Differentiated chemical reactivity of nanoparticles toward DTT

RATIONALE: Induction of oxidative stress and impairment of the antioxidant defense are considered important biological responses following nanoparticle (NP) exposure. The acellular in vitro dithiothreitol (DTT) assay is proposed to measure the oxidative potential of NP. In addition, DTT can be considered as a model compound of sulfur containing antioxidants. The objective of this work is to evaluate the surface reactivity in solution of a NP panel toward DTT. METHOD: The NP panel was composed of four carbonaceous particles, six types of metal oxides and silver with primary size ranged from 7 to 300 nm. Suspensions were prepared in surfactant solution with 30 min sonication. DTT was used as reductant to evaluate the oxidative properties of the different NP. The determination of the NP ability to catalyze electron transfer from DTT to oxygen was carried out as described in Sauvain et al., Nanotoxicology, 2008, 2:3, 121−129. RESULTS: All the carbonaceous NP catalyzed the oxidation of DTT by oxygen following the mass based order: carbon black > diesel exhaust particle > nanotubes > fullerene. A contrasting reactivity was observed for the metallic NP. Except for nickel oxide and metallic silver, which reacted similarly to the carbonaceous NP, all other metal oxides hindered the oxidation of DTT by oxygen, with ZnO being the most effective one. CONCLUSIONS : DTT was stabilized against oxidation in the presence of metal oxide NP in the solution. This suggests that different chemical interactions take place compared with carbonaceous NP. To explain these differences, we hypothesize that DTT could form complexes with the metal oxide surface (or dissolved metal ions), rendering it less susceptible to oxidation. By analogy, such a process could be thought to apply in biological systems with sulfur−containing antioxidants, reducing their buffer capacity. Such NP could thus contribute to oxidative stress by an alternative mechanism.

Le paysan instruit sur le serment civique ou Instruction familière, dans laquelle on fait connoître comment & pourquoi la nouvelle Constitution détruit la religion ([Reprod.])

Collection : Les archives de la Révolution française ; 8.1306

Instruction pressante sur la Constitution civile du clergé ([Reprod.])

Collection : Les archives de la Révolution française ; 8.52

Examen de l'instruction de l'Assemblée nationale sur la Constitution du clergé ([Reprod.])

Collection : Les archives de la Révolution française ; 8.584

Commentaire sur l'instruction de l'Assemblée nationale sur l'organisation civile du clergé ([Reprod.])

Collection : Les archives de la Révolution française ; 8.585

L'instruction de l'Assemblée nationale, sur l'organisation civile du clergé, arguée de mauvaise foi, d'inconséquence et d'injustice ([Reprod.])

Collection : Les archives de la Révolution française ; 8.64

Seconde instruction pressante sur la Constitution civile du clergé ([Reprod.])

Collection : Les archives de la Révolution française ; 8.53

Apologie du clergé de France ou commentaire raisonné, sur l'instruction pastorale de l'assemblée nationale, concernant l'organisation civile du clergé ([Reprod.]) / [par M. l'abbé Blandin]

Collection : Les archives de la Révolution française ; 8.534

Epître à M. Lamourette, se disant évêque de Rhône-et-Loire, métropolitain du sud-est sur son instruction pastorale et doctrinale du 16 juillet 1791 ([Reprod.]) / [par M. A. Guillon]

Collection : Les archives de la Révolution française ; 8.1417

Neuropeptide Y expression and regulation in a differentiated rat insulin-secreting cell line.

Neuropeptide-Y (NPY) is a 36-amino acid peptide known to inhibit glucose-stimulated insulin secretion in various animal models in vitro and in vivo. NPY is thought to be one of the mediators of sympathetic action in the pancreas through nerve endings surrounding the islets, and it has recently been shown to be synthesized within the islets of Langerhans. To elucidate the potential role of NPY in the endocrine pancreas, we studied the expression and regulation of NPY secretion in a rat insulinoma cell line (INS-1). NPY mRNA and peptide are highly expressed and secreted by INS-1 cells. NPY levels were determined by a sensitive and specific two-site amplified enzyme-linked immunosorbent assay. Incubation of INS-1 cells with various glucose concentrations did not modify NPY secretion; however, stimulation of adenylate cyclase by forskolin induced a dose- and time-dependent increase in NPY release in the medium. The glucagon-like peptide-I-(7-36) amide (GLP-1), a known gluco-incretin in humans, induced at low concentration (10(-9) M) a similar expression of NPY mRNA and peptide secretion in INS-1 cells. On the other hand, the inhibition of cAMP accumulation by the alpha 2-adrenergic agonist clonidine decreased NPY secretion. In conclusion, 1) high levels of gene expression and secretion of NPY are found in a rat insulinoma cell line (INS-1). 2) Accumulation of cAMP induced by forskolin or a gluco-incretin (GLP-1) induces a further increase in NPY gene expression and release. 3) NPY secretion is not modulated by low or high glucose concentrations in the medium. 4) Induction of NPY, a known inhibitor of insulin secretion, may represent a novel counterregulatory mechanism of insulin secretion, limiting the stimulatory effect of GLP-1 on insulin secretion.

Mémoire pour servir d'instruction aux commis à la recette du droit de centième denier de tous les offices de judicature, police, finances, et autres offices royaux, pour l'année 1773, en exécution de l'édit du mois de février 1771, et de l'arrêt du Conseil du 6 juillet 1772

[Acte. 1772]