Multivalent catanionic GalCer analogs derived from first generation dendrimeric phosphonic acids

The synthesis and characterization of a new series of catanionic multivalent analogs of GalCer is described. These systems are based on phosphonic acid terminated dendrimers and N-hexadecylamino lactitol moieties. Despite important structural differences that affect the dendrimers’ outer-shell, these supramolecular assemblies showed a fairly comparable anti-HIV-1 activity. All compounds have submicromolar IC₅₀ in a cell-based HIV-infection model but also a high general cytotoxicity.     

The diversity of subunit composition in nAChRs: evolutionary origins,physiologic and pharmacologic consequences

Nicotinic acetylcholine receptors are made up of homologous subunits, which are encoded by a large multigene family. The wide number of receptor oligomers generated display variable pharmacological properties. One of the main questions underlying research in molecular pharmacology resides in the actual role of this diversity. It is generally assumed that the observed differences between the pharmacology of homologous receptors, for instance, the EC(50) for the endogenous agonist, or the kinetics of desensitization, bear some kind of physiologic relevance in vivo. Here we develop the quite challenging point of view that, at least within a given subfamily of nicotinic receptor subunits, the pharmacologic variability observed in vitro would not be directly relevant to the function of receptor proteins in vivo. In vivo responses are not expected to be sensitive to mild differences in affinities, and several examples of functional replacement of one subunit by another have been unravelled by knockout animals. The diversity of subunits might have been conserved through evolution primarily to account for the topologic diversity of subunit distribution patterns, at the cellular and subcellular levels. A quantitative variation of pharmacological properties would be tolerated within a physiologic envelope, as a consequence of a near-neutral genetic drift. Such a "gratuitous" pharmacologic diversity is nevertheless of practical interest for the design of drugs, which would specifically tackle particular receptor oligomers with a defined subunit composition among the multiple nicotinic receptors present in the organism.     

Cholinergic agonist-induced pepsinogen secretion from murine gastric chief cells is mediated by M1 and M3 muscarinic receptors

Muscarinic cholinergic mechanisms play a key role in stimulating gastric pepsinogen secretion. Studies using antagonists suggested that the M3 receptor subtype (M3R) plays a prominent role in mediating pepsinogen secretion, but in situ hybridization indicated expression of M1 receptor (M1R) in rat chief cells. We used mice that were deficient in either the M1 (M1R-/-) or M3 (M3R-/-) receptor or that lacked both receptors (M(1/3)R-/-) to determine the role of M1R and M3R in mediating cholinergic agonist-induced pepsinogen secretion. Pepsinogen secretion from murine gastric glands was determined by adapting methods used for rabbit and rat stomach. In wild-type (WT) mice, maximal concentrations of carbachol and CCK caused a 3.0- and 2.5-fold increase in pepsinogen secretion, respectively. Maximal carbachol-induced secretion from M1R-/- mouse gastric glands was decreased by 25%. In contrast, there was only a slight decrease in carbachol potency and no change in efficacy when comparing M3R-/- with WT glands. To explore the possibility that both M1R and M3R are involved in carbachol-mediated pepsinogen secretion, we examined secretion from glands prepared from M(1/3)R-/- double-knockout mice. Strikingly, carbachol-induced pepsinogen secretion was nearly abolished in glands from M(1/3)R-/- mice, whereas CCK-induced secretion was not altered. In situ hybridization for murine M1R and M3R mRNA in gastric mucosa from WT mice revealed abundant signals for both receptor subtypes in the cytoplasm of chief cells. These data clearly indicate that, in gastric chief cells, a mixture of M1 and M3 receptors mediates cholinergic stimulation of pepsinogen secretion and that no other muscarinic receptor subtypes are involved in this activity. The development of a murine secretory model facilitates use of transgenic mice to investigate the regulation of pepsinogen secretion.     

Knee meniscal extrusion in a largely non-osteoarthritic cohort: association with greater loss of cartilage volume

We conducted a longitudinal study (duration 2 years), including 294 individuals (mean age 45 years, 58% female), in order to examine associations between meniscal extrusion, knee structure, radiographic changes and risk factors for osteoarthritis (OA) in a largely non-osteoarthritic cohort. Meniscal extrusion, tibiofemoral cartilage defect score and cartilage volume, and tibial plateau bone area were determined using T1-weighted fat-saturated magnetic resonance imaging. At baseline the presence of medial meniscal extrusion was significantly associated with body mass index (odds ratio [OR] per kg/m2 = 1.13, 95% confidence interval [CI] = 1.02-1.25), past knee injury (positive versus negative history: OR = 3.73, 95% CI = 1.16-11.97), medial tibial bone area (OR per cm2 = 1.37, 95% CI = 1.02-1.85), and osteophytes (OR per grade = 4.89, 95% CI = 1.59-15.02). Two-year longitudinal data revealed that medial meniscal extrusion at baseline was associated with a greater rate of loss of medial tibiofemoral cartilage volume (extrusion versus no extrusion: -1.4%/year; P < 0.05) and greater risk for increased medial femoral cartilage defects (OR = 2.59, 95% CI = 1.14-5.86) and lateral tibial cartilage defects (OR = 2.64, 95% CI = 1.03-6.76). However, the latter two associations became nonsignificant after adjustment for tibial bone area and osteophytes. This study suggests that increasing body mass index and bone size, past knee injury, and osteophytes may be causally related to meniscal extrusion. Most importantly, meniscal extrusion at baseline is associated with greater loss of knee cartilage over 2 years, and this seems to be mediated mostly by subchondral bone changes, suggesting extrusion represents one pathway between bone expansion and cartilage loss.     

Effects of the New Arginase Inhibitor N-Hydroxy-nor- -Arginine on NO Synthase Activity in Murine Macrophages

In stimulated murine macrophage, arginase and nitric oxide synthase (NOS) compete for their common substrate, -arginine. The objectives of this study were (i) to test the new α-amino acid N^ω-hydroxy-nor- -arginine (nor-NOHA) as a new selective arginase inhibitor and (ii) to elucidate the effects of arginase inhibition on -arginine utilization by an inducible NOS. Nor-NOHA is about 40-fold more potent than N^ω-hydroxy- -arginine (NOHA), an intermediate in the -arginine/NO pathway, to inhibit the hydrolysis of -arginine to -ornithine catalyzed by unstimulated murine macrophages (IC₅₀ values 12 ± 5 and 400 ± 50 μM, respectively). Stimulation of murine macrophages with interferon-γ and lipopolysaccharide (IFN-γ + LPS) results in clear expression of an inducible NOS (iNOS) and to an increase in arginase activity. Nor-NOHA is also a potent inhibitor of arginase in IFN-γ + LPS-stimulated macrophage (IC₅₀ value 10 ± 3 μM). In contrast to NOHA, nor-NOHA is neither a substrate nor an inhibitor for iNOS and it appears as a useful tool to study the interplays between arginase and NOS. Inhibition of arginase by nor-NOHA increases nitrite and -citrulline accumulation for incubation times higher than 12 h, under our conditions. Our results allow the determination of the kinetic parameters of the two competitive pathways and the proposal of a simple model which readily explains the differences observed between experiments. This model readily accounts for the observed effects and should be useful to predict the consequences of arginase inhibition in the presence of an active NOS on -arginine availability.     

Recombinant Interferon-γ Lentivirus Co-Infection Inhibits Adenovirus Replication Ex Vivo

Recombinant interferon-γ (IFNγ) production in cultured lentivirus (LV) was explored for inhibition of target virus in cells co-infected with adenovirus type 5 (Ad5). The ability of three different promoters of CMV, EF1α and Ubiquitin initiating the enhanced green fluorescence protein (GFP) activities within lentiviruses was systematically assessed in various cell lines, which showed that certain cell lines selected the most favorable promoter driving a high level of transgenic expression. Recombinant IFNγ lentivirus carrying CMV promoter (LV-CMV-IFNγ) was generated to co-infect 293A cells with a viral surrogate of recombinant GFP Ad5 in parallel with LV-CMV-GFP control. The best morphologic conditions were observed from the two lentiviruses co-infected cells, while single adenovirus infected cells underwent clear pathologic changes. Viral load of adenoviruses from LV-CMV-IFNγ or LV-CMV-GFP co-infected cell cultures was significantly lower than that from adenovirus alone infected cells (P = 0.005–0.041), and the reduction of adenoviral load in the co-infected cells was 86% and 61%, respectively. Ad5 viral load from LV-CMV-IFNγ co-infected cells was significantly lower than that from LV-CMV-GFP co-infection (P = 0.032), which suggested that IFNγ rather than GFP could further enhance the inhibition of Ad5 replication in the recombinant lentivirus co-infected cells. The results suggest that LV-CMV-IFNγ co-infection could significantly inhibit the target virus replication and might be a potential approach for alternative therapy of severe viral diseases.     

Brucella β 1,2 Cyclic Glucan Is an Activator of Human and Mouse Dendritic Cells

Bacterial cyclic glucans are glucose polymers that concentrate within the periplasm of alpha-proteobacteria. These molecules are necessary to maintain the homeostasis of the cell envelope by contributing to the osmolarity of Gram negative bacteria. Here, we demonstrate that Brucella β 1,2 cyclic glucans are potent activators of human and mouse dendritic cells. Dendritic cells activation by Brucella β 1,2 cyclic glucans requires TLR4, MyD88 and TRIF, but not CD14. The Brucella cyclic glucans showed neither toxicity nor immunogenicity compared to LPS and triggered antigen-specific CD8⁺ T cell responses in vivo. These cyclic glucans also enhanced antigen-specific CD4⁺ and CD8⁺ T cell responses including cross-presentation by different human DC subsets. Brucella β 1,2 cyclic glucans increased the memory CD4⁺ T cell responses of blood mononuclear cells exposed to recombinant fusion proteins composed of anti-CD40 antibody and antigens from both hepatitis C virus and Mycobacterium tuberculosis. Thus cyclic glucans represent a new class of adjuvants, which might contribute to the development of effective antimicrobial therapies.     

Presence de pollens d'Hamamelis (Hamamelidaceae,Angiospermae) dans le pliocene du Sud de la France

Pollen-analysis shows the presence of the genus Hamamelis in the pliocene flora of southern France. It contributesto the knowledge of the past distribution of taxa which are now extinct in western Europe.     

Biomass-pigment relationships in potamoplankton

During most of the growing season of 1994, pigment content,as determined by HPLC analysis of algal sample extracts, wasfollowed in the River Meuse (Belgium) potamoplankton. The concentrationof some algal pigments (chlorophylls a and b, fucoxanthin, lutein,echinenone and alloxanthin) was related to biomass estimatesof total phytoplankton and of major taxonomic components (diatoms,green algae, cyanobacteria and cryptomonads). Highly significantlinear regressions were obtained for chlorophyll a-total biomass,fucoxanthin-diatoms, lutein-green algae, chlorophyll b-greenalgae. However, no relationship was found for cyanobacteriaor cryptomonads and their specific pigments, which may be attributedto poor accuracy of biomass estimates for these non-dominantalgae. In conclusion, the good relationship found for dominantalgae and their specific pigments confirms the value of pigmentsas quantitative markers of phytoplankton, as detected in othermarine and freshwater environments.