12,024 research outputs found
An intracellular pH gradient in the anammox bacterium Kuenenia stuttgartiensis as evaluated by (31)P NMR
No full textThe cytoplasm of anaerobic ammonium oxidizing (anammox) bacteria consists of three compartments separated by membranes. It has been suggested that a proton motive force may be generated over the membrane of the innermost compartment, the “anammoxosome”. 31P nuclear magnetic resonance (NMR) spectroscopy was employed to investigate intracellular pH differences in the anammox bacterium Kuenenia stuttgartiensis. With in vivo NMR, spectra were recorded of active, highly concentrated suspensions of K. stuttgartiensis in a wide-bore NMR tube. At different external pH values, two stable and distinct phosphate peaks were apparent in the recorded spectra. These peaks were equivalent with pH values of 7.3 and 6.3 and suggested the presence of a proton motive force over an intracytoplasmic membrane in K.stuttgartiensis. This study provides for the second time—after discovery of acidocalcisome-like compartments in Agrobacterium tumefaciens—evidence for an intracytoplasmic pH gradient in a chemotrophic prokaryotic cell.BiotechnologyApplied Science
Investigating the evolutionary link between malaria and autoimmunity: a large scale immunogenetic study in two West African populations.
No full textAIM. Despite equivalent exposure to infection and comparable use of protective measures, the Fulani of West Africa have been shown to mount stronger immune responses to Plasmodium falciparum antigens and to be less susceptible to infection and mild disease than sympatric populations (Modiano et al. 1996, PNAS). The Fulani also show a higher response to other pathogens, and both their Th1 and Th2 responses are enhanced, suggesting that their resistance to malaria could result from a generally stronger immune activation. Key genes related to T regulatory cell function are indeed down-regulated in the Fulani (Torcia et al. 2008 PNAS). This disorder of immune homeostasis could be driven by genetic factors positively selected by P. falciparum and may underlie the higher susceptibility of the Fulani to diseases with autoimmune pathogenesis reported in the literature (Fish et al. 1987, Diabetologia; Mahe et al. 1996, Br J Dermatol; Brieger et al. 1997, Trop Med Int Health). The general aim of the proposed investigation is to explore the genetic basis of the lower susceptibility to malaria observed in the Fulani, and in particular to evaluate the role of autoimmunity loci. MATERIALS AND METHODS. To investigate this hypothesis, we conducted a large-scale epidemiological study in rural villages of Burkina Faso inhabited by Fulani, Mossi and Rimaibe communities. The field study lasted 2 years (2007-8) and consisted in a combination of cross sectional and longitudinal surveys. At each survey we collected parasitological (P. falciparum index and parasite density), clinical (fever, anemia, spleen size) and serological data (IgG levels against P. falciparum and self antigens). We genotyped 363 Single Nucleotide Polymorphisms (SNPs) on 2186 samples using the Sequenom System, based on allele-specific primer extension and MALDI-TOF Mass Spectrometry. SNPs included polymorphisms previously shown to be involved in resistance to severe malaria, in resistance to infection and/or in antibody production, as well as polymorphisms at autoimmunity loci. We conducted population genetic analyses and genetic association analysis with parasitological, clinical and serological phenotypes using the free software package R. RESULTS. Principal component analysis revealed that Mossi and Rimaibe (Non-Fulani) are not genetically distinct among themselves, whereas the Fulani are a clearly distinct group, in agreement with data obtained on HLA class I-II alleles (Modiano et al. 2001, Tissue Antigens; Lulli et al. 2009, Hum Immunol). We therefore compared allele frequencies and calculated Fst, a measure of population genetic differentiation, between Fulani and Non-Fulani. We observed that the proportion of autoimmunity SNPs with Fst>0.05 (indicating moderate/high differentiation and corresponding to at least a two-fold difference in allele frequency) is 20%, versus 10% shown by other loci (p=0.03). Genetic association analysis of susceptibility to infection and infection levels showed association signals among genes involved in resistance to severe malaria (TNF, DDC, ABO, IFNG-IL22, GNAS, MECP2, G6PD). Furthermore we observed strong signals of association, both in Fulani and Non-Fulani, in the 5q31 region of the genome, which has been previously linked to P. falciparum infection levels (Rihet et al. 1998, Am J Hum Genet; Mangano et al. 2008, Genes Immun). Finally, association signals were also observed among genes related to T regulatory cell function and/or involved in autoimmunity (TGFBR3, CD25, FCGR2A, CR1, IL1R1L-IL18RAP, IL1A-IL1B, IL21, BLK, ORMDL3, TGFB1). CONCLUSIONS. The results of our investigation support the hypothesis that malaria has exerted a selective pressure on the immune system and has affected is evolution, and provide evidence that common gene regulatory networks could underlie susceptibility to malaria and to immunological disorders such as autoimmune diseases
Profiling the Antibody Immune Response against Blood Stage Malaria Vaccine Candidates
No full textBACKGROUND: The complexity and diversity of the antibody immune response to the antigen repertoire of a pathogen has long been appreciated. Although it has been recognized that the detection of antibodies against multiple antigens dramatically improves the clinical sensitivity and specificity of diagnostic assays, the prognostic value of serum reactivity profiles against multiple microbial antigens in protection has not been investigated.
METHODS: Using malaria as a model we investigated whether antigen reactivity profiles in serum of children with different levels of clinical immunity to Plasmodium falciparum malaria correlated with protection. We developed a microarray immunoassay of 18 recombinant antigens derived from 4 leading blood-stage vaccine candidates for P. falciparum [merozoite surface protein 1 (MSP1), MSP2, MSP3, and apical membrane antigen (AMA)-1]. Associations between observed reactivity profiles and clinical status were sought using k-means clustering and phylogenetic networks.
RESULTS: The antibody immune response was unexpectedly complex, with different combinations of antigens recognized in different children. Serum reactivity to individual antigens did not correlate with immune status. By contrast, combined recognition of AMA-1 and allelic variants of MSP2 was significantly associated with protection against clinical malaria. This finding was confirmed independently by k-means clustering and phylogenetic networking.
CONCLUSIONS: The analysis of reactivity profiles provides a wealth of novel information about the immune response against microbial organisms that would pass unnoticed in analysis of reactivity to antigens individually. Extension of this approach to a large fraction of the proteome may expedite the identification of correlates of protection and vaccine development against microbial diseases
Investigating the genetic basis of the lower susceptibility to malaria shown by the Fulani of West-Africa.
No full textDespite equivalent exposure to infection and comparable use of protective measures, the Fulani of West Africa have been shown to mount stronger immune responses to Plasmodium falciparum antigens and to be less susceptible to infection and mild disease than sympatric populations. The Fulani also show a higher response to other pathogens, and both their Th1 and Th2 responses are enhanced, suggesting that their resistance to malaria could result from a generally stronger immune activation. Key genes related to T regulatory cell function are indeed down-regulated in the Fulani. This disorder of immune homeostasis could be driven by genetic factors positively selected by P. falciparum and may underlie the reported higher susceptibility of the Fulani to autoimmune diseases. In order to investigate the genetic basis of the lower susceptibility to malaria shown by the Fulani we conducted a large-scale epidemiological study in Burkina Faso consisting of a combination of cross-sectional and longitudinal surveys. We genotyped 363 Single Nucleotide Polymorphisms (SNPs) on 2186 samples, by Sequenom MassArray System. SNPs included polymorphisms previously shown to be involved in resistance to severe malaria, in resistance to infection or in antibody production (www.malariagen.net), as well as polymorphisms at autoimmunity loci. We will show results of: i) inter-ethnic comparison of malaria susceptibility phenotypes; ii) population genetics analysis; iii) genetic association analysis with parasitological, clinical and immunological phenotypes
Investigating the genetic basis of the Fulani’s lower susceptibility to malaria: the role of autoimmunity loci.
No full textDespite equivalent exposure to infection and comparable use of protective measures, the Fulani of West Africa have been shown to mount stronger immune responses to Plasmodium falciparum antigens and to be less susceptible to infection and mild disease than sympatric populations. The Fulani also show a higher response to other pathogens, and both their Th1 and Th2 responses are enhanced, suggesting that their resistance to malaria could result from a generally stronger immune activation. Key genes related to T regulatory cell function are indeed down-regulated in the Fulani. This disorder of immune homeostasis could be driven by genetic factors positively selected by P. falciparum and may underlie the higher susceptibility of the Fulani to diseases with autoimmune pathogenesis reported in the literature. The general aim of our investigation is to explore the genetic basis of the lower susceptibility to malaria observed in the Fulani, and in particular to evaluate the role of autoimmunity loci. We conducted a large-scale epidemiological study in rural villages of Burkina Faso inhabited by Fulani, Mossi and Rimaibe communities. The field study lasted 2 years (2007-8) and consisted in a combination of cross sectional and longitudinal surveys. At each survey we collected relevant parasitological and clinical data. Serological data (IgG levels against P. falciparum and self antigens) were generated by ELISA on plasma samples from the first survey. We genotyped 363 Single Nucleotide Polymorphisms (SNPs) on 2186 samples using the Sequenom System. Principal component analysis revealed that Mossi and Rimaibe (Non-Fulani) are not genetically distinct among themselves, whereas the Fulani are a clearly distinct group. We therefore compared allele frequencies and calculated Fst between Fulani and Non-Fulani. We observed that the proportion of autoimmunity SNPs with Fst>0.05 (indicating moderate/high differentiation and corresponding to at least a two-fold difference in allele frequency) is 20% versus 10% shown by other loci. Genetic association analysis of susceptibility to infection showed, both in Fulani and Non-Fulani, signals of association among genes: i) involved in resistance to severe malaria (ABO, DDC, G6PD, GNAS, IFNG-IL22, MECP2, TNF); ii) lying in the 5q31 region of the genome, which has been previously linked to P. falciparum infection levels (IRF1); iii) related to T regulatory cell function and/or involved in autoimmunity (BLK, CD25, CR1, FCGR2A, IL1A-IL1B, IL1R1L-IL18RAP, IL21, ORMDL3, TGFB1, TGFBR3). These results support the hypothesis that malaria has exerted a selective pressure on the immune system and has affected its evolution, and suggest that common gene regulatory networks could underlie susceptibility to malaria and to immunological disorders such as autoimmune diseases
Concept and development of an autonomous wearable micro-fluidic platform for real time pH sweat analysis
No full textIn this work the development of an autonomous, robust and wearable micro-fluidic platform capable of performing on-line analysis of pH in sweat is discussed. Through the means of an optical detection system based on a surface mount light emitting diode (SMD LED) and a light photo sensor as a detector, a wearable system was achieved in which real-time monitoring of sweat pH was performed during 55 minutes of cycling activity. We have shown how through systems engineering, integrating miniaturised electrical components, and by improving the micro-fluidic chip characteristics, the wearability, reliability and performance of the micro-fluidic platform was significantly improved
Ammonia cleaves polypeptides at asparagine proline bonds.
No full textPolypeptides that contain the sequence Asn-Pro undergo complete cleavage at this amide bond with ammonia. One cleavage product possesses Pro as the new amino terminus and the other Asn or isoAsn as the new C-terminus, the formation of the latter probably arising by way of a cyclic succinimide intermediate. Other Asn-X bonds where X = Tyr, Gln, Ile, Glu, Ala, Gly, Asn or Phe did not exhibit any peptide bond cleavage, whereas when X = Leu, Thr and Ser partial cleavage was observed. Asn residues not involved in chain-cleavage underwent deamidation to Asp as shown by MALDI-ToF mass spectrometry (MS) analysis. The partial conversion of in-chain Asp residues to isoAsp under the reaction conditions was inferred from RP-HPLC and MS analysis of reaction mixtures
Exploring the effect of the pH on the corrosion of multilayer nickel-chromium coatings
No full textThe impact of the pH on the corrosion of microporous nickel-chromium coatings has been explored at localised scale by Scanning Electrochemical Microscopy and validated by potentiodynamic polarisation measurements. Results not only reveal the correlation between both techniques but also enables to identify the different corrosion rate after increasing the electrolyte aggressiveness varying the pH. However, independently of the pH, a similar corrosion mechanism was determined: the cross-section micrographs (by Field Emission-Scanning Electron Microscope) have revealed an isotropic growth of the actives sites at early-stage corrosion as well as the attack of different nickel layers during the corrosion propagation.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Team Yaiza Gonzalez Garci
Il dibattito italiano su principi e clausole generale e l'ideale della certezza del diritto
No full textThis essay provides a critical assessment of the current Italian debate on general clauses and principles as set forth in a recent book edited by Giovanni D’Amico. The Author focuses on the role that legal certainty has played so far in this discussion and suggests that its impact on real life decisions and the functioning of the legal system has been greatly undervalued. The essay’s central argument attempts to demonstrate that, in the interpretation of general clauses and their translation into specific rules, the objective of legal certainty should be pursued and can ultimately be achieved
- …
