Mast cell proteases liberate stable encephalitogenic fragments from intact myelin.

Protease-containing supernatants from activated rat mast cells were found to degrade purified rat myelin with a subsequent release of a stable encephalitogenic peptide. The two most abundant peptides were identified as residues 69-87 (GSLPQKSQRTQDENPVV) and residues 69-88 (GSLPQKSQRTQDENPVVH). While additional exposure to the mast cell supernatants removes the COOH terminal histamine from peptide 69-88 to yield peptide 69-87, additional proteolytic degradation of the 69-87 peptide was not detected. Immunization with this peptide emulsified in CFA caused the development of clinical experimental autoimmune encephalomyelitis (EAE) in Lewis rats. In addition this 69-87 sequence was found to activate resting encephalitogenic myelin basic protein-reactive T cell lines to adoptively transfer clinical EAE. The release of stable encephalitogenic peptides from the myelin sheath by mast cell proteases may play a role in activation of encephalitogen-specific T cells during the progression of EAE.     

Changes in peroxidases in the suspension culture of Rubus fruticosus during growth

The growth parameters of a cell suspension culture of Rubus fruticosus L. were determined over a culture period including exponential growth, stationary phase and a glucose starvation period at the end of the normal culture cycle. Peroxidase activities were measured in the cytoplasm, in the cell wall, and in the culture medium by the guaiacol assay. There is a relationship between the activity found in the spent medium and the dry matter mass of the cells during the exponential growth. In the three compartments a bimodal repartition of peroxidase activities was observed, with the two peaks at day 4 and day 26, respectively. This suggests that the first peak corresponds to actively dividing cells whereas the second is associated with senescence, or stress due to starvation. Fractionation of the peroxidases from the culture mediuim revealed the presence of two sets of cationic isoenzymes, with minor amount of anionic peroxidases. Interestingly, the second peak of cationic enzymes which was of weak intensity at day 10 of the culture, becameprevalent at day 26. This indicates that not only the total amount of peroxidases varies as a function of culture time, but also that the nature of the peroxidases secreted into the medium changes during growth.Abbreviations DW dry weight - FW fresh weight - MV medium volume - SV suspension volume - BSA bovine serum albumin     

Actin Depolymerizing Factor (ADF/Cofilin) Enhances the Rate of Filament Turnover: Implication in Actin-based Motility

Actin-binding proteins of the actin depolymerizing factor (ADF)/cofilin family are thought to control actin-based motile processes. ADF1 from Arabidopsis thaliana appears to be a good model that is functionally similar to other members of the family. The function of ADF in actin dynamics has been examined using a combination of physical–chemical methods and actin-based motility assays, under physiological ionic conditions and at pH 7.8. ADF binds the ADPbound forms of G- or F-actin with an affinity two orders of magnitude higher than the ATP- or ADP-Pi– bound forms. A major property of ADF is its ability to enhance the in vitro turnover rate (treadmilling) of actin filaments to a value comparable to that observed in vivo in motile lamellipodia. ADF increases the rate of propulsion of Listeria monocytogenes in highly diluted, ADF-limited platelet extracts and shortens the actin tails. These effects are mediated by the participation of ADF in actin filament assembly, which results in a change in the kinetic parameters at the two ends of the actin filament. The kinetic effects of ADF are end specific and cannot be accounted for by filament severing. The main functionally relevant effect is a 25-fold increase in the rate of actin dissociation from the pointed ends, while the rate of dissociation from the barbed ends is unchanged. This large increase in the rate-limiting step of the monomer-polymer cycle at steady state is responsible for the increase in the rate of actin-based motile processes. In conclusion, the function of ADF is not to sequester G-actin. ADF uses ATP hydrolysis in actin assembly to enhance filament dynamics.     

Contribution a l'étude desAphelinidae aphidiphages et de leurs hotes en France [Hym. Chalcidoidea]

Résumé L'auteur donne un nouvel exemple de variabilité de la pigmentation chez un Aphelinide. L'inventaire des Aphelinides de France est dressé; 26 h?tes nouveaux sont précisés. L'observation du comportement de plusieurs espèces d'Aphelinides dans la nature a révélé l'importance du facteur de l'humidité ambiante pour l'apparition de taux de parasitisme élevés.

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Summary New data on the pigmentation variability byA. chaonia Wlk. (Aphelinidae) under natural conditions are given. The provisional list of the 11 species ofAphelinidae collected in France till now includesAphelinus flavipes Foerster andA. varipes Foerster, two species not recorded before in this country; 26 new hosts are recorded as parasites of 6 species ofAphelinus. Field observations on several Aphelinids emphasize the importance of the high level of surrounding humidity to determine high parasitism rates.

     

The role of mast cells in the elicitation of experimental allergic encephalomyelitis

Experimental allergic encephalomyelitis (EAE), a T cell-mediated autoimmune disease can be transferred with lymphoid cells from actively immunized rats into naive recipients. In the mouse, previous studies have suggested a role for histamine/serotonin in the development of active EAE. We have found that myelin basic protein-reactive cells transfer a biphasic skin test response to naive rats analogous to what has been described in the mouse contact dermatitis system, where mast cell sensitization by Ag-specific T cell factors is required for the induction of skin test responses. Treatment of cell recipients with the serotonin receptor antagonists, cyproheptadine or methysergide, blocked or significantly reduced the development of EAE. Furthermore, it was found that treatment with cyproheptadine was effective in blocking clinical disease when administered day 3 to day 6 after cell transfer. In contrast, cyproheptadine treatments before induction of paralysis day 0 to 3, failed to alter the course of clinical disease. The inhibitor of mast cell degranulation, proxicromil, was also found to effectively block the elicitation of adoptively transferred EAE and was also found to be effective when administered just before the onset of clinical disease. Reserpine, a compound known to deplete mast cells of vasoactive amines by forcing granule contents into the cytoplasm where they are degraded by cell enzymes, was also effective in blocking both active and adoptively transferred EAE. Disease inhibition was found to be partially reversed with pargyline, an inhibitor of monoamine oxidase. In addition lymphocytes from treated animals were capable of transferring disease to naive recipients and appeared to have normal activity as assessed by Ag-or mitogen-driven proliferation in addition to IL-2 production.     

Population Genetics and Signatures of Selection in Early Neolithic European Farmers

Human expansion in the course of the Neolithic transition in western Eurasia has been one of the major topics in ancient DNA research in the last 10 years. Multiple studies have shown that the spread of agriculture and animal husbandry from the Near East across Europe was accompanied by large-scale human expansions. Moreover, changes in subsistence and migration associated with the Neolithic transition have been hypothesized to involve genetic adaptation. Here, we present high quality genome-wide data from the Linear Pottery Culture site Derenburg-Meerenstieg II (DER) (N = 32 individuals) in Central Germany. Population genetic analyses show that the DER individuals carried predominantly Anatolian Neolithic-like ancestry and a very limited degree of local hunter-gatherer admixture, similar to other early European farmers. Increasing the Linear Pottery culture cohort size to ∼100 individuals allowed us to perform various frequency- and haplotype-based analyses to investigate signatures of selection associated with changes following the adoption of the Neolithic lifestyle. In addition, we developed a new method called Admixture-informed Maximum-likelihood Estimation for Selection Scans that allowed us test for selection signatures in an admixture-aware fashion. Focusing on the intersection of results from these selection scans, we identified various loci associated with immune function (JAK1, HLA-DQB1) and metabolism (LMF1, LEPR, SORBS1), as well as skin color (SLC24A5, CD82) and folate synthesis (MTHFR, NBPF3). Our findings shed light on the evolutionary pressures, such as infectious disease and changing diet, that were faced by the early farmers of Western Eurasia.     

Biological and physico-chemical processes influence cutin and suberin biomarker distribution in two Mediterranean forest soil profiles

Recent investigations have shown macromolecules, such as cutins, and suberins as effective markers for above and belowground plant tissues. These biopolyesters contain structural units specific for different litter components and for root biomass. The aim of this work was to understand the fate of plant organic matter (OM) in Mediterranean forest soils by evaluating the incorporation of cutin and suberin by measuring specific biomarkers. Soil and plant tissue (leaves, woods and roots) samples were collected in two mixed Mediterranean forests of Quercus ilex (holm oak) in costal stands in Tuscany (central Italy), which have different ecological and edaphic features. Ester-bound lipids of mineral and organic horizons and the overlying vegetation were analysed using the saponification method in order to depolymerise cutins and suberins and release their specific structural units. Cutin and suberin specific aliphatic monomers were identified and quantified by gas chromatographic techniques. The distribution of cutin and suberin specific monomers in plant tissue suggested that mid-chain hydroxy acids can be used as leaf-specific markers and α,ω-alkanedioic acids and ωC_18:1 as root-specific markers. Differences in the distributions of biomarkers specific for above and belowground plant-derived OM was observed in the two types of soils, suggesting contrasted degradation, stabilisation and transport mechanisms that may be related to soil physico-chemical properties. The acidic and dry soil appeared to inhibit microbial activity, favouring stabilization of leaf-derived compounds, while, in the more fertile soil, protection within aggregates appeared to better preserve root-derived compounds.