFICANCE: Our results on allergenicity and biological activity do not confirm the common assumption that aboriginal food might be less allergenic. Comprehensive diagnosis of egg allergy should distinguish between reactivity to hen's egg white and yolk fractions to avoid unnecessary dietary restrictions to improve life quality of the allergic child and its family

Differential association of two PTPN22 coding variants with Crohn’s disease and ulcerative colitis

2 páginas.-- Póster presentado al 5º European Workshop on Immune-Mediated Inflammatory Diseases celebrado en Sitges (Barcelona) dxel 1 al 3 de Diciembre de 2010.-- et al.The PTPN22 gene is an important risk factor for human autoimmunity. Two PTPN22 missense-SNPs, both with functional influence, the R620W (1858C>T, rs2476601) in exon 14 and the R263Q (788G>A, rs33996649) in exon 10 have been associated with autoimmune diseases [1-4].Peer reviewe

CD40: Novel Association with Crohn's Disease and Replication in Multiple Sclerosis Susceptibility

Background: A functional polymorphism located at 21 from the start codon of the CD40 gene, rs1883832, was previously reported to disrupt a Kozak sequence essential for translation. It has been consistently associated with Graves’ disease risk in populations of different ethnicity and genetic proxies of this variant evaluated in genome-wide association studies have shown evidence of an effect in rheumatoid arthritis and multiple sclerosis (MS) susceptibility. However, the protective allele associated with Graves’ disease or rheumatoid arthritis has shown a risk role in MS, an effect that we aimed to replicate in the present work. We hypothesized that this functional polymorphism might also show an association with other complex autoimmune condition such as inflammatory bowel disease, given the CD40 overexpression previously observed in Crohn’s disease (CD) lesions. Methodology: Genotyping of rs1883832C.T was performed in 1564 MS, 1102 CD and 969 ulcerative colitis (UC) Spanish patients and in 2948 ethnically matched controls by TaqMan chemistry. Principal Findings: The observed effect of the minor allele rs1883832T was replicated in our independent Spanish MS cohort [p= 0.025; OR (95% CI)= 1.12 (1.01–1.23)]. The frequency of the minor allele was also significantly higher in CD patients than in controls [p= 0.002; OR (95% CI)= 1.19 (1.06–1.33)]. This increased predisposition was not detected in UC patients [p= 0.5; OR (95% CI)= 1.04 (0.93–1.17)]. Conclusion: The impact of CD40 rs1883832 on MS and CD risk points to a common signaling shared by these autoimmune conditions.Peer reviewe

Preliminary molecular genetic analysis of the Receptor Interacting Protein 140 (RIP140) in women affected by endometriosis

BACKGROUND: Endometriosis is a complex disease affecting 10–15% of women at reproductive age. Very few genes are known to be altered in this pathology. RIP140 protein is an important cofactor of oestrogen receptor and many other nuclear receptors. Targeting disruption experiments of nrip1 gene in mice have demonstrated that nuclear receptor interacting protein 1 gene (nrip1), the gene encoding for rip140 protein, is essential for female fertility. Specifically, mice null for nrip1 gene are viable, but females are infertile because of complete failure of mature follicles to release oocytes at ovulation stage. The ovarian phenotype observed in mice devoid of rip140 closely resembles the luteinized unruptured follicle (LUF) syndrome that is observed in a high proportion of women affected of endometriosis or idiopathic infertility. Here we present a preliminary work that analyses the role of NRIP1 gene in humans. METHODS: We have sequenced the complete coding region of NRIP1 gene in 20 unrelated patients affected by endometriosis. We have performed genetic association studies by using the DNA variants identified during the sequencing process. RESULTS: We identified six DNA variants within the coding sequence of NRIP1 gene, and five of them generated amino acid changes in the protein. We observed that three of twenty sequenced patients have specific combinations of amino-acid variants within the RIP140 protein that are poorly represented in the control population (p = 0.006). Moreover, we found that Arg448Gly, a common polymorphism located within NRIP1 gene, is associated with endometriosis in a case-control study (59 cases and 141 controls, p(allele positivity test )= 0.027). CONCLUSION: Our results suggest that NRIP1 gene variants, separately or in combinations, might act as predisposing factors for human endometriosis

Mutation analysis of genes that control the G1/S cell cycle in melanoma: TP53, CDKN1A, CDKN2A, and CDKN2B

BACKGROUND: The role of genes involved in the control of progression from the G1 to the S phase of the cell cycle in melanoma tumors in not fully known. The aim of our study was to analyse mutations in TP53, CDKN1A, CDKN2A, and CDKN2B genes in melanoma tumors and melanoma cell lines METHODS: We analysed 39 primary and metastatic melanomas and 9 melanoma cell lines by single-stranded conformational polymorphism (SSCP). RESULTS: The single-stranded technique showed heterozygous defects in the TP53 gene in 8 of 39 (20.5%) melanoma tumors: three new single point mutations in intronic sequences (introns 1 and 2) and exon 10, and three new single nucleotide polymorphisms located in introns 1 and 2 (C to T transition at position 11701 in intron 1; C insertion at position 11818 in intron 2; and C insertion at position 11875 in intron 2). One melanoma tumor exhibited two heterozygous alterations in the CDKN2A exon 1 one of which was novel (stop codon, and missense mutation). No defects were found in the remaining genes. CONCLUSION: These results suggest that these genes are involved in melanoma tumorigenesis, although they may be not the major targets. Other suppressor genes that may be informative of the mechanism of tumorigenesis in skin melanomas should be studied