Correlation of SD-OCT findings and visual function in patients with retinitis pigmentosa.

Purpose: To describe the morphological macular changes detected by spectral domain optical coherence tomography (SD-OCT) in eyes with retinitis pigmentosa (RP) and to analyze their correlation with the visual function.

Methods: Twenty-two patients (44 eyes) patients affected by RP were recruited. The following structures were evaluated on SD-OCT: outer plexiform layer (OPL), outer nuclear layer (ONL), external limiting membrane (ELM), photoreceptor inner/outer segment (IS/OS) junction, photoreceptor outer segment/retinal pigmented epithelium (OS/RPE) junction, inner limiting membrane thickening (ILMT), ganglion cell complex (GCC), and cystoid macular edema (CME).

Novel hydrogel system from scleroglucan: synthesis and characterization.

New hydrogels obtained by a crosslinking reaction between the polycarboxylated derivative of scleroglucan (sclerox) and 1, 6-hexanedibromide have been prepared and characterized. Different ratios between the alkane dihalide and sclerox yielded products with appreciably different properties. Water uptake by the hydrogel with a low degree of crosslinking was remarkably affected by ionic strength.

A novel co-crosslinked polysaccharide: studies for a controlled delivery matrix.

The formulation of a new controlled delivery system, based on a novel type of matrix obtained by the chemical reaction carried out in an aqueous medium on a mixed physical gel of gellan and scleroglucan, is described in this paper. The preparation yielded a new co-crosslinked polysaccharide (CCP) hydrogel, bearing carboxylic groups, that showed a sustained release behaviour that can be modulated by means of calcium ions. For the characterization of CCP, diffusion experiments through the swelled hydrogel were carried out in different environmental conditions and the release from tablets prepared with CCP and a model drug was evaluated.

Gellan in sustained release formulations: preparation of gel capsules and release studies.

The ability of gellan to form gels in the presence of calcium ions enabled us to prepare capsules by gelation of this polysaccharide around a core containing starch, calcium chloride and a model drug. Release from the dried capsules was studied in vitro by means of the rotating basket technique (USP) in different environmental conditions (distilled water, pH = 2.0, pH = 6.

Effect of surfactants on diffusion of calcium in mucin: a possible mechanism affecting enamel remineralization.

By means of in vitro experiments, performed with a three compartment diffusion cell, we show how the presence of surfactants, often present in the formulation of dentifrices and mouthrinses, may affect the availability of calcium and its permeation rate through the proteic layer covering dental enamel (acquired pellicle). Mucin was the protein used to simulate the pellicle. Experiments were performed at different surfactant concentrations (i.

Scleroglucan sustained release oral preparations. Part II. Effects of additives.

Swelling and diffusion experiments, performed in vitro with tablets prepared with scleroglucan and several hydrophilic and hydrophobic additives, indicate that it is possible to modulate drug delivery from the matrix by appropriate choice of the nature and amount of the additive. The additives in the formulations may affect the mechanisms (zero order, diffusion, erosion) involved in the release of drugs from the dosage forms.

Scleroglucan sustained-release oral preparations. Part I. In vitro experiments.

Experiments performed in vitro with tablets and capsules indicate that the fungal polysaccharide scleroglucan is suitable for the formulation of sustained-release, oral dosage forms. Delivery of model drugs from the non-disintegrating matrix was studied in solutions buffered at different pH values. The effect on drug release of drug concentration, the physico-chemical properties of the drug, and the compression force used in the preparation of the matrix are reported, and the possible mechanisms of release are discussed.

Prevention of molecular self-association by sodium salicylate: effect on insulin and 6-carboxyfluorescein.

The effect of sodium salicylate on the concentration-dependent self-association of insulin and 6-carboxyfluorescein (CF), as expressed by metachromasy, fluorescence, and changes in aqueous solubility, was learned. By decreasing the CF concentration from 12 to 0.48 microgram.

A possible pH-controlled drug delivery system based on a derivative of the polysaccharide scleroglucan.

Four carboxylated derivatives of scleroglucan have been obtained by oxidation, to different extents, of the glucopyranose side chains of the natural polysaccharide. The diffusion of model molecules through aqueous solutions of these new products was measured at various pH values. The reversible pH induced sol-gel transition of some of the polyelectrolyte solutions tested effects a remarkable variation in the diffusion rate of the permeating species; in this sense the most interesting polysaccharide appears to be the product with 70% oxidized glucopyranose moieties.

Swelling and binding effects in a polymeric microfiber model for controlled drug release.

The diffusion of model molecules from water dispersions of ethylenevinyl-N,N-diethylglycinate copolymer microfibers has been studied in different conditions. The influence of pH on diffusion rate has been related to water association and swelling effects following structural transitions induced in the copolymer by the acidic medium, rather than to difference in binding of the diffusing species to the macromolecule.

A polymeric film responding in diffusion properties to environmental pH stimuli: a model for a self-regulating drug delivery system.

A new polymeric film, ethylene-vinyl-NN-diethylglycinate random copolymer, has been studied to evaluate possible applications of such a material to produce controlled release dosage forms. Protonation of the substituted amino groups took place to different extents according to environmental pH conditions. The polymeric film proved to be permeable only to uncharged species, the rate of diffusion of which increased with the increasing charge of the membrane.

Effect of a second solubilizate on the partition coefficient of drugs in micellar solution and their permeation rate across an artificial membrane.

The distribution of a solubilizate between micelles and the aqueous phase does not obey a simple partition law when a second solubilizate species is present. Alterations of the apparent partition coefficient cannot be explained in terms of a simple displacement mechanism, following the interaction of both solubilizates with the same site of the micelle. A non linear increase in solubilizate association to micelles following an increase in surfactant concentration is observed in the presence of a second solubilizate.

O- and N-alkylation with "Meerwein's reagent": the unusual behaviour of two lactams.

Usually tertiary oxonium salts are excellent O-alkylating agents of lactams; in some cases indiscriminate O- and N-alkylations have been described. In this paper the particular behaviour towards Meerwein's reagent of two isomers with a lactamic structure is pointed out: in one case the usual O-alkylation occurs, in the other N-alkylation is the only reaction that takes place.

Effect of surfactant monomers on chloramphenicol association to an albumin-lecithin complex: a model for modified drug absorption.

The binding of chloramphenicol to an albumin-lecithin complex in the presence or absence of premicellar concentrations of both ionic and non-ionic surfactants has been examined. Long chain, strong ionic detergents, such as sodium dodecyl sulphate or cetyltrimethylammonium bromide, severely perturb protein structure and eventually allow full separation of the complex into lecithin and albumin-detergent complexes. The dissociation process is reversible upon the removal of the detergent by exhaustive dialysis.