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Biomedical subjects

J M Breitfeller

Publications and source records attributed to J M Breitfeller.

7 recordsLinked to original sources
PubMed1982

Lectin-mediated attachment of liposomes to cornea: influence on transcorneal drug flux.

A method to enhance retention of drug-bearing liposomes at the corneal surface under conditions of tear flow was investigated. Mixed brain gangliosides were incorporated into the membranes of phosphatidyl choline liposomes to provide receptor sites for wheat germ agglutinin, a plant lectin that binds strongly to both human and rabbit corneal epithelium. Ganglioside-containing liposomes showed a 2.5-fold increase in their binding to rabbit cornea in vitro when corneas were pretreated with wheat germ agglutinin (500 micrograms/ml), suggesting that the lectin mediates specific binding of these liposomes to the corneal surface. In addition, under conditions of continuous tear flow (1 ml/hr), ganglioside-containing liposomes with entrapped carbachol significantly enhanced carbachol flux across isolated rabbit corneas pretreated with wheat germ agglutinin 90 min after drug delivery. The data support the potential use of liposomes as a vehicle for topical drug flux enhancement.

Animals↗
PubMed1980

Limbal pneumatonometry.

A series of comparisons in normal and glaucomatous eyes, all with normal corneas, was made between Goldmann applanation tonometry and Langham pneumatonometry, central and limbal, and with the patient in sitting and supine positions. All measurements were made at one visit with a standardized sequence. All mean pneumatonograph measurements were significantly higher than the corresponding applanation value. However, no significant difference was found between limbal and apical pneumatonograph values in the supine subject. Conversion values relating pneumatonograph measurements and applanation values have been derived and designated as Clinical Correlation Estimators. This allows prediction of Goldmann applanation values by extrapolation of limbal pneumatonograph measurements at a 95% confidence level. The method has potential use in the determination of intraocular pressure in the presence of corneal disease.

Adolescent↗
PubMed1979

Transcorneal flux of topical pilocarpine to the human aqueous.

Aqueous fluid was withdrawn from eyes of patients undergoing cataract extraction at various intervals after administration of two drops of 2% pilocarpine HCl in a standard manner. Determination of aqueous pilocarpine concentration was made both by spectroscopy of a ferric hydroxylamine complex and by gas-liquid chromatography. Results of both methods were consistent in indicating that concentration does not rise at any time following such topical instillation beyond 5 microgram/ml, with an average of 1.67 microgram/ml, representing a flux efficiency of 0.03%. These findings correlate well with previous investigations of transcorneal flux of pilocarpine for the rabbit in a transport chamber system, in which comparable low flux efficiency was found after simulated drop administration. This serves in some measure to validate an extrapolation of other findings in chamber experiments to the living human eye.

Administration, Topical↗
PubMed1976

Quantitation of pilocarpine delivery across isolated rabbit cornea by noncross-linked high viscosity polymer gel.

The effect on pilocarpine flux across rabbit cornea in vitro by a noncross-linked polymeric gel vehicle was measured. A closed system transport chamber was used. Its design featured continuous flow of a tear analog but excluded variables of the internal eye. Results were compared to previously determined data in the same chamber system for cross-linked hydrogel buttons and for free pilocarpine fluid. Gel-mediated flux was equal to that with lens buttons to 90 minutes in the case of a 30 per cent gel (viscosity approximately 70,000 centipoises). Elution by the tear analog system limited flux duration of gels relative to lenses. Greater viscosity of 30 per cent gel relative to 25 per cent gel (approximately 15,000 centipoises) was associated with prolonged transcorneal drug flux. The congruence of flux slopes for 30 per cent gel and lens button vehicles despite the difference in available dose suggests saturable mediation of pilocarpine transport across the cornea, but a greater "flux efficiency" through 90 minutes for 30 per cent gel.

Animals↗
PubMed1975

Quantitation of pilocarpine flux enhancement across isolated rabbit cornea by hydrogel polymer lenses.

The comparative effect on pilocarpine flux across rabbit cornea induced by two hydrogel polymer lenses containing equal doses was quantitated in a transport chamber. This closed system featured continuous flow of a tear analog but excluded variables of the internal eye influencing concentration. Flux induced by both lenses increased linearly with time. At 240 minutes total flux was a whole order greater than that induced by the same pilocarpine dose in free fluid. Analysis of pilocarpine in tear analog effluent showed the flux to be independent of the available dose retained in the hydrogel polymer lens, suggesting that corneal transport of pilocarpine to the aqueous may involve mediation by a carrier system.

Animals↗