Posterior Ocular Tissues Research Articles

Ocular penetration of topically applied norfloxacin 0.3% in the rabbits and in humans.

The kinetics of topically applied norfloxacin 0.3 percent were studied in rabbit and man. All measurements were performed by high-pressure liquid chromatography. Norfloxacin concentrations were investigated five to 120 minutes in rabbit ocular tissues after instillation of a single drop. In normal eyes, after 30 minutes, mean +/- SEM levels were 14.3 +/- 3.7 micrograms/g in cornea, 3.3 +/- 0.7 micrograms/g in conjunctiva, 0.2 +/- 0.1 microgram/g in aqueous humor. After removal of the corneal epithelium concentrations were as follows: 84.2 +/- 15.8 micrograms/g, 7.3 +/- 2.3 micrograms/g, 8.6 +/- 1.9 micrograms/g respectively. Penetration in posterior ocular tissues were rather poor. In human eyes, the intracorneal concentrations were assessed in patients being operated on corneal grafts. After instillation of 5 drops, the concentration in cornea was 15.5 +/- 2.1 micrograms/g. These data show that therapeutic levels of norfloxacin can be achieved in anterior ocular tissues, which may be of help in superficial infections of the eye.

Depth-resolved chromophore analysis of bovine retina and pigment epithelium by photoacoustic spectroscopy

The cattle retina and retinal pigment epithelium are examined by means of photoacoustic spectroscopy under conditions where structural integrity is maintained. Depth-related information is obtained about the chromophore distribution within the samples by analysis of the frequency dependence of the spectra giving a 3-D image of the posterior ocular tissues.

Glutamine fructose-6-phosphate aminotransferase and glycoprotein synthesis in the developing chick eye

Glutamine fructose-6-phosphate aminotransferase is an essential enzyme in the synthesis of glycoproteins and other complex carbohydrates. The specific activity of this enzyme was measured in posterior ocular tissues of the chick embryo from day 6 of development until hatching. The enzyme is present at high concentrations in the early embryo, then decreases 15-fold by day 9 in both retina and retinal pigment epithelium (PE). Thus, aminotransferase activity is highest during the period when retinal cells are migrating and beginning to differentiate; these maturational events may require cell-surface glycoproteins. On day 17-18 of chick embryo development, the neural retina suddenly adheres firmly and irreversibly to the underlying PE. Aminotransferase activity and glucosamine incorporation into retinal macromolecules were examined near this critical time, as were the effects of glycoprotein-synthesis inhibitors upon retinal adhesion. No evidence was found for involvement of complex carbohydrates (on cell surfaces or in the interphotoreceptor matrix, IPM) in formation of retinal adhesion in the chick. Histological studies show an absence of glycosaminoglycans in the IPM of embryonic chicks (at all stages) and of adult chickens, although these compounds are present in mammalian matrix.