Effects of triamcinolone acetonide on vessels of the posterior segment of the eye

PURPOSE: This study investigates the effects of triamcinolone acetonide (TA) on retinal endothelial cells in vitro and explores the potential vascular toxic effect of TA injected into the vitreous cavity of rats in vivo. METHODS: Subconfluent endothelial cells were treated with either 0.1 mg/ml or 1 mg/ml TA in 1% ethanol. Control cells were either untreated or exposed to 1% ethanol. Cell viability was evaluated at 24 h, 72 h, and five days using the tetrazolium 3-(4,5-dimethylthiazol-2-yl)-2,5 phenyltetrazolium bromide test (MTT) and lactate dehydrogenase (LDH) assays. Cell proliferation was evaluated by 5-bromo-2-deoxyuridine (BrdU) test. Apoptosis was evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling assay (TUNEL assay), annexin-binding, and caspase 3 activation. Caspase-independent cell deaths were investigated by immunohistochemistry using antibodies against apoptosis inducing factor (AIF), cytochrome C, microtubule-associated protein (MAP)-light chain 3 (MAP-LC3), and Leukocyte Elastase Inhibitor/Leukocyte Elastase Inhibitor-derived DNase II (LEI/L-DNase II). In vivo, semithin and ultrathin structure analysis and vascular casts were performed to examine TA-induced changes of the choroidal vasculature. In addition, outer segments phagocytosis assay on primary retinal pigment epithelium (RPE) cells was performed to assess cyclooxygenase (COX-2) and vascular endothelial growth factor (VEGF) mRNAs upregulation with or without TA. RESULTS: The inhibitory effect of TA on cell proliferation could not explain the significant reduction in cell viability. Indeed, TA induced a time-dependent reduction of bovine retinal endothelial cells viability. Annexin-binding positive cells were observed. Cytochrome C was not released from mitochondria. L-DNase II was found translocated to the nucleus, meaning that LEI was changed into L-DNase II. AIF was found nuclearized in some cells. LC3 labeling showed the absence of autophagic vesicles. No autophagy or caspase dependent apoptosis was identified. At 1 mg/ml TA induced necrosis while exposure to lower concentrations for 3 to 5 days induced caspase independent apoptosis involving AIF and LEI/L-DNase II. In vivo, semithin and ultrathin structure analysis and vascular casts revealed that TA mostly affected the choroidal vasculature with a reduction of choroidal thickness and increased the avascular areas of the choriocapillaries. Experiments performed on primary RPE cells showed that TA downregulates the basal expression of COX-2 and VEGF and inhibits the outer segments (OS)-dependent COX-2 induction but not the OS-dependent VEGF induction. CONCLUSIONS: This study demonstrates for the first time that glucocorticoids exert direct toxic effect on endothelial cells through caspase-independent cell death mechanisms. The choroidal changes observed after TA intravitreous injection may have important implications regarding the safety profile of TA use in human eyes

CD36 Deficiency Leads to Choroidal Involution via COX2 Down-Regulation in Rodents

Florian Sennelaub and colleagues show that CD36 deficiency leads to choroidal involution, a key feature of "dry" age-related macular degeneration, via COX-2 down-regulation in the retinal pigment epithelium

Dichroïsme et biréfringence électriques des solutions d’acides nucléiques et de nucléoprotéines

La structure, en solution, de l’acide désoxyribonucléique (DNA), de la désoxyribonucléohistone (DNH), des complexes DNA-Proflavine et DNH-Proflavine, et de la DNH iodée a été étudiée par mesure de la biréfringence et du dichroïsme électriques. On a examiné l’influence du contenu histonique sur l’anisotropie optique de la nucléohistone. Les résultats obtenus sur les complexes avec la proflavine sont discutés en fonction des divers modèles de fixation du colorant

Prix Nobel de Chimie 2008: Suivre les protéines à la trace grâce à la GFP («Green Fluorescent Protein»)

La GFP permet de voir les protéines directement dans les organismes vivants, de les localiser grâce à la fluorescence qu’elle émet. Par manipulation génétique, on peut accrocher la GFP à diverses protéines que l’on peut ainsi suivre à la trace dans les cellules en fonctionnement. Comme une large variété de mutants de la GFP émettant des fluorescences de couleurs différentes sont disponibles, on peut même localiser plusieurs protéines simultanément. Quel merveilleux outil pour l’imagerie en microscopie optique

Chapter 7 Codon Recognition: Evaluation of the Effects of Modified Bases in the Anticodon Loop of Trna Using the Temperature-Jump Relaxation Method

This chapter describes the temperature-jump (T-jump) technique and its uses in the study of two tRNA molecules having complementary or quasi-complementary anticodons. This approach offers a sensitive means for accurately detecting event in tiny differences in the interaction energies between the two tRNAs. The chapter emphasizes on the effect of various (hyper)-modifications found at positions 34 and 37 of the anticodon on the thermodynamic and kinetic parameters, as well as on the spectral properties of the duplexes. The results enlighten the importance of these bases in the stabilization of the tRNA association. As the anticodon–anticodon interactions can mimic the codon-anticodon association process on the ribosome, such studies allow insights into some of the structural and dynamic parameters of tRNA, intrinsic to the anticodon loop and stem that are essential for the efficiency and accuracy of the whole translation process. © 1990, Elsevier Inc. All rights reserved.SCOPUS: ar.kSCOPUS: ar.kinfo:eu-repo/semantics/publishe

Triplex and quadruplex DNA structures studied by electrospray mass spectrometry

DNA triplex and quadruplex structures have been successfully detected by electrospray ionization mass spectrometry (ESI-MS). Circular dichroism and UV-melting experiments show that these structures are stable in 150 mM ammonium acetate at pH 7 for the quadruplexes and pH 5.5 for the triplexes. The studied quadruplexes were the tetramer [d(TGGGGT)](4), the dimer [d(GGGGTTTTGGGG)](2), and the intramolecular folded strand dGGG(TTAGGG)(3), which is an analog of the human telomeric sequence. The absence of sodium contamination allowed demonstration of the specific inclusion of n-1 ammonium cations in the quadruplex structures, where n is the number of consecutive G-tetrads. We also detected the complexes between the quadruplexes and the quadruplex-specific drug mesoporphyrin IX. MS/MS spectra of [d(TGGGGT)](4) and the complex with the drug are also reported. As the drug does not displace the ammonium cations, one can conclude that the drug binds at the exterior of the tetrads, and not between them. For the triplex structure the ESI-MS spectra show the detection of the specific triplex, at m/z values typically higher than those typically observed for duplex species. Upon MS/MS the antigene strand, which is bound into the major groove of the duplex, separates from the triplex. This is the same dissociation pathway as in solution. To our knowledge this is the first report of a triplex DNA structure by electrospray mass spectrometry

Configuration du RNA de transfert et mécanisme d'interaction de la proflavine

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