Biomedical subjects
Publications and source records attributed to K Green.
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Numerous modifications have been made in MK solution, primarily concerned with alterations in both bicarbonate concentration and PCO2. Variations of the solutions from high bicarbonate to low bicarbonate and either high or low PCO2 were made which resulted in a decreased net bicarbonate flux across the endothelium after a 3-day storage period. Even with drastic changes in the storage solution there was a relatively small change in the net bicarbonate flux. Higher passive fluxes were found at a pH above 8, and a higher net flux with a bicarbonate concentration of 17.5 nM or higher. Variation in PCO2 made little difference to the net endothelial fluxes; when a high PCO2 was used, there was a concurrent elevation of PO2 in the storage solution, but no beneficial effect was found on the endothelial transport system. It was apparent that a good storage solution contained a buffer (bicarbonate was better than phosphate) and 5% dextran and was at a neutral pH (between 7 and 8).
We describe the preparation of [2,4,16,16-2H4]estradiol-17 beta. The method for quantitative determination of subpicomole amounts of estradiol-17 beta (trimethylsilyl ether derivatives) by gas-liquid chromatography-mass spectrometry with multiple ion detector and with [2H4]estradiol-17 beta as the carrier is presented and characterized. Values for serum samples, as measured by radioimmunoassay and by mass fragmentography, agreed well.
In order to investigate the efficacy of iontophoresis for increasing the penetration of vidarabine monophosphate into the eye, tritium-labeled vidarabine monophosphate was applied to rabbit eyes by topical and iontophoretic application, and the penetration of the compound into the eye, and its subsequent metabolism, were studied. At 20 min after treatment, the ratios of radioactivity for cathodal iontophoresis compared to topical application alone were cornea 8.6, aqueous humor 4.8, and iris 2.4; for 60 min the ratios were cornea 12.2 aqueous humor 17.5 and iris 2.5. In addition, the acid-soluble components were extracted from the cornea and aqueous humor. Vidarabine monophosphate, vidarabine, hypoxanthine arabinoside, adenosine, hypoxanthine, and adenine from the acid-soluble fraction were separated by thin-layer chromatography. The amount of vidarabine monophosphate and vidarabine in the cornea and aqueous humor from the iontophoretically treated group was six to 15 times higher than from the group that received topical application of the drug. It was concluded that cathodal iontophoresis resulted in significantly increased penetration of the antiviral drug vidarabine monophosphate into the anterior chamber of the eye. The effects of iontophoresis of vidarabine monophosphate on corneal epithelium, as observed by scanning electron micrographs, were equal to or less than those seen with the topical application of widely used preservatives in ophthalmic preparations.
Xenon arc photocoagulation of the fundus of pigmented rabbits resulted in no corneal endothelial cell damage when the experiment was designed to minimize corneal temperature rise by frequent topical instillations of ophthalmic irrigating solution.
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The endothelial surface of isolated rabbit corneas were perfused for three hours with varying concentrations of benzalkonium chloride and cetylpyridinium chloride. The threshold for physiological and ultrastructural alteration of corneal endothelium is approximately 0.0001% for benzalkonium chloride and 0.01 mM for cetylpyridinium chloride. The effects of the surfactants can be induced with as little as a 15-minute exposure without subsequent recovery. Use of ophthalmic medications or irrigating solutions containing these agents inside the eye is potentially hazardous to the corneal endothelium. Topical administration of 0.133% benzalkonium chloride to the anterior surface of deepithelialized in vivo corneas (five doses, seven minutes apart) caused no alterations of corneal endothelial cell function or ultrastructure.
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Corneal endothelial cell function and ultrastructure were studied in rabbit corneas stored in M-K medium with different antibiotics. At concentrations about ten times greater than their minimum inhibitory concentrations, tobramycin, gentamicin, polymixin B, penicillin and streptomycin mixture, cephaloridine, and cephalothin did not damage corneal endothelia. Corneas stored in M-K medium with bacitracin did not have temperature reversals as did other corneas after storage. This is probably not significant since they maintained almost constant thickness and the endothelial layer remained intact.
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The endothelial surface of rabbit corneas was perfused with vidarabine monophosphate (with and without adenosine deaminase inhibitor), vidarabine (with and without adenosine deaminase inhibitor), and ara-Hx. In concentrations 10 times to 1,500 times higher than those that have been obtained in the aqueous humor following topical, subconjunctival, or systemic administration, none of the compounds had any effect on corneal endothelial cell function or ultrastructure for the duration of the experimental model.