Identification of the precursor of (S)-3-methyl-3-sulfanylhexan-1-ol, the sulfury malodour of human axilla sweat

A careful study of human axillary microflora led us to the identification of a new strain of Staphylococcus haemolyticus. The role in axillary malodour formation of this microorganism was compared to those of Corynebacterium xerosis and Staphylococcus epidermidis, upon incubation on sterile human eccrine and apocrine axilla sweat. St. haemolyticus was responsible for the strongest sulfury malodour and the generation of the volatile sulfur compound (VSC) (S)-3-methyl-3-sulfanylhexan-1-ol (3). In this study, we investigated the nonvolatile precursors of VSCs. Human axillary sweat was collected, fractionated and analysed by HPLC/APCI-MS (High-Pressure Liquid Chromatography coupled to Atmospheric Pressure Chemical Ionisation Mass Spectrometry). The precursor of 3 was identified as [1-(2-hydroxyethyl)-1-methylbutyl]-L-cysteinylglycine (Cys-Gly-(S)-conjugate; 12). Because Cys-Gly-(S)-conjugates are key intermediates in the glutathione biodetoxification pathway, other derivatives of 12, specifically glutathione-(S)-conjugate 11 and Cys-(S)-conjugate 13, were prepared. Compounds 11 and 13 were not detected by HPLC/MS of sterile sweat. Synthetic homologues 11, 12, and 13 were incubated with C. xerosis, St. heamolyticus, and St. epidermidis. We observed efficient conversion of precursors 12 and 13 to form VSCs when incubated with St. haemolyticus, with a clear preference for 12. C. xerosis and St. epidermidis were less efficient in cleaving Cys-Gly-(S)-conjugate 12 to form the corresponding thiol 3. Incubation of glutathione-(S)-conjugate 11 never led to the formation of 3 under the experimental conditions employed.     

Modulation of the host immune response by a transient intracellular stage of Mycobacterium ulcerans: the contribution of endogenous mycolactone toxin

Mycobacterium ulcerans (Mu), the aetiological agent of Buruli ulcer, is an extracellular pathogen producing the macrolide toxin mycolactone. Using a mouse model of intradermal infection, we found that Mu was initially captured by phagocytes and transported to draining lymph nodes (DLN) within host cells. Similar to Buruli ulcers in humans, the infection site eventually became ulcerated with tissue necrosis and extracellular bacteria, at later stages. In contrast to Mycobacterium bovis BCG (BCG), Mu did not disseminate to the spleen. However, mice infected with Mu or BCG developed comparable primary cellular responses to mycobacterial antigens in DLN and spleen. The role of mycolactone in this sequence of events was examined with a mycolactone-deficient (mup045) mutant of Mu. Mup045 bacilli were better internalized than wild-type (wt) bacteria by mouse phagocytes in vitro. Moreover, infection with wt but not mup045 Mu led to inhibition of TNF-alpha expression, upregulation of MIP-2 chemokine, and host cell death within 1 day. Our results suggest that mycolactone expression during the intracellular life of Mu may contribute to immune evasion by inhibiting phagocytosis, provoking apoptosis of antigen presenting cells and altering the establishment of an appropriate inflammatory reaction.     

Algorithm for identifying and separating beats from arterial pulse records

Background  

This project was designed as an epidemiological aid-selecting tool for a small country health center with the general objective of screening out possible coronary patients. Peripheral artery function can be non-invasively evaluated by impedance plethysmography. Changes in these vessels appear as good predictors of future coronary behavior. Impedance plethysmography detects volume variations after simple occlusive maneuvers that may show indicative modifications in arterial/venous responses. Averaging of a series of pulses is needed and this, in turn, requires proper determination of the beginning and end of each beat. Thus, the objective here is to describe an algorithm to identify and separate out beats from a plethysmographic record. A secondary objective was to compare the output given by human operators against the algorithm.     

Strong inbreeding depression in a Daphnia metapopulation

The deleterious effects of inbreeding have long been known, and inbreeding can increase the risk of extinction for local populations in metapopulations. However, other consequences of inbreeding in metapopulations are still not well understood. Here we show the presence of strong inbreeding depression in a rockpool metapopulation of the planktonic freshwater crustacean Daphnia magna, which reproduces by cyclical parthenogenesis. We conducted three experiments in real and artificial rockpools to quantify components of inbreeding depression in the presence and the absence of competition between clonal lines of selfed and outcrossed genotypes. In replicated asexual populations, we recorded strong selection against clones produced by selfing in competition with clones produced by outcrossing. In contrast, inbreeding depression was much weaker in single-clone populations, that is, in the absence of competition between inbred and outbred clones. The finding of a competitive advantage of the outbred genotypes in this metapopulation suggests that if rockpool populations are inbred, hybrid offspring resulting from crosses between immigrants and local genotypes might have a strong selective advantage. This would increase the effective gene flow in the metapopulation. However, the finding of low inbreeding depression in the monoclonal populations suggests that inbred and outbred genotypes might have about equal chances of establishing new populations.     

Aotus monkeys: their great value for anti-malaria vaccines and drug testing

Non-human primates represent a valuable resource for testing potential vaccines candidates and drugs for human use. Malaria remains one of the greatest burdens for the humanity represented by approximately 500 million new clinical cases per year worldwide and at least two million deaths caused annually. Additional control measures such as vaccines and new anti-malarial compounds are therefore urgently needed. Safety and protective efficacy studies in animal models are critical steps for vaccines and drugs development and primate models are probably the most appropriate for this purpose. Although Aotus genus provides several species susceptible to both Plasmodium falciparum and Plasmodium vivax, having different susceptibility to malaria, Aotus lemurinus griseimembra represents the best current malaria primate model because of its high susceptibility to infection by blood forms and sporozoites of both species of Plasmodium. Although the ultimate validation of this model depends upon human trials, over the past two decades these monkeys have proved very useful to test multiple malaria vaccine candidates prior to trials in humans. A good correlation between the B- and T-cell epitopes recognised by humans and by immunised monkeys has been documented, and cross reactivity between reagents for human and Aotus cytokines and lymphocyte markers have been identified and are facilitating the selection of vaccine candidates for clinical trials. Aotus also represents a good model for the screening of anti-malarial drugs and the understanding of malaria pathogenesis as well. In view of the decreasing availability of these primates, breeding programs and biomedical research facilities must be improved in countries of primate origin.     

Arsenic trioxide promotes histone H3 phosphoacetylation at the chromatin of CASPASE-10 in acute promyelocytic leukemia cells

Arsenic trioxide (As(2)O(3)) is highly effective for the treatment of acute promyelocytic leukemia, even in patients who are unresponsive to all-trans-retinoic acid therapy. As(2)O(3) is believed to function primarily by promoting apoptosis, but the underlying molecular mechanisms remain largely unknown. In this report, using cDNA arrays, we have examined the changes in gene expression profiles triggered by clinically achievable doses of As(2)O(3) in acute promyelocytic leukemia NB4 cells. CASPASE-10 expression was found to be potently induced by As(2)O(3). Accordingly, caspase-10 activity also substantially increased in response to As(2)O(3) treatment. A selective inhibitor of caspase-10, Z-AEVD-FMK, effectively blocked caspase-3 activation and significantly attenuated As(2)O(3)-triggered apoptosis. Interestingly, the treatment of NB4 cells with As(2)O(3) markedly increased histone H3 phosphorylation at serine 10, an event that is associated with acetylation of the lysine 14 residue. Chromatin immunoprecipitation assays revealed that As(2)O(3) potently enhances histone H3 phosphoacetylation at the CASPASE-10 locus. These results suggest that the effect of As(2)O(3) on histone H3 phosphoacetylation at the CASPASE-10 gene may play an important role in the induction of apoptosis and thus contribute to its therapeutic effects on acute promyelocytic leukemia.     

Role of an intact splenic microarchitecture in early lymphocytic choriomeningitis virus production

An acute infection with lymphocytic choriomeningitis virus (LCMV) is efficiently controlled by the cytotoxic-T-cell (CTL) response of the host, and LCMV titers in the spleen and peripheral solid organs usually fall sharply after day 4 to 6 postinfection. Surprisingly, infection of immunodeficient recombination-activating gene 2-deficient (RAG2-/-) mice with 5 x 10(2) PFU of LCMV-WE causes about 80-fold-lower LCMV titers in the spleen on day 4 postinfection compared with C57BL/6 control mice. This could not be attributed to NK cell activity, since common gamma-chain-deficient RAG2-/- mice lacking NK cells show low LCMV titers comparable to those for RAG2-/- mice. Furthermore, the reduced early LCMV production in spleens could not be explained by an enhanced gamma interferon production in RAG2-/- mice. Analysis of mutant mice exhibiting various defects in the splenic microarchitecture, including (i) tumor necrosis factor alpha-negative (TNF-alpha-/-), lymphotoxin alpha-negative (LTalpha-/-), B-cell-deficient muMT mice, (ii) immunoglobulin M-negative mice, and (iii) RAG2-/- mice reconstituted with wild-type versus TNF-alpha-/- LTalpha-/- B cells, revealed a clear correlation between an intact splenic marginal zone, rapid early replication of LCMV in the spleen, and efficient CTL induction. These results suggest that by the preferential infection of the highly organized splenic microarchitecture, LCMV seems to successfully exploit one of the key elements in the chain of the adaptive immune system. Not only does the early tropism of LCMV for the splenic marginal zone trigger a potent immune response, but at the same time the marginal zone may also become a target of early CTL-mediated immunopathology that impairs immune responsiveness.     

Polymorphisms within the C-reactive protein (CRP) promoter region are associated with plasma CRP levels

Elevated plasma levels of C-reactive protein (CRP), an inflammation-sensitive marker, have emerged as an important predictor of future cardiovascular disease and metabolic abnormalities in apparently healthy men and women. Here, we performed a systematic survey of common nucleotide variation across the genomic region encompassing the CRP gene locus. Of the common single-nucleotide polymorphisms (SNPs) identified, several in the CRP promoter region are strongly associated with CRP levels in a large cohort study of cardiovascular risk in European American and African American young adults. We also demonstrate the functional importance of these SNPs in vitro.     

Modulation of intestinal urea cycle by dietary spermine in suckling rat

Argininosuccinate synthetase, an ubiquitous enzyme in mammals, catalyses the formation of argininosuccinate, the precursor of arginine. Arginine is recognised as an essential amino acid in foetuses and neonates, but also as a conditionally essential amino acid in adults. Argininosuccinate synthetase is initially expressed in enterocytes during the developmental period, it disappeared from this organ then appeared in the kidneys. Although the importance of both intestinal and renal argininosuccinate synthetases has been recognised for a long time, nutrients have not yet been identified as inducers of the gene expression. In the context of a proteomic screening of intestinal modifications induced by dietary spermine in suckling rats, we showed that argininosuccinate synthetase and carbamoyl phosphate synthase disappeared from enterocytes after this treatment. The disappearance of argininosuccinate synthetase in small intestine was confirmed by immunodetection. Expression of carbamoyl phosphate synthase and argininosuccinate synthetase coding genes decreased also after spermine administration. Expression of other urea cycle enzyme coding genes was modulated by spermine administration: argininosuccinate lyase decreased and arginase increased. Our results fit with the developmental variation of argininosuccinate synthetase and carbamoyl phosphate synthase. Modulation of the gene expression for several urea cycle enzymes suggests a coordination between all the pathway steps and switch toward polyamine (or proline and glutamate) biosynthesis from ornithine.