Distribution of injected MRI contrast agents in mouse livers studied by confocal and SIMS microscopy

OBJECTIVE: To localize magnetic resonance imaging (MRI) contrast agents injected intravenously into mouse livers. STUDY DESIGN: Parallel studies were performed on fluorescent europium and nonfluorescent, paramagnetic gadolinium and on a product combining nanoparticles of Fe and Texas Red to obtain combined information on the distribution of these molecules inside the liver. The distribution of different superparamagnetic iron oxides was also studied because the size of these new compounds is not always convenientfor microcirculation studies. RESULTS: Europium and Texas Red can be detected by confocal microscopy. Europium, iron and gadolinium can be detected by secondary ion mass spectrometry (SIMS) microscopy. Studies confirmed the complementarity of both microscopies. They also confirmed the possibility of using europium as a model of gadolinium to analyze thefate of MRI contrast agents. CONCLUSION: The methodology can be used on mice injected intravenously and analyzed by confocal and SIMS microscopy to localize MRI contrast agents inside cellular and tissue specimens of mice.     

Role of STAT3 in CD4+CD25+FOXP3+ regulatory lymphocyte generation: implications in graft-versus-host disease and antitumor immunity

Immunological tolerance is maintained by specialized subsets of T cells including CD4(+)CD25(+)FOXP3(+) regulatory cells (Treg). Previous studies established that Treg thymic differentiation or peripheral conversion depend on CD28 and Lck signaling. Moreover, foxp3 gene transfer in murine CD4(+)CD25(-) T lymphocytes results in the acquisition of suppressive functions. However, molecular pathways leading to FOXP3 expression remain to be described. In this study, we investigated the molecular events driving FOXP3 expression. We demonstrated that CD28 activation in CD4(+)CD25(-) T lymphocytes leads to STAT3 Tyr(705) phosphorylation in an Lck-dependent manner. STAT3 neutralization during naive peripheral CD4(+)CD25(-) T cell conversion into Treg through costimulation with TCR/CD28 and TGF-beta1, decreased FOXP3 expression, prevented the acquisition of suppressive functions and restored the ability of the converted lymphocytes to produce IL-2 and IFN-gamma. Furthermore, we observed that STAT3 ablation using small interfering RNA strategies inhibited FOXP3 expression and suppressive functions among naturally differentiated CD4(+)CD25(+) T lymphocytes, suggesting a direct role of STAT3 in Treg phenotype and function maintenance. CD4(+)CD25(+) T lymphocytes transduced with specific STAT3 small interfering RNA were devoid of suppressive functions and failed to control the occurrence of acute graft-vs-host disease. Finally, STAT3 inhibition in CD4(+) lymphocytes enhanced the anti-tumor immunity conferred by a lymphocyte adoptive transfer. In summary, our findings determine that STAT3 is critical in the molecular pathway required for FOXP3 expression. STAT3 modulation should be taken into account when assessing how regulatory T cells contribute to inflammatory diseases and tumor immunosurveillance.     

Peripheral, central and behavioral responses to the cuticular pheromone bouquet in Drosophila melanogaster males

Pheromonal communication is crucial with regard to mate choice in many animals including insects. Drosophila melanogaster flies produce a pheromonal bouquet with many cuticular hydrocarbons some of which diverge between the sexes and differently affect male courtship behavior. Cuticular pheromones have a relatively high weight and are thought to be -- mostly but not only -- detected by gustatory contact. However, the response of the peripheral and central gustatory systems to these substances remains poorly explored. We measured the effect induced by pheromonal cuticular mixtures on (i) the electrophysiological response of peripheral gustatory receptor neurons, (ii) the calcium variation in brain centers receiving these gustatory inputs and (iii) the behavioral reaction induced in control males and in mutant desat1 males, which show abnormal pheromone production and perception. While male and female pheromones induced inhibitory-like effects on taste receptor neurons, the contact of male pheromones on male fore-tarsi elicits a long-lasting response of higher intensity in the dedicated gustatory brain center. We found that the behavior of control males was more strongly inhibited by male pheromones than by female pheromones, but this difference disappeared in anosmic males. Mutant desat1 males showed an increased sensitivity of their peripheral gustatory neurons to contact pheromones and a behavioral incapacity to discriminate sex pheromones. Together our data indicate that cuticular hydrocarbons induce long-lasting inhibitory effects on the relevant taste pathway which may interact with the olfactory pathway to modulate pheromonal perception.     

ALIX and ESCRT-III Coordinately Control Cytokinetic Abscission during Germline Stem Cell Division In Vivo

Abscission is the final step of cytokinesis that involves the cleavage of the intercellular bridge connecting the two daughter cells. Recent studies have given novel insight into the spatiotemporal regulation and molecular mechanisms controlling abscission in cultured yeast and human cells. The mechanisms of abscission in living metazoan tissues are however not well understood. Here we show that ALIX and the ESCRT-III component Shrub are required for completion of abscission during Drosophila female germline stem cell (fGSC) division. Loss of ALIX or Shrub function in fGSCs leads to delayed abscission and the consequent formation of stem cysts in which chains of daughter cells remain interconnected to the fGSC via midbody rings and fusome. We demonstrate that ALIX and Shrub interact and that they co-localize at midbody rings and midbodies during cytokinetic abscission in fGSCs. Mechanistically, we show that the direct interaction between ALIX and Shrub is required to ensure cytokinesis completion with normal kinetics in fGSCs. We conclude that ALIX and ESCRT-III coordinately control abscission in Drosophila fGSCs and that their complex formation is required for accurate abscission timing in GSCs in vivo.     

Synthèse des 2-acé-tamido-2-désoxy-6-O-α-et β-D-xylopyranosyl-α-D-glucopyranose

2-Acetamido-2- deoxy-6-O-, -xylopyranosyl-O-D-glucopyranose has been synthesized in crystalline form by condensation of 2,3,4-tri-O-acetyl-α-D-xylopyranosyl chloride (1) with benzyl 2-acetamido-3,4-di-O-acetyl-2-deoxy-β-D-glucopyranoside (2), followed by O-deacetylation and catalytic hydrogenation. Condensation of 2 with 2,3,4-tri-O-chlorosulfonyl-β-D-xylopyranosyl chloride, followed by dechlorosulfonylation and acetylation, gave benzyl 2-acetamido-3,4-di-O-acetyl-2-deoxy-6-O-(2,3,4-tri-O-acetyl-α-D-xylopyranosyl)β-D-glucopyranoside in crystalline form. O-Deacetylation, followed by catalytic hydrogenation, gave 2-acetamido-2-deoxy-6-O-α-D-xylopyranosyl-α-D-glucopyranose in crystalline form.     

Étude De Quelques Acides Humiques Sur Gel De Dextrane

Résumé Les acides humiques extraits de 3 sols différents sont étudiés par chromatographie sur colonnes de gel de dextrane Sephadex, successivement sur G 25 F, G 75, G 200.Dans les conditions de l'expérience, on a mis en évidence l'existence de volumes moléculaires privilégiés, et on a pu apprécier les poids moléculaires correspondant à certains d'entre eux.De plus, on n'observe pas de différence qualitative entre les fractions des divers échantillons, mais seulement des variations quantitatives quant à l'importance de ces fractions.     

Spectroscopie infra-rouge de quelques acides humiques

Resume Dans un travail précédent³, on a fractionné sur gel de dextrane Sephadex les acides humiques extraits de trois types de sol. On reprend ici la fraction qui correspond aux faibles poids moléculaires, et on l'étudie par spectroscopie I.R. selon la technique des pastilles de KBr, de 4000 à 650 cm^-1.Les enregistrement présentent tous une certaine ressemblance, quel que soit le type de sol dont proviennent les acides humiques.Tous les spectres présentent 4 bandes principales d'absorption, situées successivement vers 3400 cm^-1, 1600 cm^-1, 1400 cm^-1, 1150 cm^-1. La signification de ces bandes est longuement discutée, puis on examine, plus brièvement, leur intensité. re]19721019     

Multimodal distribution and discontinuous variation in period of interacting oscillators in the crustacean stomatogastric nervous system

Summary In the stomatogastric ganglion (STG) of Homarus gammarus, pacemaker neurons of the pyloric central pattern generator are entrained by a network oscillator (CPO) contained in the commissural ganglion. A consequence of CPO's influence is that the spontaneous pyloric period can take one of several absolute values, most commonly displaying a bimodal distribution. These discrete values correspond to different coordination modes with the CPO rhythm. Moreover, the oscillation period of pyloric pacemaker neurons varies discontinuously with their membrane potential. This behavior persists when the mean pyloric period is modified by different perfusion salines but disappears when the STG is disconnected from the anterior ganglia. Under these conditions, pyloric pacemaker neurons are deprived of CPO inputs and behave like independent oscillators whose period varies continuously as a function of the membrane potential. The modulatory pyloric suppressor neurons (PS), which are known to decrease the oscillatory capabilities of the pyloric pacemakers, can change the coordination mode between these neurons and the CPO. PS can provoke discontinuous variations in the pyloric period as a function of their firing frequency. Finally, the nonlinear behavior of the pyloric pattern generator described in Homarus also occurs in Jasus lalandii, in which the existence of a CPO has not yet been demonstrated.Abbreviations AB anterior burster neuron - ASW artificial seawater - COG commissural ganglion - CP commissural pyloric neuron - CPG central pattern generator - CPO commissural pyloric oscillator - IC inferior cardiac neuron - ivn inferior ventricular nerve - LP lateral pyloric neuron - OG esophageal ganglion - PD pyloric dilator neuron - PDn pyloric dilator nerve - PS pyloric suppressor neuron - son superior esophageal nerve - PY pylonic neuron - STG stomatogastric ganglion - stn stomatogastric nerve - vlvn ventral branch of the lateral ventricular nerve Maître de conférence à l'U.E.R. de Médecine et de Pharmacie, 2 rue Dr Marcland, 87025 Limoges Cedex, France.     

Backbone-methylated analogues of the principle receptor binding region of human parathyroid hormone. Evidence for binding to both the N-terminal extracellular domain and extracellular loop region

We have used backbone N-methylations of parathyroid hormone (PTH) to study the role of these NH groups in the C-terminal amphiphilic alpha-helix of PTH (1-31) in binding to and activating the PTH receptor (P1R). The circular dichroism (CD) spectra indicated the structure of the C-terminal alpha-helix was locally disrupted around the methylation site. The CD spectra differences were explained by assuming a helix disruption for four residues on each side of the site of methylation and taking into account the known dependence of CD on the length of an alpha-helix. Binding and adenylyl cyclase-stimulating data showed that outside of the alpha-helix, methylation of residues Asp30 and Val31 had little effect on structure or activities. Within the alpha-helix, disruption of the structure was associated with increased loss of activity, but for specific residues Val21, Leu24, Arg25, and Leu28 there was a dramatic loss of activities, thus suggesting a more direct role of these NH groups in correct P1R binding and activation. Activity analyses with P1R-delNT, a mutant with its long N-terminal region deleted, gave a different pattern of effects and implicated Ser17, Trp23, and Lys26 as important for its PTH activation. These two groups of residues are located on opposite sides of the helix. These results are compatible with the C-terminal helix binding to both the N-terminal segment and also to the looped-out extracellular region. These data thus provide direct evidence for important roles of the C-terminal domain of PTH in determining high affinity binding and activation of the P1R receptor.