Ans fluorescence and electrokinetic potential of activated lymphocytes by con A or LPS in vivo

The $\text{in vivo}$ effect of Concanavalin A (Con A), or bacterial lipopolysaccharide (LPS) on mouse spleen cell populations was investigated. The membrane fluorescence changes of activated splenic lymphocytes were studied during two weeks after the injection of polyclonal immunogens. Experiments were performed with the hydrophobic fluorescent probe: 1-anilino-8-naphthalene sulphonate (ANS). The kinetic studies further indicated that the course of fluorescence changes may considerably vary depending on both immunogens. These fluorescence intensity changes would be in direct relation to the electrokinetic surface potential changes of activated lymphocytes, as assessed by the electrophoretic mobility analysis. By comparison with the inverse relationship observed in our previous study, it would be concluded that the relation (direct or inverse) between ANS fluorescence and electrokinetic potential depends on the net electrical charge of the antigens used.     

Une faune de petits mammiferes d'age turolien moyen(Miocene superieur) a Cucuron (Vaucluse); donnees nouvelles sur le genre Stephanomys (Rodentia) et consequences stratigraphiques

A small mammal fauna, including rodents and a new species of Murid, Stephanomys stadii n. sp., has been found in a continental formation underlying the deposits with the famous big mammal fauna of Mont Luberon. This fauna of small mammals is a little younger than the fauna of Los Mansuetos (Spain), so, the Pikermian fauna of Mont Luberon, which is said to be of the same age as the fauna of Pikermi is younger than the fauna of big and small mammals of Los Mansuetos.     

Synthesis of glycosyl halides and glycosides via 1-O-sulfonyl derivatives

The reaction of an aldose derivative containing a free anomeric hydroxyl group with trifluoromethanesulfonic anhydride or methanesulfonic anhydride, in the presence of halide ion and s-collidine, furnishes a glycosyl halide; if an alcohol is then introduced, glycoside synthesis is effected in an overall, “one-pot” reaction. Several α-d-glucopyranosides, including disaccharides, have been prepared in high yield by using 2,3,4,6-tetra-O-benzyl-d-glucose as the aldose, and generating the corresponding glycosyl bromide(s) in situ. As a halide-exchange step is incorporated in the reaction sequence, orthoacetate formation was favored in reactions of 2,3,4,6-tetra-O-acetyl-d-glucose, such as occurs with per-O-acetylglycosyl halides. Methanesulfonic anhydride promotes glycosidation or orthoester formation in the absence of halide ion, as well as in its presence, whereas formation of an intermediate glycosyl halide appears to be necessary in order to moderate the more vigorous reactions of the trifluoro derivative. The analogous reaction of methanesulfonyl chloride with an aldose provides a ready route to glycosyl chlorides. Under the conditions employed for these various syntheses, acid-sensitive protecting groups may be used, including cyclic and acyclic acetals and O-trityl substituents.     

Experimental study of the sensitizing power of methoxyflurane]

Methyoxyflurane, a halogenated general anaesthetic, showed a net sensibilizing effect in the guinea-pig when tested experimentally by the Magnusson and Klingman technique. According to these authors classification it may be classed as of "moderate allergenicity". In addition, the sensibilisation reaction obtained is prolonged. It remains at a similar level for 2 to 7 weeks after the end of the sensibilisation phase.     

Reduction of oxidized inorganic nitrogen compounds by a new strain of Thiobacillus denitrificans

Denitrification by Thiobacillus denitrificans "RT" strain was investigated using manometry and gas chromatography. 1. From nitrate, resting cells produced only nitrogen anaerobically with thiosulfate as the electron donor. The data suggest that nitrate was assimilated and dissimilated by the same nitrate reductase, assayed with benzyl-viologen as the electron donor. 2. From nitrite, whole cells produced nitric oxide, nitrous oxide and nitrogen, using thiosulfate as the electron donor; nitrogen was the final product of the reduction. Crude extract reduced nitrite to nitrogen with p-phenylene-diamine and dimethyl-p-phenylene diamine as the electron donors, and produced nitric oxide, nitrous oxide and nitrogen with tetramethyl-p-phenylene-diamine as the electron donor. Nitrite was reduced to nitric oxide and nitrous oxide by crude extract using ascorbate-phenazine methosulfate as the electron donor. 3. From nitric oxide, whole cells produced nitrous oxide and nitrogen using thiosulfate as the electron donor, nitrogen was the final reduction product. Nitric oxide was reduced to nitrous oxide by crude extract with the ascorbate-phenazine methosulfate system. 4. Whole cells reduced nitrous oxide to nitrogen with thiosulfate as the electron donor. It was not possible to detect any nitrous oxide reductase activity in crude extract. 5. A scheme was of denitrification by Thiobacillus denitrificans "RT" strain.     

A synthetic amino acid substitution of Tyr10 in Aβ peptide sequence yields a dominant negative variant in amyloidogenesis

Alzheimer's disease (AD) is the most common cause of dementia in elderly people, and age is the major nongenetic risk factor for sporadic AD. A hallmark of AD is the accumulation of amyloid in the brain, which is composed mainly of the amyloid beta-peptide (Aβ) in the form of oligomers and fibrils. However, how aging induces Aβ aggregation is not yet fully determined. Some residues in the Aβ sequence seem to promote Aβ-induced toxicity in association with age-dependent risk factors for AD, such as (i) increased GM1 brain membrane content, (ii) altered lipid domain in brain membrane, (iii) oxidative stress. However, the role of Aβ sequence in promoting aggregation following interaction with the plasma membrane is not yet demonstrated. As Tyr10 is implicated in the induction of oxidative stress and stabilization of Aβ aggregation, we substituted Tyr 10 with a synthetic amino acid that abolishes Aβ-induced oxidative stress and shows an accelerated interaction with GM1. This variant peptide shows impaired aggregation properties and increased affinity for GM1. It has a dominant negative effect on amyloidogenesis in vitro, in cellulo, and in isolated synaptosomes. The present study shed new light in the understanding of Aβ-membrane interactions in Aβ-induced neurotoxicity. It demonstrates the relevance of Aβ sequence in (i) Aβ-membrane interaction, underlining the role of age-dependent enhanced GM1 content in promoting Aβ aggregation, (ii) Aβ aggregation, and (iii) Aβ-induced oxidative stress. Our results open the way for the design of peptides aimed to inhibit Aβ aggregation and neurotoxicity.     

Conflicting mitochondrial and nuclear phylogeographic signals and evolution of host-plant shifts in the boreo-montane leaf beetle Chrysomela lapponica

We conducted a phylogeographic study on the cold-adapted leaf beetle Chrysomela lapponica, that feeds on willow or birch, by sampling several populations throughout most of the geographic distribution of the species, and by sequencing for each individual one mitochondrial and two nuclear DNA fragments. Patterns of DNA sequence variation from the mitochondrial and nuclear loci, as displayed in the median-joining networks, appear to display contradicting historical signal: a deep genealogical divergence is observed with the mitochondrial genome between the Alpine population and all other populations found in the Euro-Siberian distribution of the species, that is completely absent with both nuclear loci. We use coalescence simulations of DNA sequence evolution to test the hypothesis that this apparent conflict is compatible with a neutral model of sequence evolution (i.e., to check whether the stochastic nature of the coalescence process can explain these patterns). Because the simulations show that this is highly unlikely, we consider two alternative hypotheses: (1) introgression of the mitochondrial genome of another species and (2) the effect of natural selection. Although introgression is the most plausible explanation, we fail to identify the source species of the introgressed mitochondrial genome among all known species closely related to C. lapponica. We therefore suggest that the putative introgression event is ancient and the source species is either extinct or currently outside the geographic range of C. lapponica explored in this study. The observed DNA sequence variation also suggests that a host-plant shift from willow to birch has occurred recently and independently in each of the three birch-feeding populations. This emphasizes further the relative ease with which these beetles can escape their ancestral host-plant specialization on willow, but shows at the same time that host-plant shifts are highly constrained, as they only occur between willow and birch.