ABSTRACT
PURPOSE: To report 3 cases of stromal rejection after deep anterior lamellar keratoplasty (DALK) assisted by a femtosecond laser. METHODS: Three keratoconus eyes of 2 men (22 and 30 years old) and 1 woman (24 years old) who had DALK with a 60-kHz femtosecond laser developed intrastromal graft rejection with superficial and deep neovascularization after 6, 15, and 12 months, respectively. All patients underwent confocal microscopy and were treated with topical steroid therapy. RESULTS: In vivo confocal microscopy revealed cellular inflammatory infiltrates in the subepithelial and middle stroma of the donor lamella without involvement of the endothelium. Graft rejection was rapidly reversed with topical steroid therapy, and a clear cornea was restored in all cases. CONCLUSIONS: Graft rejection remains a significant complication of lamellar surgery but is associated with good tissue restoration and complete visual recovery.
Subject(s)
Corneal Transplantation/adverse effects , Graft Rejection/etiology , Keratoconus/surgery , Lasers, Excimer/therapeutic use , Adult , Corneal Stroma/pathology , Dexamethasone/therapeutic use , Female , Glucocorticoids/therapeutic use , Graft Rejection/drug therapy , Humans , Male , Microscopy, Confocal , Ophthalmic Solutions/therapeutic use , Suture Techniques , Visual Acuity/physiology , Young AdultABSTRACT
Preliminary studies of the elementary steps involved in the reaction of a chiral methyl carbonyl bioxazoline Pd(II) complex with aromatic olefins and CO have allowed development of a new enantioselective catalytic carbonylation process, leading to γ-ketoester derivatives with high yield and good enantiomeric excess. The intermediate palladacycle complexes have been isolated and characterized by NMR spectroscopy and X-ray diffraction. Factors that govern the stereoselectivity of the olefin carbonylation process are discussed.
Subject(s)
Coordination Complexes/chemistry , Palladium/chemistry , Styrenes/chemistry , Alkenes/chemistry , Carbon Monoxide/chemistry , Catalysis , Coordination Complexes/chemical synthesis , Crystallography, X-Ray , Molecular Conformation , StereoisomerismABSTRACT
Superparamagnetic iron oxide nanoparticles (SPIOs) have been produced and used as a potent and versatile contrast media for magnetic resonance imaging (MRI). Despite a number of efforts to improve their surface chemistry and biocompatibility, the SPIOs half life in blood circulation is very short and they are rapidly taken up by the reticuloendothelial system (RES). In this paper we describe a new method that permits to avoid the rapid clearance of SPIOs. Nanoparticles are made biocompatible by encapsulation into autologous red blood cells. These biomimetic constructs preserve the main properties of the cells that escape RES clearance as well as the properties of the nanoparticles that perform even better than in blood suspension with reduced T2*. These SPIO-loaded RBCs are promising intravascular imaging contrast agents and could also be addressed to selected body compartments by an external magnetic field.
Subject(s)
Magnetics , Molecular Mimicry , Nanoparticles , Animals , Contrast Media , Erythrocytes/metabolism , Female , Humans , Magnetic Resonance Imaging , Mice , Mice, Inbred BALB C , PharmacokineticsABSTRACT
Structural analysis of the first steps of isotactic CO/p-methylstyrene copolymerisation, catalysed by aryl-alpha-diimine Pd(II) complexes, highlights the influence of steric effects on the stereoselectivity of olefin insertion.
ABSTRACT
The coordination chemistry of the chiral bioxazoline ligand (4S,4'S)-2,2'-bis(4-isopropyl-4,5-dihydrooxazole) to Pd(II) provides evidence that the ligand bonding can occur either through chelation of one Pd(II) ion leading to a mononuclear species with the expected cis geometry, or by double bridging of two Pd(II) ions giving a dinuclear complex with trans geometry. The species in solution are identified by 1H NMR spectroscopy. Both the mononuclear and the dinuclear complexes promote the CO/styrene copolymerization, yielding the corresponding polyketone with a fully or a predominantly isotactic microstructure, depending on the reaction medium. The nature of the anion present in the palladium precatalysts affects the polyketone stereochemistry. MALDI-TOF analysis of the copolymers synthesized reveals the presence of p-hydroxyphenolic end-groups, thus confirming and explaining the role of 1,4-hydroquinone as a molecular weight regulator.
ABSTRACT
Insertion of 1,2-disubstituted alkynes into [Pd(CH3)(CO)(BIOX)]+[B{3,5-(CF3)2C6H3}4]- (1), where BIOX=(4S,4'S)-(-)-4,4',5,5'-tetrahydro-4,4'-bis(1-methylethyl)-2,2'-bioxazole, leads to the formation of five-membered palladacycles, which, by reaction with carbon monoxide, produce a mixture of two diastereomeric forms of a palladium complex containing an eta3-allylic gamma-lactone ligand. On leaving the mixture in solution, one isomer was converted into the other, reaching a diastereomeric excess of up to 94 %. The steric and electronic factors responsible for the epimerization process were investigated by theoretical methods. Cleavage of the eta3-allyl--palladium bond by nucleophiles allowed highly substituted chiral butenolides to be synthesized in good enantiomeric excess.
